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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: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2012-01-20 15:36:33 -08:00 committed by Paul E. McKenney
parent 105617da8d
commit c13f3757d0
2 changed files with 84 additions and 0 deletions
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18
Documentation/RCU/torture.txt
View File

@ -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.

66
kernel/rcutorture.c
View File

@ -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;