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authorPaul E. McKenney <paulmck@kernel.org>2020-09-01 16:58:41 -0700
committerPaul E. McKenney <paulmck@kernel.org>2020-11-06 17:13:48 -0800
commit19012b786ecccb29a9fa20c4ec0a67e2cdfbc010 (patch)
treea4c362ff79e925b3f63dc1ea03218d7d0fdae6eb /kernel/torture.c
parent3480d6774f07341e3e1cf3114f58bef98ea58ae0 (diff)
torture: Periodically pause in stutter_wait()
Running locktorture scenario LOCK05 results in hangs: tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --torture lock --duration 3 --configs LOCK05 The lock_torture_writer() kthreads set themselves to MAX_NICE while running SCHED_OTHER. Other locktorture kthreads run at default niceness, also SCHED_OTHER. This results in these other locktorture kthreads indefinitely preempting the lock_torture_writer() kthreads. Note that the cond_resched() in the stutter_wait() function's loop is ineffective because this scenario is built with CONFIG_PREEMPT=y. It is not clear that such indefinite preemption is supposed to happen, but in the meantime this commit prevents kthreads running in stutter_wait() from being completely CPU-bound, thus allowing the other threads to get some CPU in a timely fashion. This commit also uses hrtimers to provide very short sleeps to avoid degrading the sudden-on testing that stutter is supposed to provide. Reviewed-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/torture.c')
-rw-r--r--kernel/torture.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/kernel/torture.c b/kernel/torture.c
index 1061492f14bd..be09377af6bc 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -602,8 +602,11 @@ static int stutter_gap;
*/
bool stutter_wait(const char *title)
{
- int spt;
+ ktime_t delay;
+ unsigned int i = 0;
+ int oldnice;
bool ret = false;
+ int spt;
cond_resched_tasks_rcu_qs();
spt = READ_ONCE(stutter_pause_test);
@@ -612,8 +615,17 @@ bool stutter_wait(const char *title)
if (spt == 1) {
schedule_timeout_interruptible(1);
} else if (spt == 2) {
- while (READ_ONCE(stutter_pause_test))
+ oldnice = task_nice(current);
+ set_user_nice(current, MAX_NICE);
+ while (READ_ONCE(stutter_pause_test)) {
+ if (!(i++ & 0xffff)) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ delay = 10 * NSEC_PER_USEC;
+ schedule_hrtimeout(&delay, HRTIMER_MODE_REL);
+ }
cond_resched();
+ }
+ set_user_nice(current, oldnice);
} else {
schedule_timeout_interruptible(round_jiffies_relative(HZ));
}

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