rcu: Move RCU-related source code to kernel/rcu directory

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2145 insertions, 0 deletions

diff --git a/kernel/rcu/torture.c b/kernel/rcu/torture.c
new file mode 100644
index 0000000..3929cd4
--- /dev/null
+++ b/kernel/rcu/torture.c
@@ -0,0 +1,2145 @@
+/*
+ * Read-Copy Update module-based torture test facility
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2005, 2006
+ *
+ * Authors: Paul E. McKenney <paulmck@us.ibm.com>
+ *	  Josh Triplett <josh@freedesktop.org>
+ *
+ * See also:  Documentation/RCU/torture.txt
+ */
+#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.h>
+#include <linux/interrupt.h>
+#include <linux/sched.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>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@freedesktop.org>");
+
+MODULE_ALIAS("rcutorture");
+#ifdef MODULE_PARAM_PREFIX
+#undef MODULE_PARAM_PREFIX
+#endif
+#define MODULE_PARAM_PREFIX "rcutorture."
+
+static int fqs_duration;
+module_param(fqs_duration, int, 0444);
+MODULE_PARM_DESC(fqs_duration, "Duration of fqs bursts (us), 0 to disable");
+static int fqs_holdoff;
+module_param(fqs_holdoff, int, 0444);
+MODULE_PARM_DESC(fqs_holdoff, "Holdoff time within fqs bursts (us)");
+static int fqs_stutter = 3;
+module_param(fqs_stutter, int, 0444);
+MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
+static bool gp_exp;
+module_param(gp_exp, bool, 0444);
+MODULE_PARM_DESC(gp_exp, "Use expedited GP wait primitives");
+static bool gp_normal;
+module_param(gp_normal, bool, 0444);
+MODULE_PARM_DESC(gp_normal, "Use normal (non-expedited) GP wait primitives");
+static int irqreader = 1;
+module_param(irqreader, int, 0444);
+MODULE_PARM_DESC(irqreader, "Allow RCU readers from irq handlers");
+static int n_barrier_cbs;
+module_param(n_barrier_cbs, int, 0444);
+MODULE_PARM_DESC(n_barrier_cbs, "# of callbacks/kthreads for barrier testing");
+static int nfakewriters = 4;
+module_param(nfakewriters, int, 0444);
+MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
+static int nreaders = -1;
+module_param(nreaders, int, 0444);
+MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
+static int object_debug;
+module_param(object_debug, int, 0444);
+MODULE_PARM_DESC(object_debug, "Enable debug-object double call_rcu() testing");
+static int onoff_holdoff;
+module_param(onoff_holdoff, int, 0444);
+MODULE_PARM_DESC(onoff_holdoff, "Time after boot before CPU hotplugs (s)");
+static int onoff_interval;
+module_param(onoff_interval, int, 0444);
+MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
+static int shuffle_interval = 3;
+module_param(shuffle_interval, int, 0444);
+MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
+static int shutdown_secs;
+module_param(shutdown_secs, int, 0444);
+MODULE_PARM_DESC(shutdown_secs, "Shutdown time (s), <= zero to disable.");
+static int stall_cpu;
+module_param(stall_cpu, int, 0444);
+MODULE_PARM_DESC(stall_cpu, "Stall duration (s), zero to disable.");
+static int stall_cpu_holdoff = 10;
+module_param(stall_cpu_holdoff, int, 0444);
+MODULE_PARM_DESC(stall_cpu_holdoff, "Time to wait before starting stall (s).");
+static int stat_interval = 60;
+module_param(stat_interval, int, 0644);
+MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
+static int stutter = 5;
+module_param(stutter, int, 0444);
+MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
+static int test_boost = 1;
+module_param(test_boost, int, 0444);
+MODULE_PARM_DESC(test_boost, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
+static int test_boost_duration = 4;
+module_param(test_boost_duration, int, 0444);
+MODULE_PARM_DESC(test_boost_duration, "Duration of each boost test, seconds.");
+static int test_boost_interval = 7;
+module_param(test_boost_interval, int, 0444);
+MODULE_PARM_DESC(test_boost_interval, "Interval between boost tests, seconds.");
+static bool test_no_idle_hz = true;
+module_param(test_no_idle_hz, bool, 0444);
+MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
+static char *torture_type = "rcu";
+module_param(torture_type, charp, 0444);
+MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, ...)");
+static bool verbose;
+module_param(verbose, bool, 0444);
+MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
+
+#define TORTURE_FLAG "-torture:"
+#define PRINTK_STRING(s) \
+	do { pr_alert("%s" TORTURE_FLAG s "\n", torture_type); } while (0)
+#define VERBOSE_PRINTK_STRING(s) \
+	do { if (verbose) pr_alert("%s" TORTURE_FLAG s "\n", torture_type); } while (0)
+#define VERBOSE_PRINTK_ERRSTRING(s) \
+	do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
+
+static char printk_buf[4096];
+
+static int nrealreaders;
+static struct task_struct *writer_task;
+static struct task_struct **fakewriter_tasks;
+static struct task_struct **reader_tasks;
+static struct task_struct *stats_task;
+static struct task_struct *shuffler_task;
+static struct task_struct *stutter_task;
+static struct task_struct *fqs_task;
+static struct task_struct *boost_tasks[NR_CPUS];
+static struct task_struct *shutdown_task;
+#ifdef CONFIG_HOTPLUG_CPU
+static struct task_struct *onoff_task;
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+static struct task_struct *stall_task;
+static struct task_struct **barrier_cbs_tasks;
+static struct task_struct *barrier_task;
+
+#define RCU_TORTURE_PIPE_LEN 10
+
+struct rcu_torture {
+	struct rcu_head rtort_rcu;
+	int rtort_pipe_count;
+	struct list_head rtort_free;
+	int rtort_mbtest;
+};
+
+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) =
+	{ 0 };
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
+	{ 0 };
+static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
+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_error;
+static long n_rcu_torture_barrier_error;
+static long n_rcu_torture_boost_ktrerror;
+static long n_rcu_torture_boost_rterror;
+static long n_rcu_torture_boost_failure;
+static long n_rcu_torture_boosts;
+static long n_rcu_torture_timers;
+static long n_offline_attempts;
+static long n_offline_successes;
+static unsigned long sum_offline;
+static int min_offline = -1;
+static int max_offline;
+static long n_online_attempts;
+static long n_online_successes;
+static unsigned long sum_online;
+static int min_online = -1;
+static int max_online;
+static long n_barrier_attempts;
+static long n_barrier_successes;
+static struct list_head rcu_torture_removed;
+static cpumask_var_t shuffle_tmp_mask;
+
+static int stutter_pause_test;
+
+#if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
+#define RCUTORTURE_RUNNABLE_INIT 1
+#else
+#define RCUTORTURE_RUNNABLE_INIT 0
+#endif
+int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
+module_param(rcutorture_runnable, int, 0444);
+MODULE_PARM_DESC(rcutorture_runnable, "Start rcutorture at boot");
+
+#if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU)
+#define rcu_can_boost() 1
+#else /* #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
+#define rcu_can_boost() 0
+#endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
+
+#ifdef CONFIG_RCU_TRACE
+static u64 notrace rcu_trace_clock_local(void)
+{
+	u64 ts = trace_clock_local();
+	unsigned long __maybe_unused ts_rem = 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 */
+
+static unsigned long shutdown_time;	/* jiffies to system shutdown. */
+static unsigned long boost_starttime;	/* jiffies of next boost test start. */
+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);
+
+/* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
+
+#define FULLSTOP_DONTSTOP 0	/* Normal operation. */
+#define FULLSTOP_SHUTDOWN 1	/* System shutdown with rcutorture running. */
+#define FULLSTOP_RMMOD    2	/* Normal rmmod of rcutorture. */
+static int fullstop = FULLSTOP_RMMOD;
+/*
+ * Protect fullstop transitions and spawning of kthreads.
+ */
+static DEFINE_MUTEX(fullstop_mutex);
+
+/* Forward reference. */
+static void rcu_torture_cleanup(void);
+
+/*
+ * Detect and respond to a system shutdown.
+ */
+static int
+rcutorture_shutdown_notify(struct notifier_block *unused1,
+			   unsigned long unused2, void *unused3)
+{
+	mutex_lock(&fullstop_mutex);
+	if (fullstop == FULLSTOP_DONTSTOP)
+		fullstop = FULLSTOP_SHUTDOWN;
+	else
+		pr_warn(/* but going down anyway, so... */
+		       "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
+	mutex_unlock(&fullstop_mutex);
+	return NOTIFY_DONE;
+}
+
+/*
+ * Absorb kthreads into a kernel function that won't return, so that
+ * they won't ever access module text or data again.
+ */
+static void rcutorture_shutdown_absorb(const char *title)
+{
+	if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
+		pr_notice(
+		       "rcutorture thread %s parking due to system shutdown\n",
+		       title);
+		schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
+	}
+}
+
+/*
+ * 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);
+}
+
+struct rcu_random_state {
+	unsigned long rrs_state;
+	long rrs_count;
+};
+
+#define RCU_RANDOM_MULT 39916801  /* prime */
+#define RCU_RANDOM_ADD	479001701 /* prime */
+#define RCU_RANDOM_REFRESH 10000
+
+#define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
+
+/*
+ * Crude but fast random-number generator.  Uses a linear congruential
+ * generator, with occasional help from cpu_clock().
+ */
+static unsigned long
+rcu_random(struct rcu_random_state *rrsp)
+{
+	if (--rrsp->rrs_count < 0) {
+		rrsp->rrs_state += (unsigned long)local_clock();
+		rrsp->rrs_count = RCU_RANDOM_REFRESH;
+	}
+	rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
+	return swahw32(rrsp->rrs_state);
+}
+
+static void
+rcu_stutter_wait(const char *title)
+{
+	while (stutter_pause_test || !rcutorture_runnable) {
+		if (rcutorture_runnable)
+			schedule_timeout_interruptible(1);
+		else
+			schedule_timeout_interruptible(round_jiffies_relative(HZ));
+		rcutorture_shutdown_absorb(title);
+	}
+}
+
+/*
+ * Operations vector for selecting different types of tests.
+ */
+
+struct rcu_torture_ops {
+	void (*init)(void);
+	int (*readlock)(void);
+	void (*read_delay)(struct rcu_random_state *rrsp);
+	void (*readunlock)(int idx);
+	int (*completed)(void);
+	void (*deferred_free)(struct rcu_torture *p);
+	void (*sync)(void);
+	void (*exp_sync)(void);
+	void (*call)(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
+	void (*cb_barrier)(void);
+	void (*fqs)(void);
+	int (*stats)(char *page);
+	int irq_capable;
+	int can_boost;
+	const char *name;
+};
+
+static struct rcu_torture_ops *cur_ops;
+
+/*
+ * Definitions for rcu torture testing.
+ */
+
+static int rcu_torture_read_lock(void) __acquires(RCU)
+{
+	rcu_read_lock();
+	return 0;
+}
+
+static void rcu_read_delay(struct rcu_random_state *rrsp)
+{
+	const unsigned long shortdelay_us = 200;
+	const unsigned long longdelay_ms = 50;
+
+	/* 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 (!(rcu_random(rrsp) % (nrealreaders * 2000 * longdelay_ms)))
+		mdelay(longdelay_ms);
+	if (!(rcu_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
+		udelay(shortdelay_us);
+#ifdef CONFIG_PREEMPT
+	if (!preempt_count() && !(rcu_random(rrsp) % (nrealreaders * 20000)))
+		preempt_schedule();  /* No QS if preempt_disable() in effect */
+#endif
+}
+
+static void rcu_torture_read_unlock(int idx) __releases(RCU)
+{
+	rcu_read_unlock();
+}
+
+static int rcu_torture_completed(void)
+{
+	return rcu_batches_completed();
+}
+
+static void
+rcu_torture_cb(struct rcu_head *p)
+{
+	int i;
+	struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
+
+	if (fullstop != FULLSTOP_DONTSTOP) {
+		/* Test is ending, just drop callbacks on the floor. */
+		/* The next initialization will pick up the pieces. */
+		return;
+	}
+	i = rp->rtort_pipe_count;
+	if (i > RCU_TORTURE_PIPE_LEN)
+		i = RCU_TORTURE_PIPE_LEN;
+	atomic_inc(&rcu_torture_wcount[i]);
+	if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+		rp->rtort_mbtest = 0;
+		rcu_torture_free(rp);
+	} else {
+		cur_ops->deferred_free(rp);
+	}
+}
+
+static int rcu_no_completed(void)
+{
+	return 0;
+}
+
+static void rcu_torture_deferred_free(struct rcu_torture *p)
+{
+	call_rcu(&p->rtort_rcu, rcu_torture_cb);
+}
+
+static void rcu_sync_torture_init(void)
+{
+	INIT_LIST_HEAD(&rcu_torture_removed);
+}
+
+static struct rcu_torture_ops rcu_ops = {
+	.init		= rcu_sync_torture_init,
+	.readlock	= rcu_torture_read_lock,
+	.read_delay	= rcu_read_delay,
+	.readunlock	= rcu_torture_read_unlock,
+	.completed	= rcu_torture_completed,
+	.deferred_free	= rcu_torture_deferred_free,
+	.sync		= synchronize_rcu,
+	.exp_sync	= synchronize_rcu_expedited,
+	.call		= call_rcu,
+	.cb_barrier	= rcu_barrier,
+	.fqs		= rcu_force_quiescent_state,
+	.stats		= NULL,
+	.irq_capable	= 1,
+	.can_boost	= rcu_can_boost(),
+	.name		= "rcu"
+};
+
+/*
+ * Definitions for rcu_bh torture testing.
+ */
+
+static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
+{
+	rcu_read_lock_bh();
+	return 0;
+}
+
+static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
+{
+	rcu_read_unlock_bh();
+}
+
+static int rcu_bh_torture_completed(void)
+{
+	return rcu_batches_completed_bh();
+}
+
+static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
+{
+	call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
+}
+
+static struct rcu_torture_ops rcu_bh_ops = {
+	.init		= rcu_sync_torture_init,
+	.readlock	= rcu_bh_torture_read_lock,
+	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
+	.readunlock	= rcu_bh_torture_read_unlock,
+	.completed	= rcu_bh_torture_completed,
+	.deferred_free	= rcu_bh_torture_deferred_free,
+	.sync		= synchronize_rcu_bh,
+	.exp_sync	= synchronize_rcu_bh_expedited,
+	.call		= call_rcu_bh,
+	.cb_barrier	= rcu_barrier_bh,
+	.fqs		= rcu_bh_force_quiescent_state,
+	.stats		= NULL,
+	.irq_capable	= 1,
+	.name		= "rcu_bh"
+};
+
+/*
+ * Definitions for srcu torture testing.
+ */
+
+DEFINE_STATIC_SRCU(srcu_ctl);
+
+static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
+{
+	return srcu_read_lock(&srcu_ctl);
+}
+
+static void srcu_read_delay(struct rcu_random_state *rrsp)
+{
+	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 = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
+	if (!delay)
+		schedule_timeout_interruptible(longdelay);
+	else
+		rcu_read_delay(rrsp);
+}
+
+static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
+{
+	srcu_read_unlock(&srcu_ctl, idx);
+}
+
+static int srcu_torture_completed(void)
+{
+	return srcu_batches_completed(&srcu_ctl);
+}
+
+static void srcu_torture_deferred_free(struct rcu_torture *rp)
+{
+	call_srcu(&srcu_ctl, &rp->rtort_rcu, rcu_torture_cb);
+}
+
+static void srcu_torture_synchronize(void)
+{
+	synchronize_srcu(&srcu_ctl);
+}
+
+static void srcu_torture_call(struct rcu_head *head,
+			      void (*func)(struct rcu_head *head))
+{
+	call_srcu(&srcu_ctl, head, func);
+}
+
+static void srcu_torture_barrier(void)
+{
+	srcu_barrier(&srcu_ctl);
+}
+
+static int srcu_torture_stats(char *page)
+{
+	int cnt = 0;
+	int cpu;
+	int idx = srcu_ctl.completed & 0x1;
+
+	cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
+		       torture_type, TORTURE_FLAG, idx);
+	for_each_possible_cpu(cpu) {
+		cnt += sprintf(&page[cnt], " %d(%lu,%lu)", cpu,
+			       per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
+			       per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
+	}
+	cnt += sprintf(&page[cnt], "\n");
+	return cnt;
+}
+
+static void srcu_torture_synchronize_expedited(void)
+{
+	synchronize_srcu_expedited(&srcu_ctl);
+}
+
+static struct rcu_torture_ops srcu_ops = {
+	.init		= rcu_sync_torture_init,
+	.readlock	= srcu_torture_read_lock,
+	.read_delay	= srcu_read_delay,
+	.readunlock	= srcu_torture_read_unlock,
+	.completed	= 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,
+	.name		= "srcu"
+};
+
+/*
+ * Definitions for sched torture testing.
+ */
+
+static int sched_torture_read_lock(void)
+{
+	preempt_disable();
+	return 0;
+}
+
+static void sched_torture_read_unlock(int idx)
+{
+	preempt_enable();
+}
+
+static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
+{
+	call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
+}
+
+static struct rcu_torture_ops sched_ops = {
+	.init		= rcu_sync_torture_init,
+	.readlock	= sched_torture_read_lock,
+	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
+	.readunlock	= sched_torture_read_unlock,
+	.completed	= rcu_no_completed,
+	.deferred_free	= rcu_sched_torture_deferred_free,
+	.sync		= synchronize_sched,
+	.exp_sync	= synchronize_sched_expedited,
+	.call		= call_rcu_sched,
+	.cb_barrier	= rcu_barrier_sched,
+	.fqs		= rcu_sched_force_quiescent_state,
+	.stats		= NULL,
+	.irq_capable	= 1,
+	.name		= "sched"
+};
+
+/*
+ * RCU torture priority-boost testing.  Runs one real-time thread per
+ * CPU for moderate bursts, repeatedly registering RCU callbacks and
+ * spinning waiting for them to be invoked.  If a given callback takes
+ * too long to be invoked, we assume that priority inversion has occurred.
+ */
+
+struct rcu_boost_inflight {
+	struct rcu_head rcu;
+	int inflight;
+};
+
+static void rcu_torture_boost_cb(struct rcu_head *head)
+{
+	struct rcu_boost_inflight *rbip =
+		container_of(head, struct rcu_boost_inflight, rcu);
+
+	smp_mb(); /* Ensure RCU-core accesses precede clearing ->inflight */
+	rbip->inflight = 0;
+}
+
+static int rcu_torture_boost(void *arg)
+{
+	unsigned long call_rcu_time;
+	unsigned long endtime;
+	unsigned long oldstarttime;
+	struct rcu_boost_inflight rbi = { .inflight = 0 };
+	struct sched_param sp;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_boost started");
+
+	/* Set real-time priority. */
+	sp.sched_priority = 1;
+	if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) {
+		VERBOSE_PRINTK_STRING("rcu_torture_boost RT prio failed!");
+		n_rcu_torture_boost_rterror++;
+	}
+
+	init_rcu_head_on_stack(&rbi.rcu);
+	/* Each pass through the following loop does one boost-test cycle. */
+	do {
+		/* Wait for the next test interval. */
+		oldstarttime = boost_starttime;
+		while (ULONG_CMP_LT(jiffies, oldstarttime)) {
+			schedule_timeout_interruptible(oldstarttime - jiffies);
+			rcu_stutter_wait("rcu_torture_boost");
+			if (kthread_should_stop() ||
+			    fullstop != FULLSTOP_DONTSTOP)
+				goto checkwait;
+		}
+
+		/* Do one boost-test interval. */
+		endtime = oldstarttime + test_boost_duration * HZ;
+		call_rcu_time = jiffies;
+		while (ULONG_CMP_LT(jiffies, endtime)) {
+			/* If we don't have a callback in flight, post one. */
+			if (!rbi.inflight) {
+				smp_mb(); /* RCU core before ->inflight = 1. */
+				rbi.inflight = 1;
+				call_rcu(&rbi.rcu, rcu_torture_boost_cb);
+				if (jiffies - call_rcu_time >
+					 test_boost_duration * HZ - HZ / 2) {
+					VERBOSE_PRINTK_STRING("rcu_torture_boost boosting failed");
+					n_rcu_torture_boost_failure++;
+				}
+				call_rcu_time = jiffies;
+			}
+			cond_resched();
+			rcu_stutter_wait("rcu_torture_boost");
+			if (kthread_should_stop() ||
+			    fullstop != FULLSTOP_DONTSTOP)
+				goto checkwait;
+		}
+
+		/*
+		 * 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 == boost_starttime &&
+		       !kthread_should_stop()) {
+			if (mutex_trylock(&boost_mutex)) {
+				boost_starttime = jiffies +
+						  test_boost_interval * HZ;
+				n_rcu_torture_boosts++;
+				mutex_unlock(&boost_mutex);
+				break;
+			}
+			schedule_timeout_uninterruptible(1);
+		}
+
+		/* Go do the stutter. */
+checkwait:	rcu_stutter_wait("rcu_torture_boost");
+	} while (!kthread_should_stop() && fullstop  == FULLSTOP_DONTSTOP);
+
+	/* Clean up and exit. */
+	VERBOSE_PRINTK_STRING("rcu_torture_boost task stopping");
+	rcutorture_shutdown_absorb("rcu_torture_boost");
+	while (!kthread_should_stop() || rbi.inflight)
+		schedule_timeout_uninterruptible(1);
+	smp_mb(); /* order accesses to ->inflight before stack-frame death. */
+	destroy_rcu_head_on_stack(&rbi.rcu);
+	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;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_fqs task started");
+	do {
+		fqs_resume_time = jiffies + fqs_stutter * HZ;
+		while (ULONG_CMP_LT(jiffies, fqs_resume_time) &&
+		       !kthread_should_stop()) {
+			schedule_timeout_interruptible(1);
+		}
+		fqs_burst_remaining = fqs_duration;
+		while (fqs_burst_remaining > 0 &&
+		       !kthread_should_stop()) {
+			cur_ops->fqs();
+			udelay(fqs_holdoff);
+			fqs_burst_remaining -= fqs_holdoff;
+		}
+		rcu_stutter_wait("rcu_torture_fqs");
+	} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
+	VERBOSE_PRINTK_STRING("rcu_torture_fqs task stopping");
+	rcutorture_shutdown_absorb("rcu_torture_fqs");
+	while (!kthread_should_stop())
+		schedule_timeout_uninterruptible(1);
+	return 0;
+}
+
+/*
+ * 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 exp;
+	int i;
+	struct rcu_torture *rp;
+	struct rcu_torture *rp1;
+	struct rcu_torture *old_rp;
+	static DEFINE_RCU_RANDOM(rand);
+
+	VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
+	set_user_nice(current, 19);
+
+	do {
+		schedule_timeout_uninterruptible(1);
+		rp = rcu_torture_alloc();
+		if (rp == NULL)
+			continue;
+		rp->rtort_pipe_count = 0;
+		udelay(rcu_random(&rand) & 0x3ff);
+		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]);
+			old_rp->rtort_pipe_count++;
+			if (gp_normal == gp_exp)
+				exp = !!(rcu_random(&rand) & 0x80);
+			else
+				exp = gp_exp;
+			if (!exp) {
+				cur_ops->deferred_free(old_rp);
+			} else {
+				cur_ops->exp_sync();
+				list_add(&old_rp->rtort_free,
+					 &rcu_torture_removed);
+				list_for_each_entry_safe(rp, rp1,
+							 &rcu_torture_removed,
+							 rtort_free) {
+					i = rp->rtort_pipe_count;
+					if (i > RCU_TORTURE_PIPE_LEN)
+						i = RCU_TORTURE_PIPE_LEN;
+					atomic_inc(&rcu_torture_wcount[i]);
+					if (++rp->rtort_pipe_count >=
+					    RCU_TORTURE_PIPE_LEN) {
+						rp->rtort_mbtest = 0;
+						list_del(&rp->rtort_free);
+						rcu_torture_free(rp);
+					}
+				 }
+			}
+		}
+		rcutorture_record_progress(++rcu_torture_current_version);
+		rcu_stutter_wait("rcu_torture_writer");
+	} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
+	VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
+	rcutorture_shutdown_absorb("rcu_torture_writer");
+	while (!kthread_should_stop())
+		schedule_timeout_uninterruptible(1);
+	return 0;
+}
+
+/*
+ * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
+ * delay between calls.
+ */
+static int
+rcu_torture_fakewriter(void *arg)
+{
+	DEFINE_RCU_RANDOM(rand);
+
+	VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
+	set_user_nice(current, 19);
+
+	do {
+		schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
+		udelay(rcu_random(&rand) & 0x3ff);
+		if (cur_ops->cb_barrier != NULL &&
+		    rcu_random(&rand) % (nfakewriters * 8) == 0) {
+			cur_ops->cb_barrier();
+		} else if (gp_normal == gp_exp) {
+			if (rcu_random(&rand) & 0x80)
+				cur_ops->sync();
+			else
+				cur_ops->exp_sync();
+		} else if (gp_normal) {
+			cur_ops->sync();
+		} else {
+			cur_ops->exp_sync();
+		}
+		rcu_stutter_wait("rcu_torture_fakewriter");
+	} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
+
+	VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
+	rcutorture_shutdown_absorb("rcu_torture_fakewriter");
+	while (!kthread_should_stop())
+		schedule_timeout_uninterruptible(1);
+	return 0;
+}
+
+void rcutorture_trace_dump(void)
+{
+	static atomic_t beenhere = ATOMIC_INIT(0);
+
+	if (atomic_read(&beenhere))
+		return;
+	if (atomic_xchg(&beenhere, 1) != 0)
+		return;
+	ftrace_dump(DUMP_ALL);
+}
+
+/*
+ * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
+ * incrementing the corresponding element of the pipeline array.  The
+ * counter in the element should never be greater than 1, otherwise, the
+ * RCU implementation is broken.
+ */
+static void rcu_torture_timer(unsigned long unused)
+{
+	int idx;
+	int completed;
+	int completed_end;
+	static DEFINE_RCU_RANDOM(rand);
+	static DEFINE_SPINLOCK(rand_lock);
+	struct rcu_torture *p;
+	int pipe_count;
+	unsigned long long ts;
+
+	idx = cur_ops->readlock();
+	completed = cur_ops->completed();
+	ts = rcu_trace_clock_local();
+	p = rcu_dereference_check(rcu_torture_current,
+				  rcu_read_lock_bh_held() ||
+				  rcu_read_lock_sched_held() ||
+				  srcu_read_lock_held(&srcu_ctl));
+	if (p == NULL) {
+		/* Leave because rcu_torture_writer is not yet underway */
+		cur_ops->readunlock(idx);
+		return;
+	}
+	if (p->rtort_mbtest == 0)
+		atomic_inc(&n_rcu_torture_mberror);
+	spin_lock(&rand_lock);
+	cur_ops->read_delay(&rand);
+	n_rcu_torture_timers++;
+	spin_unlock(&rand_lock);
+	preempt_disable();
+	pipe_count = p->rtort_pipe_count;
+	if (pipe_count > RCU_TORTURE_PIPE_LEN) {
+		/* Should not happen, but... */
+		pipe_count = RCU_TORTURE_PIPE_LEN;
+	}
+	completed_end = cur_ops->completed();
+	if (pipe_count > 1) {
+		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts,
+					  completed, completed_end);
+		rcutorture_trace_dump();
+	}
+	__this_cpu_inc(rcu_torture_count[pipe_count]);
+	completed = completed_end - completed;
+	if (completed > RCU_TORTURE_PIPE_LEN) {
+		/* Should not happen, but... */
+		completed = RCU_TORTURE_PIPE_LEN;
+	}
+	__this_cpu_inc(rcu_torture_batch[completed]);
+	preempt_enable();
+	cur_ops->readunlock(idx);
+}
+
+/*
+ * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
+ * incrementing the corresponding element of the pipeline array.  The
+ * counter in the element should never be greater than 1, otherwise, the
+ * RCU implementation is broken.
+ */
+static int
+rcu_torture_reader(void *arg)
+{
+	int completed;
+	int completed_end;
+	int idx;
+	DEFINE_RCU_RANDOM(rand);
+	struct rcu_torture *p;
+	int pipe_count;
+	struct timer_list t;
+	unsigned long long ts;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
+	set_user_nice(current, 19);
+	if (irqreader && cur_ops->irq_capable)
+		setup_timer_on_stack(&t, rcu_torture_timer, 0);
+
+	do {
+		if (irqreader && cur_ops->irq_capable) {
+			if (!timer_pending(&t))
+				mod_timer(&t, jiffies + 1);
+		}
+		idx = cur_ops->readlock();
+		completed = cur_ops->completed();
+		ts = rcu_trace_clock_local();
+		p = rcu_dereference_check(rcu_torture_current,
+					  rcu_read_lock_bh_held() ||
+					  rcu_read_lock_sched_held() ||
+					  srcu_read_lock_held(&srcu_ctl));
+		if (p == NULL) {
+			/* Wait for rcu_torture_writer to get underway */
+			cur_ops->readunlock(idx);
+			schedule_timeout_interruptible(HZ);
+			continue;
+		}
+		if (p->rtort_mbtest == 0)
+			atomic_inc(&n_rcu_torture_mberror);
+		cur_ops->read_delay(&rand);
+		preempt_disable();
+		pipe_count = p->rtort_pipe_count;
+		if (pipe_count > RCU_TORTURE_PIPE_LEN) {
+			/* Should not happen, but... */
+			pipe_count = RCU_TORTURE_PIPE_LEN;
+		}
+		completed_end = cur_ops->completed();
+		if (pipe_count > 1) {
+			do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
+						  ts, completed, completed_end);
+			rcutorture_trace_dump();
+		}
+		__this_cpu_inc(rcu_torture_count[pipe_count]);
+		completed = completed_end - completed;
+		if (completed > RCU_TORTURE_PIPE_LEN) {
+			/* Should not happen, but... */
+			completed = RCU_TORTURE_PIPE_LEN;
+		}
+		__this_cpu_inc(rcu_torture_batch[completed]);
+		preempt_enable();
+		cur_ops->readunlock(idx);
+		schedule();
+		rcu_stutter_wait("rcu_torture_reader");
+	} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
+	VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
+	rcutorture_shutdown_absorb("rcu_torture_reader");
+	if (irqreader && cur_ops->irq_capable)
+		del_timer_sync(&t);
+	while (!kthread_should_stop())
+		schedule_timeout_uninterruptible(1);
+	return 0;
+}
+
+/*
+ * Create an RCU-torture statistics message in the specified buffer.
+ */
+static int
+rcu_torture_printk(char *page)
+{
+	int cnt = 0;
+	int cpu;
+	int i;
+	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+
+	for_each_possible_cpu(cpu) {
+		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+			pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
+			batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
+		}
+	}
+	for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
+		if (pipesummary[i] != 0)
+			break;
+	}
+	cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
+	cnt += sprintf(&page[cnt],
+		       "rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
+		       rcu_torture_current,
+		       rcu_torture_current_version,
+		       list_empty(&rcu_torture_freelist),
+		       atomic_read(&n_rcu_torture_alloc),
+		       atomic_read(&n_rcu_torture_alloc_fail),
+		       atomic_read(&n_rcu_torture_free));
+	cnt += sprintf(&page[cnt], "rtmbe: %d rtbke: %ld rtbre: %ld ",
+		       atomic_read(&n_rcu_torture_mberror),
+		       n_rcu_torture_boost_ktrerror,
+		       n_rcu_torture_boost_rterror);
+	cnt += sprintf(&page[cnt], "rtbf: %ld rtb: %ld nt: %ld ",
+		       n_rcu_torture_boost_failure,
+		       n_rcu_torture_boosts,
+		       n_rcu_torture_timers);
+	cnt += sprintf(&page[cnt],
+		       "onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
+		       n_online_successes, n_online_attempts,
+		       n_offline_successes, n_offline_attempts,
+		       min_online, max_online,
+		       min_offline, max_offline,
+		       sum_online, sum_offline, HZ);
+	cnt += sprintf(&page[cnt], "barrier: %ld/%ld:%ld",
+		       n_barrier_successes,
+		       n_barrier_attempts,
+		       n_rcu_torture_barrier_error);
+	cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
+	if (atomic_read(&n_rcu_torture_mberror) != 0 ||
+	    n_rcu_torture_barrier_error != 0 ||
+	    n_rcu_torture_boost_ktrerror != 0 ||
+	    n_rcu_torture_boost_rterror != 0 ||
+	    n_rcu_torture_boost_failure != 0 ||
+	    i > 1) {
+		cnt += sprintf(&page[cnt], "!!! ");
+		atomic_inc(&n_rcu_torture_error);
+		WARN_ON_ONCE(1);
+	}
+	cnt += sprintf(&page[cnt], "Reader Pipe: ");
+	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
+		cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
+	cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
+	cnt += sprintf(&page[cnt], "Reader Batch: ");
+	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
+		cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
+	cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
+	cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
+	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+		cnt += sprintf(&page[cnt], " %d",
+			       atomic_read(&rcu_torture_wcount[i]));
+	}
+	cnt += sprintf(&page[cnt], "\n");
+	if (cur_ops->stats)
+		cnt += cur_ops->stats(&page[cnt]);
+	return cnt;
+}
+
+/*
+ * Print torture statistics.  Caller must ensure that there is only
+ * one call to this function at a given time!!!  This is normally
+ * accomplished by relying on the module system to only have one copy
+ * of the module loaded, and then by giving the rcu_torture_stats
+ * kthread full control (or the init/cleanup functions when rcu_torture_stats
+ * thread is not running).
+ */
+static void
+rcu_torture_stats_print(void)
+{
+	int cnt;
+
+	cnt = rcu_torture_printk(printk_buf);
+	pr_alert("%s", printk_buf);
+}
+
+/*
+ * Periodically prints torture statistics, if periodic statistics printing
+ * was specified via the stat_interval module parameter.
+ *
+ * No need to worry about fullstop here, since this one doesn't reference
+ * volatile state or register callbacks.
+ */
+static int
+rcu_torture_stats(void *arg)
+{
+	VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
+	do {
+		schedule_timeout_interruptible(stat_interval * HZ);
+		rcu_torture_stats_print();
+		rcutorture_shutdown_absorb("rcu_torture_stats");
+	} while (!kthread_should_stop());
+	VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
+	return 0;
+}
+
+static int rcu_idle_cpu;	/* Force all torture tasks off this CPU */
+
+/* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
+ * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
+ */
+static void rcu_torture_shuffle_tasks(void)
+{
+	int i;
+
+	cpumask_setall(shuffle_tmp_mask);
+	get_online_cpus();
+
+	/* No point in shuffling if there is only one online CPU (ex: UP) */
+	if (num_online_cpus() == 1) {
+		put_online_cpus();
+		return;
+	}
+
+	if (rcu_idle_cpu != -1)
+		cpumask_clear_cpu(rcu_idle_cpu, shuffle_tmp_mask);
+
+	set_cpus_allowed_ptr(current, shuffle_tmp_mask);
+
+	if (reader_tasks) {
+		for (i = 0; i < nrealreaders; i++)
+			if (reader_tasks[i])
+				set_cpus_allowed_ptr(reader_tasks[i],
+						     shuffle_tmp_mask);
+	}
+	if (fakewriter_tasks) {
+		for (i = 0; i < nfakewriters; i++)
+			if (fakewriter_tasks[i])
+				set_cpus_allowed_ptr(fakewriter_tasks[i],
+						     shuffle_tmp_mask);
+	}
+	if (writer_task)
+		set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
+	if (stats_task)
+		set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask);
+	if (stutter_task)
+		set_cpus_allowed_ptr(stutter_task, shuffle_tmp_mask);
+	if (fqs_task)
+		set_cpus_allowed_ptr(fqs_task, shuffle_tmp_mask);
+	if (shutdown_task)
+		set_cpus_allowed_ptr(shutdown_task, shuffle_tmp_mask);
+#ifdef CONFIG_HOTPLUG_CPU
+	if (onoff_task)
+		set_cpus_allowed_ptr(onoff_task, shuffle_tmp_mask);
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+	if (stall_task)
+		set_cpus_allowed_ptr(stall_task, shuffle_tmp_mask);
+	if (barrier_cbs_tasks)
+		for (i = 0; i < n_barrier_cbs; i++)
+			if (barrier_cbs_tasks[i])
+				set_cpus_allowed_ptr(barrier_cbs_tasks[i],
+						     shuffle_tmp_mask);
+	if (barrier_task)
+		set_cpus_allowed_ptr(barrier_task, shuffle_tmp_mask);
+
+	if (rcu_idle_cpu == -1)
+		rcu_idle_cpu = num_online_cpus() - 1;
+	else
+		rcu_idle_cpu--;
+
+	put_online_cpus();
+}
+
+/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
+ * system to become idle at a time and cut off its timer ticks. This is meant
+ * to test the support for such tickless idle CPU in RCU.
+ */
+static int
+rcu_torture_shuffle(void *arg)
+{
+	VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
+	do {
+		schedule_timeout_interruptible(shuffle_interval * HZ);
+		rcu_torture_shuffle_tasks();
+		rcutorture_shutdown_absorb("rcu_torture_shuffle");
+	} while (!kthread_should_stop());
+	VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
+	return 0;
+}
+
+/* Cause the rcutorture test to "stutter", starting and stopping all
+ * threads periodically.
+ */
+static int
+rcu_torture_stutter(void *arg)
+{
+	VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
+	do {
+		schedule_timeout_interruptible(stutter * HZ);
+		stutter_pause_test = 1;
+		if (!kthread_should_stop())
+			schedule_timeout_interruptible(stutter * HZ);
+		stutter_pause_test = 0;
+		rcutorture_shutdown_absorb("rcu_torture_stutter");
+	} while (!kthread_should_stop());
+	VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
+	return 0;
+}
+
+static inline void
+rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
+{
+	pr_alert("%s" TORTURE_FLAG
+		 "--- %s: nreaders=%d nfakewriters=%d "
+		 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
+		 "shuffle_interval=%d stutter=%d irqreader=%d "
+		 "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
+		 "test_boost=%d/%d test_boost_interval=%d "
+		 "test_boost_duration=%d shutdown_secs=%d "
+		 "stall_cpu=%d stall_cpu_holdoff=%d "
+		 "n_barrier_cbs=%d "
+		 "onoff_interval=%d onoff_holdoff=%d\n",
+		 torture_type, tag, nrealreaders, nfakewriters,
+		 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
+		 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
+		 test_boost, cur_ops->can_boost,
+		 test_boost_interval, test_boost_duration, shutdown_secs,
+		 stall_cpu, stall_cpu_holdoff,
+		 n_barrier_cbs,
+		 onoff_interval, onoff_holdoff);
+}
+
+static struct notifier_block rcutorture_shutdown_nb = {
+	.notifier_call = rcutorture_shutdown_notify,
+};
+
+static void rcutorture_booster_cleanup(int cpu)
+{
+	struct task_struct *t;
+
+	if (boost_tasks[cpu] == NULL)
+		return;
+	mutex_lock(&boost_mutex);
+	VERBOSE_PRINTK_STRING("Stopping rcu_torture_boost task");
+	t = boost_tasks[cpu];
+	boost_tasks[cpu] = NULL;
+	mutex_unlock(&boost_mutex);
+
+	/* This must be outside of the mutex, otherwise deadlock! */
+	kthread_stop(t);
+	boost_tasks[cpu] = NULL;
+}
+
+static int rcutorture_booster_init(int cpu)
+{
+	int retval;
+
+	if (boost_tasks[cpu] != NULL)
+		return 0;  /* Already created, nothing more to do. */
+
+	/* Don't allow time recalculation while creating a new task. */
+	mutex_lock(&boost_mutex);
+	VERBOSE_PRINTK_STRING("Creating rcu_torture_boost task");
+	boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL,
+						  cpu_to_node(cpu),
+						  "rcu_torture_boost");
+	if (IS_ERR(boost_tasks[cpu])) {
+		retval = PTR_ERR(boost_tasks[cpu]);
+		VERBOSE_PRINTK_STRING("rcu_torture_boost task create failed");
+		n_rcu_torture_boost_ktrerror++;
+		boost_tasks[cpu] = NULL;
+		mutex_unlock(&boost_mutex);
+		return retval;
+	}
+	kthread_bind(boost_tasks[cpu], cpu);
+	wake_up_process(boost_tasks[cpu]);
+	mutex_unlock(&boost_mutex);
+	return 0;
+}
+
+/*
+ * Cause the rcutorture test to shutdown the system after the test has
+ * run for the time specified by the shutdown_secs module parameter.
+ */
+static int
+rcu_torture_shutdown(void *arg)
+{
+	long delta;
+	unsigned long jiffies_snap;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_shutdown task started");
+	jiffies_snap = ACCESS_ONCE(jiffies);
+	while (ULONG_CMP_LT(jiffies_snap, shutdown_time) &&
+	       !kthread_should_stop()) {
+		delta = shutdown_time - jiffies_snap;
+		if (verbose)
+			pr_alert("%s" TORTURE_FLAG
+				 "rcu_torture_shutdown task: %lu jiffies remaining\n",
+				 torture_type, delta);
+		schedule_timeout_interruptible(delta);
+		jiffies_snap = ACCESS_ONCE(jiffies);
+	}
+	if (kthread_should_stop()) {
+		VERBOSE_PRINTK_STRING("rcu_torture_shutdown task stopping");
+		return 0;
+	}
+
+	/* OK, shut down the system. */
+
+	VERBOSE_PRINTK_STRING("rcu_torture_shutdown task shutting down system");
+	shutdown_task = NULL;	/* Avoid self-kill deadlock. */
+	rcu_torture_cleanup();	/* Get the success/failure message. */
+	kernel_power_off();	/* Shut down the system. */
+	return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Execute random CPU-hotplug operations at the interval specified
+ * by the onoff_interval.
+ */
+static int
+rcu_torture_onoff(void *arg)
+{
+	int cpu;
+	unsigned long delta;
+	int maxcpu = -1;
+	DEFINE_RCU_RANDOM(rand);
+	int ret;
+	unsigned long starttime;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_onoff task started");
+	for_each_online_cpu(cpu)
+		maxcpu = cpu;
+	WARN_ON(maxcpu < 0);
+	if (onoff_holdoff > 0) {
+		VERBOSE_PRINTK_STRING("rcu_torture_onoff begin holdoff");
+		schedule_timeout_interruptible(onoff_holdoff * HZ);
+		VERBOSE_PRINTK_STRING("rcu_torture_onoff end holdoff");
+	}
+	while (!kthread_should_stop()) {
+		cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1);
+		if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {
+			if (verbose)
+				pr_alert("%s" TORTURE_FLAG
+					 "rcu_torture_onoff task: offlining %d\n",
+					 torture_type, cpu);
+			starttime = jiffies;
+			n_offline_attempts++;
+			ret = cpu_down(cpu);
+			if (ret) {
+				if (verbose)
+					pr_alert("%s" TORTURE_FLAG
+						 "rcu_torture_onoff task: offline %d failed: errno %d\n",
+						 torture_type, cpu, ret);
+			} else {
+				if (verbose)
+					pr_alert("%s" TORTURE_FLAG
+						 "rcu_torture_onoff task: offlined %d\n",
+						 torture_type, cpu);
+				n_offline_successes++;
+				delta = jiffies - starttime;
+				sum_offline += delta;
+				if (min_offline < 0) {
+					min_offline = delta;
+					max_offline = delta;
+				}
+				if (min_offline > delta)
+					min_offline = delta;
+				if (max_offline < delta)
+					max_offline = delta;
+			}
+		} else if (cpu_is_hotpluggable(cpu)) {
+			if (verbose)
+				pr_alert("%s" TORTURE_FLAG
+					 "rcu_torture_onoff task: onlining %d\n",
+					 torture_type, cpu);
+			starttime = jiffies;
+			n_online_attempts++;
+			ret = cpu_up(cpu);
+			if (ret) {
+				if (verbose)
+					pr_alert("%s" TORTURE_FLAG
+						 "rcu_torture_onoff task: online %d failed: errno %d\n",
+						 torture_type, cpu, ret);
+			} else {
+				if (verbose)
+					pr_alert("%s" TORTURE_FLAG
+						 "rcu_torture_onoff task: onlined %d\n",
+						 torture_type, cpu);
+				n_online_successes++;
+				delta = jiffies - starttime;
+				sum_online += delta;
+				if (min_online < 0) {
+					min_online = delta;
+					max_online = delta;
+				}
+				if (min_online > delta)
+					min_online = delta;
+				if (max_online < delta)
+					max_online = delta;
+			}
+		}
+		schedule_timeout_interruptible(onoff_interval * HZ);
+	}
+	VERBOSE_PRINTK_STRING("rcu_torture_onoff task stopping");
+	return 0;
+}
+
+static int
+rcu_torture_onoff_init(void)
+{
+	int ret;
+
+	if (onoff_interval <= 0)
+		return 0;
+	onoff_task = kthread_run(rcu_torture_onoff, NULL, "rcu_torture_onoff");
+	if (IS_ERR(onoff_task)) {
+		ret = PTR_ERR(onoff_task);
+		onoff_task = NULL;
+		return ret;
+	}
+	return 0;
+}
+
+static void rcu_torture_onoff_cleanup(void)
+{
+	if (onoff_task == NULL)
+		return;
+	VERBOSE_PRINTK_STRING("Stopping rcu_torture_onoff task");
+	kthread_stop(onoff_task);
+	onoff_task = NULL;
+}
+
+#else /* #ifdef CONFIG_HOTPLUG_CPU */
+
+static int
+rcu_torture_onoff_init(void)
+{
+	return 0;
+}
+
+static void rcu_torture_onoff_cleanup(void)
+{
+}
+
+#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
+
+/*
+ * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then
+ * induces a CPU stall for the time specified by stall_cpu.
+ */
+static int rcu_torture_stall(void *args)
+{
+	unsigned long stop_at;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_stall task started");
+	if (stall_cpu_holdoff > 0) {
+		VERBOSE_PRINTK_STRING("rcu_torture_stall begin holdoff");
+		schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
+		VERBOSE_PRINTK_STRING("rcu_torture_stall end holdoff");
+	}
+	if (!kthread_should_stop()) {
+		stop_at = get_seconds() + stall_cpu;
+		/* RCU CPU stall is expected behavior in following code. */
+		pr_alert("rcu_torture_stall start.\n");
+		rcu_read_lock();
+		preempt_disable();
+		while (ULONG_CMP_LT(get_seconds(), stop_at))
+			continue;  /* Induce RCU CPU stall warning. */
+		preempt_enable();
+		rcu_read_unlock();
+		pr_alert("rcu_torture_stall end.\n");
+	}
+	rcutorture_shutdown_absorb("rcu_torture_stall");
+	while (!kthread_should_stop())
+		schedule_timeout_interruptible(10 * HZ);
+	return 0;
+}
+
+/* Spawn CPU-stall kthread, if stall_cpu specified. */
+static int __init rcu_torture_stall_init(void)
+{
+	int ret;
+
+	if (stall_cpu <= 0)
+		return 0;
+	stall_task = kthread_run(rcu_torture_stall, NULL, "rcu_torture_stall");
+	if (IS_ERR(stall_task)) {
+		ret = PTR_ERR(stall_task);
+		stall_task = NULL;
+		return ret;
+	}
+	return 0;
+}
+
+/* Clean up after the CPU-stall kthread, if one was spawned. */
+static void rcu_torture_stall_cleanup(void)
+{
+	if (stall_task == NULL)
+		return;
+	VERBOSE_PRINTK_STRING("Stopping rcu_torture_stall_task.");
+	kthread_stop(stall_task);
+	stall_task = NULL;
+}
+
+/* Callback function for RCU barrier testing. */
+void rcu_torture_barrier_cbf(struct rcu_head *rcu)
+{
+	atomic_inc(&barrier_cbs_invoked);
+}
+
+/* kthread function to register callbacks used to test RCU barriers. */
+static int rcu_torture_barrier_cbs(void *arg)
+{
+	long myid = (long)arg;
+	bool lastphase = 0;
+	struct rcu_head rcu;
+
+	init_rcu_head_on_stack(&rcu);
+	VERBOSE_PRINTK_STRING("rcu_torture_barrier_cbs task started");
+	set_user_nice(current, 19);
+	do {
+		wait_event(barrier_cbs_wq[myid],
+			   barrier_phase != lastphase ||
+			   kthread_should_stop() ||
+			   fullstop != FULLSTOP_DONTSTOP);
+		lastphase = barrier_phase;
+		smp_mb(); /* ensure barrier_phase load before ->call(). */
+		if (kthread_should_stop() || fullstop != FULLSTOP_DONTSTOP)
+			break;
+		cur_ops->call(&rcu, rcu_torture_barrier_cbf);
+		if (atomic_dec_and_test(&barrier_cbs_count))
+			wake_up(&barrier_wq);
+	} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
+	VERBOSE_PRINTK_STRING("rcu_torture_barrier_cbs task stopping");
+	rcutorture_shutdown_absorb("rcu_torture_barrier_cbs");
+	while (!kthread_should_stop())
+		schedule_timeout_interruptible(1);
+	cur_ops->cb_barrier();
+	destroy_rcu_head_on_stack(&rcu);
+	return 0;
+}
+
+/* kthread function to drive and coordinate RCU barrier testing. */
+static int rcu_torture_barrier(void *arg)
+{
+	int i;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_barrier task starting");
+	do {
+		atomic_set(&barrier_cbs_invoked, 0);
+		atomic_set(&barrier_cbs_count, n_barrier_cbs);
+		smp_mb(); /* Ensure barrier_phase after prior assignments. */
+		barrier_phase = !barrier_phase;
+		for (i = 0; i < n_barrier_cbs; i++)
+			wake_up(&barrier_cbs_wq[i]);
+		wait_event(barrier_wq,
+			   atomic_read(&barrier_cbs_count) == 0 ||
+			   kthread_should_stop() ||
+			   fullstop != FULLSTOP_DONTSTOP);
+		if (kthread_should_stop() || fullstop != FULLSTOP_DONTSTOP)
+			break;
+		n_barrier_attempts++;
+		cur_ops->cb_barrier();
+		if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
+			n_rcu_torture_barrier_error++;
+			WARN_ON_ONCE(1);
+		}
+		n_barrier_successes++;
+		schedule_timeout_interruptible(HZ / 10);
+	} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
+	VERBOSE_PRINTK_STRING("rcu_torture_barrier task stopping");
+	rcutorture_shutdown_absorb("rcu_torture_barrier");
+	while (!kthread_should_stop())
+		schedule_timeout_interruptible(1);
+	return 0;
+}
+
+/* Initialize RCU barrier testing. */
+static int rcu_torture_barrier_init(void)
+{
+	int i;
+	int ret;
+
+	if (n_barrier_cbs == 0)
+		return 0;
+	if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
+		pr_alert("%s" TORTURE_FLAG
+			 " Call or barrier ops missing for %s,\n",
+			 torture_type, cur_ops->name);
+		pr_alert("%s" TORTURE_FLAG
+			 " RCU barrier testing omitted from run.\n",
+			 torture_type);
+		return 0;
+	}
+	atomic_set(&barrier_cbs_count, 0);
+	atomic_set(&barrier_cbs_invoked, 0);
+	barrier_cbs_tasks =
+		kzalloc(n_barrier_cbs * sizeof(barrier_cbs_tasks[0]),
+			GFP_KERNEL);
+	barrier_cbs_wq =
+		kzalloc(n_barrier_cbs * sizeof(barrier_cbs_wq[0]),
+			GFP_KERNEL);
+	if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
+		return -ENOMEM;
+	for (i = 0; i < n_barrier_cbs; i++) {
+		init_waitqueue_head(&barrier_cbs_wq[i]);
+		barrier_cbs_tasks[i] = kthread_run(rcu_torture_barrier_cbs,
+						   (void *)(long)i,
+						   "rcu_torture_barrier_cbs");
+		if (IS_ERR(barrier_cbs_tasks[i])) {
+			ret = PTR_ERR(barrier_cbs_tasks[i]);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create rcu_torture_barrier_cbs");
+			barrier_cbs_tasks[i] = NULL;
+			return ret;
+		}
+	}
+	barrier_task = kthread_run(rcu_torture_barrier, NULL,
+				   "rcu_torture_barrier");
+	if (IS_ERR(barrier_task)) {
+		ret = PTR_ERR(barrier_task);
+		VERBOSE_PRINTK_ERRSTRING("Failed to create rcu_torture_barrier");
+		barrier_task = NULL;
+	}
+	return 0;
+}
+
+/* Clean up after RCU barrier testing. */
+static void rcu_torture_barrier_cleanup(void)
+{
+	int i;
+
+	if (barrier_task != NULL) {
+		VERBOSE_PRINTK_STRING("Stopping rcu_torture_barrier task");
+		kthread_stop(barrier_task);
+		barrier_task = NULL;
+	}
+	if (barrier_cbs_tasks != NULL) {
+		for (i = 0; i < n_barrier_cbs; i++) {
+			if (barrier_cbs_tasks[i] != NULL) {
+				VERBOSE_PRINTK_STRING("Stopping rcu_torture_barrier_cbs task");
+				kthread_stop(barrier_cbs_tasks[i]);
+				barrier_cbs_tasks[i] = NULL;
+			}
+		}
+		kfree(barrier_cbs_tasks);
+		barrier_cbs_tasks = NULL;
+	}
+	if (barrier_cbs_wq != NULL) {
+		kfree(barrier_cbs_wq);
+		barrier_cbs_wq = NULL;
+	}
+}
+
+static int rcutorture_cpu_notify(struct notifier_block *self,
+				 unsigned long action, void *hcpu)
+{
+	long cpu = (long)hcpu;
+
+	switch (action) {
+	case CPU_ONLINE:
+	case CPU_DOWN_FAILED:
+		(void)rcutorture_booster_init(cpu);
+		break;
+	case CPU_DOWN_PREPARE:
+		rcutorture_booster_cleanup(cpu);
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block rcutorture_cpu_nb = {
+	.notifier_call = rcutorture_cpu_notify,
+};
+
+static void
+rcu_torture_cleanup(void)
+{
+	int i;
+
+	mutex_lock(&fullstop_mutex);
+	rcutorture_record_test_transition();
+	if (fullstop == FULLSTOP_SHUTDOWN) {
+		pr_warn(/* but going down anyway, so... */
+		       "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
+		mutex_unlock(&fullstop_mutex);
+		schedule_timeout_uninterruptible(10);
+		if (cur_ops->cb_barrier != NULL)
+			cur_ops->cb_barrier();
+		return;
+	}
+	fullstop = FULLSTOP_RMMOD;
+	mutex_unlock(&fullstop_mutex);
+	unregister_reboot_notifier(&rcutorture_shutdown_nb);
+	rcu_torture_barrier_cleanup();
+	rcu_torture_stall_cleanup();
+	if (stutter_task) {
+		VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
+		kthread_stop(stutter_task);
+	}
+	stutter_task = NULL;
+	if (shuffler_task) {
+		VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
+		kthread_stop(shuffler_task);
+		free_cpumask_var(shuffle_tmp_mask);
+	}
+	shuffler_task = NULL;
+
+	if (writer_task) {
+		VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
+		kthread_stop(writer_task);
+	}
+	writer_task = NULL;
+
+	if (reader_tasks) {
+		for (i = 0; i < nrealreaders; i++) {
+			if (reader_tasks[i]) {
+				VERBOSE_PRINTK_STRING(
+					"Stopping rcu_torture_reader task");
+				kthread_stop(reader_tasks[i]);
+			}
+			reader_tasks[i] = NULL;
+		}
+		kfree(reader_tasks);
+		reader_tasks = NULL;
+	}
+	rcu_torture_current = NULL;
+
+	if (fakewriter_tasks) {
+		for (i = 0; i < nfakewriters; i++) {
+			if (fakewriter_tasks[i]) {
+				VERBOSE_PRINTK_STRING(
+					"Stopping rcu_torture_fakewriter task");
+				kthread_stop(fakewriter_tasks[i]);
+			}
+			fakewriter_tasks[i] = NULL;
+		}
+		kfree(fakewriter_tasks);
+		fakewriter_tasks = NULL;
+	}
+
+	if (stats_task) {
+		VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
+		kthread_stop(stats_task);
+	}
+	stats_task = NULL;
+
+	if (fqs_task) {
+		VERBOSE_PRINTK_STRING("Stopping rcu_torture_fqs task");
+		kthread_stop(fqs_task);
+	}
+	fqs_task = NULL;
+	if ((test_boost == 1 && cur_ops->can_boost) ||
+	    test_boost == 2) {
+		unregister_cpu_notifier(&rcutorture_cpu_nb);
+		for_each_possible_cpu(i)
+			rcutorture_booster_cleanup(i);
+	}
+	if (shutdown_task != NULL) {
+		VERBOSE_PRINTK_STRING("Stopping rcu_torture_shutdown task");
+		kthread_stop(shutdown_task);
+	}
+	shutdown_task = NULL;
+	rcu_torture_onoff_cleanup();
+
+	/* Wait for all RCU callbacks to fire.  */
+
+	if (cur_ops->cb_barrier != NULL)
+		cur_ops->cb_barrier();
+
+	rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
+
+	if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error)
+		rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
+	else if (n_online_successes != n_online_attempts ||
+		 n_offline_successes != n_offline_attempts)
+		rcu_torture_print_module_parms(cur_ops,
+					       "End of test: RCU_HOTPLUG");
+	else
+		rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
+}
+
+#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
+static void rcu_torture_leak_cb(struct rcu_head *rhp)
+{
+}
+
+static void rcu_torture_err_cb(struct rcu_head *rhp)
+{
+	/*
+	 * This -might- happen due to race conditions, but is unlikely.
+	 * The scenario that leads to this happening is that the
+	 * first of the pair of duplicate callbacks is queued,
+	 * someone else starts a grace period that includes that
+	 * callback, then the second of the pair must wait for the
+	 * next grace period.  Unlikely, but can happen.  If it
+	 * does happen, the debug-objects subsystem won't have splatted.
+	 */
+	pr_alert("rcutorture: duplicated callback was invoked.\n");
+}
+#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+
+/*
+ * Verify that double-free causes debug-objects to complain, but only
+ * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.  Otherwise, say that the test
+ * cannot be carried out.
+ */
+static void rcu_test_debug_objects(void)
+{
+#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
+	struct rcu_head rh1;
+	struct rcu_head rh2;
+
+	init_rcu_head_on_stack(&rh1);
+	init_rcu_head_on_stack(&rh2);
+	pr_alert("rcutorture: WARN: Duplicate call_rcu() test starting.\n");
+
+	/* Try to queue the rh2 pair of callbacks for the same grace period. */
+	preempt_disable(); /* Prevent preemption from interrupting test. */
+	rcu_read_lock(); /* Make it impossible to finish a grace period. */
+	call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */
+	local_irq_disable(); /* Make it harder to start a new grace period. */
+	call_rcu(&rh2, rcu_torture_leak_cb);
+	call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
+	local_irq_enable();
+	rcu_read_unlock();
+	preempt_enable();
+
+	/* Wait for them all to get done so we can safely return. */
+	rcu_barrier();
+	pr_alert("rcutorture: WARN: Duplicate call_rcu() test complete.\n");
+	destroy_rcu_head_on_stack(&rh1);
+	destroy_rcu_head_on_stack(&rh2);
+#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+	pr_alert("rcutorture: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n");
+#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+}
+
+static int __init
+rcu_torture_init(void)
+{
+	int i;
+	int cpu;
+	int firsterr = 0;
+	int retval;
+	static struct rcu_torture_ops *torture_ops[] = {
+		&rcu_ops, &rcu_bh_ops, &srcu_ops, &sched_ops,
+	};
+
+	mutex_lock(&fullstop_mutex);
+
+	/* Process args and tell the world that the torturer is on the job. */
+	for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
+		cur_ops = torture_ops[i];
+		if (strcmp(torture_type, cur_ops->name) == 0)
+			break;
+	}
+	if (i == ARRAY_SIZE(torture_ops)) {
+		pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
+			 torture_type);
+		pr_alert("rcu-torture types:");
+		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
+			pr_alert(" %s", torture_ops[i]->name);
+		pr_alert("\n");
+		mutex_unlock(&fullstop_mutex);
+		return -EINVAL;
+	}
+	if (cur_ops->fqs == NULL && fqs_duration != 0) {
+		pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
+		fqs_duration = 0;
+	}
+	if (cur_ops->init)
+		cur_ops->init(); /* no "goto unwind" prior to this point!!! */
+
+	if (nreaders >= 0)
+		nrealreaders = nreaders;
+	else
+		nrealreaders = 2 * num_online_cpus();
+	rcu_torture_print_module_parms(cur_ops, "Start of test");
+	fullstop = FULLSTOP_DONTSTOP;
+
+	/* Set up the freelist. */
+
+	INIT_LIST_HEAD(&rcu_torture_freelist);
+	for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
+		rcu_tortures[i].rtort_mbtest = 0;
+		list_add_tail(&rcu_tortures[i].rtort_free,
+			      &rcu_torture_freelist);
+	}
+
+	/* Initialize the statistics so that each run gets its own numbers. */
+
+	rcu_torture_current = NULL;
+	rcu_torture_current_version = 0;
+	atomic_set(&n_rcu_torture_alloc, 0);
+	atomic_set(&n_rcu_torture_alloc_fail, 0);
+	atomic_set(&n_rcu_torture_free, 0);
+	atomic_set(&n_rcu_torture_mberror, 0);
+	atomic_set(&n_rcu_torture_error, 0);
+	n_rcu_torture_barrier_error = 0;
+	n_rcu_torture_boost_ktrerror = 0;
+	n_rcu_torture_boost_rterror = 0;
+	n_rcu_torture_boost_failure = 0;
+	n_rcu_torture_boosts = 0;
+	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
+		atomic_set(&rcu_torture_wcount[i], 0);
+	for_each_possible_cpu(cpu) {
+		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+			per_cpu(rcu_torture_count, cpu)[i] = 0;
+			per_cpu(rcu_torture_batch, cpu)[i] = 0;
+		}
+	}
+
+	/* Start up the kthreads. */
+
+	VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
+	writer_task = kthread_create(rcu_torture_writer, NULL,
+				     "rcu_torture_writer");
+	if (IS_ERR(writer_task)) {
+		firsterr = PTR_ERR(writer_task);
+		VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
+		writer_task = NULL;
+		goto unwind;
+	}
+	wake_up_process(writer_task);
+	fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
+				   GFP_KERNEL);
+	if (fakewriter_tasks == NULL) {
+		VERBOSE_PRINTK_ERRSTRING("out of memory");
+		firsterr = -ENOMEM;
+		goto unwind;
+	}
+	for (i = 0; i < nfakewriters; i++) {
+		VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
+		fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
+						  "rcu_torture_fakewriter");
+		if (IS_ERR(fakewriter_tasks[i])) {
+			firsterr = PTR_ERR(fakewriter_tasks[i]);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
+			fakewriter_tasks[i] = NULL;
+			goto unwind;
+		}
+	}
+	reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
+			       GFP_KERNEL);
+	if (reader_tasks == NULL) {
+		VERBOSE_PRINTK_ERRSTRING("out of memory");
+		firsterr = -ENOMEM;
+		goto unwind;
+	}
+	for (i = 0; i < nrealreaders; i++) {
+		VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
+		reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
+					      "rcu_torture_reader");
+		if (IS_ERR(reader_tasks[i])) {
+			firsterr = PTR_ERR(reader_tasks[i]);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
+			reader_tasks[i] = NULL;
+			goto unwind;
+		}
+	}
+	if (stat_interval > 0) {
+		VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
+		stats_task = kthread_run(rcu_torture_stats, NULL,
+					"rcu_torture_stats");
+		if (IS_ERR(stats_task)) {
+			firsterr = PTR_ERR(stats_task);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
+			stats_task = NULL;
+			goto unwind;
+		}
+	}
+	if (test_no_idle_hz) {
+		rcu_idle_cpu = num_online_cpus() - 1;
+
+		if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
+			firsterr = -ENOMEM;
+			VERBOSE_PRINTK_ERRSTRING("Failed to alloc mask");
+			goto unwind;
+		}
+
+		/* Create the shuffler thread */
+		shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
+					  "rcu_torture_shuffle");
+		if (IS_ERR(shuffler_task)) {
+			free_cpumask_var(shuffle_tmp_mask);
+			firsterr = PTR_ERR(shuffler_task);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
+			shuffler_task = NULL;
+			goto unwind;
+		}
+	}
+	if (stutter < 0)
+		stutter = 0;
+	if (stutter) {
+		/* Create the stutter thread */
+		stutter_task = kthread_run(rcu_torture_stutter, NULL,
+					  "rcu_torture_stutter");
+		if (IS_ERR(stutter_task)) {
+			firsterr = PTR_ERR(stutter_task);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
+			stutter_task = NULL;
+			goto unwind;
+		}
+	}
+	if (fqs_duration < 0)
+		fqs_duration = 0;
+	if (fqs_duration) {
+		/* Create the stutter thread */
+		fqs_task = kthread_run(rcu_torture_fqs, NULL,
+				       "rcu_torture_fqs");
+		if (IS_ERR(fqs_task)) {
+			firsterr = PTR_ERR(fqs_task);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create fqs");
+			fqs_task = NULL;
+			goto unwind;
+		}
+	}
+	if (test_boost_interval < 1)
+		test_boost_interval = 1;
+	if (test_boost_duration < 2)
+		test_boost_duration = 2;
+	if ((test_boost == 1 && cur_ops->can_boost) ||
+	    test_boost == 2) {
+
+		boost_starttime = jiffies + test_boost_interval * HZ;
+		register_cpu_notifier(&rcutorture_cpu_nb);
+		for_each_possible_cpu(i) {
+			if (cpu_is_offline(i))
+				continue;  /* Heuristic: CPU can go offline. */
+			retval = rcutorture_booster_init(i);
+			if (retval < 0) {
+				firsterr = retval;
+				goto unwind;
+			}
+		}
+	}
+	if (shutdown_secs > 0) {
+		shutdown_time = jiffies + shutdown_secs * HZ;
+		shutdown_task = kthread_create(rcu_torture_shutdown, NULL,
+					       "rcu_torture_shutdown");
+		if (IS_ERR(shutdown_task)) {
+			firsterr = PTR_ERR(shutdown_task);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create shutdown");
+			shutdown_task = NULL;
+			goto unwind;
+		}
+		wake_up_process(shutdown_task);
+	}
+	i = rcu_torture_onoff_init();
+	if (i != 0) {
+		firsterr = i;
+		goto unwind;
+	}
+	register_reboot_notifier(&rcutorture_shutdown_nb);
+	i = rcu_torture_stall_init();
+	if (i != 0) {
+		firsterr = i;
+		goto unwind;
+	}
+	retval = rcu_torture_barrier_init();
+	if (retval != 0) {
+		firsterr = retval;
+		goto unwind;
+	}
+	if (object_debug)
+		rcu_test_debug_objects();
+	rcutorture_record_test_transition();
+	mutex_unlock(&fullstop_mutex);
+	return 0;
+
+unwind:
+	mutex_unlock(&fullstop_mutex);
+	rcu_torture_cleanup();
+	return firsterr;
+}
+
+module_init(rcu_torture_init);
+module_exit(rcu_torture_cleanup);