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 #include <linux/nmi.h>
  50
  51 #include "rcu.h"
  52
  53 MODULE_LICENSE("GPL");
  54 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
  55
  56 /* Bits for ->extendables field, extendables param, and related definitions. */
  57 #define RCUTORTURE_RDR_SHIFT     8      /* Put SRCU index in upper bits. */
  58 #define RCUTORTURE_RDR_MASK      ((1 << RCUTORTURE_RDR_SHIFT) - 1)
  59 #define RCUTORTURE_RDR_BH        0x01   /* Extend readers by disabling bh. */
  60 #define RCUTORTURE_RDR_IRQ       0x02   /*  ... disabling interrupts. */
  61 #define RCUTORTURE_RDR_PREEMPT   0x04   /*  ... disabling preemption. */
  62 #define RCUTORTURE_RDR_RBH       0x08   /*  ... rcu_read_lock_bh(). */
  63 #define RCUTORTURE_RDR_SCHED     0x10   /*  ... rcu_read_lock_sched(). */
  64 #define RCUTORTURE_RDR_RCU       0x20   /*  ... entering another RCU reader. */
  65 #define RCUTORTURE_RDR_NBITS     6      /* Number of bits defined above. */
  66 #define RCUTORTURE_MAX_EXTEND    \
  67         (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
  68          RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
  69 #define RCUTORTURE_RDR_MAX_LOOPS 0x7    /* Maximum reader extensions. */
  70                                         /* Must be power of two minus one. */
  71 #define RCUTORTURE_RDR_MAX_SEGS (RCUTORTURE_RDR_MAX_LOOPS + 3)
  72
  73 torture_param(int, extendables, RCUTORTURE_MAX_EXTEND,
  74               "Extend readers by disabling bh (1), irqs (2), or preempt (4)");
  75 torture_param(int, fqs_duration, 0,
  76               "Duration of fqs bursts (us), 0 to disable");
  77 torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
  78 torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
  79 torture_param(bool, fwd_progress, 1, "Test grace-period forward progress");
  80 torture_param(int, fwd_progress_div, 4, "Fraction of CPU stall to wait");
  81 torture_param(int, fwd_progress_holdoff, 60,
  82               "Time between forward-progress tests (s)");
  83 torture_param(bool, fwd_progress_need_resched, 1,
  84               "Hide cond_resched() behind need_resched()");
  85 torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
  86 torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
  87 torture_param(bool, gp_normal, false,
  88              "Use normal (non-expedited) GP wait primitives");
  89 torture_param(bool, gp_poll, false, "Use polling GP wait primitives");
  90 torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
  91 torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
  92 torture_param(int, leakpointer, 0, "Leak pointer dereferences from readers");
  93 torture_param(int, n_barrier_cbs, 0,
  94              "# of callbacks/kthreads for barrier testing");
  95 torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
  96 torture_param(int, nreaders, -1, "Number of RCU reader threads");
  97 torture_param(int, object_debug, 0,
  98              "Enable debug-object double call_rcu() testing");
  99 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
 100 torture_param(int, onoff_interval, 0,
 101              "Time between CPU hotplugs (jiffies), 0=disable");
 102 torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disable");
 103 torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
 104 torture_param(int, read_exit_delay, 13,
 105               "Delay between read-then-exit episodes (s)");
 106 torture_param(int, read_exit_burst, 16,
 107               "# of read-then-exit bursts per episode, zero to disable");
 108 torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
 109 torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
 110 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
 111 torture_param(int, stall_cpu_holdoff, 10,
 112              "Time to wait before starting stall (s).");
 113 torture_param(bool, stall_no_softlockup, false,
 114              "Avoid softlockup warning during cpu stall.");
 115 torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
 116 torture_param(int, stall_cpu_block, 0, "Sleep while stalling.");
 117 torture_param(int, stall_gp_kthread, 0,
 118               "Grace-period kthread stall duration (s).");
 119 torture_param(int, stat_interval, 60,
 120              "Number of seconds between stats printk()s");
 121 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
 122 torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
 123 torture_param(int, test_boost_duration, 4,
 124              "Duration of each boost test, seconds.");
 125 torture_param(int, test_boost_interval, 7,
 126              "Interval between boost tests, seconds.");
 127 torture_param(bool, test_no_idle_hz, true,
 128              "Test support for tickless idle CPUs");
 129 torture_param(int, verbose, 1,
 130              "Enable verbose debugging printk()s");
 131
 132 static char *torture_type = "rcu";
 133 module_param(torture_type, charp, 0444);
 134 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");
 135
 136 static int nrealnocbers;
 137 static int nrealreaders;
 138 static struct task_struct *writer_task;
 139 static struct task_struct **fakewriter_tasks;
 140 static struct task_struct **reader_tasks;
 141 static struct task_struct **nocb_tasks;
 142 static struct task_struct *stats_task;
 143 static struct task_struct *fqs_task;
 144 static struct task_struct *boost_tasks[NR_CPUS];
 145 static struct task_struct *stall_task;
 146 static struct task_struct *fwd_prog_task;
 147 static struct task_struct **barrier_cbs_tasks;
 148 static struct task_struct *barrier_task;
 149 static struct task_struct *read_exit_task;
 150
 151 #define RCU_TORTURE_PIPE_LEN 10
 152
 153 // Mailbox-like structure to check RCU global memory ordering.
 154 struct rcu_torture_reader_check {
 155         unsigned long rtc_myloops;
 156         int rtc_chkrdr;
 157         unsigned long rtc_chkloops;
 158         int rtc_ready;
 159         struct rcu_torture_reader_check *rtc_assigner;
 160 } ____cacheline_internodealigned_in_smp;
 161
 162 // Update-side data structure used to check RCU readers.
 163 struct rcu_torture {
 164         struct rcu_head rtort_rcu;
 165         int rtort_pipe_count;
 166         struct list_head rtort_free;
 167         int rtort_mbtest;
 168         struct rcu_torture_reader_check *rtort_chkp;
 169 };
 170
 171 static LIST_HEAD(rcu_torture_freelist);
 172 static struct rcu_torture __rcu *rcu_torture_current;
 173 static unsigned long rcu_torture_current_version;
 174 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 175 static DEFINE_SPINLOCK(rcu_torture_lock);
 176 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
 177 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
 178 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 179 static struct rcu_torture_reader_check *rcu_torture_reader_mbchk;
 180 static atomic_t n_rcu_torture_alloc;
 181 static atomic_t n_rcu_torture_alloc_fail;
 182 static atomic_t n_rcu_torture_free;
 183 static atomic_t n_rcu_torture_mberror;
 184 static atomic_t n_rcu_torture_mbchk_fail;
 185 static atomic_t n_rcu_torture_mbchk_tries;
 186 static atomic_t n_rcu_torture_error;
 187 static long n_rcu_torture_barrier_error;
 188 static long n_rcu_torture_boost_ktrerror;
 189 static long n_rcu_torture_boost_rterror;
 190 static long n_rcu_torture_boost_failure;
 191 static long n_rcu_torture_boosts;
 192 static atomic_long_t n_rcu_torture_timers;
 193 static long n_barrier_attempts;
 194 static long n_barrier_successes; /* did rcu_barrier test succeed? */
 195 static unsigned long n_read_exits;
 196 static struct list_head rcu_torture_removed;
 197 static unsigned long shutdown_jiffies;
 198 static unsigned long start_gp_seq;
 199 static atomic_long_t n_nocb_offload;
 200 static atomic_long_t n_nocb_deoffload;
 201
 202 static int rcu_torture_writer_state;
 203 #define RTWS_FIXED_DELAY        0
 204 #define RTWS_DELAY              1
 205 #define RTWS_REPLACE            2
 206 #define RTWS_DEF_FREE           3
 207 #define RTWS_EXP_SYNC           4
 208 #define RTWS_COND_GET           5
 209 #define RTWS_COND_SYNC          6
 210 #define RTWS_POLL_GET           7
 211 #define RTWS_POLL_WAIT          8
 212 #define RTWS_SYNC               9
 213 #define RTWS_STUTTER            10
 214 #define RTWS_STOPPING           11
 215 static const char * const rcu_torture_writer_state_names[] = {
 216         "RTWS_FIXED_DELAY",
 217         "RTWS_DELAY",
 218         "RTWS_REPLACE",
 219         "RTWS_DEF_FREE",
 220         "RTWS_EXP_SYNC",
 221         "RTWS_COND_GET",
 222         "RTWS_COND_SYNC",
 223         "RTWS_POLL_GET",
 224         "RTWS_POLL_WAIT",
 225         "RTWS_SYNC",
 226         "RTWS_STUTTER",
 227         "RTWS_STOPPING",
 228 };
 229
 230 /* Record reader segment types and duration for first failing read. */
 231 struct rt_read_seg {
 232         int rt_readstate;
 233         unsigned long rt_delay_jiffies;
 234         unsigned long rt_delay_ms;
 235         unsigned long rt_delay_us;
 236         bool rt_preempted;
 237 };
 238 static int err_segs_recorded;
 239 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
 240 static int rt_read_nsegs;
 241
 242 static const char *rcu_torture_writer_state_getname(void)
 243 {
 244         unsigned int i = READ_ONCE(rcu_torture_writer_state);
 245
 246         if (i >= ARRAY_SIZE(rcu_torture_writer_state_names))
 247                 return "???";
 248         return rcu_torture_writer_state_names[i];
 249 }
 250
 251 #ifdef CONFIG_RCU_TRACE
 252 static u64 notrace rcu_trace_clock_local(void)
 253 {
 254         u64 ts = trace_clock_local();
 255
 256         (void)do_div(ts, NSEC_PER_USEC);
 257         return ts;
 258 }
 259 #else /* #ifdef CONFIG_RCU_TRACE */
 260 static u64 notrace rcu_trace_clock_local(void)
 261 {
 262         return 0ULL;
 263 }
 264 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 265
 266 /*
 267  * Stop aggressive CPU-hog tests a bit before the end of the test in order
 268  * to avoid interfering with test shutdown.
 269  */
 270 static bool shutdown_time_arrived(void)
 271 {
 272         return shutdown_secs && time_after(jiffies, shutdown_jiffies - 30 * HZ);
 273 }
 274
 275 static unsigned long boost_starttime;   /* jiffies of next boost test start. */
 276 static DEFINE_MUTEX(boost_mutex);       /* protect setting boost_starttime */
 277                                         /*  and boost task create/destroy. */
 278 static atomic_t barrier_cbs_count;      /* Barrier callbacks registered. */
 279 static bool barrier_phase;              /* Test phase. */
 280 static atomic_t barrier_cbs_invoked;    /* Barrier callbacks invoked. */
 281 static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
 282 static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
 283
 284 static bool rcu_fwd_cb_nodelay;         /* Short rcu_torture_delay() delays. */
 285
 286 /*
 287  * Allocate an element from the rcu_tortures pool.
 288  */
 289 static struct rcu_torture *
 290 rcu_torture_alloc(void)
 291 {
 292         struct list_head *p;
 293
 294         spin_lock_bh(&rcu_torture_lock);
 295         if (list_empty(&rcu_torture_freelist)) {
 296                 atomic_inc(&n_rcu_torture_alloc_fail);
 297                 spin_unlock_bh(&rcu_torture_lock);
 298                 return NULL;
 299         }
 300         atomic_inc(&n_rcu_torture_alloc);
 301         p = rcu_torture_freelist.next;
 302         list_del_init(p);
 303         spin_unlock_bh(&rcu_torture_lock);
 304         return container_of(p, struct rcu_torture, rtort_free);
 305 }
 306
 307 /*
 308  * Free an element to the rcu_tortures pool.
 309  */
 310 static void
 311 rcu_torture_free(struct rcu_torture *p)
 312 {
 313         atomic_inc(&n_rcu_torture_free);
 314         spin_lock_bh(&rcu_torture_lock);
 315         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 316         spin_unlock_bh(&rcu_torture_lock);
 317 }
 318
 319 /*
 320  * Operations vector for selecting different types of tests.
 321  */
 322
 323 struct rcu_torture_ops {
 324         int ttype;
 325         void (*init)(void);
 326         void (*cleanup)(void);
 327         int (*readlock)(void);
 328         void (*read_delay)(struct torture_random_state *rrsp,
 329                            struct rt_read_seg *rtrsp);
 330         void (*readunlock)(int idx);
 331         int (*readlock_held)(void);
 332         unsigned long (*get_gp_seq)(void);
 333         unsigned long (*gp_diff)(unsigned long new, unsigned long old);
 334         void (*deferred_free)(struct rcu_torture *p);
 335         void (*sync)(void);
 336         void (*exp_sync)(void);
 337         unsigned long (*get_gp_state)(void);
 338         unsigned long (*start_gp_poll)(void);
 339         bool (*poll_gp_state)(unsigned long oldstate);
 340         void (*cond_sync)(unsigned long oldstate);
 341         call_rcu_func_t call;
 342         void (*cb_barrier)(void);
 343         void (*fqs)(void);
 344         void (*stats)(void);
 345         void (*gp_kthread_dbg)(void);
 346         bool (*check_boost_failed)(unsigned long gp_state, int *cpup);
 347         int (*stall_dur)(void);
 348         int irq_capable;
 349         int can_boost;
 350         int extendables;
 351         int slow_gps;
 352         const char *name;
 353 };
 354
 355 static struct rcu_torture_ops *cur_ops;
 356
 357 /*
 358  * Definitions for rcu torture testing.
 359  */
 360
 361 static int torture_readlock_not_held(void)
 362 {
 363         return rcu_read_lock_bh_held() || rcu_read_lock_sched_held();
 364 }
 365
 366 static int rcu_torture_read_lock(void) __acquires(RCU)
 367 {
 368         rcu_read_lock();
 369         return 0;
 370 }
 371
 372 static void
 373 rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 374 {
 375         unsigned long started;
 376         unsigned long completed;
 377         const unsigned long shortdelay_us = 200;
 378         unsigned long longdelay_ms = 300;
 379         unsigned long long ts;
 380
 381         /* We want a short delay sometimes to make a reader delay the grace
 382          * period, and we want a long delay occasionally to trigger
 383          * force_quiescent_state. */
 384
 385         if (!READ_ONCE(rcu_fwd_cb_nodelay) &&
 386             !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
 387                 started = cur_ops->get_gp_seq();
 388                 ts = rcu_trace_clock_local();
 389                 if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK))
 390                         longdelay_ms = 5; /* Avoid triggering BH limits. */
 391                 mdelay(longdelay_ms);
 392                 rtrsp->rt_delay_ms = longdelay_ms;
 393                 completed = cur_ops->get_gp_seq();
 394                 do_trace_rcu_torture_read(cur_ops->name, NULL, ts,
 395                                           started, completed);
 396         }
 397         if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) {
 398                 udelay(shortdelay_us);
 399                 rtrsp->rt_delay_us = shortdelay_us;
 400         }
 401         if (!preempt_count() &&
 402             !(torture_random(rrsp) % (nrealreaders * 500))) {
 403                 torture_preempt_schedule();  /* QS only if preemptible. */
 404                 rtrsp->rt_preempted = true;
 405         }
 406 }
 407
 408 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 409 {
 410         rcu_read_unlock();
 411 }
 412
 413 /*
 414  * Update callback in the pipe.  This should be invoked after a grace period.
 415  */
 416 static bool
 417 rcu_torture_pipe_update_one(struct rcu_torture *rp)
 418 {
 419         int i;
 420         struct rcu_torture_reader_check *rtrcp = READ_ONCE(rp->rtort_chkp);
 421
 422         if (rtrcp) {
 423                 WRITE_ONCE(rp->rtort_chkp, NULL);
 424                 smp_store_release(&rtrcp->rtc_ready, 1); // Pair with smp_load_acquire().
 425         }
 426         i = READ_ONCE(rp->rtort_pipe_count);
 427         if (i > RCU_TORTURE_PIPE_LEN)
 428                 i = RCU_TORTURE_PIPE_LEN;
 429         atomic_inc(&rcu_torture_wcount[i]);
 430         WRITE_ONCE(rp->rtort_pipe_count, i + 1);
 431         if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 432                 rp->rtort_mbtest = 0;
 433                 return true;
 434         }
 435         return false;
 436 }
 437
 438 /*
 439  * Update all callbacks in the pipe.  Suitable for synchronous grace-period
 440  * primitives.
 441  */
 442 static void
 443 rcu_torture_pipe_update(struct rcu_torture *old_rp)
 444 {
 445         struct rcu_torture *rp;
 446         struct rcu_torture *rp1;
 447
 448         if (old_rp)
 449                 list_add(&old_rp->rtort_free, &rcu_torture_removed);
 450         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 451                 if (rcu_torture_pipe_update_one(rp)) {
 452                         list_del(&rp->rtort_free);
 453                         rcu_torture_free(rp);
 454                 }
 455         }
 456 }
 457
 458 static void
 459 rcu_torture_cb(struct rcu_head *p)
 460 {
 461         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 462
 463         if (torture_must_stop_irq()) {
 464                 /* Test is ending, just drop callbacks on the floor. */
 465                 /* The next initialization will pick up the pieces. */
 466                 return;
 467         }
 468         if (rcu_torture_pipe_update_one(rp))
 469                 rcu_torture_free(rp);
 470         else
 471                 cur_ops->deferred_free(rp);
 472 }
 473
 474 static unsigned long rcu_no_completed(void)
 475 {
 476         return 0;
 477 }
 478
 479 static void rcu_torture_deferred_free(struct rcu_torture *p)
 480 {
 481         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 482 }
 483
 484 static void rcu_sync_torture_init(void)
 485 {
 486         INIT_LIST_HEAD(&rcu_torture_removed);
 487 }
 488
 489 static struct rcu_torture_ops rcu_ops = {
 490         .ttype                  = RCU_FLAVOR,
 491         .init                   = rcu_sync_torture_init,
 492         .readlock               = rcu_torture_read_lock,
 493         .read_delay             = rcu_read_delay,
 494         .readunlock             = rcu_torture_read_unlock,
 495         .readlock_held          = torture_readlock_not_held,
 496         .get_gp_seq             = rcu_get_gp_seq,
 497         .gp_diff                = rcu_seq_diff,
 498         .deferred_free          = rcu_torture_deferred_free,
 499         .sync                   = synchronize_rcu,
 500         .exp_sync               = synchronize_rcu_expedited,
 501         .get_gp_state           = get_state_synchronize_rcu,
 502         .start_gp_poll          = start_poll_synchronize_rcu,
 503         .poll_gp_state          = poll_state_synchronize_rcu,
 504         .cond_sync              = cond_synchronize_rcu,
 505         .call                   = call_rcu,
 506         .cb_barrier             = rcu_barrier,
 507         .fqs                    = rcu_force_quiescent_state,
 508         .stats                  = NULL,
 509         .gp_kthread_dbg         = show_rcu_gp_kthreads,
 510         .check_boost_failed     = rcu_check_boost_fail,
 511         .stall_dur              = rcu_jiffies_till_stall_check,
 512         .irq_capable            = 1,
 513         .can_boost              = IS_ENABLED(CONFIG_RCU_BOOST),
 514         .extendables            = RCUTORTURE_MAX_EXTEND,
 515         .name                   = "rcu"
 516 };
 517
 518 /*
 519  * Don't even think about trying any of these in real life!!!
 520  * The names includes "busted", and they really means it!
 521  * The only purpose of these functions is to provide a buggy RCU
 522  * implementation to make sure that rcutorture correctly emits
 523  * buggy-RCU error messages.
 524  */
 525 static void rcu_busted_torture_deferred_free(struct rcu_torture *p)
 526 {
 527         /* This is a deliberate bug for testing purposes only! */
 528         rcu_torture_cb(&p->rtort_rcu);
 529 }
 530
 531 static void synchronize_rcu_busted(void)
 532 {
 533         /* This is a deliberate bug for testing purposes only! */
 534 }
 535
 536 static void
 537 call_rcu_busted(struct rcu_head *head, rcu_callback_t func)
 538 {
 539         /* This is a deliberate bug for testing purposes only! */
 540         func(head);
 541 }
 542
 543 static struct rcu_torture_ops rcu_busted_ops = {
 544         .ttype          = INVALID_RCU_FLAVOR,
 545         .init           = rcu_sync_torture_init,
 546         .readlock       = rcu_torture_read_lock,
 547         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 548         .readunlock     = rcu_torture_read_unlock,
 549         .readlock_held  = torture_readlock_not_held,
 550         .get_gp_seq     = rcu_no_completed,
 551         .deferred_free  = rcu_busted_torture_deferred_free,
 552         .sync           = synchronize_rcu_busted,
 553         .exp_sync       = synchronize_rcu_busted,
 554         .call           = call_rcu_busted,
 555         .cb_barrier     = NULL,
 556         .fqs            = NULL,
 557         .stats          = NULL,
 558         .irq_capable    = 1,
 559         .name           = "busted"
 560 };
 561
 562 /*
 563  * Definitions for srcu torture testing.
 564  */
 565
 566 DEFINE_STATIC_SRCU(srcu_ctl);
 567 static struct srcu_struct srcu_ctld;
 568 static struct srcu_struct *srcu_ctlp = &srcu_ctl;
 569
 570 static int srcu_torture_read_lock(void) __acquires(srcu_ctlp)
 571 {
 572         return srcu_read_lock(srcu_ctlp);
 573 }
 574
 575 static void
 576 srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 577 {
 578         long delay;
 579         const long uspertick = 1000000 / HZ;
 580         const long longdelay = 10;
 581
 582         /* We want there to be long-running readers, but not all the time. */
 583
 584         delay = torture_random(rrsp) %
 585                 (nrealreaders * 2 * longdelay * uspertick);
 586         if (!delay && in_task()) {
 587                 schedule_timeout_interruptible(longdelay);
 588                 rtrsp->rt_delay_jiffies = longdelay;
 589         } else {
 590                 rcu_read_delay(rrsp, rtrsp);
 591         }
 592 }
 593
 594 static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp)
 595 {
 596         srcu_read_unlock(srcu_ctlp, idx);
 597 }
 598
 599 static int torture_srcu_read_lock_held(void)
 600 {
 601         return srcu_read_lock_held(srcu_ctlp);
 602 }
 603
 604 static unsigned long srcu_torture_completed(void)
 605 {
 606         return srcu_batches_completed(srcu_ctlp);
 607 }
 608
 609 static void srcu_torture_deferred_free(struct rcu_torture *rp)
 610 {
 611         call_srcu(srcu_ctlp, &rp->rtort_rcu, rcu_torture_cb);
 612 }
 613
 614 static void srcu_torture_synchronize(void)
 615 {
 616         synchronize_srcu(srcu_ctlp);
 617 }
 618
 619 static unsigned long srcu_torture_get_gp_state(void)
 620 {
 621         return get_state_synchronize_srcu(srcu_ctlp);
 622 }
 623
 624 static unsigned long srcu_torture_start_gp_poll(void)
 625 {
 626         return start_poll_synchronize_srcu(srcu_ctlp);
 627 }
 628
 629 static bool srcu_torture_poll_gp_state(unsigned long oldstate)
 630 {
 631         return poll_state_synchronize_srcu(srcu_ctlp, oldstate);
 632 }
 633
 634 static void srcu_torture_call(struct rcu_head *head,
 635                               rcu_callback_t func)
 636 {
 637         call_srcu(srcu_ctlp, head, func);
 638 }
 639
 640 static void srcu_torture_barrier(void)
 641 {
 642         srcu_barrier(srcu_ctlp);
 643 }
 644
 645 static void srcu_torture_stats(void)
 646 {
 647         srcu_torture_stats_print(srcu_ctlp, torture_type, TORTURE_FLAG);
 648 }
 649
 650 static void srcu_torture_synchronize_expedited(void)
 651 {
 652         synchronize_srcu_expedited(srcu_ctlp);
 653 }
 654
 655 static struct rcu_torture_ops srcu_ops = {
 656         .ttype          = SRCU_FLAVOR,
 657         .init           = rcu_sync_torture_init,
 658         .readlock       = srcu_torture_read_lock,
 659         .read_delay     = srcu_read_delay,
 660         .readunlock     = srcu_torture_read_unlock,
 661         .readlock_held  = torture_srcu_read_lock_held,
 662         .get_gp_seq     = srcu_torture_completed,
 663         .deferred_free  = srcu_torture_deferred_free,
 664         .sync           = srcu_torture_synchronize,
 665         .exp_sync       = srcu_torture_synchronize_expedited,
 666         .get_gp_state   = srcu_torture_get_gp_state,
 667         .start_gp_poll  = srcu_torture_start_gp_poll,
 668         .poll_gp_state  = srcu_torture_poll_gp_state,
 669         .call           = srcu_torture_call,
 670         .cb_barrier     = srcu_torture_barrier,
 671         .stats          = srcu_torture_stats,
 672         .irq_capable    = 1,
 673         .name           = "srcu"
 674 };
 675
 676 static void srcu_torture_init(void)
 677 {
 678         rcu_sync_torture_init();
 679         WARN_ON(init_srcu_struct(&srcu_ctld));
 680         srcu_ctlp = &srcu_ctld;
 681 }
 682
 683 static void srcu_torture_cleanup(void)
 684 {
 685         cleanup_srcu_struct(&srcu_ctld);
 686         srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
 687 }
 688
 689 /* As above, but dynamically allocated. */
 690 static struct rcu_torture_ops srcud_ops = {
 691         .ttype          = SRCU_FLAVOR,
 692         .init           = srcu_torture_init,
 693         .cleanup        = srcu_torture_cleanup,
 694         .readlock       = srcu_torture_read_lock,
 695         .read_delay     = srcu_read_delay,
 696         .readunlock     = srcu_torture_read_unlock,
 697         .readlock_held  = torture_srcu_read_lock_held,
 698         .get_gp_seq     = srcu_torture_completed,
 699         .deferred_free  = srcu_torture_deferred_free,
 700         .sync           = srcu_torture_synchronize,
 701         .exp_sync       = srcu_torture_synchronize_expedited,
 702         .call           = srcu_torture_call,
 703         .cb_barrier     = srcu_torture_barrier,
 704         .stats          = srcu_torture_stats,
 705         .irq_capable    = 1,
 706         .name           = "srcud"
 707 };
 708
 709 /* As above, but broken due to inappropriate reader extension. */
 710 static struct rcu_torture_ops busted_srcud_ops = {
 711         .ttype          = SRCU_FLAVOR,
 712         .init           = srcu_torture_init,
 713         .cleanup        = srcu_torture_cleanup,
 714         .readlock       = srcu_torture_read_lock,
 715         .read_delay     = rcu_read_delay,
 716         .readunlock     = srcu_torture_read_unlock,
 717         .readlock_held  = torture_srcu_read_lock_held,
 718         .get_gp_seq     = srcu_torture_completed,
 719         .deferred_free  = srcu_torture_deferred_free,
 720         .sync           = srcu_torture_synchronize,
 721         .exp_sync       = srcu_torture_synchronize_expedited,
 722         .call           = srcu_torture_call,
 723         .cb_barrier     = srcu_torture_barrier,
 724         .stats          = srcu_torture_stats,
 725         .irq_capable    = 1,
 726         .extendables    = RCUTORTURE_MAX_EXTEND,
 727         .name           = "busted_srcud"
 728 };
 729
 730 /*
 731  * Definitions for RCU-tasks torture testing.
 732  */
 733
 734 static int tasks_torture_read_lock(void)
 735 {
 736         return 0;
 737 }
 738
 739 static void tasks_torture_read_unlock(int idx)
 740 {
 741 }
 742
 743 static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
 744 {
 745         call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
 746 }
 747
 748 static void synchronize_rcu_mult_test(void)
 749 {
 750         synchronize_rcu_mult(call_rcu_tasks, call_rcu);
 751 }
 752
 753 static struct rcu_torture_ops tasks_ops = {
 754         .ttype          = RCU_TASKS_FLAVOR,
 755         .init           = rcu_sync_torture_init,
 756         .readlock       = tasks_torture_read_lock,
 757         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 758         .readunlock     = tasks_torture_read_unlock,
 759         .get_gp_seq     = rcu_no_completed,
 760         .deferred_free  = rcu_tasks_torture_deferred_free,
 761         .sync           = synchronize_rcu_tasks,
 762         .exp_sync       = synchronize_rcu_mult_test,
 763         .call           = call_rcu_tasks,
 764         .cb_barrier     = rcu_barrier_tasks,
 765         .gp_kthread_dbg = show_rcu_tasks_classic_gp_kthread,
 766         .fqs            = NULL,
 767         .stats          = NULL,
 768         .irq_capable    = 1,
 769         .slow_gps       = 1,
 770         .name           = "tasks"
 771 };
 772
 773 /*
 774  * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
 775  * This implementation does not necessarily work well with CPU hotplug.
 776  */
 777
 778 static void synchronize_rcu_trivial(void)
 779 {
 780         int cpu;
 781
 782         for_each_online_cpu(cpu) {
 783                 rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
 784                 WARN_ON_ONCE(raw_smp_processor_id() != cpu);
 785         }
 786 }
 787
 788 static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
 789 {
 790         preempt_disable();
 791         return 0;
 792 }
 793
 794 static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
 795 {
 796         preempt_enable();
 797 }
 798
 799 static struct rcu_torture_ops trivial_ops = {
 800         .ttype          = RCU_TRIVIAL_FLAVOR,
 801         .init           = rcu_sync_torture_init,
 802         .readlock       = rcu_torture_read_lock_trivial,
 803         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 804         .readunlock     = rcu_torture_read_unlock_trivial,
 805         .readlock_held  = torture_readlock_not_held,
 806         .get_gp_seq     = rcu_no_completed,
 807         .sync           = synchronize_rcu_trivial,
 808         .exp_sync       = synchronize_rcu_trivial,
 809         .fqs            = NULL,
 810         .stats          = NULL,
 811         .irq_capable    = 1,
 812         .name           = "trivial"
 813 };
 814
 815 /*
 816  * Definitions for rude RCU-tasks torture testing.
 817  */
 818
 819 static void rcu_tasks_rude_torture_deferred_free(struct rcu_torture *p)
 820 {
 821         call_rcu_tasks_rude(&p->rtort_rcu, rcu_torture_cb);
 822 }
 823
 824 static struct rcu_torture_ops tasks_rude_ops = {
 825         .ttype          = RCU_TASKS_RUDE_FLAVOR,
 826         .init           = rcu_sync_torture_init,
 827         .readlock       = rcu_torture_read_lock_trivial,
 828         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 829         .readunlock     = rcu_torture_read_unlock_trivial,
 830         .get_gp_seq     = rcu_no_completed,
 831         .deferred_free  = rcu_tasks_rude_torture_deferred_free,
 832         .sync           = synchronize_rcu_tasks_rude,
 833         .exp_sync       = synchronize_rcu_tasks_rude,
 834         .call           = call_rcu_tasks_rude,
 835         .cb_barrier     = rcu_barrier_tasks_rude,
 836         .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread,
 837         .fqs            = NULL,
 838         .stats          = NULL,
 839         .irq_capable    = 1,
 840         .name           = "tasks-rude"
 841 };
 842
 843 /*
 844  * Definitions for tracing RCU-tasks torture testing.
 845  */
 846
 847 static int tasks_tracing_torture_read_lock(void)
 848 {
 849         rcu_read_lock_trace();
 850         return 0;
 851 }
 852
 853 static void tasks_tracing_torture_read_unlock(int idx)
 854 {
 855         rcu_read_unlock_trace();
 856 }
 857
 858 static void rcu_tasks_tracing_torture_deferred_free(struct rcu_torture *p)
 859 {
 860         call_rcu_tasks_trace(&p->rtort_rcu, rcu_torture_cb);
 861 }
 862
 863 static struct rcu_torture_ops tasks_tracing_ops = {
 864         .ttype          = RCU_TASKS_TRACING_FLAVOR,
 865         .init           = rcu_sync_torture_init,
 866         .readlock       = tasks_tracing_torture_read_lock,
 867         .read_delay     = srcu_read_delay,  /* just reuse srcu's version. */
 868         .readunlock     = tasks_tracing_torture_read_unlock,
 869         .readlock_held  = rcu_read_lock_trace_held,
 870         .get_gp_seq     = rcu_no_completed,
 871         .deferred_free  = rcu_tasks_tracing_torture_deferred_free,
 872         .sync           = synchronize_rcu_tasks_trace,
 873         .exp_sync       = synchronize_rcu_tasks_trace,
 874         .call           = call_rcu_tasks_trace,
 875         .cb_barrier     = rcu_barrier_tasks_trace,
 876         .gp_kthread_dbg = show_rcu_tasks_trace_gp_kthread,
 877         .fqs            = NULL,
 878         .stats          = NULL,
 879         .irq_capable    = 1,
 880         .slow_gps       = 1,
 881         .name           = "tasks-tracing"
 882 };
 883
 884 static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
 885 {
 886         if (!cur_ops->gp_diff)
 887                 return new - old;
 888         return cur_ops->gp_diff(new, old);
 889 }
 890
 891 /*
 892  * RCU torture priority-boost testing.  Runs one real-time thread per
 893  * CPU for moderate bursts, repeatedly starting grace periods and waiting
 894  * for them to complete.  If a given grace period takes too long, we assume
 895  * that priority inversion has occurred.
 896  */
 897
 898 static int old_rt_runtime = -1;
 899
 900 static void rcu_torture_disable_rt_throttle(void)
 901 {
 902         /*
 903          * Disable RT throttling so that rcutorture's boost threads don't get
 904          * throttled. Only possible if rcutorture is built-in otherwise the
 905          * user should manually do this by setting the sched_rt_period_us and
 906          * sched_rt_runtime sysctls.
 907          */
 908         if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime != -1)
 909                 return;
 910
 911         old_rt_runtime = sysctl_sched_rt_runtime;
 912         sysctl_sched_rt_runtime = -1;
 913 }
 914
 915 static void rcu_torture_enable_rt_throttle(void)
 916 {
 917         if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime == -1)
 918                 return;
 919
 920         sysctl_sched_rt_runtime = old_rt_runtime;
 921         old_rt_runtime = -1;
 922 }
 923
 924 static bool rcu_torture_boost_failed(unsigned long gp_state, unsigned long *start)
 925 {
 926         int cpu;
 927         static int dbg_done;
 928         unsigned long end = jiffies;
 929         bool gp_done;
 930         unsigned long j;
 931         static unsigned long last_persist;
 932         unsigned long lp;
 933         unsigned long mininterval = test_boost_duration * HZ - HZ / 2;
 934
 935         if (end - *start > mininterval) {
 936                 // Recheck after checking time to avoid false positives.
 937                 smp_mb(); // Time check before grace-period check.
 938                 if (cur_ops->poll_gp_state(gp_state))
 939                         return false; // passed, though perhaps just barely
 940                 if (cur_ops->check_boost_failed && !cur_ops->check_boost_failed(gp_state, &cpu)) {
 941                         // At most one persisted message per boost test.
 942                         j = jiffies;
 943                         lp = READ_ONCE(last_persist);
 944                         if (time_after(j, lp + mininterval) && cmpxchg(&last_persist, lp, j) == lp)
 945                                 pr_info("Boost inversion persisted: No QS from CPU %d\n", cpu);
 946                         return false; // passed on a technicality
 947                 }
 948                 VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");
 949                 n_rcu_torture_boost_failure++;
 950                 if (!xchg(&dbg_done, 1) && cur_ops->gp_kthread_dbg) {
 951                         pr_info("Boost inversion thread ->rt_priority %u gp_state %lu jiffies %lu\n",
 952                                 current->rt_priority, gp_state, end - *start);
 953                         cur_ops->gp_kthread_dbg();
 954                         // Recheck after print to flag grace period ending during splat.
 955                         gp_done = cur_ops->poll_gp_state(gp_state);
 956                         pr_info("Boost inversion: GP %lu %s.\n", gp_state,
 957                                 gp_done ? "ended already" : "still pending");
 958
 959                 }
 960
 961                 return true; // failed
 962         } else if (cur_ops->check_boost_failed && !cur_ops->check_boost_failed(gp_state, NULL)) {
 963                 *start = jiffies;
 964         }
 965
 966         return false; // passed
 967 }
 968
 969 static int rcu_torture_boost(void *arg)
 970 {
 971         unsigned long endtime;
 972         unsigned long gp_state;
 973         unsigned long gp_state_time;
 974         unsigned long oldstarttime;
 975
 976         VERBOSE_TOROUT_STRING("rcu_torture_boost started");
 977
 978         /* Set real-time priority. */
 979         sched_set_fifo_low(current);
 980
 981         /* Each pass through the following loop does one boost-test cycle. */
 982         do {
 983                 bool failed = false; // Test failed already in this test interval
 984                 bool gp_initiated = false;
 985
 986                 if (kthread_should_stop())
 987                         goto checkwait;
 988
 989                 /* Wait for the next test interval. */
 990                 oldstarttime = boost_starttime;
 991                 while (time_before(jiffies, oldstarttime)) {
 992                         schedule_timeout_interruptible(oldstarttime - jiffies);
 993                         if (stutter_wait("rcu_torture_boost"))
 994                                 sched_set_fifo_low(current);
 995                         if (torture_must_stop())
 996                                 goto checkwait;
 997                 }
 998
 999                 // Do one boost-test interval.
1000                 endtime = oldstarttime + test_boost_duration * HZ;
1001                 while (time_before(jiffies, endtime)) {
1002                         // Has current GP gone too long?
1003                         if (gp_initiated && !failed && !cur_ops->poll_gp_state(gp_state))
1004                                 failed = rcu_torture_boost_failed(gp_state, &gp_state_time);
1005                         // If we don't have a grace period in flight, start one.
1006                         if (!gp_initiated || cur_ops->poll_gp_state(gp_state)) {
1007                                 gp_state = cur_ops->start_gp_poll();
1008                                 gp_initiated = true;
1009                                 gp_state_time = jiffies;
1010                         }
1011                         if (stutter_wait("rcu_torture_boost")) {
1012                                 sched_set_fifo_low(current);
1013                                 // If the grace period already ended,
1014                                 // we don't know when that happened, so
1015                                 // start over.
1016                                 if (cur_ops->poll_gp_state(gp_state))
1017                                         gp_initiated = false;
1018                         }
1019                         if (torture_must_stop())
1020                                 goto checkwait;
1021                 }
1022
1023                 // In case the grace period extended beyond the end of the loop.
1024                 if (gp_initiated && !failed && !cur_ops->poll_gp_state(gp_state))
1025                         rcu_torture_boost_failed(gp_state, &gp_state_time);
1026
1027                 /*
1028                  * Set the start time of the next test interval.
1029                  * Yes, this is vulnerable to long delays, but such
1030                  * delays simply cause a false negative for the next
1031                  * interval.  Besides, we are running at RT priority,
1032                  * so delays should be relatively rare.
1033                  */
1034                 while (oldstarttime == boost_starttime && !kthread_should_stop()) {
1035                         if (mutex_trylock(&boost_mutex)) {
1036                                 if (oldstarttime == boost_starttime) {
1037                                         boost_starttime = jiffies + test_boost_interval * HZ;
1038                                         n_rcu_torture_boosts++;
1039                                 }
1040                                 mutex_unlock(&boost_mutex);
1041                                 break;
1042                         }
1043                         schedule_timeout_uninterruptible(1);
1044                 }
1045
1046                 /* Go do the stutter. */
1047 checkwait:      if (stutter_wait("rcu_torture_boost"))
1048                         sched_set_fifo_low(current);
1049         } while (!torture_must_stop());
1050
1051         /* Clean up and exit. */
1052         while (!kthread_should_stop()) {
1053                 torture_shutdown_absorb("rcu_torture_boost");
1054                 schedule_timeout_uninterruptible(1);
1055         }
1056         torture_kthread_stopping("rcu_torture_boost");
1057         return 0;
1058 }
1059
1060 /*
1061  * RCU torture force-quiescent-state kthread.  Repeatedly induces
1062  * bursts of calls to force_quiescent_state(), increasing the probability
1063  * of occurrence of some important types of race conditions.
1064  */
1065 static int
1066 rcu_torture_fqs(void *arg)
1067 {
1068         unsigned long fqs_resume_time;
1069         int fqs_burst_remaining;
1070         int oldnice = task_nice(current);
1071
1072         VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
1073         do {
1074                 fqs_resume_time = jiffies + fqs_stutter * HZ;
1075                 while (time_before(jiffies, fqs_resume_time) &&
1076                        !kthread_should_stop()) {
1077                         schedule_timeout_interruptible(1);
1078                 }
1079                 fqs_burst_remaining = fqs_duration;
1080                 while (fqs_burst_remaining > 0 &&
1081                        !kthread_should_stop()) {
1082                         cur_ops->fqs();
1083                         udelay(fqs_holdoff);
1084                         fqs_burst_remaining -= fqs_holdoff;
1085                 }
1086                 if (stutter_wait("rcu_torture_fqs"))
1087                         sched_set_normal(current, oldnice);
1088         } while (!torture_must_stop());
1089         torture_kthread_stopping("rcu_torture_fqs");
1090         return 0;
1091 }
1092
1093 // Used by writers to randomly choose from the available grace-period
1094 // primitives.  The only purpose of the initialization is to size the array.
1095 static int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC, RTWS_COND_GET, RTWS_POLL_GET, RTWS_SYNC };
1096 static int nsynctypes;
1097
1098 /*
1099  * Determine which grace-period primitives are available.
1100  */
1101 static void rcu_torture_write_types(void)
1102 {
1103         bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
1104         bool gp_poll1 = gp_poll, gp_sync1 = gp_sync;
1105
1106         /* Initialize synctype[] array.  If none set, take default. */
1107         if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_poll1 && !gp_sync1)
1108                 gp_cond1 = gp_exp1 = gp_normal1 = gp_poll1 = gp_sync1 = true;
1109         if (gp_cond1 && cur_ops->get_gp_state && cur_ops->cond_sync) {
1110                 synctype[nsynctypes++] = RTWS_COND_GET;
1111                 pr_info("%s: Testing conditional GPs.\n", __func__);
1112         } else if (gp_cond && (!cur_ops->get_gp_state || !cur_ops->cond_sync)) {
1113                 pr_alert("%s: gp_cond without primitives.\n", __func__);
1114         }
1115         if (gp_exp1 && cur_ops->exp_sync) {
1116                 synctype[nsynctypes++] = RTWS_EXP_SYNC;
1117                 pr_info("%s: Testing expedited GPs.\n", __func__);
1118         } else if (gp_exp && !cur_ops->exp_sync) {
1119                 pr_alert("%s: gp_exp without primitives.\n", __func__);
1120         }
1121         if (gp_normal1 && cur_ops->deferred_free) {
1122                 synctype[nsynctypes++] = RTWS_DEF_FREE;
1123                 pr_info("%s: Testing asynchronous GPs.\n", __func__);
1124         } else if (gp_normal && !cur_ops->deferred_free) {
1125                 pr_alert("%s: gp_normal without primitives.\n", __func__);
1126         }
1127         if (gp_poll1 && cur_ops->start_gp_poll && cur_ops->poll_gp_state) {
1128                 synctype[nsynctypes++] = RTWS_POLL_GET;
1129                 pr_info("%s: Testing polling GPs.\n", __func__);
1130         } else if (gp_poll && (!cur_ops->start_gp_poll || !cur_ops->poll_gp_state)) {
1131                 pr_alert("%s: gp_poll without primitives.\n", __func__);
1132         }
1133         if (gp_sync1 && cur_ops->sync) {
1134                 synctype[nsynctypes++] = RTWS_SYNC;
1135                 pr_info("%s: Testing normal GPs.\n", __func__);
1136         } else if (gp_sync && !cur_ops->sync) {
1137                 pr_alert("%s: gp_sync without primitives.\n", __func__);
1138         }
1139 }
1140
1141 /*
1142  * RCU torture writer kthread.  Repeatedly substitutes a new structure
1143  * for that pointed to by rcu_torture_current, freeing the old structure
1144  * after a series of grace periods (the "pipeline").
1145  */
1146 static int
1147 rcu_torture_writer(void *arg)
1148 {
1149         bool boot_ended;
1150         bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
1151         unsigned long cookie;
1152         int expediting = 0;
1153         unsigned long gp_snap;
1154         int i;
1155         int idx;
1156         int oldnice = task_nice(current);
1157         struct rcu_torture *rp;
1158         struct rcu_torture *old_rp;
1159         static DEFINE_TORTURE_RANDOM(rand);
1160         bool stutter_waited;
1161
1162         VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
1163         if (!can_expedite)
1164                 pr_alert("%s" TORTURE_FLAG
1165                          " GP expediting controlled from boot/sysfs for %s.\n",
1166                          torture_type, cur_ops->name);
1167         if (WARN_ONCE(nsynctypes == 0,
1168                       "rcu_torture_writer: No update-side primitives.\n")) {
1169                 /*
1170                  * No updates primitives, so don't try updating.
1171                  * The resulting test won't be testing much, hence the
1172                  * above WARN_ONCE().
1173                  */
1174                 rcu_torture_writer_state = RTWS_STOPPING;
1175                 torture_kthread_stopping("rcu_torture_writer");
1176         }
1177
1178         do {
1179                 rcu_torture_writer_state = RTWS_FIXED_DELAY;
1180                 torture_hrtimeout_us(500, 1000, &rand);
1181                 rp = rcu_torture_alloc();
1182                 if (rp == NULL)
1183                         continue;
1184                 rp->rtort_pipe_count = 0;
1185                 rcu_torture_writer_state = RTWS_DELAY;
1186                 udelay(torture_random(&rand) & 0x3ff);
1187                 rcu_torture_writer_state = RTWS_REPLACE;
1188                 old_rp = rcu_dereference_check(rcu_torture_current,
1189                                                current == writer_task);
1190                 rp->rtort_mbtest = 1;
1191                 rcu_assign_pointer(rcu_torture_current, rp);
1192                 smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
1193                 if (old_rp) {
1194                         i = old_rp->rtort_pipe_count;
1195                         if (i > RCU_TORTURE_PIPE_LEN)
1196                                 i = RCU_TORTURE_PIPE_LEN;
1197                         atomic_inc(&rcu_torture_wcount[i]);
1198                         WRITE_ONCE(old_rp->rtort_pipe_count,
1199                                    old_rp->rtort_pipe_count + 1);
1200                         if (cur_ops->get_gp_state && cur_ops->poll_gp_state) {
1201                                 idx = cur_ops->readlock();
1202                                 cookie = cur_ops->get_gp_state();
1203                                 WARN_ONCE(rcu_torture_writer_state != RTWS_DEF_FREE &&
1204                                           cur_ops->poll_gp_state(cookie),
1205                                           "%s: Cookie check 1 failed %s(%d) %lu->%lu\n",
1206                                           __func__,
1207                                           rcu_torture_writer_state_getname(),
1208                                           rcu_torture_writer_state,
1209                                           cookie, cur_ops->get_gp_state());
1210                                 cur_ops->readunlock(idx);
1211                         }
1212                         switch (synctype[torture_random(&rand) % nsynctypes]) {
1213                         case RTWS_DEF_FREE:
1214                                 rcu_torture_writer_state = RTWS_DEF_FREE;
1215                                 cur_ops->deferred_free(old_rp);
1216                                 break;
1217                         case RTWS_EXP_SYNC:
1218                                 rcu_torture_writer_state = RTWS_EXP_SYNC;
1219                                 cur_ops->exp_sync();
1220                                 rcu_torture_pipe_update(old_rp);
1221                                 break;
1222                         case RTWS_COND_GET:
1223                                 rcu_torture_writer_state = RTWS_COND_GET;
1224                                 gp_snap = cur_ops->get_gp_state();
1225                                 torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
1226                                 rcu_torture_writer_state = RTWS_COND_SYNC;
1227                                 cur_ops->cond_sync(gp_snap);
1228                                 rcu_torture_pipe_update(old_rp);
1229                                 break;
1230                         case RTWS_POLL_GET:
1231                                 rcu_torture_writer_state = RTWS_POLL_GET;
1232                                 gp_snap = cur_ops->start_gp_poll();
1233                                 rcu_torture_writer_state = RTWS_POLL_WAIT;
1234                                 while (!cur_ops->poll_gp_state(gp_snap))
1235                                         torture_hrtimeout_jiffies(torture_random(&rand) % 16,
1236                                                                   &rand);
1237                                 rcu_torture_pipe_update(old_rp);
1238                                 break;
1239                         case RTWS_SYNC:
1240                                 rcu_torture_writer_state = RTWS_SYNC;
1241                                 cur_ops->sync();
1242                                 rcu_torture_pipe_update(old_rp);
1243                                 break;
1244                         default:
1245                                 WARN_ON_ONCE(1);
1246                                 break;
1247                         }
1248                 }
1249                 WRITE_ONCE(rcu_torture_current_version,
1250                            rcu_torture_current_version + 1);
1251                 /* Cycle through nesting levels of rcu_expedite_gp() calls. */
1252                 if (can_expedite &&
1253                     !(torture_random(&rand) & 0xff & (!!expediting - 1))) {
1254                         WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited());
1255                         if (expediting >= 0)
1256                                 rcu_expedite_gp();
1257                         else
1258                                 rcu_unexpedite_gp();
1259                         if (++expediting > 3)
1260                                 expediting = -expediting;
1261                 } else if (!can_expedite) { /* Disabled during boot, recheck. */
1262                         can_expedite = !rcu_gp_is_expedited() &&
1263                                        !rcu_gp_is_normal();
1264                 }
1265                 rcu_torture_writer_state = RTWS_STUTTER;
1266                 boot_ended = rcu_inkernel_boot_has_ended();
1267                 stutter_waited = stutter_wait("rcu_torture_writer");
1268                 if (stutter_waited &&
1269                     !READ_ONCE(rcu_fwd_cb_nodelay) &&
1270                     !cur_ops->slow_gps &&
1271                     !torture_must_stop() &&
1272                     boot_ended)
1273                         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
1274                                 if (list_empty(&rcu_tortures[i].rtort_free) &&
1275                                     rcu_access_pointer(rcu_torture_current) !=
1276                                     &rcu_tortures[i]) {
1277                                         rcu_ftrace_dump(DUMP_ALL);
1278                                         WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
1279                                 }
1280                 if (stutter_waited)
1281                         sched_set_normal(current, oldnice);
1282         } while (!torture_must_stop());
1283         rcu_torture_current = NULL;  // Let stats task know that we are done.
1284         /* Reset expediting back to unexpedited. */
1285         if (expediting > 0)
1286                 expediting = -expediting;
1287         while (can_expedite && expediting++ < 0)
1288                 rcu_unexpedite_gp();
1289         WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited());
1290         if (!can_expedite)
1291                 pr_alert("%s" TORTURE_FLAG
1292                          " Dynamic grace-period expediting was disabled.\n",
1293                          torture_type);
1294         rcu_torture_writer_state = RTWS_STOPPING;
1295         torture_kthread_stopping("rcu_torture_writer");
1296         return 0;
1297 }
1298
1299 /*
1300  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
1301  * delay between calls.
1302  */
1303 static int
1304 rcu_torture_fakewriter(void *arg)
1305 {
1306         unsigned long gp_snap;
1307         DEFINE_TORTURE_RANDOM(rand);
1308
1309         VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
1310         set_user_nice(current, MAX_NICE);
1311
1312         do {
1313                 torture_hrtimeout_jiffies(torture_random(&rand) % 10, &rand);
1314                 if (cur_ops->cb_barrier != NULL &&
1315                     torture_random(&rand) % (nfakewriters * 8) == 0) {
1316                         cur_ops->cb_barrier();
1317                 } else {
1318                         switch (synctype[torture_random(&rand) % nsynctypes]) {
1319                         case RTWS_DEF_FREE:
1320                                 break;
1321                         case RTWS_EXP_SYNC:
1322                                 cur_ops->exp_sync();
1323                                 break;
1324                         case RTWS_COND_GET:
1325                                 gp_snap = cur_ops->get_gp_state();
1326                                 torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
1327                                 cur_ops->cond_sync(gp_snap);
1328                                 break;
1329                         case RTWS_POLL_GET:
1330                                 gp_snap = cur_ops->start_gp_poll();
1331                                 while (!cur_ops->poll_gp_state(gp_snap)) {
1332                                         torture_hrtimeout_jiffies(torture_random(&rand) % 16,
1333                                                                   &rand);
1334                                 }
1335                                 break;
1336                         case RTWS_SYNC:
1337                                 cur_ops->sync();
1338                                 break;
1339                         default:
1340                                 WARN_ON_ONCE(1);
1341                                 break;
1342                         }
1343                 }
1344                 stutter_wait("rcu_torture_fakewriter");
1345         } while (!torture_must_stop());
1346
1347         torture_kthread_stopping("rcu_torture_fakewriter");
1348         return 0;
1349 }
1350
1351 static void rcu_torture_timer_cb(struct rcu_head *rhp)
1352 {
1353         kfree(rhp);
1354 }
1355
1356 // Set up and carry out testing of RCU's global memory ordering
1357 static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp,
1358                                         struct torture_random_state *trsp)
1359 {
1360         unsigned long loops;
1361         int noc = torture_num_online_cpus();
1362         int rdrchked;
1363         int rdrchker;
1364         struct rcu_torture_reader_check *rtrcp; // Me.
1365         struct rcu_torture_reader_check *rtrcp_assigner; // Assigned us to do checking.
1366         struct rcu_torture_reader_check *rtrcp_chked; // Reader being checked.
1367         struct rcu_torture_reader_check *rtrcp_chker; // Reader doing checking when not me.
1368
1369         if (myid < 0)
1370                 return; // Don't try this from timer handlers.
1371
1372         // Increment my counter.
1373         rtrcp = &rcu_torture_reader_mbchk[myid];
1374         WRITE_ONCE(rtrcp->rtc_myloops, rtrcp->rtc_myloops + 1);
1375
1376         // Attempt to assign someone else some checking work.
1377         rdrchked = torture_random(trsp) % nrealreaders;
1378         rtrcp_chked = &rcu_torture_reader_mbchk[rdrchked];
1379         rdrchker = torture_random(trsp) % nrealreaders;
1380         rtrcp_chker = &rcu_torture_reader_mbchk[rdrchker];
1381         if (rdrchked != myid && rdrchked != rdrchker && noc >= rdrchked && noc >= rdrchker &&
1382             smp_load_acquire(&rtrcp->rtc_chkrdr) < 0 && // Pairs with smp_store_release below.
1383             !READ_ONCE(rtp->rtort_chkp) &&
1384             !smp_load_acquire(&rtrcp_chker->rtc_assigner)) { // Pairs with smp_store_release below.
1385                 rtrcp->rtc_chkloops = READ_ONCE(rtrcp_chked->rtc_myloops);
1386                 WARN_ON_ONCE(rtrcp->rtc_chkrdr >= 0);
1387                 rtrcp->rtc_chkrdr = rdrchked;
1388                 WARN_ON_ONCE(rtrcp->rtc_ready); // This gets set after the grace period ends.
1389                 if (cmpxchg_relaxed(&rtrcp_chker->rtc_assigner, NULL, rtrcp) ||
1390                     cmpxchg_relaxed(&rtp->rtort_chkp, NULL, rtrcp))
1391                         (void)cmpxchg_relaxed(&rtrcp_chker->rtc_assigner, rtrcp, NULL); // Back out.
1392         }
1393
1394         // If assigned some completed work, do it!
1395         rtrcp_assigner = READ_ONCE(rtrcp->rtc_assigner);
1396         if (!rtrcp_assigner || !smp_load_acquire(&rtrcp_assigner->rtc_ready))
1397                 return; // No work or work not yet ready.
1398         rdrchked = rtrcp_assigner->rtc_chkrdr;
1399         if (WARN_ON_ONCE(rdrchked < 0))
1400                 return;
1401         rtrcp_chked = &rcu_torture_reader_mbchk[rdrchked];
1402         loops = READ_ONCE(rtrcp_chked->rtc_myloops);
1403         atomic_inc(&n_rcu_torture_mbchk_tries);
1404         if (ULONG_CMP_LT(loops, rtrcp_assigner->rtc_chkloops))
1405                 atomic_inc(&n_rcu_torture_mbchk_fail);
1406         rtrcp_assigner->rtc_chkloops = loops + ULONG_MAX / 2;
1407         rtrcp_assigner->rtc_ready = 0;
1408         smp_store_release(&rtrcp->rtc_assigner, NULL); // Someone else can assign us work.
1409         smp_store_release(&rtrcp_assigner->rtc_chkrdr, -1); // Assigner can again assign.
1410 }
1411
1412 /*
1413  * Do one extension of an RCU read-side critical section using the
1414  * current reader state in readstate (set to zero for initial entry
1415  * to extended critical section), set the new state as specified by
1416  * newstate (set to zero for final exit from extended critical section),
1417  * and random-number-generator state in trsp.  If this is neither the
1418  * beginning or end of the critical section and if there was actually a
1419  * change, do a ->read_delay().
1420  */
1421 static void rcutorture_one_extend(int *readstate, int newstate,
1422                                   struct torture_random_state *trsp,
1423                                   struct rt_read_seg *rtrsp)
1424 {
1425         unsigned long flags;
1426         int idxnew = -1;
1427         int idxold = *readstate;
1428         int statesnew = ~*readstate & newstate;
1429         int statesold = *readstate & ~newstate;
1430
1431         WARN_ON_ONCE(idxold < 0);
1432         WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1);
1433         rtrsp->rt_readstate = newstate;
1434
1435         /* First, put new protection in place to avoid critical-section gap. */
1436         if (statesnew & RCUTORTURE_RDR_BH)
1437                 local_bh_disable();
1438         if (statesnew & RCUTORTURE_RDR_RBH)
1439                 rcu_read_lock_bh();
1440         if (statesnew & RCUTORTURE_RDR_IRQ)
1441                 local_irq_disable();
1442         if (statesnew & RCUTORTURE_RDR_PREEMPT)
1443                 preempt_disable();
1444         if (statesnew & RCUTORTURE_RDR_SCHED)
1445                 rcu_read_lock_sched();
1446         if (statesnew & RCUTORTURE_RDR_RCU)
1447                 idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT;
1448
1449         /*
1450          * Next, remove old protection, in decreasing order of strength
1451          * to avoid unlock paths that aren't safe in the stronger
1452          * context. Namely: BH can not be enabled with disabled interrupts.
1453          * Additionally PREEMPT_RT requires that BH is enabled in preemptible
1454          * context.
1455          */
1456         if (statesold & RCUTORTURE_RDR_IRQ)
1457                 local_irq_enable();
1458         if (statesold & RCUTORTURE_RDR_PREEMPT)
1459                 preempt_enable();
1460         if (statesold & RCUTORTURE_RDR_SCHED)
1461                 rcu_read_unlock_sched();
1462         if (statesold & RCUTORTURE_RDR_BH)
1463                 local_bh_enable();
1464         if (statesold & RCUTORTURE_RDR_RBH)
1465                 rcu_read_unlock_bh();
1466         if (statesold & RCUTORTURE_RDR_RCU) {
1467                 bool lockit = !statesnew && !(torture_random(trsp) & 0xffff);
1468
1469                 if (lockit)
1470                         raw_spin_lock_irqsave(&current->pi_lock, flags);
1471                 cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT);
1472                 if (lockit)
1473                         raw_spin_unlock_irqrestore(&current->pi_lock, flags);
1474         }
1475
1476         /* Delay if neither beginning nor end and there was a change. */
1477         if ((statesnew || statesold) && *readstate && newstate)
1478                 cur_ops->read_delay(trsp, rtrsp);
1479
1480         /* Update the reader state. */
1481         if (idxnew == -1)
1482                 idxnew = idxold & ~RCUTORTURE_RDR_MASK;
1483         WARN_ON_ONCE(idxnew < 0);
1484         WARN_ON_ONCE((idxnew >> RCUTORTURE_RDR_SHIFT) > 1);
1485         *readstate = idxnew | newstate;
1486         WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) < 0);
1487         WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) > 1);
1488 }
1489
1490 /* Return the biggest extendables mask given current RCU and boot parameters. */
1491 static int rcutorture_extend_mask_max(void)
1492 {
1493         int mask;
1494
1495         WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND);
1496         mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables;
1497         mask = mask | RCUTORTURE_RDR_RCU;
1498         return mask;
1499 }
1500
1501 /* Return a random protection state mask, but with at least one bit set. */
1502 static int
1503 rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
1504 {
1505         int mask = rcutorture_extend_mask_max();
1506         unsigned long randmask1 = torture_random(trsp) >> 8;
1507         unsigned long randmask2 = randmask1 >> 3;
1508         unsigned long preempts = RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
1509         unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ;
1510         unsigned long bhs = RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
1511
1512         WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT);
1513         /* Mostly only one bit (need preemption!), sometimes lots of bits. */
1514         if (!(randmask1 & 0x7))
1515                 mask = mask & randmask2;
1516         else
1517                 mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));
1518
1519         /*
1520          * Can't enable bh w/irq disabled.
1521          */
1522         if (mask & RCUTORTURE_RDR_IRQ)
1523                 mask |= oldmask & bhs;
1524
1525         /*
1526          * Ideally these sequences would be detected in debug builds
1527          * (regardless of RT), but until then don't stop testing
1528          * them on non-RT.
1529          */
1530         if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
1531                 /* Can't modify BH in atomic context */
1532                 if (oldmask & preempts_irq)
1533                         mask &= ~bhs;
1534                 if ((oldmask | mask) & preempts_irq)
1535                         mask |= oldmask & bhs;
1536         }
1537
1538         return mask ?: RCUTORTURE_RDR_RCU;
1539 }
1540
1541 /*
1542  * Do a randomly selected number of extensions of an existing RCU read-side
1543  * critical section.
1544  */
1545 static struct rt_read_seg *
1546 rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
1547                        struct rt_read_seg *rtrsp)
1548 {
1549         int i;
1550         int j;
1551         int mask = rcutorture_extend_mask_max();
1552
1553         WARN_ON_ONCE(!*readstate); /* -Existing- RCU read-side critsect! */
1554         if (!((mask - 1) & mask))
1555                 return rtrsp;  /* Current RCU reader not extendable. */
1556         /* Bias towards larger numbers of loops. */
1557         i = (torture_random(trsp) >> 3);
1558         i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
1559         for (j = 0; j < i; j++) {
1560                 mask = rcutorture_extend_mask(*readstate, trsp);
1561                 rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
1562         }
1563         return &rtrsp[j];
1564 }
1565
1566 /*
1567  * Do one read-side critical section, returning false if there was
1568  * no data to read.  Can be invoked both from process context and
1569  * from a timer handler.
1570  */
1571 static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
1572 {
1573         unsigned long cookie;
1574         int i;
1575         unsigned long started;
1576         unsigned long completed;
1577         int newstate;
1578         struct rcu_torture *p;
1579         int pipe_count;
1580         int readstate = 0;
1581         struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS] = { { 0 } };
1582         struct rt_read_seg *rtrsp = &rtseg[0];
1583         struct rt_read_seg *rtrsp1;
1584         unsigned long long ts;
1585
1586         WARN_ON_ONCE(!rcu_is_watching());
1587         newstate = rcutorture_extend_mask(readstate, trsp);
1588         rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
1589         if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
1590                 cookie = cur_ops->get_gp_state();
1591         started = cur_ops->get_gp_seq();
1592         ts = rcu_trace_clock_local();
1593         p = rcu_dereference_check(rcu_torture_current,
1594                                   !cur_ops->readlock_held || cur_ops->readlock_held());
1595         if (p == NULL) {
1596                 /* Wait for rcu_torture_writer to get underway */
1597                 rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
1598                 return false;
1599         }
1600         if (p->rtort_mbtest == 0)
1601                 atomic_inc(&n_rcu_torture_mberror);
1602         rcu_torture_reader_do_mbchk(myid, p, trsp);
1603         rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
1604         preempt_disable();
1605         pipe_count = READ_ONCE(p->rtort_pipe_count);
1606         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
1607                 /* Should not happen, but... */
1608                 pipe_count = RCU_TORTURE_PIPE_LEN;
1609         }
1610         completed = cur_ops->get_gp_seq();
1611         if (pipe_count > 1) {
1612                 do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
1613                                           ts, started, completed);
1614                 rcu_ftrace_dump(DUMP_ALL);
1615         }
1616         __this_cpu_inc(rcu_torture_count[pipe_count]);
1617         completed = rcutorture_seq_diff(completed, started);
1618         if (completed > RCU_TORTURE_PIPE_LEN) {
1619                 /* Should not happen, but... */
1620                 completed = RCU_TORTURE_PIPE_LEN;
1621         }
1622         __this_cpu_inc(rcu_torture_batch[completed]);
1623         preempt_enable();
1624         if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
1625                 WARN_ONCE(cur_ops->poll_gp_state(cookie),
1626                           "%s: Cookie check 2 failed %s(%d) %lu->%lu\n",
1627                           __func__,
1628                           rcu_torture_writer_state_getname(),
1629                           rcu_torture_writer_state,
1630                           cookie, cur_ops->get_gp_state());
1631         rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
1632         WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK);
1633         // This next splat is expected behavior if leakpointer, especially
1634         // for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels.
1635         WARN_ON_ONCE(leakpointer && READ_ONCE(p->rtort_pipe_count) > 1);
1636
1637         /* If error or close call, record the sequence of reader protections. */
1638         if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
1639                 i = 0;
1640                 for (rtrsp1 = &rtseg[0]; rtrsp1 < rtrsp; rtrsp1++)
1641                         err_segs[i++] = *rtrsp1;
1642                 rt_read_nsegs = i;
1643         }
1644
1645         return true;
1646 }
1647
1648 static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);
1649
1650 /*
1651  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
1652  * incrementing the corresponding element of the pipeline array.  The
1653  * counter in the element should never be greater than 1, otherwise, the
1654  * RCU implementation is broken.
1655  */
1656 static void rcu_torture_timer(struct timer_list *unused)
1657 {
1658         atomic_long_inc(&n_rcu_torture_timers);
1659         (void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand), -1);
1660
1661         /* Test call_rcu() invocation from interrupt handler. */
1662         if (cur_ops->call) {
1663                 struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_NOWAIT);
1664
1665                 if (rhp)
1666                         cur_ops->call(rhp, rcu_torture_timer_cb);
1667         }
1668 }
1669
1670 /*
1671  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
1672  * incrementing the corresponding element of the pipeline array.  The
1673  * counter in the element should never be greater than 1, otherwise, the
1674  * RCU implementation is broken.
1675  */
1676 static int
1677 rcu_torture_reader(void *arg)
1678 {
1679         unsigned long lastsleep = jiffies;
1680         long myid = (long)arg;
1681         int mynumonline = myid;
1682         DEFINE_TORTURE_RANDOM(rand);
1683         struct timer_list t;
1684
1685         VERBOSE_TOROUT_STRING("rcu_torture_reader task started");
1686         set_user_nice(current, MAX_NICE);
1687         if (irqreader && cur_ops->irq_capable)
1688                 timer_setup_on_stack(&t, rcu_torture_timer, 0);
1689         tick_dep_set_task(current, TICK_DEP_BIT_RCU);
1690         do {
1691                 if (irqreader && cur_ops->irq_capable) {
1692                         if (!timer_pending(&t))
1693                                 mod_timer(&t, jiffies + 1);
1694                 }
1695                 if (!rcu_torture_one_read(&rand, myid) && !torture_must_stop())
1696                         schedule_timeout_interruptible(HZ);
1697                 if (time_after(jiffies, lastsleep) && !torture_must_stop()) {
1698                         torture_hrtimeout_us(500, 1000, &rand);
1699                         lastsleep = jiffies + 10;
1700                 }
1701                 while (torture_num_online_cpus() < mynumonline && !torture_must_stop())
1702                         schedule_timeout_interruptible(HZ / 5);
1703                 stutter_wait("rcu_torture_reader");
1704         } while (!torture_must_stop());
1705         if (irqreader && cur_ops->irq_capable) {
1706                 del_timer_sync(&t);
1707                 destroy_timer_on_stack(&t);
1708         }
1709         tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
1710         torture_kthread_stopping("rcu_torture_reader");
1711         return 0;
1712 }
1713
1714 /*
1715  * Randomly Toggle CPUs' callback-offload state.  This uses hrtimers to
1716  * increase race probabilities and fuzzes the interval between toggling.
1717  */
1718 static int rcu_nocb_toggle(void *arg)
1719 {
1720         int cpu;
1721         int maxcpu = -1;
1722         int oldnice = task_nice(current);
1723         long r;
1724         DEFINE_TORTURE_RANDOM(rand);
1725         ktime_t toggle_delay;
1726         unsigned long toggle_fuzz;
1727         ktime_t toggle_interval = ms_to_ktime(nocbs_toggle);
1728
1729         VERBOSE_TOROUT_STRING("rcu_nocb_toggle task started");
1730         while (!rcu_inkernel_boot_has_ended())
1731                 schedule_timeout_interruptible(HZ / 10);
1732         for_each_online_cpu(cpu)
1733                 maxcpu = cpu;
1734         WARN_ON(maxcpu < 0);
1735         if (toggle_interval > ULONG_MAX)
1736                 toggle_fuzz = ULONG_MAX >> 3;
1737         else
1738                 toggle_fuzz = toggle_interval >> 3;
1739         if (toggle_fuzz <= 0)
1740                 toggle_fuzz = NSEC_PER_USEC;
1741         do {
1742                 r = torture_random(&rand);
1743                 cpu = (r >> 4) % (maxcpu + 1);
1744                 if (r & 0x1) {
1745                         rcu_nocb_cpu_offload(cpu);
1746                         atomic_long_inc(&n_nocb_offload);
1747                 } else {
1748                         rcu_nocb_cpu_deoffload(cpu);
1749                         atomic_long_inc(&n_nocb_deoffload);
1750                 }
1751                 toggle_delay = torture_random(&rand) % toggle_fuzz + toggle_interval;
1752                 set_current_state(TASK_INTERRUPTIBLE);
1753                 schedule_hrtimeout(&toggle_delay, HRTIMER_MODE_REL);
1754                 if (stutter_wait("rcu_nocb_toggle"))
1755                         sched_set_normal(current, oldnice);
1756         } while (!torture_must_stop());
1757         torture_kthread_stopping("rcu_nocb_toggle");
1758         return 0;
1759 }
1760
1761 /*
1762  * Print torture statistics.  Caller must ensure that there is only
1763  * one call to this function at a given time!!!  This is normally
1764  * accomplished by relying on the module system to only have one copy
1765  * of the module loaded, and then by giving the rcu_torture_stats
1766  * kthread full control (or the init/cleanup functions when rcu_torture_stats
1767  * thread is not running).
1768  */
1769 static void
1770 rcu_torture_stats_print(void)
1771 {
1772         int cpu;
1773         int i;
1774         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1775         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1776         struct rcu_torture *rtcp;
1777         static unsigned long rtcv_snap = ULONG_MAX;
1778         static bool splatted;
1779         struct task_struct *wtp;
1780
1781         for_each_possible_cpu(cpu) {
1782                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1783                         pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
1784                         batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
1785                 }
1786         }
1787         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
1788                 if (pipesummary[i] != 0)
1789                         break;
1790         }
1791
1792         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1793         rtcp = rcu_access_pointer(rcu_torture_current);
1794         pr_cont("rtc: %p %s: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
1795                 rtcp,
1796                 rtcp && !rcu_stall_is_suppressed_at_boot() ? "ver" : "VER",
1797                 rcu_torture_current_version,
1798                 list_empty(&rcu_torture_freelist),
1799                 atomic_read(&n_rcu_torture_alloc),
1800                 atomic_read(&n_rcu_torture_alloc_fail),
1801                 atomic_read(&n_rcu_torture_free));
1802         pr_cont("rtmbe: %d rtmbkf: %d/%d rtbe: %ld rtbke: %ld rtbre: %ld ",
1803                 atomic_read(&n_rcu_torture_mberror),
1804                 atomic_read(&n_rcu_torture_mbchk_fail), atomic_read(&n_rcu_torture_mbchk_tries),
1805                 n_rcu_torture_barrier_error,
1806                 n_rcu_torture_boost_ktrerror,
1807                 n_rcu_torture_boost_rterror);
1808         pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
1809                 n_rcu_torture_boost_failure,
1810                 n_rcu_torture_boosts,
1811                 atomic_long_read(&n_rcu_torture_timers));
1812         torture_onoff_stats();
1813         pr_cont("barrier: %ld/%ld:%ld ",
1814                 data_race(n_barrier_successes),
1815                 data_race(n_barrier_attempts),
1816                 data_race(n_rcu_torture_barrier_error));
1817         pr_cont("read-exits: %ld ", data_race(n_read_exits)); // Statistic.
1818         pr_cont("nocb-toggles: %ld:%ld\n",
1819                 atomic_long_read(&n_nocb_offload), atomic_long_read(&n_nocb_deoffload));
1820
1821         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1822         if (atomic_read(&n_rcu_torture_mberror) ||
1823             atomic_read(&n_rcu_torture_mbchk_fail) ||
1824             n_rcu_torture_barrier_error || n_rcu_torture_boost_ktrerror ||
1825             n_rcu_torture_boost_rterror || n_rcu_torture_boost_failure ||
1826             i > 1) {
1827                 pr_cont("%s", "!!! ");
1828                 atomic_inc(&n_rcu_torture_error);
1829                 WARN_ON_ONCE(atomic_read(&n_rcu_torture_mberror));
1830                 WARN_ON_ONCE(atomic_read(&n_rcu_torture_mbchk_fail));
1831                 WARN_ON_ONCE(n_rcu_torture_barrier_error);  // rcu_barrier()
1832                 WARN_ON_ONCE(n_rcu_torture_boost_ktrerror); // no boost kthread
1833                 WARN_ON_ONCE(n_rcu_torture_boost_rterror); // can't set RT prio
1834                 WARN_ON_ONCE(n_rcu_torture_boost_failure); // boost failed (TIMER_SOFTIRQ RT prio?)
1835                 WARN_ON_ONCE(i > 1); // Too-short grace period
1836         }
1837         pr_cont("Reader Pipe: ");
1838         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1839                 pr_cont(" %ld", pipesummary[i]);
1840         pr_cont("\n");
1841
1842         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1843         pr_cont("Reader Batch: ");
1844         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1845                 pr_cont(" %ld", batchsummary[i]);
1846         pr_cont("\n");
1847
1848         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1849         pr_cont("Free-Block Circulation: ");
1850         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1851                 pr_cont(" %d", atomic_read(&rcu_torture_wcount[i]));
1852         }
1853         pr_cont("\n");
1854
1855         if (cur_ops->stats)
1856                 cur_ops->stats();
1857         if (rtcv_snap == rcu_torture_current_version &&
1858             rcu_access_pointer(rcu_torture_current) &&
1859             !rcu_stall_is_suppressed()) {
1860                 int __maybe_unused flags = 0;
1861                 unsigned long __maybe_unused gp_seq = 0;
1862
1863                 rcutorture_get_gp_data(cur_ops->ttype,
1864                                        &flags, &gp_seq);
1865                 srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
1866                                         &flags, &gp_seq);
1867                 wtp = READ_ONCE(writer_task);
1868                 pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#x cpu %d\n",
1869                          rcu_torture_writer_state_getname(),
1870                          rcu_torture_writer_state, gp_seq, flags,
1871                          wtp == NULL ? ~0U : wtp->__state,
1872                          wtp == NULL ? -1 : (int)task_cpu(wtp));
1873                 if (!splatted && wtp) {
1874                         sched_show_task(wtp);
1875                         splatted = true;
1876                 }
1877                 if (cur_ops->gp_kthread_dbg)
1878                         cur_ops->gp_kthread_dbg();
1879                 rcu_ftrace_dump(DUMP_ALL);
1880         }
1881         rtcv_snap = rcu_torture_current_version;
1882 }
1883
1884 /*
1885  * Periodically prints torture statistics, if periodic statistics printing
1886  * was specified via the stat_interval module parameter.
1887  */
1888 static int
1889 rcu_torture_stats(void *arg)
1890 {
1891         VERBOSE_TOROUT_STRING("rcu_torture_stats task started");
1892         do {
1893                 schedule_timeout_interruptible(stat_interval * HZ);
1894                 rcu_torture_stats_print();
1895                 torture_shutdown_absorb("rcu_torture_stats");
1896         } while (!torture_must_stop());
1897         torture_kthread_stopping("rcu_torture_stats");
1898         return 0;
1899 }
1900
1901 /* Test mem_dump_obj() and friends.  */
1902 static void rcu_torture_mem_dump_obj(void)
1903 {
1904         struct rcu_head *rhp;
1905         struct kmem_cache *kcp;
1906         static int z;
1907
1908         kcp = kmem_cache_create("rcuscale", 136, 8, SLAB_STORE_USER, NULL);
1909         rhp = kmem_cache_alloc(kcp, GFP_KERNEL);
1910         pr_alert("mem_dump_obj() slab test: rcu_torture_stats = %px, &rhp = %px, rhp = %px, &z = %px\n", stats_task, &rhp, rhp, &z);
1911         pr_alert("mem_dump_obj(ZERO_SIZE_PTR):");
1912         mem_dump_obj(ZERO_SIZE_PTR);
1913         pr_alert("mem_dump_obj(NULL):");
1914         mem_dump_obj(NULL);
1915         pr_alert("mem_dump_obj(%px):", &rhp);
1916         mem_dump_obj(&rhp);
1917         pr_alert("mem_dump_obj(%px):", rhp);
1918         mem_dump_obj(rhp);
1919         pr_alert("mem_dump_obj(%px):", &rhp->func);
1920         mem_dump_obj(&rhp->func);
1921         pr_alert("mem_dump_obj(%px):", &z);
1922         mem_dump_obj(&z);
1923         kmem_cache_free(kcp, rhp);
1924         kmem_cache_destroy(kcp);
1925         rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
1926         pr_alert("mem_dump_obj() kmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
1927         pr_alert("mem_dump_obj(kmalloc %px):", rhp);
1928         mem_dump_obj(rhp);
1929         pr_alert("mem_dump_obj(kmalloc %px):", &rhp->func);
1930         mem_dump_obj(&rhp->func);
1931         kfree(rhp);
1932         rhp = vmalloc(4096);
1933         pr_alert("mem_dump_obj() vmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
1934         pr_alert("mem_dump_obj(vmalloc %px):", rhp);
1935         mem_dump_obj(rhp);
1936         pr_alert("mem_dump_obj(vmalloc %px):", &rhp->func);
1937         mem_dump_obj(&rhp->func);
1938         vfree(rhp);
1939 }
1940
1941 static void
1942 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
1943 {
1944         pr_alert("%s" TORTURE_FLAG
1945                  "--- %s: nreaders=%d nfakewriters=%d "
1946                  "stat_interval=%d verbose=%d test_no_idle_hz=%d "
1947                  "shuffle_interval=%d stutter=%d irqreader=%d "
1948                  "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
1949                  "test_boost=%d/%d test_boost_interval=%d "
1950                  "test_boost_duration=%d shutdown_secs=%d "
1951                  "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
1952                  "stall_cpu_block=%d "
1953                  "n_barrier_cbs=%d "
1954                  "onoff_interval=%d onoff_holdoff=%d "
1955                  "read_exit_delay=%d read_exit_burst=%d "
1956                  "nocbs_nthreads=%d nocbs_toggle=%d\n",
1957                  torture_type, tag, nrealreaders, nfakewriters,
1958                  stat_interval, verbose, test_no_idle_hz, shuffle_interval,
1959                  stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
1960                  test_boost, cur_ops->can_boost,
1961                  test_boost_interval, test_boost_duration, shutdown_secs,
1962                  stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
1963                  stall_cpu_block,
1964                  n_barrier_cbs,
1965                  onoff_interval, onoff_holdoff,
1966                  read_exit_delay, read_exit_burst,
1967                  nocbs_nthreads, nocbs_toggle);
1968 }
1969
1970 static int rcutorture_booster_cleanup(unsigned int cpu)
1971 {
1972         struct task_struct *t;
1973
1974         if (boost_tasks[cpu] == NULL)
1975                 return 0;
1976         mutex_lock(&boost_mutex);
1977         t = boost_tasks[cpu];
1978         boost_tasks[cpu] = NULL;
1979         rcu_torture_enable_rt_throttle();
1980         mutex_unlock(&boost_mutex);
1981
1982         /* This must be outside of the mutex, otherwise deadlock! */
1983         torture_stop_kthread(rcu_torture_boost, t);
1984         return 0;
1985 }
1986
1987 static int rcutorture_booster_init(unsigned int cpu)
1988 {
1989         int retval;
1990
1991         if (boost_tasks[cpu] != NULL)
1992                 return 0;  /* Already created, nothing more to do. */
1993
1994         // Testing RCU priority boosting requires rcutorture do
1995         // some serious abuse.  Counter this by running ksoftirqd
1996         // at higher priority.
1997         if (IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) {
1998                 struct sched_param sp;
1999                 struct task_struct *t;
2000
2001                 t = per_cpu(ksoftirqd, cpu);
2002                 WARN_ON_ONCE(!t);
2003                 sp.sched_priority = 2;
2004                 sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
2005         }
2006
2007         /* Don't allow time recalculation while creating a new task. */
2008         mutex_lock(&boost_mutex);
2009         rcu_torture_disable_rt_throttle();
2010         VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
2011         boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL,
2012                                                   cpu_to_node(cpu),
2013                                                   "rcu_torture_boost");
2014         if (IS_ERR(boost_tasks[cpu])) {
2015                 retval = PTR_ERR(boost_tasks[cpu]);
2016                 VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed");
2017                 n_rcu_torture_boost_ktrerror++;
2018                 boost_tasks[cpu] = NULL;
2019                 mutex_unlock(&boost_mutex);
2020                 return retval;
2021         }
2022         kthread_bind(boost_tasks[cpu], cpu);
2023         wake_up_process(boost_tasks[cpu]);
2024         mutex_unlock(&boost_mutex);
2025         return 0;
2026 }
2027
2028 /*
2029  * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then
2030  * induces a CPU stall for the time specified by stall_cpu.
2031  */
2032 static int rcu_torture_stall(void *args)
2033 {
2034         int idx;
2035         unsigned long stop_at;
2036
2037         VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
2038         if (stall_cpu_holdoff > 0) {
2039                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
2040                 schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
2041                 VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
2042         }
2043         if (!kthread_should_stop() && stall_gp_kthread > 0) {
2044                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin GP stall");
2045                 rcu_gp_set_torture_wait(stall_gp_kthread * HZ);
2046                 for (idx = 0; idx < stall_gp_kthread + 2; idx++) {
2047                         if (kthread_should_stop())
2048                                 break;
2049                         schedule_timeout_uninterruptible(HZ);
2050                 }
2051         }
2052         if (!kthread_should_stop() && stall_cpu > 0) {
2053                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin CPU stall");
2054                 stop_at = ktime_get_seconds() + stall_cpu;
2055                 /* RCU CPU stall is expected behavior in following code. */
2056                 idx = cur_ops->readlock();
2057                 if (stall_cpu_irqsoff)
2058                         local_irq_disable();
2059                 else if (!stall_cpu_block)
2060                         preempt_disable();
2061                 pr_alert("%s start on CPU %d.\n",
2062                           __func__, raw_smp_processor_id());
2063                 while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
2064                                     stop_at))
2065                         if (stall_cpu_block) {
2066 #ifdef CONFIG_PREEMPTION
2067                                 preempt_schedule();
2068 #else
2069                                 schedule_timeout_uninterruptible(HZ);
2070 #endif
2071                         } else if (stall_no_softlockup) {
2072                                 touch_softlockup_watchdog();
2073                         }
2074                 if (stall_cpu_irqsoff)
2075                         local_irq_enable();
2076                 else if (!stall_cpu_block)
2077                         preempt_enable();
2078                 cur_ops->readunlock(idx);
2079         }
2080         pr_alert("%s end.\n", __func__);
2081         torture_shutdown_absorb("rcu_torture_stall");
2082         while (!kthread_should_stop())
2083                 schedule_timeout_interruptible(10 * HZ);
2084         return 0;
2085 }
2086
2087 /* Spawn CPU-stall kthread, if stall_cpu specified. */
2088 static int __init rcu_torture_stall_init(void)
2089 {
2090         if (stall_cpu <= 0 && stall_gp_kthread <= 0)
2091                 return 0;
2092         return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
2093 }
2094
2095 /* State structure for forward-progress self-propagating RCU callback. */
2096 struct fwd_cb_state {
2097         struct rcu_head rh;
2098         int stop;
2099 };
2100
2101 /*
2102  * Forward-progress self-propagating RCU callback function.  Because
2103  * callbacks run from softirq, this function is an implicit RCU read-side
2104  * critical section.
2105  */
2106 static void rcu_torture_fwd_prog_cb(struct rcu_head *rhp)
2107 {
2108         struct fwd_cb_state *fcsp = container_of(rhp, struct fwd_cb_state, rh);
2109
2110         if (READ_ONCE(fcsp->stop)) {
2111                 WRITE_ONCE(fcsp->stop, 2);
2112                 return;
2113         }
2114         cur_ops->call(&fcsp->rh, rcu_torture_fwd_prog_cb);
2115 }
2116
2117 /* State for continuous-flood RCU callbacks. */
2118 struct rcu_fwd_cb {
2119         struct rcu_head rh;
2120         struct rcu_fwd_cb *rfc_next;
2121         struct rcu_fwd *rfc_rfp;
2122         int rfc_gps;
2123 };
2124
2125 #define MAX_FWD_CB_JIFFIES      (8 * HZ) /* Maximum CB test duration. */
2126 #define MIN_FWD_CB_LAUNDERS     3       /* This many CB invocations to count. */
2127 #define MIN_FWD_CBS_LAUNDERED   100     /* Number of counted CBs. */
2128 #define FWD_CBS_HIST_DIV        10      /* Histogram buckets/second. */
2129 #define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))
2130
2131 struct rcu_launder_hist {
2132         long n_launders;
2133         unsigned long launder_gp_seq;
2134 };
2135
2136 struct rcu_fwd {
2137         spinlock_t rcu_fwd_lock;
2138         struct rcu_fwd_cb *rcu_fwd_cb_head;
2139         struct rcu_fwd_cb **rcu_fwd_cb_tail;
2140         long n_launders_cb;
2141         unsigned long rcu_fwd_startat;
2142         struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
2143         unsigned long rcu_launder_gp_seq_start;
2144 };
2145
2146 static DEFINE_MUTEX(rcu_fwd_mutex);
2147 static struct rcu_fwd *rcu_fwds;
2148 static bool rcu_fwd_emergency_stop;
2149
2150 static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
2151 {
2152         unsigned long gps;
2153         unsigned long gps_old;
2154         int i;
2155         int j;
2156
2157         for (i = ARRAY_SIZE(rfp->n_launders_hist) - 1; i > 0; i--)
2158                 if (rfp->n_launders_hist[i].n_launders > 0)
2159                         break;
2160         pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):",
2161                  __func__, jiffies - rfp->rcu_fwd_startat);
2162         gps_old = rfp->rcu_launder_gp_seq_start;
2163         for (j = 0; j <= i; j++) {
2164                 gps = rfp->n_launders_hist[j].launder_gp_seq;
2165                 pr_cont(" %ds/%d: %ld:%ld",
2166                         j + 1, FWD_CBS_HIST_DIV,
2167                         rfp->n_launders_hist[j].n_launders,
2168                         rcutorture_seq_diff(gps, gps_old));
2169                 gps_old = gps;
2170         }
2171         pr_cont("\n");
2172 }
2173
2174 /* Callback function for continuous-flood RCU callbacks. */
2175 static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
2176 {
2177         unsigned long flags;
2178         int i;
2179         struct rcu_fwd_cb *rfcp = container_of(rhp, struct rcu_fwd_cb, rh);
2180         struct rcu_fwd_cb **rfcpp;
2181         struct rcu_fwd *rfp = rfcp->rfc_rfp;
2182
2183         rfcp->rfc_next = NULL;
2184         rfcp->rfc_gps++;
2185         spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
2186         rfcpp = rfp->rcu_fwd_cb_tail;
2187         rfp->rcu_fwd_cb_tail = &rfcp->rfc_next;
2188         WRITE_ONCE(*rfcpp, rfcp);
2189         WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1);
2190         i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
2191         if (i >= ARRAY_SIZE(rfp->n_launders_hist))
2192                 i = ARRAY_SIZE(rfp->n_launders_hist) - 1;
2193         rfp->n_launders_hist[i].n_launders++;
2194         rfp->n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();
2195         spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
2196 }
2197
2198 // Give the scheduler a chance, even on nohz_full CPUs.
2199 static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)
2200 {
2201         if (IS_ENABLED(CONFIG_PREEMPTION) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
2202                 // Real call_rcu() floods hit userspace, so emulate that.
2203                 if (need_resched() || (iter & 0xfff))
2204                         schedule();
2205                 return;
2206         }
2207         // No userspace emulation: CB invocation throttles call_rcu()
2208         cond_resched();
2209 }
2210
2211 /*
2212  * Free all callbacks on the rcu_fwd_cb_head list, either because the
2213  * test is over or because we hit an OOM event.
2214  */
2215 static unsigned long rcu_torture_fwd_prog_cbfree(struct rcu_fwd *rfp)
2216 {
2217         unsigned long flags;
2218         unsigned long freed = 0;
2219         struct rcu_fwd_cb *rfcp;
2220
2221         for (;;) {
2222                 spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
2223                 rfcp = rfp->rcu_fwd_cb_head;
2224                 if (!rfcp) {
2225                         spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
2226                         break;
2227                 }
2228                 rfp->rcu_fwd_cb_head = rfcp->rfc_next;
2229                 if (!rfp->rcu_fwd_cb_head)
2230                         rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
2231                 spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
2232                 kfree(rfcp);
2233                 freed++;
2234                 rcu_torture_fwd_prog_cond_resched(freed);
2235                 if (tick_nohz_full_enabled()) {
2236                         local_irq_save(flags);
2237                         rcu_momentary_dyntick_idle();
2238                         local_irq_restore(flags);
2239                 }
2240         }
2241         return freed;
2242 }
2243
2244 /* Carry out need_resched()/cond_resched() forward-progress testing. */
2245 static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
2246                                     int *tested, int *tested_tries)
2247 {
2248         unsigned long cver;
2249         unsigned long dur;
2250         struct fwd_cb_state fcs;
2251         unsigned long gps;
2252         int idx;
2253         int sd;
2254         int sd4;
2255         bool selfpropcb = false;
2256         unsigned long stopat;
2257         static DEFINE_TORTURE_RANDOM(trs);
2258
2259         if (!cur_ops->sync)
2260                 return; // Cannot do need_resched() forward progress testing without ->sync.
2261         if (cur_ops->call && cur_ops->cb_barrier) {
2262                 init_rcu_head_on_stack(&fcs.rh);
2263                 selfpropcb = true;
2264         }
2265
2266         /* Tight loop containing cond_resched(). */
2267         WRITE_ONCE(rcu_fwd_cb_nodelay, true);
2268         cur_ops->sync(); /* Later readers see above write. */
2269         if  (selfpropcb) {
2270                 WRITE_ONCE(fcs.stop, 0);
2271                 cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
2272         }
2273         cver = READ_ONCE(rcu_torture_current_version);
2274         gps = cur_ops->get_gp_seq();
2275         sd = cur_ops->stall_dur() + 1;
2276         sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
2277         dur = sd4 + torture_random(&trs) % (sd - sd4);
2278         WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
2279         stopat = rfp->rcu_fwd_startat + dur;
2280         while (time_before(jiffies, stopat) &&
2281                !shutdown_time_arrived() &&
2282                !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
2283                 idx = cur_ops->readlock();
2284                 udelay(10);
2285                 cur_ops->readunlock(idx);
2286                 if (!fwd_progress_need_resched || need_resched())
2287                         cond_resched();
2288         }
2289         (*tested_tries)++;
2290         if (!time_before(jiffies, stopat) &&
2291             !shutdown_time_arrived() &&
2292             !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
2293                 (*tested)++;
2294                 cver = READ_ONCE(rcu_torture_current_version) - cver;
2295                 gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
2296                 WARN_ON(!cver && gps < 2);
2297                 pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps);
2298         }
2299         if (selfpropcb) {
2300                 WRITE_ONCE(fcs.stop, 1);
2301                 cur_ops->sync(); /* Wait for running CB to complete. */
2302                 cur_ops->cb_barrier(); /* Wait for queued callbacks. */
2303         }
2304
2305         if (selfpropcb) {
2306                 WARN_ON(READ_ONCE(fcs.stop) != 2);
2307                 destroy_rcu_head_on_stack(&fcs.rh);
2308         }
2309         schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
2310         WRITE_ONCE(rcu_fwd_cb_nodelay, false);
2311 }
2312
2313 /* Carry out call_rcu() forward-progress testing. */
2314 static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
2315 {
2316         unsigned long cver;
2317         unsigned long flags;
2318         unsigned long gps;
2319         int i;
2320         long n_launders;
2321         long n_launders_cb_snap;
2322         long n_launders_sa;
2323         long n_max_cbs;
2324         long n_max_gps;
2325         struct rcu_fwd_cb *rfcp;
2326         struct rcu_fwd_cb *rfcpn;
2327         unsigned long stopat;
2328         unsigned long stoppedat;
2329
2330         if (READ_ONCE(rcu_fwd_emergency_stop))
2331                 return; /* Get out of the way quickly, no GP wait! */
2332         if (!cur_ops->call)
2333                 return; /* Can't do call_rcu() fwd prog without ->call. */
2334
2335         /* Loop continuously posting RCU callbacks. */
2336         WRITE_ONCE(rcu_fwd_cb_nodelay, true);
2337         cur_ops->sync(); /* Later readers see above write. */
2338         WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
2339         stopat = rfp->rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
2340         n_launders = 0;
2341         rfp->n_launders_cb = 0; // Hoist initialization for multi-kthread
2342         n_launders_sa = 0;
2343         n_max_cbs = 0;
2344         n_max_gps = 0;
2345         for (i = 0; i < ARRAY_SIZE(rfp->n_launders_hist); i++)
2346                 rfp->n_launders_hist[i].n_launders = 0;
2347         cver = READ_ONCE(rcu_torture_current_version);
2348         gps = cur_ops->get_gp_seq();
2349         rfp->rcu_launder_gp_seq_start = gps;
2350         tick_dep_set_task(current, TICK_DEP_BIT_RCU);
2351         while (time_before(jiffies, stopat) &&
2352                !shutdown_time_arrived() &&
2353                !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
2354                 rfcp = READ_ONCE(rfp->rcu_fwd_cb_head);
2355                 rfcpn = NULL;
2356                 if (rfcp)
2357                         rfcpn = READ_ONCE(rfcp->rfc_next);
2358                 if (rfcpn) {
2359                         if (rfcp->rfc_gps >= MIN_FWD_CB_LAUNDERS &&
2360                             ++n_max_gps >= MIN_FWD_CBS_LAUNDERED)
2361                                 break;
2362                         rfp->rcu_fwd_cb_head = rfcpn;
2363                         n_launders++;
2364                         n_launders_sa++;
2365                 } else {
2366                         rfcp = kmalloc(sizeof(*rfcp), GFP_KERNEL);
2367                         if (WARN_ON_ONCE(!rfcp)) {
2368                                 schedule_timeout_interruptible(1);
2369                                 continue;
2370                         }
2371                         n_max_cbs++;
2372                         n_launders_sa = 0;
2373                         rfcp->rfc_gps = 0;
2374                         rfcp->rfc_rfp = rfp;
2375                 }
2376                 cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
2377                 rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
2378                 if (tick_nohz_full_enabled()) {
2379                         local_irq_save(flags);
2380                         rcu_momentary_dyntick_idle();
2381                         local_irq_restore(flags);
2382                 }
2383         }
2384         stoppedat = jiffies;
2385         n_launders_cb_snap = READ_ONCE(rfp->n_launders_cb);
2386         cver = READ_ONCE(rcu_torture_current_version) - cver;
2387         gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
2388         cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
2389         (void)rcu_torture_fwd_prog_cbfree(rfp);
2390
2391         if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop) &&
2392             !shutdown_time_arrived()) {
2393                 WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
2394                 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",
2395                          __func__,
2396                          stoppedat - rfp->rcu_fwd_startat, jiffies - stoppedat,
2397                          n_launders + n_max_cbs - n_launders_cb_snap,
2398                          n_launders, n_launders_sa,
2399                          n_max_gps, n_max_cbs, cver, gps);
2400                 rcu_torture_fwd_cb_hist(rfp);
2401         }
2402         schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
2403         tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
2404         WRITE_ONCE(rcu_fwd_cb_nodelay, false);
2405 }
2406
2407
2408 /*
2409  * OOM notifier, but this only prints diagnostic information for the
2410  * current forward-progress test.
2411  */
2412 static int rcutorture_oom_notify(struct notifier_block *self,
2413                                  unsigned long notused, void *nfreed)
2414 {
2415         struct rcu_fwd *rfp;
2416
2417         mutex_lock(&rcu_fwd_mutex);
2418         rfp = rcu_fwds;
2419         if (!rfp) {
2420                 mutex_unlock(&rcu_fwd_mutex);
2421                 return NOTIFY_OK;
2422         }
2423         WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
2424              __func__);
2425         rcu_torture_fwd_cb_hist(rfp);
2426         rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rfp->rcu_fwd_startat)) / 2);
2427         WRITE_ONCE(rcu_fwd_emergency_stop, true);
2428         smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
2429         pr_info("%s: Freed %lu RCU callbacks.\n",
2430                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
2431         rcu_barrier();
2432         pr_info("%s: Freed %lu RCU callbacks.\n",
2433                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
2434         rcu_barrier();
2435         pr_info("%s: Freed %lu RCU callbacks.\n",
2436                 __func__, rcu_torture_fwd_prog_cbfree(rfp));
2437         smp_mb(); /* Frees before return to avoid redoing OOM. */
2438         (*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */
2439         pr_info("%s returning after OOM processing.\n", __func__);
2440         mutex_unlock(&rcu_fwd_mutex);
2441         return NOTIFY_OK;
2442 }
2443
2444 static struct notifier_block rcutorture_oom_nb = {
2445         .notifier_call = rcutorture_oom_notify
2446 };
2447
2448 /* Carry out grace-period forward-progress testing. */
2449 static int rcu_torture_fwd_prog(void *args)
2450 {
2451         int oldnice = task_nice(current);
2452         struct rcu_fwd *rfp = args;
2453         int tested = 0;
2454         int tested_tries = 0;
2455
2456         VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
2457         rcu_bind_current_to_nocb();
2458         if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST))
2459                 set_user_nice(current, MAX_NICE);
2460         do {
2461                 schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
2462                 WRITE_ONCE(rcu_fwd_emergency_stop, false);
2463                 if (!IS_ENABLED(CONFIG_TINY_RCU) ||
2464                     rcu_inkernel_boot_has_ended())
2465                         rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
2466                 if (rcu_inkernel_boot_has_ended())
2467                         rcu_torture_fwd_prog_cr(rfp);
2468
2469                 /* Avoid slow periods, better to test when busy. */
2470                 if (stutter_wait("rcu_torture_fwd_prog"))
2471                         sched_set_normal(current, oldnice);
2472         } while (!torture_must_stop());
2473         /* Short runs might not contain a valid forward-progress attempt. */
2474         WARN_ON(!tested && tested_tries >= 5);
2475         pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
2476         torture_kthread_stopping("rcu_torture_fwd_prog");
2477         return 0;
2478 }
2479
2480 /* If forward-progress checking is requested and feasible, spawn the thread. */
2481 static int __init rcu_torture_fwd_prog_init(void)
2482 {
2483         struct rcu_fwd *rfp;
2484
2485         if (!fwd_progress)
2486                 return 0; /* Not requested, so don't do it. */
2487         if ((!cur_ops->sync && !cur_ops->call) ||
2488             !cur_ops->stall_dur || cur_ops->stall_dur() <= 0 || cur_ops == &rcu_busted_ops) {
2489                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
2490                 return 0;
2491         }
2492         if (stall_cpu > 0) {
2493                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
2494                 if (IS_MODULE(CONFIG_RCU_TORTURE_TESTS))
2495                         return -EINVAL; /* In module, can fail back to user. */
2496                 WARN_ON(1); /* Make sure rcutorture notices conflict. */
2497                 return 0;
2498         }
2499         if (fwd_progress_holdoff <= 0)
2500                 fwd_progress_holdoff = 1;
2501         if (fwd_progress_div <= 0)
2502                 fwd_progress_div = 4;
2503         rfp = kzalloc(sizeof(*rfp), GFP_KERNEL);
2504         if (!rfp)
2505                 return -ENOMEM;
2506         spin_lock_init(&rfp->rcu_fwd_lock);
2507         rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
2508         mutex_lock(&rcu_fwd_mutex);
2509         rcu_fwds = rfp;
2510         mutex_unlock(&rcu_fwd_mutex);
2511         register_oom_notifier(&rcutorture_oom_nb);
2512         return torture_create_kthread(rcu_torture_fwd_prog, rfp, fwd_prog_task);
2513 }
2514
2515 static void rcu_torture_fwd_prog_cleanup(void)
2516 {
2517         struct rcu_fwd *rfp;
2518
2519         torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
2520         rfp = rcu_fwds;
2521         mutex_lock(&rcu_fwd_mutex);
2522         rcu_fwds = NULL;
2523         mutex_unlock(&rcu_fwd_mutex);
2524         unregister_oom_notifier(&rcutorture_oom_nb);
2525         kfree(rfp);
2526 }
2527
2528 /* Callback function for RCU barrier testing. */
2529 static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
2530 {
2531         atomic_inc(&barrier_cbs_invoked);
2532 }
2533
2534 /* IPI handler to get callback posted on desired CPU, if online. */
2535 static void rcu_torture_barrier1cb(void *rcu_void)
2536 {
2537         struct rcu_head *rhp = rcu_void;
2538
2539         cur_ops->call(rhp, rcu_torture_barrier_cbf);
2540 }
2541
2542 /* kthread function to register callbacks used to test RCU barriers. */
2543 static int rcu_torture_barrier_cbs(void *arg)
2544 {
2545         long myid = (long)arg;
2546         bool lastphase = false;
2547         bool newphase;
2548         struct rcu_head rcu;
2549
2550         init_rcu_head_on_stack(&rcu);
2551         VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started");
2552         set_user_nice(current, MAX_NICE);
2553         do {
2554                 wait_event(barrier_cbs_wq[myid],
2555                            (newphase =
2556                             smp_load_acquire(&barrier_phase)) != lastphase ||
2557                            torture_must_stop());
2558                 lastphase = newphase;
2559                 if (torture_must_stop())
2560                         break;
2561                 /*
2562                  * The above smp_load_acquire() ensures barrier_phase load
2563                  * is ordered before the following ->call().
2564                  */
2565                 if (smp_call_function_single(myid, rcu_torture_barrier1cb,
2566                                              &rcu, 1)) {
2567                         // IPI failed, so use direct call from current CPU.
2568                         cur_ops->call(&rcu, rcu_torture_barrier_cbf);
2569                 }
2570                 if (atomic_dec_and_test(&barrier_cbs_count))
2571                         wake_up(&barrier_wq);
2572         } while (!torture_must_stop());
2573         if (cur_ops->cb_barrier != NULL)
2574                 cur_ops->cb_barrier();
2575         destroy_rcu_head_on_stack(&rcu);
2576         torture_kthread_stopping("rcu_torture_barrier_cbs");
2577         return 0;
2578 }
2579
2580 /* kthread function to drive and coordinate RCU barrier testing. */
2581 static int rcu_torture_barrier(void *arg)
2582 {
2583         int i;
2584
2585         VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting");
2586         do {
2587                 atomic_set(&barrier_cbs_invoked, 0);
2588                 atomic_set(&barrier_cbs_count, n_barrier_cbs);
2589                 /* Ensure barrier_phase ordered after prior assignments. */
2590                 smp_store_release(&barrier_phase, !barrier_phase);
2591                 for (i = 0; i < n_barrier_cbs; i++)
2592                         wake_up(&barrier_cbs_wq[i]);
2593                 wait_event(barrier_wq,
2594                            atomic_read(&barrier_cbs_count) == 0 ||
2595                            torture_must_stop());
2596                 if (torture_must_stop())
2597                         break;
2598                 n_barrier_attempts++;
2599                 cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
2600                 if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
2601                         n_rcu_torture_barrier_error++;
2602                         pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
2603                                atomic_read(&barrier_cbs_invoked),
2604                                n_barrier_cbs);
2605                         WARN_ON(1);
2606                         // Wait manually for the remaining callbacks
2607                         i = 0;
2608                         do {
2609                                 if (WARN_ON(i++ > HZ))
2610                                         i = INT_MIN;
2611                                 schedule_timeout_interruptible(1);
2612                                 cur_ops->cb_barrier();
2613                         } while (atomic_read(&barrier_cbs_invoked) !=
2614                                  n_barrier_cbs &&
2615                                  !torture_must_stop());
2616                         smp_mb(); // Can't trust ordering if broken.
2617                         if (!torture_must_stop())
2618                                 pr_err("Recovered: barrier_cbs_invoked = %d\n",
2619                                        atomic_read(&barrier_cbs_invoked));
2620                 } else {
2621                         n_barrier_successes++;
2622                 }
2623                 schedule_timeout_interruptible(HZ / 10);
2624         } while (!torture_must_stop());
2625         torture_kthread_stopping("rcu_torture_barrier");
2626         return 0;
2627 }
2628
2629 /* Initialize RCU barrier testing. */
2630 static int rcu_torture_barrier_init(void)
2631 {
2632         int i;
2633         int ret;
2634
2635         if (n_barrier_cbs <= 0)
2636                 return 0;
2637         if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
2638                 pr_alert("%s" TORTURE_FLAG
2639                          " Call or barrier ops missing for %s,\n",
2640                          torture_type, cur_ops->name);
2641                 pr_alert("%s" TORTURE_FLAG
2642                          " RCU barrier testing omitted from run.\n",
2643                          torture_type);
2644                 return 0;
2645         }
2646         atomic_set(&barrier_cbs_count, 0);
2647         atomic_set(&barrier_cbs_invoked, 0);
2648         barrier_cbs_tasks =
2649                 kcalloc(n_barrier_cbs, sizeof(barrier_cbs_tasks[0]),
2650                         GFP_KERNEL);
2651         barrier_cbs_wq =
2652                 kcalloc(n_barrier_cbs, sizeof(barrier_cbs_wq[0]), GFP_KERNEL);
2653         if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
2654                 return -ENOMEM;
2655         for (i = 0; i < n_barrier_cbs; i++) {
2656                 init_waitqueue_head(&barrier_cbs_wq[i]);
2657                 ret = torture_create_kthread(rcu_torture_barrier_cbs,
2658                                              (void *)(long)i,
2659                                              barrier_cbs_tasks[i]);
2660                 if (ret)
2661                         return ret;
2662         }
2663         return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task);
2664 }
2665
2666 /* Clean up after RCU barrier testing. */
2667 static void rcu_torture_barrier_cleanup(void)
2668 {
2669         int i;
2670
2671         torture_stop_kthread(rcu_torture_barrier, barrier_task);
2672         if (barrier_cbs_tasks != NULL) {
2673                 for (i = 0; i < n_barrier_cbs; i++)
2674                         torture_stop_kthread(rcu_torture_barrier_cbs,
2675                                              barrier_cbs_tasks[i]);
2676                 kfree(barrier_cbs_tasks);
2677                 barrier_cbs_tasks = NULL;
2678         }
2679         if (barrier_cbs_wq != NULL) {
2680                 kfree(barrier_cbs_wq);
2681                 barrier_cbs_wq = NULL;
2682         }
2683 }
2684
2685 static bool rcu_torture_can_boost(void)
2686 {
2687         static int boost_warn_once;
2688         int prio;
2689
2690         if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2)
2691                 return false;
2692         if (!cur_ops->start_gp_poll || !cur_ops->poll_gp_state)
2693                 return false;
2694
2695         prio = rcu_get_gp_kthreads_prio();
2696         if (!prio)
2697                 return false;
2698
2699         if (prio < 2) {
2700                 if (boost_warn_once == 1)
2701                         return false;
2702
2703                 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);
2704                 boost_warn_once = 1;
2705                 return false;
2706         }
2707
2708         return true;
2709 }
2710
2711 static bool read_exit_child_stop;
2712 static bool read_exit_child_stopped;
2713 static wait_queue_head_t read_exit_wq;
2714
2715 // Child kthread which just does an rcutorture reader and exits.
2716 static int rcu_torture_read_exit_child(void *trsp_in)
2717 {
2718         struct torture_random_state *trsp = trsp_in;
2719
2720         set_user_nice(current, MAX_NICE);
2721         // Minimize time between reading and exiting.
2722         while (!kthread_should_stop())
2723                 schedule_timeout_uninterruptible(1);
2724         (void)rcu_torture_one_read(trsp, -1);
2725         return 0;
2726 }
2727
2728 // Parent kthread which creates and destroys read-exit child kthreads.
2729 static int rcu_torture_read_exit(void *unused)
2730 {
2731         int count = 0;
2732         bool errexit = false;
2733         int i;
2734         struct task_struct *tsp;
2735         DEFINE_TORTURE_RANDOM(trs);
2736
2737         // Allocate and initialize.
2738         set_user_nice(current, MAX_NICE);
2739         VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of test");
2740
2741         // Each pass through this loop does one read-exit episode.
2742         do {
2743                 if (++count > read_exit_burst) {
2744                         VERBOSE_TOROUT_STRING("rcu_torture_read_exit: End of episode");
2745                         rcu_barrier(); // Wait for task_struct free, avoid OOM.
2746                         for (i = 0; i < read_exit_delay; i++) {
2747                                 schedule_timeout_uninterruptible(HZ);
2748                                 if (READ_ONCE(read_exit_child_stop))
2749                                         break;
2750                         }
2751                         if (!READ_ONCE(read_exit_child_stop))
2752                                 VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of episode");
2753                         count = 0;
2754                 }
2755                 if (READ_ONCE(read_exit_child_stop))
2756                         break;
2757                 // Spawn child.
2758                 tsp = kthread_run(rcu_torture_read_exit_child,
2759                                      &trs, "%s",
2760                                      "rcu_torture_read_exit_child");
2761                 if (IS_ERR(tsp)) {
2762                         VERBOSE_TOROUT_ERRSTRING("out of memory");
2763                         errexit = true;
2764                         tsp = NULL;
2765                         break;
2766                 }
2767                 cond_resched();
2768                 kthread_stop(tsp);
2769                 n_read_exits ++;
2770                 stutter_wait("rcu_torture_read_exit");
2771         } while (!errexit && !READ_ONCE(read_exit_child_stop));
2772
2773         // Clean up and exit.
2774         smp_store_release(&read_exit_child_stopped, true); // After reaping.
2775         smp_mb(); // Store before wakeup.
2776         wake_up(&read_exit_wq);
2777         while (!torture_must_stop())
2778                 schedule_timeout_uninterruptible(1);
2779         torture_kthread_stopping("rcu_torture_read_exit");
2780         return 0;
2781 }
2782
2783 static int rcu_torture_read_exit_init(void)
2784 {
2785         if (read_exit_burst <= 0)
2786                 return -EINVAL;
2787         init_waitqueue_head(&read_exit_wq);
2788         read_exit_child_stop = false;
2789         read_exit_child_stopped = false;
2790         return torture_create_kthread(rcu_torture_read_exit, NULL,
2791                                       read_exit_task);
2792 }
2793
2794 static void rcu_torture_read_exit_cleanup(void)
2795 {
2796         if (!read_exit_task)
2797                 return;
2798         WRITE_ONCE(read_exit_child_stop, true);
2799         smp_mb(); // Above write before wait.
2800         wait_event(read_exit_wq, smp_load_acquire(&read_exit_child_stopped));
2801         torture_stop_kthread(rcutorture_read_exit, read_exit_task);
2802 }
2803
2804 static enum cpuhp_state rcutor_hp;
2805
2806 static void
2807 rcu_torture_cleanup(void)
2808 {
2809         int firsttime;
2810         int flags = 0;
2811         unsigned long gp_seq = 0;
2812         int i;
2813
2814         if (torture_cleanup_begin()) {
2815                 if (cur_ops->cb_barrier != NULL)
2816                         cur_ops->cb_barrier();
2817                 return;
2818         }
2819         if (!cur_ops) {
2820                 torture_cleanup_end();
2821                 return;
2822         }
2823
2824         if (cur_ops->gp_kthread_dbg)
2825                 cur_ops->gp_kthread_dbg();
2826         rcu_torture_read_exit_cleanup();
2827         rcu_torture_barrier_cleanup();
2828         rcu_torture_fwd_prog_cleanup();
2829         torture_stop_kthread(rcu_torture_stall, stall_task);
2830         torture_stop_kthread(rcu_torture_writer, writer_task);
2831
2832         if (nocb_tasks) {
2833                 for (i = 0; i < nrealnocbers; i++)
2834                         torture_stop_kthread(rcu_nocb_toggle, nocb_tasks[i]);
2835                 kfree(nocb_tasks);
2836                 nocb_tasks = NULL;
2837         }
2838
2839         if (reader_tasks) {
2840                 for (i = 0; i < nrealreaders; i++)
2841                         torture_stop_kthread(rcu_torture_reader,
2842                                              reader_tasks[i]);
2843                 kfree(reader_tasks);
2844                 reader_tasks = NULL;
2845         }
2846         kfree(rcu_torture_reader_mbchk);
2847         rcu_torture_reader_mbchk = NULL;
2848
2849         if (fakewriter_tasks) {
2850                 for (i = 0; i < nfakewriters; i++)
2851                         torture_stop_kthread(rcu_torture_fakewriter,
2852                                              fakewriter_tasks[i]);
2853                 kfree(fakewriter_tasks);
2854                 fakewriter_tasks = NULL;
2855         }
2856
2857         rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
2858         srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
2859         pr_alert("%s:  End-test grace-period state: g%ld f%#x total-gps=%ld\n",
2860                  cur_ops->name, (long)gp_seq, flags,
2861                  rcutorture_seq_diff(gp_seq, start_gp_seq));
2862         torture_stop_kthread(rcu_torture_stats, stats_task);
2863         torture_stop_kthread(rcu_torture_fqs, fqs_task);
2864         if (rcu_torture_can_boost() && rcutor_hp >= 0)
2865                 cpuhp_remove_state(rcutor_hp);
2866
2867         /*
2868          * Wait for all RCU callbacks to fire, then do torture-type-specific
2869          * cleanup operations.
2870          */
2871         if (cur_ops->cb_barrier != NULL)
2872                 cur_ops->cb_barrier();
2873         if (cur_ops->cleanup != NULL)
2874                 cur_ops->cleanup();
2875
2876         rcu_torture_mem_dump_obj();
2877
2878         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
2879
2880         if (err_segs_recorded) {
2881                 pr_alert("Failure/close-call rcutorture reader segments:\n");
2882                 if (rt_read_nsegs == 0)
2883                         pr_alert("\t: No segments recorded!!!\n");
2884                 firsttime = 1;
2885                 for (i = 0; i < rt_read_nsegs; i++) {
2886                         pr_alert("\t%d: %#x ", i, err_segs[i].rt_readstate);
2887                         if (err_segs[i].rt_delay_jiffies != 0) {
2888                                 pr_cont("%s%ldjiffies", firsttime ? "" : "+",
2889                                         err_segs[i].rt_delay_jiffies);
2890                                 firsttime = 0;
2891                         }
2892                         if (err_segs[i].rt_delay_ms != 0) {
2893                                 pr_cont("%s%ldms", firsttime ? "" : "+",
2894                                         err_segs[i].rt_delay_ms);
2895                                 firsttime = 0;
2896                         }
2897                         if (err_segs[i].rt_delay_us != 0) {
2898                                 pr_cont("%s%ldus", firsttime ? "" : "+",
2899                                         err_segs[i].rt_delay_us);
2900                                 firsttime = 0;
2901                         }
2902                         pr_cont("%s\n",
2903                                 err_segs[i].rt_preempted ? "preempted" : "");
2904
2905                 }
2906         }
2907         if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
2908                 rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
2909         else if (torture_onoff_failures())
2910                 rcu_torture_print_module_parms(cur_ops,
2911                                                "End of test: RCU_HOTPLUG");
2912         else
2913                 rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
2914         torture_cleanup_end();
2915 }
2916
2917 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
2918 static void rcu_torture_leak_cb(struct rcu_head *rhp)
2919 {
2920 }
2921
2922 static void rcu_torture_err_cb(struct rcu_head *rhp)
2923 {
2924         /*
2925          * This -might- happen due to race conditions, but is unlikely.
2926          * The scenario that leads to this happening is that the
2927          * first of the pair of duplicate callbacks is queued,
2928          * someone else starts a grace period that includes that
2929          * callback, then the second of the pair must wait for the
2930          * next grace period.  Unlikely, but can happen.  If it
2931          * does happen, the debug-objects subsystem won't have splatted.
2932          */
2933         pr_alert("%s: duplicated callback was invoked.\n", KBUILD_MODNAME);
2934 }
2935 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2936
2937 /*
2938  * Verify that double-free causes debug-objects to complain, but only
2939  * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.  Otherwise, say that the test
2940  * cannot be carried out.
2941  */
2942 static void rcu_test_debug_objects(void)
2943 {
2944 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
2945         struct rcu_head rh1;
2946         struct rcu_head rh2;
2947         struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
2948
2949         init_rcu_head_on_stack(&rh1);
2950         init_rcu_head_on_stack(&rh2);
2951         pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME);
2952
2953         /* Try to queue the rh2 pair of callbacks for the same grace period. */
2954         preempt_disable(); /* Prevent preemption from interrupting test. */
2955         rcu_read_lock(); /* Make it impossible to finish a grace period. */
2956         call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */
2957         local_irq_disable(); /* Make it harder to start a new grace period. */
2958         call_rcu(&rh2, rcu_torture_leak_cb);
2959         call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
2960         if (rhp) {
2961                 call_rcu(rhp, rcu_torture_leak_cb);
2962                 call_rcu(rhp, rcu_torture_err_cb); /* Another duplicate callback. */
2963         }
2964         local_irq_enable();
2965         rcu_read_unlock();
2966         preempt_enable();
2967
2968         /* Wait for them all to get done so we can safely return. */
2969         rcu_barrier();
2970         pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
2971         destroy_rcu_head_on_stack(&rh1);
2972         destroy_rcu_head_on_stack(&rh2);
2973 #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2974         pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
2975 #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
2976 }
2977
2978 static void rcutorture_sync(void)
2979 {
2980         static unsigned long n;
2981
2982         if (cur_ops->sync && !(++n & 0xfff))
2983                 cur_ops->sync();
2984 }
2985
2986 static int __init
2987 rcu_torture_init(void)
2988 {
2989         long i;
2990         int cpu;
2991         int firsterr = 0;
2992         int flags = 0;
2993         unsigned long gp_seq = 0;
2994         static struct rcu_torture_ops *torture_ops[] = {
2995                 &rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
2996                 &busted_srcud_ops, &tasks_ops, &tasks_rude_ops,
2997                 &tasks_tracing_ops, &trivial_ops,
2998         };
2999
3000         if (!torture_init_begin(torture_type, verbose))
3001                 return -EBUSY;
3002
3003         /* Process args and tell the world that the torturer is on the job. */
3004         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
3005                 cur_ops = torture_ops[i];
3006                 if (strcmp(torture_type, cur_ops->name) == 0)
3007                         break;
3008         }
3009         if (i == ARRAY_SIZE(torture_ops)) {
3010                 pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
3011                          torture_type);
3012                 pr_alert("rcu-torture types:");
3013                 for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
3014                         pr_cont(" %s", torture_ops[i]->name);
3015                 pr_cont("\n");
3016                 firsterr = -EINVAL;
3017                 cur_ops = NULL;
3018                 goto unwind;
3019         }
3020         if (cur_ops->fqs == NULL && fqs_duration != 0) {
3021                 pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
3022                 fqs_duration = 0;
3023         }
3024         if (cur_ops->init)
3025                 cur_ops->init();
3026
3027         if (nreaders >= 0) {
3028                 nrealreaders = nreaders;
3029         } else {
3030                 nrealreaders = num_online_cpus() - 2 - nreaders;
3031                 if (nrealreaders <= 0)
3032                         nrealreaders = 1;
3033         }
3034         rcu_torture_print_module_parms(cur_ops, "Start of test");
3035         rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
3036         srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
3037         start_gp_seq = gp_seq;
3038         pr_alert("%s:  Start-test grace-period state: g%ld f%#x\n",
3039                  cur_ops->name, (long)gp_seq, flags);
3040
3041         /* Set up the freelist. */
3042
3043         INIT_LIST_HEAD(&rcu_torture_freelist);
3044         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
3045                 rcu_tortures[i].rtort_mbtest = 0;
3046                 list_add_tail(&rcu_tortures[i].rtort_free,
3047                               &rcu_torture_freelist);
3048         }
3049
3050         /* Initialize the statistics so that each run gets its own numbers. */
3051
3052         rcu_torture_current = NULL;
3053         rcu_torture_current_version = 0;
3054         atomic_set(&n_rcu_torture_alloc, 0);
3055         atomic_set(&n_rcu_torture_alloc_fail, 0);
3056         atomic_set(&n_rcu_torture_free, 0);
3057         atomic_set(&n_rcu_torture_mberror, 0);
3058         atomic_set(&n_rcu_torture_mbchk_fail, 0);
3059         atomic_set(&n_rcu_torture_mbchk_tries, 0);
3060         atomic_set(&n_rcu_torture_error, 0);
3061         n_rcu_torture_barrier_error = 0;
3062         n_rcu_torture_boost_ktrerror = 0;
3063         n_rcu_torture_boost_rterror = 0;
3064         n_rcu_torture_boost_failure = 0;
3065         n_rcu_torture_boosts = 0;
3066         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
3067                 atomic_set(&rcu_torture_wcount[i], 0);
3068         for_each_possible_cpu(cpu) {
3069                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
3070                         per_cpu(rcu_torture_count, cpu)[i] = 0;
3071                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
3072                 }
3073         }
3074         err_segs_recorded = 0;
3075         rt_read_nsegs = 0;
3076
3077         /* Start up the kthreads. */
3078
3079         rcu_torture_write_types();
3080         firsterr = torture_create_kthread(rcu_torture_writer, NULL,
3081                                           writer_task);
3082         if (torture_init_error(firsterr))
3083                 goto unwind;
3084         if (nfakewriters > 0) {
3085                 fakewriter_tasks = kcalloc(nfakewriters,
3086                                            sizeof(fakewriter_tasks[0]),
3087                                            GFP_KERNEL);
3088                 if (fakewriter_tasks == NULL) {
3089                         VERBOSE_TOROUT_ERRSTRING("out of memory");
3090                         firsterr = -ENOMEM;
3091                         goto unwind;
3092                 }
3093         }
3094         for (i = 0; i < nfakewriters; i++) {
3095                 firsterr = torture_create_kthread(rcu_torture_fakewriter,
3096                                                   NULL, fakewriter_tasks[i]);
3097                 if (torture_init_error(firsterr))
3098                         goto unwind;
3099         }
3100         reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
3101                                GFP_KERNEL);
3102         rcu_torture_reader_mbchk = kcalloc(nrealreaders, sizeof(*rcu_torture_reader_mbchk),
3103                                            GFP_KERNEL);
3104         if (!reader_tasks || !rcu_torture_reader_mbchk) {
3105                 VERBOSE_TOROUT_ERRSTRING("out of memory");
3106                 firsterr = -ENOMEM;
3107                 goto unwind;
3108         }
3109         for (i = 0; i < nrealreaders; i++) {
3110                 rcu_torture_reader_mbchk[i].rtc_chkrdr = -1;
3111                 firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
3112                                                   reader_tasks[i]);
3113                 if (torture_init_error(firsterr))
3114                         goto unwind;
3115         }
3116         nrealnocbers = nocbs_nthreads;
3117         if (WARN_ON(nrealnocbers < 0))
3118                 nrealnocbers = 1;
3119         if (WARN_ON(nocbs_toggle < 0))
3120                 nocbs_toggle = HZ;
3121         if (nrealnocbers > 0) {
3122                 nocb_tasks = kcalloc(nrealnocbers, sizeof(nocb_tasks[0]), GFP_KERNEL);
3123                 if (nocb_tasks == NULL) {
3124                         VERBOSE_TOROUT_ERRSTRING("out of memory");
3125                         firsterr = -ENOMEM;
3126                         goto unwind;
3127                 }
3128         } else {
3129                 nocb_tasks = NULL;
3130         }
3131         for (i = 0; i < nrealnocbers; i++) {
3132                 firsterr = torture_create_kthread(rcu_nocb_toggle, NULL, nocb_tasks[i]);
3133                 if (torture_init_error(firsterr))
3134                         goto unwind;
3135         }
3136         if (stat_interval > 0) {
3137                 firsterr = torture_create_kthread(rcu_torture_stats, NULL,
3138                                                   stats_task);
3139                 if (torture_init_error(firsterr))
3140                         goto unwind;
3141         }
3142         if (test_no_idle_hz && shuffle_interval > 0) {
3143                 firsterr = torture_shuffle_init(shuffle_interval * HZ);
3144                 if (torture_init_error(firsterr))
3145                         goto unwind;
3146         }
3147         if (stutter < 0)
3148                 stutter = 0;
3149         if (stutter) {
3150                 int t;
3151
3152                 t = cur_ops->stall_dur ? cur_ops->stall_dur() : stutter * HZ;
3153                 firsterr = torture_stutter_init(stutter * HZ, t);
3154                 if (torture_init_error(firsterr))
3155                         goto unwind;
3156         }
3157         if (fqs_duration < 0)
3158                 fqs_duration = 0;
3159         if (fqs_duration) {
3160                 /* Create the fqs thread */
3161                 firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
3162                                                   fqs_task);
3163                 if (torture_init_error(firsterr))
3164                         goto unwind;
3165         }
3166         if (test_boost_interval < 1)
3167                 test_boost_interval = 1;
3168         if (test_boost_duration < 2)
3169                 test_boost_duration = 2;
3170         if (rcu_torture_can_boost()) {
3171
3172                 boost_starttime = jiffies + test_boost_interval * HZ;
3173
3174                 firsterr = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "RCU_TORTURE",
3175                                              rcutorture_booster_init,
3176                                              rcutorture_booster_cleanup);
3177                 rcutor_hp = firsterr;
3178                 if (torture_init_error(firsterr))
3179                         goto unwind;
3180         }
3181         shutdown_jiffies = jiffies + shutdown_secs * HZ;
3182         firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
3183         if (torture_init_error(firsterr))
3184                 goto unwind;
3185         firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval,
3186                                       rcutorture_sync);
3187         if (torture_init_error(firsterr))
3188                 goto unwind;
3189         firsterr = rcu_torture_stall_init();
3190         if (torture_init_error(firsterr))
3191                 goto unwind;
3192         firsterr = rcu_torture_fwd_prog_init();
3193         if (torture_init_error(firsterr))
3194                 goto unwind;
3195         firsterr = rcu_torture_barrier_init();
3196         if (torture_init_error(firsterr))
3197                 goto unwind;
3198         firsterr = rcu_torture_read_exit_init();
3199         if (torture_init_error(firsterr))
3200                 goto unwind;
3201         if (object_debug)
3202                 rcu_test_debug_objects();
3203         torture_init_end();
3204         return 0;
3205
3206 unwind:
3207         torture_init_end();
3208         rcu_torture_cleanup();
3209         if (shutdown_secs) {
3210                 WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
3211                 kernel_power_off();
3212         }
3213         return firsterr;
3214 }
3215
3216 module_init(rcu_torture_init);
3217 module_exit(rcu_torture_cleanup);