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