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rcu: Add rcutorture CPU-hotplug capability
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Running CPU-hotplug operations concurrently with rcutorture has
historically been a good way to find bugs in both RCU and CPU hotplug.
This commit therefore adds an rcutorture module parameter called
"onoff_interval" that causes a randomly selected CPU-hotplug operation to
be executed at the specified interval, in seconds.  The default value of
"onoff_interval" is zero, which disables rcutorture-instigated CPU-hotplug
operations.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Paul E. McKenney authored and Paul E. McKenney committed Dec 11, 2011
1 parent a95f881 commit b58bdcc
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Showing 2 changed files with 120 additions and 5 deletions.
8 changes: 8 additions & 0 deletions Documentation/RCU/torture.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,14 @@ nreaders This is the number of RCU reading threads supported.
To properly exercise RCU implementations with preemptible
read-side critical sections.

onoff_interval
The number of seconds between each attempt to execute a
randomly selected CPU-hotplug operation. Defaults to
zero, which disables CPU hotplugging. In HOTPLUG_CPU=n
kernels, rcutorture will silently refuse to do any
CPU-hotplug operations regardless of what value is
specified for onoff_interval.

shuffle_interval
The number of seconds to keep the test threads affinitied
to a particular subset of the CPUs, defaults to 3 seconds.
Expand Down
117 changes: 112 additions & 5 deletions kernel/rcutorture.c
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,7 @@ static int irqreader = 1; /* RCU readers from irq (timers). */
static int fqs_duration; /* Duration of bursts (us), 0 to disable. */
static int fqs_holdoff; /* Hold time within burst (us). */
static int fqs_stutter = 3; /* Wait time between bursts (s). */
static int onoff_interval; /* Wait time between CPU hotplugs, 0=disable. */
static int shutdown_secs; /* Shutdown time (s). <=0 for no shutdown. */
static int test_boost = 1; /* Test RCU prio boost: 0=no, 1=maybe, 2=yes. */
static int test_boost_interval = 7; /* Interval between boost tests, seconds. */
Expand Down Expand Up @@ -92,6 +93,8 @@ module_param(fqs_holdoff, int, 0444);
MODULE_PARM_DESC(fqs_holdoff, "Holdoff time within fqs bursts (us)");
module_param(fqs_stutter, int, 0444);
MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
module_param(onoff_interval, int, 0444);
MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
module_param(shutdown_secs, int, 0444);
MODULE_PARM_DESC(shutdown_secs, "Shutdown time (s), zero to disable.");
module_param(test_boost, int, 0444);
Expand Down Expand Up @@ -123,6 +126,9 @@ static struct task_struct *stutter_task;
static struct task_struct *fqs_task;
static struct task_struct *boost_tasks[NR_CPUS];
static struct task_struct *shutdown_task;
#ifdef CONFIG_HOTPLUG_CPU
static struct task_struct *onoff_task;
#endif /* #ifdef CONFIG_HOTPLUG_CPU */

#define RCU_TORTURE_PIPE_LEN 10

Expand Down Expand Up @@ -153,6 +159,10 @@ static long n_rcu_torture_boost_rterror;
static long n_rcu_torture_boost_failure;
static long n_rcu_torture_boosts;
static long n_rcu_torture_timers;
static long n_offline_attempts;
static long n_offline_successes;
static long n_online_attempts;
static long n_online_successes;
static struct list_head rcu_torture_removed;
static cpumask_var_t shuffle_tmp_mask;

Expand Down Expand Up @@ -1084,7 +1094,8 @@ rcu_torture_printk(char *page)
cnt += sprintf(&page[cnt],
"rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d "
"rtmbe: %d rtbke: %ld rtbre: %ld "
"rtbf: %ld rtb: %ld nt: %ld",
"rtbf: %ld rtb: %ld nt: %ld "
"onoff: %ld/%ld:%ld/%ld",
rcu_torture_current,
rcu_torture_current_version,
list_empty(&rcu_torture_freelist),
Expand All @@ -1096,7 +1107,11 @@ rcu_torture_printk(char *page)
n_rcu_torture_boost_rterror,
n_rcu_torture_boost_failure,
n_rcu_torture_boosts,
n_rcu_torture_timers);
n_rcu_torture_timers,
n_online_successes,
n_online_attempts,
n_offline_successes,
n_offline_attempts);
if (atomic_read(&n_rcu_torture_mberror) != 0 ||
n_rcu_torture_boost_ktrerror != 0 ||
n_rcu_torture_boost_rterror != 0 ||
Expand Down Expand Up @@ -1260,12 +1275,14 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
"shuffle_interval=%d stutter=%d irqreader=%d "
"fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
"test_boost=%d/%d test_boost_interval=%d "
"test_boost_duration=%d shutdown_secs=%d\n",
"test_boost_duration=%d shutdown_secs=%d "
"onoff_interval=%d\n",
torture_type, tag, nrealreaders, nfakewriters,
stat_interval, verbose, test_no_idle_hz, shuffle_interval,
stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
test_boost, cur_ops->can_boost,
test_boost_interval, test_boost_duration, shutdown_secs);
test_boost_interval, test_boost_duration, shutdown_secs,
onoff_interval);
}

static struct notifier_block rcutorture_shutdown_nb = {
Expand Down Expand Up @@ -1338,7 +1355,7 @@ rcu_torture_shutdown(void *arg)
schedule_timeout_interruptible(delta);
jiffies_snap = ACCESS_ONCE(jiffies);
}
if (ULONG_CMP_LT(jiffies, shutdown_time)) {
if (kthread_should_stop()) {
VERBOSE_PRINTK_STRING("rcu_torture_shutdown task stopping");
return 0;
}
Expand All @@ -1352,6 +1369,94 @@ rcu_torture_shutdown(void *arg)
return 0;
}

#ifdef CONFIG_HOTPLUG_CPU

/*
* Execute random CPU-hotplug operations at the interval specified
* by the onoff_interval.
*/
static int
rcu_torture_onoff(void *arg)
{
int cpu;
int maxcpu = -1;
DEFINE_RCU_RANDOM(rand);

VERBOSE_PRINTK_STRING("rcu_torture_onoff task started");
for_each_online_cpu(cpu)
maxcpu = cpu;
WARN_ON(maxcpu < 0);
while (!kthread_should_stop()) {
cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1);
if (cpu_online(cpu)) {
if (verbose)
printk(KERN_ALERT "%s" TORTURE_FLAG
"rcu_torture_onoff task: offlining %d\n",
torture_type, cpu);
n_offline_attempts++;
if (cpu_down(cpu) == 0) {
if (verbose)
printk(KERN_ALERT "%s" TORTURE_FLAG
"rcu_torture_onoff task: "
"offlined %d\n",
torture_type, cpu);
n_offline_successes++;
}
} else {
if (verbose)
printk(KERN_ALERT "%s" TORTURE_FLAG
"rcu_torture_onoff task: onlining %d\n",
torture_type, cpu);
n_online_attempts++;
if (cpu_up(cpu) == 0) {
if (verbose)
printk(KERN_ALERT "%s" TORTURE_FLAG
"rcu_torture_onoff task: "
"onlined %d\n",
torture_type, cpu);
n_online_successes++;
}
}
schedule_timeout_interruptible(onoff_interval * HZ);
}
VERBOSE_PRINTK_STRING("rcu_torture_onoff task stopping");
return 0;
}

static int
rcu_torture_onoff_init(void)
{
if (onoff_interval <= 0)
return 0;
onoff_task = kthread_run(rcu_torture_onoff, NULL, "rcu_torture_onoff");
if (IS_ERR(onoff_task)) {
onoff_task = NULL;
return PTR_ERR(onoff_task);
}
return 0;
}

static void rcu_torture_onoff_cleanup(void)
{
if (onoff_task == NULL)
return;
VERBOSE_PRINTK_STRING("Stopping rcu_torture_onoff task");
kthread_stop(onoff_task);
}

#else /* #ifdef CONFIG_HOTPLUG_CPU */

static void
rcu_torture_onoff_init(void)
{
}

static void rcu_torture_onoff_cleanup(void)
{
}

#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */

static int rcutorture_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
Expand Down Expand Up @@ -1460,6 +1565,7 @@ rcu_torture_cleanup(void)
VERBOSE_PRINTK_STRING("Stopping rcu_torture_shutdown task");
kthread_stop(shutdown_task);
}
rcu_torture_onoff_cleanup();

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

Expand Down Expand Up @@ -1687,6 +1793,7 @@ rcu_torture_init(void)
goto unwind;
}
}
rcu_torture_onoff_init();
register_reboot_notifier(&rcutorture_shutdown_nb);
rcutorture_record_test_transition();
mutex_unlock(&fullstop_mutex);
Expand Down

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