[net-next-2.6.git] / kernel / rcutorture.c

/*
 * Read-Copy Update /proc-based torture test facility
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) IBM Corporation, 2005
 *
 * Authors: Paul E. McKenney <paulmck@us.ibm.com>
 *
 * See also:  Documentation/RCU/torture.txt
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/rcupdate.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <asm/atomic.h>
#include <linux/bitops.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/random.h>
#include <linux/delay.h>
#include <linux/byteorder/swabb.h>
#include <linux/stat.h>

MODULE_LICENSE("GPL");

static int nreaders = -1;	/* # reader threads, defaults to 4*ncpus */
static int stat_interval = 0;	/* Interval between stats, in seconds. */
				/*  Defaults to "only at end of test". */
static int verbose = 0;		/* Print more debug info. */

MODULE_PARM(nreaders, "i");
MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
MODULE_PARM(stat_interval, "i");
MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
MODULE_PARM(verbose, "i");
MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
#define TORTURE_FLAG "rcutorture: "
#define PRINTK_STRING(s) \
	do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
#define VERBOSE_PRINTK_STRING(s) \
	do { if (verbose) printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
#define VERBOSE_PRINTK_ERRSTRING(s) \
	do { if (verbose) printk(KERN_ALERT TORTURE_FLAG "!!! " s "\n"); } while (0)

static char printk_buf[4096];

static int nrealreaders;
static struct task_struct *writer_task;
static struct task_struct **reader_tasks;
static struct task_struct *stats_task;

#define RCU_TORTURE_PIPE_LEN 10

struct rcu_torture {
	struct rcu_head rtort_rcu;
	int rtort_pipe_count;
	struct list_head rtort_free;
	int rtort_mbtest;
};

static int fullstop = 0;	/* stop generating callbacks at test end. */
static LIST_HEAD(rcu_torture_freelist);
static struct rcu_torture *rcu_torture_current = NULL;
static long rcu_torture_current_version = 0;
static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
static DEFINE_SPINLOCK(rcu_torture_lock);
static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
	{ 0 };
static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
	{ 0 };
static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
atomic_t n_rcu_torture_alloc;
atomic_t n_rcu_torture_alloc_fail;
atomic_t n_rcu_torture_free;
atomic_t n_rcu_torture_mberror;
atomic_t n_rcu_torture_error;

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

	spin_lock(&rcu_torture_lock);
	if (list_empty(&rcu_torture_freelist)) {
		atomic_inc(&n_rcu_torture_alloc_fail);
		spin_unlock(&rcu_torture_lock);
		return NULL;
	}
	atomic_inc(&n_rcu_torture_alloc);
	p = rcu_torture_freelist.next;
	list_del_init(p);
	spin_unlock(&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(&rcu_torture_lock);
	list_add_tail(&p->rtort_free, &rcu_torture_freelist);
	spin_unlock(&rcu_torture_lock);
}

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

	if (fullstop) {
		/* Test is ending, just drop callbacks on the floor. */
		/* The next initialization will pick up the pieces. */
		return;
	}
	i = rp->rtort_pipe_count;
	if (i > RCU_TORTURE_PIPE_LEN)
		i = RCU_TORTURE_PIPE_LEN;
	atomic_inc(&rcu_torture_wcount[i]);
	if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
		rp->rtort_mbtest = 0;
		rcu_torture_free(rp);
	} else
		call_rcu(p, rcu_torture_cb);
}

struct rcu_random_state {
	unsigned long rrs_state;
	unsigned long rrs_count;
};

#define RCU_RANDOM_MULT 39916801  /* prime */
#define RCU_RANDOM_ADD	479001701 /* prime */
#define RCU_RANDOM_REFRESH 10000

#define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }

/*
 * Crude but fast random-number generator.  Uses a linear congruential
 * generator, with occasional help from get_random_bytes().
 */
static long
rcu_random(struct rcu_random_state *rrsp)
{
	long refresh;

	if (--rrsp->rrs_count < 0) {
		get_random_bytes(&refresh, sizeof(refresh));
		rrsp->rrs_state += refresh;
		rrsp->rrs_count = RCU_RANDOM_REFRESH;
	}
	rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
	return swahw32(rrsp->rrs_state);
}

/*
 * 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)
{
	int i;
	long oldbatch = rcu_batches_completed();
	struct rcu_torture *rp;
	struct rcu_torture *old_rp;
	static DEFINE_RCU_RANDOM(rand);

	VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
	set_user_nice(current, 19);

	do {
		schedule_timeout_uninterruptible(1);
		if (rcu_batches_completed() == oldbatch)
			continue;
		if ((rp = rcu_torture_alloc()) == NULL)
			continue;
		rp->rtort_pipe_count = 0;
		udelay(rcu_random(&rand) & 0x3ff);
		old_rp = rcu_torture_current;
		rp->rtort_mbtest = 1;
		rcu_assign_pointer(rcu_torture_current, rp);
		smp_wmb();
		if (old_rp != NULL) {
			i = old_rp->rtort_pipe_count;
			if (i > RCU_TORTURE_PIPE_LEN)
				i = RCU_TORTURE_PIPE_LEN;
			atomic_inc(&rcu_torture_wcount[i]);
			old_rp->rtort_pipe_count++;
			call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
		}
		rcu_torture_current_version++;
		oldbatch = rcu_batches_completed();
	} while (!kthread_should_stop() && !fullstop);
	VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
	while (!kthread_should_stop())
		schedule_timeout_uninterruptible(1);
	return 0;
}

/*
 * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
 * incrementing the corresponding element of the pipeline array.  The
 * counter in the element should never be greater than 1, otherwise, the
 * RCU implementation is broken.
 */
static int
rcu_torture_reader(void *arg)
{
	int completed;
	DEFINE_RCU_RANDOM(rand);
	struct rcu_torture *p;
	int pipe_count;

	VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
	set_user_nice(current, 19);

	do {
		rcu_read_lock();
		completed = rcu_batches_completed();
		p = rcu_dereference(rcu_torture_current);
		if (p == NULL) {
			/* Wait for rcu_torture_writer to get underway */
			rcu_read_unlock();
			schedule_timeout_interruptible(HZ);
			continue;
		}
		if (p->rtort_mbtest == 0)
			atomic_inc(&n_rcu_torture_mberror);
		udelay(rcu_random(&rand) & 0x7f);
		preempt_disable();
		pipe_count = p->rtort_pipe_count;
		if (pipe_count > RCU_TORTURE_PIPE_LEN) {
			/* Should not happen, but... */
			pipe_count = RCU_TORTURE_PIPE_LEN;
		}
		++__get_cpu_var(rcu_torture_count)[pipe_count];
		completed = rcu_batches_completed() - completed;
		if (completed > RCU_TORTURE_PIPE_LEN) {
			/* Should not happen, but... */
			completed = RCU_TORTURE_PIPE_LEN;
		}
		++__get_cpu_var(rcu_torture_batch)[completed];
		preempt_enable();
		rcu_read_unlock();
		schedule();
	} while (!kthread_should_stop() && !fullstop);
	VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
	while (!kthread_should_stop())
		schedule_timeout_uninterruptible(1);
	return 0;
}

/*
 * Create an RCU-torture statistics message in the specified buffer.
 */
static int
rcu_torture_printk(char *page)
{
	int cnt = 0;
	int cpu;
	int i;
	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };

	for_each_cpu(cpu) {
		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
			pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
			batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
		}
	}
	for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
		if (pipesummary[i] != 0)
			break;
	}
	cnt += sprintf(&page[cnt], "rcutorture: ");
	cnt += sprintf(&page[cnt],
		       "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
		       "rtmbe: %d",
		       rcu_torture_current,
		       rcu_torture_current_version,
		       list_empty(&rcu_torture_freelist),
		       atomic_read(&n_rcu_torture_alloc),
		       atomic_read(&n_rcu_torture_alloc_fail),
		       atomic_read(&n_rcu_torture_free),
		       atomic_read(&n_rcu_torture_mberror));
	if (atomic_read(&n_rcu_torture_mberror) != 0)
		cnt += sprintf(&page[cnt], " !!!");
	cnt += sprintf(&page[cnt], "\nrcutorture: ");
	if (i > 1) {
		cnt += sprintf(&page[cnt], "!!! ");
		atomic_inc(&n_rcu_torture_error);
	}
	cnt += sprintf(&page[cnt], "Reader Pipe: ");
	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
		cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
	cnt += sprintf(&page[cnt], "\nrcutorture: ");
	cnt += sprintf(&page[cnt], "Reader Batch: ");
	for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++)
		cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
	cnt += sprintf(&page[cnt], "\nrcutorture: ");
	cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
		cnt += sprintf(&page[cnt], " %d",
			       atomic_read(&rcu_torture_wcount[i]));
	}
	cnt += sprintf(&page[cnt], "\n");
	return cnt;
}

/*
 * Print torture statistics.  Caller must ensure that there is only
 * one call to this function at a given time!!!  This is normally
 * accomplished by relying on the module system to only have one copy
 * of the module loaded, and then by giving the rcu_torture_stats
 * kthread full control (or the init/cleanup functions when rcu_torture_stats
 * thread is not running).
 */
static void
rcu_torture_stats_print(void)
{
	int cnt;

	cnt = rcu_torture_printk(printk_buf);
	printk(KERN_ALERT "%s", printk_buf);
}

/*
 * Periodically prints torture statistics, if periodic statistics printing
 * was specified via the stat_interval module parameter.
 *
 * No need to worry about fullstop here, since this one doesn't reference
 * volatile state or register callbacks.
 */
static int
rcu_torture_stats(void *arg)
{
	VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
	do {
		schedule_timeout_interruptible(stat_interval * HZ);
		rcu_torture_stats_print();
	} while (!kthread_should_stop());
	VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
	return 0;
}

static void
rcu_torture_cleanup(void)
{
	int i;

	fullstop = 1;
	if (writer_task != NULL) {
		VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
		kthread_stop(writer_task);
	}
	writer_task = NULL;

	if (reader_tasks != NULL) {
		for (i = 0; i < nrealreaders; i++) {
			if (reader_tasks[i] != NULL) {
				VERBOSE_PRINTK_STRING(
					"Stopping rcu_torture_reader task");
				kthread_stop(reader_tasks[i]);
			}
			reader_tasks[i] = NULL;
		}
		kfree(reader_tasks);
		reader_tasks = NULL;
	}
	rcu_torture_current = NULL;

	if (stats_task != NULL) {
		VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
		kthread_stop(stats_task);
	}
	stats_task = NULL;

	/* Wait for all RCU callbacks to fire.  */
	rcu_barrier();

	rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
	printk(KERN_ALERT TORTURE_FLAG
	       "--- End of test: %s\n",
	       atomic_read(&n_rcu_torture_error) == 0 ? "SUCCESS" : "FAILURE");
}

static int
rcu_torture_init(void)
{
	int i;
	int cpu;
	int firsterr = 0;

	/* Process args and tell the world that the torturer is on the job. */

	if (nreaders >= 0)
		nrealreaders = nreaders;
	else
		nrealreaders = 2 * num_online_cpus();
	printk(KERN_ALERT TORTURE_FLAG
	       "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
	       nrealreaders, stat_interval, verbose);
	fullstop = 0;

	/* Set up the freelist. */

	INIT_LIST_HEAD(&rcu_torture_freelist);
	for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
		rcu_tortures[i].rtort_mbtest = 0;
		list_add_tail(&rcu_tortures[i].rtort_free,
			      &rcu_torture_freelist);
	}

	/* Initialize the statistics so that each run gets its own numbers. */

	rcu_torture_current = NULL;
	rcu_torture_current_version = 0;
	atomic_set(&n_rcu_torture_alloc, 0);
	atomic_set(&n_rcu_torture_alloc_fail, 0);
	atomic_set(&n_rcu_torture_free, 0);
	atomic_set(&n_rcu_torture_mberror, 0);
	atomic_set(&n_rcu_torture_error, 0);
	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
		atomic_set(&rcu_torture_wcount[i], 0);
	for_each_cpu(cpu) {
		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
			per_cpu(rcu_torture_count, cpu)[i] = 0;
			per_cpu(rcu_torture_batch, cpu)[i] = 0;
		}
	}

	/* Start up the kthreads. */

	VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
	writer_task = kthread_run(rcu_torture_writer, NULL,
				  "rcu_torture_writer");
	if (IS_ERR(writer_task)) {
		firsterr = PTR_ERR(writer_task);
		VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
		writer_task = NULL;
		goto unwind;
	}
	reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
			       GFP_KERNEL);
	if (reader_tasks == NULL) {
		VERBOSE_PRINTK_ERRSTRING("out of memory");
		firsterr = -ENOMEM;
		goto unwind;
	}
	for (i = 0; i < nrealreaders; i++) {
		VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
		reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
					      "rcu_torture_reader");
		if (IS_ERR(reader_tasks[i])) {
			firsterr = PTR_ERR(reader_tasks[i]);
			VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
			reader_tasks[i] = NULL;
			goto unwind;
		}
	}
	if (stat_interval > 0) {
		VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
		stats_task = kthread_run(rcu_torture_stats, NULL,
					"rcu_torture_stats");
		if (IS_ERR(stats_task)) {
			firsterr = PTR_ERR(stats_task);
			VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
			stats_task = NULL;
			goto unwind;
		}
	}
	return 0;

unwind:
	rcu_torture_cleanup();
	return firsterr;
}

module_init(rcu_torture_init);
module_exit(rcu_torture_cleanup);
Commit	Line	Data
a241ec65 PM	1	/*
	2	* Read-Copy Update /proc-based torture test facility
	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, write to the Free Software
	16	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	17	*
	18	* Copyright (C) IBM Corporation, 2005
	19	*
	20	* Authors: Paul E. McKenney <paulmck@us.ibm.com>
	21	*
	22	* See also: Documentation/RCU/torture.txt
	23	*/
	24	#include <linux/types.h>
	25	#include <linux/kernel.h>
	26	#include <linux/init.h>
	27	#include <linux/module.h>
	28	#include <linux/kthread.h>
	29	#include <linux/err.h>
	30	#include <linux/spinlock.h>
	31	#include <linux/smp.h>
	32	#include <linux/rcupdate.h>
	33	#include <linux/interrupt.h>
	34	#include <linux/sched.h>
	35	#include <asm/atomic.h>
	36	#include <linux/bitops.h>
	37	#include <linux/module.h>
	38	#include <linux/completion.h>
	39	#include <linux/moduleparam.h>
	40	#include <linux/percpu.h>
	41	#include <linux/notifier.h>
a241ec65 PM	42	#include <linux/cpu.h>
	43	#include <linux/random.h>
	44	#include <linux/delay.h>
	45	#include <linux/byteorder/swabb.h>
	46	#include <linux/stat.h>
	47
	48	MODULE_LICENSE("GPL");
	49
	50	static int nreaders = -1; /* # reader threads, defaults to 4ncpus /
	51	static int stat_interval = 0; /* Interval between stats, in seconds. */
	52	/* Defaults to "only at end of test". */
	53	static int verbose = 0; /* Print more debug info. */
	54
	55	MODULE_PARM(nreaders, "i");
	56	MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
	57	MODULE_PARM(stat_interval, "i");
	58	MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
	59	MODULE_PARM(verbose, "i");
	60	MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
	61	#define TORTURE_FLAG "rcutorture: "
	62	#define PRINTK_STRING(s) \
	63	do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
	64	#define VERBOSE_PRINTK_STRING(s) \
	65	do { if (verbose) printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
	66	#define VERBOSE_PRINTK_ERRSTRING(s) \
	67	do { if (verbose) printk(KERN_ALERT TORTURE_FLAG "!!! " s "\n"); } while (0)
	68
	69	static char printk_buf[4096];
	70
	71	static int nrealreaders;
	72	static struct task_struct *writer_task;
	73	static struct task_struct **reader_tasks;
	74	static struct task_struct *stats_task;
	75
	76	#define RCU_TORTURE_PIPE_LEN 10
	77
	78	struct rcu_torture {
	79	struct rcu_head rtort_rcu;
	80	int rtort_pipe_count;
	81	struct list_head rtort_free;
996417d2	82	int rtort_mbtest;
a241ec65 PM	83	};
	84
	85	static int fullstop = 0; /* stop generating callbacks at test end. */
	86	static LIST_HEAD(rcu_torture_freelist);
	87	static struct rcu_torture *rcu_torture_current = NULL;
	88	static long rcu_torture_current_version = 0;
	89	static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
	90	static DEFINE_SPINLOCK(rcu_torture_lock);
	91	static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
	92	{ 0 };
	93	static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
	94	{ 0 };
	95	static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
	96	atomic_t n_rcu_torture_alloc;
	97	atomic_t n_rcu_torture_alloc_fail;
	98	atomic_t n_rcu_torture_free;
996417d2 PM	99	atomic_t n_rcu_torture_mberror;
996417d2 PM	100	atomic_t n_rcu_torture_error;
a241ec65 PM	101
	102	/*
	103	* Allocate an element from the rcu_tortures pool.
	104	*/
97a41e26	105	static struct rcu_torture *
a241ec65 PM	106	rcu_torture_alloc(void)
	107	{
	108	struct list_head *p;
	109
	110	spin_lock(&rcu_torture_lock);
	111	if (list_empty(&rcu_torture_freelist)) {
	112	atomic_inc(&n_rcu_torture_alloc_fail);
	113	spin_unlock(&rcu_torture_lock);
	114	return NULL;
	115	}
	116	atomic_inc(&n_rcu_torture_alloc);
	117	p = rcu_torture_freelist.next;
	118	list_del_init(p);
	119	spin_unlock(&rcu_torture_lock);
	120	return container_of(p, struct rcu_torture, rtort_free);
	121	}
	122
	123	/*
	124	* Free an element to the rcu_tortures pool.
	125	*/
	126	static void
	127	rcu_torture_free(struct rcu_torture *p)
	128	{
	129	atomic_inc(&n_rcu_torture_free);
	130	spin_lock(&rcu_torture_lock);
	131	list_add_tail(&p->rtort_free, &rcu_torture_freelist);
	132	spin_unlock(&rcu_torture_lock);
	133	}
	134
	135	static void
	136	rcu_torture_cb(struct rcu_head *p)
	137	{
	138	int i;
	139	struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
	140
	141	if (fullstop) {
	142	/* Test is ending, just drop callbacks on the floor. */
	143	/* The next initialization will pick up the pieces. */
	144	return;
	145	}
	146	i = rp->rtort_pipe_count;
	147	if (i > RCU_TORTURE_PIPE_LEN)
	148	i = RCU_TORTURE_PIPE_LEN;
	149	atomic_inc(&rcu_torture_wcount[i]);
996417d2 PM	150	if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
996417d2 PM	151	rp->rtort_mbtest = 0;
a241ec65	152	rcu_torture_free(rp);
996417d2	153	} else
a241ec65 PM	154	call_rcu(p, rcu_torture_cb);
	155	}
	156
	157	struct rcu_random_state {
	158	unsigned long rrs_state;
	159	unsigned long rrs_count;
	160	};
	161
	162	#define RCU_RANDOM_MULT 39916801 /* prime */
	163	#define RCU_RANDOM_ADD 479001701 /* prime */
	164	#define RCU_RANDOM_REFRESH 10000
	165
	166	#define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
	167
	168	/*
	169	* Crude but fast random-number generator. Uses a linear congruential
	170	* generator, with occasional help from get_random_bytes().
	171	*/
	172	static long
	173	rcu_random(struct rcu_random_state *rrsp)
	174	{
	175	long refresh;
	176
	177	if (--rrsp->rrs_count < 0) {
	178	get_random_bytes(&refresh, sizeof(refresh));
	179	rrsp->rrs_state += refresh;
	180	rrsp->rrs_count = RCU_RANDOM_REFRESH;
	181	}
	182	rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
	183	return swahw32(rrsp->rrs_state);
	184	}
	185
	186	/*
	187	* RCU torture writer kthread. Repeatedly substitutes a new structure
	188	* for that pointed to by rcu_torture_current, freeing the old structure
	189	* after a series of grace periods (the "pipeline").
	190	*/
	191	static int
	192	rcu_torture_writer(void *arg)
	193	{
	194	int i;
	195	long oldbatch = rcu_batches_completed();
	196	struct rcu_torture *rp;
	197	struct rcu_torture *old_rp;
	198	static DEFINE_RCU_RANDOM(rand);
	199
	200	VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
dbdf65b1 IM	201	set_user_nice(current, 19);
dbdf65b1 IM	202
a241ec65 PM	203	do {
	204	schedule_timeout_uninterruptible(1);
	205	if (rcu_batches_completed() == oldbatch)
	206	continue;
	207	if ((rp = rcu_torture_alloc()) == NULL)
	208	continue;
	209	rp->rtort_pipe_count = 0;
	210	udelay(rcu_random(&rand) & 0x3ff);
	211	old_rp = rcu_torture_current;
996417d2	212	rp->rtort_mbtest = 1;
a241ec65 PM	213	rcu_assign_pointer(rcu_torture_current, rp);
	214	smp_wmb();
	215	if (old_rp != NULL) {
	216	i = old_rp->rtort_pipe_count;
	217	if (i > RCU_TORTURE_PIPE_LEN)
	218	i = RCU_TORTURE_PIPE_LEN;
	219	atomic_inc(&rcu_torture_wcount[i]);
	220	old_rp->rtort_pipe_count++;
	221	call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
	222	}
	223	rcu_torture_current_version++;
	224	oldbatch = rcu_batches_completed();
	225	} while (!kthread_should_stop() && !fullstop);
	226	VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
	227	while (!kthread_should_stop())
	228	schedule_timeout_uninterruptible(1);
	229	return 0;
	230	}
	231
	232	/*
	233	* RCU torture reader kthread. Repeatedly dereferences rcu_torture_current,
	234	* incrementing the corresponding element of the pipeline array. The
	235	* counter in the element should never be greater than 1, otherwise, the
	236	* RCU implementation is broken.
	237	*/
	238	static int
	239	rcu_torture_reader(void *arg)
	240	{
	241	int completed;
	242	DEFINE_RCU_RANDOM(rand);
	243	struct rcu_torture *p;
	244	int pipe_count;
	245
	246	VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
dbdf65b1 IM	247	set_user_nice(current, 19);
dbdf65b1 IM	248
a241ec65 PM	249	do {
	250	rcu_read_lock();
	251	completed = rcu_batches_completed();
	252	p = rcu_dereference(rcu_torture_current);
	253	if (p == NULL) {
	254	/* Wait for rcu_torture_writer to get underway */
	255	rcu_read_unlock();
	256	schedule_timeout_interruptible(HZ);
	257	continue;
	258	}
996417d2 PM	259	if (p->rtort_mbtest == 0)
996417d2 PM	260	atomic_inc(&n_rcu_torture_mberror);
a241ec65 PM	261	udelay(rcu_random(&rand) & 0x7f);
	262	preempt_disable();
	263	pipe_count = p->rtort_pipe_count;
	264	if (pipe_count > RCU_TORTURE_PIPE_LEN) {
	265	/* Should not happen, but... */
	266	pipe_count = RCU_TORTURE_PIPE_LEN;
	267	}
	268	++__get_cpu_var(rcu_torture_count)[pipe_count];
	269	completed = rcu_batches_completed() - completed;
	270	if (completed > RCU_TORTURE_PIPE_LEN) {
	271	/* Should not happen, but... */
	272	completed = RCU_TORTURE_PIPE_LEN;
	273	}
	274	++__get_cpu_var(rcu_torture_batch)[completed];
	275	preempt_enable();
	276	rcu_read_unlock();
	277	schedule();
	278	} while (!kthread_should_stop() && !fullstop);
	279	VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
	280	while (!kthread_should_stop())
	281	schedule_timeout_uninterruptible(1);
	282	return 0;
	283	}
	284
	285	/*
	286	* Create an RCU-torture statistics message in the specified buffer.
	287	*/
	288	static int
	289	rcu_torture_printk(char *page)
	290	{
	291	int cnt = 0;
	292	int cpu;
	293	int i;
	294	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
	295	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
	296
	297	for_each_cpu(cpu) {
	298	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
	299	pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
	300	batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
	301	}
	302	}
	303	for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
	304	if (pipesummary[i] != 0)
	305	break;
	306	}
	307	cnt += sprintf(&page[cnt], "rcutorture: ");
	308	cnt += sprintf(&page[cnt],
996417d2 PM	309	"rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
996417d2 PM	310	"rtmbe: %d",
a241ec65 PM	311	rcu_torture_current,
	312	rcu_torture_current_version,
	313	list_empty(&rcu_torture_freelist),
	314	atomic_read(&n_rcu_torture_alloc),
	315	atomic_read(&n_rcu_torture_alloc_fail),
996417d2 PM	316	atomic_read(&n_rcu_torture_free),
	317	atomic_read(&n_rcu_torture_mberror));
	318	if (atomic_read(&n_rcu_torture_mberror) != 0)
	319	cnt += sprintf(&page[cnt], " !!!");
a241ec65	320	cnt += sprintf(&page[cnt], "\nrcutorture: ");
996417d2	321	if (i > 1) {
a241ec65	322	cnt += sprintf(&page[cnt], "!!! ");
996417d2 PM	323	atomic_inc(&n_rcu_torture_error);
996417d2 PM	324	}
a241ec65 PM	325	cnt += sprintf(&page[cnt], "Reader Pipe: ");
	326	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
	327	cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
	328	cnt += sprintf(&page[cnt], "\nrcutorture: ");
	329	cnt += sprintf(&page[cnt], "Reader Batch: ");
	330	for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++)
	331	cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
	332	cnt += sprintf(&page[cnt], "\nrcutorture: ");
	333	cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
	334	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
	335	cnt += sprintf(&page[cnt], " %d",
	336	atomic_read(&rcu_torture_wcount[i]));
	337	}
	338	cnt += sprintf(&page[cnt], "\n");
	339	return cnt;
	340	}
	341
	342	/*
	343	* Print torture statistics. Caller must ensure that there is only
	344	* one call to this function at a given time!!! This is normally
	345	* accomplished by relying on the module system to only have one copy
	346	* of the module loaded, and then by giving the rcu_torture_stats
	347	* kthread full control (or the init/cleanup functions when rcu_torture_stats
	348	* thread is not running).
	349	*/
	350	static void
	351	rcu_torture_stats_print(void)
	352	{
	353	int cnt;
	354
	355	cnt = rcu_torture_printk(printk_buf);
	356	printk(KERN_ALERT "%s", printk_buf);
	357	}
	358
	359	/*
	360	* Periodically prints torture statistics, if periodic statistics printing
	361	* was specified via the stat_interval module parameter.
	362	*
	363	* No need to worry about fullstop here, since this one doesn't reference
	364	* volatile state or register callbacks.
	365	*/
	366	static int
	367	rcu_torture_stats(void *arg)
	368	{
	369	VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
	370	do {
	371	schedule_timeout_interruptible(stat_interval * HZ);
	372	rcu_torture_stats_print();
	373	} while (!kthread_should_stop());
	374	VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
	375	return 0;
	376	}
	377
	378	static void
	379	rcu_torture_cleanup(void)
	380	{
	381	int i;
	382
	383	fullstop = 1;
	384	if (writer_task != NULL) {
	385	VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
	386	kthread_stop(writer_task);
	387	}
	388	writer_task = NULL;
389
390	if (reader_tasks != NULL) {
391	for (i = 0; i < nrealreaders; i++) {
392	if (reader_tasks[i] != NULL) {
393	VERBOSE_PRINTK_STRING(
394	"Stopping rcu_torture_reader task");
395	kthread_stop(reader_tasks[i]);
396	}
397	reader_tasks[i] = NULL;
398	}
399	kfree(reader_tasks);
400	reader_tasks = NULL;
401	}
402	rcu_torture_current = NULL;
403
404	if (stats_task != NULL) {
405	VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
406	kthread_stop(stats_task);
407	}
408	stats_task = NULL;
409
410	/* Wait for all RCU callbacks to fire. */
89d46b87	411	rcu_barrier();
a241ec65	412
a241ec65	413	rcu_torture_stats_print(); /* -After- the stats thread is stopped! */
996417d2 PM	414	printk(KERN_ALERT TORTURE_FLAG
	415	"--- End of test: %s\n",
	416	atomic_read(&n_rcu_torture_error) == 0 ? "SUCCESS" : "FAILURE");
a241ec65 PM	417	}
	418
	419	static int
	420	rcu_torture_init(void)
	421	{
	422	int i;
	423	int cpu;
	424	int firsterr = 0;
	425
	426	/* Process args and tell the world that the torturer is on the job. */
	427
	428	if (nreaders >= 0)
	429	nrealreaders = nreaders;
	430	else
	431	nrealreaders = 2 * num_online_cpus();
	432	printk(KERN_ALERT TORTURE_FLAG
	433	"--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
	434	nrealreaders, stat_interval, verbose);
	435	fullstop = 0;
	436
	437	/* Set up the freelist. */
	438
	439	INIT_LIST_HEAD(&rcu_torture_freelist);
	440	for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
996417d2	441	rcu_tortures[i].rtort_mbtest = 0;
a241ec65 PM	442	list_add_tail(&rcu_tortures[i].rtort_free,
	443	&rcu_torture_freelist);
	444	}
	445
	446	/* Initialize the statistics so that each run gets its own numbers. */
	447
	448	rcu_torture_current = NULL;
	449	rcu_torture_current_version = 0;
	450	atomic_set(&n_rcu_torture_alloc, 0);
	451	atomic_set(&n_rcu_torture_alloc_fail, 0);
	452	atomic_set(&n_rcu_torture_free, 0);
996417d2 PM	453	atomic_set(&n_rcu_torture_mberror, 0);
996417d2 PM	454	atomic_set(&n_rcu_torture_error, 0);
a241ec65 PM	455	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
	456	atomic_set(&rcu_torture_wcount[i], 0);
	457	for_each_cpu(cpu) {
	458	for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
	459	per_cpu(rcu_torture_count, cpu)[i] = 0;
	460	per_cpu(rcu_torture_batch, cpu)[i] = 0;
	461	}
	462	}
	463
	464	/* Start up the kthreads. */
	465
	466	VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
	467	writer_task = kthread_run(rcu_torture_writer, NULL,
	468	"rcu_torture_writer");
	469	if (IS_ERR(writer_task)) {
	470	firsterr = PTR_ERR(writer_task);
	471	VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
	472	writer_task = NULL;
	473	goto unwind;
	474	}
	475	reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
	476	GFP_KERNEL);
	477	if (reader_tasks == NULL) {
	478	VERBOSE_PRINTK_ERRSTRING("out of memory");
	479	firsterr = -ENOMEM;
	480	goto unwind;
	481	}
	482	for (i = 0; i < nrealreaders; i++) {
	483	VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
	484	reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
	485	"rcu_torture_reader");
	486	if (IS_ERR(reader_tasks[i])) {
	487	firsterr = PTR_ERR(reader_tasks[i]);
	488	VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
	489	reader_tasks[i] = NULL;
	490	goto unwind;
	491	}
	492	}
	493	if (stat_interval > 0) {
	494	VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
	495	stats_task = kthread_run(rcu_torture_stats, NULL,
	496	"rcu_torture_stats");
	497	if (IS_ERR(stats_task)) {
	498	firsterr = PTR_ERR(stats_task);
	499	VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
	500	stats_task = NULL;
	501	goto unwind;
	502	}
	503	}
	504	return 0;
	505
	506	unwind:
	507	rcu_torture_cleanup();
	508	return firsterr;
	509	}
	510
	511	module_init(rcu_torture_init);
	512	module_exit(rcu_torture_cleanup);