Commit b58bdcca authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
Browse files

rcu: Add rcutorture CPU-hotplug capability 



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: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent a95f8817

Documentation/RCU/torture.txt

+8 −0
Original line number Diff line number Diff line
@@ -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.

kernel/rcutorture.c

+112 −5
Original line number Diff line number Diff line
@@ -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. */
@@ -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);
@@ -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
@@ -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;
@@ -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),
@@ -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 ||
@@ -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 = {
@@ -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;

	}
@@ -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)

{
@@ -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.  */
@@ -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);

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