[linux-block.git] / kernel / torture.c

/*
 * Common functions for in-kernel torture tests.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you can access it online at
 * http://www.gnu.org/licenses/gpl-2.0.html.
 *
 * Copyright (C) IBM Corporation, 2014
 *
 * Author: Paul E. McKenney <paulmck@us.ibm.com>
 *	Based on kernel/rcu/torture.c.
 */
#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/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 <asm/byteorder.h>
#include <linux/torture.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com>");

int fullstop = FULLSTOP_RMMOD;
EXPORT_SYMBOL_GPL(fullstop);
DEFINE_MUTEX(fullstop_mutex);
EXPORT_SYMBOL_GPL(fullstop_mutex);

#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 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;

/*
 * Execute random CPU-hotplug operations at the interval specified
 * by the onoff_interval.
 */
static int
torture_onoff(void *arg)
{
	int cpu;
	unsigned long delta;
	int maxcpu = -1;
	DEFINE_TORTURE_RANDOM(rand);
	int ret;
	unsigned long starttime;

	VERBOSE_TOROUT_STRING("torture_onoff task started");
	for_each_online_cpu(cpu)
		maxcpu = cpu;
	WARN_ON(maxcpu < 0);
	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()) {
		cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
		if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {
			if (verbose)
				pr_alert("%s" TORTURE_FLAG
					 "torture_onoff task: offlining %d\n",
					 torture_type, cpu);
			starttime = jiffies;
			n_offline_attempts++;
			ret = cpu_down(cpu);
			if (ret) {
				if (verbose)
					pr_alert("%s" TORTURE_FLAG
						 "torture_onoff task: offline %d failed: errno %d\n",
						 torture_type, cpu, ret);
			} else {
				if (verbose)
					pr_alert("%s" TORTURE_FLAG
						 "torture_onoff task: offlined %d\n",
						 torture_type, cpu);
				n_offline_successes++;
				delta = jiffies - starttime;
				sum_offline += delta;
				if (min_offline < 0) {
					min_offline = delta;
					max_offline = delta;
				}
				if (min_offline > delta)
					min_offline = delta;
				if (max_offline < delta)
					max_offline = delta;
			}
		} else if (cpu_is_hotpluggable(cpu)) {
			if (verbose)
				pr_alert("%s" TORTURE_FLAG
					 "torture_onoff task: onlining %d\n",
					 torture_type, cpu);
			starttime = jiffies;
			n_online_attempts++;
			ret = cpu_up(cpu);
			if (ret) {
				if (verbose)
					pr_alert("%s" TORTURE_FLAG
						 "torture_onoff task: online %d failed: errno %d\n",
						 torture_type, cpu, ret);
			} else {
				if (verbose)
					pr_alert("%s" TORTURE_FLAG
						 "torture_onoff task: onlined %d\n",
						 torture_type, cpu);
				n_online_successes++;
				delta = jiffies - starttime;
				sum_online += delta;
				if (min_online < 0) {
					min_online = delta;
					max_online = delta;
				}
				if (min_online > delta)
					min_online = delta;
				if (max_online < delta)
					max_online = delta;
			}
		}
		schedule_timeout_interruptible(onoff_interval);
	}
	VERBOSE_TOROUT_STRING("torture_onoff task stopping");
	return 0;
}

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

/*
 * Initiate online-offline handling.
 */
int torture_onoff_init(long ooholdoff, long oointerval)
{
#ifdef CONFIG_HOTPLUG_CPU
	int ret;

	onoff_holdoff = ooholdoff;
	onoff_interval = oointerval;
	if (onoff_interval <= 0)
		return 0;
	onoff_task = kthread_run(torture_onoff, NULL, "torture_onoff");
	if (IS_ERR(onoff_task)) {
		ret = PTR_ERR(onoff_task);
		onoff_task = NULL;
		return ret;
	}
	torture_shuffle_task_register(onoff_task);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
	return 0;
}
EXPORT_SYMBOL_GPL(torture_onoff_init);

/*
 * Clean up after online/offline testing.
 */
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 */
}
EXPORT_SYMBOL_GPL(torture_onoff_cleanup);

/*
 * Print online/offline testing statistics.
 */
char *torture_onoff_stats(char *page)
{
#ifdef CONFIG_HOTPLUG_CPU
	page += sprintf(page,
		       "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 */
	return page;
}
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 varibles.
 */
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);
	get_online_cpus();

	/* No point in shuffling if there is only one online CPU (ex: UP) */
	if (num_online_cpus() == 1) {
		put_online_cpus();
		return;
	}

	/* 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;
	if (shuffle_idle_cpu != -1) {
		cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
		if (cpumask_empty(shuffle_tmp_mask)) {
			put_online_cpus();
			return;
		}
	}

	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);

	put_online_cpus();
}

/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 * system to become idle at a time and cut off its timer ticks. This is meant
 * to test the support for such tickless idle CPU in RCU.
 */
static int 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());
	VERBOSE_TOROUT_STRING("torture_shuffle task stopping");
	return 0;
}

/*
 * Start the shuffler, with shuffint in jiffies.
 */
int torture_shuffle_init(long shuffint)
{
	int ret;

	shuffle_interval = shuffint;

	shuffle_idle_cpu = -1;

	if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
		VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
		return -ENOMEM;
	}

	/* Create the shuffler thread */
	shuffler_task = kthread_run(torture_shuffle, NULL, "torture_shuffle");
	if (IS_ERR(shuffler_task)) {
		ret = PTR_ERR(shuffler_task);
		free_cpumask_var(shuffle_tmp_mask);
		VERBOSE_TOROUT_ERRSTRING("Failed to create shuffler");
		shuffler_task = NULL;
		return ret;
	}
	torture_shuffle_task_register(shuffler_task);
	return 0;
}
EXPORT_SYMBOL_GPL(torture_shuffle_init);

/*
 * Stop the shuffling.
 */
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;
}
EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);

/*
 * 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 (ACCESS_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);
Commit	Line	Data
51b1130e PM	1	/*
	2	* Common functions for in-kernel torture tests.
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; if not, you can access it online at
	16	* http://www.gnu.org/licenses/gpl-2.0.html.
	17	*
	18	* Copyright (C) IBM Corporation, 2014
	19	*
	20	* Author: Paul E. McKenney <paulmck@us.ibm.com>
	21	* Based on kernel/rcu/torture.c.
	22	*/
	23	#include <linux/types.h>
	24	#include <linux/kernel.h>
	25	#include <linux/init.h>
	26	#include <linux/module.h>
	27	#include <linux/kthread.h>
	28	#include <linux/err.h>
	29	#include <linux/spinlock.h>
	30	#include <linux/smp.h>
	31	#include <linux/interrupt.h>
	32	#include <linux/sched.h>
	33	#include <linux/atomic.h>
	34	#include <linux/bitops.h>
	35	#include <linux/completion.h>
	36	#include <linux/moduleparam.h>
	37	#include <linux/percpu.h>
	38	#include <linux/notifier.h>
	39	#include <linux/reboot.h>
	40	#include <linux/freezer.h>
	41	#include <linux/cpu.h>
	42	#include <linux/delay.h>
	43	#include <linux/stat.h>
	44	#include <linux/slab.h>
	45	#include <linux/trace_clock.h>
	46	#include <asm/byteorder.h>
	47	#include <linux/torture.h>
	48
	49	MODULE_LICENSE("GPL");
	50	MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com>");
	51
f67a3356 PM	52	int fullstop = FULLSTOP_RMMOD;
	53	EXPORT_SYMBOL_GPL(fullstop);
	54	DEFINE_MUTEX(fullstop_mutex);
	55	EXPORT_SYMBOL_GPL(fullstop_mutex);
	56
2e9e8081 PM	57	#ifdef CONFIG_HOTPLUG_CPU
	58
	59	/*
	60	* Variables for online-offline handling. Only present if CPU hotplug
	61	* is enabled, otherwise does nothing.
	62	*/
	63
	64	static struct task_struct *onoff_task;
	65	static long onoff_holdoff;
	66	static long onoff_interval;
	67	static long n_offline_attempts;
	68	static long n_offline_successes;
	69	static unsigned long sum_offline;
	70	static int min_offline = -1;
	71	static int max_offline;
	72	static long n_online_attempts;
	73	static long n_online_successes;
	74	static unsigned long sum_online;
	75	static int min_online = -1;
	76	static int max_online;
	77
	78	/*
	79	* Execute random CPU-hotplug operations at the interval specified
	80	* by the onoff_interval.
	81	*/
	82	static int
	83	torture_onoff(void *arg)
	84	{
	85	int cpu;
	86	unsigned long delta;
	87	int maxcpu = -1;
	88	DEFINE_TORTURE_RANDOM(rand);
	89	int ret;
	90	unsigned long starttime;
	91
	92	VERBOSE_TOROUT_STRING("torture_onoff task started");
	93	for_each_online_cpu(cpu)
	94	maxcpu = cpu;
	95	WARN_ON(maxcpu < 0);
	96	if (onoff_holdoff > 0) {
	97	VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
	98	schedule_timeout_interruptible(onoff_holdoff);
	99	VERBOSE_TOROUT_STRING("torture_onoff end holdoff");
	100	}
	101	while (!torture_must_stop()) {
	102	cpu = (torture_random(&rand) >> 4) % (maxcpu + 1);
	103	if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {
	104	if (verbose)
	105	pr_alert("%s" TORTURE_FLAG
	106	"torture_onoff task: offlining %d\n",
	107	torture_type, cpu);
	108	starttime = jiffies;
	109	n_offline_attempts++;
	110	ret = cpu_down(cpu);
	111	if (ret) {
	112	if (verbose)
	113	pr_alert("%s" TORTURE_FLAG
	114	"torture_onoff task: offline %d failed: errno %d\n",
	115	torture_type, cpu, ret);
	116	} else {
	117	if (verbose)
	118	pr_alert("%s" TORTURE_FLAG
	119	"torture_onoff task: offlined %d\n",
	120	torture_type, cpu);
121	n_offline_successes++;
122	delta = jiffies - starttime;
123	sum_offline += delta;
124	if (min_offline < 0) {
125	min_offline = delta;
126	max_offline = delta;
127	}
128	if (min_offline > delta)
129	min_offline = delta;
130	if (max_offline < delta)
131	max_offline = delta;
132	}
133	} else if (cpu_is_hotpluggable(cpu)) {
134	if (verbose)
135	pr_alert("%s" TORTURE_FLAG
136	"torture_onoff task: onlining %d\n",
137	torture_type, cpu);
138	starttime = jiffies;
139	n_online_attempts++;
140	ret = cpu_up(cpu);
141	if (ret) {
142	if (verbose)
143	pr_alert("%s" TORTURE_FLAG
144	"torture_onoff task: online %d failed: errno %d\n",
145	torture_type, cpu, ret);
146	} else {
147	if (verbose)
148	pr_alert("%s" TORTURE_FLAG
149	"torture_onoff task: onlined %d\n",
150	torture_type, cpu);
151	n_online_successes++;
152	delta = jiffies - starttime;
153	sum_online += delta;
154	if (min_online < 0) {
155	min_online = delta;
156	max_online = delta;
157	}
158	if (min_online > delta)
159	min_online = delta;
160	if (max_online < delta)
161	max_online = delta;
162	}
163	}
164	schedule_timeout_interruptible(onoff_interval);
165	}
166	VERBOSE_TOROUT_STRING("torture_onoff task stopping");
167	return 0;
168	}
169
170	#endif /* #ifdef CONFIG_HOTPLUG_CPU */
171
172	/*
173	* Initiate online-offline handling.
174	*/
175	int torture_onoff_init(long ooholdoff, long oointerval)
176	{
177	#ifdef CONFIG_HOTPLUG_CPU
178	int ret;
179
180	onoff_holdoff = ooholdoff;
181	onoff_interval = oointerval;
182	if (onoff_interval <= 0)
183	return 0;
184	onoff_task = kthread_run(torture_onoff, NULL, "torture_onoff");
185	if (IS_ERR(onoff_task)) {
186	ret = PTR_ERR(onoff_task);
187	onoff_task = NULL;
188	return ret;
189	}
190	torture_shuffle_task_register(onoff_task);
191	#endif /* #ifdef CONFIG_HOTPLUG_CPU */
192	return 0;
193	}
194	EXPORT_SYMBOL_GPL(torture_onoff_init);
195
196	/*
197	* Clean up after online/offline testing.
198	*/
199	void torture_onoff_cleanup(void)
200	{
201	#ifdef CONFIG_HOTPLUG_CPU
202	if (onoff_task == NULL)
203	return;
204	VERBOSE_TOROUT_STRING("Stopping torture_onoff task");
205	kthread_stop(onoff_task);
206	onoff_task = NULL;
207	#endif /* #ifdef CONFIG_HOTPLUG_CPU */
208	}
209	EXPORT_SYMBOL_GPL(torture_onoff_cleanup);
210
211	/*
212	* Print online/offline testing statistics.
213	*/
214	char torture_onoff_stats(char page)
215	{
216	#ifdef CONFIG_HOTPLUG_CPU
217	page += sprintf(page,
218	"onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
219	n_online_successes, n_online_attempts,
220	n_offline_successes, n_offline_attempts,
221	min_online, max_online,
222	min_offline, max_offline,
223	sum_online, sum_offline, HZ);
224	#endif /* #ifdef CONFIG_HOTPLUG_CPU */
225	return page;
226	}
227	EXPORT_SYMBOL_GPL(torture_onoff_stats);
228
229	/*
230	* Were all the online/offline operations successful?
231	*/
232	bool torture_onoff_failures(void)
233	{
234	#ifdef CONFIG_HOTPLUG_CPU
235	return n_online_successes != n_online_attempts \|\|
236	n_offline_successes != n_offline_attempts;
237	#else /* #ifdef CONFIG_HOTPLUG_CPU */
238	return false;
239	#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
240	}
241	EXPORT_SYMBOL_GPL(torture_onoff_failures);
242
51b1130e PM	243	#define TORTURE_RANDOM_MULT 39916801 /* prime */
	244	#define TORTURE_RANDOM_ADD 479001701 /* prime */
	245	#define TORTURE_RANDOM_REFRESH 10000
	246
	247	/*
	248	* Crude but fast random-number generator. Uses a linear congruential
	249	* generator, with occasional help from cpu_clock().
	250	*/
	251	unsigned long
	252	torture_random(struct torture_random_state *trsp)
	253	{
	254	if (--trsp->trs_count < 0) {
	255	trsp->trs_state += (unsigned long)local_clock();
	256	trsp->trs_count = TORTURE_RANDOM_REFRESH;
	257	}
	258	trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
	259	TORTURE_RANDOM_ADD;
	260	return swahw32(trsp->trs_state);
	261	}
	262	EXPORT_SYMBOL_GPL(torture_random);
f67a3356	263
3808dc9f PM	264	/*
	265	* Variables for shuffling. The idea is to ensure that each CPU stays
	266	* idle for an extended period to test interactions with dyntick idle,
	267	* as well as interactions with any per-CPU varibles.
	268	*/
	269	struct shuffle_task {
	270	struct list_head st_l;
	271	struct task_struct *st_t;
	272	};
	273
	274	static long shuffle_interval; /* In jiffies. */
	275	static struct task_struct *shuffler_task;
	276	static cpumask_var_t shuffle_tmp_mask;
	277	static int shuffle_idle_cpu; /* Force all torture tasks off this CPU */
	278	static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
	279	static DEFINE_MUTEX(shuffle_task_mutex);
	280
	281	/*
	282	* Register a task to be shuffled. If there is no memory, just splat
	283	* and don't bother registering.
	284	*/
	285	void torture_shuffle_task_register(struct task_struct *tp)
	286	{
	287	struct shuffle_task *stp;
	288
	289	if (WARN_ON_ONCE(tp == NULL))
	290	return;
	291	stp = kmalloc(sizeof(*stp), GFP_KERNEL);
	292	if (WARN_ON_ONCE(stp == NULL))
	293	return;
	294	stp->st_t = tp;
	295	mutex_lock(&shuffle_task_mutex);
	296	list_add(&stp->st_l, &shuffle_task_list);
	297	mutex_unlock(&shuffle_task_mutex);
	298	}
	299	EXPORT_SYMBOL_GPL(torture_shuffle_task_register);
	300
	301	/*
	302	* Unregister all tasks, for example, at the end of the torture run.
	303	*/
	304	static void torture_shuffle_task_unregister_all(void)
	305	{
	306	struct shuffle_task *stp;
	307	struct shuffle_task *p;
	308
	309	mutex_lock(&shuffle_task_mutex);
	310	list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
	311	list_del(&stp->st_l);
	312	kfree(stp);
	313	}
	314	mutex_unlock(&shuffle_task_mutex);
	315	}
	316
	317	/* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
	318	* A special case is when shuffle_idle_cpu = -1, in which case we allow
	319	* the tasks to run on all CPUs.
	320	*/
	321	static void torture_shuffle_tasks(void)
	322	{
	323	struct shuffle_task *stp;
	324
	325	cpumask_setall(shuffle_tmp_mask);
	326	get_online_cpus();
	327
328	/* No point in shuffling if there is only one online CPU (ex: UP) */
329	if (num_online_cpus() == 1) {
330	put_online_cpus();
331	return;
332	}
333
334	/* Advance to the next CPU. Upon overflow, don't idle any CPUs. */
335	shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
336	if (shuffle_idle_cpu >= nr_cpu_ids)
337	shuffle_idle_cpu = -1;
338	if (shuffle_idle_cpu != -1) {
339	cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
340	if (cpumask_empty(shuffle_tmp_mask)) {
341	put_online_cpus();
342	return;
343	}
344	}
345
346	mutex_lock(&shuffle_task_mutex);
347	list_for_each_entry(stp, &shuffle_task_list, st_l)
348	set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
349	mutex_unlock(&shuffle_task_mutex);
350
351	put_online_cpus();
352	}
353
354	/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
355	* system to become idle at a time and cut off its timer ticks. This is meant
356	* to test the support for such tickless idle CPU in RCU.
357	*/
358	static int torture_shuffle(void *arg)
359	{
360	VERBOSE_TOROUT_STRING("torture_shuffle task started");
361	do {
362	schedule_timeout_interruptible(shuffle_interval);
363	torture_shuffle_tasks();
364	torture_shutdown_absorb("torture_shuffle");
365	} while (!torture_must_stop());
366	VERBOSE_TOROUT_STRING("torture_shuffle task stopping");
367	return 0;
368	}
369
370	/*
371	* Start the shuffler, with shuffint in jiffies.
372	*/
373	int torture_shuffle_init(long shuffint)
374	{
375	int ret;
376
377	shuffle_interval = shuffint;
378
379	shuffle_idle_cpu = -1;
380
381	if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
382	VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
383	return -ENOMEM;
384	}
385
386	/* Create the shuffler thread */
387	shuffler_task = kthread_run(torture_shuffle, NULL, "torture_shuffle");
388	if (IS_ERR(shuffler_task)) {
389	ret = PTR_ERR(shuffler_task);
390	free_cpumask_var(shuffle_tmp_mask);
391	VERBOSE_TOROUT_ERRSTRING("Failed to create shuffler");
392	shuffler_task = NULL;
393	return ret;
394	}
395	torture_shuffle_task_register(shuffler_task);
396	return 0;
397	}
398	EXPORT_SYMBOL_GPL(torture_shuffle_init);
399
400	/*
401	* Stop the shuffling.
402	*/
403	void torture_shuffle_cleanup(void)
404	{
405	torture_shuffle_task_unregister_all();
406	if (shuffler_task) {
407	VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
408	kthread_stop(shuffler_task);
409	free_cpumask_var(shuffle_tmp_mask);
410	}
411	shuffler_task = NULL;
412	}
413	EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);
414
f67a3356 PM	415	/*
	416	* Absorb kthreads into a kernel function that won't return, so that
	417	* they won't ever access module text or data again.
	418	*/
	419	void torture_shutdown_absorb(const char *title)
	420	{
	421	while (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
	422	pr_notice(
	423	"torture thread %s parking due to system shutdown\n",
	424	title);
	425	schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
	426	}
	427	}
	428	EXPORT_SYMBOL_GPL(torture_shutdown_absorb);