1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * kernel/lockdep.c
4 *
5 * Runtime locking correctness validator
6 *
7 * Started by Ingo Molnar:
8 *
9 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
11 *
12 * this code maps all the lock dependencies as they occur in a live kernel
13 * and will warn about the following classes of locking bugs:
14 *
15 * - lock inversion scenarios
16 * - circular lock dependencies
17 * - hardirq/softirq safe/unsafe locking bugs
18 *
19 * Bugs are reported even if the current locking scenario does not cause
20 * any deadlock at this point.
21 *
22 * I.e. if anytime in the past two locks were taken in a different order,
23 * even if it happened for another task, even if those were different
24 * locks (but of the same class as this lock), this code will detect it.
25 *
26 * Thanks to Arjan van de Ven for coming up with the initial idea of
27 * mapping lock dependencies runtime.
28 */
29 #define DISABLE_BRANCH_PROFILING
30 #include <linux/mutex.h>
31 #include <linux/sched.h>
32 #include <linux/sched/clock.h>
33 #include <linux/sched/task.h>
34 #include <linux/sched/mm.h>
35 #include <linux/delay.h>
36 #include <linux/module.h>
37 #include <linux/proc_fs.h>
38 #include <linux/seq_file.h>
39 #include <linux/spinlock.h>
40 #include <linux/kallsyms.h>
41 #include <linux/interrupt.h>
42 #include <linux/stacktrace.h>
43 #include <linux/debug_locks.h>
44 #include <linux/irqflags.h>
45 #include <linux/utsname.h>
46 #include <linux/hash.h>
47 #include <linux/ftrace.h>
48 #include <linux/stringify.h>
49 #include <linux/bitmap.h>
50 #include <linux/bitops.h>
51 #include <linux/gfp.h>
52 #include <linux/random.h>
53 #include <linux/jhash.h>
54 #include <linux/nmi.h>
55 #include <linux/rcupdate.h>
56 #include <linux/kprobes.h>
57 #include <linux/lockdep.h>
58 #include <linux/context_tracking.h>
59 #include <linux/console.h>
60
61 #include <asm/sections.h>
62
63 #include "lockdep_internals.h"
64
65 #include <trace/events/lock.h>
66
67 #ifdef CONFIG_PROVE_LOCKING
68 static int prove_locking = 1;
69 module_param(prove_locking, int, 0644);
70 #else
71 #define prove_locking 0
72 #endif
73
74 #ifdef CONFIG_LOCK_STAT
75 static int lock_stat = 1;
76 module_param(lock_stat, int, 0644);
77 #else
78 #define lock_stat 0
79 #endif
80
81 #ifdef CONFIG_SYSCTL
82 static struct ctl_table kern_lockdep_table[] = {
83 #ifdef CONFIG_PROVE_LOCKING
84 {
85 .procname = "prove_locking",
86 .data = &prove_locking,
87 .maxlen = sizeof(int),
88 .mode = 0644,
89 .proc_handler = proc_dointvec,
90 },
91 #endif /* CONFIG_PROVE_LOCKING */
92 #ifdef CONFIG_LOCK_STAT
93 {
94 .procname = "lock_stat",
95 .data = &lock_stat,
96 .maxlen = sizeof(int),
97 .mode = 0644,
98 .proc_handler = proc_dointvec,
99 },
100 #endif /* CONFIG_LOCK_STAT */
101 };
102
kernel_lockdep_sysctls_init(void)103 static __init int kernel_lockdep_sysctls_init(void)
104 {
105 register_sysctl_init("kernel", kern_lockdep_table);
106 return 0;
107 }
108 late_initcall(kernel_lockdep_sysctls_init);
109 #endif /* CONFIG_SYSCTL */
110
111 DEFINE_PER_CPU(unsigned int, lockdep_recursion);
112 EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
113
lockdep_enabled(void)114 static __always_inline bool lockdep_enabled(void)
115 {
116 if (!debug_locks)
117 return false;
118
119 if (this_cpu_read(lockdep_recursion))
120 return false;
121
122 if (current->lockdep_recursion)
123 return false;
124
125 return true;
126 }
127
128 /*
129 * lockdep_lock: protects the lockdep graph, the hashes and the
130 * class/list/hash allocators.
131 *
132 * This is one of the rare exceptions where it's justified
133 * to use a raw spinlock - we really dont want the spinlock
134 * code to recurse back into the lockdep code...
135 */
136 static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
137 static struct task_struct *__owner;
138
lockdep_lock(void)139 static inline void lockdep_lock(void)
140 {
141 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
142
143 __this_cpu_inc(lockdep_recursion);
144 arch_spin_lock(&__lock);
145 __owner = current;
146 }
147
lockdep_unlock(void)148 static inline void lockdep_unlock(void)
149 {
150 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
151
152 if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
153 return;
154
155 __owner = NULL;
156 arch_spin_unlock(&__lock);
157 __this_cpu_dec(lockdep_recursion);
158 }
159
lockdep_assert_locked(void)160 static inline bool lockdep_assert_locked(void)
161 {
162 return DEBUG_LOCKS_WARN_ON(__owner != current);
163 }
164
165 static struct task_struct *lockdep_selftest_task_struct;
166
167
graph_lock(void)168 static int graph_lock(void)
169 {
170 lockdep_lock();
171 /*
172 * Make sure that if another CPU detected a bug while
173 * walking the graph we dont change it (while the other
174 * CPU is busy printing out stuff with the graph lock
175 * dropped already)
176 */
177 if (!debug_locks) {
178 lockdep_unlock();
179 return 0;
180 }
181 return 1;
182 }
183
graph_unlock(void)184 static inline void graph_unlock(void)
185 {
186 lockdep_unlock();
187 }
188
189 /*
190 * Turn lock debugging off and return with 0 if it was off already,
191 * and also release the graph lock:
192 */
debug_locks_off_graph_unlock(void)193 static inline int debug_locks_off_graph_unlock(void)
194 {
195 int ret = debug_locks_off();
196
197 lockdep_unlock();
198
199 return ret;
200 }
201
202 unsigned long nr_list_entries;
203 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
204 static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
205
206 /*
207 * All data structures here are protected by the global debug_lock.
208 *
209 * nr_lock_classes is the number of elements of lock_classes[] that is
210 * in use.
211 */
212 #define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
213 #define KEYHASH_SIZE (1UL << KEYHASH_BITS)
214 static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
215 unsigned long nr_lock_classes;
216 unsigned long nr_zapped_classes;
217 unsigned long max_lock_class_idx;
218 struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
219 DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
220
hlock_class(struct held_lock * hlock)221 static inline struct lock_class *hlock_class(struct held_lock *hlock)
222 {
223 unsigned int class_idx = hlock->class_idx;
224
225 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
226 barrier();
227
228 if (!test_bit(class_idx, lock_classes_in_use)) {
229 /*
230 * Someone passed in garbage, we give up.
231 */
232 DEBUG_LOCKS_WARN_ON(1);
233 return NULL;
234 }
235
236 /*
237 * At this point, if the passed hlock->class_idx is still garbage,
238 * we just have to live with it
239 */
240 return lock_classes + class_idx;
241 }
242
243 #ifdef CONFIG_LOCK_STAT
244 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
245
lockstat_clock(void)246 static inline u64 lockstat_clock(void)
247 {
248 return local_clock();
249 }
250
lock_point(unsigned long points[],unsigned long ip)251 static int lock_point(unsigned long points[], unsigned long ip)
252 {
253 int i;
254
255 for (i = 0; i < LOCKSTAT_POINTS; i++) {
256 if (points[i] == 0) {
257 points[i] = ip;
258 break;
259 }
260 if (points[i] == ip)
261 break;
262 }
263
264 return i;
265 }
266
lock_time_inc(struct lock_time * lt,u64 time)267 static void lock_time_inc(struct lock_time *lt, u64 time)
268 {
269 if (time > lt->max)
270 lt->max = time;
271
272 if (time < lt->min || !lt->nr)
273 lt->min = time;
274
275 lt->total += time;
276 lt->nr++;
277 }
278
lock_time_add(struct lock_time * src,struct lock_time * dst)279 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
280 {
281 if (!src->nr)
282 return;
283
284 if (src->max > dst->max)
285 dst->max = src->max;
286
287 if (src->min < dst->min || !dst->nr)
288 dst->min = src->min;
289
290 dst->total += src->total;
291 dst->nr += src->nr;
292 }
293
lock_stats(struct lock_class * class)294 struct lock_class_stats lock_stats(struct lock_class *class)
295 {
296 struct lock_class_stats stats;
297 int cpu, i;
298
299 memset(&stats, 0, sizeof(struct lock_class_stats));
300 for_each_possible_cpu(cpu) {
301 struct lock_class_stats *pcs =
302 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
303
304 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
305 stats.contention_point[i] += pcs->contention_point[i];
306
307 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
308 stats.contending_point[i] += pcs->contending_point[i];
309
310 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
311 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
312
313 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
314 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
315
316 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
317 stats.bounces[i] += pcs->bounces[i];
318 }
319
320 return stats;
321 }
322
clear_lock_stats(struct lock_class * class)323 void clear_lock_stats(struct lock_class *class)
324 {
325 int cpu;
326
327 for_each_possible_cpu(cpu) {
328 struct lock_class_stats *cpu_stats =
329 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
330
331 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
332 }
333 memset(class->contention_point, 0, sizeof(class->contention_point));
334 memset(class->contending_point, 0, sizeof(class->contending_point));
335 }
336
get_lock_stats(struct lock_class * class)337 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
338 {
339 return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
340 }
341
lock_release_holdtime(struct held_lock * hlock)342 static void lock_release_holdtime(struct held_lock *hlock)
343 {
344 struct lock_class_stats *stats;
345 u64 holdtime;
346
347 if (!lock_stat)
348 return;
349
350 holdtime = lockstat_clock() - hlock->holdtime_stamp;
351
352 stats = get_lock_stats(hlock_class(hlock));
353 if (hlock->read)
354 lock_time_inc(&stats->read_holdtime, holdtime);
355 else
356 lock_time_inc(&stats->write_holdtime, holdtime);
357 }
358 #else
lock_release_holdtime(struct held_lock * hlock)359 static inline void lock_release_holdtime(struct held_lock *hlock)
360 {
361 }
362 #endif
363
364 /*
365 * We keep a global list of all lock classes. The list is only accessed with
366 * the lockdep spinlock lock held. free_lock_classes is a list with free
367 * elements. These elements are linked together by the lock_entry member in
368 * struct lock_class.
369 */
370 static LIST_HEAD(all_lock_classes);
371 static LIST_HEAD(free_lock_classes);
372
373 /**
374 * struct pending_free - information about data structures about to be freed
375 * @zapped: Head of a list with struct lock_class elements.
376 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
377 * are about to be freed.
378 */
379 struct pending_free {
380 struct list_head zapped;
381 DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
382 };
383
384 /**
385 * struct delayed_free - data structures used for delayed freeing
386 *
387 * A data structure for delayed freeing of data structures that may be
388 * accessed by RCU readers at the time these were freed.
389 *
390 * @rcu_head: Used to schedule an RCU callback for freeing data structures.
391 * @index: Index of @pf to which freed data structures are added.
392 * @scheduled: Whether or not an RCU callback has been scheduled.
393 * @pf: Array with information about data structures about to be freed.
394 */
395 static struct delayed_free {
396 struct rcu_head rcu_head;
397 int index;
398 int scheduled;
399 struct pending_free pf[2];
400 } delayed_free;
401
402 /*
403 * The lockdep classes are in a hash-table as well, for fast lookup:
404 */
405 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
406 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
407 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
408 #define classhashentry(key) (classhash_table + __classhashfn((key)))
409
410 static struct hlist_head classhash_table[CLASSHASH_SIZE];
411
412 /*
413 * We put the lock dependency chains into a hash-table as well, to cache
414 * their existence:
415 */
416 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
417 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
418 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
419 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
420
421 static struct hlist_head chainhash_table[CHAINHASH_SIZE];
422
423 /*
424 * the id of held_lock
425 */
hlock_id(struct held_lock * hlock)426 static inline u16 hlock_id(struct held_lock *hlock)
427 {
428 BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
429
430 return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
431 }
432
chain_hlock_class_idx(u16 hlock_id)433 static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
434 {
435 return hlock_id & (MAX_LOCKDEP_KEYS - 1);
436 }
437
438 /*
439 * The hash key of the lock dependency chains is a hash itself too:
440 * it's a hash of all locks taken up to that lock, including that lock.
441 * It's a 64-bit hash, because it's important for the keys to be
442 * unique.
443 */
iterate_chain_key(u64 key,u32 idx)444 static inline u64 iterate_chain_key(u64 key, u32 idx)
445 {
446 u32 k0 = key, k1 = key >> 32;
447
448 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
449
450 return k0 | (u64)k1 << 32;
451 }
452
lockdep_init_task(struct task_struct * task)453 void lockdep_init_task(struct task_struct *task)
454 {
455 task->lockdep_depth = 0; /* no locks held yet */
456 task->curr_chain_key = INITIAL_CHAIN_KEY;
457 task->lockdep_recursion = 0;
458 }
459
lockdep_recursion_inc(void)460 static __always_inline void lockdep_recursion_inc(void)
461 {
462 __this_cpu_inc(lockdep_recursion);
463 }
464
lockdep_recursion_finish(void)465 static __always_inline void lockdep_recursion_finish(void)
466 {
467 if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
468 __this_cpu_write(lockdep_recursion, 0);
469 }
470
lockdep_set_selftest_task(struct task_struct * task)471 void lockdep_set_selftest_task(struct task_struct *task)
472 {
473 lockdep_selftest_task_struct = task;
474 }
475
476 /*
477 * Debugging switches:
478 */
479
480 #define VERBOSE 0
481 #define VERY_VERBOSE 0
482
483 #if VERBOSE
484 # define HARDIRQ_VERBOSE 1
485 # define SOFTIRQ_VERBOSE 1
486 #else
487 # define HARDIRQ_VERBOSE 0
488 # define SOFTIRQ_VERBOSE 0
489 #endif
490
491 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
492 /*
493 * Quick filtering for interesting events:
494 */
class_filter(struct lock_class * class)495 static int class_filter(struct lock_class *class)
496 {
497 #if 0
498 /* Example */
499 if (class->name_version == 1 &&
500 !strcmp(class->name, "lockname"))
501 return 1;
502 if (class->name_version == 1 &&
503 !strcmp(class->name, "&struct->lockfield"))
504 return 1;
505 #endif
506 /* Filter everything else. 1 would be to allow everything else */
507 return 0;
508 }
509 #endif
510
verbose(struct lock_class * class)511 static int verbose(struct lock_class *class)
512 {
513 #if VERBOSE
514 return class_filter(class);
515 #endif
516 return 0;
517 }
518
print_lockdep_off(const char * bug_msg)519 static void print_lockdep_off(const char *bug_msg)
520 {
521 printk(KERN_DEBUG "%s\n", bug_msg);
522 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
523 #ifdef CONFIG_LOCK_STAT
524 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
525 #endif
526 }
527
528 unsigned long nr_stack_trace_entries;
529
530 #ifdef CONFIG_PROVE_LOCKING
531 /**
532 * struct lock_trace - single stack backtrace
533 * @hash_entry: Entry in a stack_trace_hash[] list.
534 * @hash: jhash() of @entries.
535 * @nr_entries: Number of entries in @entries.
536 * @entries: Actual stack backtrace.
537 */
538 struct lock_trace {
539 struct hlist_node hash_entry;
540 u32 hash;
541 u32 nr_entries;
542 unsigned long entries[] __aligned(sizeof(unsigned long));
543 };
544 #define LOCK_TRACE_SIZE_IN_LONGS \
545 (sizeof(struct lock_trace) / sizeof(unsigned long))
546 /*
547 * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
548 */
549 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
550 static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
551
traces_identical(struct lock_trace * t1,struct lock_trace * t2)552 static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
553 {
554 return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
555 memcmp(t1->entries, t2->entries,
556 t1->nr_entries * sizeof(t1->entries[0])) == 0;
557 }
558
save_trace(void)559 static struct lock_trace *save_trace(void)
560 {
561 struct lock_trace *trace, *t2;
562 struct hlist_head *hash_head;
563 u32 hash;
564 int max_entries;
565
566 BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
567 BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
568
569 trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
570 max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
571 LOCK_TRACE_SIZE_IN_LONGS;
572
573 if (max_entries <= 0) {
574 if (!debug_locks_off_graph_unlock())
575 return NULL;
576
577 nbcon_cpu_emergency_enter();
578 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
579 dump_stack();
580 nbcon_cpu_emergency_exit();
581
582 return NULL;
583 }
584 trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
585
586 hash = jhash(trace->entries, trace->nr_entries *
587 sizeof(trace->entries[0]), 0);
588 trace->hash = hash;
589 hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
590 hlist_for_each_entry(t2, hash_head, hash_entry) {
591 if (traces_identical(trace, t2))
592 return t2;
593 }
594 nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
595 hlist_add_head(&trace->hash_entry, hash_head);
596
597 return trace;
598 }
599
600 /* Return the number of stack traces in the stack_trace[] array. */
lockdep_stack_trace_count(void)601 u64 lockdep_stack_trace_count(void)
602 {
603 struct lock_trace *trace;
604 u64 c = 0;
605 int i;
606
607 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
608 hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
609 c++;
610 }
611 }
612
613 return c;
614 }
615
616 /* Return the number of stack hash chains that have at least one stack trace. */
lockdep_stack_hash_count(void)617 u64 lockdep_stack_hash_count(void)
618 {
619 u64 c = 0;
620 int i;
621
622 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
623 if (!hlist_empty(&stack_trace_hash[i]))
624 c++;
625
626 return c;
627 }
628 #endif
629
630 unsigned int nr_hardirq_chains;
631 unsigned int nr_softirq_chains;
632 unsigned int nr_process_chains;
633 unsigned int max_lockdep_depth;
634
635 #ifdef CONFIG_DEBUG_LOCKDEP
636 /*
637 * Various lockdep statistics:
638 */
639 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
640 #endif
641
642 #ifdef CONFIG_PROVE_LOCKING
643 /*
644 * Locking printouts:
645 */
646
647 #define __USAGE(__STATE) \
648 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
649 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
650 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
651 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
652
653 static const char *usage_str[] =
654 {
655 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
656 #include "lockdep_states.h"
657 #undef LOCKDEP_STATE
658 [LOCK_USED] = "INITIAL USE",
659 [LOCK_USED_READ] = "INITIAL READ USE",
660 /* abused as string storage for verify_lock_unused() */
661 [LOCK_USAGE_STATES] = "IN-NMI",
662 };
663 #endif
664
__get_key_name(const struct lockdep_subclass_key * key,char * str)665 const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
666 {
667 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
668 }
669
lock_flag(enum lock_usage_bit bit)670 static inline unsigned long lock_flag(enum lock_usage_bit bit)
671 {
672 return 1UL << bit;
673 }
674
get_usage_char(struct lock_class * class,enum lock_usage_bit bit)675 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
676 {
677 /*
678 * The usage character defaults to '.' (i.e., irqs disabled and not in
679 * irq context), which is the safest usage category.
680 */
681 char c = '.';
682
683 /*
684 * The order of the following usage checks matters, which will
685 * result in the outcome character as follows:
686 *
687 * - '+': irq is enabled and not in irq context
688 * - '-': in irq context and irq is disabled
689 * - '?': in irq context and irq is enabled
690 */
691 if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
692 c = '+';
693 if (class->usage_mask & lock_flag(bit))
694 c = '?';
695 } else if (class->usage_mask & lock_flag(bit))
696 c = '-';
697
698 return c;
699 }
700
get_usage_chars(struct lock_class * class,char usage[LOCK_USAGE_CHARS])701 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
702 {
703 int i = 0;
704
705 #define LOCKDEP_STATE(__STATE) \
706 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
707 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
708 #include "lockdep_states.h"
709 #undef LOCKDEP_STATE
710
711 usage[i] = '\0';
712 }
713
__print_lock_name(struct held_lock * hlock,struct lock_class * class)714 static void __print_lock_name(struct held_lock *hlock, struct lock_class *class)
715 {
716 char str[KSYM_NAME_LEN];
717 const char *name;
718
719 name = class->name;
720 if (!name) {
721 name = __get_key_name(class->key, str);
722 printk(KERN_CONT "%s", name);
723 } else {
724 printk(KERN_CONT "%s", name);
725 if (class->name_version > 1)
726 printk(KERN_CONT "#%d", class->name_version);
727 if (class->subclass)
728 printk(KERN_CONT "/%d", class->subclass);
729 if (hlock && class->print_fn)
730 class->print_fn(hlock->instance);
731 }
732 }
733
print_lock_name(struct held_lock * hlock,struct lock_class * class)734 static void print_lock_name(struct held_lock *hlock, struct lock_class *class)
735 {
736 char usage[LOCK_USAGE_CHARS];
737
738 get_usage_chars(class, usage);
739
740 printk(KERN_CONT " (");
741 __print_lock_name(hlock, class);
742 printk(KERN_CONT "){%s}-{%d:%d}", usage,
743 class->wait_type_outer ?: class->wait_type_inner,
744 class->wait_type_inner);
745 }
746
print_lockdep_cache(struct lockdep_map * lock)747 static void print_lockdep_cache(struct lockdep_map *lock)
748 {
749 const char *name;
750 char str[KSYM_NAME_LEN];
751
752 name = lock->name;
753 if (!name)
754 name = __get_key_name(lock->key->subkeys, str);
755
756 printk(KERN_CONT "%s", name);
757 }
758
print_lock(struct held_lock * hlock)759 static void print_lock(struct held_lock *hlock)
760 {
761 /*
762 * We can be called locklessly through debug_show_all_locks() so be
763 * extra careful, the hlock might have been released and cleared.
764 *
765 * If this indeed happens, lets pretend it does not hurt to continue
766 * to print the lock unless the hlock class_idx does not point to a
767 * registered class. The rationale here is: since we don't attempt
768 * to distinguish whether we are in this situation, if it just
769 * happened we can't count on class_idx to tell either.
770 */
771 struct lock_class *lock = hlock_class(hlock);
772
773 if (!lock) {
774 printk(KERN_CONT "<RELEASED>\n");
775 return;
776 }
777
778 printk(KERN_CONT "%px", hlock->instance);
779 print_lock_name(hlock, lock);
780 printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
781 }
782
lockdep_print_held_locks(struct task_struct * p)783 static void lockdep_print_held_locks(struct task_struct *p)
784 {
785 int i, depth = READ_ONCE(p->lockdep_depth);
786
787 if (!depth)
788 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
789 else
790 printk("%d lock%s held by %s/%d:\n", depth,
791 depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
792 /*
793 * It's not reliable to print a task's held locks if it's not sleeping
794 * and it's not the current task.
795 */
796 if (p != current && task_is_running(p))
797 return;
798 for (i = 0; i < depth; i++) {
799 printk(" #%d: ", i);
800 print_lock(p->held_locks + i);
801 }
802 }
803
print_kernel_ident(void)804 static void print_kernel_ident(void)
805 {
806 printk("%s %.*s %s\n", init_utsname()->release,
807 (int)strcspn(init_utsname()->version, " "),
808 init_utsname()->version,
809 print_tainted());
810 }
811
very_verbose(struct lock_class * class)812 static int very_verbose(struct lock_class *class)
813 {
814 #if VERY_VERBOSE
815 return class_filter(class);
816 #endif
817 return 0;
818 }
819
820 /*
821 * Is this the address of a static object:
822 */
823 #ifdef __KERNEL__
static_obj(const void * obj)824 static int static_obj(const void *obj)
825 {
826 unsigned long addr = (unsigned long) obj;
827
828 if (is_kernel_core_data(addr))
829 return 1;
830
831 /*
832 * keys are allowed in the __ro_after_init section.
833 */
834 if (is_kernel_rodata(addr))
835 return 1;
836
837 /*
838 * in initdata section and used during bootup only?
839 * NOTE: On some platforms the initdata section is
840 * outside of the _stext ... _end range.
841 */
842 if (system_state < SYSTEM_FREEING_INITMEM &&
843 init_section_contains((void *)addr, 1))
844 return 1;
845
846 /*
847 * in-kernel percpu var?
848 */
849 if (is_kernel_percpu_address(addr))
850 return 1;
851
852 /*
853 * module static or percpu var?
854 */
855 return is_module_address(addr) || is_module_percpu_address(addr);
856 }
857 #endif
858
859 /*
860 * To make lock name printouts unique, we calculate a unique
861 * class->name_version generation counter. The caller must hold the graph
862 * lock.
863 */
count_matching_names(struct lock_class * new_class)864 static int count_matching_names(struct lock_class *new_class)
865 {
866 struct lock_class *class;
867 int count = 0;
868
869 if (!new_class->name)
870 return 0;
871
872 list_for_each_entry(class, &all_lock_classes, lock_entry) {
873 if (new_class->key - new_class->subclass == class->key)
874 return class->name_version;
875 if (class->name && !strcmp(class->name, new_class->name))
876 count = max(count, class->name_version);
877 }
878
879 return count + 1;
880 }
881
882 /* used from NMI context -- must be lockless */
883 static noinstr struct lock_class *
look_up_lock_class(const struct lockdep_map * lock,unsigned int subclass)884 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
885 {
886 struct lockdep_subclass_key *key;
887 struct hlist_head *hash_head;
888 struct lock_class *class;
889
890 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
891 instrumentation_begin();
892 debug_locks_off();
893 nbcon_cpu_emergency_enter();
894 printk(KERN_ERR
895 "BUG: looking up invalid subclass: %u\n", subclass);
896 printk(KERN_ERR
897 "turning off the locking correctness validator.\n");
898 dump_stack();
899 nbcon_cpu_emergency_exit();
900 instrumentation_end();
901 return NULL;
902 }
903
904 /*
905 * If it is not initialised then it has never been locked,
906 * so it won't be present in the hash table.
907 */
908 if (unlikely(!lock->key))
909 return NULL;
910
911 /*
912 * NOTE: the class-key must be unique. For dynamic locks, a static
913 * lock_class_key variable is passed in through the mutex_init()
914 * (or spin_lock_init()) call - which acts as the key. For static
915 * locks we use the lock object itself as the key.
916 */
917 BUILD_BUG_ON(sizeof(struct lock_class_key) >
918 sizeof(struct lockdep_map));
919
920 key = lock->key->subkeys + subclass;
921
922 hash_head = classhashentry(key);
923
924 /*
925 * We do an RCU walk of the hash, see lockdep_free_key_range().
926 */
927 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
928 return NULL;
929
930 hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
931 if (class->key == key) {
932 /*
933 * Huh! same key, different name? Did someone trample
934 * on some memory? We're most confused.
935 */
936 WARN_ONCE(class->name != lock->name &&
937 lock->key != &__lockdep_no_validate__,
938 "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n",
939 lock->name, lock->key, class->name);
940 return class;
941 }
942 }
943
944 return NULL;
945 }
946
947 /*
948 * Static locks do not have their class-keys yet - for them the key is
949 * the lock object itself. If the lock is in the per cpu area, the
950 * canonical address of the lock (per cpu offset removed) is used.
951 */
assign_lock_key(struct lockdep_map * lock)952 static bool assign_lock_key(struct lockdep_map *lock)
953 {
954 unsigned long can_addr, addr = (unsigned long)lock;
955
956 #ifdef __KERNEL__
957 /*
958 * lockdep_free_key_range() assumes that struct lock_class_key
959 * objects do not overlap. Since we use the address of lock
960 * objects as class key for static objects, check whether the
961 * size of lock_class_key objects does not exceed the size of
962 * the smallest lock object.
963 */
964 BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
965 #endif
966
967 if (__is_kernel_percpu_address(addr, &can_addr))
968 lock->key = (void *)can_addr;
969 else if (__is_module_percpu_address(addr, &can_addr))
970 lock->key = (void *)can_addr;
971 else if (static_obj(lock))
972 lock->key = (void *)lock;
973 else {
974 /* Debug-check: all keys must be persistent! */
975 debug_locks_off();
976 nbcon_cpu_emergency_enter();
977 pr_err("INFO: trying to register non-static key.\n");
978 pr_err("The code is fine but needs lockdep annotation, or maybe\n");
979 pr_err("you didn't initialize this object before use?\n");
980 pr_err("turning off the locking correctness validator.\n");
981 dump_stack();
982 nbcon_cpu_emergency_exit();
983 return false;
984 }
985
986 return true;
987 }
988
989 #ifdef CONFIG_DEBUG_LOCKDEP
990
991 /* Check whether element @e occurs in list @h */
in_list(struct list_head * e,struct list_head * h)992 static bool in_list(struct list_head *e, struct list_head *h)
993 {
994 struct list_head *f;
995
996 list_for_each(f, h) {
997 if (e == f)
998 return true;
999 }
1000
1001 return false;
1002 }
1003
1004 /*
1005 * Check whether entry @e occurs in any of the locks_after or locks_before
1006 * lists.
1007 */
in_any_class_list(struct list_head * e)1008 static bool in_any_class_list(struct list_head *e)
1009 {
1010 struct lock_class *class;
1011 int i;
1012
1013 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1014 class = &lock_classes[i];
1015 if (in_list(e, &class->locks_after) ||
1016 in_list(e, &class->locks_before))
1017 return true;
1018 }
1019 return false;
1020 }
1021
class_lock_list_valid(struct lock_class * c,struct list_head * h)1022 static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
1023 {
1024 struct lock_list *e;
1025
1026 list_for_each_entry(e, h, entry) {
1027 if (e->links_to != c) {
1028 printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
1029 c->name ? : "(?)",
1030 (unsigned long)(e - list_entries),
1031 e->links_to && e->links_to->name ?
1032 e->links_to->name : "(?)",
1033 e->class && e->class->name ? e->class->name :
1034 "(?)");
1035 return false;
1036 }
1037 }
1038 return true;
1039 }
1040
1041 #ifdef CONFIG_PROVE_LOCKING
1042 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1043 #endif
1044
check_lock_chain_key(struct lock_chain * chain)1045 static bool check_lock_chain_key(struct lock_chain *chain)
1046 {
1047 #ifdef CONFIG_PROVE_LOCKING
1048 u64 chain_key = INITIAL_CHAIN_KEY;
1049 int i;
1050
1051 for (i = chain->base; i < chain->base + chain->depth; i++)
1052 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
1053 /*
1054 * The 'unsigned long long' casts avoid that a compiler warning
1055 * is reported when building tools/lib/lockdep.
1056 */
1057 if (chain->chain_key != chain_key) {
1058 printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
1059 (unsigned long long)(chain - lock_chains),
1060 (unsigned long long)chain->chain_key,
1061 (unsigned long long)chain_key);
1062 return false;
1063 }
1064 #endif
1065 return true;
1066 }
1067
in_any_zapped_class_list(struct lock_class * class)1068 static bool in_any_zapped_class_list(struct lock_class *class)
1069 {
1070 struct pending_free *pf;
1071 int i;
1072
1073 for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
1074 if (in_list(&class->lock_entry, &pf->zapped))
1075 return true;
1076 }
1077
1078 return false;
1079 }
1080
__check_data_structures(void)1081 static bool __check_data_structures(void)
1082 {
1083 struct lock_class *class;
1084 struct lock_chain *chain;
1085 struct hlist_head *head;
1086 struct lock_list *e;
1087 int i;
1088
1089 /* Check whether all classes occur in a lock list. */
1090 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1091 class = &lock_classes[i];
1092 if (!in_list(&class->lock_entry, &all_lock_classes) &&
1093 !in_list(&class->lock_entry, &free_lock_classes) &&
1094 !in_any_zapped_class_list(class)) {
1095 printk(KERN_INFO "class %px/%s is not in any class list\n",
1096 class, class->name ? : "(?)");
1097 return false;
1098 }
1099 }
1100
1101 /* Check whether all classes have valid lock lists. */
1102 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1103 class = &lock_classes[i];
1104 if (!class_lock_list_valid(class, &class->locks_before))
1105 return false;
1106 if (!class_lock_list_valid(class, &class->locks_after))
1107 return false;
1108 }
1109
1110 /* Check the chain_key of all lock chains. */
1111 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1112 head = chainhash_table + i;
1113 hlist_for_each_entry_rcu(chain, head, entry) {
1114 if (!check_lock_chain_key(chain))
1115 return false;
1116 }
1117 }
1118
1119 /*
1120 * Check whether all list entries that are in use occur in a class
1121 * lock list.
1122 */
1123 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1124 e = list_entries + i;
1125 if (!in_any_class_list(&e->entry)) {
1126 printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1127 (unsigned int)(e - list_entries),
1128 e->class->name ? : "(?)",
1129 e->links_to->name ? : "(?)");
1130 return false;
1131 }
1132 }
1133
1134 /*
1135 * Check whether all list entries that are not in use do not occur in
1136 * a class lock list.
1137 */
1138 for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1139 e = list_entries + i;
1140 if (in_any_class_list(&e->entry)) {
1141 printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1142 (unsigned int)(e - list_entries),
1143 e->class && e->class->name ? e->class->name :
1144 "(?)",
1145 e->links_to && e->links_to->name ?
1146 e->links_to->name : "(?)");
1147 return false;
1148 }
1149 }
1150
1151 return true;
1152 }
1153
1154 int check_consistency = 0;
1155 module_param(check_consistency, int, 0644);
1156
check_data_structures(void)1157 static void check_data_structures(void)
1158 {
1159 static bool once = false;
1160
1161 if (check_consistency && !once) {
1162 if (!__check_data_structures()) {
1163 once = true;
1164 WARN_ON(once);
1165 }
1166 }
1167 }
1168
1169 #else /* CONFIG_DEBUG_LOCKDEP */
1170
check_data_structures(void)1171 static inline void check_data_structures(void) { }
1172
1173 #endif /* CONFIG_DEBUG_LOCKDEP */
1174
1175 static void init_chain_block_buckets(void);
1176
1177 /*
1178 * Initialize the lock_classes[] array elements, the free_lock_classes list
1179 * and also the delayed_free structure.
1180 */
init_data_structures_once(void)1181 static void init_data_structures_once(void)
1182 {
1183 static bool __read_mostly ds_initialized, rcu_head_initialized;
1184 int i;
1185
1186 if (likely(rcu_head_initialized))
1187 return;
1188
1189 if (system_state >= SYSTEM_SCHEDULING) {
1190 init_rcu_head(&delayed_free.rcu_head);
1191 rcu_head_initialized = true;
1192 }
1193
1194 if (ds_initialized)
1195 return;
1196
1197 ds_initialized = true;
1198
1199 INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1200 INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1201
1202 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1203 list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1204 INIT_LIST_HEAD(&lock_classes[i].locks_after);
1205 INIT_LIST_HEAD(&lock_classes[i].locks_before);
1206 }
1207 init_chain_block_buckets();
1208 }
1209
keyhashentry(const struct lock_class_key * key)1210 static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1211 {
1212 unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1213
1214 return lock_keys_hash + hash;
1215 }
1216
1217 /* Register a dynamically allocated key. */
lockdep_register_key(struct lock_class_key * key)1218 void lockdep_register_key(struct lock_class_key *key)
1219 {
1220 struct hlist_head *hash_head;
1221 struct lock_class_key *k;
1222 unsigned long flags;
1223
1224 if (WARN_ON_ONCE(static_obj(key)))
1225 return;
1226 hash_head = keyhashentry(key);
1227
1228 raw_local_irq_save(flags);
1229 if (!graph_lock())
1230 goto restore_irqs;
1231 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1232 if (WARN_ON_ONCE(k == key))
1233 goto out_unlock;
1234 }
1235 hlist_add_head_rcu(&key->hash_entry, hash_head);
1236 out_unlock:
1237 graph_unlock();
1238 restore_irqs:
1239 raw_local_irq_restore(flags);
1240 }
1241 EXPORT_SYMBOL_GPL(lockdep_register_key);
1242
1243 /* Check whether a key has been registered as a dynamic key. */
is_dynamic_key(const struct lock_class_key * key)1244 static bool is_dynamic_key(const struct lock_class_key *key)
1245 {
1246 struct hlist_head *hash_head;
1247 struct lock_class_key *k;
1248 bool found = false;
1249
1250 if (WARN_ON_ONCE(static_obj(key)))
1251 return false;
1252
1253 /*
1254 * If lock debugging is disabled lock_keys_hash[] may contain
1255 * pointers to memory that has already been freed. Avoid triggering
1256 * a use-after-free in that case by returning early.
1257 */
1258 if (!debug_locks)
1259 return true;
1260
1261 hash_head = keyhashentry(key);
1262
1263 rcu_read_lock();
1264 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1265 if (k == key) {
1266 found = true;
1267 break;
1268 }
1269 }
1270 rcu_read_unlock();
1271
1272 return found;
1273 }
1274
1275 /*
1276 * Register a lock's class in the hash-table, if the class is not present
1277 * yet. Otherwise we look it up. We cache the result in the lock object
1278 * itself, so actual lookup of the hash should be once per lock object.
1279 */
1280 static struct lock_class *
register_lock_class(struct lockdep_map * lock,unsigned int subclass,int force)1281 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1282 {
1283 struct lockdep_subclass_key *key;
1284 struct hlist_head *hash_head;
1285 struct lock_class *class;
1286 int idx;
1287
1288 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1289
1290 class = look_up_lock_class(lock, subclass);
1291 if (likely(class))
1292 goto out_set_class_cache;
1293
1294 if (!lock->key) {
1295 if (!assign_lock_key(lock))
1296 return NULL;
1297 } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1298 return NULL;
1299 }
1300
1301 key = lock->key->subkeys + subclass;
1302 hash_head = classhashentry(key);
1303
1304 if (!graph_lock()) {
1305 return NULL;
1306 }
1307 /*
1308 * We have to do the hash-walk again, to avoid races
1309 * with another CPU:
1310 */
1311 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1312 if (class->key == key)
1313 goto out_unlock_set;
1314 }
1315
1316 init_data_structures_once();
1317
1318 /* Allocate a new lock class and add it to the hash. */
1319 class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1320 lock_entry);
1321 if (!class) {
1322 if (!debug_locks_off_graph_unlock()) {
1323 return NULL;
1324 }
1325
1326 nbcon_cpu_emergency_enter();
1327 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1328 dump_stack();
1329 nbcon_cpu_emergency_exit();
1330 return NULL;
1331 }
1332 nr_lock_classes++;
1333 __set_bit(class - lock_classes, lock_classes_in_use);
1334 debug_atomic_inc(nr_unused_locks);
1335 class->key = key;
1336 class->name = lock->name;
1337 class->subclass = subclass;
1338 WARN_ON_ONCE(!list_empty(&class->locks_before));
1339 WARN_ON_ONCE(!list_empty(&class->locks_after));
1340 class->name_version = count_matching_names(class);
1341 class->wait_type_inner = lock->wait_type_inner;
1342 class->wait_type_outer = lock->wait_type_outer;
1343 class->lock_type = lock->lock_type;
1344 /*
1345 * We use RCU's safe list-add method to make
1346 * parallel walking of the hash-list safe:
1347 */
1348 hlist_add_head_rcu(&class->hash_entry, hash_head);
1349 /*
1350 * Remove the class from the free list and add it to the global list
1351 * of classes.
1352 */
1353 list_move_tail(&class->lock_entry, &all_lock_classes);
1354 idx = class - lock_classes;
1355 if (idx > max_lock_class_idx)
1356 max_lock_class_idx = idx;
1357
1358 if (verbose(class)) {
1359 graph_unlock();
1360
1361 nbcon_cpu_emergency_enter();
1362 printk("\nnew class %px: %s", class->key, class->name);
1363 if (class->name_version > 1)
1364 printk(KERN_CONT "#%d", class->name_version);
1365 printk(KERN_CONT "\n");
1366 dump_stack();
1367 nbcon_cpu_emergency_exit();
1368
1369 if (!graph_lock()) {
1370 return NULL;
1371 }
1372 }
1373 out_unlock_set:
1374 graph_unlock();
1375
1376 out_set_class_cache:
1377 if (!subclass || force)
1378 lock->class_cache[0] = class;
1379 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1380 lock->class_cache[subclass] = class;
1381
1382 /*
1383 * Hash collision, did we smoke some? We found a class with a matching
1384 * hash but the subclass -- which is hashed in -- didn't match.
1385 */
1386 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1387 return NULL;
1388
1389 return class;
1390 }
1391
1392 #ifdef CONFIG_PROVE_LOCKING
1393 /*
1394 * Allocate a lockdep entry. (assumes the graph_lock held, returns
1395 * with NULL on failure)
1396 */
alloc_list_entry(void)1397 static struct lock_list *alloc_list_entry(void)
1398 {
1399 int idx = find_first_zero_bit(list_entries_in_use,
1400 ARRAY_SIZE(list_entries));
1401
1402 if (idx >= ARRAY_SIZE(list_entries)) {
1403 if (!debug_locks_off_graph_unlock())
1404 return NULL;
1405
1406 nbcon_cpu_emergency_enter();
1407 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1408 dump_stack();
1409 nbcon_cpu_emergency_exit();
1410 return NULL;
1411 }
1412 nr_list_entries++;
1413 __set_bit(idx, list_entries_in_use);
1414 return list_entries + idx;
1415 }
1416
1417 /*
1418 * Add a new dependency to the head of the list:
1419 */
add_lock_to_list(struct lock_class * this,struct lock_class * links_to,struct list_head * head,u16 distance,u8 dep,const struct lock_trace * trace)1420 static int add_lock_to_list(struct lock_class *this,
1421 struct lock_class *links_to, struct list_head *head,
1422 u16 distance, u8 dep,
1423 const struct lock_trace *trace)
1424 {
1425 struct lock_list *entry;
1426 /*
1427 * Lock not present yet - get a new dependency struct and
1428 * add it to the list:
1429 */
1430 entry = alloc_list_entry();
1431 if (!entry)
1432 return 0;
1433
1434 entry->class = this;
1435 entry->links_to = links_to;
1436 entry->dep = dep;
1437 entry->distance = distance;
1438 entry->trace = trace;
1439 /*
1440 * Both allocation and removal are done under the graph lock; but
1441 * iteration is under RCU-sched; see look_up_lock_class() and
1442 * lockdep_free_key_range().
1443 */
1444 list_add_tail_rcu(&entry->entry, head);
1445
1446 return 1;
1447 }
1448
1449 /*
1450 * For good efficiency of modular, we use power of 2
1451 */
1452 #define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
1453 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
1454
1455 /*
1456 * The circular_queue and helpers are used to implement graph
1457 * breadth-first search (BFS) algorithm, by which we can determine
1458 * whether there is a path from a lock to another. In deadlock checks,
1459 * a path from the next lock to be acquired to a previous held lock
1460 * indicates that adding the <prev> -> <next> lock dependency will
1461 * produce a circle in the graph. Breadth-first search instead of
1462 * depth-first search is used in order to find the shortest (circular)
1463 * path.
1464 */
1465 struct circular_queue {
1466 struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1467 unsigned int front, rear;
1468 };
1469
1470 static struct circular_queue lock_cq;
1471
1472 unsigned int max_bfs_queue_depth;
1473
1474 static unsigned int lockdep_dependency_gen_id;
1475
__cq_init(struct circular_queue * cq)1476 static inline void __cq_init(struct circular_queue *cq)
1477 {
1478 cq->front = cq->rear = 0;
1479 lockdep_dependency_gen_id++;
1480 }
1481
__cq_empty(struct circular_queue * cq)1482 static inline int __cq_empty(struct circular_queue *cq)
1483 {
1484 return (cq->front == cq->rear);
1485 }
1486
__cq_full(struct circular_queue * cq)1487 static inline int __cq_full(struct circular_queue *cq)
1488 {
1489 return ((cq->rear + 1) & CQ_MASK) == cq->front;
1490 }
1491
__cq_enqueue(struct circular_queue * cq,struct lock_list * elem)1492 static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1493 {
1494 if (__cq_full(cq))
1495 return -1;
1496
1497 cq->element[cq->rear] = elem;
1498 cq->rear = (cq->rear + 1) & CQ_MASK;
1499 return 0;
1500 }
1501
1502 /*
1503 * Dequeue an element from the circular_queue, return a lock_list if
1504 * the queue is not empty, or NULL if otherwise.
1505 */
__cq_dequeue(struct circular_queue * cq)1506 static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1507 {
1508 struct lock_list * lock;
1509
1510 if (__cq_empty(cq))
1511 return NULL;
1512
1513 lock = cq->element[cq->front];
1514 cq->front = (cq->front + 1) & CQ_MASK;
1515
1516 return lock;
1517 }
1518
__cq_get_elem_count(struct circular_queue * cq)1519 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
1520 {
1521 return (cq->rear - cq->front) & CQ_MASK;
1522 }
1523
mark_lock_accessed(struct lock_list * lock)1524 static inline void mark_lock_accessed(struct lock_list *lock)
1525 {
1526 lock->class->dep_gen_id = lockdep_dependency_gen_id;
1527 }
1528
visit_lock_entry(struct lock_list * lock,struct lock_list * parent)1529 static inline void visit_lock_entry(struct lock_list *lock,
1530 struct lock_list *parent)
1531 {
1532 lock->parent = parent;
1533 }
1534
lock_accessed(struct lock_list * lock)1535 static inline unsigned long lock_accessed(struct lock_list *lock)
1536 {
1537 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1538 }
1539
get_lock_parent(struct lock_list * child)1540 static inline struct lock_list *get_lock_parent(struct lock_list *child)
1541 {
1542 return child->parent;
1543 }
1544
get_lock_depth(struct lock_list * child)1545 static inline int get_lock_depth(struct lock_list *child)
1546 {
1547 int depth = 0;
1548 struct lock_list *parent;
1549
1550 while ((parent = get_lock_parent(child))) {
1551 child = parent;
1552 depth++;
1553 }
1554 return depth;
1555 }
1556
1557 /*
1558 * Return the forward or backward dependency list.
1559 *
1560 * @lock: the lock_list to get its class's dependency list
1561 * @offset: the offset to struct lock_class to determine whether it is
1562 * locks_after or locks_before
1563 */
get_dep_list(struct lock_list * lock,int offset)1564 static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1565 {
1566 void *lock_class = lock->class;
1567
1568 return lock_class + offset;
1569 }
1570 /*
1571 * Return values of a bfs search:
1572 *
1573 * BFS_E* indicates an error
1574 * BFS_R* indicates a result (match or not)
1575 *
1576 * BFS_EINVALIDNODE: Find a invalid node in the graph.
1577 *
1578 * BFS_EQUEUEFULL: The queue is full while doing the bfs.
1579 *
1580 * BFS_RMATCH: Find the matched node in the graph, and put that node into
1581 * *@target_entry.
1582 *
1583 * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
1584 * _unchanged_.
1585 */
1586 enum bfs_result {
1587 BFS_EINVALIDNODE = -2,
1588 BFS_EQUEUEFULL = -1,
1589 BFS_RMATCH = 0,
1590 BFS_RNOMATCH = 1,
1591 };
1592
1593 /*
1594 * bfs_result < 0 means error
1595 */
bfs_error(enum bfs_result res)1596 static inline bool bfs_error(enum bfs_result res)
1597 {
1598 return res < 0;
1599 }
1600
1601 /*
1602 * DEP_*_BIT in lock_list::dep
1603 *
1604 * For dependency @prev -> @next:
1605 *
1606 * SR: @prev is shared reader (->read != 0) and @next is recursive reader
1607 * (->read == 2)
1608 * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
1609 * SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
1610 * EN: @prev is exclusive locker and @next is non-recursive locker
1611 *
1612 * Note that we define the value of DEP_*_BITs so that:
1613 * bit0 is prev->read == 0
1614 * bit1 is next->read != 2
1615 */
1616 #define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
1617 #define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
1618 #define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
1619 #define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
1620
1621 #define DEP_SR_MASK (1U << (DEP_SR_BIT))
1622 #define DEP_ER_MASK (1U << (DEP_ER_BIT))
1623 #define DEP_SN_MASK (1U << (DEP_SN_BIT))
1624 #define DEP_EN_MASK (1U << (DEP_EN_BIT))
1625
1626 static inline unsigned int
__calc_dep_bit(struct held_lock * prev,struct held_lock * next)1627 __calc_dep_bit(struct held_lock *prev, struct held_lock *next)
1628 {
1629 return (prev->read == 0) + ((next->read != 2) << 1);
1630 }
1631
calc_dep(struct held_lock * prev,struct held_lock * next)1632 static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
1633 {
1634 return 1U << __calc_dep_bit(prev, next);
1635 }
1636
1637 /*
1638 * calculate the dep_bit for backwards edges. We care about whether @prev is
1639 * shared and whether @next is recursive.
1640 */
1641 static inline unsigned int
__calc_dep_bitb(struct held_lock * prev,struct held_lock * next)1642 __calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
1643 {
1644 return (next->read != 2) + ((prev->read == 0) << 1);
1645 }
1646
calc_depb(struct held_lock * prev,struct held_lock * next)1647 static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
1648 {
1649 return 1U << __calc_dep_bitb(prev, next);
1650 }
1651
1652 /*
1653 * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
1654 * search.
1655 */
__bfs_init_root(struct lock_list * lock,struct lock_class * class)1656 static inline void __bfs_init_root(struct lock_list *lock,
1657 struct lock_class *class)
1658 {
1659 lock->class = class;
1660 lock->parent = NULL;
1661 lock->only_xr = 0;
1662 }
1663
1664 /*
1665 * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
1666 * root for a BFS search.
1667 *
1668 * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
1669 * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
1670 * and -(S*)->.
1671 */
bfs_init_root(struct lock_list * lock,struct held_lock * hlock)1672 static inline void bfs_init_root(struct lock_list *lock,
1673 struct held_lock *hlock)
1674 {
1675 __bfs_init_root(lock, hlock_class(hlock));
1676 lock->only_xr = (hlock->read == 2);
1677 }
1678
1679 /*
1680 * Similar to bfs_init_root() but initialize the root for backwards BFS.
1681 *
1682 * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
1683 * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
1684 * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
1685 */
bfs_init_rootb(struct lock_list * lock,struct held_lock * hlock)1686 static inline void bfs_init_rootb(struct lock_list *lock,
1687 struct held_lock *hlock)
1688 {
1689 __bfs_init_root(lock, hlock_class(hlock));
1690 lock->only_xr = (hlock->read != 0);
1691 }
1692
__bfs_next(struct lock_list * lock,int offset)1693 static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
1694 {
1695 if (!lock || !lock->parent)
1696 return NULL;
1697
1698 return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
1699 &lock->entry, struct lock_list, entry);
1700 }
1701
1702 /*
1703 * Breadth-First Search to find a strong path in the dependency graph.
1704 *
1705 * @source_entry: the source of the path we are searching for.
1706 * @data: data used for the second parameter of @match function
1707 * @match: match function for the search
1708 * @target_entry: pointer to the target of a matched path
1709 * @offset: the offset to struct lock_class to determine whether it is
1710 * locks_after or locks_before
1711 *
1712 * We may have multiple edges (considering different kinds of dependencies,
1713 * e.g. ER and SN) between two nodes in the dependency graph. But
1714 * only the strong dependency path in the graph is relevant to deadlocks. A
1715 * strong dependency path is a dependency path that doesn't have two adjacent
1716 * dependencies as -(*R)-> -(S*)->, please see:
1717 *
1718 * Documentation/locking/lockdep-design.rst
1719 *
1720 * for more explanation of the definition of strong dependency paths
1721 *
1722 * In __bfs(), we only traverse in the strong dependency path:
1723 *
1724 * In lock_list::only_xr, we record whether the previous dependency only
1725 * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
1726 * filter out any -(S*)-> in the current dependency and after that, the
1727 * ->only_xr is set according to whether we only have -(*R)-> left.
1728 */
__bfs(struct lock_list * source_entry,void * data,bool (* match)(struct lock_list * entry,void * data),bool (* skip)(struct lock_list * entry,void * data),struct lock_list ** target_entry,int offset)1729 static enum bfs_result __bfs(struct lock_list *source_entry,
1730 void *data,
1731 bool (*match)(struct lock_list *entry, void *data),
1732 bool (*skip)(struct lock_list *entry, void *data),
1733 struct lock_list **target_entry,
1734 int offset)
1735 {
1736 struct circular_queue *cq = &lock_cq;
1737 struct lock_list *lock = NULL;
1738 struct lock_list *entry;
1739 struct list_head *head;
1740 unsigned int cq_depth;
1741 bool first;
1742
1743 lockdep_assert_locked();
1744
1745 __cq_init(cq);
1746 __cq_enqueue(cq, source_entry);
1747
1748 while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
1749 if (!lock->class)
1750 return BFS_EINVALIDNODE;
1751
1752 /*
1753 * Step 1: check whether we already finish on this one.
1754 *
1755 * If we have visited all the dependencies from this @lock to
1756 * others (iow, if we have visited all lock_list entries in
1757 * @lock->class->locks_{after,before}) we skip, otherwise go
1758 * and visit all the dependencies in the list and mark this
1759 * list accessed.
1760 */
1761 if (lock_accessed(lock))
1762 continue;
1763 else
1764 mark_lock_accessed(lock);
1765
1766 /*
1767 * Step 2: check whether prev dependency and this form a strong
1768 * dependency path.
1769 */
1770 if (lock->parent) { /* Parent exists, check prev dependency */
1771 u8 dep = lock->dep;
1772 bool prev_only_xr = lock->parent->only_xr;
1773
1774 /*
1775 * Mask out all -(S*)-> if we only have *R in previous
1776 * step, because -(*R)-> -(S*)-> don't make up a strong
1777 * dependency.
1778 */
1779 if (prev_only_xr)
1780 dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
1781
1782 /* If nothing left, we skip */
1783 if (!dep)
1784 continue;
1785
1786 /* If there are only -(*R)-> left, set that for the next step */
1787 lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
1788 }
1789
1790 /*
1791 * Step 3: we haven't visited this and there is a strong
1792 * dependency path to this, so check with @match.
1793 * If @skip is provide and returns true, we skip this
1794 * lock (and any path this lock is in).
1795 */
1796 if (skip && skip(lock, data))
1797 continue;
1798
1799 if (match(lock, data)) {
1800 *target_entry = lock;
1801 return BFS_RMATCH;
1802 }
1803
1804 /*
1805 * Step 4: if not match, expand the path by adding the
1806 * forward or backwards dependencies in the search
1807 *
1808 */
1809 first = true;
1810 head = get_dep_list(lock, offset);
1811 list_for_each_entry_rcu(entry, head, entry) {
1812 visit_lock_entry(entry, lock);
1813
1814 /*
1815 * Note we only enqueue the first of the list into the
1816 * queue, because we can always find a sibling
1817 * dependency from one (see __bfs_next()), as a result
1818 * the space of queue is saved.
1819 */
1820 if (!first)
1821 continue;
1822
1823 first = false;
1824
1825 if (__cq_enqueue(cq, entry))
1826 return BFS_EQUEUEFULL;
1827
1828 cq_depth = __cq_get_elem_count(cq);
1829 if (max_bfs_queue_depth < cq_depth)
1830 max_bfs_queue_depth = cq_depth;
1831 }
1832 }
1833
1834 return BFS_RNOMATCH;
1835 }
1836
1837 static inline enum bfs_result
__bfs_forwards(struct lock_list * src_entry,void * data,bool (* match)(struct lock_list * entry,void * data),bool (* skip)(struct lock_list * entry,void * data),struct lock_list ** target_entry)1838 __bfs_forwards(struct lock_list *src_entry,
1839 void *data,
1840 bool (*match)(struct lock_list *entry, void *data),
1841 bool (*skip)(struct lock_list *entry, void *data),
1842 struct lock_list **target_entry)
1843 {
1844 return __bfs(src_entry, data, match, skip, target_entry,
1845 offsetof(struct lock_class, locks_after));
1846
1847 }
1848
1849 static inline enum bfs_result
__bfs_backwards(struct lock_list * src_entry,void * data,bool (* match)(struct lock_list * entry,void * data),bool (* skip)(struct lock_list * entry,void * data),struct lock_list ** target_entry)1850 __bfs_backwards(struct lock_list *src_entry,
1851 void *data,
1852 bool (*match)(struct lock_list *entry, void *data),
1853 bool (*skip)(struct lock_list *entry, void *data),
1854 struct lock_list **target_entry)
1855 {
1856 return __bfs(src_entry, data, match, skip, target_entry,
1857 offsetof(struct lock_class, locks_before));
1858
1859 }
1860
print_lock_trace(const struct lock_trace * trace,unsigned int spaces)1861 static void print_lock_trace(const struct lock_trace *trace,
1862 unsigned int spaces)
1863 {
1864 stack_trace_print(trace->entries, trace->nr_entries, spaces);
1865 }
1866
1867 /*
1868 * Print a dependency chain entry (this is only done when a deadlock
1869 * has been detected):
1870 */
1871 static noinline void
print_circular_bug_entry(struct lock_list * target,int depth)1872 print_circular_bug_entry(struct lock_list *target, int depth)
1873 {
1874 if (debug_locks_silent)
1875 return;
1876 printk("\n-> #%u", depth);
1877 print_lock_name(NULL, target->class);
1878 printk(KERN_CONT ":\n");
1879 print_lock_trace(target->trace, 6);
1880 }
1881
1882 static void
print_circular_lock_scenario(struct held_lock * src,struct held_lock * tgt,struct lock_list * prt)1883 print_circular_lock_scenario(struct held_lock *src,
1884 struct held_lock *tgt,
1885 struct lock_list *prt)
1886 {
1887 struct lock_class *source = hlock_class(src);
1888 struct lock_class *target = hlock_class(tgt);
1889 struct lock_class *parent = prt->class;
1890 int src_read = src->read;
1891 int tgt_read = tgt->read;
1892
1893 /*
1894 * A direct locking problem where unsafe_class lock is taken
1895 * directly by safe_class lock, then all we need to show
1896 * is the deadlock scenario, as it is obvious that the
1897 * unsafe lock is taken under the safe lock.
1898 *
1899 * But if there is a chain instead, where the safe lock takes
1900 * an intermediate lock (middle_class) where this lock is
1901 * not the same as the safe lock, then the lock chain is
1902 * used to describe the problem. Otherwise we would need
1903 * to show a different CPU case for each link in the chain
1904 * from the safe_class lock to the unsafe_class lock.
1905 */
1906 if (parent != source) {
1907 printk("Chain exists of:\n ");
1908 __print_lock_name(src, source);
1909 printk(KERN_CONT " --> ");
1910 __print_lock_name(NULL, parent);
1911 printk(KERN_CONT " --> ");
1912 __print_lock_name(tgt, target);
1913 printk(KERN_CONT "\n\n");
1914 }
1915
1916 printk(" Possible unsafe locking scenario:\n\n");
1917 printk(" CPU0 CPU1\n");
1918 printk(" ---- ----\n");
1919 if (tgt_read != 0)
1920 printk(" rlock(");
1921 else
1922 printk(" lock(");
1923 __print_lock_name(tgt, target);
1924 printk(KERN_CONT ");\n");
1925 printk(" lock(");
1926 __print_lock_name(NULL, parent);
1927 printk(KERN_CONT ");\n");
1928 printk(" lock(");
1929 __print_lock_name(tgt, target);
1930 printk(KERN_CONT ");\n");
1931 if (src_read != 0)
1932 printk(" rlock(");
1933 else if (src->sync)
1934 printk(" sync(");
1935 else
1936 printk(" lock(");
1937 __print_lock_name(src, source);
1938 printk(KERN_CONT ");\n");
1939 printk("\n *** DEADLOCK ***\n\n");
1940 }
1941
1942 /*
1943 * When a circular dependency is detected, print the
1944 * header first:
1945 */
1946 static noinline void
print_circular_bug_header(struct lock_list * entry,unsigned int depth,struct held_lock * check_src,struct held_lock * check_tgt)1947 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1948 struct held_lock *check_src,
1949 struct held_lock *check_tgt)
1950 {
1951 struct task_struct *curr = current;
1952
1953 if (debug_locks_silent)
1954 return;
1955
1956 pr_warn("\n");
1957 pr_warn("======================================================\n");
1958 pr_warn("WARNING: possible circular locking dependency detected\n");
1959 print_kernel_ident();
1960 pr_warn("------------------------------------------------------\n");
1961 pr_warn("%s/%d is trying to acquire lock:\n",
1962 curr->comm, task_pid_nr(curr));
1963 print_lock(check_src);
1964
1965 pr_warn("\nbut task is already holding lock:\n");
1966
1967 print_lock(check_tgt);
1968 pr_warn("\nwhich lock already depends on the new lock.\n\n");
1969 pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1970
1971 print_circular_bug_entry(entry, depth);
1972 }
1973
1974 /*
1975 * We are about to add A -> B into the dependency graph, and in __bfs() a
1976 * strong dependency path A -> .. -> B is found: hlock_class equals
1977 * entry->class.
1978 *
1979 * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
1980 * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
1981 * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
1982 * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
1983 * dependency graph, as any strong path ..-> A -> B ->.. we can get with
1984 * having dependency A -> B, we could already get a equivalent path ..-> A ->
1985 * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant.
1986 *
1987 * We need to make sure both the start and the end of A -> .. -> B is not
1988 * weaker than A -> B. For the start part, please see the comment in
1989 * check_redundant(). For the end part, we need:
1990 *
1991 * Either
1992 *
1993 * a) A -> B is -(*R)-> (everything is not weaker than that)
1994 *
1995 * or
1996 *
1997 * b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
1998 *
1999 */
hlock_equal(struct lock_list * entry,void * data)2000 static inline bool hlock_equal(struct lock_list *entry, void *data)
2001 {
2002 struct held_lock *hlock = (struct held_lock *)data;
2003
2004 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
2005 (hlock->read == 2 || /* A -> B is -(*R)-> */
2006 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
2007 }
2008
2009 /*
2010 * We are about to add B -> A into the dependency graph, and in __bfs() a
2011 * strong dependency path A -> .. -> B is found: hlock_class equals
2012 * entry->class.
2013 *
2014 * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
2015 * dependency cycle, that means:
2016 *
2017 * Either
2018 *
2019 * a) B -> A is -(E*)->
2020 *
2021 * or
2022 *
2023 * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
2024 *
2025 * as then we don't have -(*R)-> -(S*)-> in the cycle.
2026 */
hlock_conflict(struct lock_list * entry,void * data)2027 static inline bool hlock_conflict(struct lock_list *entry, void *data)
2028 {
2029 struct held_lock *hlock = (struct held_lock *)data;
2030
2031 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
2032 (hlock->read == 0 || /* B -> A is -(E*)-> */
2033 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
2034 }
2035
print_circular_bug(struct lock_list * this,struct lock_list * target,struct held_lock * check_src,struct held_lock * check_tgt)2036 static noinline void print_circular_bug(struct lock_list *this,
2037 struct lock_list *target,
2038 struct held_lock *check_src,
2039 struct held_lock *check_tgt)
2040 {
2041 struct task_struct *curr = current;
2042 struct lock_list *parent;
2043 struct lock_list *first_parent;
2044 int depth;
2045
2046 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2047 return;
2048
2049 this->trace = save_trace();
2050 if (!this->trace)
2051 return;
2052
2053 depth = get_lock_depth(target);
2054
2055 nbcon_cpu_emergency_enter();
2056
2057 print_circular_bug_header(target, depth, check_src, check_tgt);
2058
2059 parent = get_lock_parent(target);
2060 first_parent = parent;
2061
2062 while (parent) {
2063 print_circular_bug_entry(parent, --depth);
2064 parent = get_lock_parent(parent);
2065 }
2066
2067 printk("\nother info that might help us debug this:\n\n");
2068 print_circular_lock_scenario(check_src, check_tgt,
2069 first_parent);
2070
2071 lockdep_print_held_locks(curr);
2072
2073 printk("\nstack backtrace:\n");
2074 dump_stack();
2075
2076 nbcon_cpu_emergency_exit();
2077 }
2078
print_bfs_bug(int ret)2079 static noinline void print_bfs_bug(int ret)
2080 {
2081 if (!debug_locks_off_graph_unlock())
2082 return;
2083
2084 /*
2085 * Breadth-first-search failed, graph got corrupted?
2086 */
2087 WARN(1, "lockdep bfs error:%d\n", ret);
2088 }
2089
noop_count(struct lock_list * entry,void * data)2090 static bool noop_count(struct lock_list *entry, void *data)
2091 {
2092 (*(unsigned long *)data)++;
2093 return false;
2094 }
2095
__lockdep_count_forward_deps(struct lock_list * this)2096 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
2097 {
2098 unsigned long count = 0;
2099 struct lock_list *target_entry;
2100
2101 __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
2102
2103 return count;
2104 }
lockdep_count_forward_deps(struct lock_class * class)2105 unsigned long lockdep_count_forward_deps(struct lock_class *class)
2106 {
2107 unsigned long ret, flags;
2108 struct lock_list this;
2109
2110 __bfs_init_root(&this, class);
2111
2112 raw_local_irq_save(flags);
2113 lockdep_lock();
2114 ret = __lockdep_count_forward_deps(&this);
2115 lockdep_unlock();
2116 raw_local_irq_restore(flags);
2117
2118 return ret;
2119 }
2120
__lockdep_count_backward_deps(struct lock_list * this)2121 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
2122 {
2123 unsigned long count = 0;
2124 struct lock_list *target_entry;
2125
2126 __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
2127
2128 return count;
2129 }
2130
lockdep_count_backward_deps(struct lock_class * class)2131 unsigned long lockdep_count_backward_deps(struct lock_class *class)
2132 {
2133 unsigned long ret, flags;
2134 struct lock_list this;
2135
2136 __bfs_init_root(&this, class);
2137
2138 raw_local_irq_save(flags);
2139 lockdep_lock();
2140 ret = __lockdep_count_backward_deps(&this);
2141 lockdep_unlock();
2142 raw_local_irq_restore(flags);
2143
2144 return ret;
2145 }
2146
2147 /*
2148 * Check that the dependency graph starting at <src> can lead to
2149 * <target> or not.
2150 */
2151 static noinline enum bfs_result
check_path(struct held_lock * target,struct lock_list * src_entry,bool (* match)(struct lock_list * entry,void * data),bool (* skip)(struct lock_list * entry,void * data),struct lock_list ** target_entry)2152 check_path(struct held_lock *target, struct lock_list *src_entry,
2153 bool (*match)(struct lock_list *entry, void *data),
2154 bool (*skip)(struct lock_list *entry, void *data),
2155 struct lock_list **target_entry)
2156 {
2157 enum bfs_result ret;
2158
2159 ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
2160
2161 if (unlikely(bfs_error(ret)))
2162 print_bfs_bug(ret);
2163
2164 return ret;
2165 }
2166
2167 static void print_deadlock_bug(struct task_struct *, struct held_lock *, struct held_lock *);
2168
2169 /*
2170 * Prove that the dependency graph starting at <src> can not
2171 * lead to <target>. If it can, there is a circle when adding
2172 * <target> -> <src> dependency.
2173 *
2174 * Print an error and return BFS_RMATCH if it does.
2175 */
2176 static noinline enum bfs_result
check_noncircular(struct held_lock * src,struct held_lock * target,struct lock_trace ** const trace)2177 check_noncircular(struct held_lock *src, struct held_lock *target,
2178 struct lock_trace **const trace)
2179 {
2180 enum bfs_result ret;
2181 struct lock_list *target_entry;
2182 struct lock_list src_entry;
2183
2184 bfs_init_root(&src_entry, src);
2185
2186 debug_atomic_inc(nr_cyclic_checks);
2187
2188 ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
2189
2190 if (unlikely(ret == BFS_RMATCH)) {
2191 if (!*trace) {
2192 /*
2193 * If save_trace fails here, the printing might
2194 * trigger a WARN but because of the !nr_entries it
2195 * should not do bad things.
2196 */
2197 *trace = save_trace();
2198 }
2199
2200 if (src->class_idx == target->class_idx)
2201 print_deadlock_bug(current, src, target);
2202 else
2203 print_circular_bug(&src_entry, target_entry, src, target);
2204 }
2205
2206 return ret;
2207 }
2208
2209 #ifdef CONFIG_TRACE_IRQFLAGS
2210
2211 /*
2212 * Forwards and backwards subgraph searching, for the purposes of
2213 * proving that two subgraphs can be connected by a new dependency
2214 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
2215 *
2216 * A irq safe->unsafe deadlock happens with the following conditions:
2217 *
2218 * 1) We have a strong dependency path A -> ... -> B
2219 *
2220 * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
2221 * irq can create a new dependency B -> A (consider the case that a holder
2222 * of B gets interrupted by an irq whose handler will try to acquire A).
2223 *
2224 * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
2225 * strong circle:
2226 *
2227 * For the usage bits of B:
2228 * a) if A -> B is -(*N)->, then B -> A could be any type, so any
2229 * ENABLED_IRQ usage suffices.
2230 * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
2231 * ENABLED_IRQ_*_READ usage suffices.
2232 *
2233 * For the usage bits of A:
2234 * c) if A -> B is -(E*)->, then B -> A could be any type, so any
2235 * USED_IN_IRQ usage suffices.
2236 * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
2237 * USED_IN_IRQ_*_READ usage suffices.
2238 */
2239
2240 /*
2241 * There is a strong dependency path in the dependency graph: A -> B, and now
2242 * we need to decide which usage bit of A should be accumulated to detect
2243 * safe->unsafe bugs.
2244 *
2245 * Note that usage_accumulate() is used in backwards search, so ->only_xr
2246 * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
2247 *
2248 * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
2249 * path, any usage of A should be considered. Otherwise, we should only
2250 * consider _READ usage.
2251 */
usage_accumulate(struct lock_list * entry,void * mask)2252 static inline bool usage_accumulate(struct lock_list *entry, void *mask)
2253 {
2254 if (!entry->only_xr)
2255 *(unsigned long *)mask |= entry->class->usage_mask;
2256 else /* Mask out _READ usage bits */
2257 *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
2258
2259 return false;
2260 }
2261
2262 /*
2263 * There is a strong dependency path in the dependency graph: A -> B, and now
2264 * we need to decide which usage bit of B conflicts with the usage bits of A,
2265 * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
2266 *
2267 * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
2268 * path, any usage of B should be considered. Otherwise, we should only
2269 * consider _READ usage.
2270 */
usage_match(struct lock_list * entry,void * mask)2271 static inline bool usage_match(struct lock_list *entry, void *mask)
2272 {
2273 if (!entry->only_xr)
2274 return !!(entry->class->usage_mask & *(unsigned long *)mask);
2275 else /* Mask out _READ usage bits */
2276 return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
2277 }
2278
usage_skip(struct lock_list * entry,void * mask)2279 static inline bool usage_skip(struct lock_list *entry, void *mask)
2280 {
2281 if (entry->class->lock_type == LD_LOCK_NORMAL)
2282 return false;
2283
2284 /*
2285 * Skip local_lock() for irq inversion detection.
2286 *
2287 * For !RT, local_lock() is not a real lock, so it won't carry any
2288 * dependency.
2289 *
2290 * For RT, an irq inversion happens when we have lock A and B, and on
2291 * some CPU we can have:
2292 *
2293 * lock(A);
2294 * <interrupted>
2295 * lock(B);
2296 *
2297 * where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
2298 *
2299 * Now we prove local_lock() cannot exist in that dependency. First we
2300 * have the observation for any lock chain L1 -> ... -> Ln, for any
2301 * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
2302 * wait context check will complain. And since B is not a sleep lock,
2303 * therefore B.inner_wait_type >= 2, and since the inner_wait_type of
2304 * local_lock() is 3, which is greater than 2, therefore there is no
2305 * way the local_lock() exists in the dependency B -> ... -> A.
2306 *
2307 * As a result, we will skip local_lock(), when we search for irq
2308 * inversion bugs.
2309 */
2310 if (entry->class->lock_type == LD_LOCK_PERCPU &&
2311 DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
2312 return false;
2313
2314 /*
2315 * Skip WAIT_OVERRIDE for irq inversion detection -- it's not actually
2316 * a lock and only used to override the wait_type.
2317 */
2318
2319 return true;
2320 }
2321
2322 /*
2323 * Find a node in the forwards-direction dependency sub-graph starting
2324 * at @root->class that matches @bit.
2325 *
2326 * Return BFS_MATCH if such a node exists in the subgraph, and put that node
2327 * into *@target_entry.
2328 */
2329 static enum bfs_result
find_usage_forwards(struct lock_list * root,unsigned long usage_mask,struct lock_list ** target_entry)2330 find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
2331 struct lock_list **target_entry)
2332 {
2333 enum bfs_result result;
2334
2335 debug_atomic_inc(nr_find_usage_forwards_checks);
2336
2337 result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2338
2339 return result;
2340 }
2341
2342 /*
2343 * Find a node in the backwards-direction dependency sub-graph starting
2344 * at @root->class that matches @bit.
2345 */
2346 static enum bfs_result
find_usage_backwards(struct lock_list * root,unsigned long usage_mask,struct lock_list ** target_entry)2347 find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
2348 struct lock_list **target_entry)
2349 {
2350 enum bfs_result result;
2351
2352 debug_atomic_inc(nr_find_usage_backwards_checks);
2353
2354 result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2355
2356 return result;
2357 }
2358
print_lock_class_header(struct lock_class * class,int depth)2359 static void print_lock_class_header(struct lock_class *class, int depth)
2360 {
2361 int bit;
2362
2363 printk("%*s->", depth, "");
2364 print_lock_name(NULL, class);
2365 #ifdef CONFIG_DEBUG_LOCKDEP
2366 printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
2367 #endif
2368 printk(KERN_CONT " {\n");
2369
2370 for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
2371 if (class->usage_mask & (1 << bit)) {
2372 int len = depth;
2373
2374 len += printk("%*s %s", depth, "", usage_str[bit]);
2375 len += printk(KERN_CONT " at:\n");
2376 print_lock_trace(class->usage_traces[bit], len);
2377 }
2378 }
2379 printk("%*s }\n", depth, "");
2380
2381 printk("%*s ... key at: [<%px>] %pS\n",
2382 depth, "", class->key, class->key);
2383 }
2384
2385 /*
2386 * Dependency path printing:
2387 *
2388 * After BFS we get a lock dependency path (linked via ->parent of lock_list),
2389 * printing out each lock in the dependency path will help on understanding how
2390 * the deadlock could happen. Here are some details about dependency path
2391 * printing:
2392 *
2393 * 1) A lock_list can be either forwards or backwards for a lock dependency,
2394 * for a lock dependency A -> B, there are two lock_lists:
2395 *
2396 * a) lock_list in the ->locks_after list of A, whose ->class is B and
2397 * ->links_to is A. In this case, we can say the lock_list is
2398 * "A -> B" (forwards case).
2399 *
2400 * b) lock_list in the ->locks_before list of B, whose ->class is A
2401 * and ->links_to is B. In this case, we can say the lock_list is
2402 * "B <- A" (bacwards case).
2403 *
2404 * The ->trace of both a) and b) point to the call trace where B was
2405 * acquired with A held.
2406 *
2407 * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't
2408 * represent a certain lock dependency, it only provides an initial entry
2409 * for BFS. For example, BFS may introduce a "helper" lock_list whose
2410 * ->class is A, as a result BFS will search all dependencies starting with
2411 * A, e.g. A -> B or A -> C.
2412 *
2413 * The notation of a forwards helper lock_list is like "-> A", which means
2414 * we should search the forwards dependencies starting with "A", e.g A -> B
2415 * or A -> C.
2416 *
2417 * The notation of a bacwards helper lock_list is like "<- B", which means
2418 * we should search the backwards dependencies ending with "B", e.g.
2419 * B <- A or B <- C.
2420 */
2421
2422 /*
2423 * printk the shortest lock dependencies from @root to @leaf in reverse order.
2424 *
2425 * We have a lock dependency path as follow:
2426 *
2427 * @root @leaf
2428 * | |
2429 * V V
2430 * ->parent ->parent
2431 * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list |
2432 * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln|
2433 *
2434 * , so it's natural that we start from @leaf and print every ->class and
2435 * ->trace until we reach the @root.
2436 */
2437 static void __used
print_shortest_lock_dependencies(struct lock_list * leaf,struct lock_list * root)2438 print_shortest_lock_dependencies(struct lock_list *leaf,
2439 struct lock_list *root)
2440 {
2441 struct lock_list *entry = leaf;
2442 int depth;
2443
2444 /*compute depth from generated tree by BFS*/
2445 depth = get_lock_depth(leaf);
2446
2447 do {
2448 print_lock_class_header(entry->class, depth);
2449 printk("%*s ... acquired at:\n", depth, "");
2450 print_lock_trace(entry->trace, 2);
2451 printk("\n");
2452
2453 if (depth == 0 && (entry != root)) {
2454 printk("lockdep:%s bad path found in chain graph\n", __func__);
2455 break;
2456 }
2457
2458 entry = get_lock_parent(entry);
2459 depth--;
2460 } while (entry && (depth >= 0));
2461 }
2462
2463 /*
2464 * printk the shortest lock dependencies from @leaf to @root.
2465 *
2466 * We have a lock dependency path (from a backwards search) as follow:
2467 *
2468 * @leaf @root
2469 * | |
2470 * V V
2471 * ->parent ->parent
2472 * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list |
2473 * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln |
2474 *
2475 * , so when we iterate from @leaf to @root, we actually print the lock
2476 * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
2477 *
2478 * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
2479 * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
2480 * trace of L1 in the dependency path, which is alright, because most of the
2481 * time we can figure out where L1 is held from the call trace of L2.
2482 */
2483 static void __used
print_shortest_lock_dependencies_backwards(struct lock_list * leaf,struct lock_list * root)2484 print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
2485 struct lock_list *root)
2486 {
2487 struct lock_list *entry = leaf;
2488 const struct lock_trace *trace = NULL;
2489 int depth;
2490
2491 /*compute depth from generated tree by BFS*/
2492 depth = get_lock_depth(leaf);
2493
2494 do {
2495 print_lock_class_header(entry->class, depth);
2496 if (trace) {
2497 printk("%*s ... acquired at:\n", depth, "");
2498 print_lock_trace(trace, 2);
2499 printk("\n");
2500 }
2501
2502 /*
2503 * Record the pointer to the trace for the next lock_list
2504 * entry, see the comments for the function.
2505 */
2506 trace = entry->trace;
2507
2508 if (depth == 0 && (entry != root)) {
2509 printk("lockdep:%s bad path found in chain graph\n", __func__);
2510 break;
2511 }
2512
2513 entry = get_lock_parent(entry);
2514 depth--;
2515 } while (entry && (depth >= 0));
2516 }
2517
2518 static void
print_irq_lock_scenario(struct lock_list * safe_entry,struct lock_list * unsafe_entry,struct lock_class * prev_class,struct lock_class * next_class)2519 print_irq_lock_scenario(struct lock_list *safe_entry,
2520 struct lock_list *unsafe_entry,
2521 struct lock_class *prev_class,
2522 struct lock_class *next_class)
2523 {
2524 struct lock_class *safe_class = safe_entry->class;
2525 struct lock_class *unsafe_class = unsafe_entry->class;
2526 struct lock_class *middle_class = prev_class;
2527
2528 if (middle_class == safe_class)
2529 middle_class = next_class;
2530
2531 /*
2532 * A direct locking problem where unsafe_class lock is taken
2533 * directly by safe_class lock, then all we need to show
2534 * is the deadlock scenario, as it is obvious that the
2535 * unsafe lock is taken under the safe lock.
2536 *
2537 * But if there is a chain instead, where the safe lock takes
2538 * an intermediate lock (middle_class) where this lock is
2539 * not the same as the safe lock, then the lock chain is
2540 * used to describe the problem. Otherwise we would need
2541 * to show a different CPU case for each link in the chain
2542 * from the safe_class lock to the unsafe_class lock.
2543 */
2544 if (middle_class != unsafe_class) {
2545 printk("Chain exists of:\n ");
2546 __print_lock_name(NULL, safe_class);
2547 printk(KERN_CONT " --> ");
2548 __print_lock_name(NULL, middle_class);
2549 printk(KERN_CONT " --> ");
2550 __print_lock_name(NULL, unsafe_class);
2551 printk(KERN_CONT "\n\n");
2552 }
2553
2554 printk(" Possible interrupt unsafe locking scenario:\n\n");
2555 printk(" CPU0 CPU1\n");
2556 printk(" ---- ----\n");
2557 printk(" lock(");
2558 __print_lock_name(NULL, unsafe_class);
2559 printk(KERN_CONT ");\n");
2560 printk(" local_irq_disable();\n");
2561 printk(" lock(");
2562 __print_lock_name(NULL, safe_class);
2563 printk(KERN_CONT ");\n");
2564 printk(" lock(");
2565 __print_lock_name(NULL, middle_class);
2566 printk(KERN_CONT ");\n");
2567 printk(" <Interrupt>\n");
2568 printk(" lock(");
2569 __print_lock_name(NULL, safe_class);
2570 printk(KERN_CONT ");\n");
2571 printk("\n *** DEADLOCK ***\n\n");
2572 }
2573
2574 static void
print_bad_irq_dependency(struct task_struct * curr,struct lock_list * prev_root,struct lock_list * next_root,struct lock_list * backwards_entry,struct lock_list * forwards_entry,struct held_lock * prev,struct held_lock * next,enum lock_usage_bit bit1,enum lock_usage_bit bit2,const char * irqclass)2575 print_bad_irq_dependency(struct task_struct *curr,
2576 struct lock_list *prev_root,
2577 struct lock_list *next_root,
2578 struct lock_list *backwards_entry,
2579 struct lock_list *forwards_entry,
2580 struct held_lock *prev,
2581 struct held_lock *next,
2582 enum lock_usage_bit bit1,
2583 enum lock_usage_bit bit2,
2584 const char *irqclass)
2585 {
2586 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2587 return;
2588
2589 nbcon_cpu_emergency_enter();
2590
2591 pr_warn("\n");
2592 pr_warn("=====================================================\n");
2593 pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2594 irqclass, irqclass);
2595 print_kernel_ident();
2596 pr_warn("-----------------------------------------------------\n");
2597 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2598 curr->comm, task_pid_nr(curr),
2599 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
2600 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2601 lockdep_hardirqs_enabled(),
2602 curr->softirqs_enabled);
2603 print_lock(next);
2604
2605 pr_warn("\nand this task is already holding:\n");
2606 print_lock(prev);
2607 pr_warn("which would create a new lock dependency:\n");
2608 print_lock_name(prev, hlock_class(prev));
2609 pr_cont(" ->");
2610 print_lock_name(next, hlock_class(next));
2611 pr_cont("\n");
2612
2613 pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2614 irqclass);
2615 print_lock_name(NULL, backwards_entry->class);
2616 pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2617
2618 print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2619
2620 pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2621 print_lock_name(NULL, forwards_entry->class);
2622 pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2623 pr_warn("...");
2624
2625 print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2626
2627 pr_warn("\nother info that might help us debug this:\n\n");
2628 print_irq_lock_scenario(backwards_entry, forwards_entry,
2629 hlock_class(prev), hlock_class(next));
2630
2631 lockdep_print_held_locks(curr);
2632
2633 pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2634 print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
2635
2636 pr_warn("\nthe dependencies between the lock to be acquired");
2637 pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2638 next_root->trace = save_trace();
2639 if (!next_root->trace)
2640 goto out;
2641 print_shortest_lock_dependencies(forwards_entry, next_root);
2642
2643 pr_warn("\nstack backtrace:\n");
2644 dump_stack();
2645 out:
2646 nbcon_cpu_emergency_exit();
2647 }
2648
2649 static const char *state_names[] = {
2650 #define LOCKDEP_STATE(__STATE) \
2651 __stringify(__STATE),
2652 #include "lockdep_states.h"
2653 #undef LOCKDEP_STATE
2654 };
2655
2656 static const char *state_rnames[] = {
2657 #define LOCKDEP_STATE(__STATE) \
2658 __stringify(__STATE)"-READ",
2659 #include "lockdep_states.h"
2660 #undef LOCKDEP_STATE
2661 };
2662
state_name(enum lock_usage_bit bit)2663 static inline const char *state_name(enum lock_usage_bit bit)
2664 {
2665 if (bit & LOCK_USAGE_READ_MASK)
2666 return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2667 else
2668 return state_names[bit >> LOCK_USAGE_DIR_MASK];
2669 }
2670
2671 /*
2672 * The bit number is encoded like:
2673 *
2674 * bit0: 0 exclusive, 1 read lock
2675 * bit1: 0 used in irq, 1 irq enabled
2676 * bit2-n: state
2677 */
exclusive_bit(int new_bit)2678 static int exclusive_bit(int new_bit)
2679 {
2680 int state = new_bit & LOCK_USAGE_STATE_MASK;
2681 int dir = new_bit & LOCK_USAGE_DIR_MASK;
2682
2683 /*
2684 * keep state, bit flip the direction and strip read.
2685 */
2686 return state | (dir ^ LOCK_USAGE_DIR_MASK);
2687 }
2688
2689 /*
2690 * Observe that when given a bitmask where each bitnr is encoded as above, a
2691 * right shift of the mask transforms the individual bitnrs as -1 and
2692 * conversely, a left shift transforms into +1 for the individual bitnrs.
2693 *
2694 * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2695 * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2696 * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2697 *
2698 * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2699 *
2700 * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2701 * all bits set) and recompose with bitnr1 flipped.
2702 */
invert_dir_mask(unsigned long mask)2703 static unsigned long invert_dir_mask(unsigned long mask)
2704 {
2705 unsigned long excl = 0;
2706
2707 /* Invert dir */
2708 excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2709 excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2710
2711 return excl;
2712 }
2713
2714 /*
2715 * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
2716 * usage may cause deadlock too, for example:
2717 *
2718 * P1 P2
2719 * <irq disabled>
2720 * write_lock(l1); <irq enabled>
2721 * read_lock(l2);
2722 * write_lock(l2);
2723 * <in irq>
2724 * read_lock(l1);
2725 *
2726 * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
2727 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
2728 * deadlock.
2729 *
2730 * In fact, all of the following cases may cause deadlocks:
2731 *
2732 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
2733 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
2734 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
2735 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
2736 *
2737 * As a result, to calculate the "exclusive mask", first we invert the
2738 * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
2739 * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
2740 * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
2741 */
exclusive_mask(unsigned long mask)2742 static unsigned long exclusive_mask(unsigned long mask)
2743 {
2744 unsigned long excl = invert_dir_mask(mask);
2745
2746 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2747 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2748
2749 return excl;
2750 }
2751
2752 /*
2753 * Retrieve the _possible_ original mask to which @mask is
2754 * exclusive. Ie: this is the opposite of exclusive_mask().
2755 * Note that 2 possible original bits can match an exclusive
2756 * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2757 * cleared. So both are returned for each exclusive bit.
2758 */
original_mask(unsigned long mask)2759 static unsigned long original_mask(unsigned long mask)
2760 {
2761 unsigned long excl = invert_dir_mask(mask);
2762
2763 /* Include read in existing usages */
2764 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2765 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2766
2767 return excl;
2768 }
2769
2770 /*
2771 * Find the first pair of bit match between an original
2772 * usage mask and an exclusive usage mask.
2773 */
find_exclusive_match(unsigned long mask,unsigned long excl_mask,enum lock_usage_bit * bitp,enum lock_usage_bit * excl_bitp)2774 static int find_exclusive_match(unsigned long mask,
2775 unsigned long excl_mask,
2776 enum lock_usage_bit *bitp,
2777 enum lock_usage_bit *excl_bitp)
2778 {
2779 int bit, excl, excl_read;
2780
2781 for_each_set_bit(bit, &mask, LOCK_USED) {
2782 /*
2783 * exclusive_bit() strips the read bit, however,
2784 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
2785 * to search excl | LOCK_USAGE_READ_MASK as well.
2786 */
2787 excl = exclusive_bit(bit);
2788 excl_read = excl | LOCK_USAGE_READ_MASK;
2789 if (excl_mask & lock_flag(excl)) {
2790 *bitp = bit;
2791 *excl_bitp = excl;
2792 return 0;
2793 } else if (excl_mask & lock_flag(excl_read)) {
2794 *bitp = bit;
2795 *excl_bitp = excl_read;
2796 return 0;
2797 }
2798 }
2799 return -1;
2800 }
2801
2802 /*
2803 * Prove that the new dependency does not connect a hardirq-safe(-read)
2804 * lock with a hardirq-unsafe lock - to achieve this we search
2805 * the backwards-subgraph starting at <prev>, and the
2806 * forwards-subgraph starting at <next>:
2807 */
check_irq_usage(struct task_struct * curr,struct held_lock * prev,struct held_lock * next)2808 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2809 struct held_lock *next)
2810 {
2811 unsigned long usage_mask = 0, forward_mask, backward_mask;
2812 enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2813 struct lock_list *target_entry1;
2814 struct lock_list *target_entry;
2815 struct lock_list this, that;
2816 enum bfs_result ret;
2817
2818 /*
2819 * Step 1: gather all hard/soft IRQs usages backward in an
2820 * accumulated usage mask.
2821 */
2822 bfs_init_rootb(&this, prev);
2823
2824 ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
2825 if (bfs_error(ret)) {
2826 print_bfs_bug(ret);
2827 return 0;
2828 }
2829
2830 usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2831 if (!usage_mask)
2832 return 1;
2833
2834 /*
2835 * Step 2: find exclusive uses forward that match the previous
2836 * backward accumulated mask.
2837 */
2838 forward_mask = exclusive_mask(usage_mask);
2839
2840 bfs_init_root(&that, next);
2841
2842 ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2843 if (bfs_error(ret)) {
2844 print_bfs_bug(ret);
2845 return 0;
2846 }
2847 if (ret == BFS_RNOMATCH)
2848 return 1;
2849
2850 /*
2851 * Step 3: we found a bad match! Now retrieve a lock from the backward
2852 * list whose usage mask matches the exclusive usage mask from the
2853 * lock found on the forward list.
2854 *
2855 * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
2856 * the follow case:
2857 *
2858 * When trying to add A -> B to the graph, we find that there is a
2859 * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
2860 * that B -> ... -> M. However M is **softirq-safe**, if we use exact
2861 * invert bits of M's usage_mask, we will find another lock N that is
2862 * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
2863 * cause a inversion deadlock.
2864 */
2865 backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
2866
2867 ret = find_usage_backwards(&this, backward_mask, &target_entry);
2868 if (bfs_error(ret)) {
2869 print_bfs_bug(ret);
2870 return 0;
2871 }
2872 if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
2873 return 1;
2874
2875 /*
2876 * Step 4: narrow down to a pair of incompatible usage bits
2877 * and report it.
2878 */
2879 ret = find_exclusive_match(target_entry->class->usage_mask,
2880 target_entry1->class->usage_mask,
2881 &backward_bit, &forward_bit);
2882 if (DEBUG_LOCKS_WARN_ON(ret == -1))
2883 return 1;
2884
2885 print_bad_irq_dependency(curr, &this, &that,
2886 target_entry, target_entry1,
2887 prev, next,
2888 backward_bit, forward_bit,
2889 state_name(backward_bit));
2890
2891 return 0;
2892 }
2893
2894 #else
2895
check_irq_usage(struct task_struct * curr,struct held_lock * prev,struct held_lock * next)2896 static inline int check_irq_usage(struct task_struct *curr,
2897 struct held_lock *prev, struct held_lock *next)
2898 {
2899 return 1;
2900 }
2901
usage_skip(struct lock_list * entry,void * mask)2902 static inline bool usage_skip(struct lock_list *entry, void *mask)
2903 {
2904 return false;
2905 }
2906
2907 #endif /* CONFIG_TRACE_IRQFLAGS */
2908
2909 #ifdef CONFIG_LOCKDEP_SMALL
2910 /*
2911 * Check that the dependency graph starting at <src> can lead to
2912 * <target> or not. If it can, <src> -> <target> dependency is already
2913 * in the graph.
2914 *
2915 * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if
2916 * any error appears in the bfs search.
2917 */
2918 static noinline enum bfs_result
check_redundant(struct held_lock * src,struct held_lock * target)2919 check_redundant(struct held_lock *src, struct held_lock *target)
2920 {
2921 enum bfs_result ret;
2922 struct lock_list *target_entry;
2923 struct lock_list src_entry;
2924
2925 bfs_init_root(&src_entry, src);
2926 /*
2927 * Special setup for check_redundant().
2928 *
2929 * To report redundant, we need to find a strong dependency path that
2930 * is equal to or stronger than <src> -> <target>. So if <src> is E,
2931 * we need to let __bfs() only search for a path starting at a -(E*)->,
2932 * we achieve this by setting the initial node's ->only_xr to true in
2933 * that case. And if <prev> is S, we set initial ->only_xr to false
2934 * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
2935 */
2936 src_entry.only_xr = src->read == 0;
2937
2938 debug_atomic_inc(nr_redundant_checks);
2939
2940 /*
2941 * Note: we skip local_lock() for redundant check, because as the
2942 * comment in usage_skip(), A -> local_lock() -> B and A -> B are not
2943 * the same.
2944 */
2945 ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
2946
2947 if (ret == BFS_RMATCH)
2948 debug_atomic_inc(nr_redundant);
2949
2950 return ret;
2951 }
2952
2953 #else
2954
2955 static inline enum bfs_result
check_redundant(struct held_lock * src,struct held_lock * target)2956 check_redundant(struct held_lock *src, struct held_lock *target)
2957 {
2958 return BFS_RNOMATCH;
2959 }
2960
2961 #endif
2962
inc_chains(int irq_context)2963 static void inc_chains(int irq_context)
2964 {
2965 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2966 nr_hardirq_chains++;
2967 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2968 nr_softirq_chains++;
2969 else
2970 nr_process_chains++;
2971 }
2972
dec_chains(int irq_context)2973 static void dec_chains(int irq_context)
2974 {
2975 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2976 nr_hardirq_chains--;
2977 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2978 nr_softirq_chains--;
2979 else
2980 nr_process_chains--;
2981 }
2982
2983 static void
print_deadlock_scenario(struct held_lock * nxt,struct held_lock * prv)2984 print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2985 {
2986 struct lock_class *next = hlock_class(nxt);
2987 struct lock_class *prev = hlock_class(prv);
2988
2989 printk(" Possible unsafe locking scenario:\n\n");
2990 printk(" CPU0\n");
2991 printk(" ----\n");
2992 printk(" lock(");
2993 __print_lock_name(prv, prev);
2994 printk(KERN_CONT ");\n");
2995 printk(" lock(");
2996 __print_lock_name(nxt, next);
2997 printk(KERN_CONT ");\n");
2998 printk("\n *** DEADLOCK ***\n\n");
2999 printk(" May be due to missing lock nesting notation\n\n");
3000 }
3001
3002 static void
print_deadlock_bug(struct task_struct * curr,struct held_lock * prev,struct held_lock * next)3003 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
3004 struct held_lock *next)
3005 {
3006 struct lock_class *class = hlock_class(prev);
3007
3008 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3009 return;
3010
3011 nbcon_cpu_emergency_enter();
3012
3013 pr_warn("\n");
3014 pr_warn("============================================\n");
3015 pr_warn("WARNING: possible recursive locking detected\n");
3016 print_kernel_ident();
3017 pr_warn("--------------------------------------------\n");
3018 pr_warn("%s/%d is trying to acquire lock:\n",
3019 curr->comm, task_pid_nr(curr));
3020 print_lock(next);
3021 pr_warn("\nbut task is already holding lock:\n");
3022 print_lock(prev);
3023
3024 if (class->cmp_fn) {
3025 pr_warn("and the lock comparison function returns %i:\n",
3026 class->cmp_fn(prev->instance, next->instance));
3027 }
3028
3029 pr_warn("\nother info that might help us debug this:\n");
3030 print_deadlock_scenario(next, prev);
3031 lockdep_print_held_locks(curr);
3032
3033 pr_warn("\nstack backtrace:\n");
3034 dump_stack();
3035
3036 nbcon_cpu_emergency_exit();
3037 }
3038
3039 /*
3040 * Check whether we are holding such a class already.
3041 *
3042 * (Note that this has to be done separately, because the graph cannot
3043 * detect such classes of deadlocks.)
3044 *
3045 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
3046 * lock class is held but nest_lock is also held, i.e. we rely on the
3047 * nest_lock to avoid the deadlock.
3048 */
3049 static int
check_deadlock(struct task_struct * curr,struct held_lock * next)3050 check_deadlock(struct task_struct *curr, struct held_lock *next)
3051 {
3052 struct lock_class *class;
3053 struct held_lock *prev;
3054 struct held_lock *nest = NULL;
3055 int i;
3056
3057 for (i = 0; i < curr->lockdep_depth; i++) {
3058 prev = curr->held_locks + i;
3059
3060 if (prev->instance == next->nest_lock)
3061 nest = prev;
3062
3063 if (hlock_class(prev) != hlock_class(next))
3064 continue;
3065
3066 /*
3067 * Allow read-after-read recursion of the same
3068 * lock class (i.e. read_lock(lock)+read_lock(lock)):
3069 */
3070 if ((next->read == 2) && prev->read)
3071 continue;
3072
3073 class = hlock_class(prev);
3074
3075 if (class->cmp_fn &&
3076 class->cmp_fn(prev->instance, next->instance) < 0)
3077 continue;
3078
3079 /*
3080 * We're holding the nest_lock, which serializes this lock's
3081 * nesting behaviour.
3082 */
3083 if (nest)
3084 return 2;
3085
3086 print_deadlock_bug(curr, prev, next);
3087 return 0;
3088 }
3089 return 1;
3090 }
3091
3092 /*
3093 * There was a chain-cache miss, and we are about to add a new dependency
3094 * to a previous lock. We validate the following rules:
3095 *
3096 * - would the adding of the <prev> -> <next> dependency create a
3097 * circular dependency in the graph? [== circular deadlock]
3098 *
3099 * - does the new prev->next dependency connect any hardirq-safe lock
3100 * (in the full backwards-subgraph starting at <prev>) with any
3101 * hardirq-unsafe lock (in the full forwards-subgraph starting at
3102 * <next>)? [== illegal lock inversion with hardirq contexts]
3103 *
3104 * - does the new prev->next dependency connect any softirq-safe lock
3105 * (in the full backwards-subgraph starting at <prev>) with any
3106 * softirq-unsafe lock (in the full forwards-subgraph starting at
3107 * <next>)? [== illegal lock inversion with softirq contexts]
3108 *
3109 * any of these scenarios could lead to a deadlock.
3110 *
3111 * Then if all the validations pass, we add the forwards and backwards
3112 * dependency.
3113 */
3114 static int
check_prev_add(struct task_struct * curr,struct held_lock * prev,struct held_lock * next,u16 distance,struct lock_trace ** const trace)3115 check_prev_add(struct task_struct *curr, struct held_lock *prev,
3116 struct held_lock *next, u16 distance,
3117 struct lock_trace **const trace)
3118 {
3119 struct lock_list *entry;
3120 enum bfs_result ret;
3121
3122 if (!hlock_class(prev)->key || !hlock_class(next)->key) {
3123 /*
3124 * The warning statements below may trigger a use-after-free
3125 * of the class name. It is better to trigger a use-after free
3126 * and to have the class name most of the time instead of not
3127 * having the class name available.
3128 */
3129 WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
3130 "Detected use-after-free of lock class %px/%s\n",
3131 hlock_class(prev),
3132 hlock_class(prev)->name);
3133 WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
3134 "Detected use-after-free of lock class %px/%s\n",
3135 hlock_class(next),
3136 hlock_class(next)->name);
3137 return 2;
3138 }
3139
3140 if (prev->class_idx == next->class_idx) {
3141 struct lock_class *class = hlock_class(prev);
3142
3143 if (class->cmp_fn &&
3144 class->cmp_fn(prev->instance, next->instance) < 0)
3145 return 2;
3146 }
3147
3148 /*
3149 * Prove that the new <prev> -> <next> dependency would not
3150 * create a circular dependency in the graph. (We do this by
3151 * a breadth-first search into the graph starting at <next>,
3152 * and check whether we can reach <prev>.)
3153 *
3154 * The search is limited by the size of the circular queue (i.e.,
3155 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
3156 * in the graph whose neighbours are to be checked.
3157 */
3158 ret = check_noncircular(next, prev, trace);
3159 if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
3160 return 0;
3161
3162 if (!check_irq_usage(curr, prev, next))
3163 return 0;
3164
3165 /*
3166 * Is the <prev> -> <next> dependency already present?
3167 *
3168 * (this may occur even though this is a new chain: consider
3169 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
3170 * chains - the second one will be new, but L1 already has
3171 * L2 added to its dependency list, due to the first chain.)
3172 */
3173 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
3174 if (entry->class == hlock_class(next)) {
3175 if (distance == 1)
3176 entry->distance = 1;
3177 entry->dep |= calc_dep(prev, next);
3178
3179 /*
3180 * Also, update the reverse dependency in @next's
3181 * ->locks_before list.
3182 *
3183 * Here we reuse @entry as the cursor, which is fine
3184 * because we won't go to the next iteration of the
3185 * outer loop:
3186 *
3187 * For normal cases, we return in the inner loop.
3188 *
3189 * If we fail to return, we have inconsistency, i.e.
3190 * <prev>::locks_after contains <next> while
3191 * <next>::locks_before doesn't contain <prev>. In
3192 * that case, we return after the inner and indicate
3193 * something is wrong.
3194 */
3195 list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
3196 if (entry->class == hlock_class(prev)) {
3197 if (distance == 1)
3198 entry->distance = 1;
3199 entry->dep |= calc_depb(prev, next);
3200 return 1;
3201 }
3202 }
3203
3204 /* <prev> is not found in <next>::locks_before */
3205 return 0;
3206 }
3207 }
3208
3209 /*
3210 * Is the <prev> -> <next> link redundant?
3211 */
3212 ret = check_redundant(prev, next);
3213 if (bfs_error(ret))
3214 return 0;
3215 else if (ret == BFS_RMATCH)
3216 return 2;
3217
3218 if (!*trace) {
3219 *trace = save_trace();
3220 if (!*trace)
3221 return 0;
3222 }
3223
3224 /*
3225 * Ok, all validations passed, add the new lock
3226 * to the previous lock's dependency list:
3227 */
3228 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
3229 &hlock_class(prev)->locks_after, distance,
3230 calc_dep(prev, next), *trace);
3231
3232 if (!ret)
3233 return 0;
3234
3235 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
3236 &hlock_class(next)->locks_before, distance,
3237 calc_depb(prev, next), *trace);
3238 if (!ret)
3239 return 0;
3240
3241 return 2;
3242 }
3243
3244 /*
3245 * Add the dependency to all directly-previous locks that are 'relevant'.
3246 * The ones that are relevant are (in increasing distance from curr):
3247 * all consecutive trylock entries and the final non-trylock entry - or
3248 * the end of this context's lock-chain - whichever comes first.
3249 */
3250 static int
check_prevs_add(struct task_struct * curr,struct held_lock * next)3251 check_prevs_add(struct task_struct *curr, struct held_lock *next)
3252 {
3253 struct lock_trace *trace = NULL;
3254 int depth = curr->lockdep_depth;
3255 struct held_lock *hlock;
3256
3257 /*
3258 * Debugging checks.
3259 *
3260 * Depth must not be zero for a non-head lock:
3261 */
3262 if (!depth)
3263 goto out_bug;
3264 /*
3265 * At least two relevant locks must exist for this
3266 * to be a head:
3267 */
3268 if (curr->held_locks[depth].irq_context !=
3269 curr->held_locks[depth-1].irq_context)
3270 goto out_bug;
3271
3272 for (;;) {
3273 u16 distance = curr->lockdep_depth - depth + 1;
3274 hlock = curr->held_locks + depth - 1;
3275
3276 if (hlock->check) {
3277 int ret = check_prev_add(curr, hlock, next, distance, &trace);
3278 if (!ret)
3279 return 0;
3280
3281 /*
3282 * Stop after the first non-trylock entry,
3283 * as non-trylock entries have added their
3284 * own direct dependencies already, so this
3285 * lock is connected to them indirectly:
3286 */
3287 if (!hlock->trylock)
3288 break;
3289 }
3290
3291 depth--;
3292 /*
3293 * End of lock-stack?
3294 */
3295 if (!depth)
3296 break;
3297 /*
3298 * Stop the search if we cross into another context:
3299 */
3300 if (curr->held_locks[depth].irq_context !=
3301 curr->held_locks[depth-1].irq_context)
3302 break;
3303 }
3304 return 1;
3305 out_bug:
3306 if (!debug_locks_off_graph_unlock())
3307 return 0;
3308
3309 /*
3310 * Clearly we all shouldn't be here, but since we made it we
3311 * can reliable say we messed up our state. See the above two
3312 * gotos for reasons why we could possibly end up here.
3313 */
3314 WARN_ON(1);
3315
3316 return 0;
3317 }
3318
3319 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
3320 static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
3321 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
3322 unsigned long nr_zapped_lock_chains;
3323 unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
3324 unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
3325 unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
3326
3327 /*
3328 * The first 2 chain_hlocks entries in the chain block in the bucket
3329 * list contains the following meta data:
3330 *
3331 * entry[0]:
3332 * Bit 15 - always set to 1 (it is not a class index)
3333 * Bits 0-14 - upper 15 bits of the next block index
3334 * entry[1] - lower 16 bits of next block index
3335 *
3336 * A next block index of all 1 bits means it is the end of the list.
3337 *
3338 * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
3339 * the chain block size:
3340 *
3341 * entry[2] - upper 16 bits of the chain block size
3342 * entry[3] - lower 16 bits of the chain block size
3343 */
3344 #define MAX_CHAIN_BUCKETS 16
3345 #define CHAIN_BLK_FLAG (1U << 15)
3346 #define CHAIN_BLK_LIST_END 0xFFFFU
3347
3348 static int chain_block_buckets[MAX_CHAIN_BUCKETS];
3349
size_to_bucket(int size)3350 static inline int size_to_bucket(int size)
3351 {
3352 if (size > MAX_CHAIN_BUCKETS)
3353 return 0;
3354
3355 return size - 1;
3356 }
3357
3358 /*
3359 * Iterate all the chain blocks in a bucket.
3360 */
3361 #define for_each_chain_block(bucket, prev, curr) \
3362 for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
3363 (curr) >= 0; \
3364 (prev) = (curr), (curr) = chain_block_next(curr))
3365
3366 /*
3367 * next block or -1
3368 */
chain_block_next(int offset)3369 static inline int chain_block_next(int offset)
3370 {
3371 int next = chain_hlocks[offset];
3372
3373 WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
3374
3375 if (next == CHAIN_BLK_LIST_END)
3376 return -1;
3377
3378 next &= ~CHAIN_BLK_FLAG;
3379 next <<= 16;
3380 next |= chain_hlocks[offset + 1];
3381
3382 return next;
3383 }
3384
3385 /*
3386 * bucket-0 only
3387 */
chain_block_size(int offset)3388 static inline int chain_block_size(int offset)
3389 {
3390 return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
3391 }
3392
init_chain_block(int offset,int next,int bucket,int size)3393 static inline void init_chain_block(int offset, int next, int bucket, int size)
3394 {
3395 chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
3396 chain_hlocks[offset + 1] = (u16)next;
3397
3398 if (size && !bucket) {
3399 chain_hlocks[offset + 2] = size >> 16;
3400 chain_hlocks[offset + 3] = (u16)size;
3401 }
3402 }
3403
add_chain_block(int offset,int size)3404 static inline void add_chain_block(int offset, int size)
3405 {
3406 int bucket = size_to_bucket(size);
3407 int next = chain_block_buckets[bucket];
3408 int prev, curr;
3409
3410 if (unlikely(size < 2)) {
3411 /*
3412 * We can't store single entries on the freelist. Leak them.
3413 *
3414 * One possible way out would be to uniquely mark them, other
3415 * than with CHAIN_BLK_FLAG, such that we can recover them when
3416 * the block before it is re-added.
3417 */
3418 if (size)
3419 nr_lost_chain_hlocks++;
3420 return;
3421 }
3422
3423 nr_free_chain_hlocks += size;
3424 if (!bucket) {
3425 nr_large_chain_blocks++;
3426
3427 /*
3428 * Variable sized, sort large to small.
3429 */
3430 for_each_chain_block(0, prev, curr) {
3431 if (size >= chain_block_size(curr))
3432 break;
3433 }
3434 init_chain_block(offset, curr, 0, size);
3435 if (prev < 0)
3436 chain_block_buckets[0] = offset;
3437 else
3438 init_chain_block(prev, offset, 0, 0);
3439 return;
3440 }
3441 /*
3442 * Fixed size, add to head.
3443 */
3444 init_chain_block(offset, next, bucket, size);
3445 chain_block_buckets[bucket] = offset;
3446 }
3447
3448 /*
3449 * Only the first block in the list can be deleted.
3450 *
3451 * For the variable size bucket[0], the first block (the largest one) is
3452 * returned, broken up and put back into the pool. So if a chain block of
3453 * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
3454 * queued up after the primordial chain block and never be used until the
3455 * hlock entries in the primordial chain block is almost used up. That
3456 * causes fragmentation and reduce allocation efficiency. That can be
3457 * monitored by looking at the "large chain blocks" number in lockdep_stats.
3458 */
del_chain_block(int bucket,int size,int next)3459 static inline void del_chain_block(int bucket, int size, int next)
3460 {
3461 nr_free_chain_hlocks -= size;
3462 chain_block_buckets[bucket] = next;
3463
3464 if (!bucket)
3465 nr_large_chain_blocks--;
3466 }
3467
init_chain_block_buckets(void)3468 static void init_chain_block_buckets(void)
3469 {
3470 int i;
3471
3472 for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
3473 chain_block_buckets[i] = -1;
3474
3475 add_chain_block(0, ARRAY_SIZE(chain_hlocks));
3476 }
3477
3478 /*
3479 * Return offset of a chain block of the right size or -1 if not found.
3480 *
3481 * Fairly simple worst-fit allocator with the addition of a number of size
3482 * specific free lists.
3483 */
alloc_chain_hlocks(int req)3484 static int alloc_chain_hlocks(int req)
3485 {
3486 int bucket, curr, size;
3487
3488 /*
3489 * We rely on the MSB to act as an escape bit to denote freelist
3490 * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
3491 */
3492 BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
3493
3494 init_data_structures_once();
3495
3496 if (nr_free_chain_hlocks < req)
3497 return -1;
3498
3499 /*
3500 * We require a minimum of 2 (u16) entries to encode a freelist
3501 * 'pointer'.
3502 */
3503 req = max(req, 2);
3504 bucket = size_to_bucket(req);
3505 curr = chain_block_buckets[bucket];
3506
3507 if (bucket) {
3508 if (curr >= 0) {
3509 del_chain_block(bucket, req, chain_block_next(curr));
3510 return curr;
3511 }
3512 /* Try bucket 0 */
3513 curr = chain_block_buckets[0];
3514 }
3515
3516 /*
3517 * The variable sized freelist is sorted by size; the first entry is
3518 * the largest. Use it if it fits.
3519 */
3520 if (curr >= 0) {
3521 size = chain_block_size(curr);
3522 if (likely(size >= req)) {
3523 del_chain_block(0, size, chain_block_next(curr));
3524 if (size > req)
3525 add_chain_block(curr + req, size - req);
3526 return curr;
3527 }
3528 }
3529
3530 /*
3531 * Last resort, split a block in a larger sized bucket.
3532 */
3533 for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
3534 bucket = size_to_bucket(size);
3535 curr = chain_block_buckets[bucket];
3536 if (curr < 0)
3537 continue;
3538
3539 del_chain_block(bucket, size, chain_block_next(curr));
3540 add_chain_block(curr + req, size - req);
3541 return curr;
3542 }
3543
3544 return -1;
3545 }
3546
free_chain_hlocks(int base,int size)3547 static inline void free_chain_hlocks(int base, int size)
3548 {
3549 add_chain_block(base, max(size, 2));
3550 }
3551
lock_chain_get_class(struct lock_chain * chain,int i)3552 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
3553 {
3554 u16 chain_hlock = chain_hlocks[chain->base + i];
3555 unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
3556
3557 return lock_classes + class_idx;
3558 }
3559
3560 /*
3561 * Returns the index of the first held_lock of the current chain
3562 */
get_first_held_lock(struct task_struct * curr,struct held_lock * hlock)3563 static inline int get_first_held_lock(struct task_struct *curr,
3564 struct held_lock *hlock)
3565 {
3566 int i;
3567 struct held_lock *hlock_curr;
3568
3569 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
3570 hlock_curr = curr->held_locks + i;
3571 if (hlock_curr->irq_context != hlock->irq_context)
3572 break;
3573
3574 }
3575
3576 return ++i;
3577 }
3578
3579 #ifdef CONFIG_DEBUG_LOCKDEP
3580 /*
3581 * Returns the next chain_key iteration
3582 */
print_chain_key_iteration(u16 hlock_id,u64 chain_key)3583 static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
3584 {
3585 u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
3586
3587 printk(" hlock_id:%d -> chain_key:%016Lx",
3588 (unsigned int)hlock_id,
3589 (unsigned long long)new_chain_key);
3590 return new_chain_key;
3591 }
3592
3593 static void
print_chain_keys_held_locks(struct task_struct * curr,struct held_lock * hlock_next)3594 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
3595 {
3596 struct held_lock *hlock;
3597 u64 chain_key = INITIAL_CHAIN_KEY;
3598 int depth = curr->lockdep_depth;
3599 int i = get_first_held_lock(curr, hlock_next);
3600
3601 printk("depth: %u (irq_context %u)\n", depth - i + 1,
3602 hlock_next->irq_context);
3603 for (; i < depth; i++) {
3604 hlock = curr->held_locks + i;
3605 chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
3606
3607 print_lock(hlock);
3608 }
3609
3610 print_chain_key_iteration(hlock_id(hlock_next), chain_key);
3611 print_lock(hlock_next);
3612 }
3613
print_chain_keys_chain(struct lock_chain * chain)3614 static void print_chain_keys_chain(struct lock_chain *chain)
3615 {
3616 int i;
3617 u64 chain_key = INITIAL_CHAIN_KEY;
3618 u16 hlock_id;
3619
3620 printk("depth: %u\n", chain->depth);
3621 for (i = 0; i < chain->depth; i++) {
3622 hlock_id = chain_hlocks[chain->base + i];
3623 chain_key = print_chain_key_iteration(hlock_id, chain_key);
3624
3625 print_lock_name(NULL, lock_classes + chain_hlock_class_idx(hlock_id));
3626 printk("\n");
3627 }
3628 }
3629
print_collision(struct task_struct * curr,struct held_lock * hlock_next,struct lock_chain * chain)3630 static void print_collision(struct task_struct *curr,
3631 struct held_lock *hlock_next,
3632 struct lock_chain *chain)
3633 {
3634 nbcon_cpu_emergency_enter();
3635
3636 pr_warn("\n");
3637 pr_warn("============================\n");
3638 pr_warn("WARNING: chain_key collision\n");
3639 print_kernel_ident();
3640 pr_warn("----------------------------\n");
3641 pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
3642 pr_warn("Hash chain already cached but the contents don't match!\n");
3643
3644 pr_warn("Held locks:");
3645 print_chain_keys_held_locks(curr, hlock_next);
3646
3647 pr_warn("Locks in cached chain:");
3648 print_chain_keys_chain(chain);
3649
3650 pr_warn("\nstack backtrace:\n");
3651 dump_stack();
3652
3653 nbcon_cpu_emergency_exit();
3654 }
3655 #endif
3656
3657 /*
3658 * Checks whether the chain and the current held locks are consistent
3659 * in depth and also in content. If they are not it most likely means
3660 * that there was a collision during the calculation of the chain_key.
3661 * Returns: 0 not passed, 1 passed
3662 */
check_no_collision(struct task_struct * curr,struct held_lock * hlock,struct lock_chain * chain)3663 static int check_no_collision(struct task_struct *curr,
3664 struct held_lock *hlock,
3665 struct lock_chain *chain)
3666 {
3667 #ifdef CONFIG_DEBUG_LOCKDEP
3668 int i, j, id;
3669
3670 i = get_first_held_lock(curr, hlock);
3671
3672 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
3673 print_collision(curr, hlock, chain);
3674 return 0;
3675 }
3676
3677 for (j = 0; j < chain->depth - 1; j++, i++) {
3678 id = hlock_id(&curr->held_locks[i]);
3679
3680 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
3681 print_collision(curr, hlock, chain);
3682 return 0;
3683 }
3684 }
3685 #endif
3686 return 1;
3687 }
3688
3689 /*
3690 * Given an index that is >= -1, return the index of the next lock chain.
3691 * Return -2 if there is no next lock chain.
3692 */
lockdep_next_lockchain(long i)3693 long lockdep_next_lockchain(long i)
3694 {
3695 i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
3696 return i < ARRAY_SIZE(lock_chains) ? i : -2;
3697 }
3698
lock_chain_count(void)3699 unsigned long lock_chain_count(void)
3700 {
3701 return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
3702 }
3703
3704 /* Must be called with the graph lock held. */
alloc_lock_chain(void)3705 static struct lock_chain *alloc_lock_chain(void)
3706 {
3707 int idx = find_first_zero_bit(lock_chains_in_use,
3708 ARRAY_SIZE(lock_chains));
3709
3710 if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
3711 return NULL;
3712 __set_bit(idx, lock_chains_in_use);
3713 return lock_chains + idx;
3714 }
3715
3716 /*
3717 * Adds a dependency chain into chain hashtable. And must be called with
3718 * graph_lock held.
3719 *
3720 * Return 0 if fail, and graph_lock is released.
3721 * Return 1 if succeed, with graph_lock held.
3722 */
add_chain_cache(struct task_struct * curr,struct held_lock * hlock,u64 chain_key)3723 static inline int add_chain_cache(struct task_struct *curr,
3724 struct held_lock *hlock,
3725 u64 chain_key)
3726 {
3727 struct hlist_head *hash_head = chainhashentry(chain_key);
3728 struct lock_chain *chain;
3729 int i, j;
3730
3731 /*
3732 * The caller must hold the graph lock, ensure we've got IRQs
3733 * disabled to make this an IRQ-safe lock.. for recursion reasons
3734 * lockdep won't complain about its own locking errors.
3735 */
3736 if (lockdep_assert_locked())
3737 return 0;
3738
3739 chain = alloc_lock_chain();
3740 if (!chain) {
3741 if (!debug_locks_off_graph_unlock())
3742 return 0;
3743
3744 nbcon_cpu_emergency_enter();
3745 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
3746 dump_stack();
3747 nbcon_cpu_emergency_exit();
3748 return 0;
3749 }
3750 chain->chain_key = chain_key;
3751 chain->irq_context = hlock->irq_context;
3752 i = get_first_held_lock(curr, hlock);
3753 chain->depth = curr->lockdep_depth + 1 - i;
3754
3755 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
3756 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
3757 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
3758
3759 j = alloc_chain_hlocks(chain->depth);
3760 if (j < 0) {
3761 if (!debug_locks_off_graph_unlock())
3762 return 0;
3763
3764 nbcon_cpu_emergency_enter();
3765 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
3766 dump_stack();
3767 nbcon_cpu_emergency_exit();
3768 return 0;
3769 }
3770
3771 chain->base = j;
3772 for (j = 0; j < chain->depth - 1; j++, i++) {
3773 int lock_id = hlock_id(curr->held_locks + i);
3774
3775 chain_hlocks[chain->base + j] = lock_id;
3776 }
3777 chain_hlocks[chain->base + j] = hlock_id(hlock);
3778 hlist_add_head_rcu(&chain->entry, hash_head);
3779 debug_atomic_inc(chain_lookup_misses);
3780 inc_chains(chain->irq_context);
3781
3782 return 1;
3783 }
3784
3785 /*
3786 * Look up a dependency chain. Must be called with either the graph lock or
3787 * the RCU read lock held.
3788 */
lookup_chain_cache(u64 chain_key)3789 static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
3790 {
3791 struct hlist_head *hash_head = chainhashentry(chain_key);
3792 struct lock_chain *chain;
3793
3794 hlist_for_each_entry_rcu(chain, hash_head, entry) {
3795 if (READ_ONCE(chain->chain_key) == chain_key) {
3796 debug_atomic_inc(chain_lookup_hits);
3797 return chain;
3798 }
3799 }
3800 return NULL;
3801 }
3802
3803 /*
3804 * If the key is not present yet in dependency chain cache then
3805 * add it and return 1 - in this case the new dependency chain is
3806 * validated. If the key is already hashed, return 0.
3807 * (On return with 1 graph_lock is held.)
3808 */
lookup_chain_cache_add(struct task_struct * curr,struct held_lock * hlock,u64 chain_key)3809 static inline int lookup_chain_cache_add(struct task_struct *curr,
3810 struct held_lock *hlock,
3811 u64 chain_key)
3812 {
3813 struct lock_class *class = hlock_class(hlock);
3814 struct lock_chain *chain = lookup_chain_cache(chain_key);
3815
3816 if (chain) {
3817 cache_hit:
3818 if (!check_no_collision(curr, hlock, chain))
3819 return 0;
3820
3821 if (very_verbose(class)) {
3822 printk("\nhash chain already cached, key: "
3823 "%016Lx tail class: [%px] %s\n",
3824 (unsigned long long)chain_key,
3825 class->key, class->name);
3826 }
3827
3828 return 0;
3829 }
3830
3831 if (very_verbose(class)) {
3832 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
3833 (unsigned long long)chain_key, class->key, class->name);
3834 }
3835
3836 if (!graph_lock())
3837 return 0;
3838
3839 /*
3840 * We have to walk the chain again locked - to avoid duplicates:
3841 */
3842 chain = lookup_chain_cache(chain_key);
3843 if (chain) {
3844 graph_unlock();
3845 goto cache_hit;
3846 }
3847
3848 if (!add_chain_cache(curr, hlock, chain_key))
3849 return 0;
3850
3851 return 1;
3852 }
3853
validate_chain(struct task_struct * curr,struct held_lock * hlock,int chain_head,u64 chain_key)3854 static int validate_chain(struct task_struct *curr,
3855 struct held_lock *hlock,
3856 int chain_head, u64 chain_key)
3857 {
3858 /*
3859 * Trylock needs to maintain the stack of held locks, but it
3860 * does not add new dependencies, because trylock can be done
3861 * in any order.
3862 *
3863 * We look up the chain_key and do the O(N^2) check and update of
3864 * the dependencies only if this is a new dependency chain.
3865 * (If lookup_chain_cache_add() return with 1 it acquires
3866 * graph_lock for us)
3867 */
3868 if (!hlock->trylock && hlock->check &&
3869 lookup_chain_cache_add(curr, hlock, chain_key)) {
3870 /*
3871 * Check whether last held lock:
3872 *
3873 * - is irq-safe, if this lock is irq-unsafe
3874 * - is softirq-safe, if this lock is hardirq-unsafe
3875 *
3876 * And check whether the new lock's dependency graph
3877 * could lead back to the previous lock:
3878 *
3879 * - within the current held-lock stack
3880 * - across our accumulated lock dependency records
3881 *
3882 * any of these scenarios could lead to a deadlock.
3883 */
3884 /*
3885 * The simple case: does the current hold the same lock
3886 * already?
3887 */
3888 int ret = check_deadlock(curr, hlock);
3889
3890 if (!ret)
3891 return 0;
3892 /*
3893 * Add dependency only if this lock is not the head
3894 * of the chain, and if the new lock introduces no more
3895 * lock dependency (because we already hold a lock with the
3896 * same lock class) nor deadlock (because the nest_lock
3897 * serializes nesting locks), see the comments for
3898 * check_deadlock().
3899 */
3900 if (!chain_head && ret != 2) {
3901 if (!check_prevs_add(curr, hlock))
3902 return 0;
3903 }
3904
3905 graph_unlock();
3906 } else {
3907 /* after lookup_chain_cache_add(): */
3908 if (unlikely(!debug_locks))
3909 return 0;
3910 }
3911
3912 return 1;
3913 }
3914 #else
validate_chain(struct task_struct * curr,struct held_lock * hlock,int chain_head,u64 chain_key)3915 static inline int validate_chain(struct task_struct *curr,
3916 struct held_lock *hlock,
3917 int chain_head, u64 chain_key)
3918 {
3919 return 1;
3920 }
3921
init_chain_block_buckets(void)3922 static void init_chain_block_buckets(void) { }
3923 #endif /* CONFIG_PROVE_LOCKING */
3924
3925 /*
3926 * We are building curr_chain_key incrementally, so double-check
3927 * it from scratch, to make sure that it's done correctly:
3928 */
check_chain_key(struct task_struct * curr)3929 static void check_chain_key(struct task_struct *curr)
3930 {
3931 #ifdef CONFIG_DEBUG_LOCKDEP
3932 struct held_lock *hlock, *prev_hlock = NULL;
3933 unsigned int i;
3934 u64 chain_key = INITIAL_CHAIN_KEY;
3935
3936 for (i = 0; i < curr->lockdep_depth; i++) {
3937 hlock = curr->held_locks + i;
3938 if (chain_key != hlock->prev_chain_key) {
3939 debug_locks_off();
3940 /*
3941 * We got mighty confused, our chain keys don't match
3942 * with what we expect, someone trample on our task state?
3943 */
3944 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3945 curr->lockdep_depth, i,
3946 (unsigned long long)chain_key,
3947 (unsigned long long)hlock->prev_chain_key);
3948 return;
3949 }
3950
3951 /*
3952 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3953 * it registered lock class index?
3954 */
3955 if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3956 return;
3957
3958 if (prev_hlock && (prev_hlock->irq_context !=
3959 hlock->irq_context))
3960 chain_key = INITIAL_CHAIN_KEY;
3961 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
3962 prev_hlock = hlock;
3963 }
3964 if (chain_key != curr->curr_chain_key) {
3965 debug_locks_off();
3966 /*
3967 * More smoking hash instead of calculating it, damn see these
3968 * numbers float.. I bet that a pink elephant stepped on my memory.
3969 */
3970 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3971 curr->lockdep_depth, i,
3972 (unsigned long long)chain_key,
3973 (unsigned long long)curr->curr_chain_key);
3974 }
3975 #endif
3976 }
3977
3978 #ifdef CONFIG_PROVE_LOCKING
3979 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3980 enum lock_usage_bit new_bit);
3981
print_usage_bug_scenario(struct held_lock * lock)3982 static void print_usage_bug_scenario(struct held_lock *lock)
3983 {
3984 struct lock_class *class = hlock_class(lock);
3985
3986 printk(" Possible unsafe locking scenario:\n\n");
3987 printk(" CPU0\n");
3988 printk(" ----\n");
3989 printk(" lock(");
3990 __print_lock_name(lock, class);
3991 printk(KERN_CONT ");\n");
3992 printk(" <Interrupt>\n");
3993 printk(" lock(");
3994 __print_lock_name(lock, class);
3995 printk(KERN_CONT ");\n");
3996 printk("\n *** DEADLOCK ***\n\n");
3997 }
3998
3999 static void
print_usage_bug(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit prev_bit,enum lock_usage_bit new_bit)4000 print_usage_bug(struct task_struct *curr, struct held_lock *this,
4001 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
4002 {
4003 if (!debug_locks_off() || debug_locks_silent)
4004 return;
4005
4006 nbcon_cpu_emergency_enter();
4007
4008 pr_warn("\n");
4009 pr_warn("================================\n");
4010 pr_warn("WARNING: inconsistent lock state\n");
4011 print_kernel_ident();
4012 pr_warn("--------------------------------\n");
4013
4014 pr_warn("inconsistent {%s} -> {%s} usage.\n",
4015 usage_str[prev_bit], usage_str[new_bit]);
4016
4017 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
4018 curr->comm, task_pid_nr(curr),
4019 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
4020 lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
4021 lockdep_hardirqs_enabled(),
4022 lockdep_softirqs_enabled(curr));
4023 print_lock(this);
4024
4025 pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
4026 print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
4027
4028 print_irqtrace_events(curr);
4029 pr_warn("\nother info that might help us debug this:\n");
4030 print_usage_bug_scenario(this);
4031
4032 lockdep_print_held_locks(curr);
4033
4034 pr_warn("\nstack backtrace:\n");
4035 dump_stack();
4036
4037 nbcon_cpu_emergency_exit();
4038 }
4039
4040 /*
4041 * Print out an error if an invalid bit is set:
4042 */
4043 static inline int
valid_state(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit new_bit,enum lock_usage_bit bad_bit)4044 valid_state(struct task_struct *curr, struct held_lock *this,
4045 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
4046 {
4047 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
4048 graph_unlock();
4049 print_usage_bug(curr, this, bad_bit, new_bit);
4050 return 0;
4051 }
4052 return 1;
4053 }
4054
4055
4056 /*
4057 * print irq inversion bug:
4058 */
4059 static void
print_irq_inversion_bug(struct task_struct * curr,struct lock_list * root,struct lock_list * other,struct held_lock * this,int forwards,const char * irqclass)4060 print_irq_inversion_bug(struct task_struct *curr,
4061 struct lock_list *root, struct lock_list *other,
4062 struct held_lock *this, int forwards,
4063 const char *irqclass)
4064 {
4065 struct lock_list *entry = other;
4066 struct lock_list *middle = NULL;
4067 int depth;
4068
4069 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
4070 return;
4071
4072 nbcon_cpu_emergency_enter();
4073
4074 pr_warn("\n");
4075 pr_warn("========================================================\n");
4076 pr_warn("WARNING: possible irq lock inversion dependency detected\n");
4077 print_kernel_ident();
4078 pr_warn("--------------------------------------------------------\n");
4079 pr_warn("%s/%d just changed the state of lock:\n",
4080 curr->comm, task_pid_nr(curr));
4081 print_lock(this);
4082 if (forwards)
4083 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
4084 else
4085 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
4086 print_lock_name(NULL, other->class);
4087 pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
4088
4089 pr_warn("\nother info that might help us debug this:\n");
4090
4091 /* Find a middle lock (if one exists) */
4092 depth = get_lock_depth(other);
4093 do {
4094 if (depth == 0 && (entry != root)) {
4095 pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
4096 break;
4097 }
4098 middle = entry;
4099 entry = get_lock_parent(entry);
4100 depth--;
4101 } while (entry && entry != root && (depth >= 0));
4102 if (forwards)
4103 print_irq_lock_scenario(root, other,
4104 middle ? middle->class : root->class, other->class);
4105 else
4106 print_irq_lock_scenario(other, root,
4107 middle ? middle->class : other->class, root->class);
4108
4109 lockdep_print_held_locks(curr);
4110
4111 pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
4112 root->trace = save_trace();
4113 if (!root->trace)
4114 goto out;
4115 print_shortest_lock_dependencies(other, root);
4116
4117 pr_warn("\nstack backtrace:\n");
4118 dump_stack();
4119 out:
4120 nbcon_cpu_emergency_exit();
4121 }
4122
4123 /*
4124 * Prove that in the forwards-direction subgraph starting at <this>
4125 * there is no lock matching <mask>:
4126 */
4127 static int
check_usage_forwards(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit bit)4128 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
4129 enum lock_usage_bit bit)
4130 {
4131 enum bfs_result ret;
4132 struct lock_list root;
4133 struct lock_list *target_entry;
4134 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4135 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4136
4137 bfs_init_root(&root, this);
4138 ret = find_usage_forwards(&root, usage_mask, &target_entry);
4139 if (bfs_error(ret)) {
4140 print_bfs_bug(ret);
4141 return 0;
4142 }
4143 if (ret == BFS_RNOMATCH)
4144 return 1;
4145
4146 /* Check whether write or read usage is the match */
4147 if (target_entry->class->usage_mask & lock_flag(bit)) {
4148 print_irq_inversion_bug(curr, &root, target_entry,
4149 this, 1, state_name(bit));
4150 } else {
4151 print_irq_inversion_bug(curr, &root, target_entry,
4152 this, 1, state_name(read_bit));
4153 }
4154
4155 return 0;
4156 }
4157
4158 /*
4159 * Prove that in the backwards-direction subgraph starting at <this>
4160 * there is no lock matching <mask>:
4161 */
4162 static int
check_usage_backwards(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit bit)4163 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
4164 enum lock_usage_bit bit)
4165 {
4166 enum bfs_result ret;
4167 struct lock_list root;
4168 struct lock_list *target_entry;
4169 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4170 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4171
4172 bfs_init_rootb(&root, this);
4173 ret = find_usage_backwards(&root, usage_mask, &target_entry);
4174 if (bfs_error(ret)) {
4175 print_bfs_bug(ret);
4176 return 0;
4177 }
4178 if (ret == BFS_RNOMATCH)
4179 return 1;
4180
4181 /* Check whether write or read usage is the match */
4182 if (target_entry->class->usage_mask & lock_flag(bit)) {
4183 print_irq_inversion_bug(curr, &root, target_entry,
4184 this, 0, state_name(bit));
4185 } else {
4186 print_irq_inversion_bug(curr, &root, target_entry,
4187 this, 0, state_name(read_bit));
4188 }
4189
4190 return 0;
4191 }
4192
print_irqtrace_events(struct task_struct * curr)4193 void print_irqtrace_events(struct task_struct *curr)
4194 {
4195 const struct irqtrace_events *trace = &curr->irqtrace;
4196
4197 nbcon_cpu_emergency_enter();
4198
4199 printk("irq event stamp: %u\n", trace->irq_events);
4200 printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
4201 trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
4202 (void *)trace->hardirq_enable_ip);
4203 printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
4204 trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
4205 (void *)trace->hardirq_disable_ip);
4206 printk("softirqs last enabled at (%u): [<%px>] %pS\n",
4207 trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
4208 (void *)trace->softirq_enable_ip);
4209 printk("softirqs last disabled at (%u): [<%px>] %pS\n",
4210 trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
4211 (void *)trace->softirq_disable_ip);
4212
4213 nbcon_cpu_emergency_exit();
4214 }
4215
HARDIRQ_verbose(struct lock_class * class)4216 static int HARDIRQ_verbose(struct lock_class *class)
4217 {
4218 #if HARDIRQ_VERBOSE
4219 return class_filter(class);
4220 #endif
4221 return 0;
4222 }
4223
SOFTIRQ_verbose(struct lock_class * class)4224 static int SOFTIRQ_verbose(struct lock_class *class)
4225 {
4226 #if SOFTIRQ_VERBOSE
4227 return class_filter(class);
4228 #endif
4229 return 0;
4230 }
4231
4232 static int (*state_verbose_f[])(struct lock_class *class) = {
4233 #define LOCKDEP_STATE(__STATE) \
4234 __STATE##_verbose,
4235 #include "lockdep_states.h"
4236 #undef LOCKDEP_STATE
4237 };
4238
state_verbose(enum lock_usage_bit bit,struct lock_class * class)4239 static inline int state_verbose(enum lock_usage_bit bit,
4240 struct lock_class *class)
4241 {
4242 return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
4243 }
4244
4245 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
4246 enum lock_usage_bit bit, const char *name);
4247
4248 static int
mark_lock_irq(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit new_bit)4249 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
4250 enum lock_usage_bit new_bit)
4251 {
4252 int excl_bit = exclusive_bit(new_bit);
4253 int read = new_bit & LOCK_USAGE_READ_MASK;
4254 int dir = new_bit & LOCK_USAGE_DIR_MASK;
4255
4256 /*
4257 * Validate that this particular lock does not have conflicting
4258 * usage states.
4259 */
4260 if (!valid_state(curr, this, new_bit, excl_bit))
4261 return 0;
4262
4263 /*
4264 * Check for read in write conflicts
4265 */
4266 if (!read && !valid_state(curr, this, new_bit,
4267 excl_bit + LOCK_USAGE_READ_MASK))
4268 return 0;
4269
4270
4271 /*
4272 * Validate that the lock dependencies don't have conflicting usage
4273 * states.
4274 */
4275 if (dir) {
4276 /*
4277 * mark ENABLED has to look backwards -- to ensure no dependee
4278 * has USED_IN state, which, again, would allow recursion deadlocks.
4279 */
4280 if (!check_usage_backwards(curr, this, excl_bit))
4281 return 0;
4282 } else {
4283 /*
4284 * mark USED_IN has to look forwards -- to ensure no dependency
4285 * has ENABLED state, which would allow recursion deadlocks.
4286 */
4287 if (!check_usage_forwards(curr, this, excl_bit))
4288 return 0;
4289 }
4290
4291 if (state_verbose(new_bit, hlock_class(this)))
4292 return 2;
4293
4294 return 1;
4295 }
4296
4297 /*
4298 * Mark all held locks with a usage bit:
4299 */
4300 static int
mark_held_locks(struct task_struct * curr,enum lock_usage_bit base_bit)4301 mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
4302 {
4303 struct held_lock *hlock;
4304 int i;
4305
4306 for (i = 0; i < curr->lockdep_depth; i++) {
4307 enum lock_usage_bit hlock_bit = base_bit;
4308 hlock = curr->held_locks + i;
4309
4310 if (hlock->read)
4311 hlock_bit += LOCK_USAGE_READ_MASK;
4312
4313 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
4314
4315 if (!hlock->check)
4316 continue;
4317
4318 if (!mark_lock(curr, hlock, hlock_bit))
4319 return 0;
4320 }
4321
4322 return 1;
4323 }
4324
4325 /*
4326 * Hardirqs will be enabled:
4327 */
__trace_hardirqs_on_caller(void)4328 static void __trace_hardirqs_on_caller(void)
4329 {
4330 struct task_struct *curr = current;
4331
4332 /*
4333 * We are going to turn hardirqs on, so set the
4334 * usage bit for all held locks:
4335 */
4336 if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
4337 return;
4338 /*
4339 * If we have softirqs enabled, then set the usage
4340 * bit for all held locks. (disabled hardirqs prevented
4341 * this bit from being set before)
4342 */
4343 if (curr->softirqs_enabled)
4344 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
4345 }
4346
4347 /**
4348 * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
4349 *
4350 * Invoked before a possible transition to RCU idle from exit to user or
4351 * guest mode. This ensures that all RCU operations are done before RCU
4352 * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
4353 * invoked to set the final state.
4354 */
lockdep_hardirqs_on_prepare(void)4355 void lockdep_hardirqs_on_prepare(void)
4356 {
4357 if (unlikely(!debug_locks))
4358 return;
4359
4360 /*
4361 * NMIs do not (and cannot) track lock dependencies, nothing to do.
4362 */
4363 if (unlikely(in_nmi()))
4364 return;
4365
4366 if (unlikely(this_cpu_read(lockdep_recursion)))
4367 return;
4368
4369 if (unlikely(lockdep_hardirqs_enabled())) {
4370 /*
4371 * Neither irq nor preemption are disabled here
4372 * so this is racy by nature but losing one hit
4373 * in a stat is not a big deal.
4374 */
4375 __debug_atomic_inc(redundant_hardirqs_on);
4376 return;
4377 }
4378
4379 /*
4380 * We're enabling irqs and according to our state above irqs weren't
4381 * already enabled, yet we find the hardware thinks they are in fact
4382 * enabled.. someone messed up their IRQ state tracing.
4383 */
4384 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4385 return;
4386
4387 /*
4388 * See the fine text that goes along with this variable definition.
4389 */
4390 if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
4391 return;
4392
4393 /*
4394 * Can't allow enabling interrupts while in an interrupt handler,
4395 * that's general bad form and such. Recursion, limited stack etc..
4396 */
4397 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
4398 return;
4399
4400 current->hardirq_chain_key = current->curr_chain_key;
4401
4402 lockdep_recursion_inc();
4403 __trace_hardirqs_on_caller();
4404 lockdep_recursion_finish();
4405 }
4406 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
4407
lockdep_hardirqs_on(unsigned long ip)4408 void noinstr lockdep_hardirqs_on(unsigned long ip)
4409 {
4410 struct irqtrace_events *trace = ¤t->irqtrace;
4411
4412 if (unlikely(!debug_locks))
4413 return;
4414
4415 /*
4416 * NMIs can happen in the middle of local_irq_{en,dis}able() where the
4417 * tracking state and hardware state are out of sync.
4418 *
4419 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
4420 * and not rely on hardware state like normal interrupts.
4421 */
4422 if (unlikely(in_nmi())) {
4423 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4424 return;
4425
4426 /*
4427 * Skip:
4428 * - recursion check, because NMI can hit lockdep;
4429 * - hardware state check, because above;
4430 * - chain_key check, see lockdep_hardirqs_on_prepare().
4431 */
4432 goto skip_checks;
4433 }
4434
4435 if (unlikely(this_cpu_read(lockdep_recursion)))
4436 return;
4437
4438 if (lockdep_hardirqs_enabled()) {
4439 /*
4440 * Neither irq nor preemption are disabled here
4441 * so this is racy by nature but losing one hit
4442 * in a stat is not a big deal.
4443 */
4444 __debug_atomic_inc(redundant_hardirqs_on);
4445 return;
4446 }
4447
4448 /*
4449 * We're enabling irqs and according to our state above irqs weren't
4450 * already enabled, yet we find the hardware thinks they are in fact
4451 * enabled.. someone messed up their IRQ state tracing.
4452 */
4453 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4454 return;
4455
4456 /*
4457 * Ensure the lock stack remained unchanged between
4458 * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
4459 */
4460 DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
4461 current->curr_chain_key);
4462
4463 skip_checks:
4464 /* we'll do an OFF -> ON transition: */
4465 __this_cpu_write(hardirqs_enabled, 1);
4466 trace->hardirq_enable_ip = ip;
4467 trace->hardirq_enable_event = ++trace->irq_events;
4468 debug_atomic_inc(hardirqs_on_events);
4469 }
4470 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
4471
4472 /*
4473 * Hardirqs were disabled:
4474 */
lockdep_hardirqs_off(unsigned long ip)4475 void noinstr lockdep_hardirqs_off(unsigned long ip)
4476 {
4477 if (unlikely(!debug_locks))
4478 return;
4479
4480 /*
4481 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
4482 * they will restore the software state. This ensures the software
4483 * state is consistent inside NMIs as well.
4484 */
4485 if (in_nmi()) {
4486 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4487 return;
4488 } else if (__this_cpu_read(lockdep_recursion))
4489 return;
4490
4491 /*
4492 * So we're supposed to get called after you mask local IRQs, but for
4493 * some reason the hardware doesn't quite think you did a proper job.
4494 */
4495 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4496 return;
4497
4498 if (lockdep_hardirqs_enabled()) {
4499 struct irqtrace_events *trace = ¤t->irqtrace;
4500
4501 /*
4502 * We have done an ON -> OFF transition:
4503 */
4504 __this_cpu_write(hardirqs_enabled, 0);
4505 trace->hardirq_disable_ip = ip;
4506 trace->hardirq_disable_event = ++trace->irq_events;
4507 debug_atomic_inc(hardirqs_off_events);
4508 } else {
4509 debug_atomic_inc(redundant_hardirqs_off);
4510 }
4511 }
4512 EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
4513
4514 /*
4515 * Softirqs will be enabled:
4516 */
lockdep_softirqs_on(unsigned long ip)4517 void lockdep_softirqs_on(unsigned long ip)
4518 {
4519 struct irqtrace_events *trace = ¤t->irqtrace;
4520
4521 if (unlikely(!lockdep_enabled()))
4522 return;
4523
4524 /*
4525 * We fancy IRQs being disabled here, see softirq.c, avoids
4526 * funny state and nesting things.
4527 */
4528 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4529 return;
4530
4531 if (current->softirqs_enabled) {
4532 debug_atomic_inc(redundant_softirqs_on);
4533 return;
4534 }
4535
4536 lockdep_recursion_inc();
4537 /*
4538 * We'll do an OFF -> ON transition:
4539 */
4540 current->softirqs_enabled = 1;
4541 trace->softirq_enable_ip = ip;
4542 trace->softirq_enable_event = ++trace->irq_events;
4543 debug_atomic_inc(softirqs_on_events);
4544 /*
4545 * We are going to turn softirqs on, so set the
4546 * usage bit for all held locks, if hardirqs are
4547 * enabled too:
4548 */
4549 if (lockdep_hardirqs_enabled())
4550 mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
4551 lockdep_recursion_finish();
4552 }
4553
4554 /*
4555 * Softirqs were disabled:
4556 */
lockdep_softirqs_off(unsigned long ip)4557 void lockdep_softirqs_off(unsigned long ip)
4558 {
4559 if (unlikely(!lockdep_enabled()))
4560 return;
4561
4562 /*
4563 * We fancy IRQs being disabled here, see softirq.c
4564 */
4565 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4566 return;
4567
4568 if (current->softirqs_enabled) {
4569 struct irqtrace_events *trace = ¤t->irqtrace;
4570
4571 /*
4572 * We have done an ON -> OFF transition:
4573 */
4574 current->softirqs_enabled = 0;
4575 trace->softirq_disable_ip = ip;
4576 trace->softirq_disable_event = ++trace->irq_events;
4577 debug_atomic_inc(softirqs_off_events);
4578 /*
4579 * Whoops, we wanted softirqs off, so why aren't they?
4580 */
4581 DEBUG_LOCKS_WARN_ON(!softirq_count());
4582 } else
4583 debug_atomic_inc(redundant_softirqs_off);
4584 }
4585
4586 static int
mark_usage(struct task_struct * curr,struct held_lock * hlock,int check)4587 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4588 {
4589 if (!check)
4590 goto lock_used;
4591
4592 /*
4593 * If non-trylock use in a hardirq or softirq context, then
4594 * mark the lock as used in these contexts:
4595 */
4596 if (!hlock->trylock) {
4597 if (hlock->read) {
4598 if (lockdep_hardirq_context())
4599 if (!mark_lock(curr, hlock,
4600 LOCK_USED_IN_HARDIRQ_READ))
4601 return 0;
4602 if (curr->softirq_context)
4603 if (!mark_lock(curr, hlock,
4604 LOCK_USED_IN_SOFTIRQ_READ))
4605 return 0;
4606 } else {
4607 if (lockdep_hardirq_context())
4608 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
4609 return 0;
4610 if (curr->softirq_context)
4611 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
4612 return 0;
4613 }
4614 }
4615
4616 /*
4617 * For lock_sync(), don't mark the ENABLED usage, since lock_sync()
4618 * creates no critical section and no extra dependency can be introduced
4619 * by interrupts
4620 */
4621 if (!hlock->hardirqs_off && !hlock->sync) {
4622 if (hlock->read) {
4623 if (!mark_lock(curr, hlock,
4624 LOCK_ENABLED_HARDIRQ_READ))
4625 return 0;
4626 if (curr->softirqs_enabled)
4627 if (!mark_lock(curr, hlock,
4628 LOCK_ENABLED_SOFTIRQ_READ))
4629 return 0;
4630 } else {
4631 if (!mark_lock(curr, hlock,
4632 LOCK_ENABLED_HARDIRQ))
4633 return 0;
4634 if (curr->softirqs_enabled)
4635 if (!mark_lock(curr, hlock,
4636 LOCK_ENABLED_SOFTIRQ))
4637 return 0;
4638 }
4639 }
4640
4641 lock_used:
4642 /* mark it as used: */
4643 if (!mark_lock(curr, hlock, LOCK_USED))
4644 return 0;
4645
4646 return 1;
4647 }
4648
task_irq_context(struct task_struct * task)4649 static inline unsigned int task_irq_context(struct task_struct *task)
4650 {
4651 return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
4652 LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
4653 }
4654
separate_irq_context(struct task_struct * curr,struct held_lock * hlock)4655 static int separate_irq_context(struct task_struct *curr,
4656 struct held_lock *hlock)
4657 {
4658 unsigned int depth = curr->lockdep_depth;
4659
4660 /*
4661 * Keep track of points where we cross into an interrupt context:
4662 */
4663 if (depth) {
4664 struct held_lock *prev_hlock;
4665
4666 prev_hlock = curr->held_locks + depth-1;
4667 /*
4668 * If we cross into another context, reset the
4669 * hash key (this also prevents the checking and the
4670 * adding of the dependency to 'prev'):
4671 */
4672 if (prev_hlock->irq_context != hlock->irq_context)
4673 return 1;
4674 }
4675 return 0;
4676 }
4677
4678 /*
4679 * Mark a lock with a usage bit, and validate the state transition:
4680 */
mark_lock(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit new_bit)4681 static int mark_lock(struct task_struct *curr, struct held_lock *this,
4682 enum lock_usage_bit new_bit)
4683 {
4684 unsigned int new_mask, ret = 1;
4685
4686 if (new_bit >= LOCK_USAGE_STATES) {
4687 DEBUG_LOCKS_WARN_ON(1);
4688 return 0;
4689 }
4690
4691 if (new_bit == LOCK_USED && this->read)
4692 new_bit = LOCK_USED_READ;
4693
4694 new_mask = 1 << new_bit;
4695
4696 /*
4697 * If already set then do not dirty the cacheline,
4698 * nor do any checks:
4699 */
4700 if (likely(hlock_class(this)->usage_mask & new_mask))
4701 return 1;
4702
4703 if (!graph_lock())
4704 return 0;
4705 /*
4706 * Make sure we didn't race:
4707 */
4708 if (unlikely(hlock_class(this)->usage_mask & new_mask))
4709 goto unlock;
4710
4711 if (!hlock_class(this)->usage_mask)
4712 debug_atomic_dec(nr_unused_locks);
4713
4714 hlock_class(this)->usage_mask |= new_mask;
4715
4716 if (new_bit < LOCK_TRACE_STATES) {
4717 if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
4718 return 0;
4719 }
4720
4721 if (new_bit < LOCK_USED) {
4722 ret = mark_lock_irq(curr, this, new_bit);
4723 if (!ret)
4724 return 0;
4725 }
4726
4727 unlock:
4728 graph_unlock();
4729
4730 /*
4731 * We must printk outside of the graph_lock:
4732 */
4733 if (ret == 2) {
4734 nbcon_cpu_emergency_enter();
4735 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
4736 print_lock(this);
4737 print_irqtrace_events(curr);
4738 dump_stack();
4739 nbcon_cpu_emergency_exit();
4740 }
4741
4742 return ret;
4743 }
4744
task_wait_context(struct task_struct * curr)4745 static inline short task_wait_context(struct task_struct *curr)
4746 {
4747 /*
4748 * Set appropriate wait type for the context; for IRQs we have to take
4749 * into account force_irqthread as that is implied by PREEMPT_RT.
4750 */
4751 if (lockdep_hardirq_context()) {
4752 /*
4753 * Check if force_irqthreads will run us threaded.
4754 */
4755 if (curr->hardirq_threaded || curr->irq_config)
4756 return LD_WAIT_CONFIG;
4757
4758 return LD_WAIT_SPIN;
4759 } else if (curr->softirq_context) {
4760 /*
4761 * Softirqs are always threaded.
4762 */
4763 return LD_WAIT_CONFIG;
4764 }
4765
4766 return LD_WAIT_MAX;
4767 }
4768
4769 static int
print_lock_invalid_wait_context(struct task_struct * curr,struct held_lock * hlock)4770 print_lock_invalid_wait_context(struct task_struct *curr,
4771 struct held_lock *hlock)
4772 {
4773 short curr_inner;
4774
4775 if (!debug_locks_off())
4776 return 0;
4777 if (debug_locks_silent)
4778 return 0;
4779
4780 nbcon_cpu_emergency_enter();
4781
4782 pr_warn("\n");
4783 pr_warn("=============================\n");
4784 pr_warn("[ BUG: Invalid wait context ]\n");
4785 print_kernel_ident();
4786 pr_warn("-----------------------------\n");
4787
4788 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4789 print_lock(hlock);
4790
4791 pr_warn("other info that might help us debug this:\n");
4792
4793 curr_inner = task_wait_context(curr);
4794 pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
4795
4796 lockdep_print_held_locks(curr);
4797
4798 pr_warn("stack backtrace:\n");
4799 dump_stack();
4800
4801 nbcon_cpu_emergency_exit();
4802
4803 return 0;
4804 }
4805
4806 /*
4807 * Verify the wait_type context.
4808 *
4809 * This check validates we take locks in the right wait-type order; that is it
4810 * ensures that we do not take mutexes inside spinlocks and do not attempt to
4811 * acquire spinlocks inside raw_spinlocks and the sort.
4812 *
4813 * The entire thing is slightly more complex because of RCU, RCU is a lock that
4814 * can be taken from (pretty much) any context but also has constraints.
4815 * However when taken in a stricter environment the RCU lock does not loosen
4816 * the constraints.
4817 *
4818 * Therefore we must look for the strictest environment in the lock stack and
4819 * compare that to the lock we're trying to acquire.
4820 */
check_wait_context(struct task_struct * curr,struct held_lock * next)4821 static int check_wait_context(struct task_struct *curr, struct held_lock *next)
4822 {
4823 u8 next_inner = hlock_class(next)->wait_type_inner;
4824 u8 next_outer = hlock_class(next)->wait_type_outer;
4825 u8 curr_inner;
4826 int depth;
4827
4828 if (!next_inner || next->trylock)
4829 return 0;
4830
4831 if (!next_outer)
4832 next_outer = next_inner;
4833
4834 /*
4835 * Find start of current irq_context..
4836 */
4837 for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
4838 struct held_lock *prev = curr->held_locks + depth;
4839 if (prev->irq_context != next->irq_context)
4840 break;
4841 }
4842 depth++;
4843
4844 curr_inner = task_wait_context(curr);
4845
4846 for (; depth < curr->lockdep_depth; depth++) {
4847 struct held_lock *prev = curr->held_locks + depth;
4848 struct lock_class *class = hlock_class(prev);
4849 u8 prev_inner = class->wait_type_inner;
4850
4851 if (prev_inner) {
4852 /*
4853 * We can have a bigger inner than a previous one
4854 * when outer is smaller than inner, as with RCU.
4855 *
4856 * Also due to trylocks.
4857 */
4858 curr_inner = min(curr_inner, prev_inner);
4859
4860 /*
4861 * Allow override for annotations -- this is typically
4862 * only valid/needed for code that only exists when
4863 * CONFIG_PREEMPT_RT=n.
4864 */
4865 if (unlikely(class->lock_type == LD_LOCK_WAIT_OVERRIDE))
4866 curr_inner = prev_inner;
4867 }
4868 }
4869
4870 if (next_outer > curr_inner)
4871 return print_lock_invalid_wait_context(curr, next);
4872
4873 return 0;
4874 }
4875
4876 #else /* CONFIG_PROVE_LOCKING */
4877
4878 static inline int
mark_usage(struct task_struct * curr,struct held_lock * hlock,int check)4879 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4880 {
4881 return 1;
4882 }
4883
task_irq_context(struct task_struct * task)4884 static inline unsigned int task_irq_context(struct task_struct *task)
4885 {
4886 return 0;
4887 }
4888
separate_irq_context(struct task_struct * curr,struct held_lock * hlock)4889 static inline int separate_irq_context(struct task_struct *curr,
4890 struct held_lock *hlock)
4891 {
4892 return 0;
4893 }
4894
check_wait_context(struct task_struct * curr,struct held_lock * next)4895 static inline int check_wait_context(struct task_struct *curr,
4896 struct held_lock *next)
4897 {
4898 return 0;
4899 }
4900
4901 #endif /* CONFIG_PROVE_LOCKING */
4902
4903 /*
4904 * Initialize a lock instance's lock-class mapping info:
4905 */
lockdep_init_map_type(struct lockdep_map * lock,const char * name,struct lock_class_key * key,int subclass,u8 inner,u8 outer,u8 lock_type)4906 void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
4907 struct lock_class_key *key, int subclass,
4908 u8 inner, u8 outer, u8 lock_type)
4909 {
4910 int i;
4911
4912 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
4913 lock->class_cache[i] = NULL;
4914
4915 #ifdef CONFIG_LOCK_STAT
4916 lock->cpu = raw_smp_processor_id();
4917 #endif
4918
4919 /*
4920 * Can't be having no nameless bastards around this place!
4921 */
4922 if (DEBUG_LOCKS_WARN_ON(!name)) {
4923 lock->name = "NULL";
4924 return;
4925 }
4926
4927 lock->name = name;
4928
4929 lock->wait_type_outer = outer;
4930 lock->wait_type_inner = inner;
4931 lock->lock_type = lock_type;
4932
4933 /*
4934 * No key, no joy, we need to hash something.
4935 */
4936 if (DEBUG_LOCKS_WARN_ON(!key))
4937 return;
4938 /*
4939 * Sanity check, the lock-class key must either have been allocated
4940 * statically or must have been registered as a dynamic key.
4941 */
4942 if (!static_obj(key) && !is_dynamic_key(key)) {
4943 if (debug_locks)
4944 printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
4945 DEBUG_LOCKS_WARN_ON(1);
4946 return;
4947 }
4948 lock->key = key;
4949
4950 if (unlikely(!debug_locks))
4951 return;
4952
4953 if (subclass) {
4954 unsigned long flags;
4955
4956 if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
4957 return;
4958
4959 raw_local_irq_save(flags);
4960 lockdep_recursion_inc();
4961 register_lock_class(lock, subclass, 1);
4962 lockdep_recursion_finish();
4963 raw_local_irq_restore(flags);
4964 }
4965 }
4966 EXPORT_SYMBOL_GPL(lockdep_init_map_type);
4967
4968 struct lock_class_key __lockdep_no_validate__;
4969 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
4970
4971 struct lock_class_key __lockdep_no_track__;
4972 EXPORT_SYMBOL_GPL(__lockdep_no_track__);
4973
4974 #ifdef CONFIG_PROVE_LOCKING
lockdep_set_lock_cmp_fn(struct lockdep_map * lock,lock_cmp_fn cmp_fn,lock_print_fn print_fn)4975 void lockdep_set_lock_cmp_fn(struct lockdep_map *lock, lock_cmp_fn cmp_fn,
4976 lock_print_fn print_fn)
4977 {
4978 struct lock_class *class = lock->class_cache[0];
4979 unsigned long flags;
4980
4981 raw_local_irq_save(flags);
4982 lockdep_recursion_inc();
4983
4984 if (!class)
4985 class = register_lock_class(lock, 0, 0);
4986
4987 if (class) {
4988 WARN_ON(class->cmp_fn && class->cmp_fn != cmp_fn);
4989 WARN_ON(class->print_fn && class->print_fn != print_fn);
4990
4991 class->cmp_fn = cmp_fn;
4992 class->print_fn = print_fn;
4993 }
4994
4995 lockdep_recursion_finish();
4996 raw_local_irq_restore(flags);
4997 }
4998 EXPORT_SYMBOL_GPL(lockdep_set_lock_cmp_fn);
4999 #endif
5000
5001 static void
print_lock_nested_lock_not_held(struct task_struct * curr,struct held_lock * hlock)5002 print_lock_nested_lock_not_held(struct task_struct *curr,
5003 struct held_lock *hlock)
5004 {
5005 if (!debug_locks_off())
5006 return;
5007 if (debug_locks_silent)
5008 return;
5009
5010 nbcon_cpu_emergency_enter();
5011
5012 pr_warn("\n");
5013 pr_warn("==================================\n");
5014 pr_warn("WARNING: Nested lock was not taken\n");
5015 print_kernel_ident();
5016 pr_warn("----------------------------------\n");
5017
5018 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
5019 print_lock(hlock);
5020
5021 pr_warn("\nbut this task is not holding:\n");
5022 pr_warn("%s\n", hlock->nest_lock->name);
5023
5024 pr_warn("\nstack backtrace:\n");
5025 dump_stack();
5026
5027 pr_warn("\nother info that might help us debug this:\n");
5028 lockdep_print_held_locks(curr);
5029
5030 pr_warn("\nstack backtrace:\n");
5031 dump_stack();
5032
5033 nbcon_cpu_emergency_exit();
5034 }
5035
5036 static int __lock_is_held(const struct lockdep_map *lock, int read);
5037
5038 /*
5039 * This gets called for every mutex_lock*()/spin_lock*() operation.
5040 * We maintain the dependency maps and validate the locking attempt:
5041 *
5042 * The callers must make sure that IRQs are disabled before calling it,
5043 * otherwise we could get an interrupt which would want to take locks,
5044 * which would end up in lockdep again.
5045 */
__lock_acquire(struct lockdep_map * lock,unsigned int subclass,int trylock,int read,int check,int hardirqs_off,struct lockdep_map * nest_lock,unsigned long ip,int references,int pin_count,int sync)5046 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5047 int trylock, int read, int check, int hardirqs_off,
5048 struct lockdep_map *nest_lock, unsigned long ip,
5049 int references, int pin_count, int sync)
5050 {
5051 struct task_struct *curr = current;
5052 struct lock_class *class = NULL;
5053 struct held_lock *hlock;
5054 unsigned int depth;
5055 int chain_head = 0;
5056 int class_idx;
5057 u64 chain_key;
5058
5059 if (unlikely(!debug_locks))
5060 return 0;
5061
5062 if (unlikely(lock->key == &__lockdep_no_track__))
5063 return 0;
5064
5065 if (!prove_locking || lock->key == &__lockdep_no_validate__)
5066 check = 0;
5067
5068 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
5069 class = lock->class_cache[subclass];
5070 /*
5071 * Not cached?
5072 */
5073 if (unlikely(!class)) {
5074 class = register_lock_class(lock, subclass, 0);
5075 if (!class)
5076 return 0;
5077 }
5078
5079 debug_class_ops_inc(class);
5080
5081 if (very_verbose(class)) {
5082 nbcon_cpu_emergency_enter();
5083 printk("\nacquire class [%px] %s", class->key, class->name);
5084 if (class->name_version > 1)
5085 printk(KERN_CONT "#%d", class->name_version);
5086 printk(KERN_CONT "\n");
5087 dump_stack();
5088 nbcon_cpu_emergency_exit();
5089 }
5090
5091 /*
5092 * Add the lock to the list of currently held locks.
5093 * (we dont increase the depth just yet, up until the
5094 * dependency checks are done)
5095 */
5096 depth = curr->lockdep_depth;
5097 /*
5098 * Ran out of static storage for our per-task lock stack again have we?
5099 */
5100 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
5101 return 0;
5102
5103 class_idx = class - lock_classes;
5104
5105 if (depth && !sync) {
5106 /* we're holding locks and the new held lock is not a sync */
5107 hlock = curr->held_locks + depth - 1;
5108 if (hlock->class_idx == class_idx && nest_lock) {
5109 if (!references)
5110 references++;
5111
5112 if (!hlock->references)
5113 hlock->references++;
5114
5115 hlock->references += references;
5116
5117 /* Overflow */
5118 if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
5119 return 0;
5120
5121 return 2;
5122 }
5123 }
5124
5125 hlock = curr->held_locks + depth;
5126 /*
5127 * Plain impossible, we just registered it and checked it weren't no
5128 * NULL like.. I bet this mushroom I ate was good!
5129 */
5130 if (DEBUG_LOCKS_WARN_ON(!class))
5131 return 0;
5132 hlock->class_idx = class_idx;
5133 hlock->acquire_ip = ip;
5134 hlock->instance = lock;
5135 hlock->nest_lock = nest_lock;
5136 hlock->irq_context = task_irq_context(curr);
5137 hlock->trylock = trylock;
5138 hlock->read = read;
5139 hlock->check = check;
5140 hlock->sync = !!sync;
5141 hlock->hardirqs_off = !!hardirqs_off;
5142 hlock->references = references;
5143 #ifdef CONFIG_LOCK_STAT
5144 hlock->waittime_stamp = 0;
5145 hlock->holdtime_stamp = lockstat_clock();
5146 #endif
5147 hlock->pin_count = pin_count;
5148
5149 if (check_wait_context(curr, hlock))
5150 return 0;
5151
5152 /* Initialize the lock usage bit */
5153 if (!mark_usage(curr, hlock, check))
5154 return 0;
5155
5156 /*
5157 * Calculate the chain hash: it's the combined hash of all the
5158 * lock keys along the dependency chain. We save the hash value
5159 * at every step so that we can get the current hash easily
5160 * after unlock. The chain hash is then used to cache dependency
5161 * results.
5162 *
5163 * The 'key ID' is what is the most compact key value to drive
5164 * the hash, not class->key.
5165 */
5166 /*
5167 * Whoops, we did it again.. class_idx is invalid.
5168 */
5169 if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
5170 return 0;
5171
5172 chain_key = curr->curr_chain_key;
5173 if (!depth) {
5174 /*
5175 * How can we have a chain hash when we ain't got no keys?!
5176 */
5177 if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
5178 return 0;
5179 chain_head = 1;
5180 }
5181
5182 hlock->prev_chain_key = chain_key;
5183 if (separate_irq_context(curr, hlock)) {
5184 chain_key = INITIAL_CHAIN_KEY;
5185 chain_head = 1;
5186 }
5187 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
5188
5189 if (nest_lock && !__lock_is_held(nest_lock, -1)) {
5190 print_lock_nested_lock_not_held(curr, hlock);
5191 return 0;
5192 }
5193
5194 if (!debug_locks_silent) {
5195 WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
5196 WARN_ON_ONCE(!hlock_class(hlock)->key);
5197 }
5198
5199 if (!validate_chain(curr, hlock, chain_head, chain_key))
5200 return 0;
5201
5202 /* For lock_sync(), we are done here since no actual critical section */
5203 if (hlock->sync)
5204 return 1;
5205
5206 curr->curr_chain_key = chain_key;
5207 curr->lockdep_depth++;
5208 check_chain_key(curr);
5209 #ifdef CONFIG_DEBUG_LOCKDEP
5210 if (unlikely(!debug_locks))
5211 return 0;
5212 #endif
5213 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
5214 debug_locks_off();
5215 nbcon_cpu_emergency_enter();
5216 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
5217 printk(KERN_DEBUG "depth: %i max: %lu!\n",
5218 curr->lockdep_depth, MAX_LOCK_DEPTH);
5219
5220 lockdep_print_held_locks(current);
5221 debug_show_all_locks();
5222 dump_stack();
5223 nbcon_cpu_emergency_exit();
5224
5225 return 0;
5226 }
5227
5228 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
5229 max_lockdep_depth = curr->lockdep_depth;
5230
5231 return 1;
5232 }
5233
print_unlock_imbalance_bug(struct task_struct * curr,struct lockdep_map * lock,unsigned long ip)5234 static void print_unlock_imbalance_bug(struct task_struct *curr,
5235 struct lockdep_map *lock,
5236 unsigned long ip)
5237 {
5238 if (!debug_locks_off())
5239 return;
5240 if (debug_locks_silent)
5241 return;
5242
5243 nbcon_cpu_emergency_enter();
5244
5245 pr_warn("\n");
5246 pr_warn("=====================================\n");
5247 pr_warn("WARNING: bad unlock balance detected!\n");
5248 print_kernel_ident();
5249 pr_warn("-------------------------------------\n");
5250 pr_warn("%s/%d is trying to release lock (",
5251 curr->comm, task_pid_nr(curr));
5252 print_lockdep_cache(lock);
5253 pr_cont(") at:\n");
5254 print_ip_sym(KERN_WARNING, ip);
5255 pr_warn("but there are no more locks to release!\n");
5256 pr_warn("\nother info that might help us debug this:\n");
5257 lockdep_print_held_locks(curr);
5258
5259 pr_warn("\nstack backtrace:\n");
5260 dump_stack();
5261
5262 nbcon_cpu_emergency_exit();
5263 }
5264
match_held_lock(const struct held_lock * hlock,const struct lockdep_map * lock)5265 static noinstr int match_held_lock(const struct held_lock *hlock,
5266 const struct lockdep_map *lock)
5267 {
5268 if (hlock->instance == lock)
5269 return 1;
5270
5271 if (hlock->references) {
5272 const struct lock_class *class = lock->class_cache[0];
5273
5274 if (!class)
5275 class = look_up_lock_class(lock, 0);
5276
5277 /*
5278 * If look_up_lock_class() failed to find a class, we're trying
5279 * to test if we hold a lock that has never yet been acquired.
5280 * Clearly if the lock hasn't been acquired _ever_, we're not
5281 * holding it either, so report failure.
5282 */
5283 if (!class)
5284 return 0;
5285
5286 /*
5287 * References, but not a lock we're actually ref-counting?
5288 * State got messed up, follow the sites that change ->references
5289 * and try to make sense of it.
5290 */
5291 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
5292 return 0;
5293
5294 if (hlock->class_idx == class - lock_classes)
5295 return 1;
5296 }
5297
5298 return 0;
5299 }
5300
5301 /* @depth must not be zero */
find_held_lock(struct task_struct * curr,struct lockdep_map * lock,unsigned int depth,int * idx)5302 static struct held_lock *find_held_lock(struct task_struct *curr,
5303 struct lockdep_map *lock,
5304 unsigned int depth, int *idx)
5305 {
5306 struct held_lock *ret, *hlock, *prev_hlock;
5307 int i;
5308
5309 i = depth - 1;
5310 hlock = curr->held_locks + i;
5311 ret = hlock;
5312 if (match_held_lock(hlock, lock))
5313 goto out;
5314
5315 ret = NULL;
5316 for (i--, prev_hlock = hlock--;
5317 i >= 0;
5318 i--, prev_hlock = hlock--) {
5319 /*
5320 * We must not cross into another context:
5321 */
5322 if (prev_hlock->irq_context != hlock->irq_context) {
5323 ret = NULL;
5324 break;
5325 }
5326 if (match_held_lock(hlock, lock)) {
5327 ret = hlock;
5328 break;
5329 }
5330 }
5331
5332 out:
5333 *idx = i;
5334 return ret;
5335 }
5336
reacquire_held_locks(struct task_struct * curr,unsigned int depth,int idx,unsigned int * merged)5337 static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
5338 int idx, unsigned int *merged)
5339 {
5340 struct held_lock *hlock;
5341 int first_idx = idx;
5342
5343 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
5344 return 0;
5345
5346 for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
5347 switch (__lock_acquire(hlock->instance,
5348 hlock_class(hlock)->subclass,
5349 hlock->trylock,
5350 hlock->read, hlock->check,
5351 hlock->hardirqs_off,
5352 hlock->nest_lock, hlock->acquire_ip,
5353 hlock->references, hlock->pin_count, 0)) {
5354 case 0:
5355 return 1;
5356 case 1:
5357 break;
5358 case 2:
5359 *merged += (idx == first_idx);
5360 break;
5361 default:
5362 WARN_ON(1);
5363 return 0;
5364 }
5365 }
5366 return 0;
5367 }
5368
5369 static int
__lock_set_class(struct lockdep_map * lock,const char * name,struct lock_class_key * key,unsigned int subclass,unsigned long ip)5370 __lock_set_class(struct lockdep_map *lock, const char *name,
5371 struct lock_class_key *key, unsigned int subclass,
5372 unsigned long ip)
5373 {
5374 struct task_struct *curr = current;
5375 unsigned int depth, merged = 0;
5376 struct held_lock *hlock;
5377 struct lock_class *class;
5378 int i;
5379
5380 if (unlikely(!debug_locks))
5381 return 0;
5382
5383 depth = curr->lockdep_depth;
5384 /*
5385 * This function is about (re)setting the class of a held lock,
5386 * yet we're not actually holding any locks. Naughty user!
5387 */
5388 if (DEBUG_LOCKS_WARN_ON(!depth))
5389 return 0;
5390
5391 hlock = find_held_lock(curr, lock, depth, &i);
5392 if (!hlock) {
5393 print_unlock_imbalance_bug(curr, lock, ip);
5394 return 0;
5395 }
5396
5397 lockdep_init_map_type(lock, name, key, 0,
5398 lock->wait_type_inner,
5399 lock->wait_type_outer,
5400 lock->lock_type);
5401 class = register_lock_class(lock, subclass, 0);
5402 hlock->class_idx = class - lock_classes;
5403
5404 curr->lockdep_depth = i;
5405 curr->curr_chain_key = hlock->prev_chain_key;
5406
5407 if (reacquire_held_locks(curr, depth, i, &merged))
5408 return 0;
5409
5410 /*
5411 * I took it apart and put it back together again, except now I have
5412 * these 'spare' parts.. where shall I put them.
5413 */
5414 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
5415 return 0;
5416 return 1;
5417 }
5418
__lock_downgrade(struct lockdep_map * lock,unsigned long ip)5419 static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5420 {
5421 struct task_struct *curr = current;
5422 unsigned int depth, merged = 0;
5423 struct held_lock *hlock;
5424 int i;
5425
5426 if (unlikely(!debug_locks))
5427 return 0;
5428
5429 depth = curr->lockdep_depth;
5430 /*
5431 * This function is about (re)setting the class of a held lock,
5432 * yet we're not actually holding any locks. Naughty user!
5433 */
5434 if (DEBUG_LOCKS_WARN_ON(!depth))
5435 return 0;
5436
5437 hlock = find_held_lock(curr, lock, depth, &i);
5438 if (!hlock) {
5439 print_unlock_imbalance_bug(curr, lock, ip);
5440 return 0;
5441 }
5442
5443 curr->lockdep_depth = i;
5444 curr->curr_chain_key = hlock->prev_chain_key;
5445
5446 WARN(hlock->read, "downgrading a read lock");
5447 hlock->read = 1;
5448 hlock->acquire_ip = ip;
5449
5450 if (reacquire_held_locks(curr, depth, i, &merged))
5451 return 0;
5452
5453 /* Merging can't happen with unchanged classes.. */
5454 if (DEBUG_LOCKS_WARN_ON(merged))
5455 return 0;
5456
5457 /*
5458 * I took it apart and put it back together again, except now I have
5459 * these 'spare' parts.. where shall I put them.
5460 */
5461 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
5462 return 0;
5463
5464 return 1;
5465 }
5466
5467 /*
5468 * Remove the lock from the list of currently held locks - this gets
5469 * called on mutex_unlock()/spin_unlock*() (or on a failed
5470 * mutex_lock_interruptible()).
5471 */
5472 static int
__lock_release(struct lockdep_map * lock,unsigned long ip)5473 __lock_release(struct lockdep_map *lock, unsigned long ip)
5474 {
5475 struct task_struct *curr = current;
5476 unsigned int depth, merged = 1;
5477 struct held_lock *hlock;
5478 int i;
5479
5480 if (unlikely(!debug_locks))
5481 return 0;
5482
5483 depth = curr->lockdep_depth;
5484 /*
5485 * So we're all set to release this lock.. wait what lock? We don't
5486 * own any locks, you've been drinking again?
5487 */
5488 if (depth <= 0) {
5489 print_unlock_imbalance_bug(curr, lock, ip);
5490 return 0;
5491 }
5492
5493 /*
5494 * Check whether the lock exists in the current stack
5495 * of held locks:
5496 */
5497 hlock = find_held_lock(curr, lock, depth, &i);
5498 if (!hlock) {
5499 print_unlock_imbalance_bug(curr, lock, ip);
5500 return 0;
5501 }
5502
5503 if (hlock->instance == lock)
5504 lock_release_holdtime(hlock);
5505
5506 WARN(hlock->pin_count, "releasing a pinned lock\n");
5507
5508 if (hlock->references) {
5509 hlock->references--;
5510 if (hlock->references) {
5511 /*
5512 * We had, and after removing one, still have
5513 * references, the current lock stack is still
5514 * valid. We're done!
5515 */
5516 return 1;
5517 }
5518 }
5519
5520 /*
5521 * We have the right lock to unlock, 'hlock' points to it.
5522 * Now we remove it from the stack, and add back the other
5523 * entries (if any), recalculating the hash along the way:
5524 */
5525
5526 curr->lockdep_depth = i;
5527 curr->curr_chain_key = hlock->prev_chain_key;
5528
5529 /*
5530 * The most likely case is when the unlock is on the innermost
5531 * lock. In this case, we are done!
5532 */
5533 if (i == depth-1)
5534 return 1;
5535
5536 if (reacquire_held_locks(curr, depth, i + 1, &merged))
5537 return 0;
5538
5539 /*
5540 * We had N bottles of beer on the wall, we drank one, but now
5541 * there's not N-1 bottles of beer left on the wall...
5542 * Pouring two of the bottles together is acceptable.
5543 */
5544 DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
5545
5546 /*
5547 * Since reacquire_held_locks() would have called check_chain_key()
5548 * indirectly via __lock_acquire(), we don't need to do it again
5549 * on return.
5550 */
5551 return 0;
5552 }
5553
5554 static __always_inline
__lock_is_held(const struct lockdep_map * lock,int read)5555 int __lock_is_held(const struct lockdep_map *lock, int read)
5556 {
5557 struct task_struct *curr = current;
5558 int i;
5559
5560 for (i = 0; i < curr->lockdep_depth; i++) {
5561 struct held_lock *hlock = curr->held_locks + i;
5562
5563 if (match_held_lock(hlock, lock)) {
5564 if (read == -1 || !!hlock->read == read)
5565 return LOCK_STATE_HELD;
5566
5567 return LOCK_STATE_NOT_HELD;
5568 }
5569 }
5570
5571 return LOCK_STATE_NOT_HELD;
5572 }
5573
__lock_pin_lock(struct lockdep_map * lock)5574 static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
5575 {
5576 struct pin_cookie cookie = NIL_COOKIE;
5577 struct task_struct *curr = current;
5578 int i;
5579
5580 if (unlikely(!debug_locks))
5581 return cookie;
5582
5583 for (i = 0; i < curr->lockdep_depth; i++) {
5584 struct held_lock *hlock = curr->held_locks + i;
5585
5586 if (match_held_lock(hlock, lock)) {
5587 /*
5588 * Grab 16bits of randomness; this is sufficient to not
5589 * be guessable and still allows some pin nesting in
5590 * our u32 pin_count.
5591 */
5592 cookie.val = 1 + (sched_clock() & 0xffff);
5593 hlock->pin_count += cookie.val;
5594 return cookie;
5595 }
5596 }
5597
5598 WARN(1, "pinning an unheld lock\n");
5599 return cookie;
5600 }
5601
__lock_repin_lock(struct lockdep_map * lock,struct pin_cookie cookie)5602 static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5603 {
5604 struct task_struct *curr = current;
5605 int i;
5606
5607 if (unlikely(!debug_locks))
5608 return;
5609
5610 for (i = 0; i < curr->lockdep_depth; i++) {
5611 struct held_lock *hlock = curr->held_locks + i;
5612
5613 if (match_held_lock(hlock, lock)) {
5614 hlock->pin_count += cookie.val;
5615 return;
5616 }
5617 }
5618
5619 WARN(1, "pinning an unheld lock\n");
5620 }
5621
__lock_unpin_lock(struct lockdep_map * lock,struct pin_cookie cookie)5622 static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5623 {
5624 struct task_struct *curr = current;
5625 int i;
5626
5627 if (unlikely(!debug_locks))
5628 return;
5629
5630 for (i = 0; i < curr->lockdep_depth; i++) {
5631 struct held_lock *hlock = curr->held_locks + i;
5632
5633 if (match_held_lock(hlock, lock)) {
5634 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
5635 return;
5636
5637 hlock->pin_count -= cookie.val;
5638
5639 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
5640 hlock->pin_count = 0;
5641
5642 return;
5643 }
5644 }
5645
5646 WARN(1, "unpinning an unheld lock\n");
5647 }
5648
5649 /*
5650 * Check whether we follow the irq-flags state precisely:
5651 */
check_flags(unsigned long flags)5652 static noinstr void check_flags(unsigned long flags)
5653 {
5654 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
5655 if (!debug_locks)
5656 return;
5657
5658 /* Get the warning out.. */
5659 instrumentation_begin();
5660
5661 if (irqs_disabled_flags(flags)) {
5662 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
5663 printk("possible reason: unannotated irqs-off.\n");
5664 }
5665 } else {
5666 if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
5667 printk("possible reason: unannotated irqs-on.\n");
5668 }
5669 }
5670
5671 #ifndef CONFIG_PREEMPT_RT
5672 /*
5673 * We dont accurately track softirq state in e.g.
5674 * hardirq contexts (such as on 4KSTACKS), so only
5675 * check if not in hardirq contexts:
5676 */
5677 if (!hardirq_count()) {
5678 if (softirq_count()) {
5679 /* like the above, but with softirqs */
5680 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
5681 } else {
5682 /* lick the above, does it taste good? */
5683 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
5684 }
5685 }
5686 #endif
5687
5688 if (!debug_locks)
5689 print_irqtrace_events(current);
5690
5691 instrumentation_end();
5692 #endif
5693 }
5694
lock_set_class(struct lockdep_map * lock,const char * name,struct lock_class_key * key,unsigned int subclass,unsigned long ip)5695 void lock_set_class(struct lockdep_map *lock, const char *name,
5696 struct lock_class_key *key, unsigned int subclass,
5697 unsigned long ip)
5698 {
5699 unsigned long flags;
5700
5701 if (unlikely(!lockdep_enabled()))
5702 return;
5703
5704 raw_local_irq_save(flags);
5705 lockdep_recursion_inc();
5706 check_flags(flags);
5707 if (__lock_set_class(lock, name, key, subclass, ip))
5708 check_chain_key(current);
5709 lockdep_recursion_finish();
5710 raw_local_irq_restore(flags);
5711 }
5712 EXPORT_SYMBOL_GPL(lock_set_class);
5713
lock_downgrade(struct lockdep_map * lock,unsigned long ip)5714 void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5715 {
5716 unsigned long flags;
5717
5718 if (unlikely(!lockdep_enabled()))
5719 return;
5720
5721 raw_local_irq_save(flags);
5722 lockdep_recursion_inc();
5723 check_flags(flags);
5724 if (__lock_downgrade(lock, ip))
5725 check_chain_key(current);
5726 lockdep_recursion_finish();
5727 raw_local_irq_restore(flags);
5728 }
5729 EXPORT_SYMBOL_GPL(lock_downgrade);
5730
5731 /* NMI context !!! */
verify_lock_unused(struct lockdep_map * lock,struct held_lock * hlock,int subclass)5732 static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
5733 {
5734 #ifdef CONFIG_PROVE_LOCKING
5735 struct lock_class *class = look_up_lock_class(lock, subclass);
5736 unsigned long mask = LOCKF_USED;
5737
5738 /* if it doesn't have a class (yet), it certainly hasn't been used yet */
5739 if (!class)
5740 return;
5741
5742 /*
5743 * READ locks only conflict with USED, such that if we only ever use
5744 * READ locks, there is no deadlock possible -- RCU.
5745 */
5746 if (!hlock->read)
5747 mask |= LOCKF_USED_READ;
5748
5749 if (!(class->usage_mask & mask))
5750 return;
5751
5752 hlock->class_idx = class - lock_classes;
5753
5754 print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
5755 #endif
5756 }
5757
lockdep_nmi(void)5758 static bool lockdep_nmi(void)
5759 {
5760 if (raw_cpu_read(lockdep_recursion))
5761 return false;
5762
5763 if (!in_nmi())
5764 return false;
5765
5766 return true;
5767 }
5768
5769 /*
5770 * read_lock() is recursive if:
5771 * 1. We force lockdep think this way in selftests or
5772 * 2. The implementation is not queued read/write lock or
5773 * 3. The locker is at an in_interrupt() context.
5774 */
read_lock_is_recursive(void)5775 bool read_lock_is_recursive(void)
5776 {
5777 return force_read_lock_recursive ||
5778 !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
5779 in_interrupt();
5780 }
5781 EXPORT_SYMBOL_GPL(read_lock_is_recursive);
5782
5783 /*
5784 * We are not always called with irqs disabled - do that here,
5785 * and also avoid lockdep recursion:
5786 */
lock_acquire(struct lockdep_map * lock,unsigned int subclass,int trylock,int read,int check,struct lockdep_map * nest_lock,unsigned long ip)5787 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5788 int trylock, int read, int check,
5789 struct lockdep_map *nest_lock, unsigned long ip)
5790 {
5791 unsigned long flags;
5792
5793 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
5794
5795 if (!debug_locks)
5796 return;
5797
5798 if (unlikely(!lockdep_enabled())) {
5799 /* XXX allow trylock from NMI ?!? */
5800 if (lockdep_nmi() && !trylock) {
5801 struct held_lock hlock;
5802
5803 hlock.acquire_ip = ip;
5804 hlock.instance = lock;
5805 hlock.nest_lock = nest_lock;
5806 hlock.irq_context = 2; // XXX
5807 hlock.trylock = trylock;
5808 hlock.read = read;
5809 hlock.check = check;
5810 hlock.hardirqs_off = true;
5811 hlock.references = 0;
5812
5813 verify_lock_unused(lock, &hlock, subclass);
5814 }
5815 return;
5816 }
5817
5818 raw_local_irq_save(flags);
5819 check_flags(flags);
5820
5821 lockdep_recursion_inc();
5822 __lock_acquire(lock, subclass, trylock, read, check,
5823 irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 0);
5824 lockdep_recursion_finish();
5825 raw_local_irq_restore(flags);
5826 }
5827 EXPORT_SYMBOL_GPL(lock_acquire);
5828
lock_release(struct lockdep_map * lock,unsigned long ip)5829 void lock_release(struct lockdep_map *lock, unsigned long ip)
5830 {
5831 unsigned long flags;
5832
5833 trace_lock_release(lock, ip);
5834
5835 if (unlikely(!lockdep_enabled() ||
5836 lock->key == &__lockdep_no_track__))
5837 return;
5838
5839 raw_local_irq_save(flags);
5840 check_flags(flags);
5841
5842 lockdep_recursion_inc();
5843 if (__lock_release(lock, ip))
5844 check_chain_key(current);
5845 lockdep_recursion_finish();
5846 raw_local_irq_restore(flags);
5847 }
5848 EXPORT_SYMBOL_GPL(lock_release);
5849
5850 /*
5851 * lock_sync() - A special annotation for synchronize_{s,}rcu()-like API.
5852 *
5853 * No actual critical section is created by the APIs annotated with this: these
5854 * APIs are used to wait for one or multiple critical sections (on other CPUs
5855 * or threads), and it means that calling these APIs inside these critical
5856 * sections is potential deadlock.
5857 */
lock_sync(struct lockdep_map * lock,unsigned subclass,int read,int check,struct lockdep_map * nest_lock,unsigned long ip)5858 void lock_sync(struct lockdep_map *lock, unsigned subclass, int read,
5859 int check, struct lockdep_map *nest_lock, unsigned long ip)
5860 {
5861 unsigned long flags;
5862
5863 if (unlikely(!lockdep_enabled()))
5864 return;
5865
5866 raw_local_irq_save(flags);
5867 check_flags(flags);
5868
5869 lockdep_recursion_inc();
5870 __lock_acquire(lock, subclass, 0, read, check,
5871 irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 1);
5872 check_chain_key(current);
5873 lockdep_recursion_finish();
5874 raw_local_irq_restore(flags);
5875 }
5876 EXPORT_SYMBOL_GPL(lock_sync);
5877
lock_is_held_type(const struct lockdep_map * lock,int read)5878 noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
5879 {
5880 unsigned long flags;
5881 int ret = LOCK_STATE_NOT_HELD;
5882
5883 /*
5884 * Avoid false negative lockdep_assert_held() and
5885 * lockdep_assert_not_held().
5886 */
5887 if (unlikely(!lockdep_enabled()))
5888 return LOCK_STATE_UNKNOWN;
5889
5890 raw_local_irq_save(flags);
5891 check_flags(flags);
5892
5893 lockdep_recursion_inc();
5894 ret = __lock_is_held(lock, read);
5895 lockdep_recursion_finish();
5896 raw_local_irq_restore(flags);
5897
5898 return ret;
5899 }
5900 EXPORT_SYMBOL_GPL(lock_is_held_type);
5901 NOKPROBE_SYMBOL(lock_is_held_type);
5902
lock_pin_lock(struct lockdep_map * lock)5903 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
5904 {
5905 struct pin_cookie cookie = NIL_COOKIE;
5906 unsigned long flags;
5907
5908 if (unlikely(!lockdep_enabled()))
5909 return cookie;
5910
5911 raw_local_irq_save(flags);
5912 check_flags(flags);
5913
5914 lockdep_recursion_inc();
5915 cookie = __lock_pin_lock(lock);
5916 lockdep_recursion_finish();
5917 raw_local_irq_restore(flags);
5918
5919 return cookie;
5920 }
5921 EXPORT_SYMBOL_GPL(lock_pin_lock);
5922
lock_repin_lock(struct lockdep_map * lock,struct pin_cookie cookie)5923 void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5924 {
5925 unsigned long flags;
5926
5927 if (unlikely(!lockdep_enabled()))
5928 return;
5929
5930 raw_local_irq_save(flags);
5931 check_flags(flags);
5932
5933 lockdep_recursion_inc();
5934 __lock_repin_lock(lock, cookie);
5935 lockdep_recursion_finish();
5936 raw_local_irq_restore(flags);
5937 }
5938 EXPORT_SYMBOL_GPL(lock_repin_lock);
5939
lock_unpin_lock(struct lockdep_map * lock,struct pin_cookie cookie)5940 void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5941 {
5942 unsigned long flags;
5943
5944 if (unlikely(!lockdep_enabled()))
5945 return;
5946
5947 raw_local_irq_save(flags);
5948 check_flags(flags);
5949
5950 lockdep_recursion_inc();
5951 __lock_unpin_lock(lock, cookie);
5952 lockdep_recursion_finish();
5953 raw_local_irq_restore(flags);
5954 }
5955 EXPORT_SYMBOL_GPL(lock_unpin_lock);
5956
5957 #ifdef CONFIG_LOCK_STAT
print_lock_contention_bug(struct task_struct * curr,struct lockdep_map * lock,unsigned long ip)5958 static void print_lock_contention_bug(struct task_struct *curr,
5959 struct lockdep_map *lock,
5960 unsigned long ip)
5961 {
5962 if (!debug_locks_off())
5963 return;
5964 if (debug_locks_silent)
5965 return;
5966
5967 nbcon_cpu_emergency_enter();
5968
5969 pr_warn("\n");
5970 pr_warn("=================================\n");
5971 pr_warn("WARNING: bad contention detected!\n");
5972 print_kernel_ident();
5973 pr_warn("---------------------------------\n");
5974 pr_warn("%s/%d is trying to contend lock (",
5975 curr->comm, task_pid_nr(curr));
5976 print_lockdep_cache(lock);
5977 pr_cont(") at:\n");
5978 print_ip_sym(KERN_WARNING, ip);
5979 pr_warn("but there are no locks held!\n");
5980 pr_warn("\nother info that might help us debug this:\n");
5981 lockdep_print_held_locks(curr);
5982
5983 pr_warn("\nstack backtrace:\n");
5984 dump_stack();
5985
5986 nbcon_cpu_emergency_exit();
5987 }
5988
5989 static void
__lock_contended(struct lockdep_map * lock,unsigned long ip)5990 __lock_contended(struct lockdep_map *lock, unsigned long ip)
5991 {
5992 struct task_struct *curr = current;
5993 struct held_lock *hlock;
5994 struct lock_class_stats *stats;
5995 unsigned int depth;
5996 int i, contention_point, contending_point;
5997
5998 depth = curr->lockdep_depth;
5999 /*
6000 * Whee, we contended on this lock, except it seems we're not
6001 * actually trying to acquire anything much at all..
6002 */
6003 if (DEBUG_LOCKS_WARN_ON(!depth))
6004 return;
6005
6006 if (unlikely(lock->key == &__lockdep_no_track__))
6007 return;
6008
6009 hlock = find_held_lock(curr, lock, depth, &i);
6010 if (!hlock) {
6011 print_lock_contention_bug(curr, lock, ip);
6012 return;
6013 }
6014
6015 if (hlock->instance != lock)
6016 return;
6017
6018 hlock->waittime_stamp = lockstat_clock();
6019
6020 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
6021 contending_point = lock_point(hlock_class(hlock)->contending_point,
6022 lock->ip);
6023
6024 stats = get_lock_stats(hlock_class(hlock));
6025 if (contention_point < LOCKSTAT_POINTS)
6026 stats->contention_point[contention_point]++;
6027 if (contending_point < LOCKSTAT_POINTS)
6028 stats->contending_point[contending_point]++;
6029 if (lock->cpu != smp_processor_id())
6030 stats->bounces[bounce_contended + !!hlock->read]++;
6031 }
6032
6033 static void
__lock_acquired(struct lockdep_map * lock,unsigned long ip)6034 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
6035 {
6036 struct task_struct *curr = current;
6037 struct held_lock *hlock;
6038 struct lock_class_stats *stats;
6039 unsigned int depth;
6040 u64 now, waittime = 0;
6041 int i, cpu;
6042
6043 depth = curr->lockdep_depth;
6044 /*
6045 * Yay, we acquired ownership of this lock we didn't try to
6046 * acquire, how the heck did that happen?
6047 */
6048 if (DEBUG_LOCKS_WARN_ON(!depth))
6049 return;
6050
6051 if (unlikely(lock->key == &__lockdep_no_track__))
6052 return;
6053
6054 hlock = find_held_lock(curr, lock, depth, &i);
6055 if (!hlock) {
6056 print_lock_contention_bug(curr, lock, _RET_IP_);
6057 return;
6058 }
6059
6060 if (hlock->instance != lock)
6061 return;
6062
6063 cpu = smp_processor_id();
6064 if (hlock->waittime_stamp) {
6065 now = lockstat_clock();
6066 waittime = now - hlock->waittime_stamp;
6067 hlock->holdtime_stamp = now;
6068 }
6069
6070 stats = get_lock_stats(hlock_class(hlock));
6071 if (waittime) {
6072 if (hlock->read)
6073 lock_time_inc(&stats->read_waittime, waittime);
6074 else
6075 lock_time_inc(&stats->write_waittime, waittime);
6076 }
6077 if (lock->cpu != cpu)
6078 stats->bounces[bounce_acquired + !!hlock->read]++;
6079
6080 lock->cpu = cpu;
6081 lock->ip = ip;
6082 }
6083
lock_contended(struct lockdep_map * lock,unsigned long ip)6084 void lock_contended(struct lockdep_map *lock, unsigned long ip)
6085 {
6086 unsigned long flags;
6087
6088 trace_lock_contended(lock, ip);
6089
6090 if (unlikely(!lock_stat || !lockdep_enabled()))
6091 return;
6092
6093 raw_local_irq_save(flags);
6094 check_flags(flags);
6095 lockdep_recursion_inc();
6096 __lock_contended(lock, ip);
6097 lockdep_recursion_finish();
6098 raw_local_irq_restore(flags);
6099 }
6100 EXPORT_SYMBOL_GPL(lock_contended);
6101
lock_acquired(struct lockdep_map * lock,unsigned long ip)6102 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
6103 {
6104 unsigned long flags;
6105
6106 trace_lock_acquired(lock, ip);
6107
6108 if (unlikely(!lock_stat || !lockdep_enabled()))
6109 return;
6110
6111 raw_local_irq_save(flags);
6112 check_flags(flags);
6113 lockdep_recursion_inc();
6114 __lock_acquired(lock, ip);
6115 lockdep_recursion_finish();
6116 raw_local_irq_restore(flags);
6117 }
6118 EXPORT_SYMBOL_GPL(lock_acquired);
6119 #endif
6120
6121 /*
6122 * Used by the testsuite, sanitize the validator state
6123 * after a simulated failure:
6124 */
6125
lockdep_reset(void)6126 void lockdep_reset(void)
6127 {
6128 unsigned long flags;
6129 int i;
6130
6131 raw_local_irq_save(flags);
6132 lockdep_init_task(current);
6133 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
6134 nr_hardirq_chains = 0;
6135 nr_softirq_chains = 0;
6136 nr_process_chains = 0;
6137 debug_locks = 1;
6138 for (i = 0; i < CHAINHASH_SIZE; i++)
6139 INIT_HLIST_HEAD(chainhash_table + i);
6140 raw_local_irq_restore(flags);
6141 }
6142
6143 /* Remove a class from a lock chain. Must be called with the graph lock held. */
remove_class_from_lock_chain(struct pending_free * pf,struct lock_chain * chain,struct lock_class * class)6144 static void remove_class_from_lock_chain(struct pending_free *pf,
6145 struct lock_chain *chain,
6146 struct lock_class *class)
6147 {
6148 #ifdef CONFIG_PROVE_LOCKING
6149 int i;
6150
6151 for (i = chain->base; i < chain->base + chain->depth; i++) {
6152 if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
6153 continue;
6154 /*
6155 * Each lock class occurs at most once in a lock chain so once
6156 * we found a match we can break out of this loop.
6157 */
6158 goto free_lock_chain;
6159 }
6160 /* Since the chain has not been modified, return. */
6161 return;
6162
6163 free_lock_chain:
6164 free_chain_hlocks(chain->base, chain->depth);
6165 /* Overwrite the chain key for concurrent RCU readers. */
6166 WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
6167 dec_chains(chain->irq_context);
6168
6169 /*
6170 * Note: calling hlist_del_rcu() from inside a
6171 * hlist_for_each_entry_rcu() loop is safe.
6172 */
6173 hlist_del_rcu(&chain->entry);
6174 __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
6175 nr_zapped_lock_chains++;
6176 #endif
6177 }
6178
6179 /* Must be called with the graph lock held. */
remove_class_from_lock_chains(struct pending_free * pf,struct lock_class * class)6180 static void remove_class_from_lock_chains(struct pending_free *pf,
6181 struct lock_class *class)
6182 {
6183 struct lock_chain *chain;
6184 struct hlist_head *head;
6185 int i;
6186
6187 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
6188 head = chainhash_table + i;
6189 hlist_for_each_entry_rcu(chain, head, entry) {
6190 remove_class_from_lock_chain(pf, chain, class);
6191 }
6192 }
6193 }
6194
6195 /*
6196 * Remove all references to a lock class. The caller must hold the graph lock.
6197 */
zap_class(struct pending_free * pf,struct lock_class * class)6198 static void zap_class(struct pending_free *pf, struct lock_class *class)
6199 {
6200 struct lock_list *entry;
6201 int i;
6202
6203 WARN_ON_ONCE(!class->key);
6204
6205 /*
6206 * Remove all dependencies this lock is
6207 * involved in:
6208 */
6209 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
6210 entry = list_entries + i;
6211 if (entry->class != class && entry->links_to != class)
6212 continue;
6213 __clear_bit(i, list_entries_in_use);
6214 nr_list_entries--;
6215 list_del_rcu(&entry->entry);
6216 }
6217 if (list_empty(&class->locks_after) &&
6218 list_empty(&class->locks_before)) {
6219 list_move_tail(&class->lock_entry, &pf->zapped);
6220 hlist_del_rcu(&class->hash_entry);
6221 WRITE_ONCE(class->key, NULL);
6222 WRITE_ONCE(class->name, NULL);
6223 nr_lock_classes--;
6224 __clear_bit(class - lock_classes, lock_classes_in_use);
6225 if (class - lock_classes == max_lock_class_idx)
6226 max_lock_class_idx--;
6227 } else {
6228 WARN_ONCE(true, "%s() failed for class %s\n", __func__,
6229 class->name);
6230 }
6231
6232 remove_class_from_lock_chains(pf, class);
6233 nr_zapped_classes++;
6234 }
6235
reinit_class(struct lock_class * class)6236 static void reinit_class(struct lock_class *class)
6237 {
6238 WARN_ON_ONCE(!class->lock_entry.next);
6239 WARN_ON_ONCE(!list_empty(&class->locks_after));
6240 WARN_ON_ONCE(!list_empty(&class->locks_before));
6241 memset_startat(class, 0, key);
6242 WARN_ON_ONCE(!class->lock_entry.next);
6243 WARN_ON_ONCE(!list_empty(&class->locks_after));
6244 WARN_ON_ONCE(!list_empty(&class->locks_before));
6245 }
6246
within(const void * addr,void * start,unsigned long size)6247 static inline int within(const void *addr, void *start, unsigned long size)
6248 {
6249 return addr >= start && addr < start + size;
6250 }
6251
inside_selftest(void)6252 static bool inside_selftest(void)
6253 {
6254 return current == lockdep_selftest_task_struct;
6255 }
6256
6257 /* The caller must hold the graph lock. */
get_pending_free(void)6258 static struct pending_free *get_pending_free(void)
6259 {
6260 return delayed_free.pf + delayed_free.index;
6261 }
6262
6263 static void free_zapped_rcu(struct rcu_head *cb);
6264
6265 /*
6266 * Schedule an RCU callback if no RCU callback is pending. Must be called with
6267 * the graph lock held.
6268 */
call_rcu_zapped(struct pending_free * pf)6269 static void call_rcu_zapped(struct pending_free *pf)
6270 {
6271 WARN_ON_ONCE(inside_selftest());
6272
6273 if (list_empty(&pf->zapped))
6274 return;
6275
6276 if (delayed_free.scheduled)
6277 return;
6278
6279 delayed_free.scheduled = true;
6280
6281 WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
6282 delayed_free.index ^= 1;
6283
6284 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6285 }
6286
6287 /* The caller must hold the graph lock. May be called from RCU context. */
__free_zapped_classes(struct pending_free * pf)6288 static void __free_zapped_classes(struct pending_free *pf)
6289 {
6290 struct lock_class *class;
6291
6292 check_data_structures();
6293
6294 list_for_each_entry(class, &pf->zapped, lock_entry)
6295 reinit_class(class);
6296
6297 list_splice_init(&pf->zapped, &free_lock_classes);
6298
6299 #ifdef CONFIG_PROVE_LOCKING
6300 bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
6301 pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
6302 bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
6303 #endif
6304 }
6305
free_zapped_rcu(struct rcu_head * ch)6306 static void free_zapped_rcu(struct rcu_head *ch)
6307 {
6308 struct pending_free *pf;
6309 unsigned long flags;
6310
6311 if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
6312 return;
6313
6314 raw_local_irq_save(flags);
6315 lockdep_lock();
6316
6317 /* closed head */
6318 pf = delayed_free.pf + (delayed_free.index ^ 1);
6319 __free_zapped_classes(pf);
6320 delayed_free.scheduled = false;
6321
6322 /*
6323 * If there's anything on the open list, close and start a new callback.
6324 */
6325 call_rcu_zapped(delayed_free.pf + delayed_free.index);
6326
6327 lockdep_unlock();
6328 raw_local_irq_restore(flags);
6329 }
6330
6331 /*
6332 * Remove all lock classes from the class hash table and from the
6333 * all_lock_classes list whose key or name is in the address range [start,
6334 * start + size). Move these lock classes to the zapped_classes list. Must
6335 * be called with the graph lock held.
6336 */
__lockdep_free_key_range(struct pending_free * pf,void * start,unsigned long size)6337 static void __lockdep_free_key_range(struct pending_free *pf, void *start,
6338 unsigned long size)
6339 {
6340 struct lock_class *class;
6341 struct hlist_head *head;
6342 int i;
6343
6344 /* Unhash all classes that were created by a module. */
6345 for (i = 0; i < CLASSHASH_SIZE; i++) {
6346 head = classhash_table + i;
6347 hlist_for_each_entry_rcu(class, head, hash_entry) {
6348 if (!within(class->key, start, size) &&
6349 !within(class->name, start, size))
6350 continue;
6351 zap_class(pf, class);
6352 }
6353 }
6354 }
6355
6356 /*
6357 * Used in module.c to remove lock classes from memory that is going to be
6358 * freed; and possibly re-used by other modules.
6359 *
6360 * We will have had one synchronize_rcu() before getting here, so we're
6361 * guaranteed nobody will look up these exact classes -- they're properly dead
6362 * but still allocated.
6363 */
lockdep_free_key_range_reg(void * start,unsigned long size)6364 static void lockdep_free_key_range_reg(void *start, unsigned long size)
6365 {
6366 struct pending_free *pf;
6367 unsigned long flags;
6368
6369 init_data_structures_once();
6370
6371 raw_local_irq_save(flags);
6372 lockdep_lock();
6373 pf = get_pending_free();
6374 __lockdep_free_key_range(pf, start, size);
6375 call_rcu_zapped(pf);
6376 lockdep_unlock();
6377 raw_local_irq_restore(flags);
6378
6379 /*
6380 * Wait for any possible iterators from look_up_lock_class() to pass
6381 * before continuing to free the memory they refer to.
6382 */
6383 synchronize_rcu();
6384 }
6385
6386 /*
6387 * Free all lockdep keys in the range [start, start+size). Does not sleep.
6388 * Ignores debug_locks. Must only be used by the lockdep selftests.
6389 */
lockdep_free_key_range_imm(void * start,unsigned long size)6390 static void lockdep_free_key_range_imm(void *start, unsigned long size)
6391 {
6392 struct pending_free *pf = delayed_free.pf;
6393 unsigned long flags;
6394
6395 init_data_structures_once();
6396
6397 raw_local_irq_save(flags);
6398 lockdep_lock();
6399 __lockdep_free_key_range(pf, start, size);
6400 __free_zapped_classes(pf);
6401 lockdep_unlock();
6402 raw_local_irq_restore(flags);
6403 }
6404
lockdep_free_key_range(void * start,unsigned long size)6405 void lockdep_free_key_range(void *start, unsigned long size)
6406 {
6407 init_data_structures_once();
6408
6409 if (inside_selftest())
6410 lockdep_free_key_range_imm(start, size);
6411 else
6412 lockdep_free_key_range_reg(start, size);
6413 }
6414
6415 /*
6416 * Check whether any element of the @lock->class_cache[] array refers to a
6417 * registered lock class. The caller must hold either the graph lock or the
6418 * RCU read lock.
6419 */
lock_class_cache_is_registered(struct lockdep_map * lock)6420 static bool lock_class_cache_is_registered(struct lockdep_map *lock)
6421 {
6422 struct lock_class *class;
6423 struct hlist_head *head;
6424 int i, j;
6425
6426 for (i = 0; i < CLASSHASH_SIZE; i++) {
6427 head = classhash_table + i;
6428 hlist_for_each_entry_rcu(class, head, hash_entry) {
6429 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
6430 if (lock->class_cache[j] == class)
6431 return true;
6432 }
6433 }
6434 return false;
6435 }
6436
6437 /* The caller must hold the graph lock. Does not sleep. */
__lockdep_reset_lock(struct pending_free * pf,struct lockdep_map * lock)6438 static void __lockdep_reset_lock(struct pending_free *pf,
6439 struct lockdep_map *lock)
6440 {
6441 struct lock_class *class;
6442 int j;
6443
6444 /*
6445 * Remove all classes this lock might have:
6446 */
6447 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
6448 /*
6449 * If the class exists we look it up and zap it:
6450 */
6451 class = look_up_lock_class(lock, j);
6452 if (class)
6453 zap_class(pf, class);
6454 }
6455 /*
6456 * Debug check: in the end all mapped classes should
6457 * be gone.
6458 */
6459 if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
6460 debug_locks_off();
6461 }
6462
6463 /*
6464 * Remove all information lockdep has about a lock if debug_locks == 1. Free
6465 * released data structures from RCU context.
6466 */
lockdep_reset_lock_reg(struct lockdep_map * lock)6467 static void lockdep_reset_lock_reg(struct lockdep_map *lock)
6468 {
6469 struct pending_free *pf;
6470 unsigned long flags;
6471 int locked;
6472
6473 raw_local_irq_save(flags);
6474 locked = graph_lock();
6475 if (!locked)
6476 goto out_irq;
6477
6478 pf = get_pending_free();
6479 __lockdep_reset_lock(pf, lock);
6480 call_rcu_zapped(pf);
6481
6482 graph_unlock();
6483 out_irq:
6484 raw_local_irq_restore(flags);
6485 }
6486
6487 /*
6488 * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
6489 * lockdep selftests.
6490 */
lockdep_reset_lock_imm(struct lockdep_map * lock)6491 static void lockdep_reset_lock_imm(struct lockdep_map *lock)
6492 {
6493 struct pending_free *pf = delayed_free.pf;
6494 unsigned long flags;
6495
6496 raw_local_irq_save(flags);
6497 lockdep_lock();
6498 __lockdep_reset_lock(pf, lock);
6499 __free_zapped_classes(pf);
6500 lockdep_unlock();
6501 raw_local_irq_restore(flags);
6502 }
6503
lockdep_reset_lock(struct lockdep_map * lock)6504 void lockdep_reset_lock(struct lockdep_map *lock)
6505 {
6506 init_data_structures_once();
6507
6508 if (inside_selftest())
6509 lockdep_reset_lock_imm(lock);
6510 else
6511 lockdep_reset_lock_reg(lock);
6512 }
6513
6514 /*
6515 * Unregister a dynamically allocated key.
6516 *
6517 * Unlike lockdep_register_key(), a search is always done to find a matching
6518 * key irrespective of debug_locks to avoid potential invalid access to freed
6519 * memory in lock_class entry.
6520 */
lockdep_unregister_key(struct lock_class_key * key)6521 void lockdep_unregister_key(struct lock_class_key *key)
6522 {
6523 struct hlist_head *hash_head = keyhashentry(key);
6524 struct lock_class_key *k;
6525 struct pending_free *pf;
6526 unsigned long flags;
6527 bool found = false;
6528
6529 might_sleep();
6530
6531 if (WARN_ON_ONCE(static_obj(key)))
6532 return;
6533
6534 raw_local_irq_save(flags);
6535 lockdep_lock();
6536
6537 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
6538 if (k == key) {
6539 hlist_del_rcu(&k->hash_entry);
6540 found = true;
6541 break;
6542 }
6543 }
6544 WARN_ON_ONCE(!found && debug_locks);
6545 if (found) {
6546 pf = get_pending_free();
6547 __lockdep_free_key_range(pf, key, 1);
6548 call_rcu_zapped(pf);
6549 }
6550 lockdep_unlock();
6551 raw_local_irq_restore(flags);
6552
6553 /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
6554 synchronize_rcu();
6555 }
6556 EXPORT_SYMBOL_GPL(lockdep_unregister_key);
6557
lockdep_init(void)6558 void __init lockdep_init(void)
6559 {
6560 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
6561
6562 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
6563 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
6564 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
6565 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
6566 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
6567 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
6568 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
6569
6570 printk(" memory used by lock dependency info: %zu kB\n",
6571 (sizeof(lock_classes) +
6572 sizeof(lock_classes_in_use) +
6573 sizeof(classhash_table) +
6574 sizeof(list_entries) +
6575 sizeof(list_entries_in_use) +
6576 sizeof(chainhash_table) +
6577 sizeof(delayed_free)
6578 #ifdef CONFIG_PROVE_LOCKING
6579 + sizeof(lock_cq)
6580 + sizeof(lock_chains)
6581 + sizeof(lock_chains_in_use)
6582 + sizeof(chain_hlocks)
6583 #endif
6584 ) / 1024
6585 );
6586
6587 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
6588 printk(" memory used for stack traces: %zu kB\n",
6589 (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
6590 );
6591 #endif
6592
6593 printk(" per task-struct memory footprint: %zu bytes\n",
6594 sizeof(((struct task_struct *)NULL)->held_locks));
6595 }
6596
6597 static void
print_freed_lock_bug(struct task_struct * curr,const void * mem_from,const void * mem_to,struct held_lock * hlock)6598 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
6599 const void *mem_to, struct held_lock *hlock)
6600 {
6601 if (!debug_locks_off())
6602 return;
6603 if (debug_locks_silent)
6604 return;
6605
6606 nbcon_cpu_emergency_enter();
6607
6608 pr_warn("\n");
6609 pr_warn("=========================\n");
6610 pr_warn("WARNING: held lock freed!\n");
6611 print_kernel_ident();
6612 pr_warn("-------------------------\n");
6613 pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
6614 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
6615 print_lock(hlock);
6616 lockdep_print_held_locks(curr);
6617
6618 pr_warn("\nstack backtrace:\n");
6619 dump_stack();
6620
6621 nbcon_cpu_emergency_exit();
6622 }
6623
not_in_range(const void * mem_from,unsigned long mem_len,const void * lock_from,unsigned long lock_len)6624 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
6625 const void* lock_from, unsigned long lock_len)
6626 {
6627 return lock_from + lock_len <= mem_from ||
6628 mem_from + mem_len <= lock_from;
6629 }
6630
6631 /*
6632 * Called when kernel memory is freed (or unmapped), or if a lock
6633 * is destroyed or reinitialized - this code checks whether there is
6634 * any held lock in the memory range of <from> to <to>:
6635 */
debug_check_no_locks_freed(const void * mem_from,unsigned long mem_len)6636 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
6637 {
6638 struct task_struct *curr = current;
6639 struct held_lock *hlock;
6640 unsigned long flags;
6641 int i;
6642
6643 if (unlikely(!debug_locks))
6644 return;
6645
6646 raw_local_irq_save(flags);
6647 for (i = 0; i < curr->lockdep_depth; i++) {
6648 hlock = curr->held_locks + i;
6649
6650 if (not_in_range(mem_from, mem_len, hlock->instance,
6651 sizeof(*hlock->instance)))
6652 continue;
6653
6654 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
6655 break;
6656 }
6657 raw_local_irq_restore(flags);
6658 }
6659 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
6660
print_held_locks_bug(void)6661 static void print_held_locks_bug(void)
6662 {
6663 if (!debug_locks_off())
6664 return;
6665 if (debug_locks_silent)
6666 return;
6667
6668 nbcon_cpu_emergency_enter();
6669
6670 pr_warn("\n");
6671 pr_warn("====================================\n");
6672 pr_warn("WARNING: %s/%d still has locks held!\n",
6673 current->comm, task_pid_nr(current));
6674 print_kernel_ident();
6675 pr_warn("------------------------------------\n");
6676 lockdep_print_held_locks(current);
6677 pr_warn("\nstack backtrace:\n");
6678 dump_stack();
6679
6680 nbcon_cpu_emergency_exit();
6681 }
6682
debug_check_no_locks_held(void)6683 void debug_check_no_locks_held(void)
6684 {
6685 if (unlikely(current->lockdep_depth > 0))
6686 print_held_locks_bug();
6687 }
6688 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
6689
6690 #ifdef __KERNEL__
debug_show_all_locks(void)6691 void debug_show_all_locks(void)
6692 {
6693 struct task_struct *g, *p;
6694
6695 if (unlikely(!debug_locks)) {
6696 pr_warn("INFO: lockdep is turned off.\n");
6697 return;
6698 }
6699 pr_warn("\nShowing all locks held in the system:\n");
6700
6701 rcu_read_lock();
6702 for_each_process_thread(g, p) {
6703 if (!p->lockdep_depth)
6704 continue;
6705 lockdep_print_held_locks(p);
6706 touch_nmi_watchdog();
6707 touch_all_softlockup_watchdogs();
6708 }
6709 rcu_read_unlock();
6710
6711 pr_warn("\n");
6712 pr_warn("=============================================\n\n");
6713 }
6714 EXPORT_SYMBOL_GPL(debug_show_all_locks);
6715 #endif
6716
6717 /*
6718 * Careful: only use this function if you are sure that
6719 * the task cannot run in parallel!
6720 */
debug_show_held_locks(struct task_struct * task)6721 void debug_show_held_locks(struct task_struct *task)
6722 {
6723 if (unlikely(!debug_locks)) {
6724 printk("INFO: lockdep is turned off.\n");
6725 return;
6726 }
6727 lockdep_print_held_locks(task);
6728 }
6729 EXPORT_SYMBOL_GPL(debug_show_held_locks);
6730
lockdep_sys_exit(void)6731 asmlinkage __visible void lockdep_sys_exit(void)
6732 {
6733 struct task_struct *curr = current;
6734
6735 if (unlikely(curr->lockdep_depth)) {
6736 if (!debug_locks_off())
6737 return;
6738 nbcon_cpu_emergency_enter();
6739 pr_warn("\n");
6740 pr_warn("================================================\n");
6741 pr_warn("WARNING: lock held when returning to user space!\n");
6742 print_kernel_ident();
6743 pr_warn("------------------------------------------------\n");
6744 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
6745 curr->comm, curr->pid);
6746 lockdep_print_held_locks(curr);
6747 nbcon_cpu_emergency_exit();
6748 }
6749
6750 /*
6751 * The lock history for each syscall should be independent. So wipe the
6752 * slate clean on return to userspace.
6753 */
6754 lockdep_invariant_state(false);
6755 }
6756
lockdep_rcu_suspicious(const char * file,const int line,const char * s)6757 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
6758 {
6759 struct task_struct *curr = current;
6760 int dl = READ_ONCE(debug_locks);
6761 bool rcu = warn_rcu_enter();
6762
6763 /* Note: the following can be executed concurrently, so be careful. */
6764 nbcon_cpu_emergency_enter();
6765 pr_warn("\n");
6766 pr_warn("=============================\n");
6767 pr_warn("WARNING: suspicious RCU usage\n");
6768 print_kernel_ident();
6769 pr_warn("-----------------------------\n");
6770 pr_warn("%s:%d %s!\n", file, line, s);
6771 pr_warn("\nother info that might help us debug this:\n\n");
6772 pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s",
6773 !rcu_lockdep_current_cpu_online()
6774 ? "RCU used illegally from offline CPU!\n"
6775 : "",
6776 rcu_scheduler_active, dl,
6777 dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
6778
6779 /*
6780 * If a CPU is in the RCU-free window in idle (ie: in the section
6781 * between ct_idle_enter() and ct_idle_exit(), then RCU
6782 * considers that CPU to be in an "extended quiescent state",
6783 * which means that RCU will be completely ignoring that CPU.
6784 * Therefore, rcu_read_lock() and friends have absolutely no
6785 * effect on a CPU running in that state. In other words, even if
6786 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
6787 * delete data structures out from under it. RCU really has no
6788 * choice here: we need to keep an RCU-free window in idle where
6789 * the CPU may possibly enter into low power mode. This way we can
6790 * notice an extended quiescent state to other CPUs that started a grace
6791 * period. Otherwise we would delay any grace period as long as we run
6792 * in the idle task.
6793 *
6794 * So complain bitterly if someone does call rcu_read_lock(),
6795 * rcu_read_lock_bh() and so on from extended quiescent states.
6796 */
6797 if (!rcu_is_watching())
6798 pr_warn("RCU used illegally from extended quiescent state!\n");
6799
6800 lockdep_print_held_locks(curr);
6801 pr_warn("\nstack backtrace:\n");
6802 dump_stack();
6803 nbcon_cpu_emergency_exit();
6804 warn_rcu_exit(rcu);
6805 }
6806 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
6807