diff options
| author | Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> | 2011-12-15 14:37:41 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-12-21 10:34:52 +0100 |
| commit | 62af3783e4fd8ba9e28416e8e91cb3bdd9fb133e (patch) | |
| tree | 728bed51d0ae2725ade8046ba83794dd5f9944e4 /kernel/sched | |
| parent | 7ceff013c43c0f38f0d26c79507889c6791c0ea0 (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.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2d1ac6e2386..bdf18836f74 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) |