kernel/rcu/rcutorture.c

   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.rst
  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_wait.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 #include <linux/rcupdate_trace.h>
  49
  50 #include "rcu.h"
  51
  52 MODULE_LICENSE("GPL");
  53 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
  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, leakpointer, 0, "Leak pointer dereferences from readers");
  91 torture_param(int, n_barrier_cbs, 0,
  92              "# of callbacks/kthreads for barrier testing");
  93 torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
  94 torture_param(int, nreaders, -1, "Number of RCU reader threads");
  95 torture_param(int, object_debug, 0,
  96              "Enable debug-object double call_rcu() testing");
  97 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
  98 torture_param(int, onoff_interval, 0,
  99              "Time between CPU hotplugs (jiffies), 0=disable");
 100 torture_param(int, read_exit_delay, 13,
 101               "Delay between read-then-exit episodes (s)");
 102 torture_param(int, read_exit_burst, 16,
 103               "# of read-then-exit bursts per episode, zero to disable");
 104 torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
 105 torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
 106 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
 107 torture_param(int, stall_cpu_holdoff, 10,
 108              "Time to wait before starting stall (s).");
 109 torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
 110 torture_param(int, stall_cpu_block, 0, "Sleep while stalling.");
 111 torture_param(int, stall_gp_kthread, 0,
 112               "Grace-period kthread stall duration (s).");
 113 torture_param(int, stat_interval, 60,
 114              "Number of seconds between stats printk()s");
 115 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
 116 torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
 117 torture_param(int, test_boost_duration, 4,
 118              "Duration of each boost test, seconds.");
 119 torture_param(int, test_boost_interval, 7,
 120              "Interval between boost tests, seconds.");
 121 torture_param(bool, test_no_idle_hz, true,
 122              "Test support for tickless idle CPUs");
 123 torture_param(int, verbose, 1,
 124              "Enable verbose debugging printk()s");
 125
 126 static char *torture_type = "rcu";
 127 module_param(torture_type, charp, 0444);
 128 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");
 129
 130 static int nrealreaders;
 131 static struct task_struct *writer_task;
 132 static struct task_struct **fakewriter_tasks;
 133 static struct task_struct **reader_tasks;
 134 static struct task_struct *stats_task;
 135 static struct task_struct *fqs_task;
 136 static struct task_struct *boost_tasks[NR_CPUS];
 137 static struct task_struct *stall_task;
 138 static struct task_struct *fwd_prog_task;
 139 static struct task_struct **barrier_cbs_tasks;
 140 static struct task_struct *barrier_task;
 141 static struct task_struct *read_exit_task;
 142
 143 #define RCU_TORTURE_PIPE_LEN 10
 144
 145 struct rcu_torture {
 146         struct rcu_head rtort_rcu;
 147         int rtort_pipe_count;
 148         struct list_head rtort_free;
 149         int rtort_mbtest;
 150 };
 151
 152 static LIST_HEAD(rcu_torture_freelist);
 153 static struct rcu_torture __rcu *rcu_torture_current;
 154 static unsigned long rcu_torture_current_version;
 155 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 156 static DEFINE_SPINLOCK(rcu_torture_lock);
 157 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
 158 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
 159 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 160 static atomic_t n_rcu_torture_alloc;
 161 static atomic_t n_rcu_torture_alloc_fail;
 162 static atomic_t n_rcu_torture_free;
 163 static atomic_t n_rcu_torture_mberror;
 164 static atomic_t n_rcu_torture_error;
 165 static long n_rcu_torture_barrier_error;
 166 static long n_rcu_torture_boost_ktrerror;
 167 static long n_rcu_torture_boost_rterror;
 168 static long n_rcu_torture_boost_failure;
 169 static long n_rcu_torture_boosts;
 170 static atomic_long_t n_rcu_torture_timers;
 171 static long n_barrier_attempts;
 172 static long n_barrier_successes; /* did rcu_barrier test succeed? */
 173 static unsigned long n_read_exits;
 174 static struct list_head rcu_torture_removed;
 175 static unsigned long shutdown_jiffies;
 176 static unsigned long start_gp_seq;
 177
 178 static int rcu_torture_writer_state;
 179 #define RTWS_FIXED_DELAY        0
 180 #define RTWS_DELAY              1
 181 #define RTWS_REPLACE            2
 182 #define RTWS_DEF_FREE           3
 183 #define RTWS_EXP_SYNC           4
 184 #define RTWS_COND_GET           5
 185 #define RTWS_COND_SYNC          6
 186 #define RTWS_SYNC               7
 187 #define RTWS_STUTTER            8
 188 #define RTWS_STOPPING           9
 189 static const char * const rcu_torture_writer_state_names[] = {
 190         "RTWS_FIXED_DELAY",
 191         "RTWS_DELAY",
 192         "RTWS_REPLACE",
 193         "RTWS_DEF_FREE",
 194         "RTWS_EXP_SYNC",
 195         "RTWS_COND_GET",
 196         "RTWS_COND_SYNC",
 197         "RTWS_SYNC",
 198         "RTWS_STUTTER",
 199         "RTWS_STOPPING",
 200 };
 201
 202 /* Record reader segment types and duration for first failing read. */
 203 struct rt_read_seg {
 204         int rt_readstate;
 205         unsigned long rt_delay_jiffies;
 206         unsigned long rt_delay_ms;
 207         unsigned long rt_delay_us;
 208         bool rt_preempted;
 209 };
 210 static int err_segs_recorded;
 211 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
 212 static int rt_read_nsegs;
 213
 214 static const char *rcu_torture_writer_state_getname(void)
 215 {
 216         unsigned int i = READ_ONCE(rcu_torture_writer_state);
 217
 218         if (i >= ARRAY_SIZE(rcu_torture_writer_state_names))
 219                 return "???";
 220         return rcu_torture_writer_state_names[i];
 221 }
 222
 223 #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU)
 224 #define rcu_can_boost() 1
 225 #else /* #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
 226 #define rcu_can_boost() 0
 227 #endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
 228
 229 #ifdef CONFIG_RCU_TRACE
 230 static u64 notrace rcu_trace_clock_local(void)
 231 {
 232         u64 ts = trace_clock_local();
 233
 234         (void)do_div(ts, NSEC_PER_USEC);
 235         return ts;
 236 }
 237 #else /* #ifdef CONFIG_RCU_TRACE */
 238 static u64 notrace rcu_trace_clock_local(void)
 239 {
 240         return 0ULL;
 241 }
 242 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 243
 244 /*
 245  * Stop aggressive CPU-hog tests a bit before the end of the test in order
 246  * to avoid interfering with test shutdown.
 247  */
 248 static bool shutdown_time_arrived(void)
 249 {
 250         return shutdown_secs && time_after(jiffies, shutdown_jiffies - 30 * HZ);
 251 }
 252
 253 static unsigned long boost_starttime;   /* jiffies of next boost test start. */
 254 static DEFINE_MUTEX(boost_mutex);       /* protect setting boost_starttime */
 255                                         /*  and boost task create/destroy. */
 256 static atomic_t barrier_cbs_count;      /* Barrier callbacks registered. */
 257 static bool barrier_phase;              /* Test phase. */
 258 static atomic_t barrier_cbs_invoked;    /* Barrier callbacks invoked. */
 259 static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
 260 static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
 261
 262 static bool rcu_fwd_cb_nodelay;         /* Short rcu_torture_delay() delays. */
 263
 264 /*
 265  * Allocate an element from the rcu_tortures pool.
 266  */
 267 static struct rcu_torture *
 268 rcu_torture_alloc(void)
 269 {
 270         struct list_head *p;
 271
 272         spin_lock_bh(&rcu_torture_lock);
 273         if (list_empty(&rcu_torture_freelist)) {
 274                 atomic_inc(&n_rcu_torture_alloc_fail);
 275                 spin_unlock_bh(&rcu_torture_lock);
 276                 return NULL;
 277         }
 278         atomic_inc(&n_rcu_torture_alloc);
 279         p = rcu_torture_freelist.next;
 280         list_del_init(p);
 281         spin_unlock_bh(&rcu_torture_lock);
 282         return container_of(p, struct rcu_torture, rtort_free);
 283 }
 284
 285 /*
 286  * Free an element to the rcu_tortures pool.
 287  */
 288 static void
 289 rcu_torture_free(struct rcu_torture *p)
 290 {
 291         atomic_inc(&n_rcu_torture_free);
 292         spin_lock_bh(&rcu_torture_lock);
 293         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 294         spin_unlock_bh(&rcu_torture_lock);
 295 }
 296
 297 /*
 298  * Operations vector for selecting different types of tests.
 299  */
 300
 301 struct rcu_torture_ops {
 302         int ttype;
 303         void (*init)(void);
 304         void (*cleanup)(void);
 305         int (*readlock)(void);
 306         void (*read_delay)(struct torture_random_state *rrsp,
 307                            struct rt_read_seg *rtrsp);
 308         void (*readunlock)(int idx);
 309         unsigned long (*get_gp_seq)(void);
 310         unsigned long (*gp_diff)(unsigned long new, unsigned long old);
 311         void (*deferred_free)(struct rcu_torture *p);
 312         void (*sync)(void);
 313         void (*exp_sync)(void);
 314         unsigned long (*get_state)(void);
 315         void (*cond_sync)(unsigned long oldstate);
 316         call_rcu_func_t call;
 317         void (*cb_barrier)(void);
 318         void (*fqs)(void);
 319         void (*stats)(void);
 320         int (*stall_dur)(void);
 321         int irq_capable;
 322         int can_boost;
 323         int extendables;
 324         int slow_gps;
 325         const char *name;
 326 };
 327
 328 static struct rcu_torture_ops *cur_ops;
 329
 330 /*
 331  * Definitions for rcu torture testing.
 332  */
 333
 334 static int rcu_torture_read_lock(void) __acquires(RCU)
 335 {
 336         rcu_read_lock();
 337         return 0;
 338 }
 339
 340 static void
 341 rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 342 {
 343         unsigned long started;
 344         unsigned long completed;
 345         const unsigned long shortdelay_us = 200;
 346         unsigned long longdelay_ms = 300;
 347         unsigned long long ts;
 348
 349         /* We want a short delay sometimes to make a reader delay the grace
 350          * period, and we want a long delay occasionally to trigger
 351          * force_quiescent_state. */
 352
 353         if (!READ_ONCE(rcu_fwd_cb_nodelay) &&
 354             !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
 355                 started = cur_ops->get_gp_seq();
 356                 ts = rcu_trace_clock_local();
 357                 if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK))
 358                         longdelay_ms = 5; /* Avoid triggering BH limits. */
 359                 mdelay(longdelay_ms);
 360                 rtrsp->rt_delay_ms = longdelay_ms;
 361                 completed = cur_ops->get_gp_seq();
 362                 do_trace_rcu_torture_read(cur_ops->name, NULL, ts,
 363                                           started, completed);
 364         }
 365         if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) {
 366                 udelay(shortdelay_us);
 367                 rtrsp->rt_delay_us = shortdelay_us;
 368         }
 369         if (!preempt_count() &&
 370             !(torture_random(rrsp) % (nrealreaders * 500))) {
 371                 torture_preempt_schedule();  /* QS only if preemptible. */
 372                 rtrsp->rt_preempted = true;
 373         }
 374 }
 375
 376 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 377 {
 378         rcu_read_unlock();
 379 }
 380
 381 /*
 382  * Update callback in the pipe.  This should be invoked after a grace period.
 383  */
 384 static bool
 385 rcu_torture_pipe_update_one(struct rcu_torture *rp)
 386 {
 387         int i;
 388
 389         i = READ_ONCE(rp->rtort_pipe_count);
 390         if (i > RCU_TORTURE_PIPE_LEN)
 391                 i = RCU_TORTURE_PIPE_LEN;
 392         atomic_inc(&rcu_torture_wcount[i]);
 393         WRITE_ONCE(rp->rtort_pipe_count, i + 1);
 394         if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 395                 rp->rtort_mbtest = 0;
 396                 return true;
 397         }
 398         return false;
 399 }
 400
 401 /*
 402  * Update all callbacks in the pipe.  Suitable for synchronous grace-period
 403  * primitives.
 404  */
 405 static void
 406 rcu_torture_pipe_update(struct rcu_torture *old_rp)
 407 {
 408         struct rcu_torture *rp;
 409         struct rcu_torture *rp1;
 410
 411         if (old_rp)
 412                 list_add(&old_rp->rtort_free, &rcu_torture_removed);
 413         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 414                 if (rcu_torture_pipe_update_one(rp)) {
 415                         list_del(&rp->rtort_free);
 416                         rcu_torture_free(rp);
 417                 }
 418         }
 419 }
 420
 421 static void
 422 rcu_torture_cb(struct rcu_head *p)
 423 {
 424         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 425
 426         if (torture_must_stop_irq()) {
 427                 /* Test is ending, just drop callbacks on the floor. */
 428                 /* The next initialization will pick up the pieces. */
 429                 return;
 430         }
 431         if (rcu_torture_pipe_update_one(rp))
 432                 rcu_torture_free(rp);
 433         else
 434                 cur_ops->deferred_free(rp);
 435 }
 436
 437 static unsigned long rcu_no_completed(void)
 438 {
 439         return 0;
 440 }
 441
 442 static void rcu_torture_deferred_free(struct rcu_torture *p)
 443 {
 444         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 445 }
 446
 447 static void rcu_sync_torture_init(void)
 448 {
 449         INIT_LIST_HEAD(&rcu_torture_removed);
 450 }
 451
 452 static struct rcu_torture_ops rcu_ops = {
 453         .ttype          = RCU_FLAVOR,
 454         .init           = rcu_sync_torture_init,
 455         .readlock       = rcu_torture_read_lock,
 456         .read_delay     = rcu_read_delay,
 457         .readunlock     = rcu_torture_read_unlock,
 458         .get_gp_seq     = rcu_get_gp_seq,
 459         .gp_diff        = rcu_seq_diff,
 460         .deferred_free  = rcu_torture_deferred_free,
 461         .sync           = synchronize_rcu,
 462         .exp_sync       = synchronize_rcu_expedited,
 463         .get_state      = get_state_synchronize_rcu,
 464         .cond_sync      = cond_synchronize_rcu,
 465         .call           = call_rcu,
 466         .cb_barrier     = rcu_barrier,
 467         .fqs            = rcu_force_quiescent_state,
 468         .stats          = NULL,
 469         .stall_dur      = rcu_jiffies_till_stall_check,
 470         .irq_capable    = 1,
 471         .can_boost      = rcu_can_boost(),
 472         .extendables    = RCUTORTURE_MAX_EXTEND,
 473         .name           = "rcu"
 474 };
 475
 476 /*
 477  * Don't even think about trying any of these in real life!!!
 478  * The names includes "busted", and they really means it!
 479  * The only purpose of these functions is to provide a buggy RCU
 480  * implementation to make sure that rcutorture correctly emits
 481  * buggy-RCU error messages.
 482  */
 483 static void rcu_busted_torture_deferred_free(struct rcu_torture *p)
 484 {
 485         /* This is a deliberate bug for testing purposes only! */
 486         rcu_torture_cb(&p->rtort_rcu);
 487 }
 488
 489 static void synchronize_rcu_busted(void)
 490 {
 491         /* This is a deliberate bug for testing purposes only! */
 492 }
 493
 494 static void
 495 call_rcu_busted(struct rcu_head *head, rcu_callback_t func)
 496 {
 497         /* This is a deliberate bug for testing purposes only! */
 498         func(head);
 499 }
 500
 501 static struct rcu_torture_ops rcu_busted_ops = {
 502         .ttype          = INVALID_RCU_FLAVOR,
 503         .init           = rcu_sync_torture_init,
 504         .readlock       = rcu_torture_read_lock,
 505         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 506         .readunlock     = rcu_torture_read_unlock,
 507         .get_gp_seq     = rcu_no_completed,
 508         .deferred_free  = rcu_busted_torture_deferred_free,
 509         .sync           = synchronize_rcu_busted,
 510         .exp_sync       = synchronize_rcu_busted,
 511         .call           = call_rcu_busted,
 512         .cb_barrier     = NULL,
 513         .fqs            = NULL,
 514         .stats          = NULL,
 515         .irq_capable    = 1,
 516         .name           = "busted"
 517 };
 518
 519 /*
 520  * Definitions for srcu torture testing.
 521  */
 522
 523 DEFINE_STATIC_SRCU(srcu_ctl);
 524 static struct srcu_struct srcu_ctld;
 525 static struct srcu_struct *srcu_ctlp = &srcu_ctl;
 526
 527 static int srcu_torture_read_lock(void) __acquires(srcu_ctlp)
 528 {
 529         return srcu_read_lock(srcu_ctlp);
 530 }
 531
 532 static void
 533 srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 534 {
 535         long delay;
 536         const long uspertick = 1000000 / HZ;
 537         const long longdelay = 10;
 538
 539         /* We want there to be long-running readers, but not all the time. */
 540
 541         delay = torture_random(rrsp) %
 542                 (nrealreaders * 2 * longdelay * uspertick);
 543         if (!delay && in_task()) {
 544                 schedule_timeout_interruptible(longdelay);
 545                 rtrsp->rt_delay_jiffies = longdelay;
 546         } else {
 547                 rcu_read_delay(rrsp, rtrsp);
 548         }
 549 }
 550
 551 static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp)
 552 {
 553         srcu_read_unlock(srcu_ctlp, idx);
 554 }
 555
 556 static unsigned long srcu_torture_completed(void)
 557 {
 558         return srcu_batches_completed(srcu_ctlp);
 559 }
 560
 561 static void srcu_torture_deferred_free(struct rcu_torture *rp)
 562 {
 563         call_srcu(srcu_ctlp, &rp->rtort_rcu, rcu_torture_cb);
 564 }
 565
 566 static void srcu_torture_synchronize(void)
 567 {
 568         synchronize_srcu(srcu_ctlp);
 569 }
 570
 571 static void srcu_torture_call(struct rcu_head *head,
 572                               rcu_callback_t func)
 573 {
 574         call_srcu(srcu_ctlp, head, func);
 575 }
 576
 577 static void srcu_torture_barrier(void)
 578 {
 579         srcu_barrier(srcu_ctlp);
 580 }
 581
 582 static void srcu_torture_stats(void)
 583 {
 584         srcu_torture_stats_print(srcu_ctlp, torture_type, TORTURE_FLAG);
 585 }
 586
 587 static void srcu_torture_synchronize_expedited(void)
 588 {
 589         synchronize_srcu_expedited(srcu_ctlp);
 590 }
 591
 592 static struct rcu_torture_ops srcu_ops = {
 593         .ttype          = SRCU_FLAVOR,
 594         .init           = rcu_sync_torture_init,
 595         .readlock       = srcu_torture_read_lock,
 596         .read_delay     = srcu_read_delay,
 597         .readunlock     = srcu_torture_read_unlock,
 598         .get_gp_seq     = srcu_torture_completed,
 599         .deferred_free  = srcu_torture_deferred_free,
 600         .sync           = srcu_torture_synchronize,
 601         .exp_sync       = srcu_torture_synchronize_expedited,
 602         .call           = srcu_torture_call,
 603         .cb_barrier     = srcu_torture_barrier,
 604         .stats          = srcu_torture_stats,
 605         .irq_capable    = 1,
 606         .name           = "srcu"
 607 };
 608
 609 static void srcu_torture_init(void)
 610 {
 611         rcu_sync_torture_init();
 612         WARN_ON(init_srcu_struct(&srcu_ctld));
 613         srcu_ctlp = &srcu_ctld;
 614 }
 615
 616 static void srcu_torture_cleanup(void)
 617 {
 618         cleanup_srcu_struct(&srcu_ctld);
 619         srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
 620 }
 621
 622 /* As above, but dynamically allocated. */
 623 static struct rcu_torture_ops srcud_ops = {
 624         .ttype          = SRCU_FLAVOR,
 625         .init           = srcu_torture_init,
 626         .cleanup        = srcu_torture_cleanup,
 627         .readlock       = srcu_torture_read_lock,
 628         .read_delay     = srcu_read_delay,
 629         .readunlock     = srcu_torture_read_unlock,
 630         .get_gp_seq     = srcu_torture_completed,
 631         .deferred_free  = srcu_torture_deferred_free,
 632         .sync           = srcu_torture_synchronize,
 633         .exp_sync       = srcu_torture_synchronize_expedited,
 634         .call           = srcu_torture_call,
 635         .cb_barrier     = srcu_torture_barrier,
 636         .stats          = srcu_torture_stats,
 637         .irq_capable    = 1,
 638         .name           = "srcud"
 639 };
 640
 641 /* As above, but broken due to inappropriate reader extension. */
 642 static struct rcu_torture_ops busted_srcud_ops = {
 643         .ttype          = SRCU_FLAVOR,
 644         .init           = srcu_torture_init,
 645         .cleanup        = srcu_torture_cleanup,
 646         .readlock       = srcu_torture_read_lock,
 647         .read_delay     = rcu_read_delay,
 648         .readunlock     = srcu_torture_read_unlock,
 649         .get_gp_seq     = srcu_torture_completed,
 650         .deferred_free  = srcu_torture_deferred_free,
 651         .sync           = srcu_torture_synchronize,
 652         .exp_sync       = srcu_torture_synchronize_expedited,
 653         .call           = srcu_torture_call,
 654         .cb_barrier     = srcu_torture_barrier,
 655         .stats          = srcu_torture_stats,
 656         .irq_capable    = 1,
 657         .extendables    = RCUTORTURE_MAX_EXTEND,
 658         .name           = "busted_srcud"
 659 };
 660
 661 /*
 662  * Definitions for RCU-tasks torture testing.
 663  */
 664
 665 static int tasks_torture_read_lock(void)
 666 {
 667         return 0;
 668 }
 669
 670 static void tasks_torture_read_unlock(int idx)
 671 {
 672 }
 673
 674 static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
 675 {
 676         call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
 677 }
 678
 679 static void synchronize_rcu_mult_test(void)
 680 {
 681         synchronize_rcu_mult(call_rcu_tasks, call_rcu);
 682 }
 683
 684 static struct rcu_torture_ops tasks_ops = {
 685         .ttype          = RCU_TASKS_FLAVOR,
 686         .init           = rcu_sync_torture_init,
 687         .readlock       = tasks_torture_read_lock,
 688         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 689         .readunlock     = tasks_torture_read_unlock,
 690         .get_gp_seq     = rcu_no_completed,
 691         .deferred_free  = rcu_tasks_torture_deferred_free,
 692         .sync           = synchronize_rcu_tasks,
 693         .exp_sync       = synchronize_rcu_mult_test,
 694         .call           = call_rcu_tasks,
 695         .cb_barrier     = rcu_barrier_tasks,
 696         .fqs            = NULL,
 697         .stats          = NULL,
 698         .irq_capable    = 1,
 699         .slow_gps       = 1,
 700         .name           = "tasks"
 701 };
 702
 703 /*
 704  * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
 705  * This implementation does not necessarily work well with CPU hotplug.
 706  */
 707
 708 static void synchronize_rcu_trivial(void)
 709 {
 710         int cpu;
 711
 712         for_each_online_cpu(cpu) {
 713                 rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
 714                 WARN_ON_ONCE(raw_smp_processor_id() != cpu);
 715         }
 716 }
 717
 718 static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
 719 {
 720         preempt_disable();
 721         return 0;
 722 }
 723
 724 static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
 725 {
 726         preempt_enable();
 727 }
 728
 729 static struct rcu_torture_ops trivial_ops = {
 730         .ttype          = RCU_TRIVIAL_FLAVOR,
 731         .init           = rcu_sync_torture_init,
 732         .readlock       = rcu_torture_read_lock_trivial,
 733         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 734         .readunlock     = rcu_torture_read_unlock_trivial,
 735         .get_gp_seq     = rcu_no_completed,
 736         .sync           = synchronize_rcu_trivial,
 737         .exp_sync       = synchronize_rcu_trivial,
 738         .fqs            = NULL,
 739         .stats          = NULL,
 740         .irq_capable    = 1,
 741         .name           = "trivial"
 742 };
 743
 744 /*
 745  * Definitions for rude RCU-tasks torture testing.
 746  */
 747
 748 static void rcu_tasks_rude_torture_deferred_free(struct rcu_torture *p)
 749 {
 750         call_rcu_tasks_rude(&p->rtort_rcu, rcu_torture_cb);
 751 }
 752
 753 static struct rcu_torture_ops tasks_rude_ops = {
 754         .ttype          = RCU_TASKS_RUDE_FLAVOR,
 755         .init           = rcu_sync_torture_init,
 756         .readlock       = rcu_torture_read_lock_trivial,
 757         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 758         .readunlock     = rcu_torture_read_unlock_trivial,
 759         .get_gp_seq     = rcu_no_completed,
 760         .deferred_free  = rcu_tasks_rude_torture_deferred_free,
 761         .sync           = synchronize_rcu_tasks_rude,
 762         .exp_sync       = synchronize_rcu_tasks_rude,
 763         .call           = call_rcu_tasks_rude,
 764         .cb_barrier     = rcu_barrier_tasks_rude,
 765         .fqs            = NULL,
 766         .stats          = NULL,
 767         .irq_capable    = 1,
 768         .name           = "tasks-rude"
 769 };
 770
 771 /*
 772  * Definitions for tracing RCU-tasks torture testing.
 773  */
 774
 775 static int tasks_tracing_torture_read_lock(void)
 776 {
 777         rcu_read_lock_trace();
 778         return 0;
 779 }
 780
 781 static void tasks_tracing_torture_read_unlock(int idx)
 782 {
 783         rcu_read_unlock_trace();
 784 }
 785
 786 static void rcu_tasks_tracing_torture_deferred_free(struct rcu_torture *p)
 787 {
 788         call_rcu_tasks_trace(&p->rtort_rcu, rcu_torture_cb);
 789 }
 790
 791 static struct rcu_torture_ops tasks_tracing_ops = {
 792         .ttype          = RCU_TASKS_TRACING_FLAVOR,
 793         .init           = rcu_sync_torture_init,
 794         .readlock       = tasks_tracing_torture_read_lock,
 795         .read_delay     = srcu_read_delay,  /* just reuse srcu's version. */
 796         .readunlock     = tasks_tracing_torture_read_unlock,
 797         .get_gp_seq     = rcu_no_completed,
 798         .deferred_free  = rcu_tasks_tracing_torture_deferred_free,
 799         .sync           = synchronize_rcu_tasks_trace,
 800         .exp_sync       = synchronize_rcu_tasks_trace,
 801         .call           = call_rcu_tasks_trace,
 802         .cb_barrier     = rcu_barrier_tasks_trace,
 803         .fqs            = NULL,
 804         .stats          = NULL,
 805         .irq_capable    = 1,
 806         .slow_gps       = 1,
 807         .name           = "tasks-tracing"
 808 };
 809
 810 static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
 811 {
 812         if (!cur_ops->gp_diff)
 813                 return new - old;
 814         return cur_ops->gp_diff(new, old);
 815 }
 816
 817 static bool __maybe_unused torturing_tasks(void)
 818 {
 819         return cur_ops == &tasks_ops || cur_ops == &tasks_rude_ops;
 820 }
 821
 822 /*
 823  * RCU torture priority-boost testing.  Runs one real-time thread per
 824  * CPU for moderate bursts, repeatedly registering RCU callbacks and
 825  * spinning waiting for them to be invoked.  If a given callback takes
 826  * too long to be invoked, we assume that priority inversion has occurred.
 827  */
 828
 829 struct rcu_boost_inflight {
 830         struct rcu_head rcu;
 831         int inflight;
 832 };
 833
 834 static void rcu_torture_boost_cb(struct rcu_head *head)
 835 {
 836         struct rcu_boost_inflight *rbip =
 837                 container_of(head, struct rcu_boost_inflight, rcu);
 838
 839         /* Ensure RCU-core accesses precede clearing ->inflight */
 840         smp_store_release(&rbip->inflight, 0);
 841 }
 842
 843 static int old_rt_runtime = -1;
 844
 845 static void rcu_torture_disable_rt_throttle(void)
 846 {
 847         /*
 848          * Disable RT throttling so that rcutorture's boost threads don't get
 849          * throttled. Only possible if rcutorture is built-in otherwise the
 850          * user should manually do this by setting the sched_rt_period_us and
 851          * sched_rt_runtime sysctls.
 852          */
 853         if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime != -1)
 854                 return;
 855
 856         old_rt_runtime = sysctl_sched_rt_runtime;
 857         sysctl_sched_rt_runtime = -1;
 858 }
 859
 860 static void rcu_torture_enable_rt_throttle(void)
 861 {
 862         if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime == -1)
 863                 return;
 864
 865         sysctl_sched_rt_runtime = old_rt_runtime;
 866         old_rt_runtime = -1;
 867 }
 868
 869 static bool rcu_torture_boost_failed(unsigned long start, unsigned long end)
 870 {
 871         if (end - start > test_boost_duration * HZ - HZ / 2) {
 872                 VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");
 873                 n_rcu_torture_boost_failure++;
 874
 875                 return true; /* failed */
 876         }
 877
 878         return false; /* passed */
 879 }
 880
 881 static int rcu_torture_boost(void *arg)
 882 {
 883         unsigned long call_rcu_time;
 884         unsigned long endtime;
 885         unsigned long oldstarttime;
 886         struct rcu_boost_inflight rbi = { .inflight = 0 };
 887
 888         VERBOSE_TOROUT_STRING("rcu_torture_boost started");
 889
 890         /* Set real-time priority. */
 891         sched_set_fifo_low(current);
 892
 893         init_rcu_head_on_stack(&rbi.rcu);
 894         /* Each pass through the following loop does one boost-test cycle. */
 895         do {
 896                 /* Track if the test failed already in this test interval? */
 897                 bool failed = false;
 898
 899                 /* Increment n_rcu_torture_boosts once per boost-test */
 900                 while (!kthread_should_stop()) {
 901                         if (mutex_trylock(&boost_mutex)) {
 902                                 n_rcu_torture_boosts++;
 903                                 mutex_unlock(&boost_mutex);
 904                                 break;
 905                         }
 906                         schedule_timeout_uninterruptible(1);
 907                 }
 908                 if (kthread_should_stop())
 909                         goto checkwait;
 910
 911                 /* Wait for the next test interval. */
 912                 oldstarttime = boost_starttime;
 913                 while (time_before(jiffies, oldstarttime)) {
 914                         schedule_timeout_interruptible(oldstarttime - jiffies);
 915                         stutter_wait("rcu_torture_boost");
 916                         if (torture_must_stop())
 917                                 goto checkwait;
 918                 }
 919
 920                 /* Do one boost-test interval. */
 921                 endtime = oldstarttime + test_boost_duration * HZ;
 922                 call_rcu_time = jiffies;
 923                 while (time_before(jiffies, endtime)) {
 924                         /* If we don't have a callback in flight, post one. */
 925                         if (!smp_load_acquire(&rbi.inflight)) {
 926                                 /* RCU core before ->inflight = 1. */
 927                                 smp_store_release(&rbi.inflight, 1);
 928                                 call_rcu(&rbi.rcu, rcu_torture_boost_cb);
 929                                 /* Check if the boost test failed */
 930                                 failed = failed ||
 931                                          rcu_torture_boost_failed(call_rcu_time,
 932                                                                  jiffies);
 933                                 call_rcu_time = jiffies;
 934                         }
 935                         stutter_wait("rcu_torture_boost");
 936                         if (torture_must_stop())
 937                                 goto checkwait;
 938                 }
 939
 940                 /*
 941                  * If boost never happened, then inflight will always be 1, in
 942                  * this case the boost check would never happen in the above
 943                  * loop so do another one here.
 944                  */
 945                 if (!failed && smp_load_acquire(&rbi.inflight))
 946                         rcu_torture_boost_failed(call_rcu_time, jiffies);
 947
 948                 /*
 949                  * Set the start time of the next test interval.
 950                  * Yes, this is vulnerable to long delays, but such
 951                  * delays simply cause a false negative for the next
 952                  * interval.  Besides, we are running at RT priority,
 953                  * so delays should be relatively rare.
 954                  */
 955                 while (oldstarttime == boost_starttime &&
 956                        !kthread_should_stop()) {
 957                         if (mutex_trylock(&boost_mutex)) {
 958                                 boost_starttime = jiffies +
 959                                                   test_boost_interval * HZ;
 960                                 mutex_unlock(&boost_mutex);
 961                                 break;
 962                         }
 963                         schedule_timeout_uninterruptible(1);
 964                 }
 965
 966                 /* Go do the stutter. */
 967 checkwait:      stutter_wait("rcu_torture_boost");
 968         } while (!torture_must_stop());
 969
 970         /* Clean up and exit. */
 971         while (!kthread_should_stop() || smp_load_acquire(&rbi.inflight)) {
 972                 torture_shutdown_absorb("rcu_torture_boost");
 973                 schedule_timeout_uninterruptible(1);
 974         }
 975         destroy_rcu_head_on_stack(&rbi.rcu);
 976         torture_kthread_stopping("rcu_torture_boost");
 977         return 0;
 978 }
 979
 980 /*
 981  * RCU torture force-quiescent-state kthread.  Repeatedly induces
 982  * bursts of calls to force_quiescent_state(), increasing the probability
 983  * of occurrence of some important types of race conditions.
 984  */
 985 static int
 986 rcu_torture_fqs(void *arg)
 987 {
 988         unsigned long fqs_resume_time;
 989         int fqs_burst_remaining;
 990
 991         VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
 992         do {
 993                 fqs_resume_time = jiffies + fqs_stutter * HZ;
 994                 while (time_before(jiffies, fqs_resume_time) &&
 995                        !kthread_should_stop()) {
 996                         schedule_timeout_interruptible(1);
 997                 }
 998                 fqs_burst_remaining = fqs_duration;
 999                 while (fqs_burst_remaining > 0 &&
1000                        !kthread_should_stop()) {
1001                         cur_ops->fqs();
1002                         udelay(fqs_holdoff);
1003                         fqs_burst_remaining -= fqs_holdoff;
1004                 }
1005                 stutter_wait("rcu_torture_fqs");
1006         } while (!torture_must_stop());
1007         torture_kthread_stopping("rcu_torture_fqs");
1008         return 0;
1009 }
1010
1011 /*
1012  * RCU torture writer kthread.  Repeatedly substitutes a new structure
1013  * for that pointed to by rcu_torture_current, freeing the old structure
1014  * after a series of grace periods (the "pipeline").
1015  */
1016 static int
1017 rcu_torture_writer(void *arg)
1018 {
1019         bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
1020         int expediting = 0;
1021         unsigned long gp_snap;
1022         bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
1023         bool gp_sync1 = gp_sync;
1024         int i;
1025         struct rcu_torture *rp;
1026         struct rcu_torture *old_rp;
1027         static DEFINE_TORTURE_RANDOM(rand);
1028         int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC,
1029                            RTWS_COND_GET, RTWS_SYNC };
1030         int nsynctypes = 0;
1031
1032         VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
1033         if (!can_expedite)
1034                 pr_alert("%s" TORTURE_FLAG
1035                          " GP expediting controlled from boot/sysfs for %s.\n",
1036                          torture_type, cur_ops->name);
1037
1038         /* Initialize synctype[] array.  If none set, take default. */
1039         if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync1)
1040                 gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true;
1041         if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync) {
1042                 synctype[nsynctypes++] = RTWS_COND_GET;
1043                 pr_info("%s: Testing conditional GPs.\n", __func__);
1044         } else if (gp_cond && (!cur_ops->get_state || !cur_ops->cond_sync)) {
1045                 pr_alert("%s: gp_cond without primitives.\n", __func__);
1046         }
1047         if (gp_exp1 && cur_ops->exp_sync) {
1048                 synctype[nsynctypes++] = RTWS_EXP_SYNC;
1049                 pr_info("%s: Testing expedited GPs.\n", __func__);
1050         } else if (gp_exp && !cur_ops->exp_sync) {
1051                 pr_alert("%s: gp_exp without primitives.\n", __func__);
1052         }
1053         if (gp_normal1 && cur_ops->deferred_free) {
1054                 synctype[nsynctypes++] = RTWS_DEF_FREE;
1055                 pr_info("%s: Testing asynchronous GPs.\n", __func__);
1056         } else if (gp_normal && !cur_ops->deferred_free) {
1057                 pr_alert("%s: gp_normal without primitives.\n", __func__);
1058         }
1059         if (gp_sync1 && cur_ops->sync) {
1060                 synctype[nsynctypes++] = RTWS_SYNC;
1061                 pr_info("%s: Testing normal GPs.\n", __func__);
1062         } else if (gp_sync && !cur_ops->sync) {
1063                 pr_alert("%s: gp_sync without primitives.\n", __func__);
1064         }
1065         if (WARN_ONCE(nsynctypes == 0,
1066                       "rcu_torture_writer: No update-side primitives.\n")) {
1067                 /*
1068                  * No updates primitives, so don't try updating.
1069                  * The resulting test won't be testing much, hence the
1070                  * above WARN_ONCE().
1071                  */
1072                 rcu_torture_writer_state = RTWS_STOPPING;
1073                 torture_kthread_stopping("rcu_torture_writer");
1074         }
1075
1076         do {
1077                 rcu_torture_writer_state = RTWS_FIXED_DELAY;
1078                 schedule_timeout_uninterruptible(1);
1079                 rp = rcu_torture_alloc();
1080                 if (rp == NULL)
1081                         continue;
1082                 rp->rtort_pipe_count = 0;
1083                 rcu_torture_writer_state = RTWS_DELAY;
1084                 udelay(torture_random(&rand) & 0x3ff);
1085                 rcu_torture_writer_state = RTWS_REPLACE;
1086                 old_rp = rcu_dereference_check(rcu_torture_current,
1087                                                current == writer_task);
1088                 rp->rtort_mbtest = 1;
1089                 rcu_assign_pointer(rcu_torture_current, rp);
1090                 smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
1091                 if (old_rp) {
1092                         i = old_rp->rtort_pipe_count;
1093                         if (i > RCU_TORTURE_PIPE_LEN)
1094                                 i = RCU_TORTURE_PIPE_LEN;
1095                         atomic_inc(&rcu_torture_wcount[i]);
1096                         WRITE_ONCE(old_rp->rtort_pipe_count,
1097                                    old_rp->rtort_pipe_count + 1);
1098                         switch (synctype[torture_random(&rand) % nsynctypes]) {
1099                         case RTWS_DEF_FREE:
1100                                 rcu_torture_writer_state = RTWS_DEF_FREE;
1101                                 cur_ops->deferred_free(old_rp);
1102                                 break;
1103                         case RTWS_EXP_SYNC:
1104                                 rcu_torture_writer_state = RTWS_EXP_SYNC;
1105                                 cur_ops->exp_sync();
1106                                 rcu_torture_pipe_update(old_rp);
1107                                 break;
1108                         case RTWS_COND_GET:
1109                                 rcu_torture_writer_state = RTWS_COND_GET;
1110                                 gp_snap = cur_ops->get_state();
1111                                 i = torture_random(&rand) % 16;
1112                                 if (i != 0)
1113                                         schedule_timeout_interruptible(i);
1114                                 udelay(torture_random(&rand) % 1000);
1115                                 rcu_torture_writer_state = RTWS_COND_SYNC;
1116                                 cur_ops->cond_sync(gp_snap);
1117                                 rcu_torture_pipe_update(old_rp);
1118                                 break;
1119                         case RTWS_SYNC:
1120                                 rcu_torture_writer_state = RTWS_SYNC;
1121                                 cur_ops->sync();
1122                                 rcu_torture_pipe_update(old_rp);
1123                                 break;
1124                         default:
1125                                 WARN_ON_ONCE(1);
1126                                 break;
1127                         }
1128                 }
1129                 WRITE_ONCE(rcu_torture_current_version,
1130                            rcu_torture_current_version + 1);
1131                 /* Cycle through nesting levels of rcu_expedite_gp() calls. */
1132                 if (can_expedite &&
1133                     !(torture_random(&rand) & 0xff & (!!expediting - 1))) {
1134                         WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited());
1135                         if (expediting >= 0)
1136                                 rcu_expedite_gp();
1137                         else
1138                                 rcu_unexpedite_gp();
1139                         if (++expediting > 3)
1140                                 expediting = -expediting;
1141                 } else if (!can_expedite) { /* Disabled during boot, recheck. */
1142                         can_expedite = !rcu_gp_is_expedited() &&
1143                                        !rcu_gp_is_normal();
1144                 }
1145                 rcu_torture_writer_state = RTWS_STUTTER;
1146                 if (stutter_wait("rcu_torture_writer") &&
1147                     !READ_ONCE(rcu_fwd_cb_nodelay) &&
1148                     !cur_ops->slow_gps &&
1149                     !torture_must_stop() &&
1150                     rcu_inkernel_boot_has_ended())
1151                         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
1152                                 if (list_empty(&rcu_tortures[i].rtort_free) &&
1153                                     rcu_access_pointer(rcu_torture_current) !=
1154                                     &rcu_tortures[i]) {
1155                                         rcu_ftrace_dump(DUMP_ALL);
1156                                         WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
1157                                 }
1158         } while (!torture_must_stop());
1159         rcu_torture_current = NULL;  // Let stats task know that we are done.
1160         /* Reset expediting back to unexpedited. */
1161         if (expediting > 0)
1162                 expediting = -expediting;
1163         while (can_expedite && expediting++ < 0)
1164                 rcu_unexpedite_gp();
1165         WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited());
1166         if (!can_expedite)
1167                 pr_alert("%s" TORTURE_FLAG
1168                          " Dynamic grace-period expediting was disabled.\n",
1169                          torture_type);
1170         rcu_torture_writer_state = RTWS_STOPPING;
1171         torture_kthread_stopping("rcu_torture_writer");
1172         return 0;
1173 }
1174
1175 /*
1176  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
1177  * delay between calls.
1178  */
1179 static int
1180 rcu_torture_fakewriter(void *arg)
1181 {
1182         DEFINE_TORTURE_RANDOM(rand);
1183
1184         VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
1185         set_user_nice(current, MAX_NICE);
1186
1187         do {
1188                 schedule_timeout_uninterruptible(1 + torture_random(&rand)%10);
1189                 udelay(torture_random(&rand) & 0x3ff);
1190                 if (cur_ops->cb_barrier != NULL &&
1191                     torture_random(&rand) % (nfakewriters * 8) == 0) {
1192                         cur_ops->cb_barrier();
1193                 } else if (gp_normal == gp_exp) {
1194                         if (cur_ops->sync && torture_random(&rand) & 0x80)
1195                                 cur_ops->sync();
1196                         else if (cur_ops->exp_sync)
1197                                 cur_ops->exp_sync();
1198                 } else if (gp_normal && cur_ops->sync) {
1199                         cur_ops->sync();
1200                 } else if (cur_ops->exp_sync) {
1201                         cur_ops->exp_sync();
1202                 }
1203                 stutter_wait("rcu_torture_fakewriter");
1204         } while (!torture_must_stop());
1205
1206         torture_kthread_stopping("rcu_torture_fakewriter");
1207         return 0;
1208 }
1209
1210 static void rcu_torture_timer_cb(struct rcu_head *rhp)
1211 {
1212         kfree(rhp);
1213 }
1214
1215 /*
1216  * Do one extension of an RCU read-side critical section using the
1217  * current reader state in readstate (set to zero for initial entry
1218  * to extended critical section), set the new state as specified by
1219  * newstate (set to zero for final exit from extended critical section),
1220  * and random-number-generator state in trsp.  If this is neither the
1221  * beginning or end of the critical section and if there was actually a
1222  * change, do a ->read_delay().
1223  */
1224 static void rcutorture_one_extend(int *readstate, int newstate,
1225                                   struct torture_random_state *trsp,
1226                                   struct rt_read_seg *rtrsp)
1227 {
1228         unsigned long flags;
1229         int idxnew = -1;
1230         int idxold = *readstate;
1231         int statesnew = ~*readstate & newstate;
1232         int statesold = *readstate & ~newstate;
1233
1234         WARN_ON_ONCE(idxold < 0);
1235         WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1);
1236         rtrsp->rt_readstate = newstate;
1237
1238         /* First, put new protection in place to avoid critical-section gap. */
1239         if (statesnew & RCUTORTURE_RDR_BH)
1240                 local_bh_disable();
1241         if (statesnew & RCUTORTURE_RDR_IRQ)
1242                 local_irq_disable();
1243         if (statesnew & RCUTORTURE_RDR_PREEMPT)
1244                 preempt_disable();
1245         if (statesnew & RCUTORTURE_RDR_RBH)
1246                 rcu_read_lock_bh();
1247         if (statesnew & RCUTORTURE_RDR_SCHED)
1248                 rcu_read_lock_sched();
1249         if (statesnew & RCUTORTURE_RDR_RCU)
1250                 idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT;
1251
1252         /* Next, remove old protection, irq first due to bh conflict. */
1253         if (statesold & RCUTORTURE_RDR_IRQ)
1254                 local_irq_enable();
1255         if (statesold & RCUTORTURE_RDR_BH)
1256                 local_bh_enable();
1257         if (statesold & RCUTORTURE_RDR_PREEMPT)
1258                 preempt_enable();
1259         if (statesold & RCUTORTURE_RDR_RBH)
1260                 rcu_read_unlock_bh();
1261         if (statesold & RCUTORTURE_RDR_SCHED)
1262                 rcu_read_unlock_sched();
1263         if (statesold & RCUTORTURE_RDR_RCU) {
1264                 bool lockit = !statesnew && !(torture_random(trsp) & 0xffff);
1265
1266                 if (lockit)
1267                         raw_spin_lock_irqsave(&current->pi_lock, flags);
1268                 cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT);
1269                 if (lockit)
1270                         raw_spin_unlock_irqrestore(&current->pi_lock, flags);
1271         }
1272
1273         /* Delay if neither beginning nor end and there was a change. */
1274         if ((statesnew || statesold) && *readstate && newstate)
1275                 cur_ops->read_delay(trsp, rtrsp);
1276
1277         /* Update the reader state. */
1278         if (idxnew == -1)
1279                 idxnew = idxold & ~RCUTORTURE_RDR_MASK;
1280         WARN_ON_ONCE(idxnew < 0);
1281         WARN_ON_ONCE((idxnew >> RCUTORTURE_RDR_SHIFT) > 1);
1282         *readstate = idxnew | newstate;
1283         WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) < 0);
1284         WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) > 1);
1285 }
1286
1287 /* Return the biggest extendables mask given current RCU and boot parameters. */
1288 static int rcutorture_extend_mask_max(void)
1289 {
1290         int mask;
1291
1292         WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND);
1293         mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables;
1294         mask = mask | RCUTORTURE_RDR_RCU;
1295         return mask;
1296 }
1297
1298 /* Return a random protection state mask, but with at least one bit set. */
1299 static int
1300 rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
1301 {
1302         int mask = rcutorture_extend_mask_max();
1303         unsigned long randmask1 = torture_random(trsp) >> 8;
1304         unsigned long randmask2 = randmask1 >> 3;
1305
1306         WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT);
1307         /* Mostly only one bit (need preemption!), sometimes lots of bits. */
1308         if (!(randmask1 & 0x7))
1309                 mask = mask & randmask2;
1310         else
1311                 mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));
1312         /* Can't enable bh w/irq disabled. */
1313         if ((mask & RCUTORTURE_RDR_IRQ) &&
1314             ((!(mask & RCUTORTURE_RDR_BH) && (oldmask & RCUTORTURE_RDR_BH)) ||
1315              (!(mask & RCUTORTURE_RDR_RBH) && (oldmask & RCUTORTURE_RDR_RBH))))
1316                 mask |= RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
1317         return mask ?: RCUTORTURE_RDR_RCU;
1318 }
1319
1320 /*
1321  * Do a randomly selected number of extensions of an existing RCU read-side
1322  * critical section.
1323  */
1324 static struct rt_read_seg *
1325 rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
1326                        struct rt_read_seg *rtrsp)
1327 {
1328         int i;
1329         int j;
1330         int mask = rcutorture_extend_mask_max();
1331
1332         WARN_ON_ONCE(!*readstate); /* -Existing- RCU read-side critsect! */
1333         if (!((mask - 1) & mask))
1334                 return rtrsp;  /* Current RCU reader not extendable. */
1335         /* Bias towards larger numbers of loops. */
1336         i = (torture_random(trsp) >> 3);
1337         i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
1338         for (j = 0; j < i; j++) {
1339                 mask = rcutorture_extend_mask(*readstate, trsp);
1340                 rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
1341         }
1342         return &rtrsp[j];
1343 }
1344
1345 /*
1346  * Do one read-side critical section, returning false if there was
1347  * no data to read.  Can be invoked both from process context and
1348  * from a timer handler.
1349  */
1350 static bool rcu_torture_one_read(struct torture_random_state *trsp)
1351 {
1352         int i;
1353         unsigned long started;
1354         unsigned long completed;
1355         int newstate;
1356         struct rcu_torture *p;
1357         int pipe_count;
1358         int readstate = 0;
1359         struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS] = { { 0 } };
1360         struct rt_read_seg *rtrsp = &rtseg[0];
1361         struct rt_read_seg *rtrsp1;
1362         unsigned long long ts;
1363
1364         WARN_ON_ONCE(!rcu_is_watching());
1365         newstate = rcutorture_extend_mask(readstate, trsp);
1366         rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
1367         started = cur_ops->get_gp_seq();
1368         ts = rcu_trace_clock_local();
1369         p = rcu_dereference_check(rcu_torture_current,
1370                                   rcu_read_lock_bh_held() ||
1371                                   rcu_read_lock_sched_held() ||
1372                                   srcu_read_lock_held(srcu_ctlp) ||
1373                                   rcu_read_lock_trace_held() ||
1374                                   torturing_tasks());
1375         if (p == NULL) {
1376                 /* Wait for rcu_torture_writer to get underway */
1377                 rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
1378                 return false;
1379         }
1380         if (p->rtort_mbtest == 0)
1381                 atomic_inc(&n_rcu_torture_mberror);
1382         rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
1383         preempt_disable();
1384         pipe_count = READ_ONCE(p->rtort_pipe_count);
1385         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
1386                 /* Should not happen, but... */
1387                 pipe_count = RCU_TORTURE_PIPE_LEN;
1388         }
1389         completed = cur_ops->get_gp_seq();
1390         if (pipe_count > 1) {
1391                 do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
1392                                           ts, started, completed);
1393                 rcu_ftrace_dump(DUMP_ALL);
1394         }
1395         __this_cpu_inc(rcu_torture_count[pipe_count]);
1396         completed = rcutorture_seq_diff(completed, started);
1397         if (completed > RCU_TORTURE_PIPE_LEN) {
1398                 /* Should not happen, but... */
1399                 completed = RCU_TORTURE_PIPE_LEN;
1400         }
1401         __this_cpu_inc(rcu_torture_batch[completed]);
1402         preempt_enable();
1403         rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
1404         WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK);
1405         // This next splat is expected behavior if leakpointer, especially
1406         // for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels.
1407         WARN_ON_ONCE(leakpointer && READ_ONCE(p->rtort_pipe_count) > 1);
1408
1409         /* If error or close call, record the sequence of reader protections. */
1410         if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
1411                 i = 0;
1412                 for (rtrsp1 = &rtseg[0]; rtrsp1 < rtrsp; rtrsp1++)
1413                         err_segs[i++] = *rtrsp1;
1414                 rt_read_nsegs = i;
1415         }
1416
1417         return true;
1418 }
1419
1420 static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);
1421
1422 /*
1423  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
1424  * incrementing the corresponding element of the pipeline array.  The
1425  * counter in the element should never be greater than 1, otherwise, the
1426  * RCU implementation is broken.
1427  */
1428 static void rcu_torture_timer(struct timer_list *unused)
1429 {
1430         atomic_long_inc(&n_rcu_torture_timers);
1431         (void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand));
1432
1433         /* Test call_rcu() invocation from interrupt handler. */
1434         if (cur_ops->call) {
1435                 struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_NOWAIT);
1436
1437                 if (rhp)
1438                         cur_ops->call(rhp, rcu_torture_timer_cb);
1439         }
1440 }
1441
1442 /*
1443  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
1444  * incrementing the corresponding element of the pipeline array.  The
1445  * counter in the element should never be greater than 1, otherwise, the
1446  * RCU implementation is broken.
1447  */
1448 static int
1449 rcu_torture_reader(void *arg)
1450 {
1451         unsigned long lastsleep = jiffies;
1452         long myid = (long)arg;
1453         int mynumonline = myid;
1454         DEFINE_TORTURE_RANDOM(rand);
1455         struct timer_list t;
1456
1457         VERBOSE_TOROUT_STRING("rcu_torture_reader task started");
1458         set_user_nice(current, MAX_NICE);
1459         if (irqreader && cur_ops->irq_capable)
1460                 timer_setup_on_stack(&t, rcu_torture_timer, 0);
1461         tick_dep_set_task(current, TICK_DEP_BIT_RCU);
1462         do {
1463                 if (irqreader && cur_ops->irq_capable) {
1464                         if (!timer_pending(&t))
1465                                 mod_timer(&t, jiffies + 1);
1466                 }
1467                 if (!rcu_torture_one_read(&rand) && !torture_must_stop())
1468                         schedule_timeout_interruptible(HZ);
1469                 if (time_after(jiffies, lastsleep) && !torture_must_stop()) {
1470                         schedule_timeout_interruptible(1);
1471                         lastsleep = jiffies + 10;
1472                 }
1473                 while (num_online_cpus() < mynumonline && !torture_must_stop())
1474                         schedule_timeout_interruptible(HZ / 5);
1475                 stutter_wait("rcu_torture_reader");
1476         } while (!torture_must_stop());
1477         if (irqreader && cur_ops->irq_capable) {
1478                 del_timer_sync(&t);
1479                 destroy_timer_on_stack(&t);
1480         }
1481         tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
1482         torture_kthread_stopping("rcu_torture_reader");
1483         return 0;
1484 }
1485
1486 /*
1487  * Print torture statistics.  Caller must ensure that there is only
1488  * one call to this function at a given time!!!  This is normally
1489  * accomplished by relying on the module system to only have one copy
1490  * of the module loaded, and then by giving the rcu_torture_stats
1491  * kthread full control (or the init/cleanup functions when rcu_torture_stats
1492  * thread is not running).
1493  */
1494 static void
1495 rcu_torture_stats_print(void)
1496 {
1497         int cpu;
1498         int i;
1499         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1500         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1501         struct rcu_torture *rtcp;
1502         static unsigned long rtcv_snap = ULONG_MAX;
1503         static bool splatted;
1504         struct task_struct *wtp;
1505
1506         for_each_possible_cpu(cpu) {
1507                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1508                         pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
1509                         batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
1510                 }
1511         }
1512         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
1513                 if (pipesummary[i] != 0)
1514                         break;
1515         }
1516
1517         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1518         rtcp = rcu_access_pointer(rcu_torture_current);
1519         pr_cont("rtc: %p %s: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
1520                 rtcp,
1521                 rtcp && !rcu_stall_is_suppressed_at_boot() ? "ver" : "VER",
1522                 rcu_torture_current_version,
1523                 list_empty(&rcu_torture_freelist),
1524                 atomic_read(&n_rcu_torture_alloc),
1525                 atomic_read(&n_rcu_torture_alloc_fail),
1526                 atomic_read(&n_rcu_torture_free));
1527         pr_cont("rtmbe: %d rtbe: %ld rtbke: %ld rtbre: %ld ",
1528                 atomic_read(&n_rcu_torture_mberror),
1529                 n_rcu_torture_barrier_error,
1530                 n_rcu_torture_boost_ktrerror,
1531                 n_rcu_torture_boost_rterror);
1532         pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
1533                 n_rcu_torture_boost_failure,
1534                 n_rcu_torture_boosts,
1535                 atomic_long_read(&n_rcu_torture_timers));
1536         torture_onoff_stats();
1537         pr_cont("barrier: %ld/%ld:%ld ",
1538                 data_race(n_barrier_successes),
1539                 data_race(n_barrier_attempts),
1540                 data_race(n_rcu_torture_barrier_error));
1541         pr_cont("read-exits: %ld\n", data_race(n_read_exits));
1542
1543         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1544         if (atomic_read(&n_rcu_torture_mberror) ||
1545             n_rcu_torture_barrier_error || n_rcu_torture_boost_ktrerror ||
1546             n_rcu_torture_boost_rterror || n_rcu_torture_boost_failure ||
1547             i > 1) {
1548                 pr_cont("%s", "!!! ");
1549                 atomic_inc(&n_rcu_torture_error);
1550                 WARN_ON_ONCE(atomic_read(&n_rcu_torture_mberror));
1551                 WARN_ON_ONCE(n_rcu_torture_barrier_error);  // rcu_barrier()
1552                 WARN_ON_ONCE(n_rcu_torture_boost_ktrerror); // no boost kthread
1553                 WARN_ON_ONCE(n_rcu_torture_boost_rterror); // can't set RT prio
1554                 WARN_ON_ONCE(n_rcu_torture_boost_failure); // RCU boost failed
1555                 WARN_ON_ONCE(i > 1); // Too-short grace period
1556         }
1557         pr_cont("Reader Pipe: ");
1558         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1559                 pr_cont(" %ld", pipesummary[i]);
1560         pr_cont("\n");
1561
1562         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1563         pr_cont("Reader Batch: ");
1564         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1565                 pr_cont(" %ld", batchsummary[i]);
1566         pr_cont("\n");
1567
1568         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1569         pr_cont("Free-Block Circulation: ");
1570         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1571                 pr_cont(" %d", atomic_read(&rcu_torture_wcount[i]));
1572         }
1573         pr_cont("\n");
1574
1575         if (cur_ops->stats)
1576                 cur_ops->stats();
1577         if (rtcv_snap == rcu_torture_current_version &&
1578             rcu_access_pointer(rcu_torture_current) &&
1579             !rcu_stall_is_suppressed()) {
1580                 int __maybe_unused flags = 0;
1581                 unsigned long __maybe_unused gp_seq = 0;
1582
1583                 rcutorture_get_gp_data(cur_ops->ttype,
1584                                        &flags, &gp_seq);
1585                 srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
1586                                         &flags, &gp_seq);
1587                 wtp = READ_ONCE(writer_task);
1588                 pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#lx cpu %d\n",
1589                          rcu_torture_writer_state_getname(),
1590                          rcu_torture_writer_state, gp_seq, flags,
1591                          wtp == NULL ? ~0UL : wtp->state,
1592                          wtp == NULL ? -1 : (int)task_cpu(wtp));
1593                 if (!splatted && wtp) {
1594                         sched_show_task(wtp);
1595                         splatted = true;
1596                 }
1597                 show_rcu_gp_kthreads();
1598                 rcu_ftrace_dump(DUMP_ALL);
1599         }
1600         rtcv_snap = rcu_torture_current_version;
1601 }
1602
1603 /*
1604  * Periodically prints torture statistics, if periodic statistics printing
1605  * was specified via the stat_interval module parameter.
1606  */
1607 static int
1608 rcu_torture_stats(void *arg)
1609 {
1610         VERBOSE_TOROUT_STRING("rcu_torture_stats task started");
1611         do {
1612                 schedule_timeout_interruptible(stat_interval * HZ);
1613                 rcu_torture_stats_print();
1614                 torture_shutdown_absorb("rcu_torture_stats");
1615         } while (!torture_must_stop());
1616         torture_kthread_stopping("rcu_torture_stats");
1617         return 0;
1618 }
1619
1620 static void
1621 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
1622 {
1623         pr_alert("%s" TORTURE_FLAG
1624                  "--- %s: nreaders=%d nfakewriters=%d "
1625                  "stat_interval=%d verbose=%d test_no_idle_hz=%d "
1626                  "shuffle_interval=%d stutter=%d irqreader=%d "
1627                  "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
1628                  "test_boost=%d/%d test_boost_interval=%d "
1629                  "test_boost_duration=%d shutdown_secs=%d "
1630                  "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
1631                  "stall_cpu_block=%d "
1632                  "n_barrier_cbs=%d "
1633                  "onoff_interval=%d onoff_holdoff=%d "
1634                  "read_exit_delay=%d read_exit_burst=%d\n",
1635                  torture_type, tag, nrealreaders, nfakewriters,
1636                  stat_interval, verbose, test_no_idle_hz, shuffle_interval,
1637                  stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
1638                  test_boost, cur_ops->can_boost,
1639                  test_boost_interval, test_boost_duration, shutdown_secs,
1640                  stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
1641                  stall_cpu_block,
1642                  n_barrier_cbs,
1643                  onoff_interval, onoff_holdoff,
1644                  read_exit_delay, read_exit_burst);
1645 }
1646
1647 static int rcutorture_booster_cleanup(unsigned int cpu)
1648 {
1649         struct task_struct *t;
1650
1651         if (boost_tasks[cpu] == NULL)
1652                 return 0;
1653         mutex_lock(&boost_mutex);
1654         t = boost_tasks[cpu];
1655         boost_tasks[cpu] = NULL;
1656         rcu_torture_enable_rt_throttle();
1657         mutex_unlock(&boost_mutex);
1658
1659         /* This must be outside of the mutex, otherwise deadlock! */
1660         torture_stop_kthread(rcu_torture_boost, t);
1661         return 0;
1662 }
1663
1664 static int rcutorture_booster_init(unsigned int cpu)
1665 {
1666         int retval;
1667
1668         if (boost_tasks[cpu] != NULL)
1669                 return 0;  /* Already created, nothing more to do. */
1670
1671         /* Don't allow time recalculation while creating a new task. */
1672         mutex_lock(&boost_mutex);
1673         rcu_torture_disable_rt_throttle();
1674         VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
1675         boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL,
1676                                                   cpu_to_node(cpu),
1677                                                   "rcu_torture_boost");
1678         if (IS_ERR(boost_tasks[cpu])) {
1679                 retval = PTR_ERR(boost_tasks[cpu]);
1680                 VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed");
1681                 n_rcu_torture_boost_ktrerror++;
1682                 boost_tasks[cpu] = NULL;
1683                 mutex_unlock(&boost_mutex);
1684                 return retval;
1685         }
1686         kthread_bind(boost_tasks[cpu], cpu);
1687         wake_up_process(boost_tasks[cpu]);
1688         mutex_unlock(&boost_mutex);
1689         return 0;
1690 }
1691
1692 /*
1693  * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then
1694  * induces a CPU stall for the time specified by stall_cpu.
1695  */
1696 static int rcu_torture_stall(void *args)
1697 {
1698         int idx;
1699         unsigned long stop_at;
1700
1701         VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
1702         if (stall_cpu_holdoff > 0) {
1703                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
1704                 schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
1705                 VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
1706         }
1707         if (!kthread_should_stop() && stall_gp_kthread > 0) {
1708                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin GP stall");
1709                 rcu_gp_set_torture_wait(stall_gp_kthread * HZ);
1710                 for (idx = 0; idx < stall_gp_kthread + 2; idx++) {
1711                         if (kthread_should_stop())
1712                                 break;
1713                         schedule_timeout_uninterruptible(HZ);
1714                 }
1715         }
1716         if (!kthread_should_stop() && stall_cpu > 0) {
1717                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin CPU stall");
1718                 stop_at = ktime_get_seconds() + stall_cpu;
1719                 /* RCU CPU stall is expected behavior in following code. */
1720                 idx = cur_ops->readlock();
1721                 if (stall_cpu_irqsoff)
1722                         local_irq_disable();
1723                 else if (!stall_cpu_block)
1724                         preempt_disable();
1725                 pr_alert("rcu_torture_stall start on CPU %d.\n",
1726                          raw_smp_processor_id());
1727                 while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
1728                                     stop_at))
1729                         if (stall_cpu_block)
1730                                 schedule_timeout_uninterruptible(HZ);
1731                 if (stall_cpu_irqsoff)
1732                         local_irq_enable();
1733                 else if (!stall_cpu_block)
1734                         preempt_enable();
1735                 cur_ops->readunlock(idx);
1736         }
1737         pr_alert("rcu_torture_stall end.\n");
1738         torture_shutdown_absorb("rcu_torture_stall");
1739         while (!kthread_should_stop())
1740                 schedule_timeout_interruptible(10 * HZ);
1741         return 0;
1742 }
1743
1744 /* Spawn CPU-stall kthread, if stall_cpu specified. */
1745 static int __init rcu_torture_stall_init(void)
1746 {
1747         if (stall_cpu <= 0 && stall_gp_kthread <= 0)
1748                 return 0;
1749         return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
1750 }
1751
1752 /* State structure for forward-progress self-propagating RCU callback. */
1753 struct fwd_cb_state {
1754         struct rcu_head rh;
1755         int stop;
1756 };
1757
1758 /*
1759  * Forward-progress self-propagating RCU callback function.  Because
1760  * callbacks run from softirq, this function is an implicit RCU read-side
1761  * critical section.
1762  */
1763 static void rcu_torture_fwd_prog_cb(struct rcu_head *rhp)
1764 {
1765         struct fwd_cb_state *fcsp = container_of(rhp, struct fwd_cb_state, rh);
1766
1767         if (READ_ONCE(fcsp->stop)) {
1768                 WRITE_ONCE(fcsp->stop, 2);
1769                 return;
1770         }
1771         cur_ops->call(&fcsp->rh, rcu_torture_fwd_prog_cb);
1772 }
1773
1774 /* State for continuous-flood RCU callbacks. */
1775 struct rcu_fwd_cb {
1776         struct rcu_head rh;
1777         struct rcu_fwd_cb *rfc_next;
1778         struct rcu_fwd *rfc_rfp;
1779         int rfc_gps;
1780 };
1781
1782 #define MAX_FWD_CB_JIFFIES      (8 * HZ) /* Maximum CB test duration. */
1783 #define MIN_FWD_CB_LAUNDERS     3       /* This many CB invocations to count. */
1784 #define MIN_FWD_CBS_LAUNDERED   100     /* Number of counted CBs. */
1785 #define FWD_CBS_HIST_DIV        10      /* Histogram buckets/second. */
1786 #define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))
1787
1788 struct rcu_launder_hist {
1789         long n_launders;
1790         unsigned long launder_gp_seq;
1791 };
1792
1793 struct rcu_fwd {
1794         spinlock_t rcu_fwd_lock;
1795         struct rcu_fwd_cb *rcu_fwd_cb_head;
1796         struct rcu_fwd_cb **rcu_fwd_cb_tail;
1797         long n_launders_cb;
1798         unsigned long rcu_fwd_startat;
1799         struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
1800         unsigned long rcu_launder_gp_seq_start;
1801 };
1802
1803 static DEFINE_MUTEX(rcu_fwd_mutex);
1804 static struct rcu_fwd *rcu_fwds;
1805 static bool rcu_fwd_emergency_stop;
1806
1807 static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
1808 {
1809         unsigned long gps;
1810         unsigned long gps_old;
1811         int i;
1812         int j;
1813
1814         for (i = ARRAY_SIZE(rfp->n_launders_hist) - 1; i > 0; i--)
1815                 if (rfp->n_launders_hist[i].n_launders > 0)
1816                         break;
1817         pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):",
1818                  __func__, jiffies - rfp->rcu_fwd_startat);
1819         gps_old = rfp->rcu_launder_gp_seq_start;
1820         for (j = 0; j <= i; j++) {
1821                 gps = rfp->n_launders_hist[j].launder_gp_seq;
1822                 pr_cont(" %ds/%d: %ld:%ld",
1823                         j + 1, FWD_CBS_HIST_DIV,
1824                         rfp->n_launders_hist[j].n_launders,
1825                         rcutorture_seq_diff(gps, gps_old));
1826                 gps_old = gps;
1827         }
1828         pr_cont("\n");
1829 }
1830
1831 /* Callback function for continuous-flood RCU callbacks. */
1832 static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
1833 {
1834         unsigned long flags;
1835         int i;
1836         struct rcu_fwd_cb *rfcp = container_of(rhp, struct rcu_fwd_cb, rh);
1837         struct rcu_fwd_cb **rfcpp;
1838         struct rcu_fwd *rfp = rfcp->rfc_rfp;
1839
1840         rfcp->rfc_next = NULL;
1841         rfcp->rfc_gps++;
1842         spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
1843         rfcpp = rfp->rcu_fwd_cb_tail;
1844         rfp->rcu_fwd_cb_tail = &rfcp->rfc_next;
1845         WRITE_ONCE(*rfcpp, rfcp);
1846         WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1);
1847         i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
1848         if (i >= ARRAY_SIZE(rfp->n_launders_hist))
1849                 i = ARRAY_SIZE(rfp->n_launders_hist) - 1;
1850         rfp->n_launders_hist[i].n_launders++;
1851         rfp->n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();
1852         spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
1853 }
1854
1855 // Give the scheduler a chance, even on nohz_full CPUs.
1856 static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)
1857 {
1858         if (IS_ENABLED(CONFIG_PREEMPTION) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
1859                 // Real call_rcu() floods hit userspace, so emulate that.
1860                 if (need_resched() || (iter & 0xfff))
1861                         schedule();
1862                 return;
1863         }
1864         // No userspace emulation: CB invocation throttles call_rcu()
1865         cond_resched();
1866 }
1867
1868 /*
1869  * Free all callbacks on the rcu_fwd_cb_head list, either because the
1870  * test is over or because we hit an OOM event.
1871  */
1872 static unsigned long rcu_torture_fwd_prog_cbfree(struct rcu_fwd *rfp)
1873 {
1874         unsigned long flags;
1875         unsigned long freed = 0;
1876         struct rcu_fwd_cb *rfcp;
1877
1878         for (;;) {
1879                 spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
1880                 rfcp = rfp->rcu_fwd_cb_head;
1881                 if (!rfcp) {
1882                         spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
1883                         break;
1884                 }
1885                 rfp->rcu_fwd_cb_head = rfcp->rfc_next;
1886                 if (!rfp->rcu_fwd_cb_head)
1887                         rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
1888                 spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
1889                 kfree(rfcp);
1890                 freed++;
1891                 rcu_torture_fwd_prog_cond_resched(freed);
1892                 if (tick_nohz_full_enabled()) {
1893                         local_irq_save(flags);
1894                         rcu_momentary_dyntick_idle();
1895                         local_irq_restore(flags);
1896                 }
1897         }
1898         return freed;
1899 }
1900
1901 /* Carry out need_resched()/cond_resched() forward-progress testing. */
1902 static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
1903                                     int *tested, int *tested_tries)
1904 {
1905         unsigned long cver;
1906         unsigned long dur;
1907         struct fwd_cb_state fcs;
1908         unsigned long gps;
1909         int idx;
1910         int sd;
1911         int sd4;
1912         bool selfpropcb = false;
1913         unsigned long stopat;
1914         static DEFINE_TORTURE_RANDOM(trs);
1915
1916         if  (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) {
1917                 init_rcu_head_on_stack(&fcs.rh);
1918                 selfpropcb = true;
1919         }
1920
1921         /* Tight loop containing cond_resched(). */
1922         WRITE_ONCE(rcu_fwd_cb_nodelay, true);
1923         cur_ops->sync(); /* Later readers see above write. */
1924         if  (selfpropcb) {
1925                 WRITE_ONCE(fcs.stop, 0);
1926                 cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
1927         }
1928         cver = READ_ONCE(rcu_torture_current_version);
1929         gps = cur_ops->get_gp_seq();
1930         sd = cur_ops->stall_dur() + 1;
1931         sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
1932         dur = sd4 + torture_random(&trs) % (sd - sd4);
1933         WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
1934         stopat = rfp->rcu_fwd_startat + dur;
1935         while (time_before(jiffies, stopat) &&
1936                !shutdown_time_arrived() &&
1937                !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
1938                 idx = cur_ops->readlock();
1939                 udelay(10);
1940                 cur_ops->readunlock(idx);
1941                 if (!fwd_progress_need_resched || need_resched())
1942                         cond_resched();
1943         }
1944         (*tested_tries)++;
1945         if (!time_before(jiffies, stopat) &&
1946             !shutdown_time_arrived() &&
1947             !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
1948                 (*tested)++;
1949                 cver = READ_ONCE(rcu_torture_current_version) - cver;
1950                 gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
1951                 WARN_ON(!cver && gps < 2);
1952                 pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps);
1953         }
1954         if (selfpropcb) {
1955                 WRITE_ONCE(fcs.stop, 1);
1956                 cur_ops->sync(); /* Wait for running CB to complete. */
1957                 cur_ops->cb_barrier(); /* Wait for queued callbacks. */
1958         }
1959
1960         if (selfpropcb) {
1961                 WARN_ON(READ_ONCE(fcs.stop) != 2);
1962                 destroy_rcu_head_on_stack(&fcs.rh);
1963         }
1964         schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
1965         WRITE_ONCE(rcu_fwd_cb_nodelay, false);
1966 }
1967
1968 /* Carry out call_rcu() forward-progress testing. */
1969 static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
1970 {
1971         unsigned long cver;
1972         unsigned long flags;
1973         unsigned long gps;
1974         int i;
1975         long n_launders;
1976         long n_launders_cb_snap;
1977         long n_launders_sa;
1978         long n_max_cbs;
1979         long n_max_gps;
1980         struct rcu_fwd_cb *rfcp;
1981         struct rcu_fwd_cb *rfcpn;
1982         unsigned long stopat;
1983         unsigned long stoppedat;
1984
1985         if (READ_ONCE(rcu_fwd_emergency_stop))
1986                 return; /* Get out of the way quickly, no GP wait! */
1987         if (!cur_ops->call)
1988                 return; /* Can't do call_rcu() fwd prog without ->call. */
1989
1990         /* Loop continuously posting RCU callbacks. */
1991         WRITE_ONCE(rcu_fwd_cb_nodelay, true);
1992         cur_ops->sync(); /* Later readers see above write. */
1993         WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
1994         stopat = rfp->rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
1995         n_launders = 0;
1996         rfp->n_launders_cb = 0; // Hoist initialization for multi-kthread
1997         n_launders_sa = 0;
1998         n_max_cbs = 0;
1999         n_max_gps = 0;
2000         for (i = 0; i < ARRAY_SIZE(rfp->n_launders_hist); i++)
2001                 rfp->n_launders_hist[i].n_launders = 0;
2002         cver = READ_ONCE(rcu_torture_current_version);
2003         gps = cur_ops->get_gp_seq();
2004         rfp->rcu_launder_gp_seq_start = gps;
2005         tick_dep_set_task(current, TICK_DEP_BIT_RCU);
2006         while (time_before(jiffies, stopat) &&
2007                !shutdown_time_arrived() &&
2008                !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
2009                 rfcp = READ_ONCE(rfp->rcu_fwd_cb_head);
2010                 rfcpn = NULL;
2011                 if (rfcp)
2012                         rfcpn = READ_ONCE(rfcp->rfc_next);
2013                 if (rfcpn) {
2014                         if (rfcp->rfc_gps >= MIN_FWD_CB_LAUNDERS &&
2015                             ++n_max_gps >= MIN_FWD_CBS_LAUNDERED)
2016                                 break;
2017                         rfp->rcu_fwd_cb_head = rfcpn;
2018                         n_launders++;
2019                         n_launders_sa++;
2020                 } else {
2021                         rfcp = kmalloc(sizeof(*rfcp), GFP_KERNEL);
2022                         if (WARN_ON_ONCE(!rfcp)) {
2023                                 schedule_timeout_interruptible(1);
2024                                 continue;
2025                         }
2026                         n_max_cbs++;
2027                         n_launders_sa = 0;
2028                         rfcp->rfc_gps = 0;
2029                         rfcp->rfc_rfp = rfp;
2030                 }
2031                 cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
2032                 rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
2033                 if (tick_nohz_full_enabled()) {
2034                         local_irq_save(flags);
2035                         rcu_momentary_dyntick_idle();
2036                         local_irq_restore(flags);
2037                 }
2038         }
2039         stoppedat = jiffies;
2040         n_launders_cb_snap = READ_ONCE(rfp->n_launders_cb);
2041         cver = READ_ONCE(rcu_torture_current_version) - cver;
2042         gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
2043         cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
2044         (void)rcu_torture_fwd_prog_cbfree(rfp);
2045
2046         if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop) &&
2047             !shutdown_time_arrived()) {
2048                 WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
2049                 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",
2050                          __func__,
2051                          stoppedat - rfp->rcu_fwd_startat, jiffies - stoppedat,
2052                          n_launders + n_max_cbs - n_launders_cb_snap,
2053                          n_launders, n_launders_sa,
2054                          n_max_gps, n_max_cbs, cver, gps);
2055                 rcu_torture_fwd_cb_hist(rfp);
2056         }
2057         schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
2058         tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
2059         WRITE_ONCE(rcu_fwd_cb_nodelay, false);
2060 }
2061
2062
2063 /*
2064  * OOM notifier, but this only prints diagnostic information for the
2065  * current forward-progress test.
2066  */
2067 static int rcutorture_oom_notify(struct notifier_block *self,
2068                                  unsigned long notused, void *nfreed)
2069 {
2070         struct rcu_fwd *rfp;
2071
2072         mutex_lock(&rcu_fwd_mutex);
2073         rfp = rcu_fwds;
2074         if (!rfp) {
2075                 mutex_unlock(&rcu_fwd_mutex);
2076                 return NOTIFY_OK;
2077         }
2078         WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
2079              __func__);
2080         rcu_torture_fwd_cb_hist(rfp);
2081         rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rfp->rcu_fwd_startat)) / 2);
2082         WRITE_ONCE(rcu_fwd_emergency_stop, true);
2083         smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
2084         pr_info("%s: Freed %lu RCU callbacks.\n",
2085                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
2086         rcu_barrier();
2087         pr_info("%s: Freed %lu RCU callbacks.\n",
2088                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
2089         rcu_barrier();
2090         pr_info("%s: Freed %lu RCU callbacks.\n",
2091                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
2092         smp_mb(); /* Frees before return to avoid redoing OOM. */
2093         (*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */
2094         pr_info("%s returning after OOM processing.\n", __func__);
2095         mutex_unlock(&rcu_fwd_mutex);
2096         return NOTIFY_OK;
2097 }
2098
2099 static struct notifier_block rcutorture_oom_nb = {
2100         .notifier_call = rcutorture_oom_notify
2101 };
2102
2103 /* Carry out grace-period forward-progress testing. */
2104 static int rcu_torture_fwd_prog(void *args)
2105 {
2106         struct rcu_fwd *rfp = args;
2107         int tested = 0;
2108         int tested_tries = 0;
2109
2110         VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
2111         rcu_bind_current_to_nocb();
2112         if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST))
2113                 set_user_nice(current, MAX_NICE);
2114         do {
2115                 schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
2116                 WRITE_ONCE(rcu_fwd_emergency_stop, false);
2117                 if (!IS_ENABLED(CONFIG_TINY_RCU) ||
2118                     rcu_inkernel_boot_has_ended())
2119                         rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
2120                 if (rcu_inkernel_boot_has_ended())
2121                         rcu_torture_fwd_prog_cr(rfp);
2122
2123                 /* Avoid slow periods, better to test when busy. */
2124                 stutter_wait("rcu_torture_fwd_prog");
2125         } while (!torture_must_stop());
2126         /* Short runs might not contain a valid forward-progress attempt. */
2127         WARN_ON(!tested && tested_tries >= 5);
2128         pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
2129         torture_kthread_stopping("rcu_torture_fwd_prog");
2130         return 0;
2131 }
2132
2133 /* If forward-progress checking is requested and feasible, spawn the thread. */
2134 static int __init rcu_torture_fwd_prog_init(void)
2135 {
2136         struct rcu_fwd *rfp;
2137
2138         if (!fwd_progress)
2139                 return 0; /* Not requested, so don't do it. */
2140         if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0 ||
2141             cur_ops == &rcu_busted_ops) {
2142                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
2143                 return 0;
2144         }
2145         if (stall_cpu > 0) {
2146                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
2147                 if (IS_MODULE(CONFIG_RCU_TORTURE_TESTS))
2148                         return -EINVAL; /* In module, can fail back to user. */
2149                 WARN_ON(1); /* Make sure rcutorture notices conflict. */
2150                 return 0;
2151         }
2152         if (fwd_progress_holdoff <= 0)
2153                 fwd_progress_holdoff = 1;
2154         if (fwd_progress_div <= 0)
2155                 fwd_progress_div = 4;
2156         rfp = kzalloc(sizeof(*rfp), GFP_KERNEL);
2157         if (!rfp)
2158                 return -ENOMEM;
2159         spin_lock_init(&rfp->rcu_fwd_lock);
2160         rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
2161         mutex_lock(&rcu_fwd_mutex);
2162         rcu_fwds = rfp;
2163         mutex_unlock(&rcu_fwd_mutex);
2164         register_oom_notifier(&rcutorture_oom_nb);
2165         return torture_create_kthread(rcu_torture_fwd_prog, rfp, fwd_prog_task);
2166 }
2167
2168 static void rcu_torture_fwd_prog_cleanup(void)
2169 {
2170         struct rcu_fwd *rfp;
2171
2172         torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
2173         rfp = rcu_fwds;
2174         mutex_lock(&rcu_fwd_mutex);
2175         rcu_fwds = NULL;
2176         mutex_unlock(&rcu_fwd_mutex);
2177         unregister_oom_notifier(&rcutorture_oom_nb);
2178         kfree(rfp);
2179 }
2180
2181 /* Callback function for RCU barrier testing. */
2182 static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
2183 {
2184         atomic_inc(&barrier_cbs_invoked);
2185 }
2186
2187 /* IPI handler to get callback posted on desired CPU, if online. */
2188 static void rcu_torture_barrier1cb(void *rcu_void)
2189 {
2190         struct rcu_head *rhp = rcu_void;
2191
2192         cur_ops->call(rhp, rcu_torture_barrier_cbf);
2193 }
2194
2195 /* kthread function to register callbacks used to test RCU barriers. */
2196 static int rcu_torture_barrier_cbs(void *arg)
2197 {
2198         long myid = (long)arg;
2199         bool lastphase = false;
2200         bool newphase;
2201         struct rcu_head rcu;
2202
2203         init_rcu_head_on_stack(&rcu);
2204         VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started");
2205         set_user_nice(current, MAX_NICE);
2206         do {
2207                 wait_event(barrier_cbs_wq[myid],
2208                            (newphase =
2209                             smp_load_acquire(&barrier_phase)) != lastphase ||
2210                            torture_must_stop());
2211                 lastphase = newphase;
2212                 if (torture_must_stop())
2213                         break;
2214                 /*
2215                  * The above smp_load_acquire() ensures barrier_phase load
2216                  * is ordered before the following ->call().
2217                  */
2218                 if (smp_call_function_single(myid, rcu_torture_barrier1cb,
2219                                              &rcu, 1)) {
2220                         // IPI failed, so use direct call from current CPU.
2221                         cur_ops->call(&rcu, rcu_torture_barrier_cbf);
2222                 }
2223                 if (atomic_dec_and_test(&barrier_cbs_count))
2224                         wake_up(&barrier_wq);
2225         } while (!torture_must_stop());
2226         if (cur_ops->cb_barrier != NULL)
2227                 cur_ops->cb_barrier();
2228         destroy_rcu_head_on_stack(&rcu);
2229         torture_kthread_stopping("rcu_torture_barrier_cbs");
2230         return 0;
2231 }
2232
2233 /* kthread function to drive and coordinate RCU barrier testing. */
2234 static int rcu_torture_barrier(void *arg)
2235 {
2236         int i;
2237
2238         VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting");
2239         do {
2240                 atomic_set(&barrier_cbs_invoked, 0);
2241                 atomic_set(&barrier_cbs_count, n_barrier_cbs);
2242                 /* Ensure barrier_phase ordered after prior assignments. */
2243                 smp_store_release(&barrier_phase, !barrier_phase);
2244                 for (i = 0; i < n_barrier_cbs; i++)
2245                         wake_up(&barrier_cbs_wq[i]);
2246                 wait_event(barrier_wq,
2247                            atomic_read(&barrier_cbs_count) == 0 ||
2248                            torture_must_stop());
2249                 if (torture_must_stop())
2250                         break;
2251                 n_barrier_attempts++;
2252                 cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
2253                 if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
2254                         n_rcu_torture_barrier_error++;
2255                         pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
2256                                atomic_read(&barrier_cbs_invoked),
2257                                n_barrier_cbs);
2258                         WARN_ON(1);
2259                         // Wait manually for the remaining callbacks
2260                         i = 0;
2261                         do {
2262                                 if (WARN_ON(i++ > HZ))
2263                                         i = INT_MIN;
2264                                 schedule_timeout_interruptible(1);
2265                                 cur_ops->cb_barrier();
2266                         } while (atomic_read(&barrier_cbs_invoked) !=
2267                                  n_barrier_cbs &&
2268                                  !torture_must_stop());
2269                         smp_mb(); // Can't trust ordering if broken.
2270                         if (!torture_must_stop())
2271                                 pr_err("Recovered: barrier_cbs_invoked = %d\n",
2272                                        atomic_read(&barrier_cbs_invoked));
2273                 } else {
2274                         n_barrier_successes++;
2275                 }
2276                 schedule_timeout_interruptible(HZ / 10);
2277         } while (!torture_must_stop());
2278         torture_kthread_stopping("rcu_torture_barrier");
2279         return 0;
2280 }
2281
2282 /* Initialize RCU barrier testing. */
2283 static int rcu_torture_barrier_init(void)
2284 {
2285         int i;
2286         int ret;
2287
2288         if (n_barrier_cbs <= 0)
2289                 return 0;
2290         if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
2291                 pr_alert("%s" TORTURE_FLAG
2292                          " Call or barrier ops missing for %s,\n",
2293                          torture_type, cur_ops->name);
2294                 pr_alert("%s" TORTURE_FLAG
2295                          " RCU barrier testing omitted from run.\n",
2296                          torture_type);
2297                 return 0;
2298         }
2299         atomic_set(&barrier_cbs_count, 0);
2300         atomic_set(&barrier_cbs_invoked, 0);
2301         barrier_cbs_tasks =
2302                 kcalloc(n_barrier_cbs, sizeof(barrier_cbs_tasks[0]),
2303                         GFP_KERNEL);
2304         barrier_cbs_wq =
2305                 kcalloc(n_barrier_cbs, sizeof(barrier_cbs_wq[0]), GFP_KERNEL);
2306         if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
2307                 return -ENOMEM;
2308         for (i = 0; i < n_barrier_cbs; i++) {
2309                 init_waitqueue_head(&barrier_cbs_wq[i]);
2310                 ret = torture_create_kthread(rcu_torture_barrier_cbs,
2311                                              (void *)(long)i,
2312                                              barrier_cbs_tasks[i]);
2313                 if (ret)
2314                         return ret;
2315         }
2316         return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task);
2317 }
2318
2319 /* Clean up after RCU barrier testing. */
2320 static void rcu_torture_barrier_cleanup(void)
2321 {
2322         int i;
2323
2324         torture_stop_kthread(rcu_torture_barrier, barrier_task);
2325         if (barrier_cbs_tasks != NULL) {
2326                 for (i = 0; i < n_barrier_cbs; i++)
2327                         torture_stop_kthread(rcu_torture_barrier_cbs,
2328                                              barrier_cbs_tasks[i]);
2329                 kfree(barrier_cbs_tasks);
2330                 barrier_cbs_tasks = NULL;
2331         }
2332         if (barrier_cbs_wq != NULL) {
2333                 kfree(barrier_cbs_wq);
2334                 barrier_cbs_wq = NULL;
2335         }
2336 }
2337
2338 static bool rcu_torture_can_boost(void)
2339 {
2340         static int boost_warn_once;
2341         int prio;
2342
2343         if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2)
2344                 return false;
2345
2346         prio = rcu_get_gp_kthreads_prio();
2347         if (!prio)
2348                 return false;
2349
2350         if (prio < 2) {
2351                 if (boost_warn_once  == 1)
2352                         return false;
2353
2354                 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);
2355                 boost_warn_once = 1;
2356                 return false;
2357         }
2358
2359         return true;
2360 }
2361
2362 static bool read_exit_child_stop;
2363 static bool read_exit_child_stopped;
2364 static wait_queue_head_t read_exit_wq;
2365
2366 // Child kthread which just does an rcutorture reader and exits.
2367 static int rcu_torture_read_exit_child(void *trsp_in)
2368 {
2369         struct torture_random_state *trsp = trsp_in;
2370
2371         set_user_nice(current, MAX_NICE);
2372         // Minimize time between reading and exiting.
2373         while (!kthread_should_stop())
2374                 schedule_timeout_uninterruptible(1);
2375         (void)rcu_torture_one_read(trsp);
2376         return 0;
2377 }
2378
2379 // Parent kthread which creates and destroys read-exit child kthreads.
2380 static int rcu_torture_read_exit(void *unused)
2381 {
2382         int count = 0;
2383         bool errexit = false;
2384         int i;
2385         struct task_struct *tsp;
2386         DEFINE_TORTURE_RANDOM(trs);
2387
2388         // Allocate and initialize.
2389         set_user_nice(current, MAX_NICE);
2390         VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of test");
2391
2392         // Each pass through this loop does one read-exit episode.
2393         do {
2394                 if (++count > read_exit_burst) {
2395                         VERBOSE_TOROUT_STRING("rcu_torture_read_exit: End of episode");
2396                         rcu_barrier(); // Wait for task_struct free, avoid OOM.
2397                         for (i = 0; i < read_exit_delay; i++) {
2398                                 schedule_timeout_uninterruptible(HZ);
2399                                 if (READ_ONCE(read_exit_child_stop))
2400                                         break;
2401                         }
2402                         if (!READ_ONCE(read_exit_child_stop))
2403                                 VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of episode");
2404                         count = 0;
2405                 }
2406                 if (READ_ONCE(read_exit_child_stop))
2407                         break;
2408                 // Spawn child.
2409                 tsp = kthread_run(rcu_torture_read_exit_child,
2410                                      &trs, "%s",
2411                                      "rcu_torture_read_exit_child");
2412                 if (IS_ERR(tsp)) {
2413                         VERBOSE_TOROUT_ERRSTRING("out of memory");
2414                         errexit = true;
2415                         tsp = NULL;
2416                         break;
2417                 }
2418                 cond_resched();
2419                 kthread_stop(tsp);
2420                 n_read_exits ++;
2421                 stutter_wait("rcu_torture_read_exit");
2422         } while (!errexit && !READ_ONCE(read_exit_child_stop));
2423
2424         // Clean up and exit.
2425         smp_store_release(&read_exit_child_stopped, true); // After reaping.
2426         smp_mb(); // Store before wakeup.
2427         wake_up(&read_exit_wq);
2428         while (!torture_must_stop())
2429                 schedule_timeout_uninterruptible(1);
2430         torture_kthread_stopping("rcu_torture_read_exit");
2431         return 0;
2432 }
2433
2434 static int rcu_torture_read_exit_init(void)
2435 {
2436         if (read_exit_burst <= 0)
2437                 return -EINVAL;
2438         init_waitqueue_head(&read_exit_wq);
2439         read_exit_child_stop = false;
2440         read_exit_child_stopped = false;
2441         return torture_create_kthread(rcu_torture_read_exit, NULL,
2442                                       read_exit_task);
2443 }
2444
2445 static void rcu_torture_read_exit_cleanup(void)
2446 {
2447         if (!read_exit_task)
2448                 return;
2449         WRITE_ONCE(read_exit_child_stop, true);
2450         smp_mb(); // Above write before wait.
2451         wait_event(read_exit_wq, smp_load_acquire(&read_exit_child_stopped));
2452         torture_stop_kthread(rcutorture_read_exit, read_exit_task);
2453 }
2454
2455 static enum cpuhp_state rcutor_hp;
2456
2457 static void
2458 rcu_torture_cleanup(void)
2459 {
2460         int firsttime;
2461         int flags = 0;
2462         unsigned long gp_seq = 0;
2463         int i;
2464
2465         if (torture_cleanup_begin()) {
2466                 if (cur_ops->cb_barrier != NULL)
2467                         cur_ops->cb_barrier();
2468                 return;
2469         }
2470         if (!cur_ops) {
2471                 torture_cleanup_end();
2472                 return;
2473         }
2474
2475         show_rcu_gp_kthreads();
2476         rcu_torture_read_exit_cleanup();
2477         rcu_torture_barrier_cleanup();
2478         rcu_torture_fwd_prog_cleanup();
2479         torture_stop_kthread(rcu_torture_stall, stall_task);
2480         torture_stop_kthread(rcu_torture_writer, writer_task);
2481
2482         if (reader_tasks) {
2483                 for (i = 0; i < nrealreaders; i++)
2484                         torture_stop_kthread(rcu_torture_reader,
2485                                              reader_tasks[i]);
2486                 kfree(reader_tasks);
2487         }
2488
2489         if (fakewriter_tasks) {
2490                 for (i = 0; i < nfakewriters; i++) {
2491                         torture_stop_kthread(rcu_torture_fakewriter,
2492                                              fakewriter_tasks[i]);
2493                 }
2494                 kfree(fakewriter_tasks);
2495                 fakewriter_tasks = NULL;
2496         }
2497
2498         rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
2499         srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
2500         pr_alert("%s:  End-test grace-period state: g%ld f%#x total-gps=%ld\n",
2501                  cur_ops->name, (long)gp_seq, flags,
2502                  rcutorture_seq_diff(gp_seq, start_gp_seq));
2503         torture_stop_kthread(rcu_torture_stats, stats_task);
2504         torture_stop_kthread(rcu_torture_fqs, fqs_task);
2505         if (rcu_torture_can_boost())
2506                 cpuhp_remove_state(rcutor_hp);
2507
2508         /*
2509          * Wait for all RCU callbacks to fire, then do torture-type-specific
2510          * cleanup operations.
2511          */
2512         if (cur_ops->cb_barrier != NULL)
2513                 cur_ops->cb_barrier();
2514         if (cur_ops->cleanup != NULL)
2515                 cur_ops->cleanup();
2516
2517         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
2518
2519         if (err_segs_recorded) {
2520                 pr_alert("Failure/close-call rcutorture reader segments:\n");
2521                 if (rt_read_nsegs == 0)
2522                         pr_alert("\t: No segments recorded!!!\n");
2523                 firsttime = 1;
2524                 for (i = 0; i < rt_read_nsegs; i++) {
2525                         pr_alert("\t%d: %#x ", i, err_segs[i].rt_readstate);
2526                         if (err_segs[i].rt_delay_jiffies != 0) {
2527                                 pr_cont("%s%ldjiffies", firsttime ? "" : "+",
2528                                         err_segs[i].rt_delay_jiffies);
2529                                 firsttime = 0;
2530                         }
2531                         if (err_segs[i].rt_delay_ms != 0) {
2532                                 pr_cont("%s%ldms", firsttime ? "" : "+",
2533                                         err_segs[i].rt_delay_ms);
2534                                 firsttime = 0;
2535                         }
2536                         if (err_segs[i].rt_delay_us != 0) {
2537                                 pr_cont("%s%ldus", firsttime ? "" : "+",
2538                                         err_segs[i].rt_delay_us);
2539                                 firsttime = 0;
2540                         }
2541                         pr_cont("%s\n",
2542                                 err_segs[i].rt_preempted ? "preempted" : "");
2543
2544                 }
2545         }
2546         if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
2547                 rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
2548         else if (torture_onoff_failures())
2549                 rcu_torture_print_module_parms(cur_ops,
2550                                                "End of test: RCU_HOTPLUG");
2551         else
2552                 rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
2553         torture_cleanup_end();
2554 }
2555
2556 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
2557 static void rcu_torture_leak_cb(struct rcu_head *rhp)
2558 {
2559 }
2560
2561 static void rcu_torture_err_cb(struct rcu_head *rhp)
2562 {
2563         /*
2564          * This -might- happen due to race conditions, but is unlikely.
2565          * The scenario that leads to this happening is that the
2566          * first of the pair of duplicate callbacks is queued,
2567          * someone else starts a grace period that includes that
2568          * callback, then the second of the pair must wait for the
2569          * next grace period.  Unlikely, but can happen.  If it
2570          * does happen, the debug-objects subsystem won't have splatted.
2571          */
2572         pr_alert("%s: duplicated callback was invoked.\n", KBUILD_MODNAME);
2573 }
2574 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2575
2576 /*
2577  * Verify that double-free causes debug-objects to complain, but only
2578  * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.  Otherwise, say that the test
2579  * cannot be carried out.
2580  */
2581 static void rcu_test_debug_objects(void)
2582 {
2583 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
2584         struct rcu_head rh1;
2585         struct rcu_head rh2;
2586
2587         init_rcu_head_on_stack(&rh1);
2588         init_rcu_head_on_stack(&rh2);
2589         pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME);
2590
2591         /* Try to queue the rh2 pair of callbacks for the same grace period. */
2592         preempt_disable(); /* Prevent preemption from interrupting test. */
2593         rcu_read_lock(); /* Make it impossible to finish a grace period. */
2594         call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */
2595         local_irq_disable(); /* Make it harder to start a new grace period. */
2596         call_rcu(&rh2, rcu_torture_leak_cb);
2597         call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
2598         local_irq_enable();
2599         rcu_read_unlock();
2600         preempt_enable();
2601
2602         /* Wait for them all to get done so we can safely return. */
2603         rcu_barrier();
2604         pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
2605         destroy_rcu_head_on_stack(&rh1);
2606         destroy_rcu_head_on_stack(&rh2);
2607 #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2608         pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
2609 #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2610 }
2611
2612 static void rcutorture_sync(void)
2613 {
2614         static unsigned long n;
2615
2616         if (cur_ops->sync && !(++n & 0xfff))
2617                 cur_ops->sync();
2618 }
2619
2620 static int __init
2621 rcu_torture_init(void)
2622 {
2623         long i;
2624         int cpu;
2625         int firsterr = 0;
2626         int flags = 0;
2627         unsigned long gp_seq = 0;
2628         static struct rcu_torture_ops *torture_ops[] = {
2629                 &rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
2630                 &busted_srcud_ops, &tasks_ops, &tasks_rude_ops,
2631                 &tasks_tracing_ops, &trivial_ops,
2632         };
2633
2634         if (!torture_init_begin(torture_type, verbose))
2635                 return -EBUSY;
2636
2637         /* Process args and tell the world that the torturer is on the job. */
2638         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
2639                 cur_ops = torture_ops[i];
2640                 if (strcmp(torture_type, cur_ops->name) == 0)
2641                         break;
2642         }
2643         if (i == ARRAY_SIZE(torture_ops)) {
2644                 pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
2645                          torture_type);
2646                 pr_alert("rcu-torture types:");
2647                 for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
2648                         pr_cont(" %s", torture_ops[i]->name);
2649                 pr_cont("\n");
2650                 WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
2651                 firsterr = -EINVAL;
2652                 cur_ops = NULL;
2653                 goto unwind;
2654         }
2655         if (cur_ops->fqs == NULL && fqs_duration != 0) {
2656                 pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
2657                 fqs_duration = 0;
2658         }
2659         if (cur_ops->init)
2660                 cur_ops->init();
2661
2662         if (nreaders >= 0) {
2663                 nrealreaders = nreaders;
2664         } else {
2665                 nrealreaders = num_online_cpus() - 2 - nreaders;
2666                 if (nrealreaders <= 0)
2667                         nrealreaders = 1;
2668         }
2669         rcu_torture_print_module_parms(cur_ops, "Start of test");
2670         rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
2671         srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
2672         start_gp_seq = gp_seq;
2673         pr_alert("%s:  Start-test grace-period state: g%ld f%#x\n",
2674                  cur_ops->name, (long)gp_seq, flags);
2675
2676         /* Set up the freelist. */
2677
2678         INIT_LIST_HEAD(&rcu_torture_freelist);
2679         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
2680                 rcu_tortures[i].rtort_mbtest = 0;
2681                 list_add_tail(&rcu_tortures[i].rtort_free,
2682                               &rcu_torture_freelist);
2683         }
2684
2685         /* Initialize the statistics so that each run gets its own numbers. */
2686
2687         rcu_torture_current = NULL;
2688         rcu_torture_current_version = 0;
2689         atomic_set(&n_rcu_torture_alloc, 0);
2690         atomic_set(&n_rcu_torture_alloc_fail, 0);
2691         atomic_set(&n_rcu_torture_free, 0);
2692         atomic_set(&n_rcu_torture_mberror, 0);
2693         atomic_set(&n_rcu_torture_error, 0);
2694         n_rcu_torture_barrier_error = 0;
2695         n_rcu_torture_boost_ktrerror = 0;
2696         n_rcu_torture_boost_rterror = 0;
2697         n_rcu_torture_boost_failure = 0;
2698         n_rcu_torture_boosts = 0;
2699         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
2700                 atomic_set(&rcu_torture_wcount[i], 0);
2701         for_each_possible_cpu(cpu) {
2702                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
2703                         per_cpu(rcu_torture_count, cpu)[i] = 0;
2704                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
2705                 }
2706         }
2707         err_segs_recorded = 0;
2708         rt_read_nsegs = 0;
2709
2710         /* Start up the kthreads. */
2711
2712         firsterr = torture_create_kthread(rcu_torture_writer, NULL,
2713                                           writer_task);
2714         if (firsterr)
2715                 goto unwind;
2716         if (nfakewriters > 0) {
2717                 fakewriter_tasks = kcalloc(nfakewriters,
2718                                            sizeof(fakewriter_tasks[0]),
2719                                            GFP_KERNEL);
2720                 if (fakewriter_tasks == NULL) {
2721                         VERBOSE_TOROUT_ERRSTRING("out of memory");
2722                         firsterr = -ENOMEM;
2723                         goto unwind;
2724                 }
2725         }
2726         for (i = 0; i < nfakewriters; i++) {
2727                 firsterr = torture_create_kthread(rcu_torture_fakewriter,
2728                                                   NULL, fakewriter_tasks[i]);
2729                 if (firsterr)
2730                         goto unwind;
2731         }
2732         reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
2733                                GFP_KERNEL);
2734         if (reader_tasks == NULL) {
2735                 VERBOSE_TOROUT_ERRSTRING("out of memory");
2736                 firsterr = -ENOMEM;
2737                 goto unwind;
2738         }
2739         for (i = 0; i < nrealreaders; i++) {
2740                 firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
2741                                                   reader_tasks[i]);
2742                 if (firsterr)
2743                         goto unwind;
2744         }
2745         if (stat_interval > 0) {
2746                 firsterr = torture_create_kthread(rcu_torture_stats, NULL,
2747                                                   stats_task);
2748                 if (firsterr)
2749                         goto unwind;
2750         }
2751         if (test_no_idle_hz && shuffle_interval > 0) {
2752                 firsterr = torture_shuffle_init(shuffle_interval * HZ);
2753                 if (firsterr)
2754                         goto unwind;
2755         }
2756         if (stutter < 0)
2757                 stutter = 0;
2758         if (stutter) {
2759                 int t;
2760
2761                 t = cur_ops->stall_dur ? cur_ops->stall_dur() : stutter * HZ;
2762                 firsterr = torture_stutter_init(stutter * HZ, t);
2763                 if (firsterr)
2764                         goto unwind;
2765         }
2766         if (fqs_duration < 0)
2767                 fqs_duration = 0;
2768         if (fqs_duration) {
2769                 /* Create the fqs thread */
2770                 firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
2771                                                   fqs_task);
2772                 if (firsterr)
2773                         goto unwind;
2774         }
2775         if (test_boost_interval < 1)
2776                 test_boost_interval = 1;
2777         if (test_boost_duration < 2)
2778                 test_boost_duration = 2;
2779         if (rcu_torture_can_boost()) {
2780
2781                 boost_starttime = jiffies + test_boost_interval * HZ;
2782
2783                 firsterr = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "RCU_TORTURE",
2784                                              rcutorture_booster_init,
2785                                              rcutorture_booster_cleanup);
2786                 if (firsterr < 0)
2787                         goto unwind;
2788                 rcutor_hp = firsterr;
2789         }
2790         shutdown_jiffies = jiffies + shutdown_secs * HZ;
2791         firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
2792         if (firsterr)
2793                 goto unwind;
2794         firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval,
2795                                       rcutorture_sync);
2796         if (firsterr)
2797                 goto unwind;
2798         firsterr = rcu_torture_stall_init();
2799         if (firsterr)
2800                 goto unwind;
2801         firsterr = rcu_torture_fwd_prog_init();
2802         if (firsterr)
2803                 goto unwind;
2804         firsterr = rcu_torture_barrier_init();
2805         if (firsterr)
2806                 goto unwind;
2807         firsterr = rcu_torture_read_exit_init();
2808         if (firsterr)
2809                 goto unwind;
2810         if (object_debug)
2811                 rcu_test_debug_objects();
2812         torture_init_end();
2813         return 0;
2814
2815 unwind:
2816         torture_init_end();
2817         rcu_torture_cleanup();
2818         return firsterr;
2819 }
2820
2821 module_init(rcu_torture_init);
2822 module_exit(rcu_torture_cleanup);