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authorDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>2011-12-15 14:37:41 +0900
committerIngo Molnar <mingo@elte.hu>2011-12-21 10:34:52 +0100
commit62af3783e4fd8ba9e28416e8e91cb3bdd9fb133e (patch)
tree728bed51d0ae2725ade8046ba83794dd5f9944e4 /kernel/sched
parent7ceff013c43c0f38f0d26c79507889c6791c0ea0 (diff)
sched: Fix cgroup movement of waking process
There is a small race between try_to_wake_up() and sched_move_task(), which is trying to move the process being woken up. try_to_wake_up() on CPU0 sched_move_task() on CPU1 --------------------------------+--------------------------------- raw_spin_lock_irqsave(p->pi_lock) task_waking_fair() ->p.se.vruntime -= cfs_rq->min_vruntime ttwu_queue() ->send reschedule IPI to CPU1 raw_spin_unlock_irqsave(p->pi_lock) task_rq_lock() -> tring to aquire both p->pi_lock and rq->lock with IRQ disabled task_move_group_fair() -> p.se.vruntime -= (old)cfs_rq->min_vruntime += (new)cfs_rq->min_vruntime task_rq_unlock() (via IPI) sched_ttwu_pending() raw_spin_lock(rq->lock) ttwu_do_activate() ... enqueue_entity() child.se->vruntime += cfs_rq->min_vruntime raw_spin_unlock(rq->lock) As a result, vruntime of the process becomes far bigger than min_vruntime, if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime. This patch fixes this problem by just ignoring such process in task_move_group_fair(), because the vruntime has already been normalized in task_waking_fair(). Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/20111215143741.df82dd50.nishimura@mxp.nes.nec.co.jp Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/fair.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2d1ac6e2386d..bdf18836f74e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5344,11 +5344,13 @@ static void task_move_group_fair(struct task_struct *p, int on_rq)
*
* - Moving a forked child which is waiting for being woken up by
* wake_up_new_task().
+ * - Moving a task which has been woken up by try_to_wake_up() and
+ * waiting for actually being woken up by sched_ttwu_pending().
*
* To prevent boost or penalty in the new cfs_rq caused by delta
* min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
*/
- if (!on_rq && !p->se.sum_exec_runtime)
+ if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
on_rq = 1;
if (!on_rq)