From: Oleg Nesterov <oleg@tv-sign.ru>

sched_exit:

	if (parent->time_slice > task_timeslice(p)))
		parent->time_slice = task_timeslice(p)

I think it should use task_timeslice(parent) instead.

The patch looks complicated, but it is not. It just caches the value
of 'p->parent'.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Con Kolivas <kernel@kolivas.org>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 kernel/sched.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff -puN kernel/sched.c~sched_exit-fix-parent-time_slice-calculation kernel/sched.c
--- a/kernel/sched.c~sched_exit-fix-parent-time_slice-calculation
+++ a/kernel/sched.c
@@ -1606,6 +1606,7 @@ void fastcall wake_up_new_task(task_t *p
  */
 void fastcall sched_exit(task_t *p)
 {
+	task_t *parent = p->parent;
 	unsigned long flags;
 	runqueue_t *rq;
 
@@ -1613,14 +1614,14 @@ void fastcall sched_exit(task_t *p)
 	 * If the child was a (relative-) CPU hog then decrease
 	 * the sleep_avg of the parent as well.
 	 */
-	rq = task_rq_lock(p->parent, &flags);
-	if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) {
-		p->parent->time_slice += p->time_slice;
-		if (unlikely(p->parent->time_slice > task_timeslice(p)))
-			p->parent->time_slice = task_timeslice(p);
+	rq = task_rq_lock(parent, &flags);
+	if (p->first_time_slice && task_cpu(p) == task_cpu(parent)) {
+		parent->time_slice += p->time_slice;
+		if (unlikely(parent->time_slice > task_timeslice(parent)))
+			parent->time_slice = task_timeslice(parent);
 	}
-	if (p->sleep_avg < p->parent->sleep_avg)
-		p->parent->sleep_avg = p->parent->sleep_avg /
+	if (p->sleep_avg < parent->sleep_avg)
+		parent->sleep_avg = parent->sleep_avg /
 		(EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
 		(EXIT_WEIGHT + 1);
 	task_rq_unlock(rq, &flags);
_