Quelle  rcutorture.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0+
/*
 * Read-Copy Update module-based torture test facility
 *
 * Copyright (C) IBM Corporation, 2005, 2006
 *
 * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 *   Josh Triplett <josh@joshtriplett.org>
 *
 * See also:  Documentation/RCU/torture.rst
 */

#define pr_fmt(fmt) fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/rcupdate_wait.h>
#include <linux/rcu_notifier.h>
#include <linux/interrupt.h>
#include <linux/sched/signal.h>
#include <uapi/linux/sched/types.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/freezer.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/stat.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/trace_clock.h>
#include <asm/byteorder.h>
#include <linux/torture.h>
#include <linux/vmalloc.h>
#include <linux/sched/debug.h>
#include <linux/sched/sysctl.h>
#include <linux/oom.h>
#include <linux/tick.h>
#include <linux/rcupdate_trace.h>
#include <linux/nmi.h>

#include "rcu.h"

MODULE_DESCRIPTION("Read-Copy Update module-based torture test facility");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney and Josh Triplett ");

// Bits for ->extendables field, extendables param, and related definitions.
#define RCUTORTURE_RDR_SHIFT_1 8 // Put SRCU index in upper bits.
#define RCUTORTURE_RDR_MASK_1 (0xff << RCUTORTURE_RDR_SHIFT_1)
#define RCUTORTURE_RDR_SHIFT_2 16 // Put SRCU index in upper bits.
#define RCUTORTURE_RDR_MASK_2 (0xff << RCUTORTURE_RDR_SHIFT_2)
#define RCUTORTURE_RDR_BH 0x01 // Extend readers by disabling bh.
#define RCUTORTURE_RDR_IRQ 0x02 //  ... disabling interrupts.
#define RCUTORTURE_RDR_PREEMPT 0x04 //  ... disabling preemption.
#define RCUTORTURE_RDR_RBH 0x08 //  ... rcu_read_lock_bh().
#define RCUTORTURE_RDR_SCHED 0x10 //  ... rcu_read_lock_sched().
#define RCUTORTURE_RDR_RCU_1 0x20 //  ... entering another RCU reader.
#define RCUTORTURE_RDR_RCU_2 0x40 //  ... entering another RCU reader.
#define RCUTORTURE_RDR_UPDOWN 0x80 //  ... up-read from task, down-read from timer.
     // Note: Manual start, automatic end.
#define RCUTORTURE_RDR_NBITS 8 // Number of bits defined above.
#define RCUTORTURE_MAX_EXTEND \
 (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
  RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)  // Intentionally omit RCUTORTURE_RDR_UPDOWN.
#define RCUTORTURE_RDR_ALLBITS \
 (RCUTORTURE_MAX_EXTEND | RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2 | \
  RCUTORTURE_RDR_MASK_1 | RCUTORTURE_RDR_MASK_2)
#define RCUTORTURE_RDR_MAX_LOOPS 0x7 /* Maximum reader extensions. */
     /* Must be power of two minus one. */
#define RCUTORTURE_RDR_MAX_SEGS (RCUTORTURE_RDR_MAX_LOOPS + 3)

torture_param(int, extendables, RCUTORTURE_MAX_EXTEND,
       "Extend readers by disabling bh (1), irqs (2), or preempt (4)");
torture_param(int, fqs_duration, 0, "Duration of fqs bursts (us), 0 to disable");
torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
torture_param(int, fwd_progress, 1, "Number of grace-period forward progress tasks (0 to disable)");
torture_param(int, fwd_progress_div, 4, "Fraction of CPU stall to wait");
torture_param(int, fwd_progress_holdoff, 60, "Time between forward-progress tests (s)");
torture_param(bool, fwd_progress_need_resched, 1, "Hide cond_resched() behind need_resched()");
torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
torture_param(bool, gp_cond_exp, false, "Use conditional/async expedited GP wait primitives");
torture_param(bool, gp_cond_full, false, "Use conditional/async full-state GP wait primitives");
torture_param(bool, gp_cond_exp_full, false,
      "Use conditional/async full-stateexpedited GP wait primitives");
torture_param(int, gp_cond_wi, 16 * USEC_PER_SEC / HZ,
     "Wait interval for normal conditional grace periods, us (default 16 jiffies)");
torture_param(int, gp_cond_wi_exp, 128,
     "Wait interval for expedited conditional grace periods, us (default 128 us)");
torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
torture_param(bool, gp_normal, false, "Use normal (non-expedited) GP wait primitives");
torture_param(bool, gp_poll, false, "Use polling GP wait primitives");
torture_param(bool, gp_poll_exp, false, "Use polling expedited GP wait primitives");
torture_param(bool, gp_poll_full, false, "Use polling full-state GP wait primitives");
torture_param(bool, gp_poll_exp_full, false, "Use polling full-state expedited GP wait primitives");
torture_param(int, gp_poll_wi, 16 * USEC_PER_SEC / HZ,
     "Wait interval for normal polled grace periods, us (default 16 jiffies)");
torture_param(int, gp_poll_wi_exp, 128,
     "Wait interval for expedited polled grace periods, us (default 128 us)");
torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
torture_param(int, leakpointer, 0, "Leak pointer dereferences from readers");
torture_param(int, n_barrier_cbs, 0, "# of callbacks/kthreads for barrier testing");
torture_param(int, n_up_down, 32, "# of concurrent up/down hrtimer-based RCU readers");
torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
torture_param(int, nreaders, -1, "Number of RCU reader threads");
torture_param(int, object_debug, 0, "Enable debug-object double call_rcu() testing");
torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (jiffies), 0=disable");
torture_param(bool, gpwrap_lag, true, "Enable grace-period wrap lag testing");
torture_param(int, gpwrap_lag_gps, 8, "Value to set for set_gpwrap_lag during an active testing period.");
torture_param(int, gpwrap_lag_cycle_mins, 30, "Total cycle duration for gpwrap lag testing (in minutes)");
torture_param(int, gpwrap_lag_active_mins, 5, "Duration for which gpwrap lag is active within each cycle (in minutes)");
torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disable");
torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
torture_param(int, preempt_duration, 0, "Preemption duration (ms), zero to disable");
torture_param(int, preempt_interval, MSEC_PER_SEC, "Interval between preemptions (ms)");
torture_param(int, read_exit_delay, 13, "Delay between read-then-exit episodes (s)");
torture_param(int, read_exit_burst, 16, "# of read-then-exit bursts per episode, zero to disable");
torture_param(int, reader_flavor, SRCU_READ_FLAVOR_NORMAL, "Reader flavors to use, one per bit.");
torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
torture_param(int, stall_cpu_holdoff, 10, "Time to wait before starting stall (s).");
torture_param(bool, stall_no_softlockup, false, "Avoid softlockup warning during cpu stall.");
torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
torture_param(int, stall_cpu_block, 0, "Sleep while stalling.");
torture_param(int, stall_cpu_repeat, 0, "Number of additional stalls after the first one.");
torture_param(int, stall_gp_kthread, 0, "Grace-period kthread stall duration (s).");
torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s");
torture_param(int, stutter, 5, "Number of seconds to run/halt test");
torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
torture_param(int, test_boost_duration, 4, "Duration of each boost test, seconds.");
torture_param(int, test_boost_holdoff, 0, "Holdoff time from rcutorture start, seconds.");
torture_param(int, test_boost_interval, 7, "Interval between boost tests, seconds.");
torture_param(int, test_nmis, 0, "End-test NMI tests, 0 to disable.");
torture_param(bool, test_no_idle_hz, true, "Test support for tickless idle CPUs");
torture_param(int, test_srcu_lockdep, 0, "Test specified SRCU deadlock scenario.");
torture_param(int, verbose, 1, "Enable verbose debugging printk()s");

static char *torture_type = "rcu";
module_param(torture_type, charp, 0444);
MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");

static int nrealnocbers;
static int nrealreaders;
static int nrealfakewriters;
static struct task_struct *writer_task;
static struct task_struct **fakewriter_tasks;
static struct task_struct **reader_tasks;
static struct task_struct *updown_task;
static struct task_struct **nocb_tasks;
static struct task_struct *stats_task;
static struct task_struct *fqs_task;
static struct task_struct *boost_tasks[NR_CPUS];
static struct task_struct *stall_task;
static struct task_struct **fwd_prog_tasks;
static struct task_struct **barrier_cbs_tasks;
static struct task_struct *barrier_task;
static struct task_struct *read_exit_task;
static struct task_struct *preempt_task;

#define RCU_TORTURE_PIPE_LEN 10

// Mailbox-like structure to check RCU global memory ordering.
struct rcu_torture_reader_check {
 unsigned long rtc_myloops;
 int rtc_chkrdr;
 unsigned long rtc_chkloops;
 int rtc_ready;
 struct rcu_torture_reader_check *rtc_assigner;
} ____cacheline_internodealigned_in_smp;

// Update-side data structure used to check RCU readers.
struct rcu_torture {
 struct rcu_head rtort_rcu;
 int rtort_pipe_count;
 struct list_head rtort_free;
 int rtort_mbtest;
 struct rcu_torture_reader_check *rtort_chkp;
};

static LIST_HEAD(rcu_torture_freelist);
static struct rcu_torture __rcu *rcu_torture_current;
static unsigned long rcu_torture_current_version;
static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
static DEFINE_SPINLOCK(rcu_torture_lock);
static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
static struct rcu_torture_reader_check *rcu_torture_reader_mbchk;
static atomic_t n_rcu_torture_alloc;
static atomic_t n_rcu_torture_alloc_fail;
static atomic_t n_rcu_torture_free;
static atomic_t n_rcu_torture_mberror;
static atomic_t n_rcu_torture_mbchk_fail;
static atomic_t n_rcu_torture_mbchk_tries;
static atomic_t n_rcu_torture_error;
static long n_rcu_torture_barrier_error;
static long n_rcu_torture_boost_ktrerror;
static long n_rcu_torture_boost_failure;
static long n_rcu_torture_boosts;
static atomic_long_t n_rcu_torture_timers;
static long n_barrier_attempts;
static long n_barrier_successes; /* did rcu_barrier test succeed? */
static unsigned long n_read_exits;
static struct list_head rcu_torture_removed;
static unsigned long shutdown_jiffies;
static unsigned long start_gp_seq;
static atomic_long_t n_nocb_offload;
static atomic_long_t n_nocb_deoffload;

static int rcu_torture_writer_state;
#define RTWS_FIXED_DELAY 0
#define RTWS_DELAY  1
#define RTWS_REPLACE  2
#define RTWS_DEF_FREE  3
#define RTWS_EXP_SYNC  4
#define RTWS_COND_GET  5
#define RTWS_COND_GET_FULL 6
#define RTWS_COND_GET_EXP 7
#define RTWS_COND_GET_EXP_FULL 8
#define RTWS_COND_SYNC  9
#define RTWS_COND_SYNC_FULL 10
#define RTWS_COND_SYNC_EXP 11
#define RTWS_COND_SYNC_EXP_FULL 12
#define RTWS_POLL_GET  13
#define RTWS_POLL_GET_FULL 14
#define RTWS_POLL_GET_EXP 15
#define RTWS_POLL_GET_EXP_FULL 16
#define RTWS_POLL_WAIT  17
#define RTWS_POLL_WAIT_FULL 18
#define RTWS_POLL_WAIT_EXP 19
#define RTWS_POLL_WAIT_EXP_FULL 20
#define RTWS_SYNC  21
#define RTWS_STUTTER  22
#define RTWS_STOPPING  23
static const char * const rcu_torture_writer_state_names[] = {
 "RTWS_FIXED_DELAY",
 "RTWS_DELAY",
 "RTWS_REPLACE",
 "RTWS_DEF_FREE",
 "RTWS_EXP_SYNC",
 "RTWS_COND_GET",
 "RTWS_COND_GET_FULL",
 "RTWS_COND_GET_EXP",
 "RTWS_COND_GET_EXP_FULL",
 "RTWS_COND_SYNC",
 "RTWS_COND_SYNC_FULL",
 "RTWS_COND_SYNC_EXP",
 "RTWS_COND_SYNC_EXP_FULL",
 "RTWS_POLL_GET",
 "RTWS_POLL_GET_FULL",
 "RTWS_POLL_GET_EXP",
 "RTWS_POLL_GET_EXP_FULL",
 "RTWS_POLL_WAIT",
 "RTWS_POLL_WAIT_FULL",
 "RTWS_POLL_WAIT_EXP",
 "RTWS_POLL_WAIT_EXP_FULL",
 "RTWS_SYNC",
 "RTWS_STUTTER",
 "RTWS_STOPPING",
};

/* Record reader segment types and duration for first failing read. */
struct rt_read_seg {
 int rt_readstate;
 unsigned long rt_delay_jiffies;
 unsigned long rt_delay_ms;
 unsigned long rt_delay_us;
 bool rt_preempted;
 int rt_cpu;
 int rt_end_cpu;
 unsigned long long rt_gp_seq;
 unsigned long long rt_gp_seq_end;
 u64 rt_ts;
};
static int err_segs_recorded;
static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
static int rt_read_nsegs;
static int rt_read_preempted;

static const char *rcu_torture_writer_state_getname(void)
{
 unsigned int i = READ_ONCE(rcu_torture_writer_state);

 if (i >= ARRAY_SIZE(rcu_torture_writer_state_names))
  return "???";
 return rcu_torture_writer_state_names[i];
}

#ifdef CONFIG_RCU_TRACE
static u64 notrace rcu_trace_clock_local(void)
{
 u64 ts = trace_clock_local();

 (void)do_div(ts, NSEC_PER_USEC);
 return ts;
}
#else /* #ifdef CONFIG_RCU_TRACE */
static u64 notrace rcu_trace_clock_local(void)
{
 return 0ULL;
}
#endif /* #else #ifdef CONFIG_RCU_TRACE */

/*
 * Stop aggressive CPU-hog tests a bit before the end of the test in order
 * to avoid interfering with test shutdown.
 */
static bool shutdown_time_arrived(void)
{
 return shutdown_secs && time_after(jiffies, shutdown_jiffies - 30 * HZ);
}

static unsigned long boost_starttime; /* jiffies of next boost test start. */
static DEFINE_MUTEX(boost_mutex); /* protect setting boost_starttime */
     /*  and boost task create/destroy. */
static atomic_t barrier_cbs_count; /* Barrier callbacks registered. */
static bool barrier_phase;  /* Test phase. */
static atomic_t barrier_cbs_invoked; /* Barrier callbacks invoked. */
static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);

static atomic_t rcu_fwd_cb_nodelay; /* Short rcu_torture_delay() delays. */

/*
 * Allocate an element from the rcu_tortures pool.
 */
static struct rcu_torture *
rcu_torture_alloc(void)
{
 struct list_head *p;

 spin_lock_bh(&rcu_torture_lock);
 if (list_empty(&rcu_torture_freelist)) {
  atomic_inc(&n_rcu_torture_alloc_fail);
  spin_unlock_bh(&rcu_torture_lock);
  return NULL;
 }
 atomic_inc(&n_rcu_torture_alloc);
 p = rcu_torture_freelist.next;
 list_del_init(p);
 spin_unlock_bh(&rcu_torture_lock);
 return container_of(p, struct rcu_torture, rtort_free);
}

/*
 * Free an element to the rcu_tortures pool.
 */
static void
rcu_torture_free(struct rcu_torture *p)
{
 atomic_inc(&n_rcu_torture_free);
 spin_lock_bh(&rcu_torture_lock);
 list_add_tail(&p->rtort_free, &rcu_torture_freelist);
 spin_unlock_bh(&rcu_torture_lock);
}

/*
 * Operations vector for selecting different types of tests.
 */

struct rcu_torture_ops {
 int ttype;
 void (*init)(void);
 void (*cleanup)(void);
 int (*readlock)(void);
 void (*read_delay)(struct torture_random_state *rrsp,
      struct rt_read_seg *rtrsp);
 void (*readunlock)(int idx);
 int (*readlock_held)(void);   // lockdep.
 int (*readlock_nesting)(void); // actual nesting, if available, -1 if not.
 int (*down_read)(void);
 void (*up_read)(int idx);
 unsigned long (*get_gp_seq)(void);
 unsigned long (*gp_diff)(unsigned long new, unsigned long old);
 void (*deferred_free)(struct rcu_torture *p);
 void (*sync)(void);
 void (*exp_sync)(void);
 unsigned long (*get_gp_state_exp)(void);
 unsigned long (*start_gp_poll_exp)(void);
 void (*start_gp_poll_exp_full)(struct rcu_gp_oldstate *rgosp);
 bool (*poll_gp_state_exp)(unsigned long oldstate);
 void (*cond_sync_exp)(unsigned long oldstate);
 void (*cond_sync_exp_full)(struct rcu_gp_oldstate *rgosp);
 unsigned long (*get_comp_state)(void);
 void (*get_comp_state_full)(struct rcu_gp_oldstate *rgosp);
 bool (*same_gp_state)(unsigned long oldstate1, unsigned long oldstate2);
 bool (*same_gp_state_full)(struct rcu_gp_oldstate *rgosp1, struct rcu_gp_oldstate *rgosp2);
 unsigned long (*get_gp_state)(void);
 void (*get_gp_state_full)(struct rcu_gp_oldstate *rgosp);
 unsigned long (*start_gp_poll)(void);
 void (*start_gp_poll_full)(struct rcu_gp_oldstate *rgosp);
 bool (*poll_gp_state)(unsigned long oldstate);
 bool (*poll_gp_state_full)(struct rcu_gp_oldstate *rgosp);
 bool (*poll_need_2gp)(bool poll, bool poll_full);
 void (*cond_sync)(unsigned long oldstate);
 void (*cond_sync_full)(struct rcu_gp_oldstate *rgosp);
 int poll_active;
 int poll_active_full;
 call_rcu_func_t call;
 void (*cb_barrier)(void);
 void (*fqs)(void);
 void (*stats)(void);
 void (*gp_kthread_dbg)(void);
 bool (*check_boost_failed)(unsigned long gp_state, int *cpup);
 int (*stall_dur)(void);
 void (*get_gp_data)(int *flags, unsigned long *gp_seq);
 void (*gp_slow_register)(atomic_t *rgssp);
 void (*gp_slow_unregister)(atomic_t *rgssp);
 bool (*reader_blocked)(void);
 unsigned long long (*gather_gp_seqs)(void);
 void (*format_gp_seqs)(unsigned long long seqs, char *cp, size_t len);
 void (*set_gpwrap_lag)(unsigned long lag);
 int (*get_gpwrap_count)(int cpu);
 long cbflood_max;
 int irq_capable;
 int can_boost;
 int extendables;
 int slow_gps;
 int no_pi_lock;
 int debug_objects;
 int start_poll_irqsoff;
 int have_up_down;
 const char *name;
};

static struct rcu_torture_ops *cur_ops;

/*
 * Definitions for rcu torture testing.
 */

static int torture_readlock_not_held(void)
{
 return rcu_read_lock_bh_held() || rcu_read_lock_sched_held();
}

static int rcu_torture_read_lock(void)
{
 rcu_read_lock();
 return 0;
}

static void
rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
{
 unsigned long started;
 unsigned long completed;
 const unsigned long shortdelay_us = 200;
 unsigned long longdelay_ms = 300;
 unsigned long long ts;

 /* We want a short delay sometimes to make a reader delay the grace
 * period, and we want a long delay occasionally to trigger
 * force_quiescent_state. */

 if (!atomic_read(&rcu_fwd_cb_nodelay) &&
     !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
  started = cur_ops->get_gp_seq();
  ts = rcu_trace_clock_local();
  if ((preempt_count() & HARDIRQ_MASK) || softirq_count())
   longdelay_ms = 5; /* Avoid triggering BH limits. */
  mdelay(longdelay_ms);
  rtrsp->rt_delay_ms = longdelay_ms;
  completed = cur_ops->get_gp_seq();
  do_trace_rcu_torture_read(cur_ops->name, NULL, ts,
       started, completed);
 }
 if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) {
  udelay(shortdelay_us);
  rtrsp->rt_delay_us = shortdelay_us;
 }
 if (!preempt_count() &&
     !(torture_random(rrsp) % (nrealreaders * 500)))
  torture_preempt_schedule();  /* QS only if preemptible. */
}

static void rcu_torture_read_unlock(int idx)
{
 rcu_read_unlock();
}

static int rcu_torture_readlock_nesting(void)
{
 if (IS_ENABLED(CONFIG_PREEMPT_RCU))
  return rcu_preempt_depth();
 if (IS_ENABLED(CONFIG_PREEMPT_COUNT))
  return (preempt_count() & PREEMPT_MASK);
 return -1;
}

/*
 * Update callback in the pipe.  This should be invoked after a grace period.
 */
static bool
rcu_torture_pipe_update_one(struct rcu_torture *rp)
{
 int i;
 struct rcu_torture_reader_check *rtrcp = READ_ONCE(rp->rtort_chkp);

 if (rtrcp) {
  WRITE_ONCE(rp->rtort_chkp, NULL);
  smp_store_release(&rtrcp->rtc_ready, 1); // Pair with smp_load_acquire().
 }
 i = rp->rtort_pipe_count;
 if (i > RCU_TORTURE_PIPE_LEN)
  i = RCU_TORTURE_PIPE_LEN;
 atomic_inc(&rcu_torture_wcount[i]);
 WRITE_ONCE(rp->rtort_pipe_count, i + 1);
 ASSERT_EXCLUSIVE_WRITER(rp->rtort_pipe_count);
 if (i + 1 >= RCU_TORTURE_PIPE_LEN) {
  rp->rtort_mbtest = 0;
  return true;
 }
 return false;
}

/*
 * Update all callbacks in the pipe.  Suitable for synchronous grace-period
 * primitives.
 */
static void
rcu_torture_pipe_update(struct rcu_torture *old_rp)
{
 struct rcu_torture *rp;
 struct rcu_torture *rp1;

 if (old_rp)
  list_add(&old_rp->rtort_free, &rcu_torture_removed);
 list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
  if (rcu_torture_pipe_update_one(rp)) {
   list_del(&rp->rtort_free);
   rcu_torture_free(rp);
  }
 }
}

static void
rcu_torture_cb(struct rcu_head *p)
{
 struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);

 if (torture_must_stop_irq()) {
  /* Test is ending, just drop callbacks on the floor. */
  /* The next initialization will pick up the pieces. */
  return;
 }
 if (rcu_torture_pipe_update_one(rp))
  rcu_torture_free(rp);
 else
  cur_ops->deferred_free(rp);
}

static unsigned long rcu_no_completed(void)
{
 return 0;
}

static void rcu_torture_deferred_free(struct rcu_torture *p)
{
 call_rcu_hurry(&p->rtort_rcu, rcu_torture_cb);
}

static void rcu_sync_torture_init(void)
{
 INIT_LIST_HEAD(&rcu_torture_removed);
}

static bool rcu_poll_need_2gp(bool poll, bool poll_full)
{
 return poll;
}

static struct rcu_torture_ops rcu_ops = {
 .ttype   = RCU_FLAVOR,
 .init   = rcu_sync_torture_init,
 .readlock  = rcu_torture_read_lock,
 .read_delay  = rcu_read_delay,
 .readunlock  = rcu_torture_read_unlock,
 .readlock_held  = torture_readlock_not_held,
 .readlock_nesting = rcu_torture_readlock_nesting,
 .get_gp_seq  = rcu_get_gp_seq,
 .gp_diff  = rcu_seq_diff,
 .deferred_free  = rcu_torture_deferred_free,
 .sync   = synchronize_rcu,
 .exp_sync  = synchronize_rcu_expedited,
 .same_gp_state  = same_state_synchronize_rcu,
 .same_gp_state_full = same_state_synchronize_rcu_full,
 .get_comp_state  = get_completed_synchronize_rcu,
 .get_comp_state_full = get_completed_synchronize_rcu_full,
 .get_gp_state  = get_state_synchronize_rcu,
 .get_gp_state_full = get_state_synchronize_rcu_full,
 .start_gp_poll  = start_poll_synchronize_rcu,
 .start_gp_poll_full = start_poll_synchronize_rcu_full,
 .poll_gp_state  = poll_state_synchronize_rcu,
 .poll_gp_state_full = poll_state_synchronize_rcu_full,
 .poll_need_2gp  = rcu_poll_need_2gp,
 .cond_sync  = cond_synchronize_rcu,
 .cond_sync_full  = cond_synchronize_rcu_full,
 .poll_active  = NUM_ACTIVE_RCU_POLL_OLDSTATE,
 .poll_active_full = NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE,
 .get_gp_state_exp = get_state_synchronize_rcu,
 .start_gp_poll_exp = start_poll_synchronize_rcu_expedited,
 .start_gp_poll_exp_full = start_poll_synchronize_rcu_expedited_full,
 .poll_gp_state_exp = poll_state_synchronize_rcu,
 .cond_sync_exp  = cond_synchronize_rcu_expedited,
 .cond_sync_exp_full = cond_synchronize_rcu_expedited_full,
 .call   = call_rcu_hurry,
 .cb_barrier  = rcu_barrier,
 .fqs   = rcu_force_quiescent_state,
 .gp_kthread_dbg  = show_rcu_gp_kthreads,
 .check_boost_failed = rcu_check_boost_fail,
 .stall_dur  = rcu_jiffies_till_stall_check,
 .get_gp_data  = rcutorture_get_gp_data,
 .gp_slow_register = rcu_gp_slow_register,
 .gp_slow_unregister = rcu_gp_slow_unregister,
 .reader_blocked  = IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_CPU)
      ? has_rcu_reader_blocked
      : NULL,
 .gather_gp_seqs  = rcutorture_gather_gp_seqs,
 .format_gp_seqs  = rcutorture_format_gp_seqs,
 .set_gpwrap_lag  = rcu_set_gpwrap_lag,
 .get_gpwrap_count = rcu_get_gpwrap_count,
 .irq_capable  = 1,
 .can_boost  = IS_ENABLED(CONFIG_RCU_BOOST),
 .extendables  = RCUTORTURE_MAX_EXTEND,
 .debug_objects  = 1,
 .start_poll_irqsoff = 1,
 .name   = "rcu"
};

/*
 * Don't even think about trying any of these in real life!!!
 * The names includes "busted", and they really means it!
 * The only purpose of these functions is to provide a buggy RCU
 * implementation to make sure that rcutorture correctly emits
 * buggy-RCU error messages.
 */
static void rcu_busted_torture_deferred_free(struct rcu_torture *p)
{
 /* This is a deliberate bug for testing purposes only! */
 rcu_torture_cb(&p->rtort_rcu);
}

static void synchronize_rcu_busted(void)
{
 /* This is a deliberate bug for testing purposes only! */
}

static void
call_rcu_busted(struct rcu_head *head, rcu_callback_t func)
{
 /* This is a deliberate bug for testing purposes only! */
 func(head);
}

static struct rcu_torture_ops rcu_busted_ops = {
 .ttype  = INVALID_RCU_FLAVOR,
 .init  = rcu_sync_torture_init,
 .readlock = rcu_torture_read_lock,
 .read_delay = rcu_read_delay,  /* just reuse rcu's version. */
 .readunlock = rcu_torture_read_unlock,
 .readlock_held = torture_readlock_not_held,
 .get_gp_seq = rcu_no_completed,
 .deferred_free = rcu_busted_torture_deferred_free,
 .sync  = synchronize_rcu_busted,
 .exp_sync = synchronize_rcu_busted,
 .call  = call_rcu_busted,
 .gather_gp_seqs = rcutorture_gather_gp_seqs,
 .format_gp_seqs = rcutorture_format_gp_seqs,
 .irq_capable = 1,
 .extendables = RCUTORTURE_MAX_EXTEND,
 .name  = "busted"
};

/*
 * Definitions for srcu torture testing.
 */

DEFINE_STATIC_SRCU(srcu_ctl);
static struct srcu_struct srcu_ctld;
static struct srcu_struct *srcu_ctlp = &srcu_ctl;
static struct rcu_torture_ops srcud_ops;

static void srcu_get_gp_data(int *flags, unsigned long *gp_seq)
{
 srcutorture_get_gp_data(srcu_ctlp, flags, gp_seq);
}

static int srcu_torture_read_lock(void)
{
 int idx;
 struct srcu_ctr __percpu *scp;
 int ret = 0;

 WARN_ON_ONCE(reader_flavor & ~SRCU_READ_FLAVOR_ALL);

 if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL)) {
  idx = srcu_read_lock(srcu_ctlp);
  WARN_ON_ONCE(idx & ~0x1);
  ret += idx;
 }
 if (reader_flavor & SRCU_READ_FLAVOR_NMI) {
  idx = srcu_read_lock_nmisafe(srcu_ctlp);
  WARN_ON_ONCE(idx & ~0x1);
  ret += idx << 1;
 }
 if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
  scp = srcu_read_lock_fast(srcu_ctlp);
  idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
  WARN_ON_ONCE(idx & ~0x1);
  ret += idx << 3;
 }
 return ret;
}

static void
srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
{
 long delay;
 const long uspertick = 1000000 / HZ;
 const long longdelay = 10;

 /* We want there to be long-running readers, but not all the time. */

 delay = torture_random(rrsp) %
  (nrealreaders * 2 * longdelay * uspertick);
 if (!delay && in_task()) {
  schedule_timeout_interruptible(longdelay);
  rtrsp->rt_delay_jiffies = longdelay;
 } else {
  rcu_read_delay(rrsp, rtrsp);
 }
}

static void srcu_torture_read_unlock(int idx)
{
 WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
 if (reader_flavor & SRCU_READ_FLAVOR_FAST)
  srcu_read_unlock_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
 if (reader_flavor & SRCU_READ_FLAVOR_NMI)
  srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1);
 if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL))
  srcu_read_unlock(srcu_ctlp, idx & 0x1);
}

static int torture_srcu_read_lock_held(void)
{
 return srcu_read_lock_held(srcu_ctlp);
}

static bool srcu_torture_have_up_down(void)
{
 int rf = reader_flavor;

 if (!rf)
  rf = SRCU_READ_FLAVOR_NORMAL;
 return !!(cur_ops->have_up_down & rf);
}

static int srcu_torture_down_read(void)
{
 int idx;
 struct srcu_ctr __percpu *scp;

 WARN_ON_ONCE(reader_flavor & ~SRCU_READ_FLAVOR_ALL);
 WARN_ON_ONCE(reader_flavor & (reader_flavor - 1));

 if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL)) {
  idx = srcu_down_read(srcu_ctlp);
  WARN_ON_ONCE(idx & ~0x1);
  return idx;
 }
 if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
  scp = srcu_down_read_fast(srcu_ctlp);
  idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
  WARN_ON_ONCE(idx & ~0x1);
  return idx << 3;
 }
 WARN_ON_ONCE(1);
 return 0;
}

static void srcu_torture_up_read(int idx)
{
 WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
 if (reader_flavor & SRCU_READ_FLAVOR_FAST)
  srcu_up_read_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
 else if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) ||
   !(reader_flavor & SRCU_READ_FLAVOR_ALL))
  srcu_up_read(srcu_ctlp, idx & 0x1);
 else
  WARN_ON_ONCE(1);
}

static unsigned long srcu_torture_completed(void)
{
 return srcu_batches_completed(srcu_ctlp);
}

static void srcu_torture_deferred_free(struct rcu_torture *rp)
{
 call_srcu(srcu_ctlp, &rp->rtort_rcu, rcu_torture_cb);
}

static void srcu_torture_synchronize(void)
{
 synchronize_srcu(srcu_ctlp);
}

static unsigned long srcu_torture_get_gp_state(void)
{
 return get_state_synchronize_srcu(srcu_ctlp);
}

static unsigned long srcu_torture_start_gp_poll(void)
{
 return start_poll_synchronize_srcu(srcu_ctlp);
}

static bool srcu_torture_poll_gp_state(unsigned long oldstate)
{
 return poll_state_synchronize_srcu(srcu_ctlp, oldstate);
}

static void srcu_torture_call(struct rcu_head *head,
         rcu_callback_t func)
{
 call_srcu(srcu_ctlp, head, func);
}

static void srcu_torture_barrier(void)
{
 srcu_barrier(srcu_ctlp);
}

static void srcu_torture_stats(void)
{
 srcu_torture_stats_print(srcu_ctlp, torture_type, TORTURE_FLAG);
}

static void srcu_torture_synchronize_expedited(void)
{
 synchronize_srcu_expedited(srcu_ctlp);
}

static struct rcu_torture_ops srcu_ops = {
 .ttype  = SRCU_FLAVOR,
 .init  = rcu_sync_torture_init,
 .readlock = srcu_torture_read_lock,
 .read_delay = srcu_read_delay,
 .readunlock = srcu_torture_read_unlock,
 .down_read = srcu_torture_down_read,
 .up_read = srcu_torture_up_read,
 .readlock_held = torture_srcu_read_lock_held,
 .get_gp_seq = srcu_torture_completed,
 .gp_diff = rcu_seq_diff,
 .deferred_free = srcu_torture_deferred_free,
 .sync  = srcu_torture_synchronize,
 .exp_sync = srcu_torture_synchronize_expedited,
 .same_gp_state = same_state_synchronize_srcu,
 .get_comp_state = get_completed_synchronize_srcu,
 .get_gp_state = srcu_torture_get_gp_state,
 .start_gp_poll = srcu_torture_start_gp_poll,
 .poll_gp_state = srcu_torture_poll_gp_state,
 .poll_active = NUM_ACTIVE_SRCU_POLL_OLDSTATE,
 .call  = srcu_torture_call,
 .cb_barrier = srcu_torture_barrier,
 .stats  = srcu_torture_stats,
 .get_gp_data = srcu_get_gp_data,
 .cbflood_max = 50000,
 .irq_capable = 1,
 .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
 .debug_objects = 1,
 .have_up_down = IS_ENABLED(CONFIG_TINY_SRCU)
    ? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST,
 .name  = "srcu"
};

static void srcu_torture_init(void)
{
 rcu_sync_torture_init();
 WARN_ON(init_srcu_struct(&srcu_ctld));
 srcu_ctlp = &srcu_ctld;
}

static void srcu_torture_cleanup(void)
{
 cleanup_srcu_struct(&srcu_ctld);
 srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */
}

/* As above, but dynamically allocated. */
static struct rcu_torture_ops srcud_ops = {
 .ttype  = SRCU_FLAVOR,
 .init  = srcu_torture_init,
 .cleanup = srcu_torture_cleanup,
 .readlock = srcu_torture_read_lock,
 .read_delay = srcu_read_delay,
 .readunlock = srcu_torture_read_unlock,
 .readlock_held = torture_srcu_read_lock_held,
 .down_read = srcu_torture_down_read,
 .up_read = srcu_torture_up_read,
 .get_gp_seq = srcu_torture_completed,
 .gp_diff = rcu_seq_diff,
 .deferred_free = srcu_torture_deferred_free,
 .sync  = srcu_torture_synchronize,
 .exp_sync = srcu_torture_synchronize_expedited,
 .same_gp_state = same_state_synchronize_srcu,
 .get_comp_state = get_completed_synchronize_srcu,
 .get_gp_state = srcu_torture_get_gp_state,
 .start_gp_poll = srcu_torture_start_gp_poll,
 .poll_gp_state = srcu_torture_poll_gp_state,
 .poll_active = NUM_ACTIVE_SRCU_POLL_OLDSTATE,
 .call  = srcu_torture_call,
 .cb_barrier = srcu_torture_barrier,
 .stats  = srcu_torture_stats,
 .get_gp_data = srcu_get_gp_data,
 .cbflood_max = 50000,
 .irq_capable = 1,
 .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
 .debug_objects = 1,
 .have_up_down = IS_ENABLED(CONFIG_TINY_SRCU)
    ? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST,
 .name  = "srcud"
};

/* As above, but broken due to inappropriate reader extension. */
static struct rcu_torture_ops busted_srcud_ops = {
 .ttype  = SRCU_FLAVOR,
 .init  = srcu_torture_init,
 .cleanup = srcu_torture_cleanup,
 .readlock = srcu_torture_read_lock,
 .read_delay = rcu_read_delay,
 .readunlock = srcu_torture_read_unlock,
 .readlock_held = torture_srcu_read_lock_held,
 .get_gp_seq = srcu_torture_completed,
 .deferred_free = srcu_torture_deferred_free,
 .sync  = srcu_torture_synchronize,
 .exp_sync = srcu_torture_synchronize_expedited,
 .call  = srcu_torture_call,
 .cb_barrier = srcu_torture_barrier,
 .stats  = srcu_torture_stats,
 .irq_capable = 1,
 .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
 .extendables = RCUTORTURE_MAX_EXTEND,
 .name  = "busted_srcud"
};

/*
 * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
 * This implementation does not work well with CPU hotplug nor
 * with rcutorture's shuffling.
 */

static void synchronize_rcu_trivial(void)
{
 int cpu;

 for_each_online_cpu(cpu) {
  torture_sched_setaffinity(current->pid, cpumask_of(cpu), true);
  WARN_ON_ONCE(raw_smp_processor_id() != cpu);
 }
}

static void rcu_sync_torture_init_trivial(void)
{
 rcu_sync_torture_init();
 // if (onoff_interval || shuffle_interval) {
 if (WARN_ONCE(onoff_interval || shuffle_interval, "%s: Non-zero onoff_interval (%d) or shuffle_interval (%d) breaks trivial RCU, resetting to zero", __func__, onoff_interval, shuffle_interval)) {
  onoff_interval = 0;
  shuffle_interval = 0;
 }
}

static int rcu_torture_read_lock_trivial(void)
{
 preempt_disable();
 return 0;
}

static void rcu_torture_read_unlock_trivial(int idx)
{
 preempt_enable();
}

static struct rcu_torture_ops trivial_ops = {
 .ttype  = RCU_TRIVIAL_FLAVOR,
 .init  = rcu_sync_torture_init_trivial,
 .readlock = rcu_torture_read_lock_trivial,
 .read_delay = rcu_read_delay,  /* just reuse rcu's version. */
 .readunlock = rcu_torture_read_unlock_trivial,
 .readlock_held = torture_readlock_not_held,
 .get_gp_seq = rcu_no_completed,
 .sync  = synchronize_rcu_trivial,
 .exp_sync = synchronize_rcu_trivial,
 .irq_capable = 1,
 .name  = "trivial"
};

#ifdef CONFIG_TASKS_RCU

/*
 * Definitions for RCU-tasks torture testing.
 */

static int tasks_torture_read_lock(void)
{
 return 0;
}

static void tasks_torture_read_unlock(int idx)
{
}

static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
{
 call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
}

static void synchronize_rcu_mult_test(void)
{
 synchronize_rcu_mult(call_rcu_tasks, call_rcu_hurry);
}

static struct rcu_torture_ops tasks_ops = {
 .ttype  = RCU_TASKS_FLAVOR,
 .init  = rcu_sync_torture_init,
 .readlock = tasks_torture_read_lock,
 .read_delay = rcu_read_delay,  /* just reuse rcu's version. */
 .readunlock = tasks_torture_read_unlock,
 .get_gp_seq = rcu_no_completed,
 .deferred_free = rcu_tasks_torture_deferred_free,
 .sync  = synchronize_rcu_tasks,
 .exp_sync = synchronize_rcu_mult_test,
 .call  = call_rcu_tasks,
 .cb_barrier = rcu_barrier_tasks,
 .gp_kthread_dbg = show_rcu_tasks_classic_gp_kthread,
 .get_gp_data = rcu_tasks_get_gp_data,
 .irq_capable = 1,
 .slow_gps = 1,
 .name  = "tasks"
};

#define TASKS_OPS &tasks_ops,

#else // #ifdef CONFIG_TASKS_RCU

#define TASKS_OPS

#endif // #else #ifdef CONFIG_TASKS_RCU


#ifdef CONFIG_TASKS_RUDE_RCU

/*
 * Definitions for rude RCU-tasks torture testing.
 */

static struct rcu_torture_ops tasks_rude_ops = {
 .ttype  = RCU_TASKS_RUDE_FLAVOR,
 .init  = rcu_sync_torture_init,
 .readlock = rcu_torture_read_lock_trivial,
 .read_delay = rcu_read_delay,  /* just reuse rcu's version. */
 .readunlock = rcu_torture_read_unlock_trivial,
 .get_gp_seq = rcu_no_completed,
 .sync  = synchronize_rcu_tasks_rude,
 .exp_sync = synchronize_rcu_tasks_rude,
 .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread,
 .get_gp_data = rcu_tasks_rude_get_gp_data,
 .cbflood_max = 50000,
 .irq_capable = 1,
 .name  = "tasks-rude"
};

#define TASKS_RUDE_OPS &tasks_rude_ops,

#else // #ifdef CONFIG_TASKS_RUDE_RCU

#define TASKS_RUDE_OPS

#endif // #else #ifdef CONFIG_TASKS_RUDE_RCU


#ifdef CONFIG_TASKS_TRACE_RCU

/*
 * Definitions for tracing RCU-tasks torture testing.
 */

static int tasks_tracing_torture_read_lock(void)
{
 rcu_read_lock_trace();
 return 0;
}

static void tasks_tracing_torture_read_unlock(int idx)
{
 rcu_read_unlock_trace();
}

static void rcu_tasks_tracing_torture_deferred_free(struct rcu_torture *p)
{
 call_rcu_tasks_trace(&p->rtort_rcu, rcu_torture_cb);
}

static struct rcu_torture_ops tasks_tracing_ops = {
 .ttype  = RCU_TASKS_TRACING_FLAVOR,
 .init  = rcu_sync_torture_init,
 .readlock = tasks_tracing_torture_read_lock,
 .read_delay = srcu_read_delay,  /* just reuse srcu's version. */
 .readunlock = tasks_tracing_torture_read_unlock,
 .readlock_held = rcu_read_lock_trace_held,
 .get_gp_seq = rcu_no_completed,
 .deferred_free = rcu_tasks_tracing_torture_deferred_free,
 .sync  = synchronize_rcu_tasks_trace,
 .exp_sync = synchronize_rcu_tasks_trace,
 .call  = call_rcu_tasks_trace,
 .cb_barrier = rcu_barrier_tasks_trace,
 .gp_kthread_dbg = show_rcu_tasks_trace_gp_kthread,
 .get_gp_data    = rcu_tasks_trace_get_gp_data,
 .cbflood_max = 50000,
 .irq_capable = 1,
 .slow_gps = 1,
 .name  = "tasks-tracing"
};

#define TASKS_TRACING_OPS &tasks_tracing_ops,

#else // #ifdef CONFIG_TASKS_TRACE_RCU

#define TASKS_TRACING_OPS

#endif // #else #ifdef CONFIG_TASKS_TRACE_RCU


static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
{
 if (!cur_ops->gp_diff)
  return new - old;
 return cur_ops->gp_diff(new, old);
}

/*
 * RCU torture priority-boost testing.  Runs one real-time thread per
 * CPU for moderate bursts, repeatedly starting grace periods and waiting
 * for them to complete.  If a given grace period takes too long, we assume
 * that priority inversion has occurred.
 */

static int old_rt_runtime = -1;

static void rcu_torture_disable_rt_throttle(void)
{
 /*
 * Disable RT throttling so that rcutorture's boost threads don't get
 * throttled. Only possible if rcutorture is built-in otherwise the
 * user should manually do this by setting the sched_rt_period_us and
 * sched_rt_runtime sysctls.
 */
 if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime != -1)
  return;

 old_rt_runtime = sysctl_sched_rt_runtime;
 sysctl_sched_rt_runtime = -1;
}

static void rcu_torture_enable_rt_throttle(void)
{
 if (!IS_BUILTIN(CONFIG_RCU_TORTURE_TEST) || old_rt_runtime == -1)
  return;

 sysctl_sched_rt_runtime = old_rt_runtime;
 old_rt_runtime = -1;
}

static bool rcu_torture_boost_failed(unsigned long gp_state, unsigned long *start)
{
 int cpu;
 static int dbg_done;
 unsigned long end = jiffies;
 bool gp_done;
 unsigned long j;
 static unsigned long last_persist;
 unsigned long lp;
 unsigned long mininterval = test_boost_duration * HZ - HZ / 2;

 if (end - *start > mininterval) {
  // Recheck after checking time to avoid false positives.
  smp_mb(); // Time check before grace-period check.
  if (cur_ops->poll_gp_state(gp_state))
   return false; // passed, though perhaps just barely
  if (cur_ops->check_boost_failed && !cur_ops->check_boost_failed(gp_state, &cpu)) {
   // At most one persisted message per boost test.
   j = jiffies;
   lp = READ_ONCE(last_persist);
   if (time_after(j, lp + mininterval) &&
       cmpxchg(&last_persist, lp, j) == lp) {
    if (cpu < 0)
     pr_info("Boost inversion persisted: QS from all CPUs\n");
    else
     pr_info("Boost inversion persisted: No QS from CPU %d\n", cpu);
   }
   return false; // passed on a technicality
  }
  VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");
  n_rcu_torture_boost_failure++;
  if (!xchg(&dbg_done, 1) && cur_ops->gp_kthread_dbg) {
   pr_info("Boost inversion thread ->rt_priority %u gp_state %lu jiffies %lu\n",
    current->rt_priority, gp_state, end - *start);
   cur_ops->gp_kthread_dbg();
   // Recheck after print to flag grace period ending during splat.
   gp_done = cur_ops->poll_gp_state(gp_state);
   pr_info("Boost inversion: GP %lu %s.\n", gp_state,
    gp_done ? "ended already" : "still pending");

  }

  return true; // failed
 } else if (cur_ops->check_boost_failed && !cur_ops->check_boost_failed(gp_state, NULL)) {
  *start = jiffies;
 }

 return false; // passed
}

static int rcu_torture_boost(void *arg)
{
 unsigned long endtime;
 unsigned long gp_state;
 unsigned long gp_state_time;
 unsigned long oldstarttime;
 unsigned long booststarttime = get_torture_init_jiffies() + test_boost_holdoff * HZ;

 if (test_boost_holdoff <= 0 || time_after(jiffies, booststarttime)) {
  VERBOSE_TOROUT_STRING("rcu_torture_boost started");
 } else {
  VERBOSE_TOROUT_STRING("rcu_torture_boost started holdoff period");
  while (time_before(jiffies, booststarttime)) {
   schedule_timeout_idle(HZ);
   if (kthread_should_stop())
    goto cleanup;
  }
  VERBOSE_TOROUT_STRING("rcu_torture_boost finished holdoff period");
 }

 /* Set real-time priority. */
 sched_set_fifo_low(current);

 /* Each pass through the following loop does one boost-test cycle. */
 do {
  bool failed = false; // Test failed already in this test interval
  bool gp_initiated = false;

  if (kthread_should_stop())
   goto checkwait;

  /* Wait for the next test interval. */
  oldstarttime = READ_ONCE(boost_starttime);
  while (time_before(jiffies, oldstarttime)) {
   schedule_timeout_interruptible(oldstarttime - jiffies);
   if (stutter_wait("rcu_torture_boost"))
    sched_set_fifo_low(current);
   if (torture_must_stop())
    goto checkwait;
  }

  // Do one boost-test interval.
  endtime = oldstarttime + test_boost_duration * HZ;
  while (time_before(jiffies, endtime)) {
   // Has current GP gone too long?
   if (gp_initiated && !failed && !cur_ops->poll_gp_state(gp_state))
    failed = rcu_torture_boost_failed(gp_state, &gp_state_time);
   // If we don't have a grace period in flight, start one.
   if (!gp_initiated || cur_ops->poll_gp_state(gp_state)) {
    gp_state = cur_ops->start_gp_poll();
    gp_initiated = true;
    gp_state_time = jiffies;
   }
   if (stutter_wait("rcu_torture_boost")) {
    sched_set_fifo_low(current);
    // If the grace period already ended,
    // we don't know when that happened, so
    // start over.
    if (cur_ops->poll_gp_state(gp_state))
     gp_initiated = false;
   }
   if (torture_must_stop())
    goto checkwait;
  }

  // In case the grace period extended beyond the end of the loop.
  if (gp_initiated && !failed && !cur_ops->poll_gp_state(gp_state))
   rcu_torture_boost_failed(gp_state, &gp_state_time);

  /*
 * Set the start time of the next test interval.
 * Yes, this is vulnerable to long delays, but such
 * delays simply cause a false negative for the next
 * interval.  Besides, we are running at RT priority,
 * so delays should be relatively rare.
 */
  while (oldstarttime == READ_ONCE(boost_starttime) && !kthread_should_stop()) {
   if (mutex_trylock(&boost_mutex)) {
    if (oldstarttime == boost_starttime) {
     WRITE_ONCE(boost_starttime,
         jiffies + test_boost_interval * HZ);
     n_rcu_torture_boosts++;
    }
    mutex_unlock(&boost_mutex);
    break;
   }
   schedule_timeout_uninterruptible(HZ / 20);
  }

  /* Go do the stutter. */
checkwait: if (stutter_wait("rcu_torture_boost"))
   sched_set_fifo_low(current);
 } while (!torture_must_stop());

cleanup:
 /* Clean up and exit. */
 while (!kthread_should_stop()) {
  torture_shutdown_absorb("rcu_torture_boost");
  schedule_timeout_uninterruptible(HZ / 20);
 }
 torture_kthread_stopping("rcu_torture_boost");
 return 0;
}

/*
 * RCU torture force-quiescent-state kthread.  Repeatedly induces
 * bursts of calls to force_quiescent_state(), increasing the probability
 * of occurrence of some important types of race conditions.
 */
static int
rcu_torture_fqs(void *arg)
{
 unsigned long fqs_resume_time;
 int fqs_burst_remaining;
 int oldnice = task_nice(current);

 VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
 do {
  fqs_resume_time = jiffies + fqs_stutter * HZ;
  while (time_before(jiffies, fqs_resume_time) &&
         !kthread_should_stop()) {
   schedule_timeout_interruptible(HZ / 20);
  }
  fqs_burst_remaining = fqs_duration;
  while (fqs_burst_remaining > 0 &&
         !kthread_should_stop()) {
   cur_ops->fqs();
   udelay(fqs_holdoff);
   fqs_burst_remaining -= fqs_holdoff;
  }
  if (stutter_wait("rcu_torture_fqs"))
   sched_set_normal(current, oldnice);
 } while (!torture_must_stop());
 torture_kthread_stopping("rcu_torture_fqs");
 return 0;
}

// Used by writers to randomly choose from the available grace-period primitives.
static int synctype[ARRAY_SIZE(rcu_torture_writer_state_names)] = { };
static int nsynctypes;

/*
 * Determine which grace-period primitives are available.
 */
static void rcu_torture_write_types(void)
{
 bool gp_cond1 = gp_cond, gp_cond_exp1 = gp_cond_exp, gp_cond_full1 = gp_cond_full;
 bool gp_cond_exp_full1 = gp_cond_exp_full, gp_exp1 = gp_exp, gp_poll_exp1 = gp_poll_exp;
 bool gp_poll_exp_full1 = gp_poll_exp_full, gp_normal1 = gp_normal, gp_poll1 = gp_poll;
 bool gp_poll_full1 = gp_poll_full, gp_sync1 = gp_sync;

 /* Initialize synctype[] array.  If none set, take default. */
 if (!gp_cond1 &&
     !gp_cond_exp1 &&
     !gp_cond_full1 &&
     !gp_cond_exp_full1 &&
     !gp_exp1 &&
     !gp_poll_exp1 &&
     !gp_poll_exp_full1 &&
     !gp_normal1 &&
     !gp_poll1 &&
     !gp_poll_full1 &&
     !gp_sync1) {
  gp_cond1 = true;
  gp_cond_exp1 = true;
  gp_cond_full1 = true;
  gp_cond_exp_full1 = true;
  gp_exp1 = true;
  gp_poll_exp1 = true;
  gp_poll_exp_full1 = true;
  gp_normal1 = true;
  gp_poll1 = true;
  gp_poll_full1 = true;
  gp_sync1 = true;
 }
 if (gp_cond1 && cur_ops->get_gp_state && cur_ops->cond_sync) {
  synctype[nsynctypes++] = RTWS_COND_GET;
  pr_info("%s: Testing conditional GPs.\n", __func__);
 } else if (gp_cond && (!cur_ops->get_gp_state || !cur_ops->cond_sync)) {
  pr_alert("%s: gp_cond without primitives.\n", __func__);
 }
 if (gp_cond_exp1 && cur_ops->get_gp_state_exp && cur_ops->cond_sync_exp) {
  synctype[nsynctypes++] = RTWS_COND_GET_EXP;
  pr_info("%s: Testing conditional expedited GPs.\n", __func__);
 } else if (gp_cond_exp && (!cur_ops->get_gp_state_exp || !cur_ops->cond_sync_exp)) {
  pr_alert("%s: gp_cond_exp without primitives.\n", __func__);
 }
 if (gp_cond_full1 && cur_ops->get_gp_state && cur_ops->cond_sync_full) {
  synctype[nsynctypes++] = RTWS_COND_GET_FULL;
  pr_info("%s: Testing conditional full-state GPs.\n", __func__);
 } else if (gp_cond_full && (!cur_ops->get_gp_state || !cur_ops->cond_sync_full)) {
  pr_alert("%s: gp_cond_full without primitives.\n", __func__);
 }
 if (gp_cond_exp_full1 && cur_ops->get_gp_state_exp && cur_ops->cond_sync_exp_full) {
  synctype[nsynctypes++] = RTWS_COND_GET_EXP_FULL;
  pr_info("%s: Testing conditional full-state expedited GPs.\n", __func__);
 } else if (gp_cond_exp_full &&
     (!cur_ops->get_gp_state_exp || !cur_ops->cond_sync_exp_full)) {
  pr_alert("%s: gp_cond_exp_full without primitives.\n", __func__);
 }
 if (gp_exp1 && cur_ops->exp_sync) {
  synctype[nsynctypes++] = RTWS_EXP_SYNC;
  pr_info("%s: Testing expedited GPs.\n", __func__);
 } else if (gp_exp && !cur_ops->exp_sync) {
  pr_alert("%s: gp_exp without primitives.\n", __func__);
 }
 if (gp_normal1 && cur_ops->deferred_free) {
  synctype[nsynctypes++] = RTWS_DEF_FREE;
  pr_info("%s: Testing asynchronous GPs.\n", __func__);
 } else if (gp_normal && !cur_ops->deferred_free) {
  pr_alert("%s: gp_normal without primitives.\n", __func__);
 }
 if (gp_poll1 && cur_ops->get_comp_state && cur_ops->same_gp_state &&
     cur_ops->start_gp_poll && cur_ops->poll_gp_state) {
  synctype[nsynctypes++] = RTWS_POLL_GET;
  pr_info("%s: Testing polling GPs.\n", __func__);
 } else if (gp_poll && (!cur_ops->start_gp_poll || !cur_ops->poll_gp_state)) {
  pr_alert("%s: gp_poll without primitives.\n", __func__);
 }
 if (gp_poll_full1 && cur_ops->get_comp_state_full && cur_ops->same_gp_state_full
     && cur_ops->start_gp_poll_full && cur_ops->poll_gp_state_full) {
  synctype[nsynctypes++] = RTWS_POLL_GET_FULL;
  pr_info("%s: Testing polling full-state GPs.\n", __func__);
 } else if (gp_poll_full && (!cur_ops->start_gp_poll_full || !cur_ops->poll_gp_state_full)) {
  pr_alert("%s: gp_poll_full without primitives.\n", __func__);
 }
 if (gp_poll_exp1 && cur_ops->start_gp_poll_exp && cur_ops->poll_gp_state_exp) {
  synctype[nsynctypes++] = RTWS_POLL_GET_EXP;
  pr_info("%s: Testing polling expedited GPs.\n", __func__);
 } else if (gp_poll_exp && (!cur_ops->start_gp_poll_exp || !cur_ops->poll_gp_state_exp)) {
  pr_alert("%s: gp_poll_exp without primitives.\n", __func__);
 }
 if (gp_poll_exp_full1 && cur_ops->start_gp_poll_exp_full && cur_ops->poll_gp_state_full) {
  synctype[nsynctypes++] = RTWS_POLL_GET_EXP_FULL;
  pr_info("%s: Testing polling full-state expedited GPs.\n", __func__);
 } else if (gp_poll_exp_full &&
     (!cur_ops->start_gp_poll_exp_full || !cur_ops->poll_gp_state_full)) {
  pr_alert("%s: gp_poll_exp_full without primitives.\n", __func__);
 }
 if (gp_sync1 && cur_ops->sync) {
  synctype[nsynctypes++] = RTWS_SYNC;
  pr_info("%s: Testing normal GPs.\n", __func__);
 } else if (gp_sync && !cur_ops->sync) {
  pr_alert("%s: gp_sync without primitives.\n", __func__);
 }
 pr_alert("%s: Testing %d update types.\n", __func__, nsynctypes);
 pr_info("%s: gp_cond_wi %d gp_cond_wi_exp %d gp_poll_wi %d gp_poll_wi_exp %d\n", __func__, gp_cond_wi, gp_cond_wi_exp, gp_poll_wi, gp_poll_wi_exp);
}

/*
 * Do the specified rcu_torture_writer() synchronous grace period,
 * while also testing out the polled APIs.  Note well that the single-CPU
 * grace-period optimizations must be accounted for.
 */
static void do_rtws_sync(struct torture_random_state *trsp, void (*sync)(void))
{
 unsigned long cookie;
 struct rcu_gp_oldstate cookie_full;
 bool dopoll;
 bool dopoll_full;
 unsigned long r = torture_random(trsp);

 dopoll = cur_ops->get_gp_state && cur_ops->poll_gp_state && !(r & 0x300);
 dopoll_full = cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full && !(r & 0xc00);
 if (dopoll || dopoll_full)
  cpus_read_lock();
 if (dopoll)
  cookie = cur_ops->get_gp_state();
 if (dopoll_full)
  cur_ops->get_gp_state_full(&cookie_full);
 if (cur_ops->poll_need_2gp && cur_ops->poll_need_2gp(dopoll, dopoll_full))
  sync();
 sync();
 WARN_ONCE(dopoll && !cur_ops->poll_gp_state(cookie),
    "%s: Cookie check 3 failed %pS() online %*pbl.",
    __func__, sync, cpumask_pr_args(cpu_online_mask));
 WARN_ONCE(dopoll_full && !cur_ops->poll_gp_state_full(&cookie_full),
    "%s: Cookie check 4 failed %pS() online %*pbl",
    __func__, sync, cpumask_pr_args(cpu_online_mask));
 if (dopoll || dopoll_full)
  cpus_read_unlock();
}

/*
 * RCU torture writer kthread.  Repeatedly substitutes a new structure
 * for that pointed to by rcu_torture_current, freeing the old structure
 * after a series of grace periods (the "pipeline").
 */
static int
rcu_torture_writer(void *arg)
{
 bool boot_ended;
 bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
 unsigned long cookie;
 struct rcu_gp_oldstate cookie_full;
 int expediting = 0;
 unsigned long gp_snap;
 unsigned long gp_snap1;
 struct rcu_gp_oldstate gp_snap_full;
 struct rcu_gp_oldstate gp_snap1_full;
 int i;
 int idx;
 int oldnice = task_nice(current);
 struct rcu_gp_oldstate *rgo = NULL;
 int rgo_size = 0;
 struct rcu_torture *rp;
 struct rcu_torture *old_rp;
 static DEFINE_TORTURE_RANDOM(rand);
 unsigned long stallsdone = jiffies;
 bool stutter_waited;
 unsigned long *ulo = NULL;
 int ulo_size = 0;

 // If a new stall test is added, this must be adjusted.
 if (stall_cpu_holdoff + stall_gp_kthread + stall_cpu)
  stallsdone += (stall_cpu_holdoff + stall_gp_kthread + stall_cpu + 60) *
         HZ * (stall_cpu_repeat + 1);
 VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
 if (!can_expedite)
  pr_alert("%s" TORTURE_FLAG
    " GP expediting controlled from boot/sysfs for %s.\n",
    torture_type, cur_ops->name);
 if (WARN_ONCE(nsynctypes == 0,
        "%s: No update-side primitives.\n", __func__)) {
  /*
 * No updates primitives, so don't try updating.
 * The resulting test won't be testing much, hence the
 * above WARN_ONCE().
 */
  rcu_torture_writer_state = RTWS_STOPPING;
  torture_kthread_stopping("rcu_torture_writer");
  return 0;
 }
 if (cur_ops->poll_active > 0) {
  ulo = kzalloc(cur_ops->poll_active * sizeof(ulo[0]), GFP_KERNEL);
  if (!WARN_ON(!ulo))
   ulo_size = cur_ops->poll_active;
 }
 if (cur_ops->poll_active_full > 0) {
  rgo = kzalloc(cur_ops->poll_active_full * sizeof(rgo[0]), GFP_KERNEL);
  if (!WARN_ON(!rgo))
   rgo_size = cur_ops->poll_active_full;
 }

 do {
  rcu_torture_writer_state = RTWS_FIXED_DELAY;
  torture_hrtimeout_us(500, 1000, &rand);
  rp = rcu_torture_alloc();
  if (rp == NULL)
   continue;
  rp->rtort_pipe_count = 0;
  ASSERT_EXCLUSIVE_WRITER(rp->rtort_pipe_count);
  rcu_torture_writer_state = RTWS_DELAY;
  udelay(torture_random(&rand) & 0x3ff);
  rcu_torture_writer_state = RTWS_REPLACE;
  old_rp = rcu_dereference_check(rcu_torture_current,
            current == writer_task);
  rp->rtort_mbtest = 1;
  rcu_assign_pointer(rcu_torture_current, rp);
  smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
  if (old_rp) {
   i = old_rp->rtort_pipe_count;
   if (i > RCU_TORTURE_PIPE_LEN)
    i = RCU_TORTURE_PIPE_LEN;
   atomic_inc(&rcu_torture_wcount[i]);
   WRITE_ONCE(old_rp->rtort_pipe_count,
       old_rp->rtort_pipe_count + 1);
   ASSERT_EXCLUSIVE_WRITER(old_rp->rtort_pipe_count);

   // Make sure readers block polled grace periods.
   if (cur_ops->get_gp_state && cur_ops->poll_gp_state) {
    idx = cur_ops->readlock();
    cookie = cur_ops->get_gp_state();
    WARN_ONCE(cur_ops->poll_gp_state(cookie),
       "%s: Cookie check 1 failed %s(%d) %lu->%lu\n",
       __func__,
       rcu_torture_writer_state_getname(),
       rcu_torture_writer_state,
       cookie, cur_ops->get_gp_state());
    if (cur_ops->get_comp_state) {
     cookie = cur_ops->get_comp_state();
     WARN_ON_ONCE(!cur_ops->poll_gp_state(cookie));
    }
    cur_ops->readunlock(idx);
   }
   if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full) {
    idx = cur_ops->readlock();
    cur_ops->get_gp_state_full(&cookie_full);
    WARN_ONCE(cur_ops->poll_gp_state_full(&cookie_full),
       "%s: Cookie check 5 failed %s(%d) online %*pbl\n",
       __func__,
       rcu_torture_writer_state_getname(),
       rcu_torture_writer_state,
       cpumask_pr_args(cpu_online_mask));
    if (cur_ops->get_comp_state_full) {
     cur_ops->get_comp_state_full(&cookie_full);
     WARN_ON_ONCE(!cur_ops->poll_gp_state_full(&cookie_full));
    }
    cur_ops->readunlock(idx);
   }
   switch (synctype[torture_random(&rand) % nsynctypes]) {
   case RTWS_DEF_FREE:
    rcu_torture_writer_state = RTWS_DEF_FREE;
    cur_ops->deferred_free(old_rp);
    break;
   case RTWS_EXP_SYNC:
    rcu_torture_writer_state = RTWS_EXP_SYNC;
    do_rtws_sync(&rand, cur_ops->exp_sync);
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_COND_GET:
    rcu_torture_writer_state = RTWS_COND_GET;
    gp_snap = cur_ops->get_gp_state();
    torture_hrtimeout_us(torture_random(&rand) % gp_cond_wi,
           1000, &rand);
    rcu_torture_writer_state = RTWS_COND_SYNC;
    cur_ops->cond_sync(gp_snap);
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_COND_GET_EXP:
    rcu_torture_writer_state = RTWS_COND_GET_EXP;
    gp_snap = cur_ops->get_gp_state_exp();
    torture_hrtimeout_us(torture_random(&rand) % gp_cond_wi_exp,
           1000, &rand);
    rcu_torture_writer_state = RTWS_COND_SYNC_EXP;
    cur_ops->cond_sync_exp(gp_snap);
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_COND_GET_FULL:
    rcu_torture_writer_state = RTWS_COND_GET_FULL;
    cur_ops->get_gp_state_full(&gp_snap_full);
    torture_hrtimeout_us(torture_random(&rand) % gp_cond_wi,
           1000, &rand);
    rcu_torture_writer_state = RTWS_COND_SYNC_FULL;
    cur_ops->cond_sync_full(&gp_snap_full);
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_COND_GET_EXP_FULL:
    rcu_torture_writer_state = RTWS_COND_GET_EXP_FULL;
    cur_ops->get_gp_state_full(&gp_snap_full);
    torture_hrtimeout_us(torture_random(&rand) % gp_cond_wi_exp,
           1000, &rand);
    rcu_torture_writer_state = RTWS_COND_SYNC_EXP_FULL;
    cur_ops->cond_sync_exp_full(&gp_snap_full);
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_POLL_GET:
    rcu_torture_writer_state = RTWS_POLL_GET;
    for (i = 0; i < ulo_size; i++)
     ulo[i] = cur_ops->get_comp_state();
    gp_snap = cur_ops->start_gp_poll();
    rcu_torture_writer_state = RTWS_POLL_WAIT;
    while (!cur_ops->poll_gp_state(gp_snap)) {
     gp_snap1 = cur_ops->get_gp_state();
     for (i = 0; i < ulo_size; i++)
      if (cur_ops->poll_gp_state(ulo[i]) ||
          cur_ops->same_gp_state(ulo[i], gp_snap1)) {
       ulo[i] = gp_snap1;
       break;
      }
     WARN_ON_ONCE(ulo_size > 0 && i >= ulo_size);
     torture_hrtimeout_us(torture_random(&rand) % gp_poll_wi,
            1000, &rand);
    }
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_POLL_GET_FULL:
    rcu_torture_writer_state = RTWS_POLL_GET_FULL;
    for (i = 0; i < rgo_size; i++)
     cur_ops->get_comp_state_full(&rgo[i]);
    cur_ops->start_gp_poll_full(&gp_snap_full);
    rcu_torture_writer_state = RTWS_POLL_WAIT_FULL;
    while (!cur_ops->poll_gp_state_full(&gp_snap_full)) {
     cur_ops->get_gp_state_full(&gp_snap1_full);
     for (i = 0; i < rgo_size; i++)
      if (cur_ops->poll_gp_state_full(&rgo[i]) ||
          cur_ops->same_gp_state_full(&rgo[i],
          &gp_snap1_full)) {
       rgo[i] = gp_snap1_full;
       break;
      }
     WARN_ON_ONCE(rgo_size > 0 && i >= rgo_size);
     torture_hrtimeout_us(torture_random(&rand) % gp_poll_wi,
            1000, &rand);
    }
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_POLL_GET_EXP:
    rcu_torture_writer_state = RTWS_POLL_GET_EXP;
    gp_snap = cur_ops->start_gp_poll_exp();
    rcu_torture_writer_state = RTWS_POLL_WAIT_EXP;
    while (!cur_ops->poll_gp_state_exp(gp_snap))
     torture_hrtimeout_us(torture_random(&rand) % gp_poll_wi_exp,
            1000, &rand);
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_POLL_GET_EXP_FULL:
    rcu_torture_writer_state = RTWS_POLL_GET_EXP_FULL;
    cur_ops->start_gp_poll_exp_full(&gp_snap_full);
    rcu_torture_writer_state = RTWS_POLL_WAIT_EXP_FULL;
    while (!cur_ops->poll_gp_state_full(&gp_snap_full))
     torture_hrtimeout_us(torture_random(&rand) % gp_poll_wi_exp,
            1000, &rand);
    rcu_torture_pipe_update(old_rp);
    break;
   case RTWS_SYNC:
    rcu_torture_writer_state = RTWS_SYNC;
    do_rtws_sync(&rand, cur_ops->sync);
    rcu_torture_pipe_update(old_rp);
    break;
   default:
    WARN_ON_ONCE(1);
    break;
   }
  }
  WRITE_ONCE(rcu_torture_current_version,
      rcu_torture_current_version + 1);
  /* Cycle through nesting levels of rcu_expedite_gp() calls. */
  if (can_expedite &&
      !(torture_random(&rand) & 0xff & (!!expediting - 1))) {
   WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited());
   if (expediting >= 0)
    rcu_expedite_gp();
   else
    rcu_unexpedite_gp();
   if (++expediting > 3)
    expediting = -expediting;
  } else if (!can_expedite) { /* Disabled during boot, recheck. */
   can_expedite = !rcu_gp_is_expedited() &&
           !rcu_gp_is_normal();
  }
  rcu_torture_writer_state = RTWS_STUTTER;
  boot_ended = rcu_inkernel_boot_has_ended();
  stutter_waited = stutter_wait("rcu_torture_writer");
  if (stutter_waited &&
      !atomic_read(&rcu_fwd_cb_nodelay) &&
      !cur_ops->slow_gps &&
      !torture_must_stop() &&
      boot_ended &&
      time_after(jiffies, stallsdone))
   for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
    if (list_empty(&rcu_tortures[i].rtort_free) &&
        rcu_access_pointer(rcu_torture_current) != &rcu_tortures[i]) {
     tracing_off();
     if (cur_ops->gp_kthread_dbg)
      cur_ops->gp_kthread_dbg();
     WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
     rcu_ftrace_dump(DUMP_ALL);
     break;
    }
  if (stutter_waited)
   sched_set_normal(current, oldnice);
 } while (!torture_must_stop());
 rcu_torture_current = NULL;  // Let stats task know that we are done.
 /* Reset expediting back to unexpedited. */
 if (expediting > 0)
  expediting = -expediting;
 while (can_expedite && expediting++ < 0)
  rcu_unexpedite_gp();
 WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited());
 if (!can_expedite)
  pr_alert("%s" TORTURE_FLAG
    " Dynamic grace-period expediting was disabled.\n",
    torture_type);
 kfree(ulo);
 kfree(rgo);
 rcu_torture_writer_state = RTWS_STOPPING;
 torture_kthread_stopping("rcu_torture_writer");
 return 0;
}

/*
 * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
 * delay between calls.
 */
static int
rcu_torture_fakewriter(void *arg)
{
 unsigned long gp_snap;
 struct rcu_gp_oldstate gp_snap_full;
 DEFINE_TORTURE_RANDOM(rand);

 VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
 set_user_nice(current, MAX_NICE);

 if (WARN_ONCE(nsynctypes == 0,
        "%s: No update-side primitives.\n", __func__)) {
  /*
 * No updates primitives, so don't try updating.
 * The resulting test won't be testing much, hence the
 * above WARN_ONCE().
 */
  torture_kthread_stopping("rcu_torture_fakewriter");
  return 0;
 }

 do {
  torture_hrtimeout_jiffies(torture_random(&rand) % 10, &rand);
  if (cur_ops->cb_barrier != NULL &&
      torture_random(&rand) % (nrealfakewriters * 8) == 0) {
   cur_ops->cb_barrier();
  } else {
   switch (synctype[torture_random(&rand) % nsynctypes]) {
   case RTWS_DEF_FREE:
    break;
   case RTWS_EXP_SYNC:
    cur_ops->exp_sync();
    break;
   case RTWS_COND_GET:
    gp_snap = cur_ops->get_gp_state();
    torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
    cur_ops->cond_sync(gp_snap);
    break;
   case RTWS_COND_GET_EXP:
    gp_snap = cur_ops->get_gp_state_exp();
    torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
    cur_ops->cond_sync_exp(gp_snap);
    break;
   case RTWS_COND_GET_FULL:
    cur_ops->get_gp_state_full(&gp_snap_full);
    torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
    cur_ops->cond_sync_full(&gp_snap_full);
    break;
   case RTWS_COND_GET_EXP_FULL:
    cur_ops->get_gp_state_full(&gp_snap_full);
    torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
    cur_ops->cond_sync_exp_full(&gp_snap_full);
    break;
   case RTWS_POLL_GET:
    if (cur_ops->start_poll_irqsoff)
     local_irq_disable();
    gp_snap = cur_ops->start_gp_poll();
    if (cur_ops->start_poll_irqsoff)
     local_irq_enable();
    while (!cur_ops->poll_gp_state(gp_snap)) {
     torture_hrtimeout_jiffies(torture_random(&rand) % 16,
          &rand);
    }
    break;
   case RTWS_POLL_GET_FULL:
    if (cur_ops->start_poll_irqsoff)
     local_irq_disable();
    cur_ops->start_gp_poll_full(&gp_snap_full);
    if (cur_ops->start_poll_irqsoff)
     local_irq_enable();
    while (!cur_ops->poll_gp_state_full(&gp_snap_full)) {
     torture_hrtimeout_jiffies(torture_random(&rand) % 16,
          &rand);
    }
    break;
   case RTWS_POLL_GET_EXP:
    gp_snap = cur_ops->start_gp_poll_exp();
    while (!cur_ops->poll_gp_state_exp(gp_snap)) {
     torture_hrtimeout_jiffies(torture_random(&rand) % 16,
          &rand);
    }
    break;
   case RTWS_POLL_GET_EXP_FULL:
    cur_ops->start_gp_poll_exp_full(&gp_snap_full);
    while (!cur_ops->poll_gp_state_full(&gp_snap_full)) {
     torture_hrtimeout_jiffies(torture_random(&rand) % 16,
          &rand);
    }
    break;
   case RTWS_SYNC:
    cur_ops->sync();
    break;
   default:
    WARN_ON_ONCE(1);
    break;
   }
  }
  stutter_wait("rcu_torture_fakewriter");
 } while (!torture_must_stop());

 torture_kthread_stopping("rcu_torture_fakewriter");
 return 0;
}

static void rcu_torture_timer_cb(struct rcu_head *rhp)
{
 kfree(rhp);
}

// Set up and carry out testing of RCU's global memory ordering
static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp,
     struct torture_random_state *trsp)
{
 unsigned long loops;
 int noc = torture_num_online_cpus();
 int rdrchked;
 int rdrchker;
 struct rcu_torture_reader_check *rtrcp; // Me.
 struct rcu_torture_reader_check *rtrcp_assigner; // Assigned us to do checking.
 struct rcu_torture_reader_check *rtrcp_chked; // Reader being checked.
 struct rcu_torture_reader_check *rtrcp_chker; // Reader doing checking when not me.

 if (myid < 0)
  return; // Don't try this from timer handlers.

 // Increment my counter.
 rtrcp = &rcu_torture_reader_mbchk[myid];
 WRITE_ONCE(rtrcp->rtc_myloops, rtrcp->rtc_myloops + 1);

 // Attempt to assign someone else some checking work.
 rdrchked = torture_random(trsp) % nrealreaders;
 rtrcp_chked = &rcu_torture_reader_mbchk[rdrchked];
 rdrchker = torture_random(trsp) % nrealreaders;
 rtrcp_chker = &rcu_torture_reader_mbchk[rdrchker];
 if (rdrchked != myid && rdrchked != rdrchker && noc >= rdrchked && noc >= rdrchker &&
     smp_load_acquire(&rtrcp->rtc_chkrdr) < 0 && // Pairs with smp_store_release below.
     !READ_ONCE(rtp->rtort_chkp) &&
     !smp_load_acquire(&rtrcp_chker->rtc_assigner)) { // Pairs with smp_store_release below.
  rtrcp->rtc_chkloops = READ_ONCE(rtrcp_chked->rtc_myloops);
  WARN_ON_ONCE(rtrcp->rtc_chkrdr >= 0);
  rtrcp->rtc_chkrdr = rdrchked;
  WARN_ON_ONCE(rtrcp->rtc_ready); // This gets set after the grace period ends.
  if (cmpxchg_relaxed(&rtrcp_chker->rtc_assigner, NULL, rtrcp) ||
      cmpxchg_relaxed(&rtp->rtort_chkp, NULL, rtrcp))
--> --------------------

--> maximum size reached

--> --------------------