1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Berkeley Software Design Inc's name may not be used to endorse or
15 * promote products derived from this software without specific prior
16 * written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 *
30 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
31 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
32 */
33
34 /*
35 * Machine independent bits of mutex implementation.
36 */
37
38 #include <sys/cdefs.h>
39 #include "opt_adaptive_mutexes.h"
40 #include "opt_ddb.h"
41 #include "opt_hwpmc_hooks.h"
42 #include "opt_sched.h"
43
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/bus.h>
47 #include <sys/conf.h>
48 #include <sys/kdb.h>
49 #include <sys/kernel.h>
50 #include <sys/ktr.h>
51 #include <sys/lock.h>
52 #include <sys/malloc.h>
53 #include <sys/mutex.h>
54 #include <sys/proc.h>
55 #include <sys/resourcevar.h>
56 #include <sys/sched.h>
57 #include <sys/sbuf.h>
58 #include <sys/smp.h>
59 #include <sys/sysctl.h>
60 #include <sys/turnstile.h>
61 #include <sys/vmmeter.h>
62 #include <sys/lock_profile.h>
63
64 #include <machine/atomic.h>
65 #include <machine/bus.h>
66 #include <machine/cpu.h>
67
68 #include <ddb/ddb.h>
69
70 #include <fs/devfs/devfs_int.h>
71
72 #include <vm/vm.h>
73 #include <vm/vm_extern.h>
74
75 #if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
76 #define ADAPTIVE_MUTEXES
77 #endif
78
79 #ifdef HWPMC_HOOKS
80 #include <sys/pmckern.h>
81 PMC_SOFT_DEFINE( , , lock, failed);
82 #endif
83
84 /*
85 * Return the mutex address when the lock cookie address is provided.
86 * This functionality assumes that struct mtx* have a member named mtx_lock.
87 */
88 #define mtxlock2mtx(c) (__containerof(c, struct mtx, mtx_lock))
89
90 /*
91 * Internal utility macros.
92 */
93 #define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
94
95 #define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)
96
97 static void assert_mtx(const struct lock_object *lock, int what);
98 #ifdef DDB
99 static void db_show_mtx(const struct lock_object *lock);
100 #endif
101 static void lock_mtx(struct lock_object *lock, uintptr_t how);
102 static void lock_spin(struct lock_object *lock, uintptr_t how);
103 static int trylock_mtx(struct lock_object *lock, uintptr_t how);
104 static int trylock_spin(struct lock_object *lock, uintptr_t how);
105 #ifdef KDTRACE_HOOKS
106 static int owner_mtx(const struct lock_object *lock,
107 struct thread **owner);
108 #endif
109 static uintptr_t unlock_mtx(struct lock_object *lock);
110 static uintptr_t unlock_spin(struct lock_object *lock);
111
112 /*
113 * Lock classes for sleep and spin mutexes.
114 */
115 struct lock_class lock_class_mtx_sleep = {
116 .lc_name = "sleep mutex",
117 .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
118 .lc_assert = assert_mtx,
119 #ifdef DDB
120 .lc_ddb_show = db_show_mtx,
121 #endif
122 .lc_lock = lock_mtx,
123 .lc_trylock = trylock_mtx,
124 .lc_unlock = unlock_mtx,
125 #ifdef KDTRACE_HOOKS
126 .lc_owner = owner_mtx,
127 #endif
128 };
129 struct lock_class lock_class_mtx_spin = {
130 .lc_name = "spin mutex",
131 .lc_flags = LC_SPINLOCK | LC_RECURSABLE,
132 .lc_assert = assert_mtx,
133 #ifdef DDB
134 .lc_ddb_show = db_show_mtx,
135 #endif
136 .lc_lock = lock_spin,
137 .lc_trylock = trylock_spin,
138 .lc_unlock = unlock_spin,
139 #ifdef KDTRACE_HOOKS
140 .lc_owner = owner_mtx,
141 #endif
142 };
143
144 #ifdef ADAPTIVE_MUTEXES
145 #ifdef MUTEX_CUSTOM_BACKOFF
146 static SYSCTL_NODE(_debug, OID_AUTO, mtx, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
147 "mtx debugging");
148
149 static struct lock_delay_config __read_frequently mtx_delay;
150
151 SYSCTL_U16(_debug_mtx, OID_AUTO, delay_base, CTLFLAG_RW, &mtx_delay.base,
152 0, "");
153 SYSCTL_U16(_debug_mtx, OID_AUTO, delay_max, CTLFLAG_RW, &mtx_delay.max,
154 0, "");
155
156 LOCK_DELAY_SYSINIT_DEFAULT(mtx_delay);
157 #else
158 #define mtx_delay locks_delay
159 #endif
160 #endif
161
162 #ifdef MUTEX_SPIN_CUSTOM_BACKOFF
163 static SYSCTL_NODE(_debug, OID_AUTO, mtx_spin,
164 CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
165 "mtx spin debugging");
166
167 static struct lock_delay_config __read_frequently mtx_spin_delay;
168
169 SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_base, CTLFLAG_RW,
170 &mtx_spin_delay.base, 0, "");
171 SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_max, CTLFLAG_RW,
172 &mtx_spin_delay.max, 0, "");
173
174 LOCK_DELAY_SYSINIT_DEFAULT(mtx_spin_delay);
175 #else
176 #define mtx_spin_delay locks_delay
177 #endif
178
179 /*
180 * System-wide mutexes
181 */
182 struct mtx blocked_lock;
183 struct mtx __exclusive_cache_line Giant;
184
185 static void _mtx_lock_indefinite_check(struct mtx *, struct lock_delay_arg *);
186
187 static void
assert_mtx(const struct lock_object * lock,int what)188 assert_mtx(const struct lock_object *lock, int what)
189 {
190
191 /*
192 * Treat LA_LOCKED as if LA_XLOCKED was asserted.
193 *
194 * Some callers of lc_assert uses LA_LOCKED to indicate that either
195 * a shared lock or write lock was held, while other callers uses
196 * the more strict LA_XLOCKED (used as MA_OWNED).
197 *
198 * Mutex is the only lock class that can not be shared, as a result,
199 * we can reasonably consider the caller really intends to assert
200 * LA_XLOCKED when they are asserting LA_LOCKED on a mutex object.
201 */
202 if (what & LA_LOCKED) {
203 what &= ~LA_LOCKED;
204 what |= LA_XLOCKED;
205 }
206 mtx_assert((const struct mtx *)lock, what);
207 }
208
209 static void
lock_mtx(struct lock_object * lock,uintptr_t how)210 lock_mtx(struct lock_object *lock, uintptr_t how)
211 {
212
213 mtx_lock((struct mtx *)lock);
214 }
215
216 static void
lock_spin(struct lock_object * lock,uintptr_t how)217 lock_spin(struct lock_object *lock, uintptr_t how)
218 {
219
220 mtx_lock_spin((struct mtx *)lock);
221 }
222
223 static int
trylock_mtx(struct lock_object * lock,uintptr_t how)224 trylock_mtx(struct lock_object *lock, uintptr_t how)
225 {
226
227 return (mtx_trylock((struct mtx *)lock));
228 }
229
230 static int
trylock_spin(struct lock_object * lock,uintptr_t how)231 trylock_spin(struct lock_object *lock, uintptr_t how)
232 {
233
234 return (mtx_trylock_spin((struct mtx *)lock));
235 }
236
237 static uintptr_t
unlock_mtx(struct lock_object * lock)238 unlock_mtx(struct lock_object *lock)
239 {
240 struct mtx *m;
241
242 m = (struct mtx *)lock;
243 mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
244 mtx_unlock(m);
245 return (0);
246 }
247
248 static uintptr_t
unlock_spin(struct lock_object * lock)249 unlock_spin(struct lock_object *lock)
250 {
251 struct mtx *m;
252
253 m = (struct mtx *)lock;
254 mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
255 mtx_unlock_spin(m);
256 return (0);
257 }
258
259 #ifdef KDTRACE_HOOKS
260 static int
owner_mtx(const struct lock_object * lock,struct thread ** owner)261 owner_mtx(const struct lock_object *lock, struct thread **owner)
262 {
263 const struct mtx *m;
264 uintptr_t x;
265
266 m = (const struct mtx *)lock;
267 x = m->mtx_lock;
268 *owner = (struct thread *)(x & ~MTX_FLAGMASK);
269 return (*owner != NULL);
270 }
271 #endif
272
273 /*
274 * Function versions of the inlined __mtx_* macros. These are used by
275 * modules and can also be called from assembly language if needed.
276 */
277 void
__mtx_lock_flags(volatile uintptr_t * c,int opts,const char * file,int line)278 __mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
279 {
280 struct mtx *m;
281 uintptr_t tid, v;
282
283 m = mtxlock2mtx(c);
284
285 KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() ||
286 !TD_IS_IDLETHREAD(curthread),
287 ("mtx_lock() by idle thread %p on mutex %p @ %s:%d",
288 curthread, m, file, line));
289 KASSERT(m->mtx_lock != MTX_DESTROYED,
290 ("mtx_lock() of destroyed mutex %p @ %s:%d", m, file, line));
291 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_spin,
292 ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
293 file, line));
294 WITNESS_CHECKORDER(&m->lock_object, (opts & ~MTX_RECURSE) |
295 LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
296
297 tid = (uintptr_t)curthread;
298 v = MTX_UNOWNED;
299 if (!_mtx_obtain_lock_fetch(m, &v, tid))
300 _mtx_lock_sleep(m, v, opts, file, line);
301 else
302 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
303 m, 0, 0, file, line);
304 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
305 line);
306 WITNESS_LOCK(&m->lock_object, (opts & ~MTX_RECURSE) | LOP_EXCLUSIVE,
307 file, line);
308 TD_LOCKS_INC(curthread);
309 }
310
311 void
__mtx_unlock_flags(volatile uintptr_t * c,int opts,const char * file,int line)312 __mtx_unlock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
313 {
314 struct mtx *m;
315
316 m = mtxlock2mtx(c);
317
318 KASSERT(m->mtx_lock != MTX_DESTROYED,
319 ("mtx_unlock() of destroyed mutex %p @ %s:%d", m, file, line));
320 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_spin,
321 ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
322 file, line));
323 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
324 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
325 line);
326 mtx_assert(m, MA_OWNED);
327
328 #ifdef LOCK_PROFILING
329 __mtx_unlock_sleep(c, (uintptr_t)curthread, opts, file, line);
330 #else
331 __mtx_unlock(m, curthread, opts, file, line);
332 #endif
333 TD_LOCKS_DEC(curthread);
334 }
335
336 void
__mtx_lock_spin_flags(volatile uintptr_t * c,int opts,const char * file,int line)337 __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
338 int line)
339 {
340 struct mtx *m;
341 #ifdef SMP
342 uintptr_t tid, v;
343 #endif
344
345 m = mtxlock2mtx(c);
346
347 KASSERT(m->mtx_lock != MTX_DESTROYED,
348 ("mtx_lock_spin() of destroyed mutex %p @ %s:%d", m, file, line));
349 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_sleep,
350 ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
351 m->lock_object.lo_name, file, line));
352 if (mtx_owned(m))
353 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
354 (opts & MTX_RECURSE) != 0,
355 ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n",
356 m->lock_object.lo_name, file, line));
357 opts &= ~MTX_RECURSE;
358 WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
359 file, line, NULL);
360 #ifdef SMP
361 spinlock_enter();
362 tid = (uintptr_t)curthread;
363 v = MTX_UNOWNED;
364 if (!_mtx_obtain_lock_fetch(m, &v, tid))
365 _mtx_lock_spin(m, v, opts, file, line);
366 else
367 LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire,
368 m, 0, 0, file, line);
369 #else
370 __mtx_lock_spin(m, curthread, opts, file, line);
371 #endif
372 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
373 line);
374 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
375 }
376
377 int
__mtx_trylock_spin_flags(volatile uintptr_t * c,int opts,const char * file,int line)378 __mtx_trylock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
379 int line)
380 {
381 struct mtx *m;
382
383 if (SCHEDULER_STOPPED())
384 return (1);
385
386 m = mtxlock2mtx(c);
387
388 KASSERT(m->mtx_lock != MTX_DESTROYED,
389 ("mtx_trylock_spin() of destroyed mutex %p @ %s:%d", m, file,
390 line));
391 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_sleep,
392 ("mtx_trylock_spin() of sleep mutex %s @ %s:%d",
393 m->lock_object.lo_name, file, line));
394 KASSERT((opts & MTX_RECURSE) == 0,
395 ("mtx_trylock_spin: unsupp. opt MTX_RECURSE on mutex %s @ %s:%d\n",
396 m->lock_object.lo_name, file, line));
397 if (__mtx_trylock_spin(m, curthread, opts, file, line)) {
398 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 1, file, line);
399 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
400 return (1);
401 }
402 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 0, file, line);
403 return (0);
404 }
405
406 void
__mtx_unlock_spin_flags(volatile uintptr_t * c,int opts,const char * file,int line)407 __mtx_unlock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
408 int line)
409 {
410 struct mtx *m;
411
412 m = mtxlock2mtx(c);
413
414 KASSERT(m->mtx_lock != MTX_DESTROYED,
415 ("mtx_unlock_spin() of destroyed mutex %p @ %s:%d", m, file,
416 line));
417 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_sleep,
418 ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
419 m->lock_object.lo_name, file, line));
420 WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
421 LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
422 line);
423 mtx_assert(m, MA_OWNED);
424
425 __mtx_unlock_spin(m);
426 }
427
428 /*
429 * The important part of mtx_trylock{,_flags}()
430 * Tries to acquire lock `m.' If this function is called on a mutex that
431 * is already owned, it will recursively acquire the lock.
432 */
433 int
_mtx_trylock_flags_int(struct mtx * m,int opts LOCK_FILE_LINE_ARG_DEF)434 _mtx_trylock_flags_int(struct mtx *m, int opts LOCK_FILE_LINE_ARG_DEF)
435 {
436 struct thread *td;
437 uintptr_t tid, v;
438 #ifdef LOCK_PROFILING
439 uint64_t waittime = 0;
440 int contested = 0;
441 #endif
442 int rval;
443 bool recursed;
444
445 td = curthread;
446 tid = (uintptr_t)td;
447 if (SCHEDULER_STOPPED())
448 return (1);
449
450 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td),
451 ("mtx_trylock() by idle thread %p on mutex %p @ %s:%d",
452 curthread, m, file, line));
453 KASSERT(m->mtx_lock != MTX_DESTROYED,
454 ("mtx_trylock() of destroyed mutex %p @ %s:%d", m, file, line));
455 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_spin,
456 ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
457 file, line));
458
459 rval = 1;
460 recursed = false;
461 v = MTX_UNOWNED;
462 for (;;) {
463 if (_mtx_obtain_lock_fetch(m, &v, tid))
464 break;
465 if (v == MTX_UNOWNED)
466 continue;
467 if (v == tid &&
468 ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
469 (opts & MTX_RECURSE) != 0)) {
470 m->mtx_recurse++;
471 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
472 recursed = true;
473 break;
474 }
475 rval = 0;
476 break;
477 }
478
479 opts &= ~MTX_RECURSE;
480
481 LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
482 if (rval) {
483 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
484 file, line);
485 TD_LOCKS_INC(curthread);
486 if (!recursed)
487 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
488 m, contested, waittime, file, line);
489 }
490
491 return (rval);
492 }
493
494 int
_mtx_trylock_flags_(volatile uintptr_t * c,int opts,const char * file,int line)495 _mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file, int line)
496 {
497 struct mtx *m;
498
499 m = mtxlock2mtx(c);
500 return (_mtx_trylock_flags_int(m, opts LOCK_FILE_LINE_ARG));
501 }
502
503 /*
504 * __mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
505 *
506 * We call this if the lock is either contested (i.e. we need to go to
507 * sleep waiting for it), or if we need to recurse on it.
508 */
509 #if LOCK_DEBUG > 0
510 void
__mtx_lock_sleep(volatile uintptr_t * c,uintptr_t v,int opts,const char * file,int line)511 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, int opts, const char *file,
512 int line)
513 #else
514 void
515 __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v)
516 #endif
517 {
518 struct thread *td;
519 struct mtx *m;
520 struct turnstile *ts;
521 uintptr_t tid;
522 struct thread *owner;
523 #ifdef LOCK_PROFILING
524 int contested = 0;
525 uint64_t waittime = 0;
526 #endif
527 #if defined(ADAPTIVE_MUTEXES) || defined(KDTRACE_HOOKS)
528 struct lock_delay_arg lda;
529 #endif
530 #ifdef KDTRACE_HOOKS
531 u_int sleep_cnt = 0;
532 int64_t sleep_time = 0;
533 int64_t all_time = 0;
534 #endif
535 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
536 int doing_lockprof = 0;
537 #endif
538
539 td = curthread;
540 tid = (uintptr_t)td;
541 m = mtxlock2mtx(c);
542
543 #ifdef KDTRACE_HOOKS
544 if (LOCKSTAT_PROFILE_ENABLED(adaptive__acquire)) {
545 while (v == MTX_UNOWNED) {
546 if (_mtx_obtain_lock_fetch(m, &v, tid))
547 goto out_lockstat;
548 }
549 doing_lockprof = 1;
550 all_time -= lockstat_nsecs(&m->lock_object);
551 }
552 #endif
553 #ifdef LOCK_PROFILING
554 doing_lockprof = 1;
555 #endif
556
557 if (SCHEDULER_STOPPED())
558 return;
559
560 if (__predict_false(v == MTX_UNOWNED))
561 v = MTX_READ_VALUE(m);
562
563 if (__predict_false(lv_mtx_owner(v) == td)) {
564 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
565 (opts & MTX_RECURSE) != 0,
566 ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
567 m->lock_object.lo_name, file, line));
568 #if LOCK_DEBUG > 0
569 opts &= ~MTX_RECURSE;
570 #endif
571 m->mtx_recurse++;
572 atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
573 if (LOCK_LOG_TEST(&m->lock_object, opts))
574 CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
575 return;
576 }
577 #if LOCK_DEBUG > 0
578 opts &= ~MTX_RECURSE;
579 #endif
580
581 #if defined(ADAPTIVE_MUTEXES)
582 lock_delay_arg_init(&lda, &mtx_delay);
583 #elif defined(KDTRACE_HOOKS)
584 lock_delay_arg_init_noadapt(&lda);
585 #endif
586
587 #ifdef HWPMC_HOOKS
588 PMC_SOFT_CALL( , , lock, failed);
589 #endif
590 lock_profile_obtain_lock_failed(&m->lock_object, false,
591 &contested, &waittime);
592 if (LOCK_LOG_TEST(&m->lock_object, opts))
593 CTR4(KTR_LOCK,
594 "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
595 m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
596
597 THREAD_CONTENDS_ON_LOCK(&m->lock_object);
598
599 for (;;) {
600 if (v == MTX_UNOWNED) {
601 if (_mtx_obtain_lock_fetch(m, &v, tid))
602 break;
603 continue;
604 }
605 #ifdef KDTRACE_HOOKS
606 lda.spin_cnt++;
607 #endif
608 #ifdef ADAPTIVE_MUTEXES
609 /*
610 * If the owner is running on another CPU, spin until the
611 * owner stops running or the state of the lock changes.
612 */
613 owner = lv_mtx_owner(v);
614 if (TD_IS_RUNNING(owner)) {
615 if (LOCK_LOG_TEST(&m->lock_object, 0))
616 CTR3(KTR_LOCK,
617 "%s: spinning on %p held by %p",
618 __func__, m, owner);
619 KTR_STATE1(KTR_SCHED, "thread",
620 sched_tdname((struct thread *)tid),
621 "spinning", "lockname:\"%s\"",
622 m->lock_object.lo_name);
623 do {
624 lock_delay(&lda);
625 v = MTX_READ_VALUE(m);
626 owner = lv_mtx_owner(v);
627 } while (v != MTX_UNOWNED && TD_IS_RUNNING(owner));
628 KTR_STATE0(KTR_SCHED, "thread",
629 sched_tdname((struct thread *)tid),
630 "running");
631 continue;
632 }
633 #endif
634
635 ts = turnstile_trywait(&m->lock_object);
636 v = MTX_READ_VALUE(m);
637 retry_turnstile:
638
639 /*
640 * Check if the lock has been released while spinning for
641 * the turnstile chain lock.
642 */
643 if (v == MTX_UNOWNED) {
644 turnstile_cancel(ts);
645 continue;
646 }
647
648 #ifdef ADAPTIVE_MUTEXES
649 /*
650 * The current lock owner might have started executing
651 * on another CPU (or the lock could have changed
652 * owners) while we were waiting on the turnstile
653 * chain lock. If so, drop the turnstile lock and try
654 * again.
655 */
656 owner = lv_mtx_owner(v);
657 if (TD_IS_RUNNING(owner)) {
658 turnstile_cancel(ts);
659 continue;
660 }
661 #endif
662
663 /*
664 * If the mutex isn't already contested and a failure occurs
665 * setting the contested bit, the mutex was either released
666 * or the state of the MTX_RECURSED bit changed.
667 */
668 if ((v & MTX_CONTESTED) == 0 &&
669 !atomic_fcmpset_ptr(&m->mtx_lock, &v, v | MTX_CONTESTED)) {
670 goto retry_turnstile;
671 }
672
673 /*
674 * We definitely must sleep for this lock.
675 */
676 mtx_assert(m, MA_NOTOWNED);
677
678 /*
679 * Block on the turnstile.
680 */
681 #ifdef KDTRACE_HOOKS
682 sleep_time -= lockstat_nsecs(&m->lock_object);
683 #endif
684 #ifndef ADAPTIVE_MUTEXES
685 owner = mtx_owner(m);
686 #endif
687 MPASS(owner == mtx_owner(m));
688 turnstile_wait(ts, owner, TS_EXCLUSIVE_QUEUE);
689 #ifdef KDTRACE_HOOKS
690 sleep_time += lockstat_nsecs(&m->lock_object);
691 sleep_cnt++;
692 #endif
693 v = MTX_READ_VALUE(m);
694 }
695 THREAD_CONTENTION_DONE(&m->lock_object);
696 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
697 if (__predict_true(!doing_lockprof))
698 return;
699 #endif
700 #ifdef KDTRACE_HOOKS
701 all_time += lockstat_nsecs(&m->lock_object);
702 if (sleep_time)
703 LOCKSTAT_RECORD1(adaptive__block, m, sleep_time);
704
705 /*
706 * Only record the loops spinning and not sleeping.
707 */
708 if (lda.spin_cnt > sleep_cnt)
709 LOCKSTAT_RECORD1(adaptive__spin, m, all_time - sleep_time);
710 out_lockstat:
711 #endif
712 LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested,
713 waittime, file, line);
714 }
715
716 #ifdef SMP
717 /*
718 * _mtx_lock_spin_cookie: the tougher part of acquiring an MTX_SPIN lock.
719 *
720 * This is only called if we need to actually spin for the lock. Recursion
721 * is handled inline.
722 */
723 #if LOCK_DEBUG > 0
724 void
_mtx_lock_spin_cookie(volatile uintptr_t * c,uintptr_t v,int opts,const char * file,int line)725 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, int opts,
726 const char *file, int line)
727 #else
728 void
729 _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v)
730 #endif
731 {
732 struct mtx *m;
733 struct lock_delay_arg lda;
734 uintptr_t tid;
735 #ifdef LOCK_PROFILING
736 int contested = 0;
737 uint64_t waittime = 0;
738 #endif
739 #ifdef KDTRACE_HOOKS
740 int64_t spin_time = 0;
741 #endif
742 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
743 int doing_lockprof = 0;
744 #endif
745
746 tid = (uintptr_t)curthread;
747 m = mtxlock2mtx(c);
748
749 #ifdef KDTRACE_HOOKS
750 if (LOCKSTAT_PROFILE_ENABLED(adaptive__acquire)) {
751 while (v == MTX_UNOWNED) {
752 if (_mtx_obtain_lock_fetch(m, &v, tid))
753 goto out_lockstat;
754 }
755 doing_lockprof = 1;
756 spin_time -= lockstat_nsecs(&m->lock_object);
757 }
758 #endif
759 #ifdef LOCK_PROFILING
760 doing_lockprof = 1;
761 #endif
762
763 if (__predict_false(v == MTX_UNOWNED))
764 v = MTX_READ_VALUE(m);
765
766 if (__predict_false(v == tid)) {
767 m->mtx_recurse++;
768 return;
769 }
770
771 if (SCHEDULER_STOPPED())
772 return;
773
774 if (LOCK_LOG_TEST(&m->lock_object, opts))
775 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
776 KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
777 "spinning", "lockname:\"%s\"", m->lock_object.lo_name);
778
779 lock_delay_arg_init(&lda, &mtx_spin_delay);
780
781 #ifdef HWPMC_HOOKS
782 PMC_SOFT_CALL( , , lock, failed);
783 #endif
784 lock_profile_obtain_lock_failed(&m->lock_object, true, &contested, &waittime);
785
786 for (;;) {
787 if (v == MTX_UNOWNED) {
788 if (_mtx_obtain_lock_fetch(m, &v, tid))
789 break;
790 continue;
791 }
792 /* Give interrupts a chance while we spin. */
793 spinlock_exit();
794 do {
795 if (__predict_true(lda.spin_cnt < 10000000)) {
796 lock_delay(&lda);
797 } else {
798 _mtx_lock_indefinite_check(m, &lda);
799 }
800 v = MTX_READ_VALUE(m);
801 } while (v != MTX_UNOWNED);
802 spinlock_enter();
803 }
804
805 if (LOCK_LOG_TEST(&m->lock_object, opts))
806 CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
807 KTR_STATE0(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
808 "running");
809
810 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
811 if (__predict_true(!doing_lockprof))
812 return;
813 #endif
814 #ifdef KDTRACE_HOOKS
815 spin_time += lockstat_nsecs(&m->lock_object);
816 if (lda.spin_cnt != 0)
817 LOCKSTAT_RECORD1(spin__spin, m, spin_time);
818 out_lockstat:
819 #endif
820 LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire, m,
821 contested, waittime, file, line);
822 }
823 #endif /* SMP */
824
825 #ifdef INVARIANTS
826 static void
thread_lock_validate(struct mtx * m,int opts,const char * file,int line)827 thread_lock_validate(struct mtx *m, int opts, const char *file, int line)
828 {
829
830 KASSERT(m->mtx_lock != MTX_DESTROYED,
831 ("thread_lock() of destroyed mutex %p @ %s:%d", m, file, line));
832 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_sleep,
833 ("thread_lock() of sleep mutex %s @ %s:%d",
834 m->lock_object.lo_name, file, line));
835 KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) == 0,
836 ("thread_lock: got a recursive mutex %s @ %s:%d\n",
837 m->lock_object.lo_name, file, line));
838 WITNESS_CHECKORDER(&m->lock_object,
839 opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
840 }
841 #else
842 #define thread_lock_validate(m, opts, file, line) do { } while (0)
843 #endif
844
845 #ifndef LOCK_PROFILING
846 #if LOCK_DEBUG > 0
847 void
_thread_lock(struct thread * td,int opts,const char * file,int line)848 _thread_lock(struct thread *td, int opts, const char *file, int line)
849 #else
850 void
851 _thread_lock(struct thread *td)
852 #endif
853 {
854 struct mtx *m;
855 uintptr_t tid;
856
857 tid = (uintptr_t)curthread;
858
859 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(spin__acquire)))
860 goto slowpath_noirq;
861 spinlock_enter();
862 m = td->td_lock;
863 thread_lock_validate(m, 0, file, line);
864 if (__predict_false(m == &blocked_lock))
865 goto slowpath_unlocked;
866 if (__predict_false(!_mtx_obtain_lock(m, tid)))
867 goto slowpath_unlocked;
868 if (__predict_true(m == td->td_lock)) {
869 WITNESS_LOCK(&m->lock_object, LOP_EXCLUSIVE, file, line);
870 return;
871 }
872 _mtx_release_lock_quick(m);
873 slowpath_unlocked:
874 spinlock_exit();
875 slowpath_noirq:
876 #if LOCK_DEBUG > 0
877 thread_lock_flags_(td, opts, file, line);
878 #else
879 thread_lock_flags_(td, 0, 0, 0);
880 #endif
881 }
882 #endif
883
884 void
thread_lock_flags_(struct thread * td,int opts,const char * file,int line)885 thread_lock_flags_(struct thread *td, int opts, const char *file, int line)
886 {
887 struct mtx *m;
888 uintptr_t tid, v;
889 struct lock_delay_arg lda;
890 #ifdef LOCK_PROFILING
891 int contested = 0;
892 uint64_t waittime = 0;
893 #endif
894 #ifdef KDTRACE_HOOKS
895 int64_t spin_time = 0;
896 #endif
897 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
898 int doing_lockprof = 1;
899 #endif
900
901 tid = (uintptr_t)curthread;
902
903 if (SCHEDULER_STOPPED()) {
904 /*
905 * Ensure that spinlock sections are balanced even when the
906 * scheduler is stopped, since we may otherwise inadvertently
907 * re-enable interrupts while dumping core.
908 */
909 spinlock_enter();
910 return;
911 }
912
913 lock_delay_arg_init(&lda, &mtx_spin_delay);
914
915 #ifdef HWPMC_HOOKS
916 PMC_SOFT_CALL( , , lock, failed);
917 #endif
918
919 #ifdef LOCK_PROFILING
920 doing_lockprof = 1;
921 #elif defined(KDTRACE_HOOKS)
922 doing_lockprof = lockstat_enabled;
923 #endif
924 #ifdef KDTRACE_HOOKS
925 if (__predict_false(doing_lockprof))
926 spin_time -= lockstat_nsecs(&td->td_lock->lock_object);
927 #endif
928 spinlock_enter();
929
930 for (;;) {
931 retry:
932 m = td->td_lock;
933 thread_lock_validate(m, opts, file, line);
934 v = MTX_READ_VALUE(m);
935 for (;;) {
936 if (v == MTX_UNOWNED) {
937 if (_mtx_obtain_lock_fetch(m, &v, tid))
938 break;
939 continue;
940 }
941 MPASS(v != tid);
942 lock_profile_obtain_lock_failed(&m->lock_object, true,
943 &contested, &waittime);
944 /* Give interrupts a chance while we spin. */
945 spinlock_exit();
946 do {
947 if (__predict_true(lda.spin_cnt < 10000000)) {
948 lock_delay(&lda);
949 } else {
950 _mtx_lock_indefinite_check(m, &lda);
951 }
952 if (m != td->td_lock) {
953 spinlock_enter();
954 goto retry;
955 }
956 v = MTX_READ_VALUE(m);
957 } while (v != MTX_UNOWNED);
958 spinlock_enter();
959 }
960 if (m == td->td_lock)
961 break;
962 _mtx_release_lock_quick(m);
963 }
964 LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
965 line);
966 WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
967
968 #if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
969 if (__predict_true(!doing_lockprof))
970 return;
971 #endif
972 #ifdef KDTRACE_HOOKS
973 spin_time += lockstat_nsecs(&m->lock_object);
974 #endif
975 LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire, m, contested,
976 waittime, file, line);
977 #ifdef KDTRACE_HOOKS
978 if (lda.spin_cnt != 0)
979 LOCKSTAT_RECORD1(thread__spin, m, spin_time);
980 #endif
981 }
982
983 struct mtx *
thread_lock_block(struct thread * td)984 thread_lock_block(struct thread *td)
985 {
986 struct mtx *lock;
987
988 lock = td->td_lock;
989 mtx_assert(lock, MA_OWNED);
990 td->td_lock = &blocked_lock;
991
992 return (lock);
993 }
994
995 void
thread_lock_unblock(struct thread * td,struct mtx * new)996 thread_lock_unblock(struct thread *td, struct mtx *new)
997 {
998
999 mtx_assert(new, MA_OWNED);
1000 KASSERT(td->td_lock == &blocked_lock,
1001 ("thread %p lock %p not blocked_lock %p",
1002 td, td->td_lock, &blocked_lock));
1003 atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
1004 }
1005
1006 void
thread_lock_block_wait(struct thread * td)1007 thread_lock_block_wait(struct thread *td)
1008 {
1009
1010 while (td->td_lock == &blocked_lock)
1011 cpu_spinwait();
1012
1013 /* Acquire fence to be certain that all thread state is visible. */
1014 atomic_thread_fence_acq();
1015 }
1016
1017 void
thread_lock_set(struct thread * td,struct mtx * new)1018 thread_lock_set(struct thread *td, struct mtx *new)
1019 {
1020 struct mtx *lock;
1021
1022 mtx_assert(new, MA_OWNED);
1023 lock = td->td_lock;
1024 mtx_assert(lock, MA_OWNED);
1025 td->td_lock = new;
1026 mtx_unlock_spin(lock);
1027 }
1028
1029 /*
1030 * __mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
1031 *
1032 * We are only called here if the lock is recursed, contested (i.e. we
1033 * need to wake up a blocked thread) or lockstat probe is active.
1034 */
1035 #if LOCK_DEBUG > 0
1036 void
__mtx_unlock_sleep(volatile uintptr_t * c,uintptr_t v,int opts,const char * file,int line)1037 __mtx_unlock_sleep(volatile uintptr_t *c, uintptr_t v, int opts,
1038 const char *file, int line)
1039 #else
1040 void
1041 __mtx_unlock_sleep(volatile uintptr_t *c, uintptr_t v)
1042 #endif
1043 {
1044 struct mtx *m;
1045 struct turnstile *ts;
1046 uintptr_t tid;
1047
1048 if (SCHEDULER_STOPPED())
1049 return;
1050
1051 tid = (uintptr_t)curthread;
1052 m = mtxlock2mtx(c);
1053
1054 if (__predict_false(v == tid))
1055 v = MTX_READ_VALUE(m);
1056
1057 if (__predict_false(v & MTX_RECURSED)) {
1058 if (--(m->mtx_recurse) == 0)
1059 atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
1060 if (LOCK_LOG_TEST(&m->lock_object, opts))
1061 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
1062 return;
1063 }
1064
1065 LOCKSTAT_PROFILE_RELEASE_LOCK(adaptive__release, m);
1066 if (v == tid && _mtx_release_lock(m, tid))
1067 return;
1068
1069 /*
1070 * We have to lock the chain before the turnstile so this turnstile
1071 * can be removed from the hash list if it is empty.
1072 */
1073 turnstile_chain_lock(&m->lock_object);
1074 _mtx_release_lock_quick(m);
1075 ts = turnstile_lookup(&m->lock_object);
1076 if (__predict_false(ts == NULL)) {
1077 panic("got NULL turnstile on mutex %p v %p", m, (void *)v);
1078 }
1079 if (LOCK_LOG_TEST(&m->lock_object, opts))
1080 CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
1081 turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
1082
1083 /*
1084 * This turnstile is now no longer associated with the mutex. We can
1085 * unlock the chain lock so a new turnstile may take it's place.
1086 */
1087 turnstile_unpend(ts);
1088 turnstile_chain_unlock(&m->lock_object);
1089 }
1090
1091 /*
1092 * All the unlocking of MTX_SPIN locks is done inline.
1093 * See the __mtx_unlock_spin() macro for the details.
1094 */
1095
1096 /*
1097 * The backing function for the INVARIANTS-enabled mtx_assert()
1098 */
1099 #ifdef INVARIANT_SUPPORT
1100 void
__mtx_assert(const volatile uintptr_t * c,int what,const char * file,int line)1101 __mtx_assert(const volatile uintptr_t *c, int what, const char *file, int line)
1102 {
1103 const struct mtx *m;
1104
1105 if (KERNEL_PANICKED() || dumping || SCHEDULER_STOPPED())
1106 return;
1107
1108 m = mtxlock2mtx(c);
1109
1110 switch (what) {
1111 case MA_OWNED:
1112 case MA_OWNED | MA_RECURSED:
1113 case MA_OWNED | MA_NOTRECURSED:
1114 if (!mtx_owned(m))
1115 panic("mutex %s not owned at %s:%d",
1116 m->lock_object.lo_name, file, line);
1117 if (mtx_recursed(m)) {
1118 if ((what & MA_NOTRECURSED) != 0)
1119 panic("mutex %s recursed at %s:%d",
1120 m->lock_object.lo_name, file, line);
1121 } else if ((what & MA_RECURSED) != 0) {
1122 panic("mutex %s unrecursed at %s:%d",
1123 m->lock_object.lo_name, file, line);
1124 }
1125 break;
1126 case MA_NOTOWNED:
1127 if (mtx_owned(m))
1128 panic("mutex %s owned at %s:%d",
1129 m->lock_object.lo_name, file, line);
1130 break;
1131 default:
1132 panic("unknown mtx_assert at %s:%d", file, line);
1133 }
1134 }
1135 #endif
1136
1137 /*
1138 * General init routine used by the MTX_SYSINIT() macro.
1139 */
1140 void
mtx_sysinit(void * arg)1141 mtx_sysinit(void *arg)
1142 {
1143 struct mtx_args *margs = arg;
1144
1145 mtx_init((struct mtx *)margs->ma_mtx, margs->ma_desc, NULL,
1146 margs->ma_opts);
1147 }
1148
1149 /*
1150 * Mutex initialization routine; initialize lock `m' of type contained in
1151 * `opts' with options contained in `opts' and name `name.' The optional
1152 * lock type `type' is used as a general lock category name for use with
1153 * witness.
1154 */
1155 void
_mtx_init(volatile uintptr_t * c,const char * name,const char * type,int opts)1156 _mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts)
1157 {
1158 struct mtx *m;
1159 struct lock_class *class;
1160 int flags;
1161
1162 m = mtxlock2mtx(c);
1163
1164 MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
1165 MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE | MTX_NEW)) == 0);
1166 ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock,
1167 ("%s: mtx_lock not aligned for %s: %p", __func__, name,
1168 &m->mtx_lock));
1169
1170 /* Determine lock class and lock flags. */
1171 if (opts & MTX_SPIN)
1172 class = &lock_class_mtx_spin;
1173 else
1174 class = &lock_class_mtx_sleep;
1175 flags = 0;
1176 if (opts & MTX_QUIET)
1177 flags |= LO_QUIET;
1178 if (opts & MTX_RECURSE)
1179 flags |= LO_RECURSABLE;
1180 if ((opts & MTX_NOWITNESS) == 0)
1181 flags |= LO_WITNESS;
1182 if (opts & MTX_DUPOK)
1183 flags |= LO_DUPOK;
1184 if (opts & MTX_NOPROFILE)
1185 flags |= LO_NOPROFILE;
1186 if (opts & MTX_NEW)
1187 flags |= LO_NEW;
1188
1189 /* Initialize mutex. */
1190 lock_init(&m->lock_object, class, name, type, flags);
1191
1192 m->mtx_lock = MTX_UNOWNED;
1193 m->mtx_recurse = 0;
1194 }
1195
1196 /*
1197 * Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be
1198 * passed in as a flag here because if the corresponding mtx_init() was
1199 * called with MTX_QUIET set, then it will already be set in the mutex's
1200 * flags.
1201 */
1202 void
_mtx_destroy(volatile uintptr_t * c)1203 _mtx_destroy(volatile uintptr_t *c)
1204 {
1205 struct mtx *m;
1206
1207 m = mtxlock2mtx(c);
1208
1209 if (!mtx_owned(m))
1210 MPASS(mtx_unowned(m));
1211 else {
1212 MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
1213
1214 /* Perform the non-mtx related part of mtx_unlock_spin(). */
1215 if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin) {
1216 lock_profile_release_lock(&m->lock_object, true);
1217 spinlock_exit();
1218 } else {
1219 TD_LOCKS_DEC(curthread);
1220 lock_profile_release_lock(&m->lock_object, false);
1221 }
1222
1223 /* Tell witness this isn't locked to make it happy. */
1224 WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
1225 __LINE__);
1226 }
1227
1228 m->mtx_lock = MTX_DESTROYED;
1229 lock_destroy(&m->lock_object);
1230 }
1231
1232 /*
1233 * Intialize the mutex code and system mutexes. This is called from the MD
1234 * startup code prior to mi_startup(). The per-CPU data space needs to be
1235 * setup before this is called.
1236 */
1237 void
mutex_init(void)1238 mutex_init(void)
1239 {
1240
1241 /* Setup turnstiles so that sleep mutexes work. */
1242 init_turnstiles();
1243
1244 /*
1245 * Initialize mutexes.
1246 */
1247 mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
1248 mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
1249 blocked_lock.mtx_lock = 0xdeadc0de; /* Always blocked. */
1250 mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
1251 mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN);
1252 mtx_init(&proc0.p_statmtx, "pstatl", NULL, MTX_SPIN);
1253 mtx_init(&proc0.p_itimmtx, "pitiml", NULL, MTX_SPIN);
1254 mtx_init(&proc0.p_profmtx, "pprofl", NULL, MTX_SPIN);
1255 mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
1256 mtx_lock(&Giant);
1257 }
1258
1259 static void __noinline
_mtx_lock_indefinite_check(struct mtx * m,struct lock_delay_arg * ldap)1260 _mtx_lock_indefinite_check(struct mtx *m, struct lock_delay_arg *ldap)
1261 {
1262 struct thread *td;
1263
1264 ldap->spin_cnt++;
1265 if (ldap->spin_cnt < 60000000 || kdb_active || KERNEL_PANICKED())
1266 cpu_lock_delay();
1267 else {
1268 td = mtx_owner(m);
1269
1270 /* If the mutex is unlocked, try again. */
1271 if (td == NULL)
1272 return;
1273
1274 printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
1275 m, m->lock_object.lo_name, td, td->td_tid);
1276 #ifdef WITNESS
1277 witness_display_spinlock(&m->lock_object, td, printf);
1278 #endif
1279 panic("spin lock held too long");
1280 }
1281 cpu_spinwait();
1282 }
1283
1284 void
mtx_spin_wait_unlocked(struct mtx * m)1285 mtx_spin_wait_unlocked(struct mtx *m)
1286 {
1287 struct lock_delay_arg lda;
1288
1289 KASSERT(m->mtx_lock != MTX_DESTROYED,
1290 ("%s() of destroyed mutex %p", __func__, m));
1291 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_sleep,
1292 ("%s() of sleep mutex %p (%s)", __func__, m,
1293 m->lock_object.lo_name));
1294 KASSERT(!mtx_owned(m), ("%s() waiting on myself on lock %p (%s)", __func__, m,
1295 m->lock_object.lo_name));
1296
1297 lda.spin_cnt = 0;
1298
1299 while (atomic_load_acq_ptr(&m->mtx_lock) != MTX_UNOWNED) {
1300 if (__predict_true(lda.spin_cnt < 10000000)) {
1301 cpu_spinwait();
1302 lda.spin_cnt++;
1303 } else {
1304 _mtx_lock_indefinite_check(m, &lda);
1305 }
1306 }
1307 }
1308
1309 void
mtx_wait_unlocked(struct mtx * m)1310 mtx_wait_unlocked(struct mtx *m)
1311 {
1312 struct thread *owner;
1313 uintptr_t v;
1314
1315 KASSERT(m->mtx_lock != MTX_DESTROYED,
1316 ("%s() of destroyed mutex %p", __func__, m));
1317 KASSERT(LOCK_CLASS(&m->lock_object) != &lock_class_mtx_spin,
1318 ("%s() of spin mutex %p (%s)", __func__, m,
1319 m->lock_object.lo_name));
1320 KASSERT(!mtx_owned(m), ("%s() waiting on myself on lock %p (%s)", __func__, m,
1321 m->lock_object.lo_name));
1322
1323 for (;;) {
1324 v = atomic_load_acq_ptr(&m->mtx_lock);
1325 if (v == MTX_UNOWNED) {
1326 break;
1327 }
1328 owner = lv_mtx_owner(v);
1329 if (!TD_IS_RUNNING(owner)) {
1330 mtx_lock(m);
1331 mtx_unlock(m);
1332 break;
1333 }
1334 cpu_spinwait();
1335 }
1336 }
1337
1338 #ifdef DDB
1339 static void
db_show_mtx(const struct lock_object * lock)1340 db_show_mtx(const struct lock_object *lock)
1341 {
1342 struct thread *td;
1343 const struct mtx *m;
1344
1345 m = (const struct mtx *)lock;
1346
1347 db_printf(" flags: {");
1348 if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
1349 db_printf("SPIN");
1350 else
1351 db_printf("DEF");
1352 if (m->lock_object.lo_flags & LO_RECURSABLE)
1353 db_printf(", RECURSE");
1354 if (m->lock_object.lo_flags & LO_DUPOK)
1355 db_printf(", DUPOK");
1356 db_printf("}\n");
1357 db_printf(" state: {");
1358 if (mtx_unowned(m))
1359 db_printf("UNOWNED");
1360 else if (mtx_destroyed(m))
1361 db_printf("DESTROYED");
1362 else {
1363 db_printf("OWNED");
1364 if (m->mtx_lock & MTX_CONTESTED)
1365 db_printf(", CONTESTED");
1366 if (m->mtx_lock & MTX_RECURSED)
1367 db_printf(", RECURSED");
1368 }
1369 db_printf("}\n");
1370 if (!mtx_unowned(m) && !mtx_destroyed(m)) {
1371 td = mtx_owner(m);
1372 db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
1373 td->td_tid, td->td_proc->p_pid, td->td_name);
1374 if (mtx_recursed(m))
1375 db_printf(" recursed: %d\n", m->mtx_recurse);
1376 }
1377 }
1378 #endif
1379