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_1   8      /* Put SRCU index in upper bits. */
  58 #define RCUTORTURE_RDR_MASK_1    (1 << RCUTORTURE_RDR_SHIFT_1)
  59 #define RCUTORTURE_RDR_SHIFT_2   9      /* Put SRCU index in upper bits. */
  60 #define RCUTORTURE_RDR_MASK_2    (1 << RCUTORTURE_RDR_SHIFT_2)
  61 #define RCUTORTURE_RDR_BH        0x01   /* Extend readers by disabling bh. */
  62 #define RCUTORTURE_RDR_IRQ       0x02   /*  ... disabling interrupts. */
  63 #define RCUTORTURE_RDR_PREEMPT   0x04   /*  ... disabling preemption. */
  64 #define RCUTORTURE_RDR_RBH       0x08   /*  ... rcu_read_lock_bh(). */
  65 #define RCUTORTURE_RDR_SCHED     0x10   /*  ... rcu_read_lock_sched(). */
  66 #define RCUTORTURE_RDR_RCU_1     0x20   /*  ... entering another RCU reader. */
  67 #define RCUTORTURE_RDR_RCU_2     0x40   /*  ... entering another RCU reader. */
  68 #define RCUTORTURE_RDR_NBITS     7      /* Number of bits defined above. */
  69 #define RCUTORTURE_MAX_EXTEND    \
  70         (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
  71          RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
  72 #define RCUTORTURE_RDR_MAX_LOOPS 0x7    /* Maximum reader extensions. */
  73                                         /* Must be power of two minus one. */
  74 #define RCUTORTURE_RDR_MAX_SEGS (RCUTORTURE_RDR_MAX_LOOPS + 3)
  75
  76 torture_param(int, extendables, RCUTORTURE_MAX_EXTEND,
  77               "Extend readers by disabling bh (1), irqs (2), or preempt (4)");
  78 torture_param(int, fqs_duration, 0,
  79               "Duration of fqs bursts (us), 0 to disable");
  80 torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
  81 torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
  82 torture_param(int, fwd_progress, 1, "Test grace-period forward progress");
  83 torture_param(int, fwd_progress_div, 4, "Fraction of CPU stall to wait");
  84 torture_param(int, fwd_progress_holdoff, 60,
  85               "Time between forward-progress tests (s)");
  86 torture_param(bool, fwd_progress_need_resched, 1,
  87               "Hide cond_resched() behind need_resched()");
  88 torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
  89 torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
  90 torture_param(bool, gp_normal, false,
  91              "Use normal (non-expedited) GP wait primitives");
  92 torture_param(bool, gp_poll, false, "Use polling GP wait primitives");
  93 torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
  94 torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
  95 torture_param(int, leakpointer, 0, "Leak pointer dereferences from readers");
  96 torture_param(int, n_barrier_cbs, 0,
  97              "# of callbacks/kthreads for barrier testing");
  98 torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
  99 torture_param(int, nreaders, -1, "Number of RCU reader threads");
 100 torture_param(int, object_debug, 0,
 101              "Enable debug-object double call_rcu() testing");
 102 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
 103 torture_param(int, onoff_interval, 0,
 104              "Time between CPU hotplugs (jiffies), 0=disable");
 105 torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disable");
 106 torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
 107 torture_param(int, read_exit_delay, 13,
 108               "Delay between read-then-exit episodes (s)");
 109 torture_param(int, read_exit_burst, 16,
 110               "# of read-then-exit bursts per episode, zero to disable");
 111 torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
 112 torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
 113 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
 114 torture_param(int, stall_cpu_holdoff, 10,
 115              "Time to wait before starting stall (s).");
 116 torture_param(bool, stall_no_softlockup, false,
 117              "Avoid softlockup warning during cpu stall.");
 118 torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
 119 torture_param(int, stall_cpu_block, 0, "Sleep while stalling.");
 120 torture_param(int, stall_gp_kthread, 0,
 121               "Grace-period kthread stall duration (s).");
 122 torture_param(int, stat_interval, 60,
 123              "Number of seconds between stats printk()s");
 124 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
 125 torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
 126 torture_param(int, test_boost_duration, 4,
 127              "Duration of each boost test, seconds.");
 128 torture_param(int, test_boost_interval, 7,
 129              "Interval between boost tests, seconds.");
 130 torture_param(bool, test_no_idle_hz, true,
 131              "Test support for tickless idle CPUs");
 132 torture_param(int, verbose, 1,
 133              "Enable verbose debugging printk()s");
 134
 135 static char *torture_type = "rcu";
 136 module_param(torture_type, charp, 0444);
 137 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");
 138
 139 static int nrealnocbers;
 140 static int nrealreaders;
 141 static struct task_struct *writer_task;
 142 static struct task_struct **fakewriter_tasks;
 143 static struct task_struct **reader_tasks;
 144 static struct task_struct **nocb_tasks;
 145 static struct task_struct *stats_task;
 146 static struct task_struct *fqs_task;
 147 static struct task_struct *boost_tasks[NR_CPUS];
 148 static struct task_struct *stall_task;
 149 static struct task_struct **fwd_prog_tasks;
 150 static struct task_struct **barrier_cbs_tasks;
 151 static struct task_struct *barrier_task;
 152 static struct task_struct *read_exit_task;
 153
 154 #define RCU_TORTURE_PIPE_LEN 10
 155
 156 // Mailbox-like structure to check RCU global memory ordering.
 157 struct rcu_torture_reader_check {
 158         unsigned long rtc_myloops;
 159         int rtc_chkrdr;
 160         unsigned long rtc_chkloops;
 161         int rtc_ready;
 162         struct rcu_torture_reader_check *rtc_assigner;
 163 } ____cacheline_internodealigned_in_smp;
 164
 165 // Update-side data structure used to check RCU readers.
 166 struct rcu_torture {
 167         struct rcu_head rtort_rcu;
 168         int rtort_pipe_count;
 169         struct list_head rtort_free;
 170         int rtort_mbtest;
 171         struct rcu_torture_reader_check *rtort_chkp;
 172 };
 173
 174 static LIST_HEAD(rcu_torture_freelist);
 175 static struct rcu_torture __rcu *rcu_torture_current;
 176 static unsigned long rcu_torture_current_version;
 177 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 178 static DEFINE_SPINLOCK(rcu_torture_lock);
 179 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
 180 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
 181 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 182 static struct rcu_torture_reader_check *rcu_torture_reader_mbchk;
 183 static atomic_t n_rcu_torture_alloc;
 184 static atomic_t n_rcu_torture_alloc_fail;
 185 static atomic_t n_rcu_torture_free;
 186 static atomic_t n_rcu_torture_mberror;
 187 static atomic_t n_rcu_torture_mbchk_fail;
 188 static atomic_t n_rcu_torture_mbchk_tries;
 189 static atomic_t n_rcu_torture_error;
 190 static long n_rcu_torture_barrier_error;
 191 static long n_rcu_torture_boost_ktrerror;
 192 static long n_rcu_torture_boost_rterror;
 193 static long n_rcu_torture_boost_failure;
 194 static long n_rcu_torture_boosts;
 195 static atomic_long_t n_rcu_torture_timers;
 196 static long n_barrier_attempts;
 197 static long n_barrier_successes; /* did rcu_barrier test succeed? */
 198 static unsigned long n_read_exits;
 199 static struct list_head rcu_torture_removed;
 200 static unsigned long shutdown_jiffies;
 201 static unsigned long start_gp_seq;
 202 static atomic_long_t n_nocb_offload;
 203 static atomic_long_t n_nocb_deoffload;
 204
 205 static int rcu_torture_writer_state;
 206 #define RTWS_FIXED_DELAY        0
 207 #define RTWS_DELAY              1
 208 #define RTWS_REPLACE            2
 209 #define RTWS_DEF_FREE           3
 210 #define RTWS_EXP_SYNC           4
 211 #define RTWS_COND_GET           5
 212 #define RTWS_COND_SYNC          6
 213 #define RTWS_POLL_GET           7
 214 #define RTWS_POLL_WAIT          8
 215 #define RTWS_SYNC               9
 216 #define RTWS_STUTTER            10
 217 #define RTWS_STOPPING           11
 218 static const char * const rcu_torture_writer_state_names[] = {
 219         "RTWS_FIXED_DELAY",
 220         "RTWS_DELAY",
 221         "RTWS_REPLACE",
 222         "RTWS_DEF_FREE",
 223         "RTWS_EXP_SYNC",
 224         "RTWS_COND_GET",
 225         "RTWS_COND_SYNC",
 226         "RTWS_POLL_GET",
 227         "RTWS_POLL_WAIT",
 228         "RTWS_SYNC",
 229         "RTWS_STUTTER",
 230         "RTWS_STOPPING",
 231 };
 232
 233 /* Record reader segment types and duration for first failing read. */
 234 struct rt_read_seg {
 235         int rt_readstate;
 236         unsigned long rt_delay_jiffies;
 237         unsigned long rt_delay_ms;
 238         unsigned long rt_delay_us;
 239         bool rt_preempted;
 240 };
 241 static int err_segs_recorded;
 242 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
 243 static int rt_read_nsegs;
 244
 245 static const char *rcu_torture_writer_state_getname(void)
 246 {
 247         unsigned int i = READ_ONCE(rcu_torture_writer_state);
 248
 249         if (i >= ARRAY_SIZE(rcu_torture_writer_state_names))
 250                 return "???";
 251         return rcu_torture_writer_state_names[i];
 252 }
 253
 254 #ifdef CONFIG_RCU_TRACE
 255 static u64 notrace rcu_trace_clock_local(void)
 256 {
 257         u64 ts = trace_clock_local();
 258
 259         (void)do_div(ts, NSEC_PER_USEC);
 260         return ts;
 261 }
 262 #else /* #ifdef CONFIG_RCU_TRACE */
 263 static u64 notrace rcu_trace_clock_local(void)
 264 {
 265         return 0ULL;
 266 }
 267 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 268
 269 /*
 270  * Stop aggressive CPU-hog tests a bit before the end of the test in order
 271  * to avoid interfering with test shutdown.
 272  */
 273 static bool shutdown_time_arrived(void)
 274 {
 275         return shutdown_secs && time_after(jiffies, shutdown_jiffies - 30 * HZ);
 276 }
 277
 278 static unsigned long boost_starttime;   /* jiffies of next boost test start. */
 279 static DEFINE_MUTEX(boost_mutex);       /* protect setting boost_starttime */
 280                                         /*  and boost task create/destroy. */
 281 static atomic_t barrier_cbs_count;      /* Barrier callbacks registered. */
 282 static bool barrier_phase;              /* Test phase. */
 283 static atomic_t barrier_cbs_invoked;    /* Barrier callbacks invoked. */
 284 static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
 285 static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
 286
 287 static bool rcu_fwd_cb_nodelay;         /* Short rcu_torture_delay() delays. */
 288
 289 /*
 290  * Allocate an element from the rcu_tortures pool.
 291  */
 292 static struct rcu_torture *
 293 rcu_torture_alloc(void)
 294 {
 295         struct list_head *p;
 296
 297         spin_lock_bh(&rcu_torture_lock);
 298         if (list_empty(&rcu_torture_freelist)) {
 299                 atomic_inc(&n_rcu_torture_alloc_fail);
 300                 spin_unlock_bh(&rcu_torture_lock);
 301                 return NULL;
 302         }
 303         atomic_inc(&n_rcu_torture_alloc);
 304         p = rcu_torture_freelist.next;
 305         list_del_init(p);
 306         spin_unlock_bh(&rcu_torture_lock);
 307         return container_of(p, struct rcu_torture, rtort_free);
 308 }
 309
 310 /*
 311  * Free an element to the rcu_tortures pool.
 312  */
 313 static void
 314 rcu_torture_free(struct rcu_torture *p)
 315 {
 316         atomic_inc(&n_rcu_torture_free);
 317         spin_lock_bh(&rcu_torture_lock);
 318         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 319         spin_unlock_bh(&rcu_torture_lock);
 320 }
 321
 322 /*
 323  * Operations vector for selecting different types of tests.
 324  */
 325
 326 struct rcu_torture_ops {
 327         int ttype;
 328         void (*init)(void);
 329         void (*cleanup)(void);
 330         int (*readlock)(void);
 331         void (*read_delay)(struct torture_random_state *rrsp,
 332                            struct rt_read_seg *rtrsp);
 333         void (*readunlock)(int idx);
 334         int (*readlock_held)(void);
 335         unsigned long (*get_gp_seq)(void);
 336         unsigned long (*gp_diff)(unsigned long new, unsigned long old);
 337         void (*deferred_free)(struct rcu_torture *p);
 338         void (*sync)(void);
 339         void (*exp_sync)(void);
 340         unsigned long (*get_gp_state)(void);
 341         unsigned long (*start_gp_poll)(void);
 342         bool (*poll_gp_state)(unsigned long oldstate);
 343         void (*cond_sync)(unsigned long oldstate);
 344         call_rcu_func_t call;
 345         void (*cb_barrier)(void);
 346         void (*fqs)(void);
 347         void (*stats)(void);
 348         void (*gp_kthread_dbg)(void);
 349         bool (*check_boost_failed)(unsigned long gp_state, int *cpup);
 350         int (*stall_dur)(void);
 351         long cbflood_max;
 352         int irq_capable;
 353         int can_boost;
 354         int extendables;
 355         int slow_gps;
 356         int no_pi_lock;
 357         const char *name;
 358 };
 359
 360 static struct rcu_torture_ops *cur_ops;
 361
 362 /*
 363  * Definitions for rcu torture testing.
 364  */
 365
 366 static int torture_readlock_not_held(void)
 367 {
 368         return rcu_read_lock_bh_held() || rcu_read_lock_sched_held();
 369 }
 370
 371 static int rcu_torture_read_lock(void) __acquires(RCU)
 372 {
 373         rcu_read_lock();
 374         return 0;
 375 }
 376
 377 static void
 378 rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 379 {
 380         unsigned long started;
 381         unsigned long completed;
 382         const unsigned long shortdelay_us = 200;
 383         unsigned long longdelay_ms = 300;
 384         unsigned long long ts;
 385
 386         /* We want a short delay sometimes to make a reader delay the grace
 387          * period, and we want a long delay occasionally to trigger
 388          * force_quiescent_state. */
 389
 390         if (!READ_ONCE(rcu_fwd_cb_nodelay) &&
 391             !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
 392                 started = cur_ops->get_gp_seq();
 393                 ts = rcu_trace_clock_local();
 394                 if (preempt_count() & (SOFTIRQ_MASK | HARDIRQ_MASK))
 395                         longdelay_ms = 5; /* Avoid triggering BH limits. */
 396                 mdelay(longdelay_ms);
 397                 rtrsp->rt_delay_ms = longdelay_ms;
 398                 completed = cur_ops->get_gp_seq();
 399                 do_trace_rcu_torture_read(cur_ops->name, NULL, ts,
 400                                           started, completed);
 401         }
 402         if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) {
 403                 udelay(shortdelay_us);
 404                 rtrsp->rt_delay_us = shortdelay_us;
 405         }
 406         if (!preempt_count() &&
 407             !(torture_random(rrsp) % (nrealreaders * 500))) {
 408                 torture_preempt_schedule();  /* QS only if preemptible. */
 409                 rtrsp->rt_preempted = true;
 410         }
 411 }
 412
 413 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 414 {
 415         rcu_read_unlock();
 416 }
 417
 418 /*
 419  * Update callback in the pipe.  This should be invoked after a grace period.
 420  */
 421 static bool
 422 rcu_torture_pipe_update_one(struct rcu_torture *rp)
 423 {
 424         int i;
 425         struct rcu_torture_reader_check *rtrcp = READ_ONCE(rp->rtort_chkp);
 426
 427         if (rtrcp) {
 428                 WRITE_ONCE(rp->rtort_chkp, NULL);
 429                 smp_store_release(&rtrcp->rtc_ready, 1); // Pair with smp_load_acquire().
 430         }
 431         i = READ_ONCE(rp->rtort_pipe_count);
 432         if (i > RCU_TORTURE_PIPE_LEN)
 433                 i = RCU_TORTURE_PIPE_LEN;
 434         atomic_inc(&rcu_torture_wcount[i]);
 435         WRITE_ONCE(rp->rtort_pipe_count, i + 1);
 436         if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
 437                 rp->rtort_mbtest = 0;
 438                 return true;
 439         }
 440         return false;
 441 }
 442
 443 /*
 444  * Update all callbacks in the pipe.  Suitable for synchronous grace-period
 445  * primitives.
 446  */
 447 static void
 448 rcu_torture_pipe_update(struct rcu_torture *old_rp)
 449 {
 450         struct rcu_torture *rp;
 451         struct rcu_torture *rp1;
 452
 453         if (old_rp)
 454                 list_add(&old_rp->rtort_free, &rcu_torture_removed);
 455         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
 456                 if (rcu_torture_pipe_update_one(rp)) {
 457                         list_del(&rp->rtort_free);
 458                         rcu_torture_free(rp);
 459                 }
 460         }
 461 }
 462
 463 static void
 464 rcu_torture_cb(struct rcu_head *p)
 465 {
 466         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 467
 468         if (torture_must_stop_irq()) {
 469                 /* Test is ending, just drop callbacks on the floor. */
 470                 /* The next initialization will pick up the pieces. */
 471                 return;
 472         }
 473         if (rcu_torture_pipe_update_one(rp))
 474                 rcu_torture_free(rp);
 475         else
 476                 cur_ops->deferred_free(rp);
 477 }
 478
 479 static unsigned long rcu_no_completed(void)
 480 {
 481         return 0;
 482 }
 483
 484 static void rcu_torture_deferred_free(struct rcu_torture *p)
 485 {
 486         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 487 }
 488
 489 static void rcu_sync_torture_init(void)
 490 {
 491         INIT_LIST_HEAD(&rcu_torture_removed);
 492 }
 493
 494 static struct rcu_torture_ops rcu_ops = {
 495         .ttype                  = RCU_FLAVOR,
 496         .init                   = rcu_sync_torture_init,
 497         .readlock               = rcu_torture_read_lock,
 498         .read_delay             = rcu_read_delay,
 499         .readunlock             = rcu_torture_read_unlock,
 500         .readlock_held          = torture_readlock_not_held,
 501         .get_gp_seq             = rcu_get_gp_seq,
 502         .gp_diff                = rcu_seq_diff,
 503         .deferred_free          = rcu_torture_deferred_free,
 504         .sync                   = synchronize_rcu,
 505         .exp_sync               = synchronize_rcu_expedited,
 506         .get_gp_state           = get_state_synchronize_rcu,
 507         .start_gp_poll          = start_poll_synchronize_rcu,
 508         .poll_gp_state          = poll_state_synchronize_rcu,
 509         .cond_sync              = cond_synchronize_rcu,
 510         .call                   = call_rcu,
 511         .cb_barrier             = rcu_barrier,
 512         .fqs                    = rcu_force_quiescent_state,
 513         .stats                  = NULL,
 514         .gp_kthread_dbg         = show_rcu_gp_kthreads,
 515         .check_boost_failed     = rcu_check_boost_fail,
 516         .stall_dur              = rcu_jiffies_till_stall_check,
 517         .irq_capable            = 1,
 518         .can_boost              = IS_ENABLED(CONFIG_RCU_BOOST),
 519         .extendables            = RCUTORTURE_MAX_EXTEND,
 520         .name                   = "rcu"
 521 };
 522
 523 /*
 524  * Don't even think about trying any of these in real life!!!
 525  * The names includes "busted", and they really means it!
 526  * The only purpose of these functions is to provide a buggy RCU
 527  * implementation to make sure that rcutorture correctly emits
 528  * buggy-RCU error messages.
 529  */
 530 static void rcu_busted_torture_deferred_free(struct rcu_torture *p)
 531 {
 532         /* This is a deliberate bug for testing purposes only! */
 533         rcu_torture_cb(&p->rtort_rcu);
 534 }
 535
 536 static void synchronize_rcu_busted(void)
 537 {
 538         /* This is a deliberate bug for testing purposes only! */
 539 }
 540
 541 static void
 542 call_rcu_busted(struct rcu_head *head, rcu_callback_t func)
 543 {
 544         /* This is a deliberate bug for testing purposes only! */
 545         func(head);
 546 }
 547
 548 static struct rcu_torture_ops rcu_busted_ops = {
 549         .ttype          = INVALID_RCU_FLAVOR,
 550         .init           = rcu_sync_torture_init,
 551         .readlock       = rcu_torture_read_lock,
 552         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 553         .readunlock     = rcu_torture_read_unlock,
 554         .readlock_held  = torture_readlock_not_held,
 555         .get_gp_seq     = rcu_no_completed,
 556         .deferred_free  = rcu_busted_torture_deferred_free,
 557         .sync           = synchronize_rcu_busted,
 558         .exp_sync       = synchronize_rcu_busted,
 559         .call           = call_rcu_busted,
 560         .cb_barrier     = NULL,
 561         .fqs            = NULL,
 562         .stats          = NULL,
 563         .irq_capable    = 1,
 564         .name           = "busted"
 565 };
 566
 567 /*
 568  * Definitions for srcu torture testing.
 569  */
 570
 571 DEFINE_STATIC_SRCU(srcu_ctl);
 572 static struct srcu_struct srcu_ctld;
 573 static struct srcu_struct *srcu_ctlp = &srcu_ctl;
 574
 575 static int srcu_torture_read_lock(void) __acquires(srcu_ctlp)
 576 {
 577         return srcu_read_lock(srcu_ctlp);
 578 }
 579
 580 static void
 581 srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 582 {
 583         long delay;
 584         const long uspertick = 1000000 / HZ;
 585         const long longdelay = 10;
 586
 587         /* We want there to be long-running readers, but not all the time. */
 588
 589         delay = torture_random(rrsp) %
 590                 (nrealreaders * 2 * longdelay * uspertick);
 591         if (!delay && in_task()) {
 592                 schedule_timeout_interruptible(longdelay);
 593                 rtrsp->rt_delay_jiffies = longdelay;
 594         } else {
 595                 rcu_read_delay(rrsp, rtrsp);
 596         }
 597 }
 598
 599 static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp)
 600 {
 601         srcu_read_unlock(srcu_ctlp, idx);
 602 }
 603
 604 static int torture_srcu_read_lock_held(void)
 605 {
 606         return srcu_read_lock_held(srcu_ctlp);
 607 }
 608
 609 static unsigned long srcu_torture_completed(void)
 610 {
 611         return srcu_batches_completed(srcu_ctlp);
 612 }
 613
 614 static void srcu_torture_deferred_free(struct rcu_torture *rp)
 615 {
 616         call_srcu(srcu_ctlp, &rp->rtort_rcu, rcu_torture_cb);
 617 }
 618
 619 static void srcu_torture_synchronize(void)
 620 {
 621         synchronize_srcu(srcu_ctlp);
 622 }
 623
 624 static unsigned long srcu_torture_get_gp_state(void)
 625 {
 626         return get_state_synchronize_srcu(srcu_ctlp);
 627 }
 628
 629 static unsigned long srcu_torture_start_gp_poll(void)
 630 {
 631         return start_poll_synchronize_srcu(srcu_ctlp);
 632 }
 633
 634 static bool srcu_torture_poll_gp_state(unsigned long oldstate)
 635 {
 636         return poll_state_synchronize_srcu(srcu_ctlp, oldstate);
 637 }
 638
 639 static void srcu_torture_call(struct rcu_head *head,
 640                               rcu_callback_t func)
 641 {
 642         call_srcu(srcu_ctlp, head, func);
 643 }
 644
 645 static void srcu_torture_barrier(void)
 646 {
 647         srcu_barrier(srcu_ctlp);
 648 }
 649
 650 static void srcu_torture_stats(void)
 651 {
 652         srcu_torture_stats_print(srcu_ctlp, torture_type, TORTURE_FLAG);
 653 }
 654
 655 static void srcu_torture_synchronize_expedited(void)
 656 {
 657         synchronize_srcu_expedited(srcu_ctlp);
 658 }
 659
 660 static struct rcu_torture_ops srcu_ops = {
 661         .ttype          = SRCU_FLAVOR,
 662         .init           = rcu_sync_torture_init,
 663         .readlock       = srcu_torture_read_lock,
 664         .read_delay     = srcu_read_delay,
 665         .readunlock     = srcu_torture_read_unlock,
 666         .readlock_held  = torture_srcu_read_lock_held,
 667         .get_gp_seq     = srcu_torture_completed,
 668         .deferred_free  = srcu_torture_deferred_free,
 669         .sync           = srcu_torture_synchronize,
 670         .exp_sync       = srcu_torture_synchronize_expedited,
 671         .get_gp_state   = srcu_torture_get_gp_state,
 672         .start_gp_poll  = srcu_torture_start_gp_poll,
 673         .poll_gp_state  = srcu_torture_poll_gp_state,
 674         .call           = srcu_torture_call,
 675         .cb_barrier     = srcu_torture_barrier,
 676         .stats          = srcu_torture_stats,
 677         .irq_capable    = 1,
 678         .no_pi_lock     = IS_ENABLED(CONFIG_TINY_SRCU),
 679         .name           = "srcu"
 680 };
 681
 682 static void srcu_torture_init(void)
 683 {
 684         rcu_sync_torture_init();
 685         WARN_ON(init_srcu_struct(&srcu_ctld));
 686         srcu_ctlp = &srcu_ctld;
 687 }
 688
 689 static void srcu_torture_cleanup(void)
 690 {
 691         cleanup_srcu_struct(&srcu_ctld);
 692         srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
 693 }
 694
 695 /* As above, but dynamically allocated. */
 696 static struct rcu_torture_ops srcud_ops = {
 697         .ttype          = SRCU_FLAVOR,
 698         .init           = srcu_torture_init,
 699         .cleanup        = srcu_torture_cleanup,
 700         .readlock       = srcu_torture_read_lock,
 701         .read_delay     = srcu_read_delay,
 702         .readunlock     = srcu_torture_read_unlock,
 703         .readlock_held  = torture_srcu_read_lock_held,
 704         .get_gp_seq     = srcu_torture_completed,
 705         .deferred_free  = srcu_torture_deferred_free,
 706         .sync           = srcu_torture_synchronize,
 707         .exp_sync       = srcu_torture_synchronize_expedited,
 708         .call           = srcu_torture_call,
 709         .cb_barrier     = srcu_torture_barrier,
 710         .stats          = srcu_torture_stats,
 711         .irq_capable    = 1,
 712         .no_pi_lock     = IS_ENABLED(CONFIG_TINY_SRCU),
 713         .name           = "srcud"
 714 };
 715
 716 /* As above, but broken due to inappropriate reader extension. */
 717 static struct rcu_torture_ops busted_srcud_ops = {
 718         .ttype          = SRCU_FLAVOR,
 719         .init           = srcu_torture_init,
 720         .cleanup        = srcu_torture_cleanup,
 721         .readlock       = srcu_torture_read_lock,
 722         .read_delay     = rcu_read_delay,
 723         .readunlock     = srcu_torture_read_unlock,
 724         .readlock_held  = torture_srcu_read_lock_held,
 725         .get_gp_seq     = srcu_torture_completed,
 726         .deferred_free  = srcu_torture_deferred_free,
 727         .sync           = srcu_torture_synchronize,
 728         .exp_sync       = srcu_torture_synchronize_expedited,
 729         .call           = srcu_torture_call,
 730         .cb_barrier     = srcu_torture_barrier,
 731         .stats          = srcu_torture_stats,
 732         .irq_capable    = 1,
 733         .no_pi_lock     = IS_ENABLED(CONFIG_TINY_SRCU),
 734         .extendables    = RCUTORTURE_MAX_EXTEND,
 735         .name           = "busted_srcud"
 736 };
 737
 738 /*
 739  * Definitions for RCU-tasks torture testing.
 740  */
 741
 742 static int tasks_torture_read_lock(void)
 743 {
 744         return 0;
 745 }
 746
 747 static void tasks_torture_read_unlock(int idx)
 748 {
 749 }
 750
 751 static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
 752 {
 753         call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
 754 }
 755
 756 static void synchronize_rcu_mult_test(void)
 757 {
 758         synchronize_rcu_mult(call_rcu_tasks, call_rcu);
 759 }
 760
 761 static struct rcu_torture_ops tasks_ops = {
 762         .ttype          = RCU_TASKS_FLAVOR,
 763         .init           = rcu_sync_torture_init,
 764         .readlock       = tasks_torture_read_lock,
 765         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 766         .readunlock     = tasks_torture_read_unlock,
 767         .get_gp_seq     = rcu_no_completed,
 768         .deferred_free  = rcu_tasks_torture_deferred_free,
 769         .sync           = synchronize_rcu_tasks,
 770         .exp_sync       = synchronize_rcu_mult_test,
 771         .call           = call_rcu_tasks,
 772         .cb_barrier     = rcu_barrier_tasks,
 773         .gp_kthread_dbg = show_rcu_tasks_classic_gp_kthread,
 774         .fqs            = NULL,
 775         .stats          = NULL,
 776         .irq_capable    = 1,
 777         .slow_gps       = 1,
 778         .name           = "tasks"
 779 };
 780
 781 /*
 782  * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
 783  * This implementation does not necessarily work well with CPU hotplug.
 784  */
 785
 786 static void synchronize_rcu_trivial(void)
 787 {
 788         int cpu;
 789
 790         for_each_online_cpu(cpu) {
 791                 rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
 792                 WARN_ON_ONCE(raw_smp_processor_id() != cpu);
 793         }
 794 }
 795
 796 static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
 797 {
 798         preempt_disable();
 799         return 0;
 800 }
 801
 802 static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
 803 {
 804         preempt_enable();
 805 }
 806
 807 static struct rcu_torture_ops trivial_ops = {
 808         .ttype          = RCU_TRIVIAL_FLAVOR,
 809         .init           = rcu_sync_torture_init,
 810         .readlock       = rcu_torture_read_lock_trivial,
 811         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 812         .readunlock     = rcu_torture_read_unlock_trivial,
 813         .readlock_held  = torture_readlock_not_held,
 814         .get_gp_seq     = rcu_no_completed,
 815         .sync           = synchronize_rcu_trivial,
 816         .exp_sync       = synchronize_rcu_trivial,
 817         .fqs            = NULL,
 818         .stats          = NULL,
 819         .irq_capable    = 1,
 820         .name           = "trivial"
 821 };
 822
 823 /*
 824  * Definitions for rude RCU-tasks torture testing.
 825  */
 826
 827 static void rcu_tasks_rude_torture_deferred_free(struct rcu_torture *p)
 828 {
 829         call_rcu_tasks_rude(&p->rtort_rcu, rcu_torture_cb);
 830 }
 831
 832 static struct rcu_torture_ops tasks_rude_ops = {
 833         .ttype          = RCU_TASKS_RUDE_FLAVOR,
 834         .init           = rcu_sync_torture_init,
 835         .readlock       = rcu_torture_read_lock_trivial,
 836         .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
 837         .readunlock     = rcu_torture_read_unlock_trivial,
 838         .get_gp_seq     = rcu_no_completed,
 839         .deferred_free  = rcu_tasks_rude_torture_deferred_free,
 840         .sync           = synchronize_rcu_tasks_rude,
 841         .exp_sync       = synchronize_rcu_tasks_rude,
 842         .call           = call_rcu_tasks_rude,
 843         .cb_barrier     = rcu_barrier_tasks_rude,
 844         .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread,
 845         .cbflood_max    = 50000,
 846         .fqs            = NULL,
 847         .stats          = NULL,
 848         .irq_capable    = 1,
 849         .name           = "tasks-rude"
 850 };
 851
 852 /*
 853  * Definitions for tracing RCU-tasks torture testing.
 854  */
 855
 856 static int tasks_tracing_torture_read_lock(void)
 857 {
 858         rcu_read_lock_trace();
 859         return 0;
 860 }
 861
 862 static void tasks_tracing_torture_read_unlock(int idx)
 863 {
 864         rcu_read_unlock_trace();
 865 }
 866
 867 static void rcu_tasks_tracing_torture_deferred_free(struct rcu_torture *p)
 868 {
 869         call_rcu_tasks_trace(&p->rtort_rcu, rcu_torture_cb);
 870 }
 871
 872 static struct rcu_torture_ops tasks_tracing_ops = {
 873         .ttype          = RCU_TASKS_TRACING_FLAVOR,
 874         .init           = rcu_sync_torture_init,
 875         .readlock       = tasks_tracing_torture_read_lock,
 876         .read_delay     = srcu_read_delay,  /* just reuse srcu's version. */
 877         .readunlock     = tasks_tracing_torture_read_unlock,
 878         .readlock_held  = rcu_read_lock_trace_held,
 879         .get_gp_seq     = rcu_no_completed,
 880         .deferred_free  = rcu_tasks_tracing_torture_deferred_free,
 881         .sync           = synchronize_rcu_tasks_trace,
 882         .exp_sync       = synchronize_rcu_tasks_trace,
 883         .call           = call_rcu_tasks_trace,
 884         .cb_barrier     = rcu_barrier_tasks_trace,
 885         .gp_kthread_dbg = show_rcu_tasks_trace_gp_kthread,
 886         .cbflood_max    = 50000,
 887         .fqs            = NULL,
 888         .stats          = NULL,
 889         .irq_capable    = 1,
 890         .slow_gps       = 1,
 891         .name           = "tasks-tracing"
 892 };
 893
 894 static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
 895 {
 896         if (!cur_ops->gp_diff)
 897                 return new - old;
 898         return cur_ops->gp_diff(new, old);
 899 }
 900
 901 /*
 902  * RCU torture priority-boost testing.  Runs one real-time thread per
 903  * CPU for moderate bursts, repeatedly starting grace periods and waiting
 904  * for them to complete.  If a given grace period takes too long, we assume
 905  * that priority inversion has occurred.
 906  */
 907
 908 static int old_rt_runtime = -1;
 909
 910 static void rcu_torture_disable_rt_throttle(void)
 911 {
 912         /*
 913          * Disable RT throttling so that rcutorture's boost threads don't get
 914          * throttled. Only possible if rcutorture is built-in otherwise the
 915          * user should manually do this by setting the sched_rt_period_us and
 916          * sched_rt_runtime sysctls.
 917          */
 918         if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime != -1)
 919                 return;
 920
 921         old_rt_runtime = sysctl_sched_rt_runtime;
 922         sysctl_sched_rt_runtime = -1;
 923 }
 924
 925 static void rcu_torture_enable_rt_throttle(void)
 926 {
 927         if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime == -1)
 928                 return;
 929
 930         sysctl_sched_rt_runtime = old_rt_runtime;
 931         old_rt_runtime = -1;
 932 }
 933
 934 static bool rcu_torture_boost_failed(unsigned long gp_state, unsigned long *start)
 935 {
 936         int cpu;
 937         static int dbg_done;
 938         unsigned long end = jiffies;
 939         bool gp_done;
 940         unsigned long j;
 941         static unsigned long last_persist;
 942         unsigned long lp;
 943         unsigned long mininterval = test_boost_duration * HZ - HZ / 2;
 944
 945         if (end - *start > mininterval) {
 946                 // Recheck after checking time to avoid false positives.
 947                 smp_mb(); // Time check before grace-period check.
 948                 if (cur_ops->poll_gp_state(gp_state))
 949                         return false; // passed, though perhaps just barely
 950                 if (cur_ops->check_boost_failed && !cur_ops->check_boost_failed(gp_state, &cpu)) {
 951                         // At most one persisted message per boost test.
 952                         j = jiffies;
 953                         lp = READ_ONCE(last_persist);
 954                         if (time_after(j, lp + mininterval) && cmpxchg(&last_persist, lp, j) == lp)
 955                                 pr_info("Boost inversion persisted: No QS from CPU %d\n", cpu);
 956                         return false; // passed on a technicality
 957                 }
 958                 VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");
 959                 n_rcu_torture_boost_failure++;
 960                 if (!xchg(&dbg_done, 1) && cur_ops->gp_kthread_dbg) {
 961                         pr_info("Boost inversion thread ->rt_priority %u gp_state %lu jiffies %lu\n",
 962                                 current->rt_priority, gp_state, end - *start);
 963                         cur_ops->gp_kthread_dbg();
 964                         // Recheck after print to flag grace period ending during splat.
 965                         gp_done = cur_ops->poll_gp_state(gp_state);
 966                         pr_info("Boost inversion: GP %lu %s.\n", gp_state,
 967                                 gp_done ? "ended already" : "still pending");
 968
 969                 }
 970
 971                 return true; // failed
 972         } else if (cur_ops->check_boost_failed && !cur_ops->check_boost_failed(gp_state, NULL)) {
 973                 *start = jiffies;
 974         }
 975
 976         return false; // passed
 977 }
 978
 979 static int rcu_torture_boost(void *arg)
 980 {
 981         unsigned long endtime;
 982         unsigned long gp_state;
 983         unsigned long gp_state_time;
 984         unsigned long oldstarttime;
 985
 986         VERBOSE_TOROUT_STRING("rcu_torture_boost started");
 987
 988         /* Set real-time priority. */
 989         sched_set_fifo_low(current);
 990
 991         /* Each pass through the following loop does one boost-test cycle. */
 992         do {
 993                 bool failed = false; // Test failed already in this test interval
 994                 bool gp_initiated = false;
 995
 996                 if (kthread_should_stop())
 997                         goto checkwait;
 998
 999                 /* Wait for the next test interval. */
1000                 oldstarttime = boost_starttime;
1001                 while (time_before(jiffies, oldstarttime)) {
1002                         schedule_timeout_interruptible(oldstarttime - jiffies);
1003                         if (stutter_wait("rcu_torture_boost"))
1004                                 sched_set_fifo_low(current);
1005                         if (torture_must_stop())
1006                                 goto checkwait;
1007                 }
1008
1009                 // Do one boost-test interval.
1010                 endtime = oldstarttime + test_boost_duration * HZ;
1011                 while (time_before(jiffies, endtime)) {
1012                         // Has current GP gone too long?
1013                         if (gp_initiated && !failed && !cur_ops->poll_gp_state(gp_state))
1014                                 failed = rcu_torture_boost_failed(gp_state, &gp_state_time);
1015                         // If we don't have a grace period in flight, start one.
1016                         if (!gp_initiated || cur_ops->poll_gp_state(gp_state)) {
1017                                 gp_state = cur_ops->start_gp_poll();
1018                                 gp_initiated = true;
1019                                 gp_state_time = jiffies;
1020                         }
1021                         if (stutter_wait("rcu_torture_boost")) {
1022                                 sched_set_fifo_low(current);
1023                                 // If the grace period already ended,
1024                                 // we don't know when that happened, so
1025                                 // start over.
1026                                 if (cur_ops->poll_gp_state(gp_state))
1027                                         gp_initiated = false;
1028                         }
1029                         if (torture_must_stop())
1030                                 goto checkwait;
1031                 }
1032
1033                 // In case the grace period extended beyond the end of the loop.
1034                 if (gp_initiated && !failed && !cur_ops->poll_gp_state(gp_state))
1035                         rcu_torture_boost_failed(gp_state, &gp_state_time);
1036
1037                 /*
1038                  * Set the start time of the next test interval.
1039                  * Yes, this is vulnerable to long delays, but such
1040                  * delays simply cause a false negative for the next
1041                  * interval.  Besides, we are running at RT priority,
1042                  * so delays should be relatively rare.
1043                  */
1044                 while (oldstarttime == boost_starttime && !kthread_should_stop()) {
1045                         if (mutex_trylock(&boost_mutex)) {
1046                                 if (oldstarttime == boost_starttime) {
1047                                         boost_starttime = jiffies + test_boost_interval * HZ;
1048                                         n_rcu_torture_boosts++;
1049                                 }
1050                                 mutex_unlock(&boost_mutex);
1051                                 break;
1052                         }
1053                         schedule_timeout_uninterruptible(1);
1054                 }
1055
1056                 /* Go do the stutter. */
1057 checkwait:      if (stutter_wait("rcu_torture_boost"))
1058                         sched_set_fifo_low(current);
1059         } while (!torture_must_stop());
1060
1061         /* Clean up and exit. */
1062         while (!kthread_should_stop()) {
1063                 torture_shutdown_absorb("rcu_torture_boost");
1064                 schedule_timeout_uninterruptible(1);
1065         }
1066         torture_kthread_stopping("rcu_torture_boost");
1067         return 0;
1068 }
1069
1070 /*
1071  * RCU torture force-quiescent-state kthread.  Repeatedly induces
1072  * bursts of calls to force_quiescent_state(), increasing the probability
1073  * of occurrence of some important types of race conditions.
1074  */
1075 static int
1076 rcu_torture_fqs(void *arg)
1077 {
1078         unsigned long fqs_resume_time;
1079         int fqs_burst_remaining;
1080         int oldnice = task_nice(current);
1081
1082         VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
1083         do {
1084                 fqs_resume_time = jiffies + fqs_stutter * HZ;
1085                 while (time_before(jiffies, fqs_resume_time) &&
1086                        !kthread_should_stop()) {
1087                         schedule_timeout_interruptible(1);
1088                 }
1089                 fqs_burst_remaining = fqs_duration;
1090                 while (fqs_burst_remaining > 0 &&
1091                        !kthread_should_stop()) {
1092                         cur_ops->fqs();
1093                         udelay(fqs_holdoff);
1094                         fqs_burst_remaining -= fqs_holdoff;
1095                 }
1096                 if (stutter_wait("rcu_torture_fqs"))
1097                         sched_set_normal(current, oldnice);
1098         } while (!torture_must_stop());
1099         torture_kthread_stopping("rcu_torture_fqs");
1100         return 0;
1101 }
1102
1103 // Used by writers to randomly choose from the available grace-period
1104 // primitives.  The only purpose of the initialization is to size the array.
1105 static int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC, RTWS_COND_GET, RTWS_POLL_GET, RTWS_SYNC };
1106 static int nsynctypes;
1107
1108 /*
1109  * Determine which grace-period primitives are available.
1110  */
1111 static void rcu_torture_write_types(void)
1112 {
1113         bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
1114         bool gp_poll1 = gp_poll, gp_sync1 = gp_sync;
1115
1116         /* Initialize synctype[] array.  If none set, take default. */
1117         if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_poll1 && !gp_sync1)
1118                 gp_cond1 = gp_exp1 = gp_normal1 = gp_poll1 = gp_sync1 = true;
1119         if (gp_cond1 && cur_ops->get_gp_state && cur_ops->cond_sync) {
1120                 synctype[nsynctypes++] = RTWS_COND_GET;
1121                 pr_info("%s: Testing conditional GPs.\n", __func__);
1122         } else if (gp_cond && (!cur_ops->get_gp_state || !cur_ops->cond_sync)) {
1123                 pr_alert("%s: gp_cond without primitives.\n", __func__);
1124         }
1125         if (gp_exp1 && cur_ops->exp_sync) {
1126                 synctype[nsynctypes++] = RTWS_EXP_SYNC;
1127                 pr_info("%s: Testing expedited GPs.\n", __func__);
1128         } else if (gp_exp && !cur_ops->exp_sync) {
1129                 pr_alert("%s: gp_exp without primitives.\n", __func__);
1130         }
1131         if (gp_normal1 && cur_ops->deferred_free) {
1132                 synctype[nsynctypes++] = RTWS_DEF_FREE;
1133                 pr_info("%s: Testing asynchronous GPs.\n", __func__);
1134         } else if (gp_normal && !cur_ops->deferred_free) {
1135                 pr_alert("%s: gp_normal without primitives.\n", __func__);
1136         }
1137         if (gp_poll1 && cur_ops->start_gp_poll && cur_ops->poll_gp_state) {
1138                 synctype[nsynctypes++] = RTWS_POLL_GET;
1139                 pr_info("%s: Testing polling GPs.\n", __func__);
1140         } else if (gp_poll && (!cur_ops->start_gp_poll || !cur_ops->poll_gp_state)) {
1141                 pr_alert("%s: gp_poll without primitives.\n", __func__);
1142         }
1143         if (gp_sync1 && cur_ops->sync) {
1144                 synctype[nsynctypes++] = RTWS_SYNC;
1145                 pr_info("%s: Testing normal GPs.\n", __func__);
1146         } else if (gp_sync && !cur_ops->sync) {
1147                 pr_alert("%s: gp_sync without primitives.\n", __func__);
1148         }
1149 }
1150
1151 /*
1152  * RCU torture writer kthread.  Repeatedly substitutes a new structure
1153  * for that pointed to by rcu_torture_current, freeing the old structure
1154  * after a series of grace periods (the "pipeline").
1155  */
1156 static int
1157 rcu_torture_writer(void *arg)
1158 {
1159         bool boot_ended;
1160         bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
1161         unsigned long cookie;
1162         int expediting = 0;
1163         unsigned long gp_snap;
1164         int i;
1165         int idx;
1166         int oldnice = task_nice(current);
1167         struct rcu_torture *rp;
1168         struct rcu_torture *old_rp;
1169         static DEFINE_TORTURE_RANDOM(rand);
1170         bool stutter_waited;
1171
1172         VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
1173         if (!can_expedite)
1174                 pr_alert("%s" TORTURE_FLAG
1175                          " GP expediting controlled from boot/sysfs for %s.\n",
1176                          torture_type, cur_ops->name);
1177         if (WARN_ONCE(nsynctypes == 0,
1178                       "rcu_torture_writer: No update-side primitives.\n")) {
1179                 /*
1180                  * No updates primitives, so don't try updating.
1181                  * The resulting test won't be testing much, hence the
1182                  * above WARN_ONCE().
1183                  */
1184                 rcu_torture_writer_state = RTWS_STOPPING;
1185                 torture_kthread_stopping("rcu_torture_writer");
1186         }
1187
1188         do {
1189                 rcu_torture_writer_state = RTWS_FIXED_DELAY;
1190                 torture_hrtimeout_us(500, 1000, &rand);
1191                 rp = rcu_torture_alloc();
1192                 if (rp == NULL)
1193                         continue;
1194                 rp->rtort_pipe_count = 0;
1195                 rcu_torture_writer_state = RTWS_DELAY;
1196                 udelay(torture_random(&rand) & 0x3ff);
1197                 rcu_torture_writer_state = RTWS_REPLACE;
1198                 old_rp = rcu_dereference_check(rcu_torture_current,
1199                                                current == writer_task);
1200                 rp->rtort_mbtest = 1;
1201                 rcu_assign_pointer(rcu_torture_current, rp);
1202                 smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
1203                 if (old_rp) {
1204                         i = old_rp->rtort_pipe_count;
1205                         if (i > RCU_TORTURE_PIPE_LEN)
1206                                 i = RCU_TORTURE_PIPE_LEN;
1207                         atomic_inc(&rcu_torture_wcount[i]);
1208                         WRITE_ONCE(old_rp->rtort_pipe_count,
1209                                    old_rp->rtort_pipe_count + 1);
1210                         if (cur_ops->get_gp_state && cur_ops->poll_gp_state) {
1211                                 idx = cur_ops->readlock();
1212                                 cookie = cur_ops->get_gp_state();
1213                                 WARN_ONCE(rcu_torture_writer_state != RTWS_DEF_FREE &&
1214                                           cur_ops->poll_gp_state(cookie),
1215                                           "%s: Cookie check 1 failed %s(%d) %lu->%lu\n",
1216                                           __func__,
1217                                           rcu_torture_writer_state_getname(),
1218                                           rcu_torture_writer_state,
1219                                           cookie, cur_ops->get_gp_state());
1220                                 cur_ops->readunlock(idx);
1221                         }
1222                         switch (synctype[torture_random(&rand) % nsynctypes]) {
1223                         case RTWS_DEF_FREE:
1224                                 rcu_torture_writer_state = RTWS_DEF_FREE;
1225                                 cur_ops->deferred_free(old_rp);
1226                                 break;
1227                         case RTWS_EXP_SYNC:
1228                                 rcu_torture_writer_state = RTWS_EXP_SYNC;
1229                                 cur_ops->exp_sync();
1230                                 rcu_torture_pipe_update(old_rp);
1231                                 break;
1232                         case RTWS_COND_GET:
1233                                 rcu_torture_writer_state = RTWS_COND_GET;
1234                                 gp_snap = cur_ops->get_gp_state();
1235                                 torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
1236                                 rcu_torture_writer_state = RTWS_COND_SYNC;
1237                                 cur_ops->cond_sync(gp_snap);
1238                                 rcu_torture_pipe_update(old_rp);
1239                                 break;
1240                         case RTWS_POLL_GET:
1241                                 rcu_torture_writer_state = RTWS_POLL_GET;
1242                                 gp_snap = cur_ops->start_gp_poll();
1243                                 rcu_torture_writer_state = RTWS_POLL_WAIT;
1244                                 while (!cur_ops->poll_gp_state(gp_snap))
1245                                         torture_hrtimeout_jiffies(torture_random(&rand) % 16,
1246                                                                   &rand);
1247                                 rcu_torture_pipe_update(old_rp);
1248                                 break;
1249                         case RTWS_SYNC:
1250                                 rcu_torture_writer_state = RTWS_SYNC;
1251                                 cur_ops->sync();
1252                                 rcu_torture_pipe_update(old_rp);
1253                                 break;
1254                         default:
1255                                 WARN_ON_ONCE(1);
1256                                 break;
1257                         }
1258                 }
1259                 WRITE_ONCE(rcu_torture_current_version,
1260                            rcu_torture_current_version + 1);
1261                 /* Cycle through nesting levels of rcu_expedite_gp() calls. */
1262                 if (can_expedite &&
1263                     !(torture_random(&rand) & 0xff & (!!expediting - 1))) {
1264                         WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited());
1265                         if (expediting >= 0)
1266                                 rcu_expedite_gp();
1267                         else
1268                                 rcu_unexpedite_gp();
1269                         if (++expediting > 3)
1270                                 expediting = -expediting;
1271                 } else if (!can_expedite) { /* Disabled during boot, recheck. */
1272                         can_expedite = !rcu_gp_is_expedited() &&
1273                                        !rcu_gp_is_normal();
1274                 }
1275                 rcu_torture_writer_state = RTWS_STUTTER;
1276                 boot_ended = rcu_inkernel_boot_has_ended();
1277                 stutter_waited = stutter_wait("rcu_torture_writer");
1278                 if (stutter_waited &&
1279                     !READ_ONCE(rcu_fwd_cb_nodelay) &&
1280                     !cur_ops->slow_gps &&
1281                     !torture_must_stop() &&
1282                     boot_ended)
1283                         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
1284                                 if (list_empty(&rcu_tortures[i].rtort_free) &&
1285                                     rcu_access_pointer(rcu_torture_current) !=
1286                                     &rcu_tortures[i]) {
1287                                         rcu_ftrace_dump(DUMP_ALL);
1288                                         WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
1289                                 }
1290                 if (stutter_waited)
1291                         sched_set_normal(current, oldnice);
1292         } while (!torture_must_stop());
1293         rcu_torture_current = NULL;  // Let stats task know that we are done.
1294         /* Reset expediting back to unexpedited. */
1295         if (expediting > 0)
1296                 expediting = -expediting;
1297         while (can_expedite && expediting++ < 0)
1298                 rcu_unexpedite_gp();
1299         WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited());
1300         if (!can_expedite)
1301                 pr_alert("%s" TORTURE_FLAG
1302                          " Dynamic grace-period expediting was disabled.\n",
1303                          torture_type);
1304         rcu_torture_writer_state = RTWS_STOPPING;
1305         torture_kthread_stopping("rcu_torture_writer");
1306         return 0;
1307 }
1308
1309 /*
1310  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
1311  * delay between calls.
1312  */
1313 static int
1314 rcu_torture_fakewriter(void *arg)
1315 {
1316         unsigned long gp_snap;
1317         DEFINE_TORTURE_RANDOM(rand);
1318
1319         VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
1320         set_user_nice(current, MAX_NICE);
1321
1322         do {
1323                 torture_hrtimeout_jiffies(torture_random(&rand) % 10, &rand);
1324                 if (cur_ops->cb_barrier != NULL &&
1325                     torture_random(&rand) % (nfakewriters * 8) == 0) {
1326                         cur_ops->cb_barrier();
1327                 } else {
1328                         switch (synctype[torture_random(&rand) % nsynctypes]) {
1329                         case RTWS_DEF_FREE:
1330                                 break;
1331                         case RTWS_EXP_SYNC:
1332                                 cur_ops->exp_sync();
1333                                 break;
1334                         case RTWS_COND_GET:
1335                                 gp_snap = cur_ops->get_gp_state();
1336                                 torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
1337                                 cur_ops->cond_sync(gp_snap);
1338                                 break;
1339                         case RTWS_POLL_GET:
1340                                 gp_snap = cur_ops->start_gp_poll();
1341                                 while (!cur_ops->poll_gp_state(gp_snap)) {
1342                                         torture_hrtimeout_jiffies(torture_random(&rand) % 16,
1343                                                                   &rand);
1344                                 }
1345                                 break;
1346                         case RTWS_SYNC:
1347                                 cur_ops->sync();
1348                                 break;
1349                         default:
1350                                 WARN_ON_ONCE(1);
1351                                 break;
1352                         }
1353                 }
1354                 stutter_wait("rcu_torture_fakewriter");
1355         } while (!torture_must_stop());
1356
1357         torture_kthread_stopping("rcu_torture_fakewriter");
1358         return 0;
1359 }
1360
1361 static void rcu_torture_timer_cb(struct rcu_head *rhp)
1362 {
1363         kfree(rhp);
1364 }
1365
1366 // Set up and carry out testing of RCU's global memory ordering
1367 static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp,
1368                                         struct torture_random_state *trsp)
1369 {
1370         unsigned long loops;
1371         int noc = torture_num_online_cpus();
1372         int rdrchked;
1373         int rdrchker;
1374         struct rcu_torture_reader_check *rtrcp; // Me.
1375         struct rcu_torture_reader_check *rtrcp_assigner; // Assigned us to do checking.
1376         struct rcu_torture_reader_check *rtrcp_chked; // Reader being checked.
1377         struct rcu_torture_reader_check *rtrcp_chker; // Reader doing checking when not me.
1378
1379         if (myid < 0)
1380                 return; // Don't try this from timer handlers.
1381
1382         // Increment my counter.
1383         rtrcp = &rcu_torture_reader_mbchk[myid];
1384         WRITE_ONCE(rtrcp->rtc_myloops, rtrcp->rtc_myloops + 1);
1385
1386         // Attempt to assign someone else some checking work.
1387         rdrchked = torture_random(trsp) % nrealreaders;
1388         rtrcp_chked = &rcu_torture_reader_mbchk[rdrchked];
1389         rdrchker = torture_random(trsp) % nrealreaders;
1390         rtrcp_chker = &rcu_torture_reader_mbchk[rdrchker];
1391         if (rdrchked != myid && rdrchked != rdrchker && noc >= rdrchked && noc >= rdrchker &&
1392             smp_load_acquire(&rtrcp->rtc_chkrdr) < 0 && // Pairs with smp_store_release below.
1393             !READ_ONCE(rtp->rtort_chkp) &&
1394             !smp_load_acquire(&rtrcp_chker->rtc_assigner)) { // Pairs with smp_store_release below.
1395                 rtrcp->rtc_chkloops = READ_ONCE(rtrcp_chked->rtc_myloops);
1396                 WARN_ON_ONCE(rtrcp->rtc_chkrdr >= 0);
1397                 rtrcp->rtc_chkrdr = rdrchked;
1398                 WARN_ON_ONCE(rtrcp->rtc_ready); // This gets set after the grace period ends.
1399                 if (cmpxchg_relaxed(&rtrcp_chker->rtc_assigner, NULL, rtrcp) ||
1400                     cmpxchg_relaxed(&rtp->rtort_chkp, NULL, rtrcp))
1401                         (void)cmpxchg_relaxed(&rtrcp_chker->rtc_assigner, rtrcp, NULL); // Back out.
1402         }
1403
1404         // If assigned some completed work, do it!
1405         rtrcp_assigner = READ_ONCE(rtrcp->rtc_assigner);
1406         if (!rtrcp_assigner || !smp_load_acquire(&rtrcp_assigner->rtc_ready))
1407                 return; // No work or work not yet ready.
1408         rdrchked = rtrcp_assigner->rtc_chkrdr;
1409         if (WARN_ON_ONCE(rdrchked < 0))
1410                 return;
1411         rtrcp_chked = &rcu_torture_reader_mbchk[rdrchked];
1412         loops = READ_ONCE(rtrcp_chked->rtc_myloops);
1413         atomic_inc(&n_rcu_torture_mbchk_tries);
1414         if (ULONG_CMP_LT(loops, rtrcp_assigner->rtc_chkloops))
1415                 atomic_inc(&n_rcu_torture_mbchk_fail);
1416         rtrcp_assigner->rtc_chkloops = loops + ULONG_MAX / 2;
1417         rtrcp_assigner->rtc_ready = 0;
1418         smp_store_release(&rtrcp->rtc_assigner, NULL); // Someone else can assign us work.
1419         smp_store_release(&rtrcp_assigner->rtc_chkrdr, -1); // Assigner can again assign.
1420 }
1421
1422 /*
1423  * Do one extension of an RCU read-side critical section using the
1424  * current reader state in readstate (set to zero for initial entry
1425  * to extended critical section), set the new state as specified by
1426  * newstate (set to zero for final exit from extended critical section),
1427  * and random-number-generator state in trsp.  If this is neither the
1428  * beginning or end of the critical section and if there was actually a
1429  * change, do a ->read_delay().
1430  */
1431 static void rcutorture_one_extend(int *readstate, int newstate,
1432                                   struct torture_random_state *trsp,
1433                                   struct rt_read_seg *rtrsp)
1434 {
1435         unsigned long flags;
1436         int idxnew1 = -1;
1437         int idxnew2 = -1;
1438         int idxold1 = *readstate;
1439         int idxold2 = idxold1;
1440         int statesnew = ~*readstate & newstate;
1441         int statesold = *readstate & ~newstate;
1442
1443         WARN_ON_ONCE(idxold2 < 0);
1444         WARN_ON_ONCE((idxold2 >> RCUTORTURE_RDR_SHIFT_2) > 1);
1445         rtrsp->rt_readstate = newstate;
1446
1447         /* First, put new protection in place to avoid critical-section gap. */
1448         if (statesnew & RCUTORTURE_RDR_BH)
1449                 local_bh_disable();
1450         if (statesnew & RCUTORTURE_RDR_RBH)
1451                 rcu_read_lock_bh();
1452         if (statesnew & RCUTORTURE_RDR_IRQ)
1453                 local_irq_disable();
1454         if (statesnew & RCUTORTURE_RDR_PREEMPT)
1455                 preempt_disable();
1456         if (statesnew & RCUTORTURE_RDR_SCHED)
1457                 rcu_read_lock_sched();
1458         if (statesnew & RCUTORTURE_RDR_RCU_1)
1459                 idxnew1 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_1;
1460         if (statesnew & RCUTORTURE_RDR_RCU_2)
1461                 idxnew2 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_2;
1462
1463         /*
1464          * Next, remove old protection, in decreasing order of strength
1465          * to avoid unlock paths that aren't safe in the stronger
1466          * context. Namely: BH can not be enabled with disabled interrupts.
1467          * Additionally PREEMPT_RT requires that BH is enabled in preemptible
1468          * context.
1469          */
1470         if (statesold & RCUTORTURE_RDR_IRQ)
1471                 local_irq_enable();
1472         if (statesold & RCUTORTURE_RDR_PREEMPT)
1473                 preempt_enable();
1474         if (statesold & RCUTORTURE_RDR_SCHED)
1475                 rcu_read_unlock_sched();
1476         if (statesold & RCUTORTURE_RDR_BH)
1477                 local_bh_enable();
1478         if (statesold & RCUTORTURE_RDR_RBH)
1479                 rcu_read_unlock_bh();
1480         if (statesold & RCUTORTURE_RDR_RCU_2) {
1481                 cur_ops->readunlock((idxold2 >> RCUTORTURE_RDR_SHIFT_2) & 0x1);
1482                 WARN_ON_ONCE(idxnew2 != -1);
1483                 idxold2 = 0;
1484         }
1485         if (statesold & RCUTORTURE_RDR_RCU_1) {
1486                 bool lockit;
1487
1488                 lockit = !cur_ops->no_pi_lock && !statesnew && !(torture_random(trsp) & 0xffff);
1489                 if (lockit)
1490                         raw_spin_lock_irqsave(&current->pi_lock, flags);
1491                 cur_ops->readunlock((idxold1 >> RCUTORTURE_RDR_SHIFT_1) & 0x1);
1492                 WARN_ON_ONCE(idxnew1 != -1);
1493                 idxold1 = 0;
1494                 if (lockit)
1495                         raw_spin_unlock_irqrestore(&current->pi_lock, flags);
1496         }
1497
1498         /* Delay if neither beginning nor end and there was a change. */
1499         if ((statesnew || statesold) && *readstate && newstate)
1500                 cur_ops->read_delay(trsp, rtrsp);
1501
1502         /* Update the reader state. */
1503         if (idxnew1 == -1)
1504                 idxnew1 = idxold1 & RCUTORTURE_RDR_MASK_1;
1505         WARN_ON_ONCE(idxnew1 < 0);
1506         if (WARN_ON_ONCE((idxnew1 >> RCUTORTURE_RDR_SHIFT_1) > 1))
1507                 pr_info("Unexpected idxnew1 value of %#x\n", idxnew1);
1508         if (idxnew2 == -1)
1509                 idxnew2 = idxold2 & RCUTORTURE_RDR_MASK_2;
1510         WARN_ON_ONCE(idxnew2 < 0);
1511         WARN_ON_ONCE((idxnew2 >> RCUTORTURE_RDR_SHIFT_2) > 1);
1512         *readstate = idxnew1 | idxnew2 | newstate;
1513         WARN_ON_ONCE(*readstate < 0);
1514         if (WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT_2) > 1))
1515                 pr_info("Unexpected idxnew2 value of %#x\n", idxnew2);
1516 }
1517
1518 /* Return the biggest extendables mask given current RCU and boot parameters. */
1519 static int rcutorture_extend_mask_max(void)
1520 {
1521         int mask;
1522
1523         WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND);
1524         mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables;
1525         mask = mask | RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2;
1526         return mask;
1527 }
1528
1529 /* Return a random protection state mask, but with at least one bit set. */
1530 static int
1531 rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
1532 {
1533         int mask = rcutorture_extend_mask_max();
1534         unsigned long randmask1 = torture_random(trsp) >> 8;
1535         unsigned long randmask2 = randmask1 >> 3;
1536         unsigned long preempts = RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
1537         unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ;
1538         unsigned long bhs = RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
1539
1540         WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1);
1541         /* Mostly only one bit (need preemption!), sometimes lots of bits. */
1542         if (!(randmask1 & 0x7))
1543                 mask = mask & randmask2;
1544         else
1545                 mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));
1546
1547         // Can't have nested RCU reader without outer RCU reader.
1548         if (!(mask & RCUTORTURE_RDR_RCU_1) && (mask & RCUTORTURE_RDR_RCU_2)) {
1549                 if (oldmask & RCUTORTURE_RDR_RCU_1)
1550                         mask &= ~RCUTORTURE_RDR_RCU_2;
1551                 else
1552                         mask |= RCUTORTURE_RDR_RCU_1;
1553         }
1554
1555         /*
1556          * Can't enable bh w/irq disabled.
1557          */
1558         if (mask & RCUTORTURE_RDR_IRQ)
1559                 mask |= oldmask & bhs;
1560
1561         /*
1562          * Ideally these sequences would be detected in debug builds
1563          * (regardless of RT), but until then don't stop testing
1564          * them on non-RT.
1565          */
1566         if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
1567                 /* Can't modify BH in atomic context */
1568                 if (oldmask & preempts_irq)
1569                         mask &= ~bhs;
1570                 if ((oldmask | mask) & preempts_irq)
1571                         mask |= oldmask & bhs;
1572         }
1573
1574         return mask ?: RCUTORTURE_RDR_RCU_1;
1575 }
1576
1577 /*
1578  * Do a randomly selected number of extensions of an existing RCU read-side
1579  * critical section.
1580  */
1581 static struct rt_read_seg *
1582 rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
1583                        struct rt_read_seg *rtrsp)
1584 {
1585         int i;
1586         int j;
1587         int mask = rcutorture_extend_mask_max();
1588
1589         WARN_ON_ONCE(!*readstate); /* -Existing- RCU read-side critsect! */
1590         if (!((mask - 1) & mask))
1591                 return rtrsp;  /* Current RCU reader not extendable. */
1592         /* Bias towards larger numbers of loops. */
1593         i = (torture_random(trsp) >> 3);
1594         i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
1595         for (j = 0; j < i; j++) {
1596                 mask = rcutorture_extend_mask(*readstate, trsp);
1597                 rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
1598         }
1599         return &rtrsp[j];
1600 }
1601
1602 /*
1603  * Do one read-side critical section, returning false if there was
1604  * no data to read.  Can be invoked both from process context and
1605  * from a timer handler.
1606  */
1607 static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
1608 {
1609         unsigned long cookie;
1610         int i;
1611         unsigned long started;
1612         unsigned long completed;
1613         int newstate;
1614         struct rcu_torture *p;
1615         int pipe_count;
1616         int readstate = 0;
1617         struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS] = { { 0 } };
1618         struct rt_read_seg *rtrsp = &rtseg[0];
1619         struct rt_read_seg *rtrsp1;
1620         unsigned long long ts;
1621
1622         WARN_ON_ONCE(!rcu_is_watching());
1623         newstate = rcutorture_extend_mask(readstate, trsp);
1624         rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
1625         if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
1626                 cookie = cur_ops->get_gp_state();
1627         started = cur_ops->get_gp_seq();
1628         ts = rcu_trace_clock_local();
1629         p = rcu_dereference_check(rcu_torture_current,
1630                                   !cur_ops->readlock_held || cur_ops->readlock_held());
1631         if (p == NULL) {
1632                 /* Wait for rcu_torture_writer to get underway */
1633                 rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
1634                 return false;
1635         }
1636         if (p->rtort_mbtest == 0)
1637                 atomic_inc(&n_rcu_torture_mberror);
1638         rcu_torture_reader_do_mbchk(myid, p, trsp);
1639         rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
1640         preempt_disable();
1641         pipe_count = READ_ONCE(p->rtort_pipe_count);
1642         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
1643                 /* Should not happen, but... */
1644                 pipe_count = RCU_TORTURE_PIPE_LEN;
1645         }
1646         completed = cur_ops->get_gp_seq();
1647         if (pipe_count > 1) {
1648                 do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
1649                                           ts, started, completed);
1650                 rcu_ftrace_dump(DUMP_ALL);
1651         }
1652         __this_cpu_inc(rcu_torture_count[pipe_count]);
1653         completed = rcutorture_seq_diff(completed, started);
1654         if (completed > RCU_TORTURE_PIPE_LEN) {
1655                 /* Should not happen, but... */
1656                 completed = RCU_TORTURE_PIPE_LEN;
1657         }
1658         __this_cpu_inc(rcu_torture_batch[completed]);
1659         preempt_enable();
1660         if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
1661                 WARN_ONCE(cur_ops->poll_gp_state(cookie),
1662                           "%s: Cookie check 2 failed %s(%d) %lu->%lu\n",
1663                           __func__,
1664                           rcu_torture_writer_state_getname(),
1665                           rcu_torture_writer_state,
1666                           cookie, cur_ops->get_gp_state());
1667         rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
1668         WARN_ON_ONCE(readstate);
1669         // This next splat is expected behavior if leakpointer, especially
1670         // for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels.
1671         WARN_ON_ONCE(leakpointer && READ_ONCE(p->rtort_pipe_count) > 1);
1672
1673         /* If error or close call, record the sequence of reader protections. */
1674         if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
1675                 i = 0;
1676                 for (rtrsp1 = &rtseg[0]; rtrsp1 < rtrsp; rtrsp1++)
1677                         err_segs[i++] = *rtrsp1;
1678                 rt_read_nsegs = i;
1679         }
1680
1681         return true;
1682 }
1683
1684 static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);
1685
1686 /*
1687  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
1688  * incrementing the corresponding element of the pipeline array.  The
1689  * counter in the element should never be greater than 1, otherwise, the
1690  * RCU implementation is broken.
1691  */
1692 static void rcu_torture_timer(struct timer_list *unused)
1693 {
1694         atomic_long_inc(&n_rcu_torture_timers);
1695         (void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand), -1);
1696
1697         /* Test call_rcu() invocation from interrupt handler. */
1698         if (cur_ops->call) {
1699                 struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_NOWAIT);
1700
1701                 if (rhp)
1702                         cur_ops->call(rhp, rcu_torture_timer_cb);
1703         }
1704 }
1705
1706 /*
1707  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
1708  * incrementing the corresponding element of the pipeline array.  The
1709  * counter in the element should never be greater than 1, otherwise, the
1710  * RCU implementation is broken.
1711  */
1712 static int
1713 rcu_torture_reader(void *arg)
1714 {
1715         unsigned long lastsleep = jiffies;
1716         long myid = (long)arg;
1717         int mynumonline = myid;
1718         DEFINE_TORTURE_RANDOM(rand);
1719         struct timer_list t;
1720
1721         VERBOSE_TOROUT_STRING("rcu_torture_reader task started");
1722         set_user_nice(current, MAX_NICE);
1723         if (irqreader && cur_ops->irq_capable)
1724                 timer_setup_on_stack(&t, rcu_torture_timer, 0);
1725         tick_dep_set_task(current, TICK_DEP_BIT_RCU);
1726         do {
1727                 if (irqreader && cur_ops->irq_capable) {
1728                         if (!timer_pending(&t))
1729                                 mod_timer(&t, jiffies + 1);
1730                 }
1731                 if (!rcu_torture_one_read(&rand, myid) && !torture_must_stop())
1732                         schedule_timeout_interruptible(HZ);
1733                 if (time_after(jiffies, lastsleep) && !torture_must_stop()) {
1734                         torture_hrtimeout_us(500, 1000, &rand);
1735                         lastsleep = jiffies + 10;
1736                 }
1737                 while (torture_num_online_cpus() < mynumonline && !torture_must_stop())
1738                         schedule_timeout_interruptible(HZ / 5);
1739                 stutter_wait("rcu_torture_reader");
1740         } while (!torture_must_stop());
1741         if (irqreader && cur_ops->irq_capable) {
1742                 del_timer_sync(&t);
1743                 destroy_timer_on_stack(&t);
1744         }
1745         tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
1746         torture_kthread_stopping("rcu_torture_reader");
1747         return 0;
1748 }
1749
1750 /*
1751  * Randomly Toggle CPUs' callback-offload state.  This uses hrtimers to
1752  * increase race probabilities and fuzzes the interval between toggling.
1753  */
1754 static int rcu_nocb_toggle(void *arg)
1755 {
1756         int cpu;
1757         int maxcpu = -1;
1758         int oldnice = task_nice(current);
1759         long r;
1760         DEFINE_TORTURE_RANDOM(rand);
1761         ktime_t toggle_delay;
1762         unsigned long toggle_fuzz;
1763         ktime_t toggle_interval = ms_to_ktime(nocbs_toggle);
1764
1765         VERBOSE_TOROUT_STRING("rcu_nocb_toggle task started");
1766         while (!rcu_inkernel_boot_has_ended())
1767                 schedule_timeout_interruptible(HZ / 10);
1768         for_each_online_cpu(cpu)
1769                 maxcpu = cpu;
1770         WARN_ON(maxcpu < 0);
1771         if (toggle_interval > ULONG_MAX)
1772                 toggle_fuzz = ULONG_MAX >> 3;
1773         else
1774                 toggle_fuzz = toggle_interval >> 3;
1775         if (toggle_fuzz <= 0)
1776                 toggle_fuzz = NSEC_PER_USEC;
1777         do {
1778                 r = torture_random(&rand);
1779                 cpu = (r >> 4) % (maxcpu + 1);
1780                 if (r & 0x1) {
1781                         rcu_nocb_cpu_offload(cpu);
1782                         atomic_long_inc(&n_nocb_offload);
1783                 } else {
1784                         rcu_nocb_cpu_deoffload(cpu);
1785                         atomic_long_inc(&n_nocb_deoffload);
1786                 }
1787                 toggle_delay = torture_random(&rand) % toggle_fuzz + toggle_interval;
1788                 set_current_state(TASK_INTERRUPTIBLE);
1789                 schedule_hrtimeout(&toggle_delay, HRTIMER_MODE_REL);
1790                 if (stutter_wait("rcu_nocb_toggle"))
1791                         sched_set_normal(current, oldnice);
1792         } while (!torture_must_stop());
1793         torture_kthread_stopping("rcu_nocb_toggle");
1794         return 0;
1795 }
1796
1797 /*
1798  * Print torture statistics.  Caller must ensure that there is only
1799  * one call to this function at a given time!!!  This is normally
1800  * accomplished by relying on the module system to only have one copy
1801  * of the module loaded, and then by giving the rcu_torture_stats
1802  * kthread full control (or the init/cleanup functions when rcu_torture_stats
1803  * thread is not running).
1804  */
1805 static void
1806 rcu_torture_stats_print(void)
1807 {
1808         int cpu;
1809         int i;
1810         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1811         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
1812         struct rcu_torture *rtcp;
1813         static unsigned long rtcv_snap = ULONG_MAX;
1814         static bool splatted;
1815         struct task_struct *wtp;
1816
1817         for_each_possible_cpu(cpu) {
1818                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1819                         pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
1820                         batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
1821                 }
1822         }
1823         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
1824                 if (pipesummary[i] != 0)
1825                         break;
1826         }
1827
1828         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1829         rtcp = rcu_access_pointer(rcu_torture_current);
1830         pr_cont("rtc: %p %s: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
1831                 rtcp,
1832                 rtcp && !rcu_stall_is_suppressed_at_boot() ? "ver" : "VER",
1833                 rcu_torture_current_version,
1834                 list_empty(&rcu_torture_freelist),
1835                 atomic_read(&n_rcu_torture_alloc),
1836                 atomic_read(&n_rcu_torture_alloc_fail),
1837                 atomic_read(&n_rcu_torture_free));
1838         pr_cont("rtmbe: %d rtmbkf: %d/%d rtbe: %ld rtbke: %ld rtbre: %ld ",
1839                 atomic_read(&n_rcu_torture_mberror),
1840                 atomic_read(&n_rcu_torture_mbchk_fail), atomic_read(&n_rcu_torture_mbchk_tries),
1841                 n_rcu_torture_barrier_error,
1842                 n_rcu_torture_boost_ktrerror,
1843                 n_rcu_torture_boost_rterror);
1844         pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
1845                 n_rcu_torture_boost_failure,
1846                 n_rcu_torture_boosts,
1847                 atomic_long_read(&n_rcu_torture_timers));
1848         torture_onoff_stats();
1849         pr_cont("barrier: %ld/%ld:%ld ",
1850                 data_race(n_barrier_successes),
1851                 data_race(n_barrier_attempts),
1852                 data_race(n_rcu_torture_barrier_error));
1853         pr_cont("read-exits: %ld ", data_race(n_read_exits)); // Statistic.
1854         pr_cont("nocb-toggles: %ld:%ld\n",
1855                 atomic_long_read(&n_nocb_offload), atomic_long_read(&n_nocb_deoffload));
1856
1857         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1858         if (atomic_read(&n_rcu_torture_mberror) ||
1859             atomic_read(&n_rcu_torture_mbchk_fail) ||
1860             n_rcu_torture_barrier_error || n_rcu_torture_boost_ktrerror ||
1861             n_rcu_torture_boost_rterror || n_rcu_torture_boost_failure ||
1862             i > 1) {
1863                 pr_cont("%s", "!!! ");
1864                 atomic_inc(&n_rcu_torture_error);
1865                 WARN_ON_ONCE(atomic_read(&n_rcu_torture_mberror));
1866                 WARN_ON_ONCE(atomic_read(&n_rcu_torture_mbchk_fail));
1867                 WARN_ON_ONCE(n_rcu_torture_barrier_error);  // rcu_barrier()
1868                 WARN_ON_ONCE(n_rcu_torture_boost_ktrerror); // no boost kthread
1869                 WARN_ON_ONCE(n_rcu_torture_boost_rterror); // can't set RT prio
1870                 WARN_ON_ONCE(n_rcu_torture_boost_failure); // boost failed (TIMER_SOFTIRQ RT prio?)
1871                 WARN_ON_ONCE(i > 1); // Too-short grace period
1872         }
1873         pr_cont("Reader Pipe: ");
1874         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1875                 pr_cont(" %ld", pipesummary[i]);
1876         pr_cont("\n");
1877
1878         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1879         pr_cont("Reader Batch: ");
1880         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
1881                 pr_cont(" %ld", batchsummary[i]);
1882         pr_cont("\n");
1883
1884         pr_alert("%s%s ", torture_type, TORTURE_FLAG);
1885         pr_cont("Free-Block Circulation: ");
1886         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
1887                 pr_cont(" %d", atomic_read(&rcu_torture_wcount[i]));
1888         }
1889         pr_cont("\n");
1890
1891         if (cur_ops->stats)
1892                 cur_ops->stats();
1893         if (rtcv_snap == rcu_torture_current_version &&
1894             rcu_access_pointer(rcu_torture_current) &&
1895             !rcu_stall_is_suppressed()) {
1896                 int __maybe_unused flags = 0;
1897                 unsigned long __maybe_unused gp_seq = 0;
1898
1899                 rcutorture_get_gp_data(cur_ops->ttype,
1900                                        &flags, &gp_seq);
1901                 srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
1902                                         &flags, &gp_seq);
1903                 wtp = READ_ONCE(writer_task);
1904                 pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#x cpu %d\n",
1905                          rcu_torture_writer_state_getname(),
1906                          rcu_torture_writer_state, gp_seq, flags,
1907                          wtp == NULL ? ~0U : wtp->__state,
1908                          wtp == NULL ? -1 : (int)task_cpu(wtp));
1909                 if (!splatted && wtp) {
1910                         sched_show_task(wtp);
1911                         splatted = true;
1912                 }
1913                 if (cur_ops->gp_kthread_dbg)
1914                         cur_ops->gp_kthread_dbg();
1915                 rcu_ftrace_dump(DUMP_ALL);
1916         }
1917         rtcv_snap = rcu_torture_current_version;
1918 }
1919
1920 /*
1921  * Periodically prints torture statistics, if periodic statistics printing
1922  * was specified via the stat_interval module parameter.
1923  */
1924 static int
1925 rcu_torture_stats(void *arg)
1926 {
1927         VERBOSE_TOROUT_STRING("rcu_torture_stats task started");
1928         do {
1929                 schedule_timeout_interruptible(stat_interval * HZ);
1930                 rcu_torture_stats_print();
1931                 torture_shutdown_absorb("rcu_torture_stats");
1932         } while (!torture_must_stop());
1933         torture_kthread_stopping("rcu_torture_stats");
1934         return 0;
1935 }
1936
1937 /* Test mem_dump_obj() and friends.  */
1938 static void rcu_torture_mem_dump_obj(void)
1939 {
1940         struct rcu_head *rhp;
1941         struct kmem_cache *kcp;
1942         static int z;
1943
1944         kcp = kmem_cache_create("rcuscale", 136, 8, SLAB_STORE_USER, NULL);
1945         rhp = kmem_cache_alloc(kcp, GFP_KERNEL);
1946         pr_alert("mem_dump_obj() slab test: rcu_torture_stats = %px, &rhp = %px, rhp = %px, &z = %px\n", stats_task, &rhp, rhp, &z);
1947         pr_alert("mem_dump_obj(ZERO_SIZE_PTR):");
1948         mem_dump_obj(ZERO_SIZE_PTR);
1949         pr_alert("mem_dump_obj(NULL):");
1950         mem_dump_obj(NULL);
1951         pr_alert("mem_dump_obj(%px):", &rhp);
1952         mem_dump_obj(&rhp);
1953         pr_alert("mem_dump_obj(%px):", rhp);
1954         mem_dump_obj(rhp);
1955         pr_alert("mem_dump_obj(%px):", &rhp->func);
1956         mem_dump_obj(&rhp->func);
1957         pr_alert("mem_dump_obj(%px):", &z);
1958         mem_dump_obj(&z);
1959         kmem_cache_free(kcp, rhp);
1960         kmem_cache_destroy(kcp);
1961         rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
1962         pr_alert("mem_dump_obj() kmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
1963         pr_alert("mem_dump_obj(kmalloc %px):", rhp);
1964         mem_dump_obj(rhp);
1965         pr_alert("mem_dump_obj(kmalloc %px):", &rhp->func);
1966         mem_dump_obj(&rhp->func);
1967         kfree(rhp);
1968         rhp = vmalloc(4096);
1969         pr_alert("mem_dump_obj() vmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
1970         pr_alert("mem_dump_obj(vmalloc %px):", rhp);
1971         mem_dump_obj(rhp);
1972         pr_alert("mem_dump_obj(vmalloc %px):", &rhp->func);
1973         mem_dump_obj(&rhp->func);
1974         vfree(rhp);
1975 }
1976
1977 static void
1978 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
1979 {
1980         pr_alert("%s" TORTURE_FLAG
1981                  "--- %s: nreaders=%d nfakewriters=%d "
1982                  "stat_interval=%d verbose=%d test_no_idle_hz=%d "
1983                  "shuffle_interval=%d stutter=%d irqreader=%d "
1984                  "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
1985                  "test_boost=%d/%d test_boost_interval=%d "
1986                  "test_boost_duration=%d shutdown_secs=%d "
1987                  "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
1988                  "stall_cpu_block=%d "
1989                  "n_barrier_cbs=%d "
1990                  "onoff_interval=%d onoff_holdoff=%d "
1991                  "read_exit_delay=%d read_exit_burst=%d "
1992                  "nocbs_nthreads=%d nocbs_toggle=%d\n",
1993                  torture_type, tag, nrealreaders, nfakewriters,
1994                  stat_interval, verbose, test_no_idle_hz, shuffle_interval,
1995                  stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
1996                  test_boost, cur_ops->can_boost,
1997                  test_boost_interval, test_boost_duration, shutdown_secs,
1998                  stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
1999                  stall_cpu_block,
2000                  n_barrier_cbs,
2001                  onoff_interval, onoff_holdoff,
2002                  read_exit_delay, read_exit_burst,
2003                  nocbs_nthreads, nocbs_toggle);
2004 }
2005
2006 static int rcutorture_booster_cleanup(unsigned int cpu)
2007 {
2008         struct task_struct *t;
2009
2010         if (boost_tasks[cpu] == NULL)
2011                 return 0;
2012         mutex_lock(&boost_mutex);
2013         t = boost_tasks[cpu];
2014         boost_tasks[cpu] = NULL;
2015         rcu_torture_enable_rt_throttle();
2016         mutex_unlock(&boost_mutex);
2017
2018         /* This must be outside of the mutex, otherwise deadlock! */
2019         torture_stop_kthread(rcu_torture_boost, t);
2020         return 0;
2021 }
2022
2023 static int rcutorture_booster_init(unsigned int cpu)
2024 {
2025         int retval;
2026
2027         if (boost_tasks[cpu] != NULL)
2028                 return 0;  /* Already created, nothing more to do. */
2029
2030         /* Don't allow time recalculation while creating a new task. */
2031         mutex_lock(&boost_mutex);
2032         rcu_torture_disable_rt_throttle();
2033         VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
2034         boost_tasks[cpu] = kthread_run_on_cpu(rcu_torture_boost, NULL,
2035                                               cpu, "rcu_torture_boost_%u");
2036         if (IS_ERR(boost_tasks[cpu])) {
2037                 retval = PTR_ERR(boost_tasks[cpu]);
2038                 VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed");
2039                 n_rcu_torture_boost_ktrerror++;
2040                 boost_tasks[cpu] = NULL;
2041                 mutex_unlock(&boost_mutex);
2042                 return retval;
2043         }
2044         mutex_unlock(&boost_mutex);
2045         return 0;
2046 }
2047
2048 /*
2049  * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then
2050  * induces a CPU stall for the time specified by stall_cpu.
2051  */
2052 static int rcu_torture_stall(void *args)
2053 {
2054         int idx;
2055         unsigned long stop_at;
2056
2057         VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
2058         if (stall_cpu_holdoff > 0) {
2059                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
2060                 schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
2061                 VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
2062         }
2063         if (!kthread_should_stop() && stall_gp_kthread > 0) {
2064                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin GP stall");
2065                 rcu_gp_set_torture_wait(stall_gp_kthread * HZ);
2066                 for (idx = 0; idx < stall_gp_kthread + 2; idx++) {
2067                         if (kthread_should_stop())
2068                                 break;
2069                         schedule_timeout_uninterruptible(HZ);
2070                 }
2071         }
2072         if (!kthread_should_stop() && stall_cpu > 0) {
2073                 VERBOSE_TOROUT_STRING("rcu_torture_stall begin CPU stall");
2074                 stop_at = ktime_get_seconds() + stall_cpu;
2075                 /* RCU CPU stall is expected behavior in following code. */
2076                 idx = cur_ops->readlock();
2077                 if (stall_cpu_irqsoff)
2078                         local_irq_disable();
2079                 else if (!stall_cpu_block)
2080                         preempt_disable();
2081                 pr_alert("%s start on CPU %d.\n",
2082                           __func__, raw_smp_processor_id());
2083                 while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
2084                                     stop_at))
2085                         if (stall_cpu_block) {
2086 #ifdef CONFIG_PREEMPTION
2087                                 preempt_schedule();
2088 #else
2089                                 schedule_timeout_uninterruptible(HZ);
2090 #endif
2091                         } else if (stall_no_softlockup) {
2092                                 touch_softlockup_watchdog();
2093                         }
2094                 if (stall_cpu_irqsoff)
2095                         local_irq_enable();
2096                 else if (!stall_cpu_block)
2097                         preempt_enable();
2098                 cur_ops->readunlock(idx);
2099         }
2100         pr_alert("%s end.\n", __func__);
2101         torture_shutdown_absorb("rcu_torture_stall");
2102         while (!kthread_should_stop())
2103                 schedule_timeout_interruptible(10 * HZ);
2104         return 0;
2105 }
2106
2107 /* Spawn CPU-stall kthread, if stall_cpu specified. */
2108 static int __init rcu_torture_stall_init(void)
2109 {
2110         if (stall_cpu <= 0 && stall_gp_kthread <= 0)
2111                 return 0;
2112         return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
2113 }
2114
2115 /* State structure for forward-progress self-propagating RCU callback. */
2116 struct fwd_cb_state {
2117         struct rcu_head rh;
2118         int stop;
2119 };
2120
2121 /*
2122  * Forward-progress self-propagating RCU callback function.  Because
2123  * callbacks run from softirq, this function is an implicit RCU read-side
2124  * critical section.
2125  */
2126 static void rcu_torture_fwd_prog_cb(struct rcu_head *rhp)
2127 {
2128         struct fwd_cb_state *fcsp = container_of(rhp, struct fwd_cb_state, rh);
2129
2130         if (READ_ONCE(fcsp->stop)) {
2131                 WRITE_ONCE(fcsp->stop, 2);
2132                 return;
2133         }
2134         cur_ops->call(&fcsp->rh, rcu_torture_fwd_prog_cb);
2135 }
2136
2137 /* State for continuous-flood RCU callbacks. */
2138 struct rcu_fwd_cb {
2139         struct rcu_head rh;
2140         struct rcu_fwd_cb *rfc_next;
2141         struct rcu_fwd *rfc_rfp;
2142         int rfc_gps;
2143 };
2144
2145 #define MAX_FWD_CB_JIFFIES      (8 * HZ) /* Maximum CB test duration. */
2146 #define MIN_FWD_CB_LAUNDERS     3       /* This many CB invocations to count. */
2147 #define MIN_FWD_CBS_LAUNDERED   100     /* Number of counted CBs. */
2148 #define FWD_CBS_HIST_DIV        10      /* Histogram buckets/second. */
2149 #define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))
2150
2151 struct rcu_launder_hist {
2152         long n_launders;
2153         unsigned long launder_gp_seq;
2154 };
2155
2156 struct rcu_fwd {
2157         spinlock_t rcu_fwd_lock;
2158         struct rcu_fwd_cb *rcu_fwd_cb_head;
2159         struct rcu_fwd_cb **rcu_fwd_cb_tail;
2160         long n_launders_cb;
2161         unsigned long rcu_fwd_startat;
2162         struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
2163         unsigned long rcu_launder_gp_seq_start;
2164         int rcu_fwd_id;
2165 };
2166
2167 static DEFINE_MUTEX(rcu_fwd_mutex);
2168 static struct rcu_fwd *rcu_fwds;
2169 static unsigned long rcu_fwd_seq;
2170 static atomic_long_t rcu_fwd_max_cbs;
2171 static bool rcu_fwd_emergency_stop;
2172
2173 static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
2174 {
2175         unsigned long gps;
2176         unsigned long gps_old;
2177         int i;
2178         int j;
2179
2180         for (i = ARRAY_SIZE(rfp->n_launders_hist) - 1; i > 0; i--)
2181                 if (rfp->n_launders_hist[i].n_launders > 0)
2182                         break;
2183         mutex_lock(&rcu_fwd_mutex); // Serialize histograms.
2184         pr_alert("%s: Callback-invocation histogram %d (duration %lu jiffies):",
2185                  __func__, rfp->rcu_fwd_id, jiffies - rfp->rcu_fwd_startat);
2186         gps_old = rfp->rcu_launder_gp_seq_start;
2187         for (j = 0; j <= i; j++) {
2188                 gps = rfp->n_launders_hist[j].launder_gp_seq;
2189                 pr_cont(" %ds/%d: %ld:%ld",
2190                         j + 1, FWD_CBS_HIST_DIV,
2191                         rfp->n_launders_hist[j].n_launders,
2192                         rcutorture_seq_diff(gps, gps_old));
2193                 gps_old = gps;
2194         }
2195         pr_cont("\n");
2196         mutex_unlock(&rcu_fwd_mutex);
2197 }
2198
2199 /* Callback function for continuous-flood RCU callbacks. */
2200 static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
2201 {
2202         unsigned long flags;
2203         int i;
2204         struct rcu_fwd_cb *rfcp = container_of(rhp, struct rcu_fwd_cb, rh);
2205         struct rcu_fwd_cb **rfcpp;
2206         struct rcu_fwd *rfp = rfcp->rfc_rfp;
2207
2208         rfcp->rfc_next = NULL;
2209         rfcp->rfc_gps++;
2210         spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
2211         rfcpp = rfp->rcu_fwd_cb_tail;
2212         rfp->rcu_fwd_cb_tail = &rfcp->rfc_next;
2213         WRITE_ONCE(*rfcpp, rfcp);
2214         WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1);
2215         i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
2216         if (i >= ARRAY_SIZE(rfp->n_launders_hist))
2217                 i = ARRAY_SIZE(rfp->n_launders_hist) - 1;
2218         rfp->n_launders_hist[i].n_launders++;
2219         rfp->n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();
2220         spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
2221 }
2222
2223 // Give the scheduler a chance, even on nohz_full CPUs.
2224 static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)
2225 {
2226         if (IS_ENABLED(CONFIG_PREEMPTION) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
2227                 // Real call_rcu() floods hit userspace, so emulate that.
2228                 if (need_resched() || (iter & 0xfff))
2229                         schedule();
2230                 return;
2231         }
2232         // No userspace emulation: CB invocation throttles call_rcu()
2233         cond_resched();
2234 }
2235
2236 /*
2237  * Free all callbacks on the rcu_fwd_cb_head list, either because the
2238  * test is over or because we hit an OOM event.
2239  */
2240 static unsigned long rcu_torture_fwd_prog_cbfree(struct rcu_fwd *rfp)
2241 {
2242         unsigned long flags;
2243         unsigned long freed = 0;
2244         struct rcu_fwd_cb *rfcp;
2245
2246         for (;;) {
2247                 spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
2248                 rfcp = rfp->rcu_fwd_cb_head;
2249                 if (!rfcp) {
2250                         spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
2251                         break;
2252                 }
2253                 rfp->rcu_fwd_cb_head = rfcp->rfc_next;
2254                 if (!rfp->rcu_fwd_cb_head)
2255                         rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
2256                 spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
2257                 kfree(rfcp);
2258                 freed++;
2259                 rcu_torture_fwd_prog_cond_resched(freed);
2260                 if (tick_nohz_full_enabled()) {
2261                         local_irq_save(flags);
2262                         rcu_momentary_dyntick_idle();
2263                         local_irq_restore(flags);
2264                 }
2265         }
2266         return freed;
2267 }
2268
2269 /* Carry out need_resched()/cond_resched() forward-progress testing. */
2270 static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
2271                                     int *tested, int *tested_tries)
2272 {
2273         unsigned long cver;
2274         unsigned long dur;
2275         struct fwd_cb_state fcs;
2276         unsigned long gps;
2277         int idx;
2278         int sd;
2279         int sd4;
2280         bool selfpropcb = false;
2281         unsigned long stopat;
2282         static DEFINE_TORTURE_RANDOM(trs);
2283
2284         if (!cur_ops->sync)
2285                 return; // Cannot do need_resched() forward progress testing without ->sync.
2286         if (cur_ops->call && cur_ops->cb_barrier) {
2287                 init_rcu_head_on_stack(&fcs.rh);
2288                 selfpropcb = true;
2289         }
2290
2291         /* Tight loop containing cond_resched(). */
2292         WRITE_ONCE(rcu_fwd_cb_nodelay, true);
2293         cur_ops->sync(); /* Later readers see above write. */
2294         if  (selfpropcb) {
2295                 WRITE_ONCE(fcs.stop, 0);
2296                 cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
2297         }
2298         cver = READ_ONCE(rcu_torture_current_version);
2299         gps = cur_ops->get_gp_seq();
2300         sd = cur_ops->stall_dur() + 1;
2301         sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
2302         dur = sd4 + torture_random(&trs) % (sd - sd4);
2303         WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
2304         stopat = rfp->rcu_fwd_startat + dur;
2305         while (time_before(jiffies, stopat) &&
2306                !shutdown_time_arrived() &&
2307                !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
2308                 idx = cur_ops->readlock();
2309                 udelay(10);
2310                 cur_ops->readunlock(idx);
2311                 if (!fwd_progress_need_resched || need_resched())
2312                         cond_resched();
2313         }
2314         (*tested_tries)++;
2315         if (!time_before(jiffies, stopat) &&
2316             !shutdown_time_arrived() &&
2317             !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
2318                 (*tested)++;
2319                 cver = READ_ONCE(rcu_torture_current_version) - cver;
2320                 gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
2321                 WARN_ON(!cver && gps < 2);
2322                 pr_alert("%s: %d Duration %ld cver %ld gps %ld\n", __func__,
2323                          rfp->rcu_fwd_id, dur, cver, gps);
2324         }
2325         if (selfpropcb) {
2326                 WRITE_ONCE(fcs.stop, 1);
2327                 cur_ops->sync(); /* Wait for running CB to complete. */
2328                 cur_ops->cb_barrier(); /* Wait for queued callbacks. */
2329         }
2330
2331         if (selfpropcb) {
2332                 WARN_ON(READ_ONCE(fcs.stop) != 2);
2333                 destroy_rcu_head_on_stack(&fcs.rh);
2334         }
2335         schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
2336         WRITE_ONCE(rcu_fwd_cb_nodelay, false);
2337 }
2338
2339 /* Carry out call_rcu() forward-progress testing. */
2340 static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
2341 {
2342         unsigned long cver;
2343         unsigned long flags;
2344         unsigned long gps;
2345         int i;
2346         long n_launders;
2347         long n_launders_cb_snap;
2348         long n_launders_sa;
2349         long n_max_cbs;
2350         long n_max_gps;
2351         struct rcu_fwd_cb *rfcp;
2352         struct rcu_fwd_cb *rfcpn;
2353         unsigned long stopat;
2354         unsigned long stoppedat;
2355
2356         if (READ_ONCE(rcu_fwd_emergency_stop))
2357                 return; /* Get out of the way quickly, no GP wait! */
2358         if (!cur_ops->call)
2359                 return; /* Can't do call_rcu() fwd prog without ->call. */
2360
2361         /* Loop continuously posting RCU callbacks. */
2362         WRITE_ONCE(rcu_fwd_cb_nodelay, true);
2363         cur_ops->sync(); /* Later readers see above write. */
2364         WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
2365         stopat = rfp->rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
2366         n_launders = 0;
2367         rfp->n_launders_cb = 0; // Hoist initialization for multi-kthread
2368         n_launders_sa = 0;
2369         n_max_cbs = 0;
2370         n_max_gps = 0;
2371         for (i = 0; i < ARRAY_SIZE(rfp->n_launders_hist); i++)
2372                 rfp->n_launders_hist[i].n_launders = 0;
2373         cver = READ_ONCE(rcu_torture_current_version);
2374         gps = cur_ops->get_gp_seq();
2375         rfp->rcu_launder_gp_seq_start = gps;
2376         tick_dep_set_task(current, TICK_DEP_BIT_RCU);
2377         while (time_before(jiffies, stopat) &&
2378                !shutdown_time_arrived() &&
2379                !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
2380                 rfcp = READ_ONCE(rfp->rcu_fwd_cb_head);
2381                 rfcpn = NULL;
2382                 if (rfcp)
2383                         rfcpn = READ_ONCE(rfcp->rfc_next);
2384                 if (rfcpn) {
2385                         if (rfcp->rfc_gps >= MIN_FWD_CB_LAUNDERS &&
2386                             ++n_max_gps >= MIN_FWD_CBS_LAUNDERED)
2387                                 break;
2388                         rfp->rcu_fwd_cb_head = rfcpn;
2389                         n_launders++;
2390                         n_launders_sa++;
2391                 } else if (!cur_ops->cbflood_max || cur_ops->cbflood_max > n_max_cbs) {
2392                         rfcp = kmalloc(sizeof(*rfcp), GFP_KERNEL);
2393                         if (WARN_ON_ONCE(!rfcp)) {
2394                                 schedule_timeout_interruptible(1);
2395                                 continue;
2396                         }
2397                         n_max_cbs++;
2398                         n_launders_sa = 0;
2399                         rfcp->rfc_gps = 0;
2400                         rfcp->rfc_rfp = rfp;
2401                 } else {
2402                         rfcp = NULL;
2403                 }
2404                 if (rfcp)
2405                         cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
2406                 rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
2407                 if (tick_nohz_full_enabled()) {
2408                         local_irq_save(flags);
2409                         rcu_momentary_dyntick_idle();
2410                         local_irq_restore(flags);
2411                 }
2412         }
2413         stoppedat = jiffies;
2414         n_launders_cb_snap = READ_ONCE(rfp->n_launders_cb);
2415         cver = READ_ONCE(rcu_torture_current_version) - cver;
2416         gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
2417         cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
2418         (void)rcu_torture_fwd_prog_cbfree(rfp);
2419
2420         if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop) &&
2421             !shutdown_time_arrived()) {
2422                 WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
2423                 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",
2424                          __func__,
2425                          stoppedat - rfp->rcu_fwd_startat, jiffies - stoppedat,
2426                          n_launders + n_max_cbs - n_launders_cb_snap,
2427                          n_launders, n_launders_sa,
2428                          n_max_gps, n_max_cbs, cver, gps);
2429                 atomic_long_add(n_max_cbs, &rcu_fwd_max_cbs);
2430                 rcu_torture_fwd_cb_hist(rfp);
2431         }
2432         schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
2433         tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
2434         WRITE_ONCE(rcu_fwd_cb_nodelay, false);
2435 }
2436
2437
2438 /*
2439  * OOM notifier, but this only prints diagnostic information for the
2440  * current forward-progress test.
2441  */
2442 static int rcutorture_oom_notify(struct notifier_block *self,
2443                                  unsigned long notused, void *nfreed)
2444 {
2445         int i;
2446         long ncbs;
2447         struct rcu_fwd *rfp;
2448
2449         mutex_lock(&rcu_fwd_mutex);
2450         rfp = rcu_fwds;
2451         if (!rfp) {
2452                 mutex_unlock(&rcu_fwd_mutex);
2453                 return NOTIFY_OK;
2454         }
2455         WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
2456              __func__);
2457         for (i = 0; i < fwd_progress; i++) {
2458                 rcu_torture_fwd_cb_hist(&rfp[i]);
2459                 rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rfp[i].rcu_fwd_startat)) / 2);
2460         }
2461         WRITE_ONCE(rcu_fwd_emergency_stop, true);
2462         smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
2463         ncbs = 0;
2464         for (i = 0; i < fwd_progress; i++)
2465                 ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
2466         pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
2467         rcu_barrier();
2468         ncbs = 0;
2469         for (i = 0; i < fwd_progress; i++)
2470                 ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
2471         pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
2472         rcu_barrier();
2473         ncbs = 0;
2474         for (i = 0; i < fwd_progress; i++)
2475                 ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
2476         pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
2477         smp_mb(); /* Frees before return to avoid redoing OOM. */
2478         (*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */
2479         pr_info("%s returning after OOM processing.\n", __func__);
2480         mutex_unlock(&rcu_fwd_mutex);
2481         return NOTIFY_OK;
2482 }
2483
2484 static struct notifier_block rcutorture_oom_nb = {
2485         .notifier_call = rcutorture_oom_notify
2486 };
2487
2488 /* Carry out grace-period forward-progress testing. */
2489 static int rcu_torture_fwd_prog(void *args)
2490 {
2491         bool firsttime = true;
2492         long max_cbs;
2493         int oldnice = task_nice(current);
2494         unsigned long oldseq = READ_ONCE(rcu_fwd_seq);
2495         struct rcu_fwd *rfp = args;
2496         int tested = 0;
2497         int tested_tries = 0;
2498
2499         VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
2500         rcu_bind_current_to_nocb();
2501         if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST))
2502                 set_user_nice(current, MAX_NICE);
2503         do {
2504                 if (!rfp->rcu_fwd_id) {
2505                         schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
2506                         WRITE_ONCE(rcu_fwd_emergency_stop, false);
2507                         if (!firsttime) {
2508                                 max_cbs = atomic_long_xchg(&rcu_fwd_max_cbs, 0);
2509                                 pr_alert("%s n_max_cbs: %ld\n", __func__, max_cbs);
2510                         }
2511                         firsttime = false;
2512                         WRITE_ONCE(rcu_fwd_seq, rcu_fwd_seq + 1);
2513                 } else {
2514                         while (READ_ONCE(rcu_fwd_seq) == oldseq)
2515                                 schedule_timeout_interruptible(1);
2516                         oldseq = READ_ONCE(rcu_fwd_seq);
2517                 }
2518                 pr_alert("%s: Starting forward-progress test %d\n", __func__, rfp->rcu_fwd_id);
2519                 if (rcu_inkernel_boot_has_ended() && torture_num_online_cpus() > rfp->rcu_fwd_id)
2520                         rcu_torture_fwd_prog_cr(rfp);
2521                 if ((cur_ops->stall_dur && cur_ops->stall_dur() > 0) &&
2522                     (!IS_ENABLED(CONFIG_TINY_RCU) ||
2523                      (rcu_inkernel_boot_has_ended() &&
2524                       torture_num_online_cpus() > rfp->rcu_fwd_id)))
2525                         rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
2526
2527                 /* Avoid slow periods, better to test when busy. */
2528                 if (stutter_wait("rcu_torture_fwd_prog"))
2529                         sched_set_normal(current, oldnice);
2530         } while (!torture_must_stop());
2531         /* Short runs might not contain a valid forward-progress attempt. */
2532         if (!rfp->rcu_fwd_id) {
2533                 WARN_ON(!tested && tested_tries >= 5);
2534                 pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
2535         }
2536         torture_kthread_stopping("rcu_torture_fwd_prog");
2537         return 0;
2538 }
2539
2540 /* If forward-progress checking is requested and feasible, spawn the thread. */
2541 static int __init rcu_torture_fwd_prog_init(void)
2542 {
2543         int i;
2544         int ret = 0;
2545         struct rcu_fwd *rfp;
2546
2547         if (!fwd_progress)
2548                 return 0; /* Not requested, so don't do it. */
2549         if (fwd_progress >= nr_cpu_ids) {
2550                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Limiting fwd_progress to # CPUs.\n");
2551                 fwd_progress = nr_cpu_ids;
2552         } else if (fwd_progress < 0) {
2553                 fwd_progress = nr_cpu_ids;
2554         }
2555         if ((!cur_ops->sync && !cur_ops->call) ||
2556             (!cur_ops->cbflood_max && (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0)) ||
2557             cur_ops == &rcu_busted_ops) {
2558                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
2559                 fwd_progress = 0;
2560                 return 0;
2561         }
2562         if (stall_cpu > 0) {
2563                 VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
2564                 fwd_progress = 0;
2565                 if (IS_MODULE(CONFIG_RCU_TORTURE_TEST))
2566                         return -EINVAL; /* In module, can fail back to user. */
2567                 WARN_ON(1); /* Make sure rcutorture notices conflict. */
2568                 return 0;
2569         }
2570         if (fwd_progress_holdoff <= 0)
2571                 fwd_progress_holdoff = 1;
2572         if (fwd_progress_div <= 0)
2573                 fwd_progress_div = 4;
2574         rfp = kcalloc(fwd_progress, sizeof(*rfp), GFP_KERNEL);
2575         fwd_prog_tasks = kcalloc(fwd_progress, sizeof(*fwd_prog_tasks), GFP_KERNEL);
2576         if (!rfp || !fwd_prog_tasks) {
2577                 kfree(rfp);
2578                 kfree(fwd_prog_tasks);
2579                 fwd_prog_tasks = NULL;
2580                 fwd_progress = 0;
2581                 return -ENOMEM;
2582         }
2583         for (i = 0; i < fwd_progress; i++) {
2584                 spin_lock_init(&rfp[i].rcu_fwd_lock);
2585                 rfp[i].rcu_fwd_cb_tail = &rfp[i].rcu_fwd_cb_head;
2586                 rfp[i].rcu_fwd_id = i;
2587         }
2588         mutex_lock(&rcu_fwd_mutex);
2589         rcu_fwds = rfp;
2590         mutex_unlock(&rcu_fwd_mutex);
2591         register_oom_notifier(&rcutorture_oom_nb);
2592         for (i = 0; i < fwd_progress; i++) {
2593                 ret = torture_create_kthread(rcu_torture_fwd_prog, &rcu_fwds[i], fwd_prog_tasks[i]);
2594                 if (ret) {
2595                         fwd_progress = i;
2596                         return ret;
2597                 }
2598         }
2599         return 0;
2600 }
2601
2602 static void rcu_torture_fwd_prog_cleanup(void)
2603 {
2604         int i;
2605         struct rcu_fwd *rfp;
2606
2607         if (!rcu_fwds || !fwd_prog_tasks)
2608                 return;
2609         for (i = 0; i < fwd_progress; i++)
2610                 torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_tasks[i]);
2611         unregister_oom_notifier(&rcutorture_oom_nb);
2612         mutex_lock(&rcu_fwd_mutex);
2613         rfp = rcu_fwds;
2614         rcu_fwds = NULL;
2615         mutex_unlock(&rcu_fwd_mutex);
2616         kfree(rfp);
2617         kfree(fwd_prog_tasks);
2618         fwd_prog_tasks = NULL;
2619 }
2620
2621 /* Callback function for RCU barrier testing. */
2622 static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
2623 {
2624         atomic_inc(&barrier_cbs_invoked);
2625 }
2626
2627 /* IPI handler to get callback posted on desired CPU, if online. */
2628 static void rcu_torture_barrier1cb(void *rcu_void)
2629 {
2630         struct rcu_head *rhp = rcu_void;
2631
2632         cur_ops->call(rhp, rcu_torture_barrier_cbf);
2633 }
2634
2635 /* kthread function to register callbacks used to test RCU barriers. */
2636 static int rcu_torture_barrier_cbs(void *arg)
2637 {
2638         long myid = (long)arg;
2639         bool lastphase = false;
2640         bool newphase;
2641         struct rcu_head rcu;
2642
2643         init_rcu_head_on_stack(&rcu);
2644         VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started");
2645         set_user_nice(current, MAX_NICE);
2646         do {
2647                 wait_event(barrier_cbs_wq[myid],
2648                            (newphase =
2649                             smp_load_acquire(&barrier_phase)) != lastphase ||
2650                            torture_must_stop());
2651                 lastphase = newphase;
2652                 if (torture_must_stop())
2653                         break;
2654                 /*
2655                  * The above smp_load_acquire() ensures barrier_phase load
2656                  * is ordered before the following ->call().
2657                  */
2658                 if (smp_call_function_single(myid, rcu_torture_barrier1cb,
2659                                              &rcu, 1)) {
2660                         // IPI failed, so use direct call from current CPU.
2661                         cur_ops->call(&rcu, rcu_torture_barrier_cbf);
2662                 }
2663                 if (atomic_dec_and_test(&barrier_cbs_count))
2664                         wake_up(&barrier_wq);
2665         } while (!torture_must_stop());
2666         if (cur_ops->cb_barrier != NULL)
2667                 cur_ops->cb_barrier();
2668         destroy_rcu_head_on_stack(&rcu);
2669         torture_kthread_stopping("rcu_torture_barrier_cbs");
2670         return 0;
2671 }
2672
2673 /* kthread function to drive and coordinate RCU barrier testing. */
2674 static int rcu_torture_barrier(void *arg)
2675 {
2676         int i;
2677
2678         VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting");
2679         do {
2680                 atomic_set(&barrier_cbs_invoked, 0);
2681                 atomic_set(&barrier_cbs_count, n_barrier_cbs);
2682                 /* Ensure barrier_phase ordered after prior assignments. */
2683                 smp_store_release(&barrier_phase, !barrier_phase);
2684                 for (i = 0; i < n_barrier_cbs; i++)
2685                         wake_up(&barrier_cbs_wq[i]);
2686                 wait_event(barrier_wq,
2687                            atomic_read(&barrier_cbs_count) == 0 ||
2688                            torture_must_stop());
2689                 if (torture_must_stop())
2690                         break;
2691                 n_barrier_attempts++;
2692                 cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
2693                 if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
2694                         n_rcu_torture_barrier_error++;
2695                         pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
2696                                atomic_read(&barrier_cbs_invoked),
2697                                n_barrier_cbs);
2698                         WARN_ON(1);
2699                         // Wait manually for the remaining callbacks
2700                         i = 0;
2701                         do {
2702                                 if (WARN_ON(i++ > HZ))
2703                                         i = INT_MIN;
2704                                 schedule_timeout_interruptible(1);
2705                                 cur_ops->cb_barrier();
2706                         } while (atomic_read(&barrier_cbs_invoked) !=
2707                                  n_barrier_cbs &&
2708                                  !torture_must_stop());
2709                         smp_mb(); // Can't trust ordering if broken.
2710                         if (!torture_must_stop())
2711                                 pr_err("Recovered: barrier_cbs_invoked = %d\n",
2712                                        atomic_read(&barrier_cbs_invoked));
2713                 } else {
2714                         n_barrier_successes++;
2715                 }
2716                 schedule_timeout_interruptible(HZ / 10);
2717         } while (!torture_must_stop());
2718         torture_kthread_stopping("rcu_torture_barrier");
2719         return 0;
2720 }
2721
2722 /* Initialize RCU barrier testing. */
2723 static int rcu_torture_barrier_init(void)
2724 {
2725         int i;
2726         int ret;
2727
2728         if (n_barrier_cbs <= 0)
2729                 return 0;
2730         if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
2731                 pr_alert("%s" TORTURE_FLAG
2732                          " Call or barrier ops missing for %s,\n",
2733                          torture_type, cur_ops->name);
2734                 pr_alert("%s" TORTURE_FLAG
2735                          " RCU barrier testing omitted from run.\n",
2736                          torture_type);
2737                 return 0;
2738         }
2739         atomic_set(&barrier_cbs_count, 0);
2740         atomic_set(&barrier_cbs_invoked, 0);
2741         barrier_cbs_tasks =
2742                 kcalloc(n_barrier_cbs, sizeof(barrier_cbs_tasks[0]),
2743                         GFP_KERNEL);
2744         barrier_cbs_wq =
2745                 kcalloc(n_barrier_cbs, sizeof(barrier_cbs_wq[0]), GFP_KERNEL);
2746         if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
2747                 return -ENOMEM;
2748         for (i = 0; i < n_barrier_cbs; i++) {
2749                 init_waitqueue_head(&barrier_cbs_wq[i]);
2750                 ret = torture_create_kthread(rcu_torture_barrier_cbs,
2751                                              (void *)(long)i,
2752                                              barrier_cbs_tasks[i]);
2753                 if (ret)
2754                         return ret;
2755         }
2756         return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task);
2757 }
2758
2759 /* Clean up after RCU barrier testing. */
2760 static void rcu_torture_barrier_cleanup(void)
2761 {
2762         int i;
2763
2764         torture_stop_kthread(rcu_torture_barrier, barrier_task);
2765         if (barrier_cbs_tasks != NULL) {
2766                 for (i = 0; i < n_barrier_cbs; i++)
2767                         torture_stop_kthread(rcu_torture_barrier_cbs,
2768                                              barrier_cbs_tasks[i]);
2769                 kfree(barrier_cbs_tasks);
2770                 barrier_cbs_tasks = NULL;
2771         }
2772         if (barrier_cbs_wq != NULL) {
2773                 kfree(barrier_cbs_wq);
2774                 barrier_cbs_wq = NULL;
2775         }
2776 }
2777
2778 static bool rcu_torture_can_boost(void)
2779 {
2780         static int boost_warn_once;
2781         int prio;
2782
2783         if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2)
2784                 return false;
2785         if (!cur_ops->start_gp_poll || !cur_ops->poll_gp_state)
2786                 return false;
2787
2788         prio = rcu_get_gp_kthreads_prio();
2789         if (!prio)
2790                 return false;
2791
2792         if (prio < 2) {
2793                 if (boost_warn_once == 1)
2794                         return false;
2795
2796                 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);
2797                 boost_warn_once = 1;
2798                 return false;
2799         }
2800
2801         return true;
2802 }
2803
2804 static bool read_exit_child_stop;
2805 static bool read_exit_child_stopped;
2806 static wait_queue_head_t read_exit_wq;
2807
2808 // Child kthread which just does an rcutorture reader and exits.
2809 static int rcu_torture_read_exit_child(void *trsp_in)
2810 {
2811         struct torture_random_state *trsp = trsp_in;
2812
2813         set_user_nice(current, MAX_NICE);
2814         // Minimize time between reading and exiting.
2815         while (!kthread_should_stop())
2816                 schedule_timeout_uninterruptible(1);
2817         (void)rcu_torture_one_read(trsp, -1);
2818         return 0;
2819 }
2820
2821 // Parent kthread which creates and destroys read-exit child kthreads.
2822 static int rcu_torture_read_exit(void *unused)
2823 {
2824         int count = 0;
2825         bool errexit = false;
2826         int i;
2827         struct task_struct *tsp;
2828         DEFINE_TORTURE_RANDOM(trs);
2829
2830         // Allocate and initialize.
2831         set_user_nice(current, MAX_NICE);
2832         VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of test");
2833
2834         // Each pass through this loop does one read-exit episode.
2835         do {
2836                 if (++count > read_exit_burst) {
2837                         VERBOSE_TOROUT_STRING("rcu_torture_read_exit: End of episode");
2838                         rcu_barrier(); // Wait for task_struct free, avoid OOM.
2839                         for (i = 0; i < read_exit_delay; i++) {
2840                                 schedule_timeout_uninterruptible(HZ);
2841                                 if (READ_ONCE(read_exit_child_stop))
2842                                         break;
2843                         }
2844                         if (!READ_ONCE(read_exit_child_stop))
2845                                 VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of episode");
2846                         count = 0;
2847                 }
2848                 if (READ_ONCE(read_exit_child_stop))
2849                         break;
2850                 // Spawn child.
2851                 tsp = kthread_run(rcu_torture_read_exit_child,
2852                                      &trs, "%s",
2853                                      "rcu_torture_read_exit_child");
2854                 if (IS_ERR(tsp)) {
2855                         TOROUT_ERRSTRING("out of memory");
2856                         errexit = true;
2857                         tsp = NULL;
2858                         break;
2859                 }
2860                 cond_resched();
2861                 kthread_stop(tsp);
2862                 n_read_exits ++;
2863                 stutter_wait("rcu_torture_read_exit");
2864         } while (!errexit && !READ_ONCE(read_exit_child_stop));
2865
2866         // Clean up and exit.
2867         smp_store_release(&read_exit_child_stopped, true); // After reaping.
2868         smp_mb(); // Store before wakeup.
2869         wake_up(&read_exit_wq);
2870         while (!torture_must_stop())
2871                 schedule_timeout_uninterruptible(1);
2872         torture_kthread_stopping("rcu_torture_read_exit");
2873         return 0;
2874 }
2875
2876 static int rcu_torture_read_exit_init(void)
2877 {
2878         if (read_exit_burst <= 0)
2879                 return 0;
2880         init_waitqueue_head(&read_exit_wq);
2881         read_exit_child_stop = false;
2882         read_exit_child_stopped = false;
2883         return torture_create_kthread(rcu_torture_read_exit, NULL,
2884                                       read_exit_task);
2885 }
2886
2887 static void rcu_torture_read_exit_cleanup(void)
2888 {
2889         if (!read_exit_task)
2890                 return;
2891         WRITE_ONCE(read_exit_child_stop, true);
2892         smp_mb(); // Above write before wait.
2893         wait_event(read_exit_wq, smp_load_acquire(&read_exit_child_stopped));
2894         torture_stop_kthread(rcutorture_read_exit, read_exit_task);
2895 }
2896
2897 static enum cpuhp_state rcutor_hp;
2898
2899 static void
2900 rcu_torture_cleanup(void)
2901 {
2902         int firsttime;
2903         int flags = 0;
2904         unsigned long gp_seq = 0;
2905         int i;
2906
2907         if (torture_cleanup_begin()) {
2908                 if (cur_ops->cb_barrier != NULL)
2909                         cur_ops->cb_barrier();
2910                 return;
2911         }
2912         if (!cur_ops) {
2913                 torture_cleanup_end();
2914                 return;
2915         }
2916
2917         if (cur_ops->gp_kthread_dbg)
2918                 cur_ops->gp_kthread_dbg();
2919         rcu_torture_read_exit_cleanup();
2920         rcu_torture_barrier_cleanup();
2921         rcu_torture_fwd_prog_cleanup();
2922         torture_stop_kthread(rcu_torture_stall, stall_task);
2923         torture_stop_kthread(rcu_torture_writer, writer_task);
2924
2925         if (nocb_tasks) {
2926                 for (i = 0; i < nrealnocbers; i++)
2927                         torture_stop_kthread(rcu_nocb_toggle, nocb_tasks[i]);
2928                 kfree(nocb_tasks);
2929                 nocb_tasks = NULL;
2930         }
2931
2932         if (reader_tasks) {
2933                 for (i = 0; i < nrealreaders; i++)
2934                         torture_stop_kthread(rcu_torture_reader,
2935                                              reader_tasks[i]);
2936                 kfree(reader_tasks);
2937                 reader_tasks = NULL;
2938         }
2939         kfree(rcu_torture_reader_mbchk);
2940         rcu_torture_reader_mbchk = NULL;
2941
2942         if (fakewriter_tasks) {
2943                 for (i = 0; i < nfakewriters; i++)
2944                         torture_stop_kthread(rcu_torture_fakewriter,
2945                                              fakewriter_tasks[i]);
2946                 kfree(fakewriter_tasks);
2947                 fakewriter_tasks = NULL;
2948         }
2949
2950         rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
2951         srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
2952         pr_alert("%s:  End-test grace-period state: g%ld f%#x total-gps=%ld\n",
2953                  cur_ops->name, (long)gp_seq, flags,
2954                  rcutorture_seq_diff(gp_seq, start_gp_seq));
2955         torture_stop_kthread(rcu_torture_stats, stats_task);
2956         torture_stop_kthread(rcu_torture_fqs, fqs_task);
2957         if (rcu_torture_can_boost() && rcutor_hp >= 0)
2958                 cpuhp_remove_state(rcutor_hp);
2959
2960         /*
2961          * Wait for all RCU callbacks to fire, then do torture-type-specific
2962          * cleanup operations.
2963          */
2964         if (cur_ops->cb_barrier != NULL)
2965                 cur_ops->cb_barrier();
2966         if (cur_ops->cleanup != NULL)
2967                 cur_ops->cleanup();
2968
2969         rcu_torture_mem_dump_obj();
2970
2971         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
2972
2973         if (err_segs_recorded) {
2974                 pr_alert("Failure/close-call rcutorture reader segments:\n");
2975                 if (rt_read_nsegs == 0)
2976                         pr_alert("\t: No segments recorded!!!\n");
2977                 firsttime = 1;
2978                 for (i = 0; i < rt_read_nsegs; i++) {
2979                         pr_alert("\t%d: %#x ", i, err_segs[i].rt_readstate);
2980                         if (err_segs[i].rt_delay_jiffies != 0) {
2981                                 pr_cont("%s%ldjiffies", firsttime ? "" : "+",
2982                                         err_segs[i].rt_delay_jiffies);
2983                                 firsttime = 0;
2984                         }
2985                         if (err_segs[i].rt_delay_ms != 0) {
2986                                 pr_cont("%s%ldms", firsttime ? "" : "+",
2987                                         err_segs[i].rt_delay_ms);
2988                                 firsttime = 0;
2989                         }
2990                         if (err_segs[i].rt_delay_us != 0) {
2991                                 pr_cont("%s%ldus", firsttime ? "" : "+",
2992                                         err_segs[i].rt_delay_us);
2993                                 firsttime = 0;
2994                         }
2995                         pr_cont("%s\n",
2996                                 err_segs[i].rt_preempted ? "preempted" : "");
2997
2998                 }
2999         }
3000         if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
3001                 rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
3002         else if (torture_onoff_failures())
3003                 rcu_torture_print_module_parms(cur_ops,
3004                                                "End of test: RCU_HOTPLUG");
3005         else
3006                 rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
3007         torture_cleanup_end();
3008 }
3009
3010 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
3011 static void rcu_torture_leak_cb(struct rcu_head *rhp)
3012 {
3013 }
3014
3015 static void rcu_torture_err_cb(struct rcu_head *rhp)
3016 {
3017         /*
3018          * This -might- happen due to race conditions, but is unlikely.
3019          * The scenario that leads to this happening is that the
3020          * first of the pair of duplicate callbacks is queued,
3021          * someone else starts a grace period that includes that
3022          * callback, then the second of the pair must wait for the
3023          * next grace period.  Unlikely, but can happen.  If it
3024          * does happen, the debug-objects subsystem won't have splatted.
3025          */
3026         pr_alert("%s: duplicated callback was invoked.\n", KBUILD_MODNAME);
3027 }
3028 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
3029
3030 /*
3031  * Verify that double-free causes debug-objects to complain, but only
3032  * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.  Otherwise, say that the test
3033  * cannot be carried out.
3034  */
3035 static void rcu_test_debug_objects(void)
3036 {
3037 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
3038         struct rcu_head rh1;
3039         struct rcu_head rh2;
3040         struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
3041
3042         init_rcu_head_on_stack(&rh1);
3043         init_rcu_head_on_stack(&rh2);
3044         pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME);
3045
3046         /* Try to queue the rh2 pair of callbacks for the same grace period. */
3047         preempt_disable(); /* Prevent preemption from interrupting test. */
3048         rcu_read_lock(); /* Make it impossible to finish a grace period. */
3049         call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */
3050         local_irq_disable(); /* Make it harder to start a new grace period. */
3051         call_rcu(&rh2, rcu_torture_leak_cb);
3052         call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
3053         if (rhp) {
3054                 call_rcu(rhp, rcu_torture_leak_cb);
3055                 call_rcu(rhp, rcu_torture_err_cb); /* Another duplicate callback. */
3056         }
3057         local_irq_enable();
3058         rcu_read_unlock();
3059         preempt_enable();
3060
3061         /* Wait for them all to get done so we can safely return. */
3062         rcu_barrier();
3063         pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
3064         destroy_rcu_head_on_stack(&rh1);
3065         destroy_rcu_head_on_stack(&rh2);
3066 #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
3067         pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
3068 #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
3069 }
3070
3071 static void rcutorture_sync(void)
3072 {
3073         static unsigned long n;
3074
3075         if (cur_ops->sync && !(++n & 0xfff))
3076                 cur_ops->sync();
3077 }
3078
3079 static int __init
3080 rcu_torture_init(void)
3081 {
3082         long i;
3083         int cpu;
3084         int firsterr = 0;
3085         int flags = 0;
3086         unsigned long gp_seq = 0;
3087         static struct rcu_torture_ops *torture_ops[] = {
3088                 &rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
3089                 &busted_srcud_ops, &tasks_ops, &tasks_rude_ops,
3090                 &tasks_tracing_ops, &trivial_ops,
3091         };
3092
3093         if (!torture_init_begin(torture_type, verbose))
3094                 return -EBUSY;
3095
3096         /* Process args and tell the world that the torturer is on the job. */
3097         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
3098                 cur_ops = torture_ops[i];
3099                 if (strcmp(torture_type, cur_ops->name) == 0)
3100                         break;
3101         }
3102         if (i == ARRAY_SIZE(torture_ops)) {
3103                 pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
3104                          torture_type);
3105                 pr_alert("rcu-torture types:");
3106                 for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
3107                         pr_cont(" %s", torture_ops[i]->name);
3108                 pr_cont("\n");
3109                 firsterr = -EINVAL;
3110                 cur_ops = NULL;
3111                 goto unwind;
3112         }
3113         if (cur_ops->fqs == NULL && fqs_duration != 0) {
3114                 pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
3115                 fqs_duration = 0;
3116         }
3117         if (cur_ops->init)
3118                 cur_ops->init();
3119
3120         if (nreaders >= 0) {
3121                 nrealreaders = nreaders;
3122         } else {
3123                 nrealreaders = num_online_cpus() - 2 - nreaders;
3124                 if (nrealreaders <= 0)
3125                         nrealreaders = 1;
3126         }
3127         rcu_torture_print_module_parms(cur_ops, "Start of test");
3128         rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
3129         srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
3130         start_gp_seq = gp_seq;
3131         pr_alert("%s:  Start-test grace-period state: g%ld f%#x\n",
3132                  cur_ops->name, (long)gp_seq, flags);
3133
3134         /* Set up the freelist. */
3135
3136         INIT_LIST_HEAD(&rcu_torture_freelist);
3137         for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
3138                 rcu_tortures[i].rtort_mbtest = 0;
3139                 list_add_tail(&rcu_tortures[i].rtort_free,
3140                               &rcu_torture_freelist);
3141         }
3142
3143         /* Initialize the statistics so that each run gets its own numbers. */
3144
3145         rcu_torture_current = NULL;
3146         rcu_torture_current_version = 0;
3147         atomic_set(&n_rcu_torture_alloc, 0);
3148         atomic_set(&n_rcu_torture_alloc_fail, 0);
3149         atomic_set(&n_rcu_torture_free, 0);
3150         atomic_set(&n_rcu_torture_mberror, 0);
3151         atomic_set(&n_rcu_torture_mbchk_fail, 0);
3152         atomic_set(&n_rcu_torture_mbchk_tries, 0);
3153         atomic_set(&n_rcu_torture_error, 0);
3154         n_rcu_torture_barrier_error = 0;
3155         n_rcu_torture_boost_ktrerror = 0;
3156         n_rcu_torture_boost_rterror = 0;
3157         n_rcu_torture_boost_failure = 0;
3158         n_rcu_torture_boosts = 0;
3159         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
3160                 atomic_set(&rcu_torture_wcount[i], 0);
3161         for_each_possible_cpu(cpu) {
3162                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
3163                         per_cpu(rcu_torture_count, cpu)[i] = 0;
3164                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
3165                 }
3166         }
3167         err_segs_recorded = 0;
3168         rt_read_nsegs = 0;
3169
3170         /* Start up the kthreads. */
3171
3172         rcu_torture_write_types();
3173         firsterr = torture_create_kthread(rcu_torture_writer, NULL,
3174                                           writer_task);
3175         if (torture_init_error(firsterr))
3176                 goto unwind;
3177         if (nfakewriters > 0) {
3178                 fakewriter_tasks = kcalloc(nfakewriters,
3179                                            sizeof(fakewriter_tasks[0]),
3180                                            GFP_KERNEL);
3181                 if (fakewriter_tasks == NULL) {
3182                         TOROUT_ERRSTRING("out of memory");
3183                         firsterr = -ENOMEM;
3184                         goto unwind;
3185                 }
3186         }
3187         for (i = 0; i < nfakewriters; i++) {
3188                 firsterr = torture_create_kthread(rcu_torture_fakewriter,
3189                                                   NULL, fakewriter_tasks[i]);
3190                 if (torture_init_error(firsterr))
3191                         goto unwind;
3192         }
3193         reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
3194                                GFP_KERNEL);
3195         rcu_torture_reader_mbchk = kcalloc(nrealreaders, sizeof(*rcu_torture_reader_mbchk),
3196                                            GFP_KERNEL);
3197         if (!reader_tasks || !rcu_torture_reader_mbchk) {
3198                 TOROUT_ERRSTRING("out of memory");
3199                 firsterr = -ENOMEM;
3200                 goto unwind;
3201         }
3202         for (i = 0; i < nrealreaders; i++) {
3203                 rcu_torture_reader_mbchk[i].rtc_chkrdr = -1;
3204                 firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
3205                                                   reader_tasks[i]);
3206                 if (torture_init_error(firsterr))
3207                         goto unwind;
3208         }
3209         nrealnocbers = nocbs_nthreads;
3210         if (WARN_ON(nrealnocbers < 0))
3211                 nrealnocbers = 1;
3212         if (WARN_ON(nocbs_toggle < 0))
3213                 nocbs_toggle = HZ;
3214         if (nrealnocbers > 0) {
3215                 nocb_tasks = kcalloc(nrealnocbers, sizeof(nocb_tasks[0]), GFP_KERNEL);
3216                 if (nocb_tasks == NULL) {
3217                         TOROUT_ERRSTRING("out of memory");
3218                         firsterr = -ENOMEM;
3219                         goto unwind;
3220                 }
3221         } else {
3222                 nocb_tasks = NULL;
3223         }
3224         for (i = 0; i < nrealnocbers; i++) {
3225                 firsterr = torture_create_kthread(rcu_nocb_toggle, NULL, nocb_tasks[i]);
3226                 if (torture_init_error(firsterr))
3227                         goto unwind;
3228         }
3229         if (stat_interval > 0) {
3230                 firsterr = torture_create_kthread(rcu_torture_stats, NULL,
3231                                                   stats_task);
3232                 if (torture_init_error(firsterr))
3233                         goto unwind;
3234         }
3235         if (test_no_idle_hz && shuffle_interval > 0) {
3236                 firsterr = torture_shuffle_init(shuffle_interval * HZ);
3237                 if (torture_init_error(firsterr))
3238                         goto unwind;
3239         }
3240         if (stutter < 0)
3241                 stutter = 0;
3242         if (stutter) {
3243                 int t;
3244
3245                 t = cur_ops->stall_dur ? cur_ops->stall_dur() : stutter * HZ;
3246                 firsterr = torture_stutter_init(stutter * HZ, t);
3247                 if (torture_init_error(firsterr))
3248                         goto unwind;
3249         }
3250         if (fqs_duration < 0)
3251                 fqs_duration = 0;
3252         if (fqs_duration) {
3253                 /* Create the fqs thread */
3254                 firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
3255                                                   fqs_task);
3256                 if (torture_init_error(firsterr))
3257                         goto unwind;
3258         }
3259         if (test_boost_interval < 1)
3260                 test_boost_interval = 1;
3261         if (test_boost_duration < 2)
3262                 test_boost_duration = 2;
3263         if (rcu_torture_can_boost()) {
3264
3265                 boost_starttime = jiffies + test_boost_interval * HZ;
3266
3267                 firsterr = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "RCU_TORTURE",
3268                                              rcutorture_booster_init,
3269                                              rcutorture_booster_cleanup);
3270                 rcutor_hp = firsterr;
3271                 if (torture_init_error(firsterr))
3272                         goto unwind;
3273
3274                 // Testing RCU priority boosting requires rcutorture do
3275                 // some serious abuse.  Counter this by running ksoftirqd
3276                 // at higher priority.
3277                 if (IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) {
3278                         for_each_online_cpu(cpu) {
3279                                 struct sched_param sp;
3280                                 struct task_struct *t;
3281
3282                                 t = per_cpu(ksoftirqd, cpu);
3283                                 WARN_ON_ONCE(!t);
3284                                 sp.sched_priority = 2;
3285                                 sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
3286                         }
3287                 }
3288         }
3289         shutdown_jiffies = jiffies + shutdown_secs * HZ;
3290         firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
3291         if (torture_init_error(firsterr))
3292                 goto unwind;
3293         firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval,
3294                                       rcutorture_sync);
3295         if (torture_init_error(firsterr))
3296                 goto unwind;
3297         firsterr = rcu_torture_stall_init();
3298         if (torture_init_error(firsterr))
3299                 goto unwind;
3300         firsterr = rcu_torture_fwd_prog_init();
3301         if (torture_init_error(firsterr))
3302                 goto unwind;
3303         firsterr = rcu_torture_barrier_init();
3304         if (torture_init_error(firsterr))
3305                 goto unwind;
3306         firsterr = rcu_torture_read_exit_init();
3307         if (torture_init_error(firsterr))
3308                 goto unwind;
3309         if (object_debug)
3310                 rcu_test_debug_objects();
3311         torture_init_end();
3312         return 0;
3313
3314 unwind:
3315         torture_init_end();
3316         rcu_torture_cleanup();
3317         if (shutdown_secs) {
3318                 WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
3319                 kernel_power_off();
3320         }
3321         return firsterr;
3322 }
3323
3324 module_init(rcu_torture_init);
3325 module_exit(rcu_torture_cleanup);