The following commit has been merged into the core/rcu branch of tip:
Commit-ID: 19012b786ecccb29a9fa20c4ec0a67e2cdfbc010
Gitweb:
https://git.kernel.org/tip/19012b786ecccb29a9fa20c4ec0a67e2cdfbc010
Author: Paul E. McKenney <paul...@kernel.org>
AuthorDate: Tue, 01 Sep 2020 16:58:41 -07:00
Committer: Paul E. McKenney <paul...@kernel.org>
CommitterDate: Fri, 06 Nov 2020 17:13:48 -08:00
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 <dbu...@suse.de>
Signed-off-by: Paul E. McKenney <paul...@kernel.org>
---
kernel/torture.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/kernel/torture.c b/kernel/torture.c
index 1061492..be09377 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));
}
