Adding upstream version 6.1.76.upstream/6.1.76upstream

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

1 files changed, 958 insertions, 0 deletions

diff --git a/kernel/torture.c b/kernel/torture.c
new file mode 100644
index 000000000..9266ca168
--- /dev/null
+++ b/kernel/torture.c
@@ -0,0 +1,958 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Common functions for in-kernel torture tests.
+ *
+ * Copyright (C) IBM Corporation, 2014
+ *
+ * Author: Paul E. McKenney <paulmck@linux.ibm.com>
+ *	Based on kernel/rcu/torture.c.
+ */
+
+#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/interrupt.h>
+#include <linux/sched.h>
+#include <linux/sched/clock.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/slab.h>
+#include <linux/trace_clock.h>
+#include <linux/ktime.h>
+#include <asm/byteorder.h>
+#include <linux/torture.h>
+#include "rcu/rcu.h"
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
+
+static bool disable_onoff_at_boot;
+module_param(disable_onoff_at_boot, bool, 0444);
+
+static bool ftrace_dump_at_shutdown;
+module_param(ftrace_dump_at_shutdown, bool, 0444);
+
+static int verbose_sleep_frequency;
+module_param(verbose_sleep_frequency, int, 0444);
+
+static int verbose_sleep_duration = 1;
+module_param(verbose_sleep_duration, int, 0444);
+
+static char *torture_type;
+static int verbose;
+
+/* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
+#define FULLSTOP_DONTSTOP 0	/* Normal operation. */
+#define FULLSTOP_SHUTDOWN 1	/* System shutdown with torture running. */
+#define FULLSTOP_RMMOD    2	/* Normal rmmod of torture. */
+static int fullstop = FULLSTOP_RMMOD;
+static DEFINE_MUTEX(fullstop_mutex);
+
+static atomic_t verbose_sleep_counter;
+
+/*
+ * Sleep if needed from VERBOSE_TOROUT*().
+ */
+void verbose_torout_sleep(void)
+{
+	if (verbose_sleep_frequency > 0 &&
+	    verbose_sleep_duration > 0 &&
+	    !(atomic_inc_return(&verbose_sleep_counter) % verbose_sleep_frequency))
+		schedule_timeout_uninterruptible(verbose_sleep_duration);
+}
+EXPORT_SYMBOL_GPL(verbose_torout_sleep);
+
+/*
+ * Schedule a high-resolution-timer sleep in nanoseconds, with a 32-bit
+ * nanosecond random fuzz.  This function and its friends desynchronize
+ * testing from the timer wheel.
+ */
+int torture_hrtimeout_ns(ktime_t baset_ns, u32 fuzzt_ns, struct torture_random_state *trsp)
+{
+	ktime_t hto = baset_ns;
+
+	if (trsp)
+		hto += (torture_random(trsp) >> 3) % fuzzt_ns;
+	set_current_state(TASK_UNINTERRUPTIBLE);
+	return schedule_hrtimeout(&hto, HRTIMER_MODE_REL);
+}
+EXPORT_SYMBOL_GPL(torture_hrtimeout_ns);
+
+/*
+ * Schedule a high-resolution-timer sleep in microseconds, with a 32-bit
+ * nanosecond (not microsecond!) random fuzz.
+ */
+int torture_hrtimeout_us(u32 baset_us, u32 fuzzt_ns, struct torture_random_state *trsp)
+{
+	ktime_t baset_ns = baset_us * NSEC_PER_USEC;
+
+	return torture_hrtimeout_ns(baset_ns, fuzzt_ns, trsp);
+}
+EXPORT_SYMBOL_GPL(torture_hrtimeout_us);
+
+/*
+ * Schedule a high-resolution-timer sleep in milliseconds, with a 32-bit
+ * microsecond (not millisecond!) random fuzz.
+ */
+int torture_hrtimeout_ms(u32 baset_ms, u32 fuzzt_us, struct torture_random_state *trsp)
+{
+	ktime_t baset_ns = baset_ms * NSEC_PER_MSEC;
+	u32 fuzzt_ns;
+
+	if ((u32)~0U / NSEC_PER_USEC < fuzzt_us)
+		fuzzt_ns = (u32)~0U;
+	else
+		fuzzt_ns = fuzzt_us * NSEC_PER_USEC;
+	return torture_hrtimeout_ns(baset_ns, fuzzt_ns, trsp);
+}
+EXPORT_SYMBOL_GPL(torture_hrtimeout_ms);
+
+/*
+ * Schedule a high-resolution-timer sleep in jiffies, with an
+ * implied one-jiffy random fuzz.  This is intended to replace calls to
+ * schedule_timeout_interruptible() and friends.
+ */
+int torture_hrtimeout_jiffies(u32 baset_j, struct torture_random_state *trsp)
+{
+	ktime_t baset_ns = jiffies_to_nsecs(baset_j);
+
+	return torture_hrtimeout_ns(baset_ns, jiffies_to_nsecs(1), trsp);
+}
+EXPORT_SYMBOL_GPL(torture_hrtimeout_jiffies);
+
+/*
+ * Schedule a high-resolution-timer sleep in milliseconds, with a 32-bit
+ * millisecond (not second!) random fuzz.
+ */
+int torture_hrtimeout_s(u32 baset_s, u32 fuzzt_ms, struct torture_random_state *trsp)
+{
+	ktime_t baset_ns = baset_s * NSEC_PER_SEC;
+	u32 fuzzt_ns;
+
+	if ((u32)~0U / NSEC_PER_MSEC < fuzzt_ms)
+		fuzzt_ns = (u32)~0U;
+	else
+		fuzzt_ns = fuzzt_ms * NSEC_PER_MSEC;
+	return torture_hrtimeout_ns(baset_ns, fuzzt_ns, trsp);
+}
+EXPORT_SYMBOL_GPL(torture_hrtimeout_s);
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Variables for online-offline handling.  Only present if CPU hotplug
+ * is enabled, otherwise does nothing.
+ */
+
+static struct task_struct *onoff_task;
+static long onoff_holdoff;
+static long onoff_interval;
+static torture_ofl_func *onoff_f;
+static long n_offline_attempts;
+static long n_offline_successes;
+static unsigned long sum_offline;
+static int min_offline = -1;
+static int max_offline;
+static long n_online_attempts;
+static long n_online_successes;
+static unsigned long sum_online;
+static int min_online = -1;
+static int max_online;
+
+static int torture_online_cpus = NR_CPUS;
+
+/*
+ * Some torture testing leverages confusion as to the number of online
+ * CPUs.  This function returns the torture-testing view of this number,
+ * which allows torture tests to load-balance appropriately.
+ */
+int torture_num_online_cpus(void)
+{
+	return READ_ONCE(torture_online_cpus);
+}
+EXPORT_SYMBOL_GPL(torture_num_online_cpus);
+
+/*
+ * Attempt to take a CPU offline.  Return false if the CPU is already
+ * offline or if it is not subject to CPU-hotplug operations.  The
+ * caller can detect other failures by looking at the statistics.
+ */
+bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
+		     unsigned long *sum_offl, int *min_offl, int *max_offl)
+{
+	unsigned long delta;
+	int ret;
+	char *s;
+	unsigned long starttime;
+
+	if (!cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
+		return false;
+	if (num_online_cpus() <= 1)
+		return false;  /* Can't offline the last CPU. */
+
+	if (verbose > 1)
+		pr_alert("%s" TORTURE_FLAG
+			 "torture_onoff task: offlining %d\n",
+			 torture_type, cpu);
+	starttime = jiffies;
+	(*n_offl_attempts)++;
+	ret = remove_cpu(cpu);
+	if (ret) {
+		s = "";
+		if (!rcu_inkernel_boot_has_ended() && ret == -EBUSY) {
+			// PCI probe frequently disables hotplug during boot.
+			(*n_offl_attempts)--;
+			s = " (-EBUSY forgiven during boot)";
+		}
+		if (verbose)
+			pr_alert("%s" TORTURE_FLAG
+				 "torture_onoff task: offline %d failed%s: errno %d\n",
+				 torture_type, cpu, s, ret);
+	} else {
+		if (verbose > 1)
+			pr_alert("%s" TORTURE_FLAG
+				 "torture_onoff task: offlined %d\n",
+				 torture_type, cpu);
+		if (onoff_f)
+			onoff_f();
+		(*n_offl_successes)++;
+		delta = jiffies - starttime;
+		*sum_offl += delta;
+		if (*min_offl < 0) {
+			*min_offl = delta;
+			*max_offl = delta;
+		}
+		if (*min_offl > delta)
+			*min_offl = delta;
+		if (*max_offl < delta)
+			*max_offl = delta;
+		WRITE_ONCE(torture_online_cpus, torture_online_cpus - 1);
+		WARN_ON_ONCE(torture_online_cpus <= 0);
+	}
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(torture_offline);
+
+/*
+ * Attempt to bring a CPU online.  Return false if the CPU is already
+ * online or if it is not subject to CPU-hotplug operations.  The
+ * caller can detect other failures by looking at the statistics.
+ */
+bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
+		    unsigned long *sum_onl, int *min_onl, int *max_onl)
+{
+	unsigned long delta;
+	int ret;
+	char *s;
+	unsigned long starttime;
+
+	if (cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
+		return false;
+
+	if (verbose > 1)
+		pr_alert("%s" TORTURE_FLAG
+			 "torture_onoff task: onlining %d\n",
+			 torture_type, cpu);
+	starttime = jiffies;
+	(*n_onl_attempts)++;
+	ret = add_cpu(cpu);
+	if (ret) {
+		s = "";
+		if (!rcu_inkernel_boot_has_ended() && ret == -EBUSY) {
+			// PCI probe frequently disables hotplug during boot.
+			(*n_onl_attempts)--;
+			s = " (-EBUSY forgiven during boot)";
+		}
+		if (verbose)
+			pr_alert("%s" TORTURE_FLAG
+				 "torture_onoff task: online %d failed%s: errno %d\n",
+				 torture_type, cpu, s, ret);
+	} else {
+		if (verbose > 1)
+			pr_alert("%s" TORTURE_FLAG
+				 "torture_onoff task: onlined %d\n",
+				 torture_type, cpu);
+		(*n_onl_successes)++;
+		delta = jiffies - starttime;
+		*sum_onl += delta;
+		if (*min_onl < 0) {
+			*min_onl = delta;
+			*max_onl = delta;
+		}
+		if (*min_onl > delta)
+			*min_onl = delta;
+		if (*max_onl < delta)
+			*max_onl = delta;
+		WRITE_ONCE(torture_online_cpus, torture_online_cpus + 1);
+	}
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(torture_online);
+
+/*
+ * Get everything online at the beginning and ends of tests.
+ */
+static void torture_online_all(char *phase)
+{
+	int cpu;
+	int ret;
+
+	for_each_possible_cpu(cpu) {
+		if (cpu_online(cpu))
+			continue;
+		ret = add_cpu(cpu);
+		if (ret && verbose) {
+			pr_alert("%s" TORTURE_FLAG
+				 "%s: %s online %d: errno %d\n",
+				 __func__, phase, torture_type, cpu, ret);
+		}
+	}
+}
+
+/*
+ * Execute random CPU-hotplug operations at the interval specified
+ * by the onoff_interval.
+ */
+static int
+torture_onoff(void *arg)
+{
+	int cpu;
+	int maxcpu = -1;
+	DEFINE_TORTURE_RANDOM(rand);
+
+	VERBOSE_TOROUT_STRING("torture_onoff task started");
+	for_each_online_cpu(cpu)
+		maxcpu = cpu;
+	WARN_ON(maxcpu < 0);
+	torture_online_all("Initial");
+	if (maxcpu == 0) {
+		VERBOSE_TOROUT_STRING("Only one CPU, so CPU-hotplug testing is disabled");
+		goto stop;
+	}
+
+	if (onoff_holdoff > 0) {
+		VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
+		schedule_timeout_interruptible(onoff_holdoff);
+		VERBOSE_TOROUT_STRING("torture_onoff end holdoff");
+	}
+	while (!torture_must_stop()) {
+		if (disable_onoff_at_boot && !rcu_inkernel_boot_has_ended()) {
+			schedule_timeout_interruptible(HZ / 10);
+			continue;
+		}
+		cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
+		if (!torture_offline(cpu,
+				     &n_offline_attempts, &n_offline_successes,
+				     &sum_offline, &min_offline, &max_offline))
+			torture_online(cpu,
+				       &n_online_attempts, &n_online_successes,
+				       &sum_online, &min_online, &max_online);
+		schedule_timeout_interruptible(onoff_interval);
+	}
+
+stop:
+	torture_kthread_stopping("torture_onoff");
+	torture_online_all("Final");
+	return 0;
+}
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+
+/*
+ * Initiate online-offline handling.
+ */
+int torture_onoff_init(long ooholdoff, long oointerval, torture_ofl_func *f)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+	onoff_holdoff = ooholdoff;
+	onoff_interval = oointerval;
+	onoff_f = f;
+	if (onoff_interval <= 0)
+		return 0;
+	return torture_create_kthread(torture_onoff, NULL, onoff_task);
+#else /* #ifdef CONFIG_HOTPLUG_CPU */
+	return 0;
+#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
+}
+EXPORT_SYMBOL_GPL(torture_onoff_init);
+
+/*
+ * Clean up after online/offline testing.
+ */
+static void torture_onoff_cleanup(void)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+	if (onoff_task == NULL)
+		return;
+	VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
+	kthread_stop(onoff_task);
+	onoff_task = NULL;
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+}
+
+/*
+ * Print online/offline testing statistics.
+ */
+void torture_onoff_stats(void)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+	pr_cont("onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
+		n_online_successes, n_online_attempts,
+		n_offline_successes, n_offline_attempts,
+		min_online, max_online,
+		min_offline, max_offline,
+		sum_online, sum_offline, HZ);
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+}
+EXPORT_SYMBOL_GPL(torture_onoff_stats);
+
+/*
+ * Were all the online/offline operations successful?
+ */
+bool torture_onoff_failures(void)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+	return n_online_successes != n_online_attempts ||
+	       n_offline_successes != n_offline_attempts;
+#else /* #ifdef CONFIG_HOTPLUG_CPU */
+	return false;
+#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
+}
+EXPORT_SYMBOL_GPL(torture_onoff_failures);
+
+#define TORTURE_RANDOM_MULT	39916801  /* prime */
+#define TORTURE_RANDOM_ADD	479001701 /* prime */
+#define TORTURE_RANDOM_REFRESH	10000
+
+/*
+ * Crude but fast random-number generator.  Uses a linear congruential
+ * generator, with occasional help from cpu_clock().
+ */
+unsigned long
+torture_random(struct torture_random_state *trsp)
+{
+	if (--trsp->trs_count < 0) {
+		trsp->trs_state += (unsigned long)local_clock();
+		trsp->trs_count = TORTURE_RANDOM_REFRESH;
+	}
+	trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
+		TORTURE_RANDOM_ADD;
+	return swahw32(trsp->trs_state);
+}
+EXPORT_SYMBOL_GPL(torture_random);
+
+/*
+ * Variables for shuffling.  The idea is to ensure that each CPU stays
+ * idle for an extended period to test interactions with dyntick idle,
+ * as well as interactions with any per-CPU variables.
+ */
+struct shuffle_task {
+	struct list_head st_l;
+	struct task_struct *st_t;
+};
+
+static long shuffle_interval;	/* In jiffies. */
+static struct task_struct *shuffler_task;
+static cpumask_var_t shuffle_tmp_mask;
+static int shuffle_idle_cpu;	/* Force all torture tasks off this CPU */
+static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
+static DEFINE_MUTEX(shuffle_task_mutex);
+
+/*
+ * Register a task to be shuffled.  If there is no memory, just splat
+ * and don't bother registering.
+ */
+void torture_shuffle_task_register(struct task_struct *tp)
+{
+	struct shuffle_task *stp;
+
+	if (WARN_ON_ONCE(tp == NULL))
+		return;
+	stp = kmalloc(sizeof(*stp), GFP_KERNEL);
+	if (WARN_ON_ONCE(stp == NULL))
+		return;
+	stp->st_t = tp;
+	mutex_lock(&shuffle_task_mutex);
+	list_add(&stp->st_l, &shuffle_task_list);
+	mutex_unlock(&shuffle_task_mutex);
+}
+EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
+
+/*
+ * Unregister all tasks, for example, at the end of the torture run.
+ */
+static void torture_shuffle_task_unregister_all(void)
+{
+	struct shuffle_task *stp;
+	struct shuffle_task *p;
+
+	mutex_lock(&shuffle_task_mutex);
+	list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
+		list_del(&stp->st_l);
+		kfree(stp);
+	}
+	mutex_unlock(&shuffle_task_mutex);
+}
+
+/* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
+ * A special case is when shuffle_idle_cpu = -1, in which case we allow
+ * the tasks to run on all CPUs.
+ */
+static void torture_shuffle_tasks(void)
+{
+	struct shuffle_task *stp;
+
+	cpumask_setall(shuffle_tmp_mask);
+	cpus_read_lock();
+
+	/* No point in shuffling if there is only one online CPU (ex: UP) */
+	if (num_online_cpus() == 1) {
+		cpus_read_unlock();
+		return;
+	}
+
+	/* Advance to the next CPU.  Upon overflow, don't idle any CPUs. */
+	shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
+	if (shuffle_idle_cpu >= nr_cpu_ids)
+		shuffle_idle_cpu = -1;
+	else
+		cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
+
+	mutex_lock(&shuffle_task_mutex);
+	list_for_each_entry(stp, &shuffle_task_list, st_l)
+		set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
+	mutex_unlock(&shuffle_task_mutex);
+
+	cpus_read_unlock();
+}
+
+/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
+ * system to become idle at a time and cut off its timer ticks. This is meant
+ * to test the support for such tickless idle CPU in RCU.
+ */
+static int torture_shuffle(void *arg)
+{
+	VERBOSE_TOROUT_STRING("torture_shuffle task started");
+	do {
+		schedule_timeout_interruptible(shuffle_interval);
+		torture_shuffle_tasks();
+		torture_shutdown_absorb("torture_shuffle");
+	} while (!torture_must_stop());
+	torture_kthread_stopping("torture_shuffle");
+	return 0;
+}
+
+/*
+ * Start the shuffler, with shuffint in jiffies.
+ */
+int torture_shuffle_init(long shuffint)
+{
+	shuffle_interval = shuffint;
+
+	shuffle_idle_cpu = -1;
+
+	if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
+		TOROUT_ERRSTRING("Failed to alloc mask");
+		return -ENOMEM;
+	}
+
+	/* Create the shuffler thread */
+	return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
+}
+EXPORT_SYMBOL_GPL(torture_shuffle_init);
+
+/*
+ * Stop the shuffling.
+ */
+static void torture_shuffle_cleanup(void)
+{
+	torture_shuffle_task_unregister_all();
+	if (shuffler_task) {
+		VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
+		kthread_stop(shuffler_task);
+		free_cpumask_var(shuffle_tmp_mask);
+	}
+	shuffler_task = NULL;
+}
+
+/*
+ * Variables for auto-shutdown.  This allows "lights out" torture runs
+ * to be fully scripted.
+ */
+static struct task_struct *shutdown_task;
+static ktime_t shutdown_time;		/* time to system shutdown. */
+static void (*torture_shutdown_hook)(void);
+
+/*
+ * Absorb kthreads into a kernel function that won't return, so that
+ * they won't ever access module text or data again.
+ */
+void torture_shutdown_absorb(const char *title)
+{
+	while (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
+		pr_notice("torture thread %s parking due to system shutdown\n",
+			  title);
+		schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
+	}
+}
+EXPORT_SYMBOL_GPL(torture_shutdown_absorb);
+
+/*
+ * Cause the torture test to shutdown the system after the test has
+ * run for the time specified by the shutdown_secs parameter.
+ */
+static int torture_shutdown(void *arg)
+{
+	ktime_t ktime_snap;
+
+	VERBOSE_TOROUT_STRING("torture_shutdown task started");
+	ktime_snap = ktime_get();
+	while (ktime_before(ktime_snap, shutdown_time) &&
+	       !torture_must_stop()) {
+		if (verbose)
+			pr_alert("%s" TORTURE_FLAG
+				 "torture_shutdown task: %llu ms remaining\n",
+				 torture_type,
+				 ktime_ms_delta(shutdown_time, ktime_snap));
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule_hrtimeout(&shutdown_time, HRTIMER_MODE_ABS);
+		ktime_snap = ktime_get();
+	}
+	if (torture_must_stop()) {
+		torture_kthread_stopping("torture_shutdown");
+		return 0;
+	}
+
+	/* OK, shut down the system. */
+
+	VERBOSE_TOROUT_STRING("torture_shutdown task shutting down system");
+	shutdown_task = NULL;	/* Avoid self-kill deadlock. */
+	if (torture_shutdown_hook)
+		torture_shutdown_hook();
+	else
+		VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
+	if (ftrace_dump_at_shutdown)
+		rcu_ftrace_dump(DUMP_ALL);
+	kernel_power_off();	/* Shut down the system. */
+	return 0;
+}
+
+/*
+ * Start up the shutdown task.
+ */
+int torture_shutdown_init(int ssecs, void (*cleanup)(void))
+{
+	torture_shutdown_hook = cleanup;
+	if (ssecs > 0) {
+		shutdown_time = ktime_add(ktime_get(), ktime_set(ssecs, 0));
+		return torture_create_kthread(torture_shutdown, NULL,
+					     shutdown_task);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(torture_shutdown_init);
+
+/*
+ * Detect and respond to a system shutdown.
+ */
+static int torture_shutdown_notify(struct notifier_block *unused1,
+				   unsigned long unused2, void *unused3)
+{
+	mutex_lock(&fullstop_mutex);
+	if (READ_ONCE(fullstop) == FULLSTOP_DONTSTOP) {
+		VERBOSE_TOROUT_STRING("Unscheduled system shutdown detected");
+		WRITE_ONCE(fullstop, FULLSTOP_SHUTDOWN);
+	} else {
+		pr_warn("Concurrent rmmod and shutdown illegal!\n");
+	}
+	mutex_unlock(&fullstop_mutex);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block torture_shutdown_nb = {
+	.notifier_call = torture_shutdown_notify,
+};
+
+/*
+ * Shut down the shutdown task.  Say what???  Heh!  This can happen if
+ * the torture module gets an rmmod before the shutdown time arrives.  ;-)
+ */
+static void torture_shutdown_cleanup(void)
+{
+	unregister_reboot_notifier(&torture_shutdown_nb);
+	if (shutdown_task != NULL) {
+		VERBOSE_TOROUT_STRING("Stopping torture_shutdown task");
+		kthread_stop(shutdown_task);
+	}
+	shutdown_task = NULL;
+}
+
+/*
+ * Variables for stuttering, which means to periodically pause and
+ * restart testing in order to catch bugs that appear when load is
+ * suddenly applied to or removed from the system.
+ */
+static struct task_struct *stutter_task;
+static int stutter_pause_test;
+static int stutter;
+static int stutter_gap;
+
+/*
+ * Block until the stutter interval ends.  This must be called periodically
+ * by all running kthreads that need to be subject to stuttering.
+ */
+bool stutter_wait(const char *title)
+{
+	unsigned int i = 0;
+	bool ret = false;
+	int spt;
+
+	cond_resched_tasks_rcu_qs();
+	spt = READ_ONCE(stutter_pause_test);
+	for (; spt; spt = READ_ONCE(stutter_pause_test)) {
+		if (!ret) {
+			sched_set_normal(current, MAX_NICE);
+			ret = true;
+		}
+		if (spt == 1) {
+			schedule_timeout_interruptible(1);
+		} else if (spt == 2) {
+			while (READ_ONCE(stutter_pause_test)) {
+				if (!(i++ & 0xffff))
+					torture_hrtimeout_us(10, 0, NULL);
+				cond_resched();
+			}
+		} else {
+			schedule_timeout_interruptible(round_jiffies_relative(HZ));
+		}
+		torture_shutdown_absorb(title);
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(stutter_wait);
+
+/*
+ * Cause the torture test to "stutter", starting and stopping all
+ * threads periodically.
+ */
+static int torture_stutter(void *arg)
+{
+	DEFINE_TORTURE_RANDOM(rand);
+	int wtime;
+
+	VERBOSE_TOROUT_STRING("torture_stutter task started");
+	do {
+		if (!torture_must_stop() && stutter > 1) {
+			wtime = stutter;
+			if (stutter > 2) {
+				WRITE_ONCE(stutter_pause_test, 1);
+				wtime = stutter - 3;
+				torture_hrtimeout_jiffies(wtime, &rand);
+				wtime = 2;
+			}
+			WRITE_ONCE(stutter_pause_test, 2);
+			torture_hrtimeout_jiffies(wtime, NULL);
+		}
+		WRITE_ONCE(stutter_pause_test, 0);
+		if (!torture_must_stop())
+			torture_hrtimeout_jiffies(stutter_gap, NULL);
+		torture_shutdown_absorb("torture_stutter");
+	} while (!torture_must_stop());
+	torture_kthread_stopping("torture_stutter");
+	return 0;
+}
+
+/*
+ * Initialize and kick off the torture_stutter kthread.
+ */
+int torture_stutter_init(const int s, const int sgap)
+{
+	stutter = s;
+	stutter_gap = sgap;
+	return torture_create_kthread(torture_stutter, NULL, stutter_task);
+}
+EXPORT_SYMBOL_GPL(torture_stutter_init);
+
+/*
+ * Cleanup after the torture_stutter kthread.
+ */
+static void torture_stutter_cleanup(void)
+{
+	if (!stutter_task)
+		return;
+	VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
+	kthread_stop(stutter_task);
+	stutter_task = NULL;
+}
+
+/*
+ * Initialize torture module.  Please note that this is -not- invoked via
+ * the usual module_init() mechanism, but rather by an explicit call from
+ * the client torture module.  This call must be paired with a later
+ * torture_init_end().
+ *
+ * The runnable parameter points to a flag that controls whether or not
+ * the test is currently runnable.  If there is no such flag, pass in NULL.
+ */
+bool torture_init_begin(char *ttype, int v)
+{
+	mutex_lock(&fullstop_mutex);
+	if (torture_type != NULL) {
+		pr_alert("%s: Refusing %s init: %s running.\n",
+			  __func__, ttype, torture_type);
+		pr_alert("%s: One torture test at a time!\n", __func__);
+		mutex_unlock(&fullstop_mutex);
+		return false;
+	}
+	torture_type = ttype;
+	verbose = v;
+	fullstop = FULLSTOP_DONTSTOP;
+	return true;
+}
+EXPORT_SYMBOL_GPL(torture_init_begin);
+
+/*
+ * Tell the torture module that initialization is complete.
+ */
+void torture_init_end(void)
+{
+	mutex_unlock(&fullstop_mutex);
+	register_reboot_notifier(&torture_shutdown_nb);
+}
+EXPORT_SYMBOL_GPL(torture_init_end);
+
+/*
+ * Clean up torture module.  Please note that this is -not- invoked via
+ * the usual module_exit() mechanism, but rather by an explicit call from
+ * the client torture module.  Returns true if a race with system shutdown
+ * is detected, otherwise, all kthreads started by functions in this file
+ * will be shut down.
+ *
+ * This must be called before the caller starts shutting down its own
+ * kthreads.
+ *
+ * Both torture_cleanup_begin() and torture_cleanup_end() must be paired,
+ * in order to correctly perform the cleanup. They are separated because
+ * threads can still need to reference the torture_type type, thus nullify
+ * only after completing all other relevant calls.
+ */
+bool torture_cleanup_begin(void)
+{
+	mutex_lock(&fullstop_mutex);
+	if (READ_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
+		pr_warn("Concurrent rmmod and shutdown illegal!\n");
+		mutex_unlock(&fullstop_mutex);
+		schedule_timeout_uninterruptible(10);
+		return true;
+	}
+	WRITE_ONCE(fullstop, FULLSTOP_RMMOD);
+	mutex_unlock(&fullstop_mutex);
+	torture_shutdown_cleanup();
+	torture_shuffle_cleanup();
+	torture_stutter_cleanup();
+	torture_onoff_cleanup();
+	return false;
+}
+EXPORT_SYMBOL_GPL(torture_cleanup_begin);
+
+void torture_cleanup_end(void)
+{
+	mutex_lock(&fullstop_mutex);
+	torture_type = NULL;
+	mutex_unlock(&fullstop_mutex);
+}
+EXPORT_SYMBOL_GPL(torture_cleanup_end);
+
+/*
+ * Is it time for the current torture test to stop?
+ */
+bool torture_must_stop(void)
+{
+	return torture_must_stop_irq() || kthread_should_stop();
+}
+EXPORT_SYMBOL_GPL(torture_must_stop);
+
+/*
+ * Is it time for the current torture test to stop?  This is the irq-safe
+ * version, hence no check for kthread_should_stop().
+ */
+bool torture_must_stop_irq(void)
+{
+	return READ_ONCE(fullstop) != FULLSTOP_DONTSTOP;
+}
+EXPORT_SYMBOL_GPL(torture_must_stop_irq);
+
+/*
+ * Each kthread must wait for kthread_should_stop() before returning from
+ * its top-level function, otherwise segfaults ensue.  This function
+ * prints a "stopping" message and waits for kthread_should_stop(), and
+ * should be called from all torture kthreads immediately prior to
+ * returning.
+ */
+void torture_kthread_stopping(char *title)
+{
+	char buf[128];
+
+	snprintf(buf, sizeof(buf), "%s is stopping", title);
+	VERBOSE_TOROUT_STRING(buf);
+	while (!kthread_should_stop()) {
+		torture_shutdown_absorb(title);
+		schedule_timeout_uninterruptible(HZ / 20);
+	}
+}
+EXPORT_SYMBOL_GPL(torture_kthread_stopping);
+
+/*
+ * Create a generic torture kthread that is immediately runnable.  If you
+ * need the kthread to be stopped so that you can do something to it before
+ * it starts, you will need to open-code your own.
+ */
+int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
+			    char *f, struct task_struct **tp)
+{
+	int ret = 0;
+
+	VERBOSE_TOROUT_STRING(m);
+	*tp = kthread_create(fn, arg, "%s", s);
+	if (IS_ERR(*tp)) {
+		ret = PTR_ERR(*tp);
+		TOROUT_ERRSTRING(f);
+		*tp = NULL;
+		return ret;
+	}
+	wake_up_process(*tp);  // Process is sleeping, so ordering provided.
+	torture_shuffle_task_register(*tp);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(_torture_create_kthread);
+
+/*
+ * Stop a generic kthread, emitting a message.
+ */
+void _torture_stop_kthread(char *m, struct task_struct **tp)
+{
+	if (*tp == NULL)
+		return;
+	VERBOSE_TOROUT_STRING(m);
+	kthread_stop(*tp);
+	*tp = NULL;
+}
+EXPORT_SYMBOL_GPL(_torture_stop_kthread);