On an SMP system, a task can awaken on a different cpu from where it
went to sleep. Timestamp inaccuracies can result from the attempt to
compensate for clock drift. Ignore resulting timewarps.
Signed-off-by: Mike Galbraith <[email protected]>
--- linux-2.6.16-mm2/kernel/sched.c-0.fix_rt 2006-03-23 15:01:41.000000000 +0100
+++ linux-2.6.16-mm2/kernel/sched.c 2006-03-23 15:02:25.000000000 +0100
@@ -845,6 +845,15 @@ static int recalc_task_prio(task_t *p, u
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;
+ /*
+ * On SMP systems, a task can go to sleep on one CPU
+ * and wake up on another. When this happens, now can
+ * end up being less than p->timestamp for short sleeps.
+ * Ignore these, they're insignificant.
+ */
+ if (unlikely(now < p->timestamp))
+ __sleep_time = 0;
+
if (batch_task(p))
sleep_time = 0;
else {
-
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