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| author | Mike Galbraith <efault@gmx.de> | 2009-10-09 08:35:03 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-10-09 15:58:11 +0200 |
| commit | f5dc37530ba8a35aae0f7f4f13781d1904f71e94 (patch) | |
| tree | 866894f6bf41876a7c6096912c82e73d140d3071 /kernel | |
| parent | 36a07902c2134649c4af7f07980413ffb1a56085 (diff) | |
| download | lwn-f5dc37530ba8a35aae0f7f4f13781d1904f71e94.tar.gz lwn-f5dc37530ba8a35aae0f7f4f13781d1904f71e94.zip | |
sched: Update the clock of runqueue select_task_rq() selected
In try_to_wake_up(), we update the runqueue clock, but
select_task_rq() may select a different runqueue than the one we
updated, leaving the new runqueue's clock stale for a bit.
This patch cures occasional huge latencies reported by latencytop
when coming out of idle on a mostly idle NO_HZ box.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1255070103.7639.30.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 76c0e9691fc0..e3f8f4f61c8e 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2311,7 +2311,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, { int cpu, orig_cpu, this_cpu, success = 0; unsigned long flags; - struct rq *rq; + struct rq *rq, *orig_rq; if (!sched_feat(SYNC_WAKEUPS)) wake_flags &= ~WF_SYNC; @@ -2319,7 +2319,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, this_cpu = get_cpu(); smp_wmb(); - rq = task_rq_lock(p, &flags); + rq = orig_rq = task_rq_lock(p, &flags); update_rq_clock(rq); if (!(p->state & state)) goto out; @@ -2350,6 +2350,10 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, set_task_cpu(p, cpu); rq = task_rq_lock(p, &flags); + + if (rq != orig_rq) + update_rq_clock(rq); + WARN_ON(p->state != TASK_WAKING); cpu = task_cpu(p); |