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Date: Mon, 6 Sep 2010 08:52:29 +0200 From: Ingo Molnar <mingo@...e.hu> To: Jack Daniel <wanders.thirst@...il.com> Cc: Peter Zijlstra <peterz@...radead.org>, LKML <linux-kernel@...r.kernel.org>, Mike Galbraith <efault@....de>, pjohn@...sta.com Subject: Re: clock drift in set_task_cpu() * Jack Daniel <wanders.thirst@...il.com> wrote: > Hi Ingo, > > [...] > > Any chance that you will be pulling in this fix ? It's already upstream, as of v2.6.36-rc3. See the commit notification email below from Aug 19. Thanks, Ingo ----- Forwarded message from tip-bot for Peter Zijlstra <peterz@...radead.org> ----- Date: Fri, 20 Aug 2010 14:16:14 GMT From: tip-bot for Peter Zijlstra <peterz@...radead.org> To: linux-tip-commits@...r.kernel.org Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com, a.p.zijlstra@...llo.nl, peterz@...radead.org, pjohn@...sta.com, wanders.thirst@...il.com, tglx@...utronix.de, mingo@...e.hu Subject: [tip:sched/urgent] sched: Fix rq->clock synchronization when migrating tasks Commit-ID: 861d034ee814917a83bd5de4b26e3b8336ddeeb8 Gitweb: http://git.kernel.org/tip/861d034ee814917a83bd5de4b26e3b8336ddeeb8 Author: Peter Zijlstra <peterz@...radead.org> AuthorDate: Thu, 19 Aug 2010 13:31:43 +0200 Committer: Ingo Molnar <mingo@...e.hu> CommitDate: Fri, 20 Aug 2010 14:59:01 +0200 sched: Fix rq->clock synchronization when migrating tasks sched_fork() -- we do task placement in ->task_fork_fair() ensure we update_rq_clock() so we work with current time. We leave the vruntime in relative state, so the time delay until wake_up_new_task() doesn't matter. wake_up_new_task() -- Since task_fork_fair() left p->vruntime in relative state we can safely migrate, the activate_task() on the remote rq will call update_rq_clock() and causes the clock to be synced (enough). Tested-by: Jack Daniel <wanders.thirst@...il.com> Tested-by: Philby John <pjohn@...sta.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl> LKML-Reference: <1281002322.1923.1708.camel@...top> Signed-off-by: Ingo Molnar <mingo@...e.hu> --- kernel/sched_fair.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 806d1b2..ab661eb 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -3752,6 +3752,8 @@ static void task_fork_fair(struct task_struct *p) raw_spin_lock_irqsave(&rq->lock, flags); + update_rq_clock(rq); + if (unlikely(task_cpu(p) != this_cpu)) __set_task_cpu(p, this_cpu); ----- End forwarded message ----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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