Commit-ID: f5dc37530ba8a35aae0f7f4f13781d1904f71e94 Gitweb: http://git.kernel.org/tip/f5dc37530ba8a35aae0f7f4f13781d1904f71e94 Author: Mike Galbraith <efault@xxxxxx> AuthorDate: Fri, 9 Oct 2009 08:35:03 +0200 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Fri, 9 Oct 2009 15:58:11 +0200 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@xxxxxx> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> LKML-Reference: <1255070103.7639.30.camel@xxxxxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- kernel/sched.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 76c0e96..e3f8f4f 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); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html