Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3654 insertions, 0 deletions

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
new file mode 100644
index 000000000..503c2aa84
--- /dev/null
+++ b/kernel/rcu/rcutorture.c
@@ -0,0 +1,3654 @@
+// 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/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_LICENSE("GPL");
+MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
+
+/* 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	 (1 << RCUTORTURE_RDR_SHIFT_1)
+#define RCUTORTURE_RDR_SHIFT_2	 9	/* Put SRCU index in upper bits. */
+#define RCUTORTURE_RDR_MASK_2	 (1 << 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_NBITS	 7	/* Number of bits defined above. */
+#define RCUTORTURE_MAX_EXTEND	 \
+	(RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
+	 RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
+#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(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(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, 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(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, 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, 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_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_interval, 7, "Interval between boost tests, seconds.");
+torture_param(bool, test_no_idle_hz, true, "Test support for tickless idle CPUs");
+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 struct task_struct *writer_task;
+static struct task_struct **fakewriter_tasks;
+static struct task_struct **reader_tasks;
+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;
+
+#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_rterror;
+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;
+};
+static int err_segs_recorded;
+static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
+static int rt_read_nsegs;
+
+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);
+	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_gp_state)(void);
+	void (*get_gp_state_full)(struct rcu_gp_oldstate *rgosp);
+	unsigned long (*get_gp_completed)(void);
+	void (*get_gp_completed_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);
+	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);
+	long cbflood_max;
+	int irq_capable;
+	int can_boost;
+	int extendables;
+	int slow_gps;
+	int no_pi_lock;
+	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) __acquires(RCU)
+{
+	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() & (SOFTIRQ_MASK | HARDIRQ_MASK))
+			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. */
+		rtrsp->rt_preempted = true;
+	}
+}
+
+static void rcu_torture_read_unlock(int idx) __releases(RCU)
+{
+	rcu_read_unlock();
+}
+
+/*
+ * 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 = READ_ONCE(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);
+	if (rp->rtort_pipe_count >= 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(&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,
+	.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,
+	.get_gp_state		= get_state_synchronize_rcu,
+	.get_gp_state_full	= get_state_synchronize_rcu_full,
+	.get_gp_completed	= get_completed_synchronize_rcu,
+	.get_gp_completed_full	= get_completed_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,
+	.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,
+	.call			= call_rcu,
+	.cb_barrier		= rcu_barrier,
+	.fqs			= rcu_force_quiescent_state,
+	.stats			= NULL,
+	.gp_kthread_dbg		= show_rcu_gp_kthreads,
+	.check_boost_failed	= rcu_check_boost_fail,
+	.stall_dur		= rcu_jiffies_till_stall_check,
+	.irq_capable		= 1,
+	.can_boost		= IS_ENABLED(CONFIG_RCU_BOOST),
+	.extendables		= RCUTORTURE_MAX_EXTEND,
+	.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,
+	.cb_barrier	= NULL,
+	.fqs		= NULL,
+	.stats		= NULL,
+	.irq_capable	= 1,
+	.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 int srcu_torture_read_lock(void) __acquires(srcu_ctlp)
+{
+	return srcu_read_lock(srcu_ctlp);
+}
+
+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) __releases(srcu_ctlp)
+{
+	srcu_read_unlock(srcu_ctlp, idx);
+}
+
+static int torture_srcu_read_lock_held(void)
+{
+	return srcu_read_lock_held(srcu_ctlp);
+}
+
+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,
+	.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,
+	.get_gp_state	= srcu_torture_get_gp_state,
+	.start_gp_poll	= srcu_torture_start_gp_poll,
+	.poll_gp_state	= srcu_torture_poll_gp_state,
+	.call		= srcu_torture_call,
+	.cb_barrier	= srcu_torture_barrier,
+	.stats		= srcu_torture_stats,
+	.cbflood_max	= 50000,
+	.irq_capable	= 1,
+	.no_pi_lock	= IS_ENABLED(CONFIG_TINY_SRCU),
+	.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,
+	.get_gp_seq	= srcu_torture_completed,
+	.deferred_free	= srcu_torture_deferred_free,
+	.sync		= srcu_torture_synchronize,
+	.exp_sync	= srcu_torture_synchronize_expedited,
+	.get_gp_state	= srcu_torture_get_gp_state,
+	.start_gp_poll	= srcu_torture_start_gp_poll,
+	.poll_gp_state	= srcu_torture_poll_gp_state,
+	.call		= srcu_torture_call,
+	.cb_barrier	= srcu_torture_barrier,
+	.stats		= srcu_torture_stats,
+	.cbflood_max	= 50000,
+	.irq_capable	= 1,
+	.no_pi_lock	= IS_ENABLED(CONFIG_TINY_SRCU),
+	.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 necessarily work well with CPU hotplug.
+ */
+
+static void synchronize_rcu_trivial(void)
+{
+	int cpu;
+
+	for_each_online_cpu(cpu) {
+		rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
+		WARN_ON_ONCE(raw_smp_processor_id() != cpu);
+	}
+}
+
+static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
+{
+	preempt_disable();
+	return 0;
+}
+
+static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
+{
+	preempt_enable();
+}
+
+static struct rcu_torture_ops trivial_ops = {
+	.ttype		= RCU_TRIVIAL_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,
+	.readlock_held	= torture_readlock_not_held,
+	.get_gp_seq	= rcu_no_completed,
+	.sync		= synchronize_rcu_trivial,
+	.exp_sync	= synchronize_rcu_trivial,
+	.fqs		= NULL,
+	.stats		= NULL,
+	.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);
+}
+
+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,
+	.fqs		= NULL,
+	.stats		= NULL,
+	.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 void rcu_tasks_rude_torture_deferred_free(struct rcu_torture *p)
+{
+	call_rcu_tasks_rude(&p->rtort_rcu, rcu_torture_cb);
+}
+
+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,
+	.deferred_free	= rcu_tasks_rude_torture_deferred_free,
+	.sync		= synchronize_rcu_tasks_rude,
+	.exp_sync	= synchronize_rcu_tasks_rude,
+	.call		= call_rcu_tasks_rude,
+	.cb_barrier	= rcu_barrier_tasks_rude,
+	.gp_kthread_dbg	= show_rcu_tasks_rude_gp_kthread,
+	.cbflood_max	= 50000,
+	.fqs		= NULL,
+	.stats		= NULL,
+	.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,
+	.cbflood_max	= 50000,
+	.fqs		= NULL,
+	.stats		= NULL,
+	.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)
+				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;
+
+	VERBOSE_TOROUT_STRING("rcu_torture_boost started");
+
+	/* 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(1);
+		}
+
+		/* Go do the stutter. */
+checkwait:	if (stutter_wait("rcu_torture_boost"))
+			sched_set_fifo_low(current);
+	} while (!torture_must_stop());
+
+	/* Clean up and exit. */
+	while (!kthread_should_stop()) {
+		torture_shutdown_absorb("rcu_torture_boost");
+		schedule_timeout_uninterruptible(1);
+	}
+	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(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;
+		}
+		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->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->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__);
+	}
+}
+
+/*
+ * 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;
+	struct rcu_gp_oldstate gp_snap_full;
+	int i;
+	int idx;
+	int oldnice = task_nice(current);
+	struct rcu_torture *rp;
+	struct rcu_torture *old_rp;
+	static DEFINE_TORTURE_RANDOM(rand);
+	bool stutter_waited;
+
+	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;
+	}
+
+	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;
+		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);
+
+			// 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_gp_completed) {
+					cookie = cur_ops->get_gp_completed();
+					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_gp_completed_full) {
+					cur_ops->get_gp_completed_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_jiffies(torture_random(&rand) % 16, &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_jiffies(torture_random(&rand) % 16, &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_jiffies(torture_random(&rand) % 16, &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_jiffies(torture_random(&rand) % 16, &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;
+				gp_snap = cur_ops->start_gp_poll();
+				rcu_torture_writer_state = RTWS_POLL_WAIT;
+				while (!cur_ops->poll_gp_state(gp_snap))
+					torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+								  &rand);
+				rcu_torture_pipe_update(old_rp);
+				break;
+			case RTWS_POLL_GET_FULL:
+				rcu_torture_writer_state = RTWS_POLL_GET_FULL;
+				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))
+					torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+								  &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_jiffies(torture_random(&rand) % 16,
+								  &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_jiffies(torture_random(&rand) % 16,
+								  &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)
+			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();
+					WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
+					rcu_ftrace_dump(DUMP_ALL);
+				}
+		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);
+	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) % (nfakewriters * 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:
+				gp_snap = cur_ops->start_gp_poll();
+				while (!cur_ops->poll_gp_state(gp_snap)) {
+					torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+								  &rand);
+				}
+				break;
+			case RTWS_POLL_GET_FULL:
+				cur_ops->start_gp_poll_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_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))
+			(void)cmpxchg_relaxed(&rtrcp_chker->rtc_assigner, rtrcp, NULL); // Back out.
+	}
+
+	// If assigned some completed work, do it!
+	rtrcp_assigner = READ_ONCE(rtrcp->rtc_assigner);
+	if (!rtrcp_assigner || !smp_load_acquire(&rtrcp_assigner->rtc_ready))
+		return; // No work or work not yet ready.
+	rdrchked = rtrcp_assigner->rtc_chkrdr;
+	if (WARN_ON_ONCE(rdrchked < 0))
+		return;
+	rtrcp_chked = &rcu_torture_reader_mbchk[rdrchked];
+	loops = READ_ONCE(rtrcp_chked->rtc_myloops);
+	atomic_inc(&n_rcu_torture_mbchk_tries);
+	if (ULONG_CMP_LT(loops, rtrcp_assigner->rtc_chkloops))
+		atomic_inc(&n_rcu_torture_mbchk_fail);
+	rtrcp_assigner->rtc_chkloops = loops + ULONG_MAX / 2;
+	rtrcp_assigner->rtc_ready = 0;
+	smp_store_release(&rtrcp->rtc_assigner, NULL); // Someone else can assign us work.
+	smp_store_release(&rtrcp_assigner->rtc_chkrdr, -1); // Assigner can again assign.
+}
+
+/*
+ * Do one extension of an RCU read-side critical section using the
+ * current reader state in readstate (set to zero for initial entry
+ * to extended critical section), set the new state as specified by
+ * newstate (set to zero for final exit from extended critical section),
+ * and random-number-generator state in trsp.  If this is neither the
+ * beginning or end of the critical section and if there was actually a
+ * change, do a ->read_delay().
+ */
+static void rcutorture_one_extend(int *readstate, int newstate,
+				  struct torture_random_state *trsp,
+				  struct rt_read_seg *rtrsp)
+{
+	unsigned long flags;
+	int idxnew1 = -1;
+	int idxnew2 = -1;
+	int idxold1 = *readstate;
+	int idxold2 = idxold1;
+	int statesnew = ~*readstate & newstate;
+	int statesold = *readstate & ~newstate;
+
+	WARN_ON_ONCE(idxold2 < 0);
+	WARN_ON_ONCE((idxold2 >> RCUTORTURE_RDR_SHIFT_2) > 1);
+	rtrsp->rt_readstate = newstate;
+
+	/* First, put new protection in place to avoid critical-section gap. */
+	if (statesnew & RCUTORTURE_RDR_BH)
+		local_bh_disable();
+	if (statesnew & RCUTORTURE_RDR_RBH)
+		rcu_read_lock_bh();
+	if (statesnew & RCUTORTURE_RDR_IRQ)
+		local_irq_disable();
+	if (statesnew & RCUTORTURE_RDR_PREEMPT)
+		preempt_disable();
+	if (statesnew & RCUTORTURE_RDR_SCHED)
+		rcu_read_lock_sched();
+	if (statesnew & RCUTORTURE_RDR_RCU_1)
+		idxnew1 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_1;
+	if (statesnew & RCUTORTURE_RDR_RCU_2)
+		idxnew2 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_2;
+
+	/*
+	 * Next, remove old protection, in decreasing order of strength
+	 * to avoid unlock paths that aren't safe in the stronger
+	 * context. Namely: BH can not be enabled with disabled interrupts.
+	 * Additionally PREEMPT_RT requires that BH is enabled in preemptible
+	 * context.
+	 */
+	if (statesold & RCUTORTURE_RDR_IRQ)
+		local_irq_enable();
+	if (statesold & RCUTORTURE_RDR_PREEMPT)
+		preempt_enable();
+	if (statesold & RCUTORTURE_RDR_SCHED)
+		rcu_read_unlock_sched();
+	if (statesold & RCUTORTURE_RDR_BH)
+		local_bh_enable();
+	if (statesold & RCUTORTURE_RDR_RBH)
+		rcu_read_unlock_bh();
+	if (statesold & RCUTORTURE_RDR_RCU_2) {
+		cur_ops->readunlock((idxold2 >> RCUTORTURE_RDR_SHIFT_2) & 0x1);
+		WARN_ON_ONCE(idxnew2 != -1);
+		idxold2 = 0;
+	}
+	if (statesold & RCUTORTURE_RDR_RCU_1) {
+		bool lockit;
+
+		lockit = !cur_ops->no_pi_lock && !statesnew && !(torture_random(trsp) & 0xffff);
+		if (lockit)
+			raw_spin_lock_irqsave(&current->pi_lock, flags);
+		cur_ops->readunlock((idxold1 >> RCUTORTURE_RDR_SHIFT_1) & 0x1);
+		WARN_ON_ONCE(idxnew1 != -1);
+		idxold1 = 0;
+		if (lockit)
+			raw_spin_unlock_irqrestore(&current->pi_lock, flags);
+	}
+
+	/* Delay if neither beginning nor end and there was a change. */
+	if ((statesnew || statesold) && *readstate && newstate)
+		cur_ops->read_delay(trsp, rtrsp);
+
+	/* Update the reader state. */
+	if (idxnew1 == -1)
+		idxnew1 = idxold1 & RCUTORTURE_RDR_MASK_1;
+	WARN_ON_ONCE(idxnew1 < 0);
+	if (WARN_ON_ONCE((idxnew1 >> RCUTORTURE_RDR_SHIFT_1) > 1))
+		pr_info("Unexpected idxnew1 value of %#x\n", idxnew1);
+	if (idxnew2 == -1)
+		idxnew2 = idxold2 & RCUTORTURE_RDR_MASK_2;
+	WARN_ON_ONCE(idxnew2 < 0);
+	WARN_ON_ONCE((idxnew2 >> RCUTORTURE_RDR_SHIFT_2) > 1);
+	*readstate = idxnew1 | idxnew2 | newstate;
+	WARN_ON_ONCE(*readstate < 0);
+	if (WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT_2) > 1))
+		pr_info("Unexpected idxnew2 value of %#x\n", idxnew2);
+}
+
+/* Return the biggest extendables mask given current RCU and boot parameters. */
+static int rcutorture_extend_mask_max(void)
+{
+	int mask;
+
+	WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND);
+	mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables;
+	mask = mask | RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2;
+	return mask;
+}
+
+/* Return a random protection state mask, but with at least one bit set. */
+static int
+rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
+{
+	int mask = rcutorture_extend_mask_max();
+	unsigned long randmask1 = torture_random(trsp) >> 8;
+	unsigned long randmask2 = randmask1 >> 3;
+	unsigned long preempts = RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
+	unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ;
+	unsigned long bhs = RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
+
+	WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1);
+	/* Mostly only one bit (need preemption!), sometimes lots of bits. */
+	if (!(randmask1 & 0x7))
+		mask = mask & randmask2;
+	else
+		mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));
+
+	// Can't have nested RCU reader without outer RCU reader.
+	if (!(mask & RCUTORTURE_RDR_RCU_1) && (mask & RCUTORTURE_RDR_RCU_2)) {
+		if (oldmask & RCUTORTURE_RDR_RCU_1)
+			mask &= ~RCUTORTURE_RDR_RCU_2;
+		else
+			mask |= RCUTORTURE_RDR_RCU_1;
+	}
+
+	/*
+	 * Can't enable bh w/irq disabled.
+	 */
+	if (mask & RCUTORTURE_RDR_IRQ)
+		mask |= oldmask & bhs;
+
+	/*
+	 * Ideally these sequences would be detected in debug builds
+	 * (regardless of RT), but until then don't stop testing
+	 * them on non-RT.
+	 */
+	if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
+		/* Can't modify BH in atomic context */
+		if (oldmask & preempts_irq)
+			mask &= ~bhs;
+		if ((oldmask | mask) & preempts_irq)
+			mask |= oldmask & bhs;
+	}
+
+	return mask ?: RCUTORTURE_RDR_RCU_1;
+}
+
+/*
+ * Do a randomly selected number of extensions of an existing RCU read-side
+ * critical section.
+ */
+static struct rt_read_seg *
+rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
+		       struct rt_read_seg *rtrsp)
+{
+	int i;
+	int j;
+	int mask = rcutorture_extend_mask_max();
+
+	WARN_ON_ONCE(!*readstate); /* -Existing- RCU read-side critsect! */
+	if (!((mask - 1) & mask))
+		return rtrsp;  /* Current RCU reader not extendable. */
+	/* Bias towards larger numbers of loops. */
+	i = (torture_random(trsp) >> 3);
+	i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
+	for (j = 0; j < i; j++) {
+		mask = rcutorture_extend_mask(*readstate, trsp);
+		rcutorture_one_extend(readstate, mask, trsp, &rtrsp[j]);
+	}
+	return &rtrsp[j];
+}
+
+/*
+ * Do one read-side critical section, returning false if there was
+ * no data to read.  Can be invoked both from process context and
+ * from a timer handler.
+ */
+static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
+{
+	bool checkpolling = !(torture_random(trsp) & 0xfff);
+	unsigned long cookie;
+	struct rcu_gp_oldstate cookie_full;
+	int i;
+	unsigned long started;
+	unsigned long completed;
+	int newstate;
+	struct rcu_torture *p;
+	int pipe_count;
+	int readstate = 0;
+	struct rt_read_seg rtseg[RCUTORTURE_RDR_MAX_SEGS] = { { 0 } };
+	struct rt_read_seg *rtrsp = &rtseg[0];
+	struct rt_read_seg *rtrsp1;
+	unsigned long long ts;
+
+	WARN_ON_ONCE(!rcu_is_watching());
+	newstate = rcutorture_extend_mask(readstate, trsp);
+	rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
+	if (checkpolling) {
+		if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
+			cookie = cur_ops->get_gp_state();
+		if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full)
+			cur_ops->get_gp_state_full(&cookie_full);
+	}
+	started = cur_ops->get_gp_seq();
+	ts = rcu_trace_clock_local();
+	p = rcu_dereference_check(rcu_torture_current,
+				  !cur_ops->readlock_held || cur_ops->readlock_held());
+	if (p == NULL) {
+		/* Wait for rcu_torture_writer to get underway */
+		rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
+		return false;
+	}
+	if (p->rtort_mbtest == 0)
+		atomic_inc(&n_rcu_torture_mberror);
+	rcu_torture_reader_do_mbchk(myid, p, trsp);
+	rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
+	preempt_disable();
+	pipe_count = READ_ONCE(p->rtort_pipe_count);
+	if (pipe_count > RCU_TORTURE_PIPE_LEN) {
+		/* Should not happen, but... */
+		pipe_count = RCU_TORTURE_PIPE_LEN;
+	}
+	completed = cur_ops->get_gp_seq();
+	if (pipe_count > 1) {
+		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
+					  ts, started, completed);
+		rcu_ftrace_dump(DUMP_ALL);
+	}
+	__this_cpu_inc(rcu_torture_count[pipe_count]);
+	completed = rcutorture_seq_diff(completed, started);
+	if (completed > RCU_TORTURE_PIPE_LEN) {
+		/* Should not happen, but... */
+		completed = RCU_TORTURE_PIPE_LEN;
+	}
+	__this_cpu_inc(rcu_torture_batch[completed]);
+	preempt_enable();
+	if (checkpolling) {
+		if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
+			WARN_ONCE(cur_ops->poll_gp_state(cookie),
+				  "%s: Cookie check 2 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_gp_state_full && cur_ops->poll_gp_state_full)
+			WARN_ONCE(cur_ops->poll_gp_state_full(&cookie_full),
+				  "%s: Cookie check 6 failed %s(%d) online %*pbl\n",
+				  __func__,
+				  rcu_torture_writer_state_getname(),
+				  rcu_torture_writer_state,
+				  cpumask_pr_args(cpu_online_mask));
+	}
+	rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
+	WARN_ON_ONCE(readstate);
+	// This next splat is expected behavior if leakpointer, especially
+	// for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels.
+	WARN_ON_ONCE(leakpointer && READ_ONCE(p->rtort_pipe_count) > 1);
+
+	/* If error or close call, record the sequence of reader protections. */
+	if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
+		i = 0;
+		for (rtrsp1 = &rtseg[0]; rtrsp1 < rtrsp; rtrsp1++)
+			err_segs[i++] = *rtrsp1;
+		rt_read_nsegs = i;
+	}
+
+	return true;
+}
+
+static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);
+
+/*
+ * 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(struct timer_list *unused)
+{
+	atomic_long_inc(&n_rcu_torture_timers);
+	(void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand), -1);
+
+	/* Test call_rcu() invocation from interrupt handler. */
+	if (cur_ops->call) {
+		struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_NOWAIT);
+
+		if (rhp)
+			cur_ops->call(rhp, rcu_torture_timer_cb);
+	}
+}
+
+/*
+ * 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)
+{
+	unsigned long lastsleep = jiffies;
+	long myid = (long)arg;
+	int mynumonline = myid;
+	DEFINE_TORTURE_RANDOM(rand);
+	struct timer_list t;
+
+	VERBOSE_TOROUT_STRING("rcu_torture_reader task started");
+	set_user_nice(current, MAX_NICE);
+	if (irqreader && cur_ops->irq_capable)
+		timer_setup_on_stack(&t, rcu_torture_timer, 0);
+	tick_dep_set_task(current, TICK_DEP_BIT_RCU);
+	do {
+		if (irqreader && cur_ops->irq_capable) {
+			if (!timer_pending(&t))
+				mod_timer(&t, jiffies + 1);
+		}
+		if (!rcu_torture_one_read(&rand, myid) && !torture_must_stop())
+			schedule_timeout_interruptible(HZ);
+		if (time_after(jiffies, lastsleep) && !torture_must_stop()) {
+			torture_hrtimeout_us(500, 1000, &rand);
+			lastsleep = jiffies + 10;
+		}
+		while (torture_num_online_cpus() < mynumonline && !torture_must_stop())
+			schedule_timeout_interruptible(HZ / 5);
+		stutter_wait("rcu_torture_reader");
+	} while (!torture_must_stop());
+	if (irqreader && cur_ops->irq_capable) {
+		del_timer_sync(&t);
+		destroy_timer_on_stack(&t);
+	}
+	tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
+	torture_kthread_stopping("rcu_torture_reader");
+	return 0;
+}
+
+/*
+ * Randomly Toggle CPUs' callback-offload state.  This uses hrtimers to
+ * increase race probabilities and fuzzes the interval between toggling.
+ */
+static int rcu_nocb_toggle(void *arg)
+{
+	int cpu;
+	int maxcpu = -1;
+	int oldnice = task_nice(current);
+	long r;
+	DEFINE_TORTURE_RANDOM(rand);
+	ktime_t toggle_delay;
+	unsigned long toggle_fuzz;
+	ktime_t toggle_interval = ms_to_ktime(nocbs_toggle);
+
+	VERBOSE_TOROUT_STRING("rcu_nocb_toggle task started");
+	while (!rcu_inkernel_boot_has_ended())
+		schedule_timeout_interruptible(HZ / 10);
+	for_each_online_cpu(cpu)
+		maxcpu = cpu;
+	WARN_ON(maxcpu < 0);
+	if (toggle_interval > ULONG_MAX)
+		toggle_fuzz = ULONG_MAX >> 3;
+	else
+		toggle_fuzz = toggle_interval >> 3;
+	if (toggle_fuzz <= 0)
+		toggle_fuzz = NSEC_PER_USEC;
+	do {
+		r = torture_random(&rand);
+		cpu = (r >> 4) % (maxcpu + 1);
+		if (r & 0x1) {
+			rcu_nocb_cpu_offload(cpu);
+			atomic_long_inc(&n_nocb_offload);
+		} else {
+			rcu_nocb_cpu_deoffload(cpu);
+			atomic_long_inc(&n_nocb_deoffload);
+		}
+		toggle_delay = torture_random(&rand) % toggle_fuzz + toggle_interval;
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule_hrtimeout(&toggle_delay, HRTIMER_MODE_REL);
+		if (stutter_wait("rcu_nocb_toggle"))
+			sched_set_normal(current, oldnice);
+	} while (!torture_must_stop());
+	torture_kthread_stopping("rcu_nocb_toggle");
+	return 0;
+}
+
+/*
+ * 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 cpu;
+	int i;
+	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+	struct rcu_torture *rtcp;
+	static unsigned long rtcv_snap = ULONG_MAX;
+	static bool splatted;
+	struct task_struct *wtp;
+
+	for_each_possible_cpu(cpu) {
+		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+			pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
+			batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
+		}
+	}
+	for (i = RCU_TORTURE_PIPE_LEN; i >= 0; i--) {
+		if (pipesummary[i] != 0)
+			break;
+	}
+
+	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
+	rtcp = rcu_access_pointer(rcu_torture_current);
+	pr_cont("rtc: %p %s: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
+		rtcp,
+		rtcp && !rcu_stall_is_suppressed_at_boot() ? "ver" : "VER",
+		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));
+	pr_cont("rtmbe: %d rtmbkf: %d/%d rtbe: %ld rtbke: %ld rtbre: %ld ",
+		atomic_read(&n_rcu_torture_mberror),
+		atomic_read(&n_rcu_torture_mbchk_fail), atomic_read(&n_rcu_torture_mbchk_tries),
+		n_rcu_torture_barrier_error,
+		n_rcu_torture_boost_ktrerror,
+		n_rcu_torture_boost_rterror);
+	pr_cont("rtbf: %ld rtb: %ld nt: %ld ",
+		n_rcu_torture_boost_failure,
+		n_rcu_torture_boosts,
+		atomic_long_read(&n_rcu_torture_timers));
+	torture_onoff_stats();
+	pr_cont("barrier: %ld/%ld:%ld ",
+		data_race(n_barrier_successes),
+		data_race(n_barrier_attempts),
+		data_race(n_rcu_torture_barrier_error));
+	pr_cont("read-exits: %ld ", data_race(n_read_exits)); // Statistic.
+	pr_cont("nocb-toggles: %ld:%ld\n",
+		atomic_long_read(&n_nocb_offload), atomic_long_read(&n_nocb_deoffload));
+
+	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
+	if (atomic_read(&n_rcu_torture_mberror) ||
+	    atomic_read(&n_rcu_torture_mbchk_fail) ||
+	    n_rcu_torture_barrier_error || n_rcu_torture_boost_ktrerror ||
+	    n_rcu_torture_boost_rterror || n_rcu_torture_boost_failure ||
+	    i > 1) {
+		pr_cont("%s", "!!! ");
+		atomic_inc(&n_rcu_torture_error);
+		WARN_ON_ONCE(atomic_read(&n_rcu_torture_mberror));
+		WARN_ON_ONCE(atomic_read(&n_rcu_torture_mbchk_fail));
+		WARN_ON_ONCE(n_rcu_torture_barrier_error);  // rcu_barrier()
+		WARN_ON_ONCE(n_rcu_torture_boost_ktrerror); // no boost kthread
+		WARN_ON_ONCE(n_rcu_torture_boost_rterror); // can't set RT prio
+		WARN_ON_ONCE(n_rcu_torture_boost_failure); // boost failed (TIMER_SOFTIRQ RT prio?)
+		WARN_ON_ONCE(i > 1); // Too-short grace period
+	}
+	pr_cont("Reader Pipe: ");
+	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
+		pr_cont(" %ld", pipesummary[i]);
+	pr_cont("\n");
+
+	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
+	pr_cont("Reader Batch: ");
+	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
+		pr_cont(" %ld", batchsummary[i]);
+	pr_cont("\n");
+
+	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
+	pr_cont("Free-Block Circulation: ");
+	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+		pr_cont(" %d", atomic_read(&rcu_torture_wcount[i]));
+	}
+	pr_cont("\n");
+
+	if (cur_ops->stats)
+		cur_ops->stats();
+	if (rtcv_snap == rcu_torture_current_version &&
+	    rcu_access_pointer(rcu_torture_current) &&
+	    !rcu_stall_is_suppressed()) {
+		int __maybe_unused flags = 0;
+		unsigned long __maybe_unused gp_seq = 0;
+
+		rcutorture_get_gp_data(cur_ops->ttype,
+				       &flags, &gp_seq);
+		srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
+					&flags, &gp_seq);
+		wtp = READ_ONCE(writer_task);
+		pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#x cpu %d\n",
+			 rcu_torture_writer_state_getname(),
+			 rcu_torture_writer_state, gp_seq, flags,
+			 wtp == NULL ? ~0U : wtp->__state,
+			 wtp == NULL ? -1 : (int)task_cpu(wtp));
+		if (!splatted && wtp) {
+			sched_show_task(wtp);
+			splatted = true;
+		}
+		if (cur_ops->gp_kthread_dbg)
+			cur_ops->gp_kthread_dbg();
+		rcu_ftrace_dump(DUMP_ALL);
+	}
+	rtcv_snap = rcu_torture_current_version;
+}
+
+/*
+ * Periodically prints torture statistics, if periodic statistics printing
+ * was specified via the stat_interval module parameter.
+ */
+static int
+rcu_torture_stats(void *arg)
+{
+	VERBOSE_TOROUT_STRING("rcu_torture_stats task started");
+	do {
+		schedule_timeout_interruptible(stat_interval * HZ);
+		rcu_torture_stats_print();
+		torture_shutdown_absorb("rcu_torture_stats");
+	} while (!torture_must_stop());
+	torture_kthread_stopping("rcu_torture_stats");
+	return 0;
+}
+
+/* Test mem_dump_obj() and friends.  */
+static void rcu_torture_mem_dump_obj(void)
+{
+	struct rcu_head *rhp;
+	struct kmem_cache *kcp;
+	static int z;
+
+	kcp = kmem_cache_create("rcuscale", 136, 8, SLAB_STORE_USER, NULL);
+	if (WARN_ON_ONCE(!kcp))
+		return;
+	rhp = kmem_cache_alloc(kcp, GFP_KERNEL);
+	if (WARN_ON_ONCE(!rhp)) {
+		kmem_cache_destroy(kcp);
+		return;
+	}
+	pr_alert("mem_dump_obj() slab test: rcu_torture_stats = %px, &rhp = %px, rhp = %px, &z = %px\n", stats_task, &rhp, rhp, &z);
+	pr_alert("mem_dump_obj(ZERO_SIZE_PTR):");
+	mem_dump_obj(ZERO_SIZE_PTR);
+	pr_alert("mem_dump_obj(NULL):");
+	mem_dump_obj(NULL);
+	pr_alert("mem_dump_obj(%px):", &rhp);
+	mem_dump_obj(&rhp);
+	pr_alert("mem_dump_obj(%px):", rhp);
+	mem_dump_obj(rhp);
+	pr_alert("mem_dump_obj(%px):", &rhp->func);
+	mem_dump_obj(&rhp->func);
+	pr_alert("mem_dump_obj(%px):", &z);
+	mem_dump_obj(&z);
+	kmem_cache_free(kcp, rhp);
+	kmem_cache_destroy(kcp);
+	rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
+	if (WARN_ON_ONCE(!rhp))
+		return;
+	pr_alert("mem_dump_obj() kmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
+	pr_alert("mem_dump_obj(kmalloc %px):", rhp);
+	mem_dump_obj(rhp);
+	pr_alert("mem_dump_obj(kmalloc %px):", &rhp->func);
+	mem_dump_obj(&rhp->func);
+	kfree(rhp);
+	rhp = vmalloc(4096);
+	if (WARN_ON_ONCE(!rhp))
+		return;
+	pr_alert("mem_dump_obj() vmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
+	pr_alert("mem_dump_obj(vmalloc %px):", rhp);
+	mem_dump_obj(rhp);
+	pr_alert("mem_dump_obj(vmalloc %px):", &rhp->func);
+	mem_dump_obj(&rhp->func);
+	vfree(rhp);
+}
+
+static 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 stall_cpu_irqsoff=%d "
+		 "stall_cpu_block=%d "
+		 "n_barrier_cbs=%d "
+		 "onoff_interval=%d onoff_holdoff=%d "
+		 "read_exit_delay=%d read_exit_burst=%d "
+		 "nocbs_nthreads=%d nocbs_toggle=%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, stall_cpu_irqsoff,
+		 stall_cpu_block,
+		 n_barrier_cbs,
+		 onoff_interval, onoff_holdoff,
+		 read_exit_delay, read_exit_burst,
+		 nocbs_nthreads, nocbs_toggle);
+}
+
+static int rcutorture_booster_cleanup(unsigned int cpu)
+{
+	struct task_struct *t;
+
+	if (boost_tasks[cpu] == NULL)
+		return 0;
+	mutex_lock(&boost_mutex);
+	t = boost_tasks[cpu];
+	boost_tasks[cpu] = NULL;
+	rcu_torture_enable_rt_throttle();
+	mutex_unlock(&boost_mutex);
+
+	/* This must be outside of the mutex, otherwise deadlock! */
+	torture_stop_kthread(rcu_torture_boost, t);
+	return 0;
+}
+
+static int rcutorture_booster_init(unsigned int cpu)
+{
+	int retval;
+
+	if (boost_tasks[cpu] != NULL)
+		return 0;  /* Already created, nothing more to do. */
+
+	// Testing RCU priority boosting requires rcutorture do
+	// some serious abuse.  Counter this by running ksoftirqd
+	// at higher priority.
+	if (IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) {
+		struct sched_param sp;
+		struct task_struct *t;
+
+		t = per_cpu(ksoftirqd, cpu);
+		WARN_ON_ONCE(!t);
+		sp.sched_priority = 2;
+		sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
+	}
+
+	/* Don't allow time recalculation while creating a new task. */
+	mutex_lock(&boost_mutex);
+	rcu_torture_disable_rt_throttle();
+	VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
+	boost_tasks[cpu] = kthread_run_on_cpu(rcu_torture_boost, NULL,
+					      cpu, "rcu_torture_boost_%u");
+	if (IS_ERR(boost_tasks[cpu])) {
+		retval = PTR_ERR(boost_tasks[cpu]);
+		VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed");
+		n_rcu_torture_boost_ktrerror++;
+		boost_tasks[cpu] = NULL;
+		mutex_unlock(&boost_mutex);
+		return retval;
+	}
+	mutex_unlock(&boost_mutex);
+	return 0;
+}
+
+/*
+ * 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)
+{
+	int idx;
+	unsigned long stop_at;
+
+	VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
+	if (stall_cpu_holdoff > 0) {
+		VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
+		schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
+		VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
+	}
+	if (!kthread_should_stop() && stall_gp_kthread > 0) {
+		VERBOSE_TOROUT_STRING("rcu_torture_stall begin GP stall");
+		rcu_gp_set_torture_wait(stall_gp_kthread * HZ);
+		for (idx = 0; idx < stall_gp_kthread + 2; idx++) {
+			if (kthread_should_stop())
+				break;
+			schedule_timeout_uninterruptible(HZ);
+		}
+	}
+	if (!kthread_should_stop() && stall_cpu > 0) {
+		VERBOSE_TOROUT_STRING("rcu_torture_stall begin CPU stall");
+		stop_at = ktime_get_seconds() + stall_cpu;
+		/* RCU CPU stall is expected behavior in following code. */
+		idx = cur_ops->readlock();
+		if (stall_cpu_irqsoff)
+			local_irq_disable();
+		else if (!stall_cpu_block)
+			preempt_disable();
+		pr_alert("%s start on CPU %d.\n",
+			  __func__, raw_smp_processor_id());
+		while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
+				    stop_at))
+			if (stall_cpu_block) {
+#ifdef CONFIG_PREEMPTION
+				preempt_schedule();
+#else
+				schedule_timeout_uninterruptible(HZ);
+#endif
+			} else if (stall_no_softlockup) {
+				touch_softlockup_watchdog();
+			}
+		if (stall_cpu_irqsoff)
+			local_irq_enable();
+		else if (!stall_cpu_block)
+			preempt_enable();
+		cur_ops->readunlock(idx);
+	}
+	pr_alert("%s end.\n", __func__);
+	torture_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)
+{
+	if (stall_cpu <= 0 && stall_gp_kthread <= 0)
+		return 0;
+	return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
+}
+
+/* State structure for forward-progress self-propagating RCU callback. */
+struct fwd_cb_state {
+	struct rcu_head rh;
+	int stop;
+};
+
+/*
+ * Forward-progress self-propagating RCU callback function.  Because
+ * callbacks run from softirq, this function is an implicit RCU read-side
+ * critical section.
+ */
+static void rcu_torture_fwd_prog_cb(struct rcu_head *rhp)
+{
+	struct fwd_cb_state *fcsp = container_of(rhp, struct fwd_cb_state, rh);
+
+	if (READ_ONCE(fcsp->stop)) {
+		WRITE_ONCE(fcsp->stop, 2);
+		return;
+	}
+	cur_ops->call(&fcsp->rh, rcu_torture_fwd_prog_cb);
+}
+
+/* State for continuous-flood RCU callbacks. */
+struct rcu_fwd_cb {
+	struct rcu_head rh;
+	struct rcu_fwd_cb *rfc_next;
+	struct rcu_fwd *rfc_rfp;
+	int rfc_gps;
+};
+
+#define MAX_FWD_CB_JIFFIES	(8 * HZ) /* Maximum CB test duration. */
+#define MIN_FWD_CB_LAUNDERS	3	/* This many CB invocations to count. */
+#define MIN_FWD_CBS_LAUNDERED	100	/* Number of counted CBs. */
+#define FWD_CBS_HIST_DIV	10	/* Histogram buckets/second. */
+#define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))
+
+struct rcu_launder_hist {
+	long n_launders;
+	unsigned long launder_gp_seq;
+};
+
+struct rcu_fwd {
+	spinlock_t rcu_fwd_lock;
+	struct rcu_fwd_cb *rcu_fwd_cb_head;
+	struct rcu_fwd_cb **rcu_fwd_cb_tail;
+	long n_launders_cb;
+	unsigned long rcu_fwd_startat;
+	struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
+	unsigned long rcu_launder_gp_seq_start;
+	int rcu_fwd_id;
+};
+
+static DEFINE_MUTEX(rcu_fwd_mutex);
+static struct rcu_fwd *rcu_fwds;
+static unsigned long rcu_fwd_seq;
+static atomic_long_t rcu_fwd_max_cbs;
+static bool rcu_fwd_emergency_stop;
+
+static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
+{
+	unsigned long gps;
+	unsigned long gps_old;
+	int i;
+	int j;
+
+	for (i = ARRAY_SIZE(rfp->n_launders_hist) - 1; i > 0; i--)
+		if (rfp->n_launders_hist[i].n_launders > 0)
+			break;
+	pr_alert("%s: Callback-invocation histogram %d (duration %lu jiffies):",
+		 __func__, rfp->rcu_fwd_id, jiffies - rfp->rcu_fwd_startat);
+	gps_old = rfp->rcu_launder_gp_seq_start;
+	for (j = 0; j <= i; j++) {
+		gps = rfp->n_launders_hist[j].launder_gp_seq;
+		pr_cont(" %ds/%d: %ld:%ld",
+			j + 1, FWD_CBS_HIST_DIV,
+			rfp->n_launders_hist[j].n_launders,
+			rcutorture_seq_diff(gps, gps_old));
+		gps_old = gps;
+	}
+	pr_cont("\n");
+}
+
+/* Callback function for continuous-flood RCU callbacks. */
+static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
+{
+	unsigned long flags;
+	int i;
+	struct rcu_fwd_cb *rfcp = container_of(rhp, struct rcu_fwd_cb, rh);
+	struct rcu_fwd_cb **rfcpp;
+	struct rcu_fwd *rfp = rfcp->rfc_rfp;
+
+	rfcp->rfc_next = NULL;
+	rfcp->rfc_gps++;
+	spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
+	rfcpp = rfp->rcu_fwd_cb_tail;
+	rfp->rcu_fwd_cb_tail = &rfcp->rfc_next;
+	WRITE_ONCE(*rfcpp, rfcp);
+	WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1);
+	i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
+	if (i >= ARRAY_SIZE(rfp->n_launders_hist))
+		i = ARRAY_SIZE(rfp->n_launders_hist) - 1;
+	rfp->n_launders_hist[i].n_launders++;
+	rfp->n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();
+	spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
+}
+
+// Give the scheduler a chance, even on nohz_full CPUs.
+static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)
+{
+	if (IS_ENABLED(CONFIG_PREEMPTION) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
+		// Real call_rcu() floods hit userspace, so emulate that.
+		if (need_resched() || (iter & 0xfff))
+			schedule();
+		return;
+	}
+	// No userspace emulation: CB invocation throttles call_rcu()
+	cond_resched();
+}
+
+/*
+ * Free all callbacks on the rcu_fwd_cb_head list, either because the
+ * test is over or because we hit an OOM event.
+ */
+static unsigned long rcu_torture_fwd_prog_cbfree(struct rcu_fwd *rfp)
+{
+	unsigned long flags;
+	unsigned long freed = 0;
+	struct rcu_fwd_cb *rfcp;
+
+	for (;;) {
+		spin_lock_irqsave(&rfp->rcu_fwd_lock, flags);
+		rfcp = rfp->rcu_fwd_cb_head;
+		if (!rfcp) {
+			spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
+			break;
+		}
+		rfp->rcu_fwd_cb_head = rfcp->rfc_next;
+		if (!rfp->rcu_fwd_cb_head)
+			rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
+		spin_unlock_irqrestore(&rfp->rcu_fwd_lock, flags);
+		kfree(rfcp);
+		freed++;
+		rcu_torture_fwd_prog_cond_resched(freed);
+		if (tick_nohz_full_enabled()) {
+			local_irq_save(flags);
+			rcu_momentary_dyntick_idle();
+			local_irq_restore(flags);
+		}
+	}
+	return freed;
+}
+
+/* Carry out need_resched()/cond_resched() forward-progress testing. */
+static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
+				    int *tested, int *tested_tries)
+{
+	unsigned long cver;
+	unsigned long dur;
+	struct fwd_cb_state fcs;
+	unsigned long gps;
+	int idx;
+	int sd;
+	int sd4;
+	bool selfpropcb = false;
+	unsigned long stopat;
+	static DEFINE_TORTURE_RANDOM(trs);
+
+	pr_alert("%s: Starting forward-progress test %d\n", __func__, rfp->rcu_fwd_id);
+	if (!cur_ops->sync)
+		return; // Cannot do need_resched() forward progress testing without ->sync.
+	if (cur_ops->call && cur_ops->cb_barrier) {
+		init_rcu_head_on_stack(&fcs.rh);
+		selfpropcb = true;
+	}
+
+	/* Tight loop containing cond_resched(). */
+	atomic_inc(&rcu_fwd_cb_nodelay);
+	cur_ops->sync(); /* Later readers see above write. */
+	if  (selfpropcb) {
+		WRITE_ONCE(fcs.stop, 0);
+		cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
+	}
+	cver = READ_ONCE(rcu_torture_current_version);
+	gps = cur_ops->get_gp_seq();
+	sd = cur_ops->stall_dur() + 1;
+	sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
+	dur = sd4 + torture_random(&trs) % (sd - sd4);
+	WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
+	stopat = rfp->rcu_fwd_startat + dur;
+	while (time_before(jiffies, stopat) &&
+	       !shutdown_time_arrived() &&
+	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
+		idx = cur_ops->readlock();
+		udelay(10);
+		cur_ops->readunlock(idx);
+		if (!fwd_progress_need_resched || need_resched())
+			cond_resched();
+	}
+	(*tested_tries)++;
+	if (!time_before(jiffies, stopat) &&
+	    !shutdown_time_arrived() &&
+	    !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
+		(*tested)++;
+		cver = READ_ONCE(rcu_torture_current_version) - cver;
+		gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
+		WARN_ON(!cver && gps < 2);
+		pr_alert("%s: %d Duration %ld cver %ld gps %ld\n", __func__,
+			 rfp->rcu_fwd_id, dur, cver, gps);
+	}
+	if (selfpropcb) {
+		WRITE_ONCE(fcs.stop, 1);
+		cur_ops->sync(); /* Wait for running CB to complete. */
+		pr_alert("%s: Waiting for CBs: %pS() %d\n", __func__, cur_ops->cb_barrier, rfp->rcu_fwd_id);
+		cur_ops->cb_barrier(); /* Wait for queued callbacks. */
+	}
+
+	if (selfpropcb) {
+		WARN_ON(READ_ONCE(fcs.stop) != 2);
+		destroy_rcu_head_on_stack(&fcs.rh);
+	}
+	schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
+	atomic_dec(&rcu_fwd_cb_nodelay);
+}
+
+/* Carry out call_rcu() forward-progress testing. */
+static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
+{
+	unsigned long cver;
+	unsigned long flags;
+	unsigned long gps;
+	int i;
+	long n_launders;
+	long n_launders_cb_snap;
+	long n_launders_sa;
+	long n_max_cbs;
+	long n_max_gps;
+	struct rcu_fwd_cb *rfcp;
+	struct rcu_fwd_cb *rfcpn;
+	unsigned long stopat;
+	unsigned long stoppedat;
+
+	pr_alert("%s: Starting forward-progress test %d\n", __func__, rfp->rcu_fwd_id);
+	if (READ_ONCE(rcu_fwd_emergency_stop))
+		return; /* Get out of the way quickly, no GP wait! */
+	if (!cur_ops->call)
+		return; /* Can't do call_rcu() fwd prog without ->call. */
+
+	/* Loop continuously posting RCU callbacks. */
+	atomic_inc(&rcu_fwd_cb_nodelay);
+	cur_ops->sync(); /* Later readers see above write. */
+	WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
+	stopat = rfp->rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
+	n_launders = 0;
+	rfp->n_launders_cb = 0; // Hoist initialization for multi-kthread
+	n_launders_sa = 0;
+	n_max_cbs = 0;
+	n_max_gps = 0;
+	for (i = 0; i < ARRAY_SIZE(rfp->n_launders_hist); i++)
+		rfp->n_launders_hist[i].n_launders = 0;
+	cver = READ_ONCE(rcu_torture_current_version);
+	gps = cur_ops->get_gp_seq();
+	rfp->rcu_launder_gp_seq_start = gps;
+	tick_dep_set_task(current, TICK_DEP_BIT_RCU);
+	while (time_before(jiffies, stopat) &&
+	       !shutdown_time_arrived() &&
+	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
+		rfcp = READ_ONCE(rfp->rcu_fwd_cb_head);
+		rfcpn = NULL;
+		if (rfcp)
+			rfcpn = READ_ONCE(rfcp->rfc_next);
+		if (rfcpn) {
+			if (rfcp->rfc_gps >= MIN_FWD_CB_LAUNDERS &&
+			    ++n_max_gps >= MIN_FWD_CBS_LAUNDERED)
+				break;
+			rfp->rcu_fwd_cb_head = rfcpn;
+			n_launders++;
+			n_launders_sa++;
+		} else if (!cur_ops->cbflood_max || cur_ops->cbflood_max > n_max_cbs) {
+			rfcp = kmalloc(sizeof(*rfcp), GFP_KERNEL);
+			if (WARN_ON_ONCE(!rfcp)) {
+				schedule_timeout_interruptible(1);
+				continue;
+			}
+			n_max_cbs++;
+			n_launders_sa = 0;
+			rfcp->rfc_gps = 0;
+			rfcp->rfc_rfp = rfp;
+		} else {
+			rfcp = NULL;
+		}
+		if (rfcp)
+			cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
+		rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
+		if (tick_nohz_full_enabled()) {
+			local_irq_save(flags);
+			rcu_momentary_dyntick_idle();
+			local_irq_restore(flags);
+		}
+	}
+	stoppedat = jiffies;
+	n_launders_cb_snap = READ_ONCE(rfp->n_launders_cb);
+	cver = READ_ONCE(rcu_torture_current_version) - cver;
+	gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
+	pr_alert("%s: Waiting for CBs: %pS() %d\n", __func__, cur_ops->cb_barrier, rfp->rcu_fwd_id);
+	cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
+	(void)rcu_torture_fwd_prog_cbfree(rfp);
+
+	if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop) &&
+	    !shutdown_time_arrived()) {
+		WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
+		pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n",
+			 __func__,
+			 stoppedat - rfp->rcu_fwd_startat, jiffies - stoppedat,
+			 n_launders + n_max_cbs - n_launders_cb_snap,
+			 n_launders, n_launders_sa,
+			 n_max_gps, n_max_cbs, cver, gps);
+		atomic_long_add(n_max_cbs, &rcu_fwd_max_cbs);
+		mutex_lock(&rcu_fwd_mutex); // Serialize histograms.
+		rcu_torture_fwd_cb_hist(rfp);
+		mutex_unlock(&rcu_fwd_mutex);
+	}
+	schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
+	tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
+	atomic_dec(&rcu_fwd_cb_nodelay);
+}
+
+
+/*
+ * OOM notifier, but this only prints diagnostic information for the
+ * current forward-progress test.
+ */
+static int rcutorture_oom_notify(struct notifier_block *self,
+				 unsigned long notused, void *nfreed)
+{
+	int i;
+	long ncbs;
+	struct rcu_fwd *rfp;
+
+	mutex_lock(&rcu_fwd_mutex);
+	rfp = rcu_fwds;
+	if (!rfp) {
+		mutex_unlock(&rcu_fwd_mutex);
+		return NOTIFY_OK;
+	}
+	WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
+	     __func__);
+	for (i = 0; i < fwd_progress; i++) {
+		rcu_torture_fwd_cb_hist(&rfp[i]);
+		rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rfp[i].rcu_fwd_startat)) / 2);
+	}
+	WRITE_ONCE(rcu_fwd_emergency_stop, true);
+	smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
+	ncbs = 0;
+	for (i = 0; i < fwd_progress; i++)
+		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
+	pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
+	cur_ops->cb_barrier();
+	ncbs = 0;
+	for (i = 0; i < fwd_progress; i++)
+		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
+	pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
+	cur_ops->cb_barrier();
+	ncbs = 0;
+	for (i = 0; i < fwd_progress; i++)
+		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
+	pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
+	smp_mb(); /* Frees before return to avoid redoing OOM. */
+	(*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */
+	pr_info("%s returning after OOM processing.\n", __func__);
+	mutex_unlock(&rcu_fwd_mutex);
+	return NOTIFY_OK;
+}
+
+static struct notifier_block rcutorture_oom_nb = {
+	.notifier_call = rcutorture_oom_notify
+};
+
+/* Carry out grace-period forward-progress testing. */
+static int rcu_torture_fwd_prog(void *args)
+{
+	bool firsttime = true;
+	long max_cbs;
+	int oldnice = task_nice(current);
+	unsigned long oldseq = READ_ONCE(rcu_fwd_seq);
+	struct rcu_fwd *rfp = args;
+	int tested = 0;
+	int tested_tries = 0;
+
+	VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
+	rcu_bind_current_to_nocb();
+	if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST))
+		set_user_nice(current, MAX_NICE);
+	do {
+		if (!rfp->rcu_fwd_id) {
+			schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
+			WRITE_ONCE(rcu_fwd_emergency_stop, false);
+			if (!firsttime) {
+				max_cbs = atomic_long_xchg(&rcu_fwd_max_cbs, 0);
+				pr_alert("%s n_max_cbs: %ld\n", __func__, max_cbs);
+			}
+			firsttime = false;
+			WRITE_ONCE(rcu_fwd_seq, rcu_fwd_seq + 1);
+		} else {
+			while (READ_ONCE(rcu_fwd_seq) == oldseq && !torture_must_stop())
+				schedule_timeout_interruptible(1);
+			oldseq = READ_ONCE(rcu_fwd_seq);
+		}
+		pr_alert("%s: Starting forward-progress test %d\n", __func__, rfp->rcu_fwd_id);
+		if (rcu_inkernel_boot_has_ended() && torture_num_online_cpus() > rfp->rcu_fwd_id)
+			rcu_torture_fwd_prog_cr(rfp);
+		if ((cur_ops->stall_dur && cur_ops->stall_dur() > 0) &&
+		    (!IS_ENABLED(CONFIG_TINY_RCU) ||
+		     (rcu_inkernel_boot_has_ended() &&
+		      torture_num_online_cpus() > rfp->rcu_fwd_id)))
+			rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
+
+		/* Avoid slow periods, better to test when busy. */
+		if (stutter_wait("rcu_torture_fwd_prog"))
+			sched_set_normal(current, oldnice);
+	} while (!torture_must_stop());
+	/* Short runs might not contain a valid forward-progress attempt. */
+	if (!rfp->rcu_fwd_id) {
+		WARN_ON(!tested && tested_tries >= 5);
+		pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
+	}
+	torture_kthread_stopping("rcu_torture_fwd_prog");
+	return 0;
+}
+
+/* If forward-progress checking is requested and feasible, spawn the thread. */
+static int __init rcu_torture_fwd_prog_init(void)
+{
+	int i;
+	int ret = 0;
+	struct rcu_fwd *rfp;
+
+	if (!fwd_progress)
+		return 0; /* Not requested, so don't do it. */
+	if (fwd_progress >= nr_cpu_ids) {
+		VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Limiting fwd_progress to # CPUs.\n");
+		fwd_progress = nr_cpu_ids;
+	} else if (fwd_progress < 0) {
+		fwd_progress = nr_cpu_ids;
+	}
+	if ((!cur_ops->sync && !cur_ops->call) ||
+	    (!cur_ops->cbflood_max && (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0)) ||
+	    cur_ops == &rcu_busted_ops) {
+		VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
+		fwd_progress = 0;
+		return 0;
+	}
+	if (stall_cpu > 0) {
+		VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
+		fwd_progress = 0;
+		if (IS_MODULE(CONFIG_RCU_TORTURE_TEST))
+			return -EINVAL; /* In module, can fail back to user. */
+		WARN_ON(1); /* Make sure rcutorture notices conflict. */
+		return 0;
+	}
+	if (fwd_progress_holdoff <= 0)
+		fwd_progress_holdoff = 1;
+	if (fwd_progress_div <= 0)
+		fwd_progress_div = 4;
+	rfp = kcalloc(fwd_progress, sizeof(*rfp), GFP_KERNEL);
+	fwd_prog_tasks = kcalloc(fwd_progress, sizeof(*fwd_prog_tasks), GFP_KERNEL);
+	if (!rfp || !fwd_prog_tasks) {
+		kfree(rfp);
+		kfree(fwd_prog_tasks);
+		fwd_prog_tasks = NULL;
+		fwd_progress = 0;
+		return -ENOMEM;
+	}
+	for (i = 0; i < fwd_progress; i++) {
+		spin_lock_init(&rfp[i].rcu_fwd_lock);
+		rfp[i].rcu_fwd_cb_tail = &rfp[i].rcu_fwd_cb_head;
+		rfp[i].rcu_fwd_id = i;
+	}
+	mutex_lock(&rcu_fwd_mutex);
+	rcu_fwds = rfp;
+	mutex_unlock(&rcu_fwd_mutex);
+	register_oom_notifier(&rcutorture_oom_nb);
+	for (i = 0; i < fwd_progress; i++) {
+		ret = torture_create_kthread(rcu_torture_fwd_prog, &rcu_fwds[i], fwd_prog_tasks[i]);
+		if (ret) {
+			fwd_progress = i;
+			return ret;
+		}
+	}
+	return 0;
+}
+
+static void rcu_torture_fwd_prog_cleanup(void)
+{
+	int i;
+	struct rcu_fwd *rfp;
+
+	if (!rcu_fwds || !fwd_prog_tasks)
+		return;
+	for (i = 0; i < fwd_progress; i++)
+		torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_tasks[i]);
+	unregister_oom_notifier(&rcutorture_oom_nb);
+	mutex_lock(&rcu_fwd_mutex);
+	rfp = rcu_fwds;
+	rcu_fwds = NULL;
+	mutex_unlock(&rcu_fwd_mutex);
+	kfree(rfp);
+	kfree(fwd_prog_tasks);
+	fwd_prog_tasks = NULL;
+}
+
+/* Callback function for RCU barrier testing. */
+static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
+{
+	atomic_inc(&barrier_cbs_invoked);
+}
+
+/* IPI handler to get callback posted on desired CPU, if online. */
+static void rcu_torture_barrier1cb(void *rcu_void)
+{
+	struct rcu_head *rhp = rcu_void;
+
+	cur_ops->call(rhp, rcu_torture_barrier_cbf);
+}
+
+/* kthread function to register callbacks used to test RCU barriers. */
+static int rcu_torture_barrier_cbs(void *arg)
+{
+	long myid = (long)arg;
+	bool lastphase = false;
+	bool newphase;
+	struct rcu_head rcu;
+
+	init_rcu_head_on_stack(&rcu);
+	VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started");
+	set_user_nice(current, MAX_NICE);
+	do {
+		wait_event(barrier_cbs_wq[myid],
+			   (newphase =
+			    smp_load_acquire(&barrier_phase)) != lastphase ||
+			   torture_must_stop());
+		lastphase = newphase;
+		if (torture_must_stop())
+			break;
+		/*
+		 * The above smp_load_acquire() ensures barrier_phase load
+		 * is ordered before the following ->call().
+		 */
+		if (smp_call_function_single(myid, rcu_torture_barrier1cb,
+					     &rcu, 1)) {
+			// IPI failed, so use direct call from current CPU.
+			cur_ops->call(&rcu, rcu_torture_barrier_cbf);
+		}
+		if (atomic_dec_and_test(&barrier_cbs_count))
+			wake_up(&barrier_wq);
+	} while (!torture_must_stop());
+	if (cur_ops->cb_barrier != NULL)
+		cur_ops->cb_barrier();
+	destroy_rcu_head_on_stack(&rcu);
+	torture_kthread_stopping("rcu_torture_barrier_cbs");
+	return 0;
+}
+
+/* kthread function to drive and coordinate RCU barrier testing. */
+static int rcu_torture_barrier(void *arg)
+{
+	int i;
+
+	VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting");
+	do {
+		atomic_set(&barrier_cbs_invoked, 0);
+		atomic_set(&barrier_cbs_count, n_barrier_cbs);
+		/* Ensure barrier_phase ordered after prior assignments. */
+		smp_store_release(&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 ||
+			   torture_must_stop());
+		if (torture_must_stop())
+			break;
+		n_barrier_attempts++;
+		cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
+		if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
+			n_rcu_torture_barrier_error++;
+			pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
+			       atomic_read(&barrier_cbs_invoked),
+			       n_barrier_cbs);
+			WARN_ON(1);
+			// Wait manually for the remaining callbacks
+			i = 0;
+			do {
+				if (WARN_ON(i++ > HZ))
+					i = INT_MIN;
+				schedule_timeout_interruptible(1);
+				cur_ops->cb_barrier();
+			} while (atomic_read(&barrier_cbs_invoked) !=
+				 n_barrier_cbs &&
+				 !torture_must_stop());
+			smp_mb(); // Can't trust ordering if broken.
+			if (!torture_must_stop())
+				pr_err("Recovered: barrier_cbs_invoked = %d\n",
+				       atomic_read(&barrier_cbs_invoked));
+		} else {
+			n_barrier_successes++;
+		}
+		schedule_timeout_interruptible(HZ / 10);
+	} while (!torture_must_stop());
+	torture_kthread_stopping("rcu_torture_barrier");
+	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 =
+		kcalloc(n_barrier_cbs, sizeof(barrier_cbs_tasks[0]),
+			GFP_KERNEL);
+	barrier_cbs_wq =
+		kcalloc(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]);
+		ret = torture_create_kthread(rcu_torture_barrier_cbs,
+					     (void *)(long)i,
+					     barrier_cbs_tasks[i]);
+		if (ret)
+			return ret;
+	}
+	return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task);
+}
+
+/* Clean up after RCU barrier testing. */
+static void rcu_torture_barrier_cleanup(void)
+{
+	int i;
+
+	torture_stop_kthread(rcu_torture_barrier, barrier_task);
+	if (barrier_cbs_tasks != NULL) {
+		for (i = 0; i < n_barrier_cbs; i++)
+			torture_stop_kthread(rcu_torture_barrier_cbs,
+					     barrier_cbs_tasks[i]);
+		kfree(barrier_cbs_tasks);
+		barrier_cbs_tasks = NULL;
+	}
+	if (barrier_cbs_wq != NULL) {
+		kfree(barrier_cbs_wq);
+		barrier_cbs_wq = NULL;
+	}
+}
+
+static bool rcu_torture_can_boost(void)
+{
+	static int boost_warn_once;
+	int prio;
+
+	if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2)
+		return false;
+	if (!cur_ops->start_gp_poll || !cur_ops->poll_gp_state)
+		return false;
+
+	prio = rcu_get_gp_kthreads_prio();
+	if (!prio)
+		return false;
+
+	if (prio < 2) {
+		if (boost_warn_once == 1)
+			return false;
+
+		pr_alert("%s: WARN: RCU kthread priority too low to test boosting.  Skipping RCU boost test. Try passing rcutree.kthread_prio > 1 on the kernel command line.\n", KBUILD_MODNAME);
+		boost_warn_once = 1;
+		return false;
+	}
+
+	return true;
+}
+
+static bool read_exit_child_stop;
+static bool read_exit_child_stopped;
+static wait_queue_head_t read_exit_wq;
+
+// Child kthread which just does an rcutorture reader and exits.
+static int rcu_torture_read_exit_child(void *trsp_in)
+{
+	struct torture_random_state *trsp = trsp_in;
+
+	set_user_nice(current, MAX_NICE);
+	// Minimize time between reading and exiting.
+	while (!kthread_should_stop())
+		schedule_timeout_uninterruptible(1);
+	(void)rcu_torture_one_read(trsp, -1);
+	return 0;
+}
+
+// Parent kthread which creates and destroys read-exit child kthreads.
+static int rcu_torture_read_exit(void *unused)
+{
+	bool errexit = false;
+	int i;
+	struct task_struct *tsp;
+	DEFINE_TORTURE_RANDOM(trs);
+
+	// Allocate and initialize.
+	set_user_nice(current, MAX_NICE);
+	VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of test");
+
+	// Each pass through this loop does one read-exit episode.
+	do {
+		VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of episode");
+		for (i = 0; i < read_exit_burst; i++) {
+			if (READ_ONCE(read_exit_child_stop))
+				break;
+			stutter_wait("rcu_torture_read_exit");
+			// Spawn child.
+			tsp = kthread_run(rcu_torture_read_exit_child,
+					  &trs, "%s", "rcu_torture_read_exit_child");
+			if (IS_ERR(tsp)) {
+				TOROUT_ERRSTRING("out of memory");
+				errexit = true;
+				break;
+			}
+			cond_resched();
+			kthread_stop(tsp);
+			n_read_exits++;
+		}
+		VERBOSE_TOROUT_STRING("rcu_torture_read_exit: End of episode");
+		rcu_barrier(); // Wait for task_struct free, avoid OOM.
+		i = 0;
+		for (; !errexit && !READ_ONCE(read_exit_child_stop) && i < read_exit_delay; i++)
+			schedule_timeout_uninterruptible(HZ);
+	} while (!errexit && !READ_ONCE(read_exit_child_stop));
+
+	// Clean up and exit.
+	smp_store_release(&read_exit_child_stopped, true); // After reaping.
+	smp_mb(); // Store before wakeup.
+	wake_up(&read_exit_wq);
+	while (!torture_must_stop())
+		schedule_timeout_uninterruptible(1);
+	torture_kthread_stopping("rcu_torture_read_exit");
+	return 0;
+}
+
+static int rcu_torture_read_exit_init(void)
+{
+	if (read_exit_burst <= 0)
+		return 0;
+	init_waitqueue_head(&read_exit_wq);
+	read_exit_child_stop = false;
+	read_exit_child_stopped = false;
+	return torture_create_kthread(rcu_torture_read_exit, NULL,
+				      read_exit_task);
+}
+
+static void rcu_torture_read_exit_cleanup(void)
+{
+	if (!read_exit_task)
+		return;
+	WRITE_ONCE(read_exit_child_stop, true);
+	smp_mb(); // Above write before wait.
+	wait_event(read_exit_wq, smp_load_acquire(&read_exit_child_stopped));
+	torture_stop_kthread(rcutorture_read_exit, read_exit_task);
+}
+
+static enum cpuhp_state rcutor_hp;
+
+static void
+rcu_torture_cleanup(void)
+{
+	int firsttime;
+	int flags = 0;
+	unsigned long gp_seq = 0;
+	int i;
+
+	if (torture_cleanup_begin()) {
+		if (cur_ops->cb_barrier != NULL) {
+			pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier);
+			cur_ops->cb_barrier();
+		}
+		rcu_gp_slow_unregister(NULL);
+		return;
+	}
+	if (!cur_ops) {
+		torture_cleanup_end();
+		rcu_gp_slow_unregister(NULL);
+		return;
+	}
+
+	if (cur_ops->gp_kthread_dbg)
+		cur_ops->gp_kthread_dbg();
+	rcu_torture_read_exit_cleanup();
+	rcu_torture_barrier_cleanup();
+	rcu_torture_fwd_prog_cleanup();
+	torture_stop_kthread(rcu_torture_stall, stall_task);
+	torture_stop_kthread(rcu_torture_writer, writer_task);
+
+	if (nocb_tasks) {
+		for (i = 0; i < nrealnocbers; i++)
+			torture_stop_kthread(rcu_nocb_toggle, nocb_tasks[i]);
+		kfree(nocb_tasks);
+		nocb_tasks = NULL;
+	}
+
+	if (reader_tasks) {
+		for (i = 0; i < nrealreaders; i++)
+			torture_stop_kthread(rcu_torture_reader,
+					     reader_tasks[i]);
+		kfree(reader_tasks);
+		reader_tasks = NULL;
+	}
+	kfree(rcu_torture_reader_mbchk);
+	rcu_torture_reader_mbchk = NULL;
+
+	if (fakewriter_tasks) {
+		for (i = 0; i < nfakewriters; i++)
+			torture_stop_kthread(rcu_torture_fakewriter,
+					     fakewriter_tasks[i]);
+		kfree(fakewriter_tasks);
+		fakewriter_tasks = NULL;
+	}
+
+	rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
+	srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
+	pr_alert("%s:  End-test grace-period state: g%ld f%#x total-gps=%ld\n",
+		 cur_ops->name, (long)gp_seq, flags,
+		 rcutorture_seq_diff(gp_seq, start_gp_seq));
+	torture_stop_kthread(rcu_torture_stats, stats_task);
+	torture_stop_kthread(rcu_torture_fqs, fqs_task);
+	if (rcu_torture_can_boost() && rcutor_hp >= 0)
+		cpuhp_remove_state(rcutor_hp);
+
+	/*
+	 * Wait for all RCU callbacks to fire, then do torture-type-specific
+	 * cleanup operations.
+	 */
+	if (cur_ops->cb_barrier != NULL) {
+		pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier);
+		cur_ops->cb_barrier();
+	}
+	if (cur_ops->cleanup != NULL)
+		cur_ops->cleanup();
+
+	rcu_torture_mem_dump_obj();
+
+	rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
+
+	if (err_segs_recorded) {
+		pr_alert("Failure/close-call rcutorture reader segments:\n");
+		if (rt_read_nsegs == 0)
+			pr_alert("\t: No segments recorded!!!\n");
+		firsttime = 1;
+		for (i = 0; i < rt_read_nsegs; i++) {
+			pr_alert("\t%d: %#x ", i, err_segs[i].rt_readstate);
+			if (err_segs[i].rt_delay_jiffies != 0) {
+				pr_cont("%s%ldjiffies", firsttime ? "" : "+",
+					err_segs[i].rt_delay_jiffies);
+				firsttime = 0;
+			}
+			if (err_segs[i].rt_delay_ms != 0) {
+				pr_cont("%s%ldms", firsttime ? "" : "+",
+					err_segs[i].rt_delay_ms);
+				firsttime = 0;
+			}
+			if (err_segs[i].rt_delay_us != 0) {
+				pr_cont("%s%ldus", firsttime ? "" : "+",
+					err_segs[i].rt_delay_us);
+				firsttime = 0;
+			}
+			pr_cont("%s\n",
+				err_segs[i].rt_preempted ? "preempted" : "");
+
+		}
+	}
+	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 (torture_onoff_failures())
+		rcu_torture_print_module_parms(cur_ops,
+					       "End of test: RCU_HOTPLUG");
+	else
+		rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
+	torture_cleanup_end();
+	rcu_gp_slow_unregister(&rcu_fwd_cb_nodelay);
+}
+
+#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("%s: duplicated callback was invoked.\n", KBUILD_MODNAME);
+}
+#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;
+	struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
+
+	init_rcu_head_on_stack(&rh1);
+	init_rcu_head_on_stack(&rh2);
+	pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME);
+
+	/* 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. */
+	if (rhp) {
+		call_rcu(rhp, rcu_torture_leak_cb);
+		call_rcu(rhp, rcu_torture_err_cb); /* Another 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("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
+	destroy_rcu_head_on_stack(&rh1);
+	destroy_rcu_head_on_stack(&rh2);
+	kfree(rhp);
+#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+	pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
+#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+}
+
+static void rcutorture_sync(void)
+{
+	static unsigned long n;
+
+	if (cur_ops->sync && !(++n & 0xfff))
+		cur_ops->sync();
+}
+
+static int __init
+rcu_torture_init(void)
+{
+	long i;
+	int cpu;
+	int firsterr = 0;
+	int flags = 0;
+	unsigned long gp_seq = 0;
+	static struct rcu_torture_ops *torture_ops[] = {
+		&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops, &busted_srcud_ops,
+		TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
+		&trivial_ops,
+	};
+
+	if (!torture_init_begin(torture_type, verbose))
+		return -EBUSY;
+
+	/* 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_cont(" %s", torture_ops[i]->name);
+		pr_cont("\n");
+		firsterr = -EINVAL;
+		cur_ops = NULL;
+		goto unwind;
+	}
+	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();
+
+	if (nreaders >= 0) {
+		nrealreaders = nreaders;
+	} else {
+		nrealreaders = num_online_cpus() - 2 - nreaders;
+		if (nrealreaders <= 0)
+			nrealreaders = 1;
+	}
+	rcu_torture_print_module_parms(cur_ops, "Start of test");
+	rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
+	srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
+	start_gp_seq = gp_seq;
+	pr_alert("%s:  Start-test grace-period state: g%ld f%#x\n",
+		 cur_ops->name, (long)gp_seq, flags);
+
+	/* 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_mbchk_fail, 0);
+	atomic_set(&n_rcu_torture_mbchk_tries, 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;
+		}
+	}
+	err_segs_recorded = 0;
+	rt_read_nsegs = 0;
+
+	/* Start up the kthreads. */
+
+	rcu_torture_write_types();
+	firsterr = torture_create_kthread(rcu_torture_writer, NULL,
+					  writer_task);
+	if (torture_init_error(firsterr))
+		goto unwind;
+	if (nfakewriters > 0) {
+		fakewriter_tasks = kcalloc(nfakewriters,
+					   sizeof(fakewriter_tasks[0]),
+					   GFP_KERNEL);
+		if (fakewriter_tasks == NULL) {
+			TOROUT_ERRSTRING("out of memory");
+			firsterr = -ENOMEM;
+			goto unwind;
+		}
+	}
+	for (i = 0; i < nfakewriters; i++) {
+		firsterr = torture_create_kthread(rcu_torture_fakewriter,
+						  NULL, fakewriter_tasks[i]);
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+	reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
+			       GFP_KERNEL);
+	rcu_torture_reader_mbchk = kcalloc(nrealreaders, sizeof(*rcu_torture_reader_mbchk),
+					   GFP_KERNEL);
+	if (!reader_tasks || !rcu_torture_reader_mbchk) {
+		TOROUT_ERRSTRING("out of memory");
+		firsterr = -ENOMEM;
+		goto unwind;
+	}
+	for (i = 0; i < nrealreaders; i++) {
+		rcu_torture_reader_mbchk[i].rtc_chkrdr = -1;
+		firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
+						  reader_tasks[i]);
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+	nrealnocbers = nocbs_nthreads;
+	if (WARN_ON(nrealnocbers < 0))
+		nrealnocbers = 1;
+	if (WARN_ON(nocbs_toggle < 0))
+		nocbs_toggle = HZ;
+	if (nrealnocbers > 0) {
+		nocb_tasks = kcalloc(nrealnocbers, sizeof(nocb_tasks[0]), GFP_KERNEL);
+		if (nocb_tasks == NULL) {
+			TOROUT_ERRSTRING("out of memory");
+			firsterr = -ENOMEM;
+			goto unwind;
+		}
+	} else {
+		nocb_tasks = NULL;
+	}
+	for (i = 0; i < nrealnocbers; i++) {
+		firsterr = torture_create_kthread(rcu_nocb_toggle, NULL, nocb_tasks[i]);
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+	if (stat_interval > 0) {
+		firsterr = torture_create_kthread(rcu_torture_stats, NULL,
+						  stats_task);
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+	if (test_no_idle_hz && shuffle_interval > 0) {
+		firsterr = torture_shuffle_init(shuffle_interval * HZ);
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+	if (stutter < 0)
+		stutter = 0;
+	if (stutter) {
+		int t;
+
+		t = cur_ops->stall_dur ? cur_ops->stall_dur() : stutter * HZ;
+		firsterr = torture_stutter_init(stutter * HZ, t);
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+	if (fqs_duration < 0)
+		fqs_duration = 0;
+	if (fqs_duration) {
+		/* Create the fqs thread */
+		firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
+						  fqs_task);
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+	if (test_boost_interval < 1)
+		test_boost_interval = 1;
+	if (test_boost_duration < 2)
+		test_boost_duration = 2;
+	if (rcu_torture_can_boost()) {
+
+		boost_starttime = jiffies + test_boost_interval * HZ;
+
+		firsterr = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "RCU_TORTURE",
+					     rcutorture_booster_init,
+					     rcutorture_booster_cleanup);
+		rcutor_hp = firsterr;
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
+	shutdown_jiffies = jiffies + shutdown_secs * HZ;
+	firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
+	if (torture_init_error(firsterr))
+		goto unwind;
+	firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval,
+				      rcutorture_sync);
+	if (torture_init_error(firsterr))
+		goto unwind;
+	firsterr = rcu_torture_stall_init();
+	if (torture_init_error(firsterr))
+		goto unwind;
+	firsterr = rcu_torture_fwd_prog_init();
+	if (torture_init_error(firsterr))
+		goto unwind;
+	firsterr = rcu_torture_barrier_init();
+	if (torture_init_error(firsterr))
+		goto unwind;
+	firsterr = rcu_torture_read_exit_init();
+	if (torture_init_error(firsterr))
+		goto unwind;
+	if (object_debug)
+		rcu_test_debug_objects();
+	torture_init_end();
+	rcu_gp_slow_register(&rcu_fwd_cb_nodelay);
+	return 0;
+
+unwind:
+	torture_init_end();
+	rcu_torture_cleanup();
+	if (shutdown_secs) {
+		WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
+		kernel_power_off();
+	}
+	return firsterr;
+}
+
+module_init(rcu_torture_init);
+module_exit(rcu_torture_cleanup);