torture: Make torture_stutter() use hrtimer

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>

diff --git a/kernel/torture.c b/kernel/torture.c
index be09377af6bcd6f43251396ca2811ce697232fdc..56ff02bf444ff21893721287b9f0f9537cfab0a5 100644 (file)
--- 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())