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rcutorture: Permit holding off CPU-hotplug operations during boot 

When rcutorture is started automatically at boot time, it might well
also start CPU-hotplug operations at that time, which might not be
desirable.  This commit therefore adds an rcutorture parameter that
allows CPU-hotplug operations to be held off for the specified number
of seconds after the start of boot.

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 2012-01-17 14:36:51 -08:00 committed by Paul E. McKenney
parent a858af2875
commit 9b9ec9b90e
2 changed files with 21 additions and 4 deletions
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13
Documentation/RCU/torture.txt
View File

@ -69,6 +69,13 @@ onoff_interval
CPU-hotplug operations regardless of what value is
specified for onoff_interval.
onoff_holdoff The number of seconds to wait until starting CPU-hotplug
operations. This would normally only be used when
rcutorture was built into the kernel and started
automatically at boot time, in which case it is useful
in order to avoid confusing boot-time code with CPUs
coming and going.
shuffle_interval
The number of seconds to keep the test threads affinitied
to a particular subset of the CPUs, defaults to 3 seconds.
@ -277,5 +284,7 @@ The following script may be used to torture RCU:
The output can be manually inspected for the error flag of "!!!".
One could of course create a more elaborate script that automatically
checked for such errors. The "rmmod" command forces a "SUCCESS" or
"FAILURE" indication to be printk()ed.
checked for such errors. The "rmmod" command forces a "SUCCESS",
"FAILURE", or "RCU_HOTPLUG" indication to be printk()ed. The first
two are self-explanatory, while the last indicates that while there
were no RCU failures, CPU-hotplug problems were detected.

12
kernel/rcutorture.c
View File

@ -65,6 +65,7 @@ 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 onoff_holdoff; /* Seconds after boot before CPU hotplugs. */
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. */
@ -95,6 +96,8 @@ 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(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(test_boost, int, 0444);
@ -1300,13 +1303,13 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
"fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
"test_boost=%d/%d test_boost_interval=%d "
"test_boost_duration=%d shutdown_secs=%d "
"onoff_interval=%d\n",
"onoff_interval=%d onoff_holdoff=%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,
onoff_interval);
onoff_interval, onoff_holdoff);
}
static struct notifier_block rcutorture_shutdown_nb = {
@ -1410,6 +1413,11 @@ rcu_torture_onoff(void *arg)
for_each_online_cpu(cpu)
maxcpu = cpu;
WARN_ON(maxcpu < 0);
if (onoff_holdoff > 0) {
VERBOSE_PRINTK_STRING("rcu_torture_onoff begin holdoff");
schedule_timeout_interruptible(onoff_holdoff * HZ);
VERBOSE_PRINTK_STRING("rcu_torture_onoff end holdoff");
}
while (!kthread_should_stop()) {
cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1);
if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {