From 64c0d770b67e0bdab7addafd1e19cdcd94be87e3 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 19 Aug 2010 13:31:43 +0200 Subject: [PATCH] sched: Fix rq->clock synchronization when migrating tasks commit 861d034ee814917a83bd5de4b26e3b8336ddeeb8 upstream. 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 Tested-by: Philby John Signed-off-by: Peter Zijlstra LKML-Reference: <1281002322.1923.1708.camel@laptop> Signed-off-by: Ingo Molnar Signed-off-by: Paul Gortmaker --- kernel/sched_fair.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 684e173c00f47..461d312d54db4 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -3588,6 +3588,8 @@ 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); -- 2.47.3