Re: [BUG] NULL pointer deref with rcutorture

Paul E. McKenney
2009-01-07T19:46:51Z

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On Tue, Jan 06, 2009 at 04:48:09AM -0800, Paul E. McKenney wrote:
> On Tue, Jan 06, 2009 at 08:47:07AM +0100, Eric Sesterhenn wrote:
> > * Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote:
> > > On Mon, Jan 05, 2009 at 04:29:12PM -0800, Paul E. McKenney wrote:
> > > > On Mon, Jan 05, 2009 at 02:18:36PM -0800, Paul E. McKenney wrote:
> > > > I will see what I can find from this.
> > >
> > > Hello, Eric,
> > >
> > > Just for grins, I built the 2.6.28 kernel/rcutorture.c on b58602a. It
> > > insmoded and rmmoded without errors.
> > >
> > > Could you please try this on your setup? I have attached this file in
> > > case that helps.
> >
> > works like a charm
>
> Well, that certainly tells me where the bug lies. ;-)
>
> Thank you for all your hard work on this, I should have a patch soon.

And here it is, against the original version of rcutorture.c (revert
all of my previous patches against rcutorture.c). I am also attaching
the resulting rcutorture.c, if that makes things more convenient for you.

This one survives modprobe and rmmod, and also survives when shutdown
while running. Here are the operating modes:

CONFIG_RCU_TORTURE_TEST=m

This is the normal rcutorture build. Use "modprobe rcutorture"
(with optional arguments) to start, and "rmmod rcutorture" to
stop. If you shut the system down without doing the rmmod, you
should see console output like:

rcutorture thread rcu_torture_writer parking due to system shutdown

One for each rcutorture kthread.

CONFIG_RCU_TORTURE_TEST=y
CONFIG_RCU_TORTURE_TEST_RUNNABLE=n

Use this if you want rcutorture built in, but don't want the
test to start running during early boot. To start the
torturing:

echo 1 > /proc/sys/kernel/rcutorture_runnable

To stop the torturing, s/1/0/

You will get "parking" console messages as noted above when
you shut the system down.

CONFIG_RCU_TORTURE_TEST=y
CONFIG_RCU_TORTURE_TEST_RUNNABLE=y

Same as above, except that the torturing starts during early
boot. Only for the stout of heart and strong of stomach.
The same /proc entry noted above may be used to control the
test.

Could you please fire this up and see if it fixes the rmmod-time bug
that you located?

Thanx, Paul

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---

rcutorture.c | 94 +++++++++++++++++++++++++++++++++++++----------------------
1 file changed, 59 insertions(+), 35 deletions(-)

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index b310655..7c4142a 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -136,31 +136,47 @@ static int stutter_pause_test = 0;
#endif
int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;

-#define FULLSTOP_SIGNALED 1 /* Bail due to signal. */
-#define FULLSTOP_CLEANUP 2 /* Orderly shutdown. */
-static int fullstop; /* stop generating callbacks at test end. */
-DEFINE_MUTEX(fullstop_mutex); /* protect fullstop transitions and */
- /* spawning of kthreads. */
+/* Mediate rmmod and system shutdown. Concurrent rmmod & shutdown illegal! */
+
+#define FULLSTOP_DONTSTOP 0 /* Normal operation. */
+#define FULLSTOP_SHUTDOWN 1 /* System shutdown with rcutorture running. */
+#define FULLSTOP_RMMOD 2 /* Normal rmmod of rcutorture. */
+static int fullstop = FULLSTOP_RMMOD;
+DEFINE_MUTEX(fullstop_mutex); /* Protect fullstop transitions and spawning */
+ /* of kthreads. */

/*
- * Detect and respond to a signal-based shutdown.
+ * Detect and respond to a system shutdown.
*/
static int
rcutorture_shutdown_notify(struct notifier_block *unused1,
unsigned long unused2, void *unused3)
{
- if (fullstop)
- return NOTIFY_DONE;
- if (signal_pending(current)) {
- mutex_lock(&fullstop_mutex);
- if (!ACCESS_ONCE(fullstop))
- fullstop = FULLSTOP_SIGNALED;
- mutex_unlock(&fullstop_mutex);
- }
+ mutex_lock(&fullstop_mutex);
+ if (fullstop == FULLSTOP_DONTSTOP)
+ fullstop = FULLSTOP_SHUTDOWN;
+ else
+ printk(KERN_WARNING /* but going down anyway, so... */
+ "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
+ mutex_unlock(&fullstop_mutex);
return NOTIFY_DONE;
}

/*
+ * Absorb kthreads into a kernel function that won't return, so that
+ * they won't ever access module text or data again.
+ */
+static void rcutorture_shutdown_absorb(char *title)
+{
+ if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
+ printk(KERN_NOTICE
+ "rcutorture thread %s parking due to system shutdown\n",
+ title);
+ schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
+ }
+}
+
+/*
* Allocate an element from the rcu_tortures pool.
*/
static struct rcu_torture *
@@ -221,13 +237,14 @@ rcu_random(struct rcu_random_state *rrsp)
}

static void
-rcu_stutter_wait(void)
+rcu_stutter_wait(char *title)
{
- while ((stutter_pause_test || !rcutorture_runnable) && !fullstop) {
+ while (stutter_pause_test || !rcutorture_runnable) {
if (rcutorture_runnable)
schedule_timeout_interruptible(1);
else
schedule_timeout_interruptible(round_jiffies_relative(HZ));
+ rcutorture_shutdown_absorb(title);
}
}

@@ -289,7 +306,7 @@ rcu_torture_cb(struct rcu_head *p)
int i;
struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);

- if (fullstop) {
+ if (fullstop != FULLSTOP_DONTSTOP) {
/* Test is ending, just drop callbacks on the floor. */
/* The next initialization will pick up the pieces. */
return;
@@ -621,10 +638,11 @@ rcu_torture_writer(void *arg)
}
rcu_torture_current_version++;
oldbatch = cur_ops->completed();
- rcu_stutter_wait();
- } while (!kthread_should_stop() && !fullstop);
+ rcu_stutter_wait("rcu_torture_writer");
+ } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
- while (!kthread_should_stop() && fullstop != FULLSTOP_SIGNALED)
+ rcutorture_shutdown_absorb("rcu_torture_writer");
+ while (!kthread_should_stop())
schedule_timeout_uninterruptible(1);
return 0;
}
@@ -645,11 +663,12 @@ rcu_torture_fakewriter(void *arg)
schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
udelay(rcu_random(&rand) & 0x3ff);
cur_ops->sync();
- rcu_stutter_wait();
- } while (!kthread_should_stop() && !fullstop);
+ rcu_stutter_wait("rcu_torture_fakewriter");
+ } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);

VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
- while (!kthread_should_stop() && fullstop != FULLSTOP_SIGNALED)
+ rcutorture_shutdown_absorb("rcu_torture_fakewriter");
+ while (!kthread_should_stop())
schedule_timeout_uninterruptible(1);
return 0;
}
@@ -754,12 +773,13 @@ rcu_torture_reader(void *arg)
preempt_enable();
cur_ops->readunlock(idx);
schedule();
- rcu_stutter_wait();
- } while (!kthread_should_stop() && !fullstop);
+ rcu_stutter_wait("rcu_torture_reader");
+ } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
+ rcutorture_shutdown_absorb("rcu_torture_reader");
if (irqreader && cur_ops->irqcapable)
del_timer_sync(&t);
- while (!kthread_should_stop() && fullstop != FULLSTOP_SIGNALED)
+ while (!kthread_should_stop())
schedule_timeout_uninterruptible(1);
return 0;
}
@@ -856,7 +876,8 @@ rcu_torture_stats(void *arg)
do {
schedule_timeout_interruptible(stat_interval * HZ);
rcu_torture_stats_print();
- } while (!kthread_should_stop() && !fullstop);
+ rcutorture_shutdown_absorb("rcu_torture_stats");
+ } while (!kthread_should_stop());
VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
return 0;
}
@@ -924,7 +945,8 @@ rcu_torture_shuffle(void *arg)
do {
schedule_timeout_interruptible(shuffle_interval * HZ);
rcu_torture_shuffle_tasks();
- } while (!kthread_should_stop() && !fullstop);
+ rcutorture_shutdown_absorb("rcu_torture_shuffle");
+ } while (!kthread_should_stop());
VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
return 0;
}
@@ -939,10 +961,11 @@ rcu_torture_stutter(void *arg)
do {
schedule_timeout_interruptible(stutter * HZ);
stutter_pause_test = 1;
- if (!kthread_should_stop() && !fullstop)
+ if (!kthread_should_stop())
schedule_timeout_interruptible(stutter * HZ);
stutter_pause_test = 0;
- } while (!kthread_should_stop() && !fullstop);
+ rcutorture_shutdown_absorb("rcu_torture_stutter");
+ } while (!kthread_should_stop());
VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
return 0;
}
@@ -969,15 +992,16 @@ rcu_torture_cleanup(void)
int i;

mutex_lock(&fullstop_mutex);
- if (!fullstop) {
- /* If being signaled, let it happen, then exit. */
+ if (fullstop == FULLSTOP_SHUTDOWN) {
+ printk(KERN_WARNING /* but going down anyway, so... */
+ "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
mutex_unlock(&fullstop_mutex);
- schedule_timeout_interruptible(10 * HZ);
+ schedule_timeout_uninterruptible(10);
if (cur_ops->cb_barrier != NULL)
cur_ops->cb_barrier();
return;
}
- fullstop = FULLSTOP_CLEANUP;
+ fullstop = FULLSTOP_RMMOD;
mutex_unlock(&fullstop_mutex);
unregister_reboot_notifier(&rcutorture_nb);
if (stutter_task) {
@@ -1077,7 +1101,7 @@ rcu_torture_init(void)
else
nrealreaders = 2 * num_online_cpus();
rcu_torture_print_module_parms("Start of test");
- fullstop = 0;
+ fullstop = FULLSTOP_DONTSTOP;

/* Set up the freelist. */

[-- Attachment #2: kernel/rcutorture.c --]
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/*
* Read-Copy Update module-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, 2006
*
* Authors: Paul E. McKenney <paulmck@us.ibm.com>
* Josh Triplett <josh@freedesktop.org>
*
* 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/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/freezer.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/stat.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <asm/byteorder.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and "
"Josh Triplett <josh@freedesktop.org>");

static int nreaders = -1; /* # reader threads, defaults to 2*ncpus */
static int nfakewriters = 4; /* # fake writer threads */
static int stat_interval; /* Interval between stats, in seconds. */
/* Defaults to "only at end of test". */
static int verbose; /* Print more debug info. */
static int test_no_idle_hz; /* Test RCU's support for tickless idle CPUs. */
static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
static int stutter = 5; /* Start/stop testing interval (in sec) */
static int irqreader = 1; /* RCU readers from irq (timers). */
static char *torture_type = "rcu"; /* What RCU implementation to torture. */

module_param(nreaders, int, 0444);
MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
module_param(nfakewriters, int, 0444);
MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
module_param(stat_interval, int, 0444);
MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
module_param(verbose, bool, 0444);
MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
module_param(test_no_idle_hz, bool, 0444);
MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
module_param(shuffle_interval, int, 0444);
MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
module_param(stutter, int, 0444);
MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
module_param(irqreader, int, 0444);
MODULE_PARM_DESC(irqreader, "Allow RCU readers from irq handlers");
module_param(torture_type, charp, 0444);
MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");

#define TORTURE_FLAG "-torture:"
#define PRINTK_STRING(s) \
do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
#define VERBOSE_PRINTK_STRING(s) \
do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
#define VERBOSE_PRINTK_ERRSTRING(s) \
do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)

static char printk_buf[4096];

static int nrealreaders;
static struct task_struct *writer_task;
static struct task_struct **fakewriter_tasks;
static struct task_struct **reader_tasks;
static struct task_struct *stats_task;
static struct task_struct *shuffler_task;
static struct task_struct *stutter_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 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];
static atomic_t n_rcu_torture_alloc;
static atomic_t n_rcu_torture_alloc_fail;
static atomic_t n_rcu_torture_free;
static atomic_t n_rcu_torture_mberror;
static atomic_t n_rcu_torture_error;
static long n_rcu_torture_timers = 0;
static struct list_head rcu_torture_removed;

static int stutter_pause_test = 0;

#if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
#define RCUTORTURE_RUNNABLE_INIT 1
#else
#define RCUTORTURE_RUNNABLE_INIT 0
#endif
int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;

/* Mediate rmmod and system shutdown. Concurrent rmmod & shutdown illegal! */

#define FULLSTOP_DONTSTOP 0 /* Normal operation. */
#define FULLSTOP_SHUTDOWN 1 /* System shutdown with rcutorture running. */
#define FULLSTOP_RMMOD 2 /* Normal rmmod of rcutorture. */
static int fullstop = FULLSTOP_RMMOD;
DEFINE_MUTEX(fullstop_mutex); /* Protect fullstop transitions and spawning */
/* of kthreads. */

/*
* Detect and respond to a system shutdown.
*/
static int
rcutorture_shutdown_notify(struct notifier_block *unused1,
unsigned long unused2, void *unused3)
{
mutex_lock(&fullstop_mutex);
if (fullstop == FULLSTOP_DONTSTOP)
fullstop = FULLSTOP_SHUTDOWN;
else
printk(KERN_WARNING /* but going down anyway, so... */
"Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
mutex_unlock(&fullstop_mutex);
return NOTIFY_DONE;
}

/*
* Absorb kthreads into a kernel function that won't return, so that
* they won't ever access module text or data again.
*/
static void rcutorture_shutdown_absorb(char *title)
{
if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
printk(KERN_NOTICE
"rcutorture thread %s parking due to system shutdown\n",
title);
schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
}
}

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

spin_lock_bh(&rcu_torture_lock);
if (list_empty(&rcu_torture_freelist)) {
atomic_inc(&n_rcu_torture_alloc_fail);
spin_unlock_bh(&rcu_torture_lock);
return NULL;
}
atomic_inc(&n_rcu_torture_alloc);
p = rcu_torture_freelist.next;
list_del_init(p);
spin_unlock_bh(&rcu_torture_lock);
return container_of(p, struct rcu_torture, rtort_free);
}

/*
* Free an element to the rcu_tortures pool.
*/
static void
rcu_torture_free(struct rcu_torture *p)
{
atomic_inc(&n_rcu_torture_free);
spin_lock_bh(&rcu_torture_lock);
list_add_tail(&p->rtort_free, &rcu_torture_freelist);
spin_unlock_bh(&rcu_torture_lock);
}

struct rcu_random_state {
unsigned long rrs_state;
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 cpu_clock().
*/
static unsigned long
rcu_random(struct rcu_random_state *rrsp)
{
if (--rrsp->rrs_count < 0) {
rrsp->rrs_state +=
(unsigned long)cpu_clock(raw_smp_processor_id());
rrsp->rrs_count = RCU_RANDOM_REFRESH;
}
rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
return swahw32(rrsp->rrs_state);
}

static void
rcu_stutter_wait(char *title)
{
while (stutter_pause_test || !rcutorture_runnable) {
if (rcutorture_runnable)
schedule_timeout_interruptible(1);
else
schedule_timeout_interruptible(round_jiffies_relative(HZ));
rcutorture_shutdown_absorb(title);
}
}

/*
* Operations vector for selecting different types of tests.
*/

struct rcu_torture_ops {
void (*init)(void);
void (*cleanup)(void);
int (*readlock)(void);
void (*readdelay)(struct rcu_random_state *rrsp);
void (*readunlock)(int idx);
int (*completed)(void);
void (*deferredfree)(struct rcu_torture *p);
void (*sync)(void);
void (*cb_barrier)(void);
int (*stats)(char *page);
int irqcapable;
char *name;
};
static struct rcu_torture_ops *cur_ops = NULL;

/*
* Definitions for rcu torture testing.
*/

static int rcu_torture_read_lock(void) __acquires(RCU)
{
rcu_read_lock();
return 0;
}

static void rcu_read_delay(struct rcu_random_state *rrsp)
{
long delay;
const long longdelay = 200;

/* We want there to be long-running readers, but not all the time. */

delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
if (!delay)
udelay(longdelay);
}

static void rcu_torture_read_unlock(int idx) __releases(RCU)
{
rcu_read_unlock();
}

static int rcu_torture_completed(void)
{
return rcu_batches_completed();
}

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 != FULLSTOP_DONTSTOP) {
/* 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
cur_ops->deferredfree(rp);
}

static void rcu_torture_deferred_free(struct rcu_torture *p)
{
call_rcu(&p->rtort_rcu, rcu_torture_cb);
}

static struct rcu_torture_ops rcu_ops = {
.init = NULL,
.cleanup = NULL,
.readlock = rcu_torture_read_lock,
.readdelay = rcu_read_delay,
.readunlock = rcu_torture_read_unlock,
.completed = rcu_torture_completed,
.deferredfree = rcu_torture_deferred_free,
.sync = synchronize_rcu,
.cb_barrier = rcu_barrier,
.stats = NULL,
.irqcapable = 1,
.name = "rcu"
};

static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
{
int i;
struct rcu_torture *rp;
struct rcu_torture *rp1;

cur_ops->sync();
list_add(&p->rtort_free, &rcu_torture_removed);
list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
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;
list_del(&rp->rtort_free);
rcu_torture_free(rp);
}
}
}

static void rcu_sync_torture_init(void)
{
INIT_LIST_HEAD(&rcu_torture_removed);
}

static struct rcu_torture_ops rcu_sync_ops = {
.init = rcu_sync_torture_init,
.cleanup = NULL,
.readlock = rcu_torture_read_lock,
.readdelay = rcu_read_delay,
.readunlock = rcu_torture_read_unlock,
.completed = rcu_torture_completed,
.deferredfree = rcu_sync_torture_deferred_free,
.sync = synchronize_rcu,
.cb_barrier = NULL,
.stats = NULL,
.irqcapable = 1,
.name = "rcu_sync"
};

/*
* Definitions for rcu_bh torture testing.
*/

static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
{
rcu_read_lock_bh();
return 0;
}

static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
{
rcu_read_unlock_bh();
}

static int rcu_bh_torture_completed(void)
{
return rcu_batches_completed_bh();
}

static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
{
call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
}

struct rcu_bh_torture_synchronize {
struct rcu_head head;
struct completion completion;
};

static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
{
struct rcu_bh_torture_synchronize *rcu;

rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
complete(&rcu->completion);
}

static void rcu_bh_torture_synchronize(void)
{
struct rcu_bh_torture_synchronize rcu;

init_completion(&rcu.completion);
call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
wait_for_completion(&rcu.completion);
}

static struct rcu_torture_ops rcu_bh_ops = {
.init = NULL,
.cleanup = NULL,
.readlock = rcu_bh_torture_read_lock,
.readdelay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = rcu_bh_torture_read_unlock,
.completed = rcu_bh_torture_completed,
.deferredfree = rcu_bh_torture_deferred_free,
.sync = rcu_bh_torture_synchronize,
.cb_barrier = rcu_barrier_bh,
.stats = NULL,
.irqcapable = 1,
.name = "rcu_bh"
};

static struct rcu_torture_ops rcu_bh_sync_ops = {
.init = rcu_sync_torture_init,
.cleanup = NULL,
.readlock = rcu_bh_torture_read_lock,
.readdelay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = rcu_bh_torture_read_unlock,
.completed = rcu_bh_torture_completed,
.deferredfree = rcu_sync_torture_deferred_free,
.sync = rcu_bh_torture_synchronize,
.cb_barrier = NULL,
.stats = NULL,
.irqcapable = 1,
.name = "rcu_bh_sync"
};

/*
* Definitions for srcu torture testing.
*/

static struct srcu_struct srcu_ctl;

static void srcu_torture_init(void)
{
init_srcu_struct(&srcu_ctl);
rcu_sync_torture_init();
}

static void srcu_torture_cleanup(void)
{
synchronize_srcu(&srcu_ctl);
cleanup_srcu_struct(&srcu_ctl);
}

static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
{
return srcu_read_lock(&srcu_ctl);
}

static void srcu_read_delay(struct rcu_random_state *rrsp)
{
long delay;
const long uspertick = 1000000 / HZ;
const long longdelay = 10;

/* We want there to be long-running readers, but not all the time. */

delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
if (!delay)
schedule_timeout_interruptible(longdelay);
}

static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
{
srcu_read_unlock(&srcu_ctl, idx);
}

static int srcu_torture_completed(void)
{
return srcu_batches_completed(&srcu_ctl);
}

static void srcu_torture_synchronize(void)
{
synchronize_srcu(&srcu_ctl);
}

static int srcu_torture_stats(char *page)
{
int cnt = 0;
int cpu;
int idx = srcu_ctl.completed & 0x1;

cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
torture_type, TORTURE_FLAG, idx);
for_each_possible_cpu(cpu) {
cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
}
cnt += sprintf(&page[cnt], "\n");
return cnt;
}

static struct rcu_torture_ops srcu_ops = {
.init = srcu_torture_init,
.cleanup = srcu_torture_cleanup,
.readlock = srcu_torture_read_lock,
.readdelay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock,
.completed = srcu_torture_completed,
.deferredfree = rcu_sync_torture_deferred_free,
.sync = srcu_torture_synchronize,
.cb_barrier = NULL,
.stats = srcu_torture_stats,
.name = "srcu"
};

/*
* Definitions for sched torture testing.
*/

static int sched_torture_read_lock(void)
{
preempt_disable();
return 0;
}

static void sched_torture_read_unlock(int idx)
{
preempt_enable();
}

static int sched_torture_completed(void)
{
return 0;
}

static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
{
call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
}

static void sched_torture_synchronize(void)
{
synchronize_sched();
}

static struct rcu_torture_ops sched_ops = {
.init = rcu_sync_torture_init,
.cleanup = NULL,
.readlock = sched_torture_read_lock,
.readdelay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = sched_torture_read_unlock,
.completed = sched_torture_completed,
.deferredfree = rcu_sched_torture_deferred_free,
.sync = sched_torture_synchronize,
.cb_barrier = rcu_barrier_sched,
.stats = NULL,
.irqcapable = 1,
.name = "sched"
};

static struct rcu_torture_ops sched_ops_sync = {
.init = rcu_sync_torture_init,
.cleanup = NULL,
.readlock = sched_torture_read_lock,
.readdelay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = sched_torture_read_unlock,
.completed = sched_torture_completed,
.deferredfree = rcu_sync_torture_deferred_free,
.sync = sched_torture_synchronize,
.cb_barrier = NULL,
.stats = NULL,
.name = "sched_sync"
};

/*
* 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 ((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) {
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++;
cur_ops->deferredfree(old_rp);
}
rcu_torture_current_version++;
oldbatch = cur_ops->completed();
rcu_stutter_wait("rcu_torture_writer");
} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
rcutorture_shutdown_absorb("rcu_torture_writer");
while (!kthread_should_stop())
schedule_timeout_uninterruptible(1);
return 0;
}

/*
* RCU torture fake writer kthread. Repeatedly calls sync, with a random
* delay between calls.
*/
static int
rcu_torture_fakewriter(void *arg)
{
DEFINE_RCU_RANDOM(rand);

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

do {
schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
udelay(rcu_random(&rand) & 0x3ff);
cur_ops->sync();
rcu_stutter_wait("rcu_torture_fakewriter");
} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);

VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
rcutorture_shutdown_absorb("rcu_torture_fakewriter");
while (!kthread_should_stop())
schedule_timeout_uninterruptible(1);
return 0;
}

/*
* RCU torture reader from timer handler. Dereferences rcu_torture_current,
* incrementing the corresponding element of the pipeline array. The
* counter in the element should never be greater than 1, otherwise, the
* RCU implementation is broken.
*/
static void rcu_torture_timer(unsigned long unused)
{
int idx;
int completed;
static DEFINE_RCU_RANDOM(rand);
static DEFINE_SPINLOCK(rand_lock);
struct rcu_torture *p;
int pipe_count;

idx = cur_ops->readlock();
completed = cur_ops->completed();
p = rcu_dereference(rcu_torture_current);
if (p == NULL) {
/* Leave because rcu_torture_writer is not yet underway */
cur_ops->readunlock(idx);
return;
}
if (p->rtort_mbtest == 0)
atomic_inc(&n_rcu_torture_mberror);
spin_lock(&rand_lock);
cur_ops->readdelay(&rand);
n_rcu_torture_timers++;
spin_unlock(&rand_lock);
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 = cur_ops->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();
cur_ops->readunlock(idx);
}

/*
* 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;
int idx;
DEFINE_RCU_RANDOM(rand);
struct rcu_torture *p;
int pipe_count;
struct timer_list t;

VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
set_user_nice(current, 19);
if (irqreader && cur_ops->irqcapable)
setup_timer_on_stack(&t, rcu_torture_timer, 0);

do {
if (irqreader && cur_ops->irqcapable) {
if (!timer_pending(&t))
mod_timer(&t, 1);
}
idx = cur_ops->readlock();
completed = cur_ops->completed();
p = rcu_dereference(rcu_torture_current);
if (p == NULL) {
/* Wait for rcu_torture_writer to get underway */
cur_ops->readunlock(idx);
schedule_timeout_interruptible(HZ);
continue;
}
if (p->rtort_mbtest == 0)
atomic_inc(&n_rcu_torture_mberror);
cur_ops->readdelay(&rand);
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 = cur_ops->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();
cur_ops->readunlock(idx);
schedule();
rcu_stutter_wait("rcu_torture_reader");
} while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
rcutorture_shutdown_absorb("rcu_torture_reader");
if (irqreader && cur_ops->irqcapable)
del_timer_sync(&t);
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_possible_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], "%s%s ", torture_type, TORTURE_FLAG);
cnt += sprintf(&page[cnt],
"rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
"rtmbe: %d nt: %ld",
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),
n_rcu_torture_timers);
if (atomic_read(&n_rcu_torture_mberror) != 0)
cnt += sprintf(&page[cnt], " !!!");
cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
if (i > 1) {
cnt += sprintf(&page[cnt], "!!! ");
atomic_inc(&n_rcu_torture_error);
WARN_ON_ONCE(1);
}
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], "\n%s%s ", torture_type, TORTURE_FLAG);
cnt += sprintf(&page[cnt], "Reader Batch: ");
for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
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");
if (cur_ops->stats)
cnt += cur_ops->stats(&page[cnt]);
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();
rcutorture_shutdown_absorb("rcu_torture_stats");
} while (!kthread_should_stop());
VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
return 0;
}

static int rcu_idle_cpu; /* Force all torture tasks off this CPU */

/* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
* is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
*/
static void rcu_torture_shuffle_tasks(void)
{
cpumask_t tmp_mask;
int i;

cpus_setall(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;
}

if (rcu_idle_cpu != -1)
cpu_clear(rcu_idle_cpu, tmp_mask);

set_cpus_allowed_ptr(current, &tmp_mask);

if (reader_tasks) {
for (i = 0; i < nrealreaders; i++)
if (reader_tasks[i])
set_cpus_allowed_ptr(reader_tasks[i],
&tmp_mask);
}

if (fakewriter_tasks) {
for (i = 0; i < nfakewriters; i++)
if (fakewriter_tasks[i])
set_cpus_allowed_ptr(fakewriter_tasks[i],
&tmp_mask);
}

if (writer_task)
set_cpus_allowed_ptr(writer_task, &tmp_mask);

if (stats_task)
set_cpus_allowed_ptr(stats_task, &tmp_mask);

if (rcu_idle_cpu == -1)
rcu_idle_cpu = num_online_cpus() - 1;
else
rcu_idle_cpu--;

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
rcu_torture_shuffle(void *arg)
{
VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
do {
schedule_timeout_interruptible(shuffle_interval * HZ);
rcu_torture_shuffle_tasks();
rcutorture_shutdown_absorb("rcu_torture_shuffle");
} while (!kthread_should_stop());
VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
return 0;
}

/* Cause the rcutorture test to "stutter", starting and stopping all
* threads periodically.
*/
static int
rcu_torture_stutter(void *arg)
{
VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
do {
schedule_timeout_interruptible(stutter * HZ);
stutter_pause_test = 1;
if (!kthread_should_stop())
schedule_timeout_interruptible(stutter * HZ);
stutter_pause_test = 0;
rcutorture_shutdown_absorb("rcu_torture_stutter");
} while (!kthread_should_stop());
VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
return 0;
}

static inline void
rcu_torture_print_module_parms(char *tag)
{
printk(KERN_ALERT "%s" TORTURE_FLAG
"--- %s: nreaders=%d nfakewriters=%d "
"stat_interval=%d verbose=%d test_no_idle_hz=%d "
"shuffle_interval=%d stutter=%d irqreader=%d\n",
torture_type, tag, nrealreaders, nfakewriters,
stat_interval, verbose, test_no_idle_hz, shuffle_interval,
stutter, irqreader);
}

static struct notifier_block rcutorture_nb = {
.notifier_call = rcutorture_shutdown_notify,
};

static void
rcu_torture_cleanup(void)
{
int i;

mutex_lock(&fullstop_mutex);
if (fullstop == FULLSTOP_SHUTDOWN) {
printk(KERN_WARNING /* but going down anyway, so... */
"Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
mutex_unlock(&fullstop_mutex);
schedule_timeout_uninterruptible(10);
if (cur_ops->cb_barrier != NULL)
cur_ops->cb_barrier();
return;
}
fullstop = FULLSTOP_RMMOD;
mutex_unlock(&fullstop_mutex);
unregister_reboot_notifier(&rcutorture_nb);
if (stutter_task) {
VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
kthread_stop(stutter_task);
}
stutter_task = NULL;
if (shuffler_task) {
VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
kthread_stop(shuffler_task);
}
shuffler_task = NULL;

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

if (reader_tasks) {
for (i = 0; i < nrealreaders; i++) {
if (reader_tasks[i]) {
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 (fakewriter_tasks) {
for (i = 0; i < nfakewriters; i++) {
if (fakewriter_tasks[i]) {
VERBOSE_PRINTK_STRING(
"Stopping rcu_torture_fakewriter task");
kthread_stop(fakewriter_tasks[i]);
}
fakewriter_tasks[i] = NULL;
}
kfree(fakewriter_tasks);
fakewriter_tasks = NULL;
}

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

/* Wait for all RCU callbacks to fire. */

if (cur_ops->cb_barrier != NULL)
cur_ops->cb_barrier();

rcu_torture_stats_print(); /* -After- the stats thread is stopped! */

if (cur_ops->cleanup)
cur_ops->cleanup();
if (atomic_read(&n_rcu_torture_error))
rcu_torture_print_module_parms("End of test: FAILURE");
else
rcu_torture_print_module_parms("End of test: SUCCESS");
}

static int __init
rcu_torture_init(void)
{
int i;
int cpu;
int firsterr = 0;
static struct rcu_torture_ops *torture_ops[] =
{ &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
&srcu_ops, &sched_ops, &sched_ops_sync, };

mutex_lock(&fullstop_mutex);

/* Process args and tell the world that the torturer is on the job. */
for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
cur_ops = torture_ops[i];
if (strcmp(torture_type, cur_ops->name) == 0)
break;
}
if (i == ARRAY_SIZE(torture_ops)) {
printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
torture_type);
mutex_unlock(&fullstop_mutex);
return (-EINVAL);
}
if (cur_ops->init)
cur_ops->init(); /* no "goto unwind" prior to this point!!! */

if (nreaders >= 0)
nrealreaders = nreaders;
else
nrealreaders = 2 * num_online_cpus();
rcu_torture_print_module_parms("Start of test");
fullstop = FULLSTOP_DONTSTOP;

/* Set up the freelist. */

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

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

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

/* 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;
}
fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
GFP_KERNEL);
if (fakewriter_tasks == NULL) {
VERBOSE_PRINTK_ERRSTRING("out of memory");
firsterr = -ENOMEM;
goto unwind;
}
for (i = 0; i < nfakewriters; i++) {
VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
"rcu_torture_fakewriter");
if (IS_ERR(fakewriter_tasks[i])) {
firsterr = PTR_ERR(fakewriter_tasks[i]);
VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
fakewriter_tasks[i] = NULL;
goto unwind;
}
}
reader_tasks = kzalloc(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;
}
}
if (test_no_idle_hz) {
rcu_idle_cpu = num_online_cpus() - 1;
/* Create the shuffler thread */
shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
"rcu_torture_shuffle");
if (IS_ERR(shuffler_task)) {
firsterr = PTR_ERR(shuffler_task);
VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
shuffler_task = NULL;
goto unwind;
}
}
if (stutter < 0)
stutter = 0;
if (stutter) {
/* Create the stutter thread */
stutter_task = kthread_run(rcu_torture_stutter, NULL,
"rcu_torture_stutter");
if (IS_ERR(stutter_task)) {
firsterr = PTR_ERR(stutter_task);
VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
stutter_task = NULL;
goto unwind;
}
}
register_reboot_notifier(&rcutorture_nb);
mutex_unlock(&fullstop_mutex);
return 0;

unwind:
mutex_unlock(&fullstop_mutex);
rcu_torture_cleanup();
return firsterr;
}

module_init(rcu_torture_init);
module_exit(rcu_torture_cleanup);