[ipfire-2.x.git] / src / patches / suse-2.6.27.39 / patches.fixes / bug-437171_1_sched_clock_lock.patch

Subject: sched: only update rq->clock while holding rq->lock
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
References: 437171 - LTC47404

Vatsa noticed rq->clock going funny and tracked it down to an update_rq_clock()
outside a rq->lock section.

This is a problem because things like double_rq_lock() update the rq->clock
value for both rqs. Therefore disabling interrupts isn't strong enough.

Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Olaf Hering <olh@suse.de>

---
 kernel/sched.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4449,12 +4449,9 @@ need_resched_nonpreemptible:
 	if (sched_feat(HRTICK))
 		hrtick_clear(rq);
 
-	/*
-	 * Do the rq-clock update outside the rq lock:
-	 */
 	local_irq_disable();
-	update_rq_clock(rq);
 	spin_lock(&rq->lock);
+	update_rq_clock(rq);
 	clear_tsk_need_resched(prev);
 
 	if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
Commit	Line	Data
2cb7cef9 BS	1	Subject: sched: only update rq->clock while holding rq->lock
	2	From: Peter Zijlstra <a.p.zijlstra@chello.nl>
	3	References: 437171 - LTC47404
	4
	5	Vatsa noticed rq->clock going funny and tracked it down to an update_rq_clock()
	6	outside a rq->lock section.
	7
	8	This is a problem because things like double_rq_lock() update the rq->clock
	9	value for both rqs. Therefore disabling interrupts isn't strong enough.
	10
	11	Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
	12	Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
	13	Signed-off-by: Ingo Molnar <mingo@elte.hu>
	14	Signed-off-by: Olaf Hering <olh@suse.de>
	15
	16	---
	17	kernel/sched.c \| 5 +----
	18	1 file changed, 1 insertion(+), 4 deletions(-)
	19
	20	--- a/kernel/sched.c
	21	+++ b/kernel/sched.c
	22	@@ -4449,12 +4449,9 @@ need_resched_nonpreemptible:
	23	if (sched_feat(HRTICK))
	24	hrtick_clear(rq);
	25
	26	- /*
	27	- * Do the rq-clock update outside the rq lock:
	28	- */
	29	local_irq_disable();
	30	- update_rq_clock(rq);
	31	spin_lock(&rq->lock);
	32	+ update_rq_clock(rq);
	33	clear_tsk_need_resched(prev);
	34
	35	if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {