xref: /linux/kernel/rcu/rcutorture.c (revision e0bf6c5ca2d3281f231c5f0c9bf145e9513644de)
1 /*
2  * Read-Copy Update module-based torture test facility
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, you can access it online at
16  * http://www.gnu.org/licenses/gpl-2.0.html.
17  *
18  * Copyright (C) IBM Corporation, 2005, 2006
19  *
20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
21  *	  Josh Triplett <josh@joshtriplett.org>
22  *
23  * See also:  Documentation/RCU/torture.txt
24  */
25 #include <linux/types.h>
26 #include <linux/kernel.h>
27 #include <linux/init.h>
28 #include <linux/module.h>
29 #include <linux/kthread.h>
30 #include <linux/err.h>
31 #include <linux/spinlock.h>
32 #include <linux/smp.h>
33 #include <linux/rcupdate.h>
34 #include <linux/interrupt.h>
35 #include <linux/sched.h>
36 #include <linux/atomic.h>
37 #include <linux/bitops.h>
38 #include <linux/completion.h>
39 #include <linux/moduleparam.h>
40 #include <linux/percpu.h>
41 #include <linux/notifier.h>
42 #include <linux/reboot.h>
43 #include <linux/freezer.h>
44 #include <linux/cpu.h>
45 #include <linux/delay.h>
46 #include <linux/stat.h>
47 #include <linux/srcu.h>
48 #include <linux/slab.h>
49 #include <linux/trace_clock.h>
50 #include <asm/byteorder.h>
51 #include <linux/torture.h>
52 #include <linux/vmalloc.h>
53 
54 MODULE_LICENSE("GPL");
55 MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
56 
57 
58 torture_param(int, cbflood_inter_holdoff, HZ,
59 	      "Holdoff between floods (jiffies)");
60 torture_param(int, cbflood_intra_holdoff, 1,
61 	      "Holdoff between bursts (jiffies)");
62 torture_param(int, cbflood_n_burst, 3, "# bursts in flood, zero to disable");
63 torture_param(int, cbflood_n_per_burst, 20000,
64 	      "# callbacks per burst in flood");
65 torture_param(int, fqs_duration, 0,
66 	      "Duration of fqs bursts (us), 0 to disable");
67 torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
68 torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
69 torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
70 torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
71 torture_param(bool, gp_normal, false,
72 	     "Use normal (non-expedited) GP wait primitives");
73 torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
74 torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
75 torture_param(int, n_barrier_cbs, 0,
76 	     "# of callbacks/kthreads for barrier testing");
77 torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
78 torture_param(int, nreaders, -1, "Number of RCU reader threads");
79 torture_param(int, object_debug, 0,
80 	     "Enable debug-object double call_rcu() testing");
81 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
82 torture_param(int, onoff_interval, 0,
83 	     "Time between CPU hotplugs (s), 0=disable");
84 torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
85 torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
86 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
87 torture_param(int, stall_cpu_holdoff, 10,
88 	     "Time to wait before starting stall (s).");
89 torture_param(int, stat_interval, 60,
90 	     "Number of seconds between stats printk()s");
91 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
92 torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
93 torture_param(int, test_boost_duration, 4,
94 	     "Duration of each boost test, seconds.");
95 torture_param(int, test_boost_interval, 7,
96 	     "Interval between boost tests, seconds.");
97 torture_param(bool, test_no_idle_hz, true,
98 	     "Test support for tickless idle CPUs");
99 torture_param(bool, verbose, true,
100 	     "Enable verbose debugging printk()s");
101 
102 static char *torture_type = "rcu";
103 module_param(torture_type, charp, 0444);
104 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, ...)");
105 
106 static int nrealreaders;
107 static int ncbflooders;
108 static struct task_struct *writer_task;
109 static struct task_struct **fakewriter_tasks;
110 static struct task_struct **reader_tasks;
111 static struct task_struct *stats_task;
112 static struct task_struct **cbflood_task;
113 static struct task_struct *fqs_task;
114 static struct task_struct *boost_tasks[NR_CPUS];
115 static struct task_struct *stall_task;
116 static struct task_struct **barrier_cbs_tasks;
117 static struct task_struct *barrier_task;
118 
119 #define RCU_TORTURE_PIPE_LEN 10
120 
121 struct rcu_torture {
122 	struct rcu_head rtort_rcu;
123 	int rtort_pipe_count;
124 	struct list_head rtort_free;
125 	int rtort_mbtest;
126 };
127 
128 static LIST_HEAD(rcu_torture_freelist);
129 static struct rcu_torture __rcu *rcu_torture_current;
130 static unsigned long rcu_torture_current_version;
131 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
132 static DEFINE_SPINLOCK(rcu_torture_lock);
133 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1],
134 		      rcu_torture_count) = { 0 };
135 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1],
136 		      rcu_torture_batch) = { 0 };
137 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
138 static atomic_t n_rcu_torture_alloc;
139 static atomic_t n_rcu_torture_alloc_fail;
140 static atomic_t n_rcu_torture_free;
141 static atomic_t n_rcu_torture_mberror;
142 static atomic_t n_rcu_torture_error;
143 static long n_rcu_torture_barrier_error;
144 static long n_rcu_torture_boost_ktrerror;
145 static long n_rcu_torture_boost_rterror;
146 static long n_rcu_torture_boost_failure;
147 static long n_rcu_torture_boosts;
148 static long n_rcu_torture_timers;
149 static long n_barrier_attempts;
150 static long n_barrier_successes;
151 static atomic_long_t n_cbfloods;
152 static struct list_head rcu_torture_removed;
153 
154 static int rcu_torture_writer_state;
155 #define RTWS_FIXED_DELAY	0
156 #define RTWS_DELAY		1
157 #define RTWS_REPLACE		2
158 #define RTWS_DEF_FREE		3
159 #define RTWS_EXP_SYNC		4
160 #define RTWS_COND_GET		5
161 #define RTWS_COND_SYNC		6
162 #define RTWS_SYNC		7
163 #define RTWS_STUTTER		8
164 #define RTWS_STOPPING		9
165 
166 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
167 #define RCUTORTURE_RUNNABLE_INIT 1
168 #else
169 #define RCUTORTURE_RUNNABLE_INIT 0
170 #endif
171 static int torture_runnable = RCUTORTURE_RUNNABLE_INIT;
172 module_param(torture_runnable, int, 0444);
173 MODULE_PARM_DESC(torture_runnable, "Start rcutorture at boot");
174 
175 #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU)
176 #define rcu_can_boost() 1
177 #else /* #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
178 #define rcu_can_boost() 0
179 #endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
180 
181 #ifdef CONFIG_RCU_TRACE
182 static u64 notrace rcu_trace_clock_local(void)
183 {
184 	u64 ts = trace_clock_local();
185 	unsigned long __maybe_unused ts_rem = do_div(ts, NSEC_PER_USEC);
186 	return ts;
187 }
188 #else /* #ifdef CONFIG_RCU_TRACE */
189 static u64 notrace rcu_trace_clock_local(void)
190 {
191 	return 0ULL;
192 }
193 #endif /* #else #ifdef CONFIG_RCU_TRACE */
194 
195 static unsigned long boost_starttime;	/* jiffies of next boost test start. */
196 static DEFINE_MUTEX(boost_mutex);	/* protect setting boost_starttime */
197 					/*  and boost task create/destroy. */
198 static atomic_t barrier_cbs_count;	/* Barrier callbacks registered. */
199 static bool barrier_phase;		/* Test phase. */
200 static atomic_t barrier_cbs_invoked;	/* Barrier callbacks invoked. */
201 static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
202 static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
203 
204 /*
205  * Allocate an element from the rcu_tortures pool.
206  */
207 static struct rcu_torture *
208 rcu_torture_alloc(void)
209 {
210 	struct list_head *p;
211 
212 	spin_lock_bh(&rcu_torture_lock);
213 	if (list_empty(&rcu_torture_freelist)) {
214 		atomic_inc(&n_rcu_torture_alloc_fail);
215 		spin_unlock_bh(&rcu_torture_lock);
216 		return NULL;
217 	}
218 	atomic_inc(&n_rcu_torture_alloc);
219 	p = rcu_torture_freelist.next;
220 	list_del_init(p);
221 	spin_unlock_bh(&rcu_torture_lock);
222 	return container_of(p, struct rcu_torture, rtort_free);
223 }
224 
225 /*
226  * Free an element to the rcu_tortures pool.
227  */
228 static void
229 rcu_torture_free(struct rcu_torture *p)
230 {
231 	atomic_inc(&n_rcu_torture_free);
232 	spin_lock_bh(&rcu_torture_lock);
233 	list_add_tail(&p->rtort_free, &rcu_torture_freelist);
234 	spin_unlock_bh(&rcu_torture_lock);
235 }
236 
237 /*
238  * Operations vector for selecting different types of tests.
239  */
240 
241 struct rcu_torture_ops {
242 	int ttype;
243 	void (*init)(void);
244 	int (*readlock)(void);
245 	void (*read_delay)(struct torture_random_state *rrsp);
246 	void (*readunlock)(int idx);
247 	unsigned long (*started)(void);
248 	unsigned long (*completed)(void);
249 	void (*deferred_free)(struct rcu_torture *p);
250 	void (*sync)(void);
251 	void (*exp_sync)(void);
252 	unsigned long (*get_state)(void);
253 	void (*cond_sync)(unsigned long oldstate);
254 	void (*call)(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
255 	void (*cb_barrier)(void);
256 	void (*fqs)(void);
257 	void (*stats)(void);
258 	int irq_capable;
259 	int can_boost;
260 	const char *name;
261 };
262 
263 static struct rcu_torture_ops *cur_ops;
264 
265 /*
266  * Definitions for rcu torture testing.
267  */
268 
269 static int rcu_torture_read_lock(void) __acquires(RCU)
270 {
271 	rcu_read_lock();
272 	return 0;
273 }
274 
275 static void rcu_read_delay(struct torture_random_state *rrsp)
276 {
277 	const unsigned long shortdelay_us = 200;
278 	const unsigned long longdelay_ms = 50;
279 
280 	/* We want a short delay sometimes to make a reader delay the grace
281 	 * period, and we want a long delay occasionally to trigger
282 	 * force_quiescent_state. */
283 
284 	if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms)))
285 		mdelay(longdelay_ms);
286 	if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
287 		udelay(shortdelay_us);
288 #ifdef CONFIG_PREEMPT
289 	if (!preempt_count() &&
290 	    !(torture_random(rrsp) % (nrealreaders * 20000)))
291 		preempt_schedule();  /* No QS if preempt_disable() in effect */
292 #endif
293 }
294 
295 static void rcu_torture_read_unlock(int idx) __releases(RCU)
296 {
297 	rcu_read_unlock();
298 }
299 
300 /*
301  * Update callback in the pipe.  This should be invoked after a grace period.
302  */
303 static bool
304 rcu_torture_pipe_update_one(struct rcu_torture *rp)
305 {
306 	int i;
307 
308 	i = rp->rtort_pipe_count;
309 	if (i > RCU_TORTURE_PIPE_LEN)
310 		i = RCU_TORTURE_PIPE_LEN;
311 	atomic_inc(&rcu_torture_wcount[i]);
312 	if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
313 		rp->rtort_mbtest = 0;
314 		return true;
315 	}
316 	return false;
317 }
318 
319 /*
320  * Update all callbacks in the pipe.  Suitable for synchronous grace-period
321  * primitives.
322  */
323 static void
324 rcu_torture_pipe_update(struct rcu_torture *old_rp)
325 {
326 	struct rcu_torture *rp;
327 	struct rcu_torture *rp1;
328 
329 	if (old_rp)
330 		list_add(&old_rp->rtort_free, &rcu_torture_removed);
331 	list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
332 		if (rcu_torture_pipe_update_one(rp)) {
333 			list_del(&rp->rtort_free);
334 			rcu_torture_free(rp);
335 		}
336 	}
337 }
338 
339 static void
340 rcu_torture_cb(struct rcu_head *p)
341 {
342 	struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
343 
344 	if (torture_must_stop_irq()) {
345 		/* Test is ending, just drop callbacks on the floor. */
346 		/* The next initialization will pick up the pieces. */
347 		return;
348 	}
349 	if (rcu_torture_pipe_update_one(rp))
350 		rcu_torture_free(rp);
351 	else
352 		cur_ops->deferred_free(rp);
353 }
354 
355 static unsigned long rcu_no_completed(void)
356 {
357 	return 0;
358 }
359 
360 static void rcu_torture_deferred_free(struct rcu_torture *p)
361 {
362 	call_rcu(&p->rtort_rcu, rcu_torture_cb);
363 }
364 
365 static void rcu_sync_torture_init(void)
366 {
367 	INIT_LIST_HEAD(&rcu_torture_removed);
368 }
369 
370 static struct rcu_torture_ops rcu_ops = {
371 	.ttype		= RCU_FLAVOR,
372 	.init		= rcu_sync_torture_init,
373 	.readlock	= rcu_torture_read_lock,
374 	.read_delay	= rcu_read_delay,
375 	.readunlock	= rcu_torture_read_unlock,
376 	.started	= rcu_batches_started,
377 	.completed	= rcu_batches_completed,
378 	.deferred_free	= rcu_torture_deferred_free,
379 	.sync		= synchronize_rcu,
380 	.exp_sync	= synchronize_rcu_expedited,
381 	.get_state	= get_state_synchronize_rcu,
382 	.cond_sync	= cond_synchronize_rcu,
383 	.call		= call_rcu,
384 	.cb_barrier	= rcu_barrier,
385 	.fqs		= rcu_force_quiescent_state,
386 	.stats		= NULL,
387 	.irq_capable	= 1,
388 	.can_boost	= rcu_can_boost(),
389 	.name		= "rcu"
390 };
391 
392 /*
393  * Definitions for rcu_bh torture testing.
394  */
395 
396 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
397 {
398 	rcu_read_lock_bh();
399 	return 0;
400 }
401 
402 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
403 {
404 	rcu_read_unlock_bh();
405 }
406 
407 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
408 {
409 	call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
410 }
411 
412 static struct rcu_torture_ops rcu_bh_ops = {
413 	.ttype		= RCU_BH_FLAVOR,
414 	.init		= rcu_sync_torture_init,
415 	.readlock	= rcu_bh_torture_read_lock,
416 	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
417 	.readunlock	= rcu_bh_torture_read_unlock,
418 	.started	= rcu_batches_started_bh,
419 	.completed	= rcu_batches_completed_bh,
420 	.deferred_free	= rcu_bh_torture_deferred_free,
421 	.sync		= synchronize_rcu_bh,
422 	.exp_sync	= synchronize_rcu_bh_expedited,
423 	.call		= call_rcu_bh,
424 	.cb_barrier	= rcu_barrier_bh,
425 	.fqs		= rcu_bh_force_quiescent_state,
426 	.stats		= NULL,
427 	.irq_capable	= 1,
428 	.name		= "rcu_bh"
429 };
430 
431 /*
432  * Don't even think about trying any of these in real life!!!
433  * The names includes "busted", and they really means it!
434  * The only purpose of these functions is to provide a buggy RCU
435  * implementation to make sure that rcutorture correctly emits
436  * buggy-RCU error messages.
437  */
438 static void rcu_busted_torture_deferred_free(struct rcu_torture *p)
439 {
440 	/* This is a deliberate bug for testing purposes only! */
441 	rcu_torture_cb(&p->rtort_rcu);
442 }
443 
444 static void synchronize_rcu_busted(void)
445 {
446 	/* This is a deliberate bug for testing purposes only! */
447 }
448 
449 static void
450 call_rcu_busted(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
451 {
452 	/* This is a deliberate bug for testing purposes only! */
453 	func(head);
454 }
455 
456 static struct rcu_torture_ops rcu_busted_ops = {
457 	.ttype		= INVALID_RCU_FLAVOR,
458 	.init		= rcu_sync_torture_init,
459 	.readlock	= rcu_torture_read_lock,
460 	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
461 	.readunlock	= rcu_torture_read_unlock,
462 	.started	= rcu_no_completed,
463 	.completed	= rcu_no_completed,
464 	.deferred_free	= rcu_busted_torture_deferred_free,
465 	.sync		= synchronize_rcu_busted,
466 	.exp_sync	= synchronize_rcu_busted,
467 	.call		= call_rcu_busted,
468 	.cb_barrier	= NULL,
469 	.fqs		= NULL,
470 	.stats		= NULL,
471 	.irq_capable	= 1,
472 	.name		= "rcu_busted"
473 };
474 
475 /*
476  * Definitions for srcu torture testing.
477  */
478 
479 DEFINE_STATIC_SRCU(srcu_ctl);
480 
481 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
482 {
483 	return srcu_read_lock(&srcu_ctl);
484 }
485 
486 static void srcu_read_delay(struct torture_random_state *rrsp)
487 {
488 	long delay;
489 	const long uspertick = 1000000 / HZ;
490 	const long longdelay = 10;
491 
492 	/* We want there to be long-running readers, but not all the time. */
493 
494 	delay = torture_random(rrsp) %
495 		(nrealreaders * 2 * longdelay * uspertick);
496 	if (!delay)
497 		schedule_timeout_interruptible(longdelay);
498 	else
499 		rcu_read_delay(rrsp);
500 }
501 
502 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
503 {
504 	srcu_read_unlock(&srcu_ctl, idx);
505 }
506 
507 static unsigned long srcu_torture_completed(void)
508 {
509 	return srcu_batches_completed(&srcu_ctl);
510 }
511 
512 static void srcu_torture_deferred_free(struct rcu_torture *rp)
513 {
514 	call_srcu(&srcu_ctl, &rp->rtort_rcu, rcu_torture_cb);
515 }
516 
517 static void srcu_torture_synchronize(void)
518 {
519 	synchronize_srcu(&srcu_ctl);
520 }
521 
522 static void srcu_torture_call(struct rcu_head *head,
523 			      void (*func)(struct rcu_head *head))
524 {
525 	call_srcu(&srcu_ctl, head, func);
526 }
527 
528 static void srcu_torture_barrier(void)
529 {
530 	srcu_barrier(&srcu_ctl);
531 }
532 
533 static void srcu_torture_stats(void)
534 {
535 	int cpu;
536 	int idx = srcu_ctl.completed & 0x1;
537 
538 	pr_alert("%s%s per-CPU(idx=%d):",
539 		 torture_type, TORTURE_FLAG, idx);
540 	for_each_possible_cpu(cpu) {
541 		long c0, c1;
542 
543 		c0 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx];
544 		c1 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx];
545 		pr_cont(" %d(%ld,%ld)", cpu, c0, c1);
546 	}
547 	pr_cont("\n");
548 }
549 
550 static void srcu_torture_synchronize_expedited(void)
551 {
552 	synchronize_srcu_expedited(&srcu_ctl);
553 }
554 
555 static struct rcu_torture_ops srcu_ops = {
556 	.ttype		= SRCU_FLAVOR,
557 	.init		= rcu_sync_torture_init,
558 	.readlock	= srcu_torture_read_lock,
559 	.read_delay	= srcu_read_delay,
560 	.readunlock	= srcu_torture_read_unlock,
561 	.started	= NULL,
562 	.completed	= srcu_torture_completed,
563 	.deferred_free	= srcu_torture_deferred_free,
564 	.sync		= srcu_torture_synchronize,
565 	.exp_sync	= srcu_torture_synchronize_expedited,
566 	.call		= srcu_torture_call,
567 	.cb_barrier	= srcu_torture_barrier,
568 	.stats		= srcu_torture_stats,
569 	.name		= "srcu"
570 };
571 
572 /*
573  * Definitions for sched torture testing.
574  */
575 
576 static int sched_torture_read_lock(void)
577 {
578 	preempt_disable();
579 	return 0;
580 }
581 
582 static void sched_torture_read_unlock(int idx)
583 {
584 	preempt_enable();
585 }
586 
587 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
588 {
589 	call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
590 }
591 
592 static struct rcu_torture_ops sched_ops = {
593 	.ttype		= RCU_SCHED_FLAVOR,
594 	.init		= rcu_sync_torture_init,
595 	.readlock	= sched_torture_read_lock,
596 	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
597 	.readunlock	= sched_torture_read_unlock,
598 	.started	= rcu_batches_started_sched,
599 	.completed	= rcu_batches_completed_sched,
600 	.deferred_free	= rcu_sched_torture_deferred_free,
601 	.sync		= synchronize_sched,
602 	.exp_sync	= synchronize_sched_expedited,
603 	.call		= call_rcu_sched,
604 	.cb_barrier	= rcu_barrier_sched,
605 	.fqs		= rcu_sched_force_quiescent_state,
606 	.stats		= NULL,
607 	.irq_capable	= 1,
608 	.name		= "sched"
609 };
610 
611 #ifdef CONFIG_TASKS_RCU
612 
613 /*
614  * Definitions for RCU-tasks torture testing.
615  */
616 
617 static int tasks_torture_read_lock(void)
618 {
619 	return 0;
620 }
621 
622 static void tasks_torture_read_unlock(int idx)
623 {
624 }
625 
626 static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
627 {
628 	call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
629 }
630 
631 static struct rcu_torture_ops tasks_ops = {
632 	.ttype		= RCU_TASKS_FLAVOR,
633 	.init		= rcu_sync_torture_init,
634 	.readlock	= tasks_torture_read_lock,
635 	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
636 	.readunlock	= tasks_torture_read_unlock,
637 	.started	= rcu_no_completed,
638 	.completed	= rcu_no_completed,
639 	.deferred_free	= rcu_tasks_torture_deferred_free,
640 	.sync		= synchronize_rcu_tasks,
641 	.exp_sync	= synchronize_rcu_tasks,
642 	.call		= call_rcu_tasks,
643 	.cb_barrier	= rcu_barrier_tasks,
644 	.fqs		= NULL,
645 	.stats		= NULL,
646 	.irq_capable	= 1,
647 	.name		= "tasks"
648 };
649 
650 #define RCUTORTURE_TASKS_OPS &tasks_ops,
651 
652 #else /* #ifdef CONFIG_TASKS_RCU */
653 
654 #define RCUTORTURE_TASKS_OPS
655 
656 #endif /* #else #ifdef CONFIG_TASKS_RCU */
657 
658 /*
659  * RCU torture priority-boost testing.  Runs one real-time thread per
660  * CPU for moderate bursts, repeatedly registering RCU callbacks and
661  * spinning waiting for them to be invoked.  If a given callback takes
662  * too long to be invoked, we assume that priority inversion has occurred.
663  */
664 
665 struct rcu_boost_inflight {
666 	struct rcu_head rcu;
667 	int inflight;
668 };
669 
670 static void rcu_torture_boost_cb(struct rcu_head *head)
671 {
672 	struct rcu_boost_inflight *rbip =
673 		container_of(head, struct rcu_boost_inflight, rcu);
674 
675 	smp_mb(); /* Ensure RCU-core accesses precede clearing ->inflight */
676 	rbip->inflight = 0;
677 }
678 
679 static int rcu_torture_boost(void *arg)
680 {
681 	unsigned long call_rcu_time;
682 	unsigned long endtime;
683 	unsigned long oldstarttime;
684 	struct rcu_boost_inflight rbi = { .inflight = 0 };
685 	struct sched_param sp;
686 
687 	VERBOSE_TOROUT_STRING("rcu_torture_boost started");
688 
689 	/* Set real-time priority. */
690 	sp.sched_priority = 1;
691 	if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) {
692 		VERBOSE_TOROUT_STRING("rcu_torture_boost RT prio failed!");
693 		n_rcu_torture_boost_rterror++;
694 	}
695 
696 	init_rcu_head_on_stack(&rbi.rcu);
697 	/* Each pass through the following loop does one boost-test cycle. */
698 	do {
699 		/* Wait for the next test interval. */
700 		oldstarttime = boost_starttime;
701 		while (ULONG_CMP_LT(jiffies, oldstarttime)) {
702 			schedule_timeout_interruptible(oldstarttime - jiffies);
703 			stutter_wait("rcu_torture_boost");
704 			if (torture_must_stop())
705 				goto checkwait;
706 		}
707 
708 		/* Do one boost-test interval. */
709 		endtime = oldstarttime + test_boost_duration * HZ;
710 		call_rcu_time = jiffies;
711 		while (ULONG_CMP_LT(jiffies, endtime)) {
712 			/* If we don't have a callback in flight, post one. */
713 			if (!rbi.inflight) {
714 				smp_mb(); /* RCU core before ->inflight = 1. */
715 				rbi.inflight = 1;
716 				call_rcu(&rbi.rcu, rcu_torture_boost_cb);
717 				if (jiffies - call_rcu_time >
718 					 test_boost_duration * HZ - HZ / 2) {
719 					VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");
720 					n_rcu_torture_boost_failure++;
721 				}
722 				call_rcu_time = jiffies;
723 			}
724 			cond_resched_rcu_qs();
725 			stutter_wait("rcu_torture_boost");
726 			if (torture_must_stop())
727 				goto checkwait;
728 		}
729 
730 		/*
731 		 * Set the start time of the next test interval.
732 		 * Yes, this is vulnerable to long delays, but such
733 		 * delays simply cause a false negative for the next
734 		 * interval.  Besides, we are running at RT priority,
735 		 * so delays should be relatively rare.
736 		 */
737 		while (oldstarttime == boost_starttime &&
738 		       !kthread_should_stop()) {
739 			if (mutex_trylock(&boost_mutex)) {
740 				boost_starttime = jiffies +
741 						  test_boost_interval * HZ;
742 				n_rcu_torture_boosts++;
743 				mutex_unlock(&boost_mutex);
744 				break;
745 			}
746 			schedule_timeout_uninterruptible(1);
747 		}
748 
749 		/* Go do the stutter. */
750 checkwait:	stutter_wait("rcu_torture_boost");
751 	} while (!torture_must_stop());
752 
753 	/* Clean up and exit. */
754 	while (!kthread_should_stop() || rbi.inflight) {
755 		torture_shutdown_absorb("rcu_torture_boost");
756 		schedule_timeout_uninterruptible(1);
757 	}
758 	smp_mb(); /* order accesses to ->inflight before stack-frame death. */
759 	destroy_rcu_head_on_stack(&rbi.rcu);
760 	torture_kthread_stopping("rcu_torture_boost");
761 	return 0;
762 }
763 
764 static void rcu_torture_cbflood_cb(struct rcu_head *rhp)
765 {
766 }
767 
768 /*
769  * RCU torture callback-flood kthread.  Repeatedly induces bursts of calls
770  * to call_rcu() or analogous, increasing the probability of occurrence
771  * of callback-overflow corner cases.
772  */
773 static int
774 rcu_torture_cbflood(void *arg)
775 {
776 	int err = 1;
777 	int i;
778 	int j;
779 	struct rcu_head *rhp;
780 
781 	if (cbflood_n_per_burst > 0 &&
782 	    cbflood_inter_holdoff > 0 &&
783 	    cbflood_intra_holdoff > 0 &&
784 	    cur_ops->call &&
785 	    cur_ops->cb_barrier) {
786 		rhp = vmalloc(sizeof(*rhp) *
787 			      cbflood_n_burst * cbflood_n_per_burst);
788 		err = !rhp;
789 	}
790 	if (err) {
791 		VERBOSE_TOROUT_STRING("rcu_torture_cbflood disabled: Bad args or OOM");
792 		while (!torture_must_stop())
793 			schedule_timeout_interruptible(HZ);
794 		return 0;
795 	}
796 	VERBOSE_TOROUT_STRING("rcu_torture_cbflood task started");
797 	do {
798 		schedule_timeout_interruptible(cbflood_inter_holdoff);
799 		atomic_long_inc(&n_cbfloods);
800 		WARN_ON(signal_pending(current));
801 		for (i = 0; i < cbflood_n_burst; i++) {
802 			for (j = 0; j < cbflood_n_per_burst; j++) {
803 				cur_ops->call(&rhp[i * cbflood_n_per_burst + j],
804 					      rcu_torture_cbflood_cb);
805 			}
806 			schedule_timeout_interruptible(cbflood_intra_holdoff);
807 			WARN_ON(signal_pending(current));
808 		}
809 		cur_ops->cb_barrier();
810 		stutter_wait("rcu_torture_cbflood");
811 	} while (!torture_must_stop());
812 	vfree(rhp);
813 	torture_kthread_stopping("rcu_torture_cbflood");
814 	return 0;
815 }
816 
817 /*
818  * RCU torture force-quiescent-state kthread.  Repeatedly induces
819  * bursts of calls to force_quiescent_state(), increasing the probability
820  * of occurrence of some important types of race conditions.
821  */
822 static int
823 rcu_torture_fqs(void *arg)
824 {
825 	unsigned long fqs_resume_time;
826 	int fqs_burst_remaining;
827 
828 	VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
829 	do {
830 		fqs_resume_time = jiffies + fqs_stutter * HZ;
831 		while (ULONG_CMP_LT(jiffies, fqs_resume_time) &&
832 		       !kthread_should_stop()) {
833 			schedule_timeout_interruptible(1);
834 		}
835 		fqs_burst_remaining = fqs_duration;
836 		while (fqs_burst_remaining > 0 &&
837 		       !kthread_should_stop()) {
838 			cur_ops->fqs();
839 			udelay(fqs_holdoff);
840 			fqs_burst_remaining -= fqs_holdoff;
841 		}
842 		stutter_wait("rcu_torture_fqs");
843 	} while (!torture_must_stop());
844 	torture_kthread_stopping("rcu_torture_fqs");
845 	return 0;
846 }
847 
848 /*
849  * RCU torture writer kthread.  Repeatedly substitutes a new structure
850  * for that pointed to by rcu_torture_current, freeing the old structure
851  * after a series of grace periods (the "pipeline").
852  */
853 static int
854 rcu_torture_writer(void *arg)
855 {
856 	unsigned long gp_snap;
857 	bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
858 	bool gp_sync1 = gp_sync;
859 	int i;
860 	struct rcu_torture *rp;
861 	struct rcu_torture *old_rp;
862 	static DEFINE_TORTURE_RANDOM(rand);
863 	int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC,
864 			   RTWS_COND_GET, RTWS_SYNC };
865 	int nsynctypes = 0;
866 
867 	VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
868 
869 	/* Initialize synctype[] array.  If none set, take default. */
870 	if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync)
871 		gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true;
872 	if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync)
873 		synctype[nsynctypes++] = RTWS_COND_GET;
874 	else if (gp_cond && (!cur_ops->get_state || !cur_ops->cond_sync))
875 		pr_alert("rcu_torture_writer: gp_cond without primitives.\n");
876 	if (gp_exp1 && cur_ops->exp_sync)
877 		synctype[nsynctypes++] = RTWS_EXP_SYNC;
878 	else if (gp_exp && !cur_ops->exp_sync)
879 		pr_alert("rcu_torture_writer: gp_exp without primitives.\n");
880 	if (gp_normal1 && cur_ops->deferred_free)
881 		synctype[nsynctypes++] = RTWS_DEF_FREE;
882 	else if (gp_normal && !cur_ops->deferred_free)
883 		pr_alert("rcu_torture_writer: gp_normal without primitives.\n");
884 	if (gp_sync1 && cur_ops->sync)
885 		synctype[nsynctypes++] = RTWS_SYNC;
886 	else if (gp_sync && !cur_ops->sync)
887 		pr_alert("rcu_torture_writer: gp_sync without primitives.\n");
888 	if (WARN_ONCE(nsynctypes == 0,
889 		      "rcu_torture_writer: No update-side primitives.\n")) {
890 		/*
891 		 * No updates primitives, so don't try updating.
892 		 * The resulting test won't be testing much, hence the
893 		 * above WARN_ONCE().
894 		 */
895 		rcu_torture_writer_state = RTWS_STOPPING;
896 		torture_kthread_stopping("rcu_torture_writer");
897 	}
898 
899 	do {
900 		rcu_torture_writer_state = RTWS_FIXED_DELAY;
901 		schedule_timeout_uninterruptible(1);
902 		rp = rcu_torture_alloc();
903 		if (rp == NULL)
904 			continue;
905 		rp->rtort_pipe_count = 0;
906 		rcu_torture_writer_state = RTWS_DELAY;
907 		udelay(torture_random(&rand) & 0x3ff);
908 		rcu_torture_writer_state = RTWS_REPLACE;
909 		old_rp = rcu_dereference_check(rcu_torture_current,
910 					       current == writer_task);
911 		rp->rtort_mbtest = 1;
912 		rcu_assign_pointer(rcu_torture_current, rp);
913 		smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
914 		if (old_rp) {
915 			i = old_rp->rtort_pipe_count;
916 			if (i > RCU_TORTURE_PIPE_LEN)
917 				i = RCU_TORTURE_PIPE_LEN;
918 			atomic_inc(&rcu_torture_wcount[i]);
919 			old_rp->rtort_pipe_count++;
920 			switch (synctype[torture_random(&rand) % nsynctypes]) {
921 			case RTWS_DEF_FREE:
922 				rcu_torture_writer_state = RTWS_DEF_FREE;
923 				cur_ops->deferred_free(old_rp);
924 				break;
925 			case RTWS_EXP_SYNC:
926 				rcu_torture_writer_state = RTWS_EXP_SYNC;
927 				cur_ops->exp_sync();
928 				rcu_torture_pipe_update(old_rp);
929 				break;
930 			case RTWS_COND_GET:
931 				rcu_torture_writer_state = RTWS_COND_GET;
932 				gp_snap = cur_ops->get_state();
933 				i = torture_random(&rand) % 16;
934 				if (i != 0)
935 					schedule_timeout_interruptible(i);
936 				udelay(torture_random(&rand) % 1000);
937 				rcu_torture_writer_state = RTWS_COND_SYNC;
938 				cur_ops->cond_sync(gp_snap);
939 				rcu_torture_pipe_update(old_rp);
940 				break;
941 			case RTWS_SYNC:
942 				rcu_torture_writer_state = RTWS_SYNC;
943 				cur_ops->sync();
944 				rcu_torture_pipe_update(old_rp);
945 				break;
946 			default:
947 				WARN_ON_ONCE(1);
948 				break;
949 			}
950 		}
951 		rcutorture_record_progress(++rcu_torture_current_version);
952 		rcu_torture_writer_state = RTWS_STUTTER;
953 		stutter_wait("rcu_torture_writer");
954 	} while (!torture_must_stop());
955 	rcu_torture_writer_state = RTWS_STOPPING;
956 	torture_kthread_stopping("rcu_torture_writer");
957 	return 0;
958 }
959 
960 /*
961  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
962  * delay between calls.
963  */
964 static int
965 rcu_torture_fakewriter(void *arg)
966 {
967 	DEFINE_TORTURE_RANDOM(rand);
968 
969 	VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
970 	set_user_nice(current, MAX_NICE);
971 
972 	do {
973 		schedule_timeout_uninterruptible(1 + torture_random(&rand)%10);
974 		udelay(torture_random(&rand) & 0x3ff);
975 		if (cur_ops->cb_barrier != NULL &&
976 		    torture_random(&rand) % (nfakewriters * 8) == 0) {
977 			cur_ops->cb_barrier();
978 		} else if (gp_normal == gp_exp) {
979 			if (torture_random(&rand) & 0x80)
980 				cur_ops->sync();
981 			else
982 				cur_ops->exp_sync();
983 		} else if (gp_normal) {
984 			cur_ops->sync();
985 		} else {
986 			cur_ops->exp_sync();
987 		}
988 		stutter_wait("rcu_torture_fakewriter");
989 	} while (!torture_must_stop());
990 
991 	torture_kthread_stopping("rcu_torture_fakewriter");
992 	return 0;
993 }
994 
995 static void rcutorture_trace_dump(void)
996 {
997 	static atomic_t beenhere = ATOMIC_INIT(0);
998 
999 	if (atomic_read(&beenhere))
1000 		return;
1001 	if (atomic_xchg(&beenhere, 1) != 0)
1002 		return;
1003 	ftrace_dump(DUMP_ALL);
1004 }
1005 
1006 /*
1007  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
1008  * incrementing the corresponding element of the pipeline array.  The
1009  * counter in the element should never be greater than 1, otherwise, the
1010  * RCU implementation is broken.
1011  */
1012 static void rcu_torture_timer(unsigned long unused)
1013 {
1014 	int idx;
1015 	unsigned long started;
1016 	unsigned long completed;
1017 	static DEFINE_TORTURE_RANDOM(rand);
1018 	static DEFINE_SPINLOCK(rand_lock);
1019 	struct rcu_torture *p;
1020 	int pipe_count;
1021 	unsigned long long ts;
1022 
1023 	idx = cur_ops->readlock();
1024 	if (cur_ops->started)
1025 		started = cur_ops->started();
1026 	else
1027 		started = cur_ops->completed();
1028 	ts = rcu_trace_clock_local();
1029 	p = rcu_dereference_check(rcu_torture_current,
1030 				  rcu_read_lock_bh_held() ||
1031 				  rcu_read_lock_sched_held() ||
1032 				  srcu_read_lock_held(&srcu_ctl));
1033 	if (p == NULL) {
1034 		/* Leave because rcu_torture_writer is not yet underway */
1035 		cur_ops->readunlock(idx);
1036 		return;
1037 	}
1038 	if (p->rtort_mbtest == 0)
1039 		atomic_inc(&n_rcu_torture_mberror);
1040 	spin_lock(&rand_lock);
1041 	cur_ops->read_delay(&rand);
1042 	n_rcu_torture_timers++;
1043 	spin_unlock(&rand_lock);
1044 	preempt_disable();
1045 	pipe_count = p->rtort_pipe_count;
1046 	if (pipe_count > RCU_TORTURE_PIPE_LEN) {
1047 		/* Should not happen, but... */
1048 		pipe_count = RCU_TORTURE_PIPE_LEN;
1049 	}
1050 	completed = cur_ops->completed();
1051 	if (pipe_count > 1) {
1052 		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts,
1053 					  started, completed);
1054 		rcutorture_trace_dump();
1055 	}
1056 	__this_cpu_inc(rcu_torture_count[pipe_count]);
1057 	completed = completed - started;
1058 	if (cur_ops->started)
1059 		completed++;
1060 	if (completed > RCU_TORTURE_PIPE_LEN) {
1061 		/* Should not happen, but... */
1062 		completed = RCU_TORTURE_PIPE_LEN;
1063 	}
1064 	__this_cpu_inc(rcu_torture_batch[completed]);
1065 	preempt_enable();
1066 	cur_ops->readunlock(idx);
1067 }
1068 
1069 /*
1070  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
1071  * incrementing the corresponding element of the pipeline array.  The
1072  * counter in the element should never be greater than 1, otherwise, the
1073  * RCU implementation is broken.
1074  */
1075 static int
1076 rcu_torture_reader(void *arg)
1077 {
1078 	unsigned long started;
1079 	unsigned long completed;
1080 	int idx;
1081 	DEFINE_TORTURE_RANDOM(rand);
1082 	struct rcu_torture *p;
1083 	int pipe_count;
1084 	struct timer_list t;
1085 	unsigned long long ts;
1086 
1087 	VERBOSE_TOROUT_STRING("rcu_torture_reader task started");
1088 	set_user_nice(current, MAX_NICE);
1089 	if (irqreader && cur_ops->irq_capable)
1090 		setup_timer_on_stack(&t, rcu_torture_timer, 0);
1091 
1092 	do {
1093 		if (irqreader && cur_ops->irq_capable) {
1094 			if (!timer_pending(&t))
1095 				mod_timer(&t, jiffies + 1);
1096 		}
1097 		idx = cur_ops->readlock();
1098 		if (cur_ops->started)
1099 			started = cur_ops->started();
1100 		else
1101 			started = cur_ops->completed();
1102 		ts = rcu_trace_clock_local();
1103 		p = rcu_dereference_check(rcu_torture_current,
1104 					  rcu_read_lock_bh_held() ||
1105 					  rcu_read_lock_sched_held() ||
1106 					  srcu_read_lock_held(&srcu_ctl));
1107 		if (p == NULL) {
1108 			/* Wait for rcu_torture_writer to get underway */
1109 			cur_ops->readunlock(idx);
1110 			schedule_timeout_interruptible(HZ);
1111 			continue;
1112 		}
1113 		if (p->rtort_mbtest == 0)
1114 			atomic_inc(&n_rcu_torture_mberror);
1115 		cur_ops->read_delay(&rand);
1116 		preempt_disable();
1117 		pipe_count = p->rtort_pipe_count;
1118 		if (pipe_count > RCU_TORTURE_PIPE_LEN) {
1119 			/* Should not happen, but... */
1120 			pipe_count = RCU_TORTURE_PIPE_LEN;
1121 		}
1122 		completed = cur_ops->completed();
1123 		if (pipe_count > 1) {
1124 			do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
1125 						  ts, started, completed);
1126 			rcutorture_trace_dump();
1127 		}
1128 		__this_cpu_inc(rcu_torture_count[pipe_count]);
1129 		completed = completed - started;
1130 		if (cur_ops->started)
1131 			completed++;
1132 		if (completed > RCU_TORTURE_PIPE_LEN) {
1133 			/* Should not happen, but... */
1134 			completed = RCU_TORTURE_PIPE_LEN;
1135 		}
1136 		__this_cpu_inc(rcu_torture_batch[completed]);
1137 		preempt_enable();
1138 		cur_ops->readunlock(idx);
1139 		cond_resched_rcu_qs();
1140 		stutter_wait("rcu_torture_reader");
1141 	} while (!torture_must_stop());
1142 	if (irqreader && cur_ops->irq_capable) {
1143 		del_timer_sync(&t);
1144 		destroy_timer_on_stack(&t);
1145 	}
1146 	torture_kthread_stopping("rcu_torture_reader");
1147 	return 0;
1148 }
1149 
1150 /*
1151  * Print torture statistics.  Caller must ensure that there is only
1152  * one call to this function at a given time!!!  This is normally
1153  * accomplished by relying on the module system to only have one copy
1154  * of the module loaded, and then by giving the rcu_torture_stats
1155  * kthread full control (or the init/cleanup functions when rcu_torture_stats
1156  * thread is not running).
1157  */
1158 static void
1159 rcu_torture_stats_print(void)
1160 {
1161 	int cpu;
1162 	int i;
1163 	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1164 	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1165 	static unsigned long rtcv_snap = ULONG_MAX;
1166 
1167 	for_each_possible_cpu(cpu) {
1168 		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1169 			pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
1170 			batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
1171 		}
1172 	}
1173 	for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
1174 		if (pipesummary[i] != 0)
1175 			break;
1176 	}
1177 
1178 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1179 	pr_cont("rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
1180 		rcu_torture_current,
1181 		rcu_torture_current_version,
1182 		list_empty(&rcu_torture_freelist),
1183 		atomic_read(&n_rcu_torture_alloc),
1184 		atomic_read(&n_rcu_torture_alloc_fail),
1185 		atomic_read(&n_rcu_torture_free));
1186 	pr_cont("rtmbe: %d rtbke: %ld rtbre: %ld ",
1187 		atomic_read(&n_rcu_torture_mberror),
1188 		n_rcu_torture_boost_ktrerror,
1189 		n_rcu_torture_boost_rterror);
1190 	pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
1191 		n_rcu_torture_boost_failure,
1192 		n_rcu_torture_boosts,
1193 		n_rcu_torture_timers);
1194 	torture_onoff_stats();
1195 	pr_cont("barrier: %ld/%ld:%ld ",
1196 		n_barrier_successes,
1197 		n_barrier_attempts,
1198 		n_rcu_torture_barrier_error);
1199 	pr_cont("cbflood: %ld\n", atomic_long_read(&n_cbfloods));
1200 
1201 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1202 	if (atomic_read(&n_rcu_torture_mberror) != 0 ||
1203 	    n_rcu_torture_barrier_error != 0 ||
1204 	    n_rcu_torture_boost_ktrerror != 0 ||
1205 	    n_rcu_torture_boost_rterror != 0 ||
1206 	    n_rcu_torture_boost_failure != 0 ||
1207 	    i > 1) {
1208 		pr_cont("%s", "!!! ");
1209 		atomic_inc(&n_rcu_torture_error);
1210 		WARN_ON_ONCE(1);
1211 	}
1212 	pr_cont("Reader Pipe: ");
1213 	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1214 		pr_cont(" %ld", pipesummary[i]);
1215 	pr_cont("\n");
1216 
1217 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1218 	pr_cont("Reader Batch: ");
1219 	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1220 		pr_cont(" %ld", batchsummary[i]);
1221 	pr_cont("\n");
1222 
1223 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1224 	pr_cont("Free-Block Circulation: ");
1225 	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1226 		pr_cont(" %d", atomic_read(&rcu_torture_wcount[i]));
1227 	}
1228 	pr_cont("\n");
1229 
1230 	if (cur_ops->stats)
1231 		cur_ops->stats();
1232 	if (rtcv_snap == rcu_torture_current_version &&
1233 	    rcu_torture_current != NULL) {
1234 		int __maybe_unused flags;
1235 		unsigned long __maybe_unused gpnum;
1236 		unsigned long __maybe_unused completed;
1237 
1238 		rcutorture_get_gp_data(cur_ops->ttype,
1239 				       &flags, &gpnum, &completed);
1240 		pr_alert("??? Writer stall state %d g%lu c%lu f%#x\n",
1241 			 rcu_torture_writer_state,
1242 			 gpnum, completed, flags);
1243 		show_rcu_gp_kthreads();
1244 		rcutorture_trace_dump();
1245 	}
1246 	rtcv_snap = rcu_torture_current_version;
1247 }
1248 
1249 /*
1250  * Periodically prints torture statistics, if periodic statistics printing
1251  * was specified via the stat_interval module parameter.
1252  */
1253 static int
1254 rcu_torture_stats(void *arg)
1255 {
1256 	VERBOSE_TOROUT_STRING("rcu_torture_stats task started");
1257 	do {
1258 		schedule_timeout_interruptible(stat_interval * HZ);
1259 		rcu_torture_stats_print();
1260 		torture_shutdown_absorb("rcu_torture_stats");
1261 	} while (!torture_must_stop());
1262 	torture_kthread_stopping("rcu_torture_stats");
1263 	return 0;
1264 }
1265 
1266 static inline void
1267 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
1268 {
1269 	pr_alert("%s" TORTURE_FLAG
1270 		 "--- %s: nreaders=%d nfakewriters=%d "
1271 		 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
1272 		 "shuffle_interval=%d stutter=%d irqreader=%d "
1273 		 "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
1274 		 "test_boost=%d/%d test_boost_interval=%d "
1275 		 "test_boost_duration=%d shutdown_secs=%d "
1276 		 "stall_cpu=%d stall_cpu_holdoff=%d "
1277 		 "n_barrier_cbs=%d "
1278 		 "onoff_interval=%d onoff_holdoff=%d\n",
1279 		 torture_type, tag, nrealreaders, nfakewriters,
1280 		 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
1281 		 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
1282 		 test_boost, cur_ops->can_boost,
1283 		 test_boost_interval, test_boost_duration, shutdown_secs,
1284 		 stall_cpu, stall_cpu_holdoff,
1285 		 n_barrier_cbs,
1286 		 onoff_interval, onoff_holdoff);
1287 }
1288 
1289 static void rcutorture_booster_cleanup(int cpu)
1290 {
1291 	struct task_struct *t;
1292 
1293 	if (boost_tasks[cpu] == NULL)
1294 		return;
1295 	mutex_lock(&boost_mutex);
1296 	t = boost_tasks[cpu];
1297 	boost_tasks[cpu] = NULL;
1298 	mutex_unlock(&boost_mutex);
1299 
1300 	/* This must be outside of the mutex, otherwise deadlock! */
1301 	torture_stop_kthread(rcu_torture_boost, t);
1302 }
1303 
1304 static int rcutorture_booster_init(int cpu)
1305 {
1306 	int retval;
1307 
1308 	if (boost_tasks[cpu] != NULL)
1309 		return 0;  /* Already created, nothing more to do. */
1310 
1311 	/* Don't allow time recalculation while creating a new task. */
1312 	mutex_lock(&boost_mutex);
1313 	VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
1314 	boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL,
1315 						  cpu_to_node(cpu),
1316 						  "rcu_torture_boost");
1317 	if (IS_ERR(boost_tasks[cpu])) {
1318 		retval = PTR_ERR(boost_tasks[cpu]);
1319 		VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed");
1320 		n_rcu_torture_boost_ktrerror++;
1321 		boost_tasks[cpu] = NULL;
1322 		mutex_unlock(&boost_mutex);
1323 		return retval;
1324 	}
1325 	kthread_bind(boost_tasks[cpu], cpu);
1326 	wake_up_process(boost_tasks[cpu]);
1327 	mutex_unlock(&boost_mutex);
1328 	return 0;
1329 }
1330 
1331 /*
1332  * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then
1333  * induces a CPU stall for the time specified by stall_cpu.
1334  */
1335 static int rcu_torture_stall(void *args)
1336 {
1337 	unsigned long stop_at;
1338 
1339 	VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
1340 	if (stall_cpu_holdoff > 0) {
1341 		VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
1342 		schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
1343 		VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
1344 	}
1345 	if (!kthread_should_stop()) {
1346 		stop_at = get_seconds() + stall_cpu;
1347 		/* RCU CPU stall is expected behavior in following code. */
1348 		pr_alert("rcu_torture_stall start.\n");
1349 		rcu_read_lock();
1350 		preempt_disable();
1351 		while (ULONG_CMP_LT(get_seconds(), stop_at))
1352 			continue;  /* Induce RCU CPU stall warning. */
1353 		preempt_enable();
1354 		rcu_read_unlock();
1355 		pr_alert("rcu_torture_stall end.\n");
1356 	}
1357 	torture_shutdown_absorb("rcu_torture_stall");
1358 	while (!kthread_should_stop())
1359 		schedule_timeout_interruptible(10 * HZ);
1360 	return 0;
1361 }
1362 
1363 /* Spawn CPU-stall kthread, if stall_cpu specified. */
1364 static int __init rcu_torture_stall_init(void)
1365 {
1366 	if (stall_cpu <= 0)
1367 		return 0;
1368 	return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
1369 }
1370 
1371 /* Callback function for RCU barrier testing. */
1372 static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
1373 {
1374 	atomic_inc(&barrier_cbs_invoked);
1375 }
1376 
1377 /* kthread function to register callbacks used to test RCU barriers. */
1378 static int rcu_torture_barrier_cbs(void *arg)
1379 {
1380 	long myid = (long)arg;
1381 	bool lastphase = 0;
1382 	bool newphase;
1383 	struct rcu_head rcu;
1384 
1385 	init_rcu_head_on_stack(&rcu);
1386 	VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started");
1387 	set_user_nice(current, MAX_NICE);
1388 	do {
1389 		wait_event(barrier_cbs_wq[myid],
1390 			   (newphase =
1391 			    ACCESS_ONCE(barrier_phase)) != lastphase ||
1392 			   torture_must_stop());
1393 		lastphase = newphase;
1394 		smp_mb(); /* ensure barrier_phase load before ->call(). */
1395 		if (torture_must_stop())
1396 			break;
1397 		cur_ops->call(&rcu, rcu_torture_barrier_cbf);
1398 		if (atomic_dec_and_test(&barrier_cbs_count))
1399 			wake_up(&barrier_wq);
1400 	} while (!torture_must_stop());
1401 	if (cur_ops->cb_barrier != NULL)
1402 		cur_ops->cb_barrier();
1403 	destroy_rcu_head_on_stack(&rcu);
1404 	torture_kthread_stopping("rcu_torture_barrier_cbs");
1405 	return 0;
1406 }
1407 
1408 /* kthread function to drive and coordinate RCU barrier testing. */
1409 static int rcu_torture_barrier(void *arg)
1410 {
1411 	int i;
1412 
1413 	VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting");
1414 	do {
1415 		atomic_set(&barrier_cbs_invoked, 0);
1416 		atomic_set(&barrier_cbs_count, n_barrier_cbs);
1417 		smp_mb(); /* Ensure barrier_phase after prior assignments. */
1418 		barrier_phase = !barrier_phase;
1419 		for (i = 0; i < n_barrier_cbs; i++)
1420 			wake_up(&barrier_cbs_wq[i]);
1421 		wait_event(barrier_wq,
1422 			   atomic_read(&barrier_cbs_count) == 0 ||
1423 			   torture_must_stop());
1424 		if (torture_must_stop())
1425 			break;
1426 		n_barrier_attempts++;
1427 		cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
1428 		if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
1429 			n_rcu_torture_barrier_error++;
1430 			pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
1431 			       atomic_read(&barrier_cbs_invoked),
1432 			       n_barrier_cbs);
1433 			WARN_ON_ONCE(1);
1434 		}
1435 		n_barrier_successes++;
1436 		schedule_timeout_interruptible(HZ / 10);
1437 	} while (!torture_must_stop());
1438 	torture_kthread_stopping("rcu_torture_barrier");
1439 	return 0;
1440 }
1441 
1442 /* Initialize RCU barrier testing. */
1443 static int rcu_torture_barrier_init(void)
1444 {
1445 	int i;
1446 	int ret;
1447 
1448 	if (n_barrier_cbs == 0)
1449 		return 0;
1450 	if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
1451 		pr_alert("%s" TORTURE_FLAG
1452 			 " Call or barrier ops missing for %s,\n",
1453 			 torture_type, cur_ops->name);
1454 		pr_alert("%s" TORTURE_FLAG
1455 			 " RCU barrier testing omitted from run.\n",
1456 			 torture_type);
1457 		return 0;
1458 	}
1459 	atomic_set(&barrier_cbs_count, 0);
1460 	atomic_set(&barrier_cbs_invoked, 0);
1461 	barrier_cbs_tasks =
1462 		kzalloc(n_barrier_cbs * sizeof(barrier_cbs_tasks[0]),
1463 			GFP_KERNEL);
1464 	barrier_cbs_wq =
1465 		kzalloc(n_barrier_cbs * sizeof(barrier_cbs_wq[0]),
1466 			GFP_KERNEL);
1467 	if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
1468 		return -ENOMEM;
1469 	for (i = 0; i < n_barrier_cbs; i++) {
1470 		init_waitqueue_head(&barrier_cbs_wq[i]);
1471 		ret = torture_create_kthread(rcu_torture_barrier_cbs,
1472 					     (void *)(long)i,
1473 					     barrier_cbs_tasks[i]);
1474 		if (ret)
1475 			return ret;
1476 	}
1477 	return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task);
1478 }
1479 
1480 /* Clean up after RCU barrier testing. */
1481 static void rcu_torture_barrier_cleanup(void)
1482 {
1483 	int i;
1484 
1485 	torture_stop_kthread(rcu_torture_barrier, barrier_task);
1486 	if (barrier_cbs_tasks != NULL) {
1487 		for (i = 0; i < n_barrier_cbs; i++)
1488 			torture_stop_kthread(rcu_torture_barrier_cbs,
1489 					     barrier_cbs_tasks[i]);
1490 		kfree(barrier_cbs_tasks);
1491 		barrier_cbs_tasks = NULL;
1492 	}
1493 	if (barrier_cbs_wq != NULL) {
1494 		kfree(barrier_cbs_wq);
1495 		barrier_cbs_wq = NULL;
1496 	}
1497 }
1498 
1499 static int rcutorture_cpu_notify(struct notifier_block *self,
1500 				 unsigned long action, void *hcpu)
1501 {
1502 	long cpu = (long)hcpu;
1503 
1504 	switch (action) {
1505 	case CPU_ONLINE:
1506 	case CPU_DOWN_FAILED:
1507 		(void)rcutorture_booster_init(cpu);
1508 		break;
1509 	case CPU_DOWN_PREPARE:
1510 		rcutorture_booster_cleanup(cpu);
1511 		break;
1512 	default:
1513 		break;
1514 	}
1515 	return NOTIFY_OK;
1516 }
1517 
1518 static struct notifier_block rcutorture_cpu_nb = {
1519 	.notifier_call = rcutorture_cpu_notify,
1520 };
1521 
1522 static void
1523 rcu_torture_cleanup(void)
1524 {
1525 	int i;
1526 
1527 	rcutorture_record_test_transition();
1528 	if (torture_cleanup_begin()) {
1529 		if (cur_ops->cb_barrier != NULL)
1530 			cur_ops->cb_barrier();
1531 		return;
1532 	}
1533 
1534 	rcu_torture_barrier_cleanup();
1535 	torture_stop_kthread(rcu_torture_stall, stall_task);
1536 	torture_stop_kthread(rcu_torture_writer, writer_task);
1537 
1538 	if (reader_tasks) {
1539 		for (i = 0; i < nrealreaders; i++)
1540 			torture_stop_kthread(rcu_torture_reader,
1541 					     reader_tasks[i]);
1542 		kfree(reader_tasks);
1543 	}
1544 	rcu_torture_current = NULL;
1545 
1546 	if (fakewriter_tasks) {
1547 		for (i = 0; i < nfakewriters; i++) {
1548 			torture_stop_kthread(rcu_torture_fakewriter,
1549 					     fakewriter_tasks[i]);
1550 		}
1551 		kfree(fakewriter_tasks);
1552 		fakewriter_tasks = NULL;
1553 	}
1554 
1555 	torture_stop_kthread(rcu_torture_stats, stats_task);
1556 	torture_stop_kthread(rcu_torture_fqs, fqs_task);
1557 	for (i = 0; i < ncbflooders; i++)
1558 		torture_stop_kthread(rcu_torture_cbflood, cbflood_task[i]);
1559 	if ((test_boost == 1 && cur_ops->can_boost) ||
1560 	    test_boost == 2) {
1561 		unregister_cpu_notifier(&rcutorture_cpu_nb);
1562 		for_each_possible_cpu(i)
1563 			rcutorture_booster_cleanup(i);
1564 	}
1565 
1566 	/* Wait for all RCU callbacks to fire.  */
1567 
1568 	if (cur_ops->cb_barrier != NULL)
1569 		cur_ops->cb_barrier();
1570 
1571 	rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
1572 
1573 	if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
1574 		rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
1575 	else if (torture_onoff_failures())
1576 		rcu_torture_print_module_parms(cur_ops,
1577 					       "End of test: RCU_HOTPLUG");
1578 	else
1579 		rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
1580 	torture_cleanup_end();
1581 }
1582 
1583 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
1584 static void rcu_torture_leak_cb(struct rcu_head *rhp)
1585 {
1586 }
1587 
1588 static void rcu_torture_err_cb(struct rcu_head *rhp)
1589 {
1590 	/*
1591 	 * This -might- happen due to race conditions, but is unlikely.
1592 	 * The scenario that leads to this happening is that the
1593 	 * first of the pair of duplicate callbacks is queued,
1594 	 * someone else starts a grace period that includes that
1595 	 * callback, then the second of the pair must wait for the
1596 	 * next grace period.  Unlikely, but can happen.  If it
1597 	 * does happen, the debug-objects subsystem won't have splatted.
1598 	 */
1599 	pr_alert("rcutorture: duplicated callback was invoked.\n");
1600 }
1601 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
1602 
1603 /*
1604  * Verify that double-free causes debug-objects to complain, but only
1605  * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.  Otherwise, say that the test
1606  * cannot be carried out.
1607  */
1608 static void rcu_test_debug_objects(void)
1609 {
1610 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
1611 	struct rcu_head rh1;
1612 	struct rcu_head rh2;
1613 
1614 	init_rcu_head_on_stack(&rh1);
1615 	init_rcu_head_on_stack(&rh2);
1616 	pr_alert("rcutorture: WARN: Duplicate call_rcu() test starting.\n");
1617 
1618 	/* Try to queue the rh2 pair of callbacks for the same grace period. */
1619 	preempt_disable(); /* Prevent preemption from interrupting test. */
1620 	rcu_read_lock(); /* Make it impossible to finish a grace period. */
1621 	call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */
1622 	local_irq_disable(); /* Make it harder to start a new grace period. */
1623 	call_rcu(&rh2, rcu_torture_leak_cb);
1624 	call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
1625 	local_irq_enable();
1626 	rcu_read_unlock();
1627 	preempt_enable();
1628 
1629 	/* Wait for them all to get done so we can safely return. */
1630 	rcu_barrier();
1631 	pr_alert("rcutorture: WARN: Duplicate call_rcu() test complete.\n");
1632 	destroy_rcu_head_on_stack(&rh1);
1633 	destroy_rcu_head_on_stack(&rh2);
1634 #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
1635 	pr_alert("rcutorture: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n");
1636 #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
1637 }
1638 
1639 static int __init
1640 rcu_torture_init(void)
1641 {
1642 	int i;
1643 	int cpu;
1644 	int firsterr = 0;
1645 	static struct rcu_torture_ops *torture_ops[] = {
1646 		&rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &sched_ops,
1647 		RCUTORTURE_TASKS_OPS
1648 	};
1649 
1650 	if (!torture_init_begin(torture_type, verbose, &torture_runnable))
1651 		return -EBUSY;
1652 
1653 	/* Process args and tell the world that the torturer is on the job. */
1654 	for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
1655 		cur_ops = torture_ops[i];
1656 		if (strcmp(torture_type, cur_ops->name) == 0)
1657 			break;
1658 	}
1659 	if (i == ARRAY_SIZE(torture_ops)) {
1660 		pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
1661 			 torture_type);
1662 		pr_alert("rcu-torture types:");
1663 		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
1664 			pr_alert(" %s", torture_ops[i]->name);
1665 		pr_alert("\n");
1666 		torture_init_end();
1667 		return -EINVAL;
1668 	}
1669 	if (cur_ops->fqs == NULL && fqs_duration != 0) {
1670 		pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
1671 		fqs_duration = 0;
1672 	}
1673 	if (cur_ops->init)
1674 		cur_ops->init(); /* no "goto unwind" prior to this point!!! */
1675 
1676 	if (nreaders >= 0) {
1677 		nrealreaders = nreaders;
1678 	} else {
1679 		nrealreaders = num_online_cpus() - 1;
1680 		if (nrealreaders <= 0)
1681 			nrealreaders = 1;
1682 	}
1683 	rcu_torture_print_module_parms(cur_ops, "Start of test");
1684 
1685 	/* Set up the freelist. */
1686 
1687 	INIT_LIST_HEAD(&rcu_torture_freelist);
1688 	for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
1689 		rcu_tortures[i].rtort_mbtest = 0;
1690 		list_add_tail(&rcu_tortures[i].rtort_free,
1691 			      &rcu_torture_freelist);
1692 	}
1693 
1694 	/* Initialize the statistics so that each run gets its own numbers. */
1695 
1696 	rcu_torture_current = NULL;
1697 	rcu_torture_current_version = 0;
1698 	atomic_set(&n_rcu_torture_alloc, 0);
1699 	atomic_set(&n_rcu_torture_alloc_fail, 0);
1700 	atomic_set(&n_rcu_torture_free, 0);
1701 	atomic_set(&n_rcu_torture_mberror, 0);
1702 	atomic_set(&n_rcu_torture_error, 0);
1703 	n_rcu_torture_barrier_error = 0;
1704 	n_rcu_torture_boost_ktrerror = 0;
1705 	n_rcu_torture_boost_rterror = 0;
1706 	n_rcu_torture_boost_failure = 0;
1707 	n_rcu_torture_boosts = 0;
1708 	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1709 		atomic_set(&rcu_torture_wcount[i], 0);
1710 	for_each_possible_cpu(cpu) {
1711 		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1712 			per_cpu(rcu_torture_count, cpu)[i] = 0;
1713 			per_cpu(rcu_torture_batch, cpu)[i] = 0;
1714 		}
1715 	}
1716 
1717 	/* Start up the kthreads. */
1718 
1719 	firsterr = torture_create_kthread(rcu_torture_writer, NULL,
1720 					  writer_task);
1721 	if (firsterr)
1722 		goto unwind;
1723 	fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
1724 				   GFP_KERNEL);
1725 	if (fakewriter_tasks == NULL) {
1726 		VERBOSE_TOROUT_ERRSTRING("out of memory");
1727 		firsterr = -ENOMEM;
1728 		goto unwind;
1729 	}
1730 	for (i = 0; i < nfakewriters; i++) {
1731 		firsterr = torture_create_kthread(rcu_torture_fakewriter,
1732 						  NULL, fakewriter_tasks[i]);
1733 		if (firsterr)
1734 			goto unwind;
1735 	}
1736 	reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
1737 			       GFP_KERNEL);
1738 	if (reader_tasks == NULL) {
1739 		VERBOSE_TOROUT_ERRSTRING("out of memory");
1740 		firsterr = -ENOMEM;
1741 		goto unwind;
1742 	}
1743 	for (i = 0; i < nrealreaders; i++) {
1744 		firsterr = torture_create_kthread(rcu_torture_reader, NULL,
1745 						  reader_tasks[i]);
1746 		if (firsterr)
1747 			goto unwind;
1748 	}
1749 	if (stat_interval > 0) {
1750 		firsterr = torture_create_kthread(rcu_torture_stats, NULL,
1751 						  stats_task);
1752 		if (firsterr)
1753 			goto unwind;
1754 	}
1755 	if (test_no_idle_hz) {
1756 		firsterr = torture_shuffle_init(shuffle_interval * HZ);
1757 		if (firsterr)
1758 			goto unwind;
1759 	}
1760 	if (stutter < 0)
1761 		stutter = 0;
1762 	if (stutter) {
1763 		firsterr = torture_stutter_init(stutter * HZ);
1764 		if (firsterr)
1765 			goto unwind;
1766 	}
1767 	if (fqs_duration < 0)
1768 		fqs_duration = 0;
1769 	if (fqs_duration) {
1770 		/* Create the fqs thread */
1771 		firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
1772 						  fqs_task);
1773 		if (firsterr)
1774 			goto unwind;
1775 	}
1776 	if (test_boost_interval < 1)
1777 		test_boost_interval = 1;
1778 	if (test_boost_duration < 2)
1779 		test_boost_duration = 2;
1780 	if ((test_boost == 1 && cur_ops->can_boost) ||
1781 	    test_boost == 2) {
1782 
1783 		boost_starttime = jiffies + test_boost_interval * HZ;
1784 		register_cpu_notifier(&rcutorture_cpu_nb);
1785 		for_each_possible_cpu(i) {
1786 			if (cpu_is_offline(i))
1787 				continue;  /* Heuristic: CPU can go offline. */
1788 			firsterr = rcutorture_booster_init(i);
1789 			if (firsterr)
1790 				goto unwind;
1791 		}
1792 	}
1793 	firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
1794 	if (firsterr)
1795 		goto unwind;
1796 	firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval * HZ);
1797 	if (firsterr)
1798 		goto unwind;
1799 	firsterr = rcu_torture_stall_init();
1800 	if (firsterr)
1801 		goto unwind;
1802 	firsterr = rcu_torture_barrier_init();
1803 	if (firsterr)
1804 		goto unwind;
1805 	if (object_debug)
1806 		rcu_test_debug_objects();
1807 	if (cbflood_n_burst > 0) {
1808 		/* Create the cbflood threads */
1809 		ncbflooders = (num_online_cpus() + 3) / 4;
1810 		cbflood_task = kcalloc(ncbflooders, sizeof(*cbflood_task),
1811 				       GFP_KERNEL);
1812 		if (!cbflood_task) {
1813 			VERBOSE_TOROUT_ERRSTRING("out of memory");
1814 			firsterr = -ENOMEM;
1815 			goto unwind;
1816 		}
1817 		for (i = 0; i < ncbflooders; i++) {
1818 			firsterr = torture_create_kthread(rcu_torture_cbflood,
1819 							  NULL,
1820 							  cbflood_task[i]);
1821 			if (firsterr)
1822 				goto unwind;
1823 		}
1824 	}
1825 	rcutorture_record_test_transition();
1826 	torture_init_end();
1827 	return 0;
1828 
1829 unwind:
1830 	torture_init_end();
1831 	rcu_torture_cleanup();
1832 	return firsterr;
1833 }
1834 
1835 module_init(rcu_torture_init);
1836 module_exit(rcu_torture_cleanup);
1837