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Linux/kernel/rcu/rcutorture.c

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  1 // SPDX-License-Identifier: GPL-2.0+
  2 /*
  3  * Read-Copy Update module-based torture test facility
  4  *
  5  * Copyright (C) IBM Corporation, 2005, 2006
  6  *
  7  * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
  8  *        Josh Triplett <josh@joshtriplett.org>
  9  *
 10  * See also:  Documentation/RCU/torture.txt
 11  */
 12 
 13 #define pr_fmt(fmt) fmt
 14 
 15 #include <linux/types.h>
 16 #include <linux/kernel.h>
 17 #include <linux/init.h>
 18 #include <linux/module.h>
 19 #include <linux/kthread.h>
 20 #include <linux/err.h>
 21 #include <linux/spinlock.h>
 22 #include <linux/smp.h>
 23 #include <linux/rcupdate.h>
 24 #include <linux/interrupt.h>
 25 #include <linux/sched/signal.h>
 26 #include <uapi/linux/sched/types.h>
 27 #include <linux/atomic.h>
 28 #include <linux/bitops.h>
 29 #include <linux/completion.h>
 30 #include <linux/moduleparam.h>
 31 #include <linux/percpu.h>
 32 #include <linux/notifier.h>
 33 #include <linux/reboot.h>
 34 #include <linux/freezer.h>
 35 #include <linux/cpu.h>
 36 #include <linux/delay.h>
 37 #include <linux/stat.h>
 38 #include <linux/srcu.h>
 39 #include <linux/slab.h>
 40 #include <linux/trace_clock.h>
 41 #include <asm/byteorder.h>
 42 #include <linux/torture.h>
 43 #include <linux/vmalloc.h>
 44 #include <linux/sched/debug.h>
 45 #include <linux/sched/sysctl.h>
 46 #include <linux/oom.h>
 47 #include <linux/tick.h>
 48 
 49 #include "rcu.h"
 50 
 51 MODULE_LICENSE("GPL");
 52 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
 53 
 54 
 55 /* Bits for ->extendables field, extendables param, and related definitions. */
 56 #define RCUTORTURE_RDR_SHIFT     8      /* Put SRCU index in upper bits. */
 57 #define RCUTORTURE_RDR_MASK      ((1 << RCUTORTURE_RDR_SHIFT) - 1)
 58 #define RCUTORTURE_RDR_BH        0x01   /* Extend readers by disabling bh. */
 59 #define RCUTORTURE_RDR_IRQ       0x02   /*  ... disabling interrupts. */
 60 #define RCUTORTURE_RDR_PREEMPT   0x04   /*  ... disabling preemption. */
 61 #define RCUTORTURE_RDR_RBH       0x08   /*  ... rcu_read_lock_bh(). */
 62 #define RCUTORTURE_RDR_SCHED     0x10   /*  ... rcu_read_lock_sched(). */
 63 #define RCUTORTURE_RDR_RCU       0x20   /*  ... entering another RCU reader. */
 64 #define RCUTORTURE_RDR_NBITS     6      /* Number of bits defined above. */
 65 #define RCUTORTURE_MAX_EXTEND    \
 66         (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
 67          RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
 68 #define RCUTORTURE_RDR_MAX_LOOPS 0x7    /* Maximum reader extensions. */
 69                                         /* Must be power of two minus one. */
 70 #define RCUTORTURE_RDR_MAX_SEGS (RCUTORTURE_RDR_MAX_LOOPS + 3)
 71 
 72 torture_param(int, extendables, RCUTORTURE_MAX_EXTEND,
 73               "Extend readers by disabling bh (1), irqs (2), or preempt (4)");
 74 torture_param(int, fqs_duration, 0,
 75               "Duration of fqs bursts (us), 0 to disable");
 76 torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
 77 torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
 78 torture_param(bool, fwd_progress, 1, "Test grace-period forward progress");
 79 torture_param(int, fwd_progress_div, 4, "Fraction of CPU stall to wait");
 80 torture_param(int, fwd_progress_holdoff, 60,
 81               "Time between forward-progress tests (s)");
 82 torture_param(bool, fwd_progress_need_resched, 1,
 83               "Hide cond_resched() behind need_resched()");
 84 torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
 85 torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
 86 torture_param(bool, gp_normal, false,
 87              "Use normal (non-expedited) GP wait primitives");
 88 torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
 89 torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
 90 torture_param(int, n_barrier_cbs, 0,
 91              "# of callbacks/kthreads for barrier testing");
 92 torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
 93 torture_param(int, nreaders, -1, "Number of RCU reader threads");
 94 torture_param(int, object_debug, 0,
 95              "Enable debug-object double call_rcu() testing");
 96 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
 97 torture_param(int, onoff_interval, 0,
 98              "Time between CPU hotplugs (jiffies), 0=disable");
 99 torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
100 torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
101 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
102 torture_param(int, stall_cpu_holdoff, 10,
103              "Time to wait before starting stall (s).");
104 torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
105 torture_param(int, stat_interval, 60,
106              "Number of seconds between stats printk()s");
107 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
108 torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
109 torture_param(int, test_boost_duration, 4,
110              "Duration of each boost test, seconds.");
111 torture_param(int, test_boost_interval, 7,
112              "Interval between boost tests, seconds.");
113 torture_param(bool, test_no_idle_hz, true,
114              "Test support for tickless idle CPUs");
115 torture_param(int, verbose, 1,
116              "Enable verbose debugging printk()s");
117 
118 static char *torture_type = "rcu";
119 module_param(torture_type, charp, 0444);
120 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");
121 
122 static int nrealreaders;
123 static struct task_struct *writer_task;
124 static struct task_struct **fakewriter_tasks;
125 static struct task_struct **reader_tasks;
126 static struct task_struct *stats_task;
127 static struct task_struct *fqs_task;
128 static struct task_struct *boost_tasks[NR_CPUS];
129 static struct task_struct *stall_task;
130 static struct task_struct *fwd_prog_task;
131 static struct task_struct **barrier_cbs_tasks;
132 static struct task_struct *barrier_task;
133 
134 #define RCU_TORTURE_PIPE_LEN 10
135 
136 struct rcu_torture {
137         struct rcu_head rtort_rcu;
138         int rtort_pipe_count;
139         struct list_head rtort_free;
140         int rtort_mbtest;
141 };
142 
143 static LIST_HEAD(rcu_torture_freelist);
144 static struct rcu_torture __rcu *rcu_torture_current;
145 static unsigned long rcu_torture_current_version;
146 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
147 static DEFINE_SPINLOCK(rcu_torture_lock);
148 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
149 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
150 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
151 static atomic_t n_rcu_torture_alloc;
152 static atomic_t n_rcu_torture_alloc_fail;
153 static atomic_t n_rcu_torture_free;
154 static atomic_t n_rcu_torture_mberror;
155 static atomic_t n_rcu_torture_error;
156 static long n_rcu_torture_barrier_error;
157 static long n_rcu_torture_boost_ktrerror;
158 static long n_rcu_torture_boost_rterror;
159 static long n_rcu_torture_boost_failure;
160 static long n_rcu_torture_boosts;
161 static atomic_long_t n_rcu_torture_timers;
162 static long n_barrier_attempts;
163 static long n_barrier_successes; /* did rcu_barrier test succeed? */
164 static struct list_head rcu_torture_removed;
165 static unsigned long shutdown_jiffies;
166 
167 static int rcu_torture_writer_state;
168 #define RTWS_FIXED_DELAY        0
169 #define RTWS_DELAY              1
170 #define RTWS_REPLACE            2
171 #define RTWS_DEF_FREE           3
172 #define RTWS_EXP_SYNC           4
173 #define RTWS_COND_GET           5
174 #define RTWS_COND_SYNC          6
175 #define RTWS_SYNC               7
176 #define RTWS_STUTTER            8
177 #define RTWS_STOPPING           9
178 static const char * const rcu_torture_writer_state_names[] = {
179         "RTWS_FIXED_DELAY",
180         "RTWS_DELAY",
181         "RTWS_REPLACE",
182         "RTWS_DEF_FREE",
183         "RTWS_EXP_SYNC",
184         "RTWS_COND_GET",
185         "RTWS_COND_SYNC",
186         "RTWS_SYNC",
187         "RTWS_STUTTER",
188         "RTWS_STOPPING",
189 };
190 
191 /* Record reader segment types and duration for first failing read. */
192 struct rt_read_seg {
193         int rt_readstate;
194         unsigned long rt_delay_jiffies;
195         unsigned long rt_delay_ms;
196         unsigned long rt_delay_us;
197         bool rt_preempted;
198 };
199 static int err_segs_recorded;
200 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
201 static int rt_read_nsegs;
202 
203 static const char *rcu_torture_writer_state_getname(void)
204 {
205         unsigned int i = READ_ONCE(rcu_torture_writer_state);
206 
207         if (i >= ARRAY_SIZE(rcu_torture_writer_state_names))
208                 return "???";
209         return rcu_torture_writer_state_names[i];
210 }
211 
212 #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU)
213 #define rcu_can_boost() 1
214 #else /* #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
215 #define rcu_can_boost() 0
216 #endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
217 
218 #ifdef CONFIG_RCU_TRACE
219 static u64 notrace rcu_trace_clock_local(void)
220 {
221         u64 ts = trace_clock_local();
222 
223         (void)do_div(ts, NSEC_PER_USEC);
224         return ts;
225 }
226 #else /* #ifdef CONFIG_RCU_TRACE */
227 static u64 notrace rcu_trace_clock_local(void)
228 {
229         return 0ULL;
230 }
231 #endif /* #else #ifdef CONFIG_RCU_TRACE */
232 
233 /*
234  * Stop aggressive CPU-hog tests a bit before the end of the test in order
235  * to avoid interfering with test shutdown.
236  */
237 static bool shutdown_time_arrived(void)
238 {
239         return shutdown_secs && time_after(jiffies, shutdown_jiffies - 30 * HZ);
240 }
241 
242 static unsigned long boost_starttime;   /* jiffies of next boost test start. */
243 static DEFINE_MUTEX(boost_mutex);       /* protect setting boost_starttime */
244                                         /*  and boost task create/destroy. */
245 static atomic_t barrier_cbs_count;      /* Barrier callbacks registered. */
246 static bool barrier_phase;              /* Test phase. */
247 static atomic_t barrier_cbs_invoked;    /* Barrier callbacks invoked. */
248 static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
249 static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
250 
251 static bool rcu_fwd_cb_nodelay;         /* Short rcu_torture_delay() delays. */
252 
253 /*
254  * Allocate an element from the rcu_tortures pool.
255  */
256 static struct rcu_torture *
257 rcu_torture_alloc(void)
258 {
259         struct list_head *p;
260 
261         spin_lock_bh(&rcu_torture_lock);
262         if (list_empty(&rcu_torture_freelist)) {
263                 atomic_inc(&n_rcu_torture_alloc_fail);
264                 spin_unlock_bh(&rcu_torture_lock);
265                 return NULL;
266         }
267         atomic_inc(&n_rcu_torture_alloc);
268         p = rcu_torture_freelist.next;
269         list_del_init(p);
270         spin_unlock_bh(&rcu_torture_lock);
271         return container_of(p, struct rcu_torture, rtort_free);
272 }
273 
274 /*
275  * Free an element to the rcu_tortures pool.
276  */
277 static void
278 rcu_torture_free(struct rcu_torture *p)
279 {
280         atomic_inc(&n_rcu_torture_free);
281         spin_lock_bh(&rcu_torture_lock);
282         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
283         spin_unlock_bh(&rcu_torture_lock);
284 }
285 
286 /*
287  * Operations vector for selecting different types of tests.
288  */
289 
290 struct rcu_torture_ops {
291         int ttype;
292         void (*init)(void);
293         void (*cleanup)(void);
294         int (*readlock)(void);
295         void (*read_delay)(struct torture_random_state *rrsp,
296                            struct rt_read_seg *rtrsp);
297         void (*readunlock)(int idx);
298         unsigned long (*get_gp_seq)(void);
299         unsigned long (*gp_diff)(unsigned long new, unsigned long old);
300         void (*deferred_free)(struct rcu_torture *p);
301         void (*sync)(void);
302         void (*exp_sync)(void);
303         unsigned long (*get_state)(void);
304         void (*cond_sync)(unsigned long oldstate);
305         call_rcu_func_t call;
306         void (*cb_barrier)(void);
307         void (*fqs)(void);
308         void (*stats)(void);
309         int (*stall_dur)(void);
310         int irq_capable;
311         int can_boost;
312         int extendables;
313         int slow_gps;
314         const char *name;
315 };
316 
317 static struct rcu_torture_ops *cur_ops;
318 
319 /*
320  * Definitions for rcu torture testing.
321  */
322 
323 static int rcu_torture_read_lock(void) __acquires(RCU)
324 {
325         rcu_read_lock();
326         return 0;
327 }
328 
329 static void
330 rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
331 {
332         unsigned long started;
333         unsigned long completed;
334         const unsigned long shortdelay_us = 200;
335         unsigned long longdelay_ms = 300;
336         unsigned long long ts;
337 
338         /* We want a short delay sometimes to make a reader delay the grace
339          * period, and we want a long delay occasionally to trigger
340          * force_quiescent_state. */
341 
342         if (!rcu_fwd_cb_nodelay &&
343             !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
344                 started = cur_ops->get_gp_seq();
345                 ts = rcu_trace_clock_local();
346                 if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK))
347                         longdelay_ms = 5; /* Avoid triggering BH limits. */
348                 mdelay(longdelay_ms);
349                 rtrsp->rt_delay_ms = longdelay_ms;
350                 completed = cur_ops->get_gp_seq();
351                 do_trace_rcu_torture_read(cur_ops->name, NULL, ts,
352                                           started, completed);
353         }
354         if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) {
355                 udelay(shortdelay_us);
356                 rtrsp->rt_delay_us = shortdelay_us;
357         }
358         if (!preempt_count() &&
359             !(torture_random(rrsp) % (nrealreaders * 500))) {
360                 torture_preempt_schedule();  /* QS only if preemptible. */
361                 rtrsp->rt_preempted = true;
362         }
363 }
364 
365 static void rcu_torture_read_unlock(int idx) __releases(RCU)
366 {
367         rcu_read_unlock();
368 }
369 
370 /*
371  * Update callback in the pipe.  This should be invoked after a grace period.
372  */
373 static bool
374 rcu_torture_pipe_update_one(struct rcu_torture *rp)
375 {
376         int i;
377 
378         i = rp->rtort_pipe_count;
379         if (i > RCU_TORTURE_PIPE_LEN)
380                 i = RCU_TORTURE_PIPE_LEN;
381         atomic_inc(&rcu_torture_wcount[i]);
382         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
383                 rp->rtort_mbtest = 0;
384                 return true;
385         }
386         return false;
387 }
388 
389 /*
390  * Update all callbacks in the pipe.  Suitable for synchronous grace-period
391  * primitives.
392  */
393 static void
394 rcu_torture_pipe_update(struct rcu_torture *old_rp)
395 {
396         struct rcu_torture *rp;
397         struct rcu_torture *rp1;
398 
399         if (old_rp)
400                 list_add(&old_rp->rtort_free, &rcu_torture_removed);
401         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
402                 if (rcu_torture_pipe_update_one(rp)) {
403                         list_del(&rp->rtort_free);
404                         rcu_torture_free(rp);
405                 }
406         }
407 }
408 
409 static void
410 rcu_torture_cb(struct rcu_head *p)
411 {
412         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
413 
414         if (torture_must_stop_irq()) {
415                 /* Test is ending, just drop callbacks on the floor. */
416                 /* The next initialization will pick up the pieces. */
417                 return;
418         }
419         if (rcu_torture_pipe_update_one(rp))
420                 rcu_torture_free(rp);
421         else
422                 cur_ops->deferred_free(rp);
423 }
424 
425 static unsigned long rcu_no_completed(void)
426 {
427         return 0;
428 }
429 
430 static void rcu_torture_deferred_free(struct rcu_torture *p)
431 {
432         call_rcu(&p->rtort_rcu, rcu_torture_cb);
433 }
434 
435 static void rcu_sync_torture_init(void)
436 {
437         INIT_LIST_HEAD(&rcu_torture_removed);
438 }
439 
440 static struct rcu_torture_ops rcu_ops = {
441         .ttype          = RCU_FLAVOR,
442         .init           = rcu_sync_torture_init,
443         .readlock       = rcu_torture_read_lock,
444         .read_delay     = rcu_read_delay,
445         .readunlock     = rcu_torture_read_unlock,
446         .get_gp_seq     = rcu_get_gp_seq,
447         .gp_diff        = rcu_seq_diff,
448         .deferred_free  = rcu_torture_deferred_free,
449         .sync           = synchronize_rcu,
450         .exp_sync       = synchronize_rcu_expedited,
451         .get_state      = get_state_synchronize_rcu,
452         .cond_sync      = cond_synchronize_rcu,
453         .call           = call_rcu,
454         .cb_barrier     = rcu_barrier,
455         .fqs            = rcu_force_quiescent_state,
456         .stats          = NULL,
457         .stall_dur      = rcu_jiffies_till_stall_check,
458         .irq_capable    = 1,
459         .can_boost      = rcu_can_boost(),
460         .extendables    = RCUTORTURE_MAX_EXTEND,
461         .name           = "rcu"
462 };
463 
464 /*
465  * Don't even think about trying any of these in real life!!!
466  * The names includes "busted", and they really means it!
467  * The only purpose of these functions is to provide a buggy RCU
468  * implementation to make sure that rcutorture correctly emits
469  * buggy-RCU error messages.
470  */
471 static void rcu_busted_torture_deferred_free(struct rcu_torture *p)
472 {
473         /* This is a deliberate bug for testing purposes only! */
474         rcu_torture_cb(&p->rtort_rcu);
475 }
476 
477 static void synchronize_rcu_busted(void)
478 {
479         /* This is a deliberate bug for testing purposes only! */
480 }
481 
482 static void
483 call_rcu_busted(struct rcu_head *head, rcu_callback_t func)
484 {
485         /* This is a deliberate bug for testing purposes only! */
486         func(head);
487 }
488 
489 static struct rcu_torture_ops rcu_busted_ops = {
490         .ttype          = INVALID_RCU_FLAVOR,
491         .init           = rcu_sync_torture_init,
492         .readlock       = rcu_torture_read_lock,
493         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
494         .readunlock     = rcu_torture_read_unlock,
495         .get_gp_seq     = rcu_no_completed,
496         .deferred_free  = rcu_busted_torture_deferred_free,
497         .sync           = synchronize_rcu_busted,
498         .exp_sync       = synchronize_rcu_busted,
499         .call           = call_rcu_busted,
500         .cb_barrier     = NULL,
501         .fqs            = NULL,
502         .stats          = NULL,
503         .irq_capable    = 1,
504         .name           = "busted"
505 };
506 
507 /*
508  * Definitions for srcu torture testing.
509  */
510 
511 DEFINE_STATIC_SRCU(srcu_ctl);
512 static struct srcu_struct srcu_ctld;
513 static struct srcu_struct *srcu_ctlp = &srcu_ctl;
514 
515 static int srcu_torture_read_lock(void) __acquires(srcu_ctlp)
516 {
517         return srcu_read_lock(srcu_ctlp);
518 }
519 
520 static void
521 srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
522 {
523         long delay;
524         const long uspertick = 1000000 / HZ;
525         const long longdelay = 10;
526 
527         /* We want there to be long-running readers, but not all the time. */
528 
529         delay = torture_random(rrsp) %
530                 (nrealreaders * 2 * longdelay * uspertick);
531         if (!delay && in_task()) {
532                 schedule_timeout_interruptible(longdelay);
533                 rtrsp->rt_delay_jiffies = longdelay;
534         } else {
535                 rcu_read_delay(rrsp, rtrsp);
536         }
537 }
538 
539 static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp)
540 {
541         srcu_read_unlock(srcu_ctlp, idx);
542 }
543 
544 static unsigned long srcu_torture_completed(void)
545 {
546         return srcu_batches_completed(srcu_ctlp);
547 }
548 
549 static void srcu_torture_deferred_free(struct rcu_torture *rp)
550 {
551         call_srcu(srcu_ctlp, &rp->rtort_rcu, rcu_torture_cb);
552 }
553 
554 static void srcu_torture_synchronize(void)
555 {
556         synchronize_srcu(srcu_ctlp);
557 }
558 
559 static void srcu_torture_call(struct rcu_head *head,
560                               rcu_callback_t func)
561 {
562         call_srcu(srcu_ctlp, head, func);
563 }
564 
565 static void srcu_torture_barrier(void)
566 {
567         srcu_barrier(srcu_ctlp);
568 }
569 
570 static void srcu_torture_stats(void)
571 {
572         srcu_torture_stats_print(srcu_ctlp, torture_type, TORTURE_FLAG);
573 }
574 
575 static void srcu_torture_synchronize_expedited(void)
576 {
577         synchronize_srcu_expedited(srcu_ctlp);
578 }
579 
580 static struct rcu_torture_ops srcu_ops = {
581         .ttype          = SRCU_FLAVOR,
582         .init           = rcu_sync_torture_init,
583         .readlock       = srcu_torture_read_lock,
584         .read_delay     = srcu_read_delay,
585         .readunlock     = srcu_torture_read_unlock,
586         .get_gp_seq     = srcu_torture_completed,
587         .deferred_free  = srcu_torture_deferred_free,
588         .sync           = srcu_torture_synchronize,
589         .exp_sync       = srcu_torture_synchronize_expedited,
590         .call           = srcu_torture_call,
591         .cb_barrier     = srcu_torture_barrier,
592         .stats          = srcu_torture_stats,
593         .irq_capable    = 1,
594         .name           = "srcu"
595 };
596 
597 static void srcu_torture_init(void)
598 {
599         rcu_sync_torture_init();
600         WARN_ON(init_srcu_struct(&srcu_ctld));
601         srcu_ctlp = &srcu_ctld;
602 }
603 
604 static void srcu_torture_cleanup(void)
605 {
606         cleanup_srcu_struct(&srcu_ctld);
607         srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
608 }
609 
610 /* As above, but dynamically allocated. */
611 static struct rcu_torture_ops srcud_ops = {
612         .ttype          = SRCU_FLAVOR,
613         .init           = srcu_torture_init,
614         .cleanup        = srcu_torture_cleanup,
615         .readlock       = srcu_torture_read_lock,
616         .read_delay     = srcu_read_delay,
617         .readunlock     = srcu_torture_read_unlock,
618         .get_gp_seq     = srcu_torture_completed,
619         .deferred_free  = srcu_torture_deferred_free,
620         .sync           = srcu_torture_synchronize,
621         .exp_sync       = srcu_torture_synchronize_expedited,
622         .call           = srcu_torture_call,
623         .cb_barrier     = srcu_torture_barrier,
624         .stats          = srcu_torture_stats,
625         .irq_capable    = 1,
626         .name           = "srcud"
627 };
628 
629 /* As above, but broken due to inappropriate reader extension. */
630 static struct rcu_torture_ops busted_srcud_ops = {
631         .ttype          = SRCU_FLAVOR,
632         .init           = srcu_torture_init,
633         .cleanup        = srcu_torture_cleanup,
634         .readlock       = srcu_torture_read_lock,
635         .read_delay     = rcu_read_delay,
636         .readunlock     = srcu_torture_read_unlock,
637         .get_gp_seq     = srcu_torture_completed,
638         .deferred_free  = srcu_torture_deferred_free,
639         .sync           = srcu_torture_synchronize,
640         .exp_sync       = srcu_torture_synchronize_expedited,
641         .call           = srcu_torture_call,
642         .cb_barrier     = srcu_torture_barrier,
643         .stats          = srcu_torture_stats,
644         .irq_capable    = 1,
645         .extendables    = RCUTORTURE_MAX_EXTEND,
646         .name           = "busted_srcud"
647 };
648 
649 /*
650  * Definitions for RCU-tasks torture testing.
651  */
652 
653 static int tasks_torture_read_lock(void)
654 {
655         return 0;
656 }
657 
658 static void tasks_torture_read_unlock(int idx)
659 {
660 }
661 
662 static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
663 {
664         call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
665 }
666 
667 static struct rcu_torture_ops tasks_ops = {
668         .ttype          = RCU_TASKS_FLAVOR,
669         .init           = rcu_sync_torture_init,
670         .readlock       = tasks_torture_read_lock,
671         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
672         .readunlock     = tasks_torture_read_unlock,
673         .get_gp_seq     = rcu_no_completed,
674         .deferred_free  = rcu_tasks_torture_deferred_free,
675         .sync           = synchronize_rcu_tasks,
676         .exp_sync       = synchronize_rcu_tasks,
677         .call           = call_rcu_tasks,
678         .cb_barrier     = rcu_barrier_tasks,
679         .fqs            = NULL,
680         .stats          = NULL,
681         .irq_capable    = 1,
682         .slow_gps       = 1,
683         .name           = "tasks"
684 };
685 
686 /*
687  * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
688  * This implementation does not necessarily work well with CPU hotplug.
689  */
690 
691 static void synchronize_rcu_trivial(void)
692 {
693         int cpu;
694 
695         for_each_online_cpu(cpu) {
696                 rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
697                 WARN_ON_ONCE(raw_smp_processor_id() != cpu);
698         }
699 }
700 
701 static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
702 {
703         preempt_disable();
704         return 0;
705 }
706 
707 static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
708 {
709         preempt_enable();
710 }
711 
712 static struct rcu_torture_ops trivial_ops = {
713         .ttype          = RCU_TRIVIAL_FLAVOR,
714         .init           = rcu_sync_torture_init,
715         .readlock       = rcu_torture_read_lock_trivial,
716         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
717         .readunlock     = rcu_torture_read_unlock_trivial,
718         .get_gp_seq     = rcu_no_completed,
719         .sync           = synchronize_rcu_trivial,
720         .exp_sync       = synchronize_rcu_trivial,
721         .fqs            = NULL,
722         .stats          = NULL,
723         .irq_capable    = 1,
724         .name           = "trivial"
725 };
726 
727 static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
728 {
729         if (!cur_ops->gp_diff)
730                 return new - old;
731         return cur_ops->gp_diff(new, old);
732 }
733 
734 static bool __maybe_unused torturing_tasks(void)
735 {
736         return cur_ops == &tasks_ops;
737 }
738 
739 /*
740  * RCU torture priority-boost testing.  Runs one real-time thread per
741  * CPU for moderate bursts, repeatedly registering RCU callbacks and
742  * spinning waiting for them to be invoked.  If a given callback takes
743  * too long to be invoked, we assume that priority inversion has occurred.
744  */
745 
746 struct rcu_boost_inflight {
747         struct rcu_head rcu;
748         int inflight;
749 };
750 
751 static void rcu_torture_boost_cb(struct rcu_head *head)
752 {
753         struct rcu_boost_inflight *rbip =
754                 container_of(head, struct rcu_boost_inflight, rcu);
755 
756         /* Ensure RCU-core accesses precede clearing ->inflight */
757         smp_store_release(&rbip->inflight, 0);
758 }
759 
760 static int old_rt_runtime = -1;
761 
762 static void rcu_torture_disable_rt_throttle(void)
763 {
764         /*
765          * Disable RT throttling so that rcutorture's boost threads don't get
766          * throttled. Only possible if rcutorture is built-in otherwise the
767          * user should manually do this by setting the sched_rt_period_us and
768          * sched_rt_runtime sysctls.
769          */
770         if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime != -1)
771                 return;
772 
773         old_rt_runtime = sysctl_sched_rt_runtime;
774         sysctl_sched_rt_runtime = -1;
775 }
776 
777 static void rcu_torture_enable_rt_throttle(void)
778 {
779         if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime == -1)
780                 return;
781 
782         sysctl_sched_rt_runtime = old_rt_runtime;
783         old_rt_runtime = -1;
784 }
785 
786 static bool rcu_torture_boost_failed(unsigned long start, unsigned long end)
787 {
788         if (end - start > test_boost_duration * HZ - HZ / 2) {
789                 VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");
790                 n_rcu_torture_boost_failure++;
791 
792                 return true; /* failed */
793         }
794 
795         return false; /* passed */
796 }
797 
798 static int rcu_torture_boost(void *arg)
799 {
800         unsigned long call_rcu_time;
801         unsigned long endtime;
802         unsigned long oldstarttime;
803         struct rcu_boost_inflight rbi = { .inflight = 0 };
804         struct sched_param sp;
805 
806         VERBOSE_TOROUT_STRING("rcu_torture_boost started");
807 
808         /* Set real-time priority. */
809         sp.sched_priority = 1;
810         if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) {
811                 VERBOSE_TOROUT_STRING("rcu_torture_boost RT prio failed!");
812                 n_rcu_torture_boost_rterror++;
813         }
814 
815         init_rcu_head_on_stack(&rbi.rcu);
816         /* Each pass through the following loop does one boost-test cycle. */
817         do {
818                 /* Track if the test failed already in this test interval? */
819                 bool failed = false;
820 
821                 /* Increment n_rcu_torture_boosts once per boost-test */
822                 while (!kthread_should_stop()) {
823                         if (mutex_trylock(&boost_mutex)) {
824                                 n_rcu_torture_boosts++;
825                                 mutex_unlock(&boost_mutex);
826                                 break;
827                         }
828                         schedule_timeout_uninterruptible(1);
829                 }
830                 if (kthread_should_stop())
831                         goto checkwait;
832 
833                 /* Wait for the next test interval. */
834                 oldstarttime = boost_starttime;
835                 while (ULONG_CMP_LT(jiffies, oldstarttime)) {
836                         schedule_timeout_interruptible(oldstarttime - jiffies);
837                         stutter_wait("rcu_torture_boost");
838                         if (torture_must_stop())
839                                 goto checkwait;
840                 }
841 
842                 /* Do one boost-test interval. */
843                 endtime = oldstarttime + test_boost_duration * HZ;
844                 call_rcu_time = jiffies;
845                 while (ULONG_CMP_LT(jiffies, endtime)) {
846                         /* If we don't have a callback in flight, post one. */
847                         if (!smp_load_acquire(&rbi.inflight)) {
848                                 /* RCU core before ->inflight = 1. */
849                                 smp_store_release(&rbi.inflight, 1);
850                                 call_rcu(&rbi.rcu, rcu_torture_boost_cb);
851                                 /* Check if the boost test failed */
852                                 failed = failed ||
853                                          rcu_torture_boost_failed(call_rcu_time,
854                                                                  jiffies);
855                                 call_rcu_time = jiffies;
856                         }
857                         stutter_wait("rcu_torture_boost");
858                         if (torture_must_stop())
859                                 goto checkwait;
860                 }
861 
862                 /*
863                  * If boost never happened, then inflight will always be 1, in
864                  * this case the boost check would never happen in the above
865                  * loop so do another one here.
866                  */
867                 if (!failed && smp_load_acquire(&rbi.inflight))
868                         rcu_torture_boost_failed(call_rcu_time, jiffies);
869 
870                 /*
871                  * Set the start time of the next test interval.
872                  * Yes, this is vulnerable to long delays, but such
873                  * delays simply cause a false negative for the next
874                  * interval.  Besides, we are running at RT priority,
875                  * so delays should be relatively rare.
876                  */
877                 while (oldstarttime == boost_starttime &&
878                        !kthread_should_stop()) {
879                         if (mutex_trylock(&boost_mutex)) {
880                                 boost_starttime = jiffies +
881                                                   test_boost_interval * HZ;
882                                 mutex_unlock(&boost_mutex);
883                                 break;
884                         }
885                         schedule_timeout_uninterruptible(1);
886                 }
887 
888                 /* Go do the stutter. */
889 checkwait:      stutter_wait("rcu_torture_boost");
890         } while (!torture_must_stop());
891 
892         /* Clean up and exit. */
893         while (!kthread_should_stop() || smp_load_acquire(&rbi.inflight)) {
894                 torture_shutdown_absorb("rcu_torture_boost");
895                 schedule_timeout_uninterruptible(1);
896         }
897         destroy_rcu_head_on_stack(&rbi.rcu);
898         torture_kthread_stopping("rcu_torture_boost");
899         return 0;
900 }
901 
902 /*
903  * RCU torture force-quiescent-state kthread.  Repeatedly induces
904  * bursts of calls to force_quiescent_state(), increasing the probability
905  * of occurrence of some important types of race conditions.
906  */
907 static int
908 rcu_torture_fqs(void *arg)
909 {
910         unsigned long fqs_resume_time;
911         int fqs_burst_remaining;
912 
913         VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
914         do {
915                 fqs_resume_time = jiffies + fqs_stutter * HZ;
916                 while (ULONG_CMP_LT(jiffies, fqs_resume_time) &&
917                        !kthread_should_stop()) {
918                         schedule_timeout_interruptible(1);
919                 }
920                 fqs_burst_remaining = fqs_duration;
921                 while (fqs_burst_remaining > 0 &&
922                        !kthread_should_stop()) {
923                         cur_ops->fqs();
924                         udelay(fqs_holdoff);
925                         fqs_burst_remaining -= fqs_holdoff;
926                 }
927                 stutter_wait("rcu_torture_fqs");
928         } while (!torture_must_stop());
929         torture_kthread_stopping("rcu_torture_fqs");
930         return 0;
931 }
932 
933 /*
934  * RCU torture writer kthread.  Repeatedly substitutes a new structure
935  * for that pointed to by rcu_torture_current, freeing the old structure
936  * after a series of grace periods (the "pipeline").
937  */
938 static int
939 rcu_torture_writer(void *arg)
940 {
941         bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
942         int expediting = 0;
943         unsigned long gp_snap;
944         bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
945         bool gp_sync1 = gp_sync;
946         int i;
947         struct rcu_torture *rp;
948         struct rcu_torture *old_rp;
949         static DEFINE_TORTURE_RANDOM(rand);
950         int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC,
951                            RTWS_COND_GET, RTWS_SYNC };
952         int nsynctypes = 0;
953 
954         VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
955         if (!can_expedite)
956                 pr_alert("%s" TORTURE_FLAG
957                          " GP expediting controlled from boot/sysfs for %s.\n",
958                          torture_type, cur_ops->name);
959 
960         /* Initialize synctype[] array.  If none set, take default. */
961         if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync1)
962                 gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true;
963         if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync) {
964                 synctype[nsynctypes++] = RTWS_COND_GET;
965                 pr_info("%s: Testing conditional GPs.\n", __func__);
966         } else if (gp_cond && (!cur_ops->get_state || !cur_ops->cond_sync)) {
967                 pr_alert("%s: gp_cond without primitives.\n", __func__);
968         }
969         if (gp_exp1 && cur_ops->exp_sync) {
970                 synctype[nsynctypes++] = RTWS_EXP_SYNC;
971                 pr_info("%s: Testing expedited GPs.\n", __func__);
972         } else if (gp_exp && !cur_ops->exp_sync) {
973                 pr_alert("%s: gp_exp without primitives.\n", __func__);
974         }
975         if (gp_normal1 && cur_ops->deferred_free) {
976                 synctype[nsynctypes++] = RTWS_DEF_FREE;
977                 pr_info("%s: Testing asynchronous GPs.\n", __func__);
978         } else if (gp_normal && !cur_ops->deferred_free) {
979                 pr_alert("%s: gp_normal without primitives.\n", __func__);
980         }
981         if (gp_sync1 && cur_ops->sync) {
982                 synctype[nsynctypes++] = RTWS_SYNC;
983                 pr_info("%s: Testing normal GPs.\n", __func__);
984         } else if (gp_sync && !cur_ops->sync) {
985                 pr_alert("%s: gp_sync without primitives.\n", __func__);
986         }
987         if (WARN_ONCE(nsynctypes == 0,
988                       "rcu_torture_writer: No update-side primitives.\n")) {
989                 /*
990                  * No updates primitives, so don't try updating.
991                  * The resulting test won't be testing much, hence the
992                  * above WARN_ONCE().
993                  */
994                 rcu_torture_writer_state = RTWS_STOPPING;
995                 torture_kthread_stopping("rcu_torture_writer");
996         }
997 
998         do {
999                 rcu_torture_writer_state = RTWS_FIXED_DELAY;
1000                 schedule_timeout_uninterruptible(1);
1001                 rp = rcu_torture_alloc();
1002                 if (rp == NULL)
1003                         continue;
1004                 rp->rtort_pipe_count = 0;
1005                 rcu_torture_writer_state = RTWS_DELAY;
1006                 udelay(torture_random(&rand) & 0x3ff);
1007                 rcu_torture_writer_state = RTWS_REPLACE;
1008                 old_rp = rcu_dereference_check(rcu_torture_current,
1009                                                current == writer_task);
1010                 rp->rtort_mbtest = 1;
1011                 rcu_assign_pointer(rcu_torture_current, rp);
1012                 smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
1013                 if (old_rp) {
1014                         i = old_rp->rtort_pipe_count;
1015                         if (i > RCU_TORTURE_PIPE_LEN)
1016                                 i = RCU_TORTURE_PIPE_LEN;
1017                         atomic_inc(&rcu_torture_wcount[i]);
1018                         old_rp->rtort_pipe_count++;
1019                         switch (synctype[torture_random(&rand) % nsynctypes]) {
1020                         case RTWS_DEF_FREE:
1021                                 rcu_torture_writer_state = RTWS_DEF_FREE;
1022                                 cur_ops->deferred_free(old_rp);
1023                                 break;
1024                         case RTWS_EXP_SYNC:
1025                                 rcu_torture_writer_state = RTWS_EXP_SYNC;
1026                                 cur_ops->exp_sync();
1027                                 rcu_torture_pipe_update(old_rp);
1028                                 break;
1029                         case RTWS_COND_GET:
1030                                 rcu_torture_writer_state = RTWS_COND_GET;
1031                                 gp_snap = cur_ops->get_state();
1032                                 i = torture_random(&rand) % 16;
1033                                 if (i != 0)
1034                                         schedule_timeout_interruptible(i);
1035                                 udelay(torture_random(&rand) % 1000);
1036                                 rcu_torture_writer_state = RTWS_COND_SYNC;
1037                                 cur_ops->cond_sync(gp_snap);
1038                                 rcu_torture_pipe_update(old_rp);
1039                                 break;
1040                         case RTWS_SYNC:
1041                                 rcu_torture_writer_state = RTWS_SYNC;
1042                                 cur_ops->sync();
1043                                 rcu_torture_pipe_update(old_rp);
1044                                 break;
1045                         default:
1046                                 WARN_ON_ONCE(1);
1047                                 break;
1048                         }
1049                 }
1050                 WRITE_ONCE(rcu_torture_current_version,
1051                            rcu_torture_current_version + 1);
1052                 /* Cycle through nesting levels of rcu_expedite_gp() calls. */
1053                 if (can_expedite &&
1054                     !(torture_random(&rand) & 0xff & (!!expediting - 1))) {
1055                         WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited());
1056                         if (expediting >= 0)
1057                                 rcu_expedite_gp();
1058                         else
1059                                 rcu_unexpedite_gp();
1060                         if (++expediting > 3)
1061                                 expediting = -expediting;
1062                 } else if (!can_expedite) { /* Disabled during boot, recheck. */
1063                         can_expedite = !rcu_gp_is_expedited() &&
1064                                        !rcu_gp_is_normal();
1065                 }
1066                 rcu_torture_writer_state = RTWS_STUTTER;
1067                 if (stutter_wait("rcu_torture_writer") &&
1068                     !READ_ONCE(rcu_fwd_cb_nodelay) &&
1069                     !cur_ops->slow_gps &&
1070                     !torture_must_stop())
1071                         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
1072                                 if (list_empty(&rcu_tortures[i].rtort_free) &&
1073                                     rcu_access_pointer(rcu_torture_current) !=
1074                                     &rcu_tortures[i]) {
1075                                         rcu_ftrace_dump(DUMP_ALL);
1076                                         WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
1077                                 }
1078         } while (!torture_must_stop());
1079         /* Reset expediting back to unexpedited. */
1080         if (expediting > 0)
1081                 expediting = -expediting;
1082         while (can_expedite && expediting++ < 0)
1083                 rcu_unexpedite_gp();
1084         WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited());
1085         if (!can_expedite)
1086                 pr_alert("%s" TORTURE_FLAG
1087                          " Dynamic grace-period expediting was disabled.\n",
1088                          torture_type);
1089         rcu_torture_writer_state = RTWS_STOPPING;
1090         torture_kthread_stopping("rcu_torture_writer");
1091         return 0;
1092 }
1093 
1094 /*
1095  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
1096  * delay between calls.
1097  */
1098 static int
1099 rcu_torture_fakewriter(void *arg)
1100 {
1101         DEFINE_TORTURE_RANDOM(rand);
1102 
1103         VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
1104         set_user_nice(current, MAX_NICE);
1105 
1106         do {
1107                 schedule_timeout_uninterruptible(1 + torture_random(&rand)%10);
1108                 udelay(torture_random(&rand) & 0x3ff);
1109                 if (cur_ops->cb_barrier != NULL &&
1110                     torture_random(&rand) % (nfakewriters * 8) == 0) {
1111                         cur_ops->cb_barrier();
1112                 } else if (gp_normal == gp_exp) {
1113                         if (cur_ops->sync && torture_random(&rand) & 0x80)
1114                                 cur_ops->sync();
1115                         else if (cur_ops->exp_sync)
1116                                 cur_ops->exp_sync();
1117                 } else if (gp_normal && cur_ops->sync) {
1118                         cur_ops->sync();
1119                 } else if (cur_ops->exp_sync) {
1120                         cur_ops->exp_sync();
1121                 }
1122                 stutter_wait("rcu_torture_fakewriter");
1123         } while (!torture_must_stop());
1124 
1125         torture_kthread_stopping("rcu_torture_fakewriter");
1126         return 0;
1127 }
1128 
1129 static void rcu_torture_timer_cb(struct rcu_head *rhp)
1130 {
1131         kfree(rhp);
1132 }
1133 
1134 /*
1135  * Do one extension of an RCU read-side critical section using the
1136  * current reader state in readstate (set to zero for initial entry
1137  * to extended critical section), set the new state as specified by
1138  * newstate (set to zero for final exit from extended critical section),
1139  * and random-number-generator state in trsp.  If this is neither the
1140  * beginning or end of the critical section and if there was actually a
1141  * change, do a ->read_delay().
1142  */
1143 static void rcutorture_one_extend(int *readstate, int newstate,
1144                                   struct torture_random_state *trsp,
1145                                   struct rt_read_seg *rtrsp)
1146 {
1147         int idxnew = -1;
1148         int idxold = *readstate;
1149         int statesnew = ~*readstate & newstate;
1150         int statesold = *readstate & ~newstate;
1151 
1152         WARN_ON_ONCE(idxold < 0);
1153         WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1);
1154         rtrsp->rt_readstate = newstate;
1155 
1156         /* First, put new protection in place to avoid critical-section gap. */
1157         if (statesnew & RCUTORTURE_RDR_BH)
1158                 local_bh_disable();
1159         if (statesnew & RCUTORTURE_RDR_IRQ)
1160                 local_irq_disable();
1161         if (statesnew & RCUTORTURE_RDR_PREEMPT)
1162                 preempt_disable();
1163         if (statesnew & RCUTORTURE_RDR_RBH)
1164                 rcu_read_lock_bh();
1165         if (statesnew & RCUTORTURE_RDR_SCHED)
1166                 rcu_read_lock_sched();
1167         if (statesnew & RCUTORTURE_RDR_RCU)
1168                 idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT;
1169 
1170         /* Next, remove old protection, irq first due to bh conflict. */
1171         if (statesold & RCUTORTURE_RDR_IRQ)
1172                 local_irq_enable();
1173         if (statesold & RCUTORTURE_RDR_BH)
1174                 local_bh_enable();
1175         if (statesold & RCUTORTURE_RDR_PREEMPT)
1176                 preempt_enable();
1177         if (statesold & RCUTORTURE_RDR_RBH)
1178                 rcu_read_unlock_bh();
1179         if (statesold & RCUTORTURE_RDR_SCHED)
1180                 rcu_read_unlock_sched();
1181         if (statesold & RCUTORTURE_RDR_RCU)
1182                 cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT);
1183 
1184         /* Delay if neither beginning nor end and there was a change. */
1185         if ((statesnew || statesold) && *readstate && newstate)
1186                 cur_ops->read_delay(trsp, rtrsp);
1187 
1188         /* Update the reader state. */
1189         if (idxnew == -1)
1190                 idxnew = idxold & ~RCUTORTURE_RDR_MASK;
1191         WARN_ON_ONCE(idxnew < 0);
1192         WARN_ON_ONCE((idxnew >> RCUTORTURE_RDR_SHIFT) > 1);
1193         *readstate = idxnew | newstate;
1194         WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) < 0);
1195         WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) > 1);
1196 }
1197 
1198 /* Return the biggest extendables mask given current RCU and boot parameters. */
1199 static int rcutorture_extend_mask_max(void)
1200 {
1201         int mask;
1202 
1203         WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND);
1204         mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables;
1205         mask = mask | RCUTORTURE_RDR_RCU;
1206         return mask;
1207 }
1208 
1209 /* Return a random protection state mask, but with at least one bit set. */
1210 static int
1211 rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
1212 {
1213         int mask = rcutorture_extend_mask_max();
1214         unsigned long randmask1 = torture_random(trsp) >> 8;
1215         unsigned long randmask2 = randmask1 >> 3;
1216 
1217         WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT);
1218         /* Mostly only one bit (need preemption!), sometimes lots of bits. */
1219         if (!(randmask1 & 0x7))
1220                 mask = mask & randmask2;
1221         else
1222                 mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));
1223         /* Can't enable bh w/irq disabled. */
1224         if ((mask & RCUTORTURE_RDR_IRQ) &&
1225             ((!(mask & RCUTORTURE_RDR_BH) && (oldmask & RCUTORTURE_RDR_BH)) ||
1226              (!(mask & RCUTORTURE_RDR_RBH) && (oldmask & RCUTORTURE_RDR_RBH))))
1227                 mask |= RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
1228         return mask ?: RCUTORTURE_RDR_RCU;
1229 }
1230 
1231 /*
1232  * Do a randomly selected number of extensions of an existing RCU read-side
1233  * critical section.
1234  */
1235 static struct rt_read_seg *
1236 rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
1237                        struct rt_read_seg *rtrsp)
1238 {
1239         int i;
1240         int j;
1241         int mask = rcutorture_extend_mask_max();
1242 
1243         WARN_ON_ONCE(!*readstate); /* -Existing- RCU read-side critsect! */
1244         if (!((mask - 1) & mask))
1245                 return rtrsp;  /* Current RCU reader not extendable. */
1246         /* Bias towards larger numbers of loops. */
1247         i = (torture_random(trsp) >> 3);
1248         i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
1249         for (j = 0; j < i; j++) {
1250                 mask = rcutorture_extend_mask(*readstate, trsp);
1251                 rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
1252         }
1253         return &rtrsp[j];
1254 }
1255 
1256 /*
1257  * Do one read-side critical section, returning false if there was
1258  * no data to read.  Can be invoked both from process context and
1259  * from a timer handler.
1260  */
1261 static bool rcu_torture_one_read(struct torture_random_state *trsp)
1262 {
1263         int i;
1264         unsigned long started;
1265         unsigned long completed;
1266         int newstate;
1267         struct rcu_torture *p;
1268         int pipe_count;
1269         int readstate = 0;
1270         struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS] = { { 0 } };
1271         struct rt_read_seg *rtrsp = &rtseg[0];
1272         struct rt_read_seg *rtrsp1;
1273         unsigned long long ts;
1274 
1275         newstate = rcutorture_extend_mask(readstate, trsp);
1276         rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
1277         started = cur_ops->get_gp_seq();
1278         ts = rcu_trace_clock_local();
1279         p = rcu_dereference_check(rcu_torture_current,
1280                                   rcu_read_lock_bh_held() ||
1281                                   rcu_read_lock_sched_held() ||
1282                                   srcu_read_lock_held(srcu_ctlp) ||
1283                                   torturing_tasks());
1284         if (p == NULL) {
1285                 /* Wait for rcu_torture_writer to get underway */
1286                 rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
1287                 return false;
1288         }
1289         if (p->rtort_mbtest == 0)
1290                 atomic_inc(&n_rcu_torture_mberror);
1291         rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
1292         preempt_disable();
1293         pipe_count = p->rtort_pipe_count;
1294         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
1295                 /* Should not happen, but... */
1296                 pipe_count = RCU_TORTURE_PIPE_LEN;
1297         }
1298         completed = cur_ops->get_gp_seq();
1299         if (pipe_count > 1) {
1300                 do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
1301                                           ts, started, completed);
1302                 rcu_ftrace_dump(DUMP_ALL);
1303         }
1304         __this_cpu_inc(rcu_torture_count[pipe_count]);
1305         completed = rcutorture_seq_diff(completed, started);
1306         if (completed > RCU_TORTURE_PIPE_LEN) {
1307                 /* Should not happen, but... */
1308                 completed = RCU_TORTURE_PIPE_LEN;
1309         }
1310         __this_cpu_inc(rcu_torture_batch[completed]);
1311         preempt_enable();
1312         rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
1313         WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK);
1314 
1315         /* If error or close call, record the sequence of reader protections. */
1316         if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
1317                 i = 0;
1318                 for (rtrsp1 = &rtseg[0]; rtrsp1 < rtrsp; rtrsp1++)
1319                         err_segs[i++] = *rtrsp1;
1320                 rt_read_nsegs = i;
1321         }
1322 
1323         return true;
1324 }
1325 
1326 static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);
1327 
1328 /*
1329  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
1330  * incrementing the corresponding element of the pipeline array.  The
1331  * counter in the element should never be greater than 1, otherwise, the
1332  * RCU implementation is broken.
1333  */
1334 static void rcu_torture_timer(struct timer_list *unused)
1335 {
1336         atomic_long_inc(&n_rcu_torture_timers);
1337         (void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand));
1338 
1339         /* Test call_rcu() invocation from interrupt handler. */
1340         if (cur_ops->call) {
1341                 struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_NOWAIT);
1342 
1343                 if (rhp)
1344                         cur_ops->call(rhp, rcu_torture_timer_cb);
1345         }
1346 }
1347 
1348 /*
1349  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
1350  * incrementing the corresponding element of the pipeline array.  The
1351  * counter in the element should never be greater than 1, otherwise, the
1352  * RCU implementation is broken.
1353  */
1354 static int
1355 rcu_torture_reader(void *arg)
1356 {
1357         unsigned long lastsleep = jiffies;
1358         long myid = (long)arg;
1359         int mynumonline = myid;
1360         DEFINE_TORTURE_RANDOM(rand);
1361         struct timer_list t;
1362 
1363         VERBOSE_TOROUT_STRING("rcu_torture_reader task started");
1364         set_user_nice(current, MAX_NICE);
1365         if (irqreader && cur_ops->irq_capable)
1366                 timer_setup_on_stack(&t, rcu_torture_timer, 0);
1367         tick_dep_set_task(current, TICK_DEP_BIT_RCU);
1368         do {
1369                 if (irqreader && cur_ops->irq_capable) {
1370                         if (!timer_pending(&t))
1371                                 mod_timer(&t, jiffies + 1);
1372                 }
1373                 if (!rcu_torture_one_read(&rand) && !torture_must_stop())
1374                         schedule_timeout_interruptible(HZ);
1375                 if (time_after(jiffies, lastsleep) && !torture_must_stop()) {
1376                         schedule_timeout_interruptible(1);
1377                         lastsleep = jiffies + 10;
1378                 }
1379                 while (num_online_cpus() < mynumonline && !torture_must_stop())
1380                         schedule_timeout_interruptible(HZ / 5);
1381                 stutter_wait("rcu_torture_reader");
1382         } while (!torture_must_stop());
1383         if (irqreader && cur_ops->irq_capable) {
1384                 del_timer_sync(&t);
1385                 destroy_timer_on_stack(&t);
1386         }
1387         tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
1388         torture_kthread_stopping("rcu_torture_reader");
1389         return 0;
1390 }
1391 
1392 /*
1393  * Print torture statistics.  Caller must ensure that there is only
1394  * one call to this function at a given time!!!  This is normally
1395  * accomplished by relying on the module system to only have one copy
1396  * of the module loaded, and then by giving the rcu_torture_stats
1397  * kthread full control (or the init/cleanup functions when rcu_torture_stats
1398  * thread is not running).
1399  */
1400 static void
1401 rcu_torture_stats_print(void)
1402 {
1403         int cpu;
1404         int i;
1405         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1406         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1407         static unsigned long rtcv_snap = ULONG_MAX;
1408         static bool splatted;
1409         struct task_struct *wtp;
1410 
1411         for_each_possible_cpu(cpu) {
1412                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1413                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
1414                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
1415                 }
1416         }
1417         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
1418                 if (pipesummary[i] != 0)
1419                         break;
1420         }
1421 
1422         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1423         pr_cont("rtc: %p %s: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
1424                 rcu_torture_current,
1425                 rcu_torture_current ? "ver" : "VER",
1426                 rcu_torture_current_version,
1427                 list_empty(&rcu_torture_freelist),
1428                 atomic_read(&n_rcu_torture_alloc),
1429                 atomic_read(&n_rcu_torture_alloc_fail),
1430                 atomic_read(&n_rcu_torture_free));
1431         pr_cont("rtmbe: %d rtbe: %ld rtbke: %ld rtbre: %ld ",
1432                 atomic_read(&n_rcu_torture_mberror),
1433                 n_rcu_torture_barrier_error,
1434                 n_rcu_torture_boost_ktrerror,
1435                 n_rcu_torture_boost_rterror);
1436         pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
1437                 n_rcu_torture_boost_failure,
1438                 n_rcu_torture_boosts,
1439                 atomic_long_read(&n_rcu_torture_timers));
1440         torture_onoff_stats();
1441         pr_cont("barrier: %ld/%ld:%ld\n",
1442                 n_barrier_successes,
1443                 n_barrier_attempts,
1444                 n_rcu_torture_barrier_error);
1445 
1446         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1447         if (atomic_read(&n_rcu_torture_mberror) ||
1448             n_rcu_torture_barrier_error || n_rcu_torture_boost_ktrerror ||
1449             n_rcu_torture_boost_rterror || n_rcu_torture_boost_failure ||
1450             i > 1) {
1451                 pr_cont("%s", "!!! ");
1452                 atomic_inc(&n_rcu_torture_error);
1453                 WARN_ON_ONCE(atomic_read(&n_rcu_torture_mberror));
1454                 WARN_ON_ONCE(n_rcu_torture_barrier_error);  // rcu_barrier()
1455                 WARN_ON_ONCE(n_rcu_torture_boost_ktrerror); // no boost kthread
1456                 WARN_ON_ONCE(n_rcu_torture_boost_rterror); // can't set RT prio
1457                 WARN_ON_ONCE(n_rcu_torture_boost_failure); // RCU boost failed
1458                 WARN_ON_ONCE(i > 1); // Too-short grace period
1459         }
1460         pr_cont("Reader Pipe: ");
1461         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1462                 pr_cont(" %ld", pipesummary[i]);
1463         pr_cont("\n");
1464 
1465         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1466         pr_cont("Reader Batch: ");
1467         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1468                 pr_cont(" %ld", batchsummary[i]);
1469         pr_cont("\n");
1470 
1471         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1472         pr_cont("Free-Block Circulation: ");
1473         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1474                 pr_cont(" %d", atomic_read(&rcu_torture_wcount[i]));
1475         }
1476         pr_cont("\n");
1477 
1478         if (cur_ops->stats)
1479                 cur_ops->stats();
1480         if (rtcv_snap == rcu_torture_current_version &&
1481             rcu_torture_current != NULL) {
1482                 int __maybe_unused flags = 0;
1483                 unsigned long __maybe_unused gp_seq = 0;
1484 
1485                 rcutorture_get_gp_data(cur_ops->ttype,
1486                                        &flags, &gp_seq);
1487                 srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
1488                                         &flags, &gp_seq);
1489                 wtp = READ_ONCE(writer_task);
1490                 pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#lx cpu %d\n",
1491                          rcu_torture_writer_state_getname(),
1492                          rcu_torture_writer_state, gp_seq, flags,
1493                          wtp == NULL ? ~0UL : wtp->state,
1494                          wtp == NULL ? -1 : (int)task_cpu(wtp));
1495                 if (!splatted && wtp) {
1496                         sched_show_task(wtp);
1497                         splatted = true;
1498                 }
1499                 show_rcu_gp_kthreads();
1500                 rcu_ftrace_dump(DUMP_ALL);
1501         }
1502         rtcv_snap = rcu_torture_current_version;
1503 }
1504 
1505 /*
1506  * Periodically prints torture statistics, if periodic statistics printing
1507  * was specified via the stat_interval module parameter.
1508  */
1509 static int
1510 rcu_torture_stats(void *arg)
1511 {
1512         VERBOSE_TOROUT_STRING("rcu_torture_stats task started");
1513         do {
1514                 schedule_timeout_interruptible(stat_interval * HZ);
1515                 rcu_torture_stats_print();
1516                 torture_shutdown_absorb("rcu_torture_stats");
1517         } while (!torture_must_stop());
1518         torture_kthread_stopping("rcu_torture_stats");
1519         return 0;
1520 }
1521 
1522 static void
1523 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
1524 {
1525         pr_alert("%s" TORTURE_FLAG
1526                  "--- %s: nreaders=%d nfakewriters=%d "
1527                  "stat_interval=%d verbose=%d test_no_idle_hz=%d "
1528                  "shuffle_interval=%d stutter=%d irqreader=%d "
1529                  "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
1530                  "test_boost=%d/%d test_boost_interval=%d "
1531                  "test_boost_duration=%d shutdown_secs=%d "
1532                  "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
1533                  "n_barrier_cbs=%d "
1534                  "onoff_interval=%d onoff_holdoff=%d\n",
1535                  torture_type, tag, nrealreaders, nfakewriters,
1536                  stat_interval, verbose, test_no_idle_hz, shuffle_interval,
1537                  stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
1538                  test_boost, cur_ops->can_boost,
1539                  test_boost_interval, test_boost_duration, shutdown_secs,
1540                  stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
1541                  n_barrier_cbs,
1542                  onoff_interval, onoff_holdoff);
1543 }
1544 
1545 static int rcutorture_booster_cleanup(unsigned int cpu)
1546 {
1547         struct task_struct *t;
1548 
1549         if (boost_tasks[cpu] == NULL)
1550                 return 0;
1551         mutex_lock(&boost_mutex);
1552         t = boost_tasks[cpu];
1553         boost_tasks[cpu] = NULL;
1554         rcu_torture_enable_rt_throttle();
1555         mutex_unlock(&boost_mutex);
1556 
1557         /* This must be outside of the mutex, otherwise deadlock! */
1558         torture_stop_kthread(rcu_torture_boost, t);
1559         return 0;
1560 }
1561 
1562 static int rcutorture_booster_init(unsigned int cpu)
1563 {
1564         int retval;
1565 
1566         if (boost_tasks[cpu] != NULL)
1567                 return 0;  /* Already created, nothing more to do. */
1568 
1569         /* Don't allow time recalculation while creating a new task. */
1570         mutex_lock(&boost_mutex);
1571         rcu_torture_disable_rt_throttle();
1572         VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
1573         boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL,
1574                                                   cpu_to_node(cpu),
1575                                                   "rcu_torture_boost");
1576         if (IS_ERR(boost_tasks[cpu])) {
1577                 retval = PTR_ERR(boost_tasks[cpu]);
1578                 VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed");
1579                 n_rcu_torture_boost_ktrerror++;
1580                 boost_tasks[cpu] = NULL;
1581                 mutex_unlock(&boost_mutex);
1582                 return retval;
1583         }
1584         kthread_bind(boost_tasks[cpu], cpu);
1585         wake_up_process(boost_tasks[cpu]);
1586         mutex_unlock(&boost_mutex);
1587         return 0;
1588 }
1589 
1590 /*
1591  * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then
1592  * induces a CPU stall for the time specified by stall_cpu.
1593  */
1594 static int rcu_torture_stall(void *args)
1595 {
1596         unsigned long stop_at;
1597 
1598         VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
1599         if (stall_cpu_holdoff > 0) {
1600                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
1601                 schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
1602                 VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
1603         }
1604         if (!kthread_should_stop()) {
1605                 stop_at = ktime_get_seconds() + stall_cpu;
1606                 /* RCU CPU stall is expected behavior in following code. */
1607                 rcu_read_lock();
1608                 if (stall_cpu_irqsoff)
1609                         local_irq_disable();
1610                 else
1611                         preempt_disable();
1612                 pr_alert("rcu_torture_stall start on CPU %d.\n",
1613                          smp_processor_id());
1614                 while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
1615                                     stop_at))
1616                         continue;  /* Induce RCU CPU stall warning. */
1617                 if (stall_cpu_irqsoff)
1618                         local_irq_enable();
1619                 else
1620                         preempt_enable();
1621                 rcu_read_unlock();
1622                 pr_alert("rcu_torture_stall end.\n");
1623         }
1624         torture_shutdown_absorb("rcu_torture_stall");
1625         while (!kthread_should_stop())
1626                 schedule_timeout_interruptible(10 * HZ);
1627         return 0;
1628 }
1629 
1630 /* Spawn CPU-stall kthread, if stall_cpu specified. */
1631 static int __init rcu_torture_stall_init(void)
1632 {
1633         if (stall_cpu <= 0)
1634                 return 0;
1635         return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
1636 }
1637 
1638 /* State structure for forward-progress self-propagating RCU callback. */
1639 struct fwd_cb_state {
1640         struct rcu_head rh;
1641         int stop;
1642 };
1643 
1644 /*
1645  * Forward-progress self-propagating RCU callback function.  Because
1646  * callbacks run from softirq, this function is an implicit RCU read-side
1647  * critical section.
1648  */
1649 static void rcu_torture_fwd_prog_cb(struct rcu_head *rhp)
1650 {
1651         struct fwd_cb_state *fcsp = container_of(rhp, struct fwd_cb_state, rh);
1652 
1653         if (READ_ONCE(fcsp->stop)) {
1654                 WRITE_ONCE(fcsp->stop, 2);
1655                 return;
1656         }
1657         cur_ops->call(&fcsp->rh, rcu_torture_fwd_prog_cb);
1658 }
1659 
1660 /* State for continuous-flood RCU callbacks. */
1661 struct rcu_fwd_cb {
1662         struct rcu_head rh;
1663         struct rcu_fwd_cb *rfc_next;
1664         struct rcu_fwd *rfc_rfp;
1665         int rfc_gps;
1666 };
1667 
1668 #define MAX_FWD_CB_JIFFIES      (8 * HZ) /* Maximum CB test duration. */
1669 #define MIN_FWD_CB_LAUNDERS     3       /* This many CB invocations to count. */
1670 #define MIN_FWD_CBS_LAUNDERED   100     /* Number of counted CBs. */
1671 #define FWD_CBS_HIST_DIV        10      /* Histogram buckets/second. */
1672 #define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))
1673 
1674 struct rcu_launder_hist {
1675         long n_launders;
1676         unsigned long launder_gp_seq;
1677 };
1678 
1679 struct rcu_fwd {
1680         spinlock_t rcu_fwd_lock;
1681         struct rcu_fwd_cb *rcu_fwd_cb_head;
1682         struct rcu_fwd_cb **rcu_fwd_cb_tail;
1683         long n_launders_cb;
1684         unsigned long rcu_fwd_startat;
1685         struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
1686         unsigned long rcu_launder_gp_seq_start;
1687 };
1688 
1689 struct rcu_fwd *rcu_fwds;
1690 bool rcu_fwd_emergency_stop;
1691 
1692 static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
1693 {
1694         unsigned long gps;
1695         unsigned long gps_old;
1696         int i;
1697         int j;
1698 
1699         for (i = ARRAY_SIZE(rfp->n_launders_hist) - 1; i > 0; i--)
1700                 if (rfp->n_launders_hist[i].n_launders > 0)
1701                         break;
1702         pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):",
1703                  __func__, jiffies - rfp->rcu_fwd_startat);
1704         gps_old = rfp->rcu_launder_gp_seq_start;
1705         for (j = 0; j <= i; j++) {
1706                 gps = rfp->n_launders_hist[j].launder_gp_seq;
1707                 pr_cont(" %ds/%d: %ld:%ld",
1708                         j + 1, FWD_CBS_HIST_DIV,
1709                         rfp->n_launders_hist[j].n_launders,
1710                         rcutorture_seq_diff(gps, gps_old));
1711                 gps_old = gps;
1712         }
1713         pr_cont("\n");
1714 }
1715 
1716 /* Callback function for continuous-flood RCU callbacks. */
1717 static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
1718 {
1719         unsigned long flags;
1720         int i;
1721         struct rcu_fwd_cb *rfcp = container_of(rhp, struct rcu_fwd_cb, rh);
1722         struct rcu_fwd_cb **rfcpp;
1723         struct rcu_fwd *rfp = rfcp->rfc_rfp;
1724 
1725         rfcp->rfc_next = NULL;
1726         rfcp->rfc_gps++;
1727         spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
1728         rfcpp = rfp->rcu_fwd_cb_tail;
1729         rfp->rcu_fwd_cb_tail = &rfcp->rfc_next;
1730         WRITE_ONCE(*rfcpp, rfcp);
1731         WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1);
1732         i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
1733         if (i >= ARRAY_SIZE(rfp->n_launders_hist))
1734                 i = ARRAY_SIZE(rfp->n_launders_hist) - 1;
1735         rfp->n_launders_hist[i].n_launders++;
1736         rfp->n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();
1737         spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
1738 }
1739 
1740 // Give the scheduler a chance, even on nohz_full CPUs.
1741 static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)
1742 {
1743         if (IS_ENABLED(CONFIG_PREEMPTION) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
1744                 // Real call_rcu() floods hit userspace, so emulate that.
1745                 if (need_resched() || (iter & 0xfff))
1746                         schedule();
1747                 return;
1748         }
1749         // No userspace emulation: CB invocation throttles call_rcu()
1750         cond_resched();
1751 }
1752 
1753 /*
1754  * Free all callbacks on the rcu_fwd_cb_head list, either because the
1755  * test is over or because we hit an OOM event.
1756  */
1757 static unsigned long rcu_torture_fwd_prog_cbfree(struct rcu_fwd *rfp)
1758 {
1759         unsigned long flags;
1760         unsigned long freed = 0;
1761         struct rcu_fwd_cb *rfcp;
1762 
1763         for (;;) {
1764                 spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
1765                 rfcp = rfp->rcu_fwd_cb_head;
1766                 if (!rfcp) {
1767                         spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
1768                         break;
1769                 }
1770                 rfp->rcu_fwd_cb_head = rfcp->rfc_next;
1771                 if (!rfp->rcu_fwd_cb_head)
1772                         rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
1773                 spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
1774                 kfree(rfcp);
1775                 freed++;
1776                 rcu_torture_fwd_prog_cond_resched(freed);
1777                 if (tick_nohz_full_enabled()) {
1778                         local_irq_save(flags);
1779                         rcu_momentary_dyntick_idle();
1780                         local_irq_restore(flags);
1781                 }
1782         }
1783         return freed;
1784 }
1785 
1786 /* Carry out need_resched()/cond_resched() forward-progress testing. */
1787 static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
1788                                     int *tested, int *tested_tries)
1789 {
1790         unsigned long cver;
1791         unsigned long dur;
1792         struct fwd_cb_state fcs;
1793         unsigned long gps;
1794         int idx;
1795         int sd;
1796         int sd4;
1797         bool selfpropcb = false;
1798         unsigned long stopat;
1799         static DEFINE_TORTURE_RANDOM(trs);
1800 
1801         if  (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) {
1802                 init_rcu_head_on_stack(&fcs.rh);
1803                 selfpropcb = true;
1804         }
1805 
1806         /* Tight loop containing cond_resched(). */
1807         WRITE_ONCE(rcu_fwd_cb_nodelay, true);
1808         cur_ops->sync(); /* Later readers see above write. */
1809         if  (selfpropcb) {
1810                 WRITE_ONCE(fcs.stop, 0);
1811                 cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
1812         }
1813         cver = READ_ONCE(rcu_torture_current_version);
1814         gps = cur_ops->get_gp_seq();
1815         sd = cur_ops->stall_dur() + 1;
1816         sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
1817         dur = sd4 + torture_random(&trs) % (sd - sd4);
1818         WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
1819         stopat = rfp->rcu_fwd_startat + dur;
1820         while (time_before(jiffies, stopat) &&
1821                !shutdown_time_arrived() &&
1822                !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
1823                 idx = cur_ops->readlock();
1824                 udelay(10);
1825                 cur_ops->readunlock(idx);
1826                 if (!fwd_progress_need_resched || need_resched())
1827                         cond_resched();
1828         }
1829         (*tested_tries)++;
1830         if (!time_before(jiffies, stopat) &&
1831             !shutdown_time_arrived() &&
1832             !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
1833                 (*tested)++;
1834                 cver = READ_ONCE(rcu_torture_current_version) - cver;
1835                 gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
1836                 WARN_ON(!cver && gps < 2);
1837                 pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps);
1838         }
1839         if (selfpropcb) {
1840                 WRITE_ONCE(fcs.stop, 1);
1841                 cur_ops->sync(); /* Wait for running CB to complete. */
1842                 cur_ops->cb_barrier(); /* Wait for queued callbacks. */
1843         }
1844 
1845         if (selfpropcb) {
1846                 WARN_ON(READ_ONCE(fcs.stop) != 2);
1847                 destroy_rcu_head_on_stack(&fcs.rh);
1848         }
1849         schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
1850         WRITE_ONCE(rcu_fwd_cb_nodelay, false);
1851 }
1852 
1853 /* Carry out call_rcu() forward-progress testing. */
1854 static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
1855 {
1856         unsigned long cver;
1857         unsigned long flags;
1858         unsigned long gps;
1859         int i;
1860         long n_launders;
1861         long n_launders_cb_snap;
1862         long n_launders_sa;
1863         long n_max_cbs;
1864         long n_max_gps;
1865         struct rcu_fwd_cb *rfcp;
1866         struct rcu_fwd_cb *rfcpn;
1867         unsigned long stopat;
1868         unsigned long stoppedat;
1869 
1870         if (READ_ONCE(rcu_fwd_emergency_stop))
1871                 return; /* Get out of the way quickly, no GP wait! */
1872         if (!cur_ops->call)
1873                 return; /* Can't do call_rcu() fwd prog without ->call. */
1874 
1875         /* Loop continuously posting RCU callbacks. */
1876         WRITE_ONCE(rcu_fwd_cb_nodelay, true);
1877         cur_ops->sync(); /* Later readers see above write. */
1878         WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
1879         stopat = rfp->rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
1880         n_launders = 0;
1881         rfp->n_launders_cb = 0; // Hoist initialization for multi-kthread
1882         n_launders_sa = 0;
1883         n_max_cbs = 0;
1884         n_max_gps = 0;
1885         for (i = 0; i < ARRAY_SIZE(rfp->n_launders_hist); i++)
1886                 rfp->n_launders_hist[i].n_launders = 0;
1887         cver = READ_ONCE(rcu_torture_current_version);
1888         gps = cur_ops->get_gp_seq();
1889         rfp->rcu_launder_gp_seq_start = gps;
1890         tick_dep_set_task(current, TICK_DEP_BIT_RCU);
1891         while (time_before(jiffies, stopat) &&
1892                !shutdown_time_arrived() &&
1893                !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
1894                 rfcp = READ_ONCE(rfp->rcu_fwd_cb_head);
1895                 rfcpn = NULL;
1896                 if (rfcp)
1897                         rfcpn = READ_ONCE(rfcp->rfc_next);
1898                 if (rfcpn) {
1899                         if (rfcp->rfc_gps >= MIN_FWD_CB_LAUNDERS &&
1900                             ++n_max_gps >= MIN_FWD_CBS_LAUNDERED)
1901                                 break;
1902                         rfp->rcu_fwd_cb_head = rfcpn;
1903                         n_launders++;
1904                         n_launders_sa++;
1905                 } else {
1906                         rfcp = kmalloc(sizeof(*rfcp), GFP_KERNEL);
1907                         if (WARN_ON_ONCE(!rfcp)) {
1908                                 schedule_timeout_interruptible(1);
1909                                 continue;
1910                         }
1911                         n_max_cbs++;
1912                         n_launders_sa = 0;
1913                         rfcp->rfc_gps = 0;
1914                         rfcp->rfc_rfp = rfp;
1915                 }
1916                 cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
1917                 rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
1918                 if (tick_nohz_full_enabled()) {
1919                         local_irq_save(flags);
1920                         rcu_momentary_dyntick_idle();
1921                         local_irq_restore(flags);
1922                 }
1923         }
1924         stoppedat = jiffies;
1925         n_launders_cb_snap = READ_ONCE(rfp->n_launders_cb);
1926         cver = READ_ONCE(rcu_torture_current_version) - cver;
1927         gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
1928         cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
1929         (void)rcu_torture_fwd_prog_cbfree(rfp);
1930 
1931         if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop) &&
1932             !shutdown_time_arrived()) {
1933                 WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
1934                 pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n",
1935                          __func__,
1936                          stoppedat - rfp->rcu_fwd_startat, jiffies - stoppedat,
1937                          n_launders + n_max_cbs - n_launders_cb_snap,
1938                          n_launders, n_launders_sa,
1939                          n_max_gps, n_max_cbs, cver, gps);
1940                 rcu_torture_fwd_cb_hist(rfp);
1941         }
1942         schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
1943         tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
1944         WRITE_ONCE(rcu_fwd_cb_nodelay, false);
1945 }
1946 
1947 
1948 /*
1949  * OOM notifier, but this only prints diagnostic information for the
1950  * current forward-progress test.
1951  */
1952 static int rcutorture_oom_notify(struct notifier_block *self,
1953                                  unsigned long notused, void *nfreed)
1954 {
1955         struct rcu_fwd *rfp = rcu_fwds;
1956 
1957         WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
1958              __func__);
1959         rcu_torture_fwd_cb_hist(rfp);
1960         rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rfp->rcu_fwd_startat)) / 2);
1961         WRITE_ONCE(rcu_fwd_emergency_stop, true);
1962         smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
1963         pr_info("%s: Freed %lu RCU callbacks.\n",
1964                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
1965         rcu_barrier();
1966         pr_info("%s: Freed %lu RCU callbacks.\n",
1967                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
1968         rcu_barrier();
1969         pr_info("%s: Freed %lu RCU callbacks.\n",
1970                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
1971         smp_mb(); /* Frees before return to avoid redoing OOM. */
1972         (*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */
1973         pr_info("%s returning after OOM processing.\n", __func__);
1974         return NOTIFY_OK;
1975 }
1976 
1977 static struct notifier_block rcutorture_oom_nb = {
1978         .notifier_call = rcutorture_oom_notify
1979 };
1980 
1981 /* Carry out grace-period forward-progress testing. */
1982 static int rcu_torture_fwd_prog(void *args)
1983 {
1984         struct rcu_fwd *rfp = args;
1985         int tested = 0;
1986         int tested_tries = 0;
1987 
1988         VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
1989         rcu_bind_current_to_nocb();
1990         if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST))
1991                 set_user_nice(current, MAX_NICE);
1992         do {
1993                 schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
1994                 WRITE_ONCE(rcu_fwd_emergency_stop, false);
1995                 register_oom_notifier(&rcutorture_oom_nb);
1996                 rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
1997                 rcu_torture_fwd_prog_cr(rfp);
1998                 unregister_oom_notifier(&rcutorture_oom_nb);
1999 
2000                 /* Avoid slow periods, better to test when busy. */
2001                 stutter_wait("rcu_torture_fwd_prog");
2002         } while (!torture_must_stop());
2003         /* Short runs might not contain a valid forward-progress attempt. */
2004         WARN_ON(!tested && tested_tries >= 5);
2005         pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
2006         torture_kthread_stopping("rcu_torture_fwd_prog");
2007         return 0;
2008 }
2009 
2010 /* If forward-progress checking is requested and feasible, spawn the thread. */
2011 static int __init rcu_torture_fwd_prog_init(void)
2012 {
2013         struct rcu_fwd *rfp;
2014 
2015         if (!fwd_progress)
2016                 return 0; /* Not requested, so don't do it. */
2017         if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0 ||
2018             cur_ops == &rcu_busted_ops) {
2019                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
2020                 return 0;
2021         }
2022         if (stall_cpu > 0) {
2023                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
2024                 if (IS_MODULE(CONFIG_RCU_TORTURE_TESTS))
2025                         return -EINVAL; /* In module, can fail back to user. */
2026                 WARN_ON(1); /* Make sure rcutorture notices conflict. */
2027                 return 0;
2028         }
2029         if (fwd_progress_holdoff <= 0)
2030                 fwd_progress_holdoff = 1;
2031         if (fwd_progress_div <= 0)
2032                 fwd_progress_div = 4;
2033         rfp = kzalloc(sizeof(*rfp), GFP_KERNEL);
2034         if (!rfp)
2035                 return -ENOMEM;
2036         spin_lock_init(&rfp->rcu_fwd_lock);
2037         rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
2038         return torture_create_kthread(rcu_torture_fwd_prog, rfp, fwd_prog_task);
2039 }
2040 
2041 /* Callback function for RCU barrier testing. */
2042 static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
2043 {
2044         atomic_inc(&barrier_cbs_invoked);
2045 }
2046 
2047 /* kthread function to register callbacks used to test RCU barriers. */
2048 static int rcu_torture_barrier_cbs(void *arg)
2049 {
2050         long myid = (long)arg;
2051         bool lastphase = 0;
2052         bool newphase;
2053         struct rcu_head rcu;
2054 
2055         init_rcu_head_on_stack(&rcu);
2056         VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started");
2057         set_user_nice(current, MAX_NICE);
2058         do {
2059                 wait_event(barrier_cbs_wq[myid],
2060                            (newphase =
2061                             smp_load_acquire(&barrier_phase)) != lastphase ||
2062                            torture_must_stop());
2063                 lastphase = newphase;
2064                 if (torture_must_stop())
2065                         break;
2066                 /*
2067                  * The above smp_load_acquire() ensures barrier_phase load
2068                  * is ordered before the following ->call().
2069                  */
2070                 local_irq_disable(); /* Just to test no-irq call_rcu(). */
2071                 cur_ops->call(&rcu, rcu_torture_barrier_cbf);
2072                 local_irq_enable();
2073                 if (atomic_dec_and_test(&barrier_cbs_count))
2074                         wake_up(&barrier_wq);
2075         } while (!torture_must_stop());
2076         if (cur_ops->cb_barrier != NULL)
2077                 cur_ops->cb_barrier();
2078         destroy_rcu_head_on_stack(&rcu);
2079         torture_kthread_stopping("rcu_torture_barrier_cbs");
2080         return 0;
2081 }
2082 
2083 /* kthread function to drive and coordinate RCU barrier testing. */
2084 static int rcu_torture_barrier(void *arg)
2085 {
2086         int i;
2087 
2088         VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting");
2089         do {
2090                 atomic_set(&barrier_cbs_invoked, 0);
2091                 atomic_set(&barrier_cbs_count, n_barrier_cbs);
2092                 /* Ensure barrier_phase ordered after prior assignments. */
2093                 smp_store_release(&barrier_phase, !barrier_phase);
2094                 for (i = 0; i < n_barrier_cbs; i++)
2095                         wake_up(&barrier_cbs_wq[i]);
2096                 wait_event(barrier_wq,
2097                            atomic_read(&barrier_cbs_count) == 0 ||
2098                            torture_must_stop());
2099                 if (torture_must_stop())
2100                         break;
2101                 n_barrier_attempts++;
2102                 cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
2103                 if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
2104                         n_rcu_torture_barrier_error++;
2105                         pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
2106                                atomic_read(&barrier_cbs_invoked),
2107                                n_barrier_cbs);
2108                         WARN_ON_ONCE(1);
2109                 } else {
2110                         n_barrier_successes++;
2111                 }
2112                 schedule_timeout_interruptible(HZ / 10);
2113         } while (!torture_must_stop());
2114         torture_kthread_stopping("rcu_torture_barrier");
2115         return 0;
2116 }
2117 
2118 /* Initialize RCU barrier testing. */
2119 static int rcu_torture_barrier_init(void)
2120 {
2121         int i;
2122         int ret;
2123 
2124         if (n_barrier_cbs <= 0)
2125                 return 0;
2126         if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
2127                 pr_alert("%s" TORTURE_FLAG
2128                          " Call or barrier ops missing for %s,\n",
2129                          torture_type, cur_ops->name);
2130                 pr_alert("%s" TORTURE_FLAG
2131                          " RCU barrier testing omitted from run.\n",
2132                          torture_type);
2133                 return 0;
2134         }
2135         atomic_set(&barrier_cbs_count, 0);
2136         atomic_set(&barrier_cbs_invoked, 0);
2137         barrier_cbs_tasks =
2138                 kcalloc(n_barrier_cbs, sizeof(barrier_cbs_tasks[0]),
2139                         GFP_KERNEL);
2140         barrier_cbs_wq =
2141                 kcalloc(n_barrier_cbs, sizeof(barrier_cbs_wq[0]), GFP_KERNEL);
2142         if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
2143                 return -ENOMEM;
2144         for (i = 0; i < n_barrier_cbs; i++) {
2145                 init_waitqueue_head(&barrier_cbs_wq[i]);
2146                 ret = torture_create_kthread(rcu_torture_barrier_cbs,
2147                                              (void *)(long)i,
2148                                              barrier_cbs_tasks[i]);
2149                 if (ret)
2150                         return ret;
2151         }
2152         return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task);
2153 }
2154 
2155 /* Clean up after RCU barrier testing. */
2156 static void rcu_torture_barrier_cleanup(void)
2157 {
2158         int i;
2159 
2160         torture_stop_kthread(rcu_torture_barrier, barrier_task);
2161         if (barrier_cbs_tasks != NULL) {
2162                 for (i = 0; i < n_barrier_cbs; i++)
2163                         torture_stop_kthread(rcu_torture_barrier_cbs,
2164                                              barrier_cbs_tasks[i]);
2165                 kfree(barrier_cbs_tasks);
2166                 barrier_cbs_tasks = NULL;
2167         }
2168         if (barrier_cbs_wq != NULL) {
2169                 kfree(barrier_cbs_wq);
2170                 barrier_cbs_wq = NULL;
2171         }
2172 }
2173 
2174 static bool rcu_torture_can_boost(void)
2175 {
2176         static int boost_warn_once;
2177         int prio;
2178 
2179         if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2)
2180                 return false;
2181 
2182         prio = rcu_get_gp_kthreads_prio();
2183         if (!prio)
2184                 return false;
2185 
2186         if (prio < 2) {
2187                 if (boost_warn_once  == 1)
2188                         return false;
2189 
2190                 pr_alert("%s: WARN: RCU kthread priority too low to test boosting.  Skipping RCU boost test. Try passing rcutree.kthread_prio > 1 on the kernel command line.\n", KBUILD_MODNAME);
2191                 boost_warn_once = 1;
2192                 return false;
2193         }
2194 
2195         return true;
2196 }
2197 
2198 static enum cpuhp_state rcutor_hp;
2199 
2200 static void
2201 rcu_torture_cleanup(void)
2202 {
2203         int firsttime;
2204         int flags = 0;
2205         unsigned long gp_seq = 0;
2206         int i;
2207 
2208         if (torture_cleanup_begin()) {
2209                 if (cur_ops->cb_barrier != NULL)
2210                         cur_ops->cb_barrier();
2211                 return;
2212         }
2213         if (!cur_ops) {
2214                 torture_cleanup_end();
2215                 return;
2216         }
2217 
2218         show_rcu_gp_kthreads();
2219         rcu_torture_barrier_cleanup();
2220         torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
2221         torture_stop_kthread(rcu_torture_stall, stall_task);
2222         torture_stop_kthread(rcu_torture_writer, writer_task);
2223 
2224         if (reader_tasks) {
2225                 for (i = 0; i < nrealreaders; i++)
2226                         torture_stop_kthread(rcu_torture_reader,
2227                                              reader_tasks[i]);
2228                 kfree(reader_tasks);
2229         }
2230         rcu_torture_current = NULL;
2231 
2232         if (fakewriter_tasks) {
2233                 for (i = 0; i < nfakewriters; i++) {
2234                         torture_stop_kthread(rcu_torture_fakewriter,
2235                                              fakewriter_tasks[i]);
2236                 }
2237                 kfree(fakewriter_tasks);
2238                 fakewriter_tasks = NULL;
2239         }
2240 
2241         rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
2242         srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
2243         pr_alert("%s:  End-test grace-period state: g%lu f%#x\n",
2244                  cur_ops->name, gp_seq, flags);
2245         torture_stop_kthread(rcu_torture_stats, stats_task);
2246         torture_stop_kthread(rcu_torture_fqs, fqs_task);
2247         if (rcu_torture_can_boost())
2248                 cpuhp_remove_state(rcutor_hp);
2249 
2250         /*
2251          * Wait for all RCU callbacks to fire, then do torture-type-specific
2252          * cleanup operations.
2253          */
2254         if (cur_ops->cb_barrier != NULL)
2255                 cur_ops->cb_barrier();
2256         if (cur_ops->cleanup != NULL)
2257                 cur_ops->cleanup();
2258 
2259         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
2260 
2261         if (err_segs_recorded) {
2262                 pr_alert("Failure/close-call rcutorture reader segments:\n");
2263                 if (rt_read_nsegs == 0)
2264                         pr_alert("\t: No segments recorded!!!\n");
2265                 firsttime = 1;
2266                 for (i = 0; i < rt_read_nsegs; i++) {
2267                         pr_alert("\t%d: %#x ", i, err_segs[i].rt_readstate);
2268                         if (err_segs[i].rt_delay_jiffies != 0) {
2269                                 pr_cont("%s%ldjiffies", firsttime ? "" : "+",
2270                                         err_segs[i].rt_delay_jiffies);
2271                                 firsttime = 0;
2272                         }
2273                         if (err_segs[i].rt_delay_ms != 0) {
2274                                 pr_cont("%s%ldms", firsttime ? "" : "+",
2275                                         err_segs[i].rt_delay_ms);
2276                                 firsttime = 0;
2277                         }
2278                         if (err_segs[i].rt_delay_us != 0) {
2279                                 pr_cont("%s%ldus", firsttime ? "" : "+",
2280                                         err_segs[i].rt_delay_us);
2281                                 firsttime = 0;
2282                         }
2283                         pr_cont("%s\n",
2284                                 err_segs[i].rt_preempted ? "preempted" : "");
2285 
2286                 }
2287         }
2288         if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
2289                 rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
2290         else if (torture_onoff_failures())
2291                 rcu_torture_print_module_parms(cur_ops,
2292                                                "End of test: RCU_HOTPLUG");
2293         else
2294                 rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
2295         torture_cleanup_end();
2296 }
2297 
2298 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
2299 static void rcu_torture_leak_cb(struct rcu_head *rhp)
2300 {
2301 }
2302 
2303 static void rcu_torture_err_cb(struct rcu_head *rhp)
2304 {
2305         /*
2306          * This -might- happen due to race conditions, but is unlikely.
2307          * The scenario that leads to this happening is that the
2308          * first of the pair of duplicate callbacks is queued,
2309          * someone else starts a grace period that includes that
2310          * callback, then the second of the pair must wait for the
2311          * next grace period.  Unlikely, but can happen.  If it
2312          * does happen, the debug-objects subsystem won't have splatted.
2313          */
2314         pr_alert("%s: duplicated callback was invoked.\n", KBUILD_MODNAME);
2315 }
2316 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2317 
2318 /*
2319  * Verify that double-free causes debug-objects to complain, but only
2320  * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.  Otherwise, say that the test
2321  * cannot be carried out.
2322  */
2323 static void rcu_test_debug_objects(void)
2324 {
2325 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
2326         struct rcu_head rh1;
2327         struct rcu_head rh2;
2328 
2329         init_rcu_head_on_stack(&rh1);
2330         init_rcu_head_on_stack(&rh2);
2331         pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME);
2332 
2333         /* Try to queue the rh2 pair of callbacks for the same grace period. */
2334         preempt_disable(); /* Prevent preemption from interrupting test. */
2335         rcu_read_lock(); /* Make it impossible to finish a grace period. */
2336         call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */
2337         local_irq_disable(); /* Make it harder to start a new grace period. */
2338         call_rcu(&rh2, rcu_torture_leak_cb);
2339         call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
2340         local_irq_enable();
2341         rcu_read_unlock();
2342         preempt_enable();
2343 
2344         /* Wait for them all to get done so we can safely return. */
2345         rcu_barrier();
2346         pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
2347         destroy_rcu_head_on_stack(&rh1);
2348         destroy_rcu_head_on_stack(&rh2);
2349 #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2350         pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
2351 #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2352 }
2353 
2354 static void rcutorture_sync(void)
2355 {
2356         static unsigned long n;
2357 
2358         if (cur_ops->sync && !(++n & 0xfff))
2359                 cur_ops->sync();
2360 }
2361 
2362 static int __init
2363 rcu_torture_init(void)
2364 {
2365         long i;
2366         int cpu;
2367         int firsterr = 0;
2368         static struct rcu_torture_ops *torture_ops[] = {
2369                 &rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
2370                 &busted_srcud_ops, &tasks_ops, &trivial_ops,
2371         };
2372 
2373         if (!torture_init_begin(torture_type, verbose))
2374                 return -EBUSY;
2375 
2376         /* Process args and tell the world that the torturer is on the job. */
2377         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
2378                 cur_ops = torture_ops[i];
2379                 if (strcmp(torture_type, cur_ops->name) == 0)
2380                         break;
2381         }
2382         if (i == ARRAY_SIZE(torture_ops)) {
2383                 pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
2384                          torture_type);
2385                 pr_alert("rcu-torture types:");
2386                 for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
2387                         pr_cont(" %s", torture_ops[i]->name);
2388                 pr_cont("\n");
2389                 WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
2390                 firsterr = -EINVAL;
2391                 cur_ops = NULL;
2392                 goto unwind;
2393         }
2394         if (cur_ops->fqs == NULL && fqs_duration != 0) {
2395                 pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
2396                 fqs_duration = 0;
2397         }
2398         if (cur_ops->init)
2399                 cur_ops->init();
2400 
2401         if (nreaders >= 0) {
2402                 nrealreaders = nreaders;
2403         } else {
2404                 nrealreaders = num_online_cpus() - 2 - nreaders;
2405                 if (nrealreaders <= 0)
2406                         nrealreaders = 1;
2407         }
2408         rcu_torture_print_module_parms(cur_ops, "Start of test");
2409 
2410         /* Set up the freelist. */
2411 
2412         INIT_LIST_HEAD(&rcu_torture_freelist);
2413         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
2414                 rcu_tortures[i].rtort_mbtest = 0;
2415                 list_add_tail(&rcu_tortures[i].rtort_free,
2416                               &rcu_torture_freelist);
2417         }
2418 
2419         /* Initialize the statistics so that each run gets its own numbers. */
2420 
2421         rcu_torture_current = NULL;
2422         rcu_torture_current_version = 0;
2423         atomic_set(&n_rcu_torture_alloc, 0);
2424         atomic_set(&n_rcu_torture_alloc_fail, 0);
2425         atomic_set(&n_rcu_torture_free, 0);
2426         atomic_set(&n_rcu_torture_mberror, 0);
2427         atomic_set(&n_rcu_torture_error, 0);
2428         n_rcu_torture_barrier_error = 0;
2429         n_rcu_torture_boost_ktrerror = 0;
2430         n_rcu_torture_boost_rterror = 0;
2431         n_rcu_torture_boost_failure = 0;
2432         n_rcu_torture_boosts = 0;
2433         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
2434                 atomic_set(&rcu_torture_wcount[i], 0);
2435         for_each_possible_cpu(cpu) {
2436                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
2437                         per_cpu(rcu_torture_count, cpu)[i] = 0;
2438                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
2439                 }
2440         }
2441         err_segs_recorded = 0;
2442         rt_read_nsegs = 0;
2443 
2444         /* Start up the kthreads. */
2445 
2446         firsterr = torture_create_kthread(rcu_torture_writer, NULL,
2447                                           writer_task);
2448         if (firsterr)
2449                 goto unwind;
2450         if (nfakewriters > 0) {
2451                 fakewriter_tasks = kcalloc(nfakewriters,
2452                                            sizeof(fakewriter_tasks[0]),
2453                                            GFP_KERNEL);
2454                 if (fakewriter_tasks == NULL) {
2455                         VERBOSE_TOROUT_ERRSTRING("out of memory");
2456                         firsterr = -ENOMEM;
2457                         goto unwind;
2458                 }
2459         }
2460         for (i = 0; i < nfakewriters; i++) {
2461                 firsterr = torture_create_kthread(rcu_torture_fakewriter,
2462                                                   NULL, fakewriter_tasks[i]);
2463                 if (firsterr)
2464                         goto unwind;
2465         }
2466         reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
2467                                GFP_KERNEL);
2468         if (reader_tasks == NULL) {
2469                 VERBOSE_TOROUT_ERRSTRING("out of memory");
2470                 firsterr = -ENOMEM;
2471                 goto unwind;
2472         }
2473         for (i = 0; i < nrealreaders; i++) {
2474                 firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
2475                                                   reader_tasks[i]);
2476                 if (firsterr)
2477                         goto unwind;
2478         }
2479         if (stat_interval > 0) {
2480                 firsterr = torture_create_kthread(rcu_torture_stats, NULL,
2481                                                   stats_task);
2482                 if (firsterr)
2483                         goto unwind;
2484         }
2485         if (test_no_idle_hz && shuffle_interval > 0) {
2486                 firsterr = torture_shuffle_init(shuffle_interval * HZ);
2487                 if (firsterr)
2488                         goto unwind;
2489         }
2490         if (stutter < 0)
2491                 stutter = 0;
2492         if (stutter) {
2493                 int t;
2494 
2495                 t = cur_ops->stall_dur ? cur_ops->stall_dur() : stutter * HZ;
2496                 firsterr = torture_stutter_init(stutter * HZ, t);
2497                 if (firsterr)
2498                         goto unwind;
2499         }
2500         if (fqs_duration < 0)
2501                 fqs_duration = 0;
2502         if (fqs_duration) {
2503                 /* Create the fqs thread */
2504                 firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
2505                                                   fqs_task);
2506                 if (firsterr)
2507                         goto unwind;
2508         }
2509         if (test_boost_interval < 1)
2510                 test_boost_interval = 1;
2511         if (test_boost_duration < 2)
2512                 test_boost_duration = 2;
2513         if (rcu_torture_can_boost()) {
2514 
2515                 boost_starttime = jiffies + test_boost_interval * HZ;
2516 
2517                 firsterr = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "RCU_TORTURE",
2518                                              rcutorture_booster_init,
2519                                              rcutorture_booster_cleanup);
2520                 if (firsterr < 0)
2521                         goto unwind;
2522                 rcutor_hp = firsterr;
2523         }
2524         shutdown_jiffies = jiffies + shutdown_secs * HZ;
2525         firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
2526         if (firsterr)
2527                 goto unwind;
2528         firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval,
2529                                       rcutorture_sync);
2530         if (firsterr)
2531                 goto unwind;
2532         firsterr = rcu_torture_stall_init();
2533         if (firsterr)
2534                 goto unwind;
2535         firsterr = rcu_torture_fwd_prog_init();
2536         if (firsterr)
2537                 goto unwind;
2538         firsterr = rcu_torture_barrier_init();
2539         if (firsterr)
2540                 goto unwind;
2541         if (object_debug)
2542                 rcu_test_debug_objects();
2543         torture_init_end();
2544         return 0;
2545 
2546 unwind:
2547         torture_init_end();
2548         rcu_torture_cleanup();
2549         return firsterr;
2550 }
2551 
2552 module_init(rcu_torture_init);
2553 module_exit(rcu_torture_cleanup);
2554 

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