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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@gmail.com>
Tested-by: Philby John <pjohn@mvista.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1281002322.1923.1708.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-08-19 13:31:43 +02:00 committed by Ingo Molnar
parent 763008c435
commit 861d034ee8
1 changed files with 2 additions and 0 deletions
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2
kernel/sched_fair.c
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@ -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);