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TOMOYO Linux Cross Reference
Linux/kernel/rcu/rcutorture.c

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

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