Commit c13f3757 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
Browse files

rcu: Add CPU-stall capability to rcutorture 



Add module parameters to rcutorture that induce a CPU stall.
The stall_cpu parameter specifies how long to stall in seconds,
defaulting to zero, which indicates no stalling is to be undertaken.
The stall_cpu_holdoff parameter specifies how many seconds after
insmod (or boot, if rcutorture is built into the kernel) that this
stall is to start.  The default value for stall_cpu_holdoff is ten
seconds.

Signed-off-by: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 105617da

Documentation/RCU/torture.txt

+18 −0
Original line number Diff line number Diff line
@@ -86,6 +86,24 @@ shutdown_secs The number of seconds to run the test before terminating 
		zero, which disables test termination and system shutdown.

		This capability is useful for automated testing.



stall_cpu	The number of seconds that a CPU should be stalled while

		within both an rcu_read_lock() and a preempt_disable().

		This stall happens only once per rcutorture run.

		If you need multiple stalls, use modprobe and rmmod to

		repeatedly run rcutorture.  The default for stall_cpu

		is zero, which prevents rcutorture from stalling a CPU.



		Note that attempts to rmmod rcutorture while the stall

		is ongoing will hang, so be careful what value you

		choose for this module parameter!  In addition, too-large

		values for stall_cpu might well induce failures and

		warnings in other parts of the kernel.  You have been

		warned!



stall_cpu_holdoff

		The number of seconds to wait after rcutorture starts

		before stalling a CPU.  Defaults to 10 seconds.



stat_interval	The number of seconds between output of torture

		statistics (via printk()).  Regardless of the interval,

		statistics are printed when the module is unloaded.

kernel/rcutorture.c

+66 −0
Original line number Diff line number Diff line
@@ -67,6 +67,8 @@ static int fqs_stutter = 3; /* Wait time between bursts (s). */ 
static int onoff_interval;	/* Wait time between CPU hotplugs, 0=disable. */

static int onoff_holdoff;	/* Seconds after boot before CPU hotplugs. */

static int shutdown_secs;	/* Shutdown time (s).  <=0 for no shutdown. */

static int stall_cpu;		/* CPU-stall duration (s).  0 for no stall. */

static int stall_cpu_holdoff = 10; /* Time to wait until stall (s).  */

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. */

static int test_boost_duration = 4; /* Duration of each boost test, seconds. */
@@ -100,6 +102,10 @@ module_param(onoff_holdoff, int, 0444); 
MODULE_PARM_DESC(onoff_holdoff, "Time after boot before CPU hotplugs (s)");

module_param(shutdown_secs, int, 0444);

MODULE_PARM_DESC(shutdown_secs, "Shutdown time (s), zero to disable.");

module_param(stall_cpu, int, 0444);

MODULE_PARM_DESC(stall_cpu, "Stall duration (s), zero to disable.");

module_param(stall_cpu_holdoff, int, 0444);

MODULE_PARM_DESC(stall_cpu_holdoff, "Time to wait before starting stall (s).");

module_param(test_boost, int, 0444);

MODULE_PARM_DESC(test_boost, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");

module_param(test_boost_interval, int, 0444);
@@ -132,6 +138,7 @@ static struct task_struct *shutdown_task; 
#ifdef CONFIG_HOTPLUG_CPU

static struct task_struct *onoff_task;

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

static struct task_struct *stall_task;



#define RCU_TORTURE_PIPE_LEN 10
@@ -1489,6 +1496,63 @@ static void rcu_torture_onoff_cleanup(void) 


#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */



/*

 * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then

 * induces a CPU stall for the time specified by stall_cpu.

 */

static int __cpuinit rcu_torture_stall(void *args)

{

	unsigned long stop_at;



	VERBOSE_PRINTK_STRING("rcu_torture_stall task started");

	if (stall_cpu_holdoff > 0) {

		VERBOSE_PRINTK_STRING("rcu_torture_stall begin holdoff");

		schedule_timeout_interruptible(stall_cpu_holdoff * HZ);

		VERBOSE_PRINTK_STRING("rcu_torture_stall end holdoff");

	}

	if (!kthread_should_stop()) {

		stop_at = get_seconds() + stall_cpu;

		/* RCU CPU stall is expected behavior in following code. */

		printk(KERN_ALERT "rcu_torture_stall start.\n");

		rcu_read_lock();

		preempt_disable();

		while (ULONG_CMP_LT(get_seconds(), stop_at))

			continue;  /* Induce RCU CPU stall warning. */

		preempt_enable();

		rcu_read_unlock();

		printk(KERN_ALERT "rcu_torture_stall end.\n");

	}

	rcutorture_shutdown_absorb("rcu_torture_stall");

	while (!kthread_should_stop())

		schedule_timeout_interruptible(10 * HZ);

	return 0;

}



/* Spawn CPU-stall kthread, if stall_cpu specified. */

static int __init rcu_torture_stall_init(void)

{

	int ret;



	if (stall_cpu <= 0)

		return 0;

	stall_task = kthread_run(rcu_torture_stall, NULL, "rcu_torture_stall");

	if (IS_ERR(stall_task)) {

		ret = PTR_ERR(stall_task);

		stall_task = NULL;

		return ret;

	}

	return 0;

}



/* Clean up after the CPU-stall kthread, if one was spawned. */

static void rcu_torture_stall_cleanup(void)

{

	if (stall_task == NULL)

		return;

	VERBOSE_PRINTK_STRING("Stopping rcu_torture_stall_task.");

	kthread_stop(stall_task);

}



static int rcutorture_cpu_notify(struct notifier_block *self,

				 unsigned long action, void *hcpu)

{
@@ -1531,6 +1595,7 @@ rcu_torture_cleanup(void) 
	fullstop = FULLSTOP_RMMOD;

	mutex_unlock(&fullstop_mutex);

	unregister_reboot_notifier(&rcutorture_shutdown_nb);

	rcu_torture_stall_cleanup();

	if (stutter_task) {

		VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");

		kthread_stop(stutter_task);
@@ -1831,6 +1896,7 @@ rcu_torture_init(void) 
	}

	rcu_torture_onoff_init();

	register_reboot_notifier(&rcutorture_shutdown_nb);

	rcu_torture_stall_init();

	rcutorture_record_test_transition();

	mutex_unlock(&fullstop_mutex);

	return 0;

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