[PATCH tip/core/rcu 05/28] torture: Make torture_stutter() use hrtimer

paulmck
2020-11-05T23:48:15Z

The torture_stutter() function uses schedule_timeout_interruptible()
to time the stutter duration, but this can miss race conditions due to
its being time-synchronized with everything else that is based on the
timer wheels. This commit therefore converts torture_stutter() to use
the high-resolution timers via schedule_hrtimeout(), and also to fuzz
the stutter interval. While in the area, this commit also limits the
spin-loop portion of the stutter_wait() function's wait loop to two
jiffies, down from about one second.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/torture.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/kernel/torture.c b/kernel/torture.c
index 5488ad2..d8bdd9a 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -641,20 +641,27 @@ EXPORT_SYMBOL_GPL(stutter_wait);
*/
static int torture_stutter(void *arg)
{
+ ktime_t delay;
+ DEFINE_TORTURE_RANDOM(rand);
int wtime;

VERBOSE_TOROUT_STRING("torture_stutter task started");
do {
if (!torture_must_stop() && stutter > 1) {
wtime = stutter;
- if (stutter > HZ + 1) {
+ if (stutter > 2) {
WRITE_ONCE(stutter_pause_test, 1);
- wtime = stutter - HZ - 1;
- schedule_timeout_interruptible(wtime);
- wtime = HZ + 1;
+ wtime = stutter - 3;
+ delay = ktime_divns(NSEC_PER_SEC * wtime, HZ);
+ delay += (torture_random(&rand) >> 3) % NSEC_PER_MSEC;
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_hrtimeout(&delay, HRTIMER_MODE_REL);
+ wtime = 2;
}
WRITE_ONCE(stutter_pause_test, 2);
- schedule_timeout_interruptible(wtime);
+ delay = ktime_divns(NSEC_PER_SEC * wtime, HZ);
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_hrtimeout(&delay, HRTIMER_MODE_REL);
}
WRITE_ONCE(stutter_pause_test, 0);
if (!torture_must_stop())
--
2.9.5