On Mon, Dec 12, 2011 at 10:59 PM, Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote: > 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 another 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 > ->p.se.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@xxxxxxxxxxxxxxxxx> > --- > kernel/sched_fair.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index bdaa4ab..3feb3a2 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -4925,10 +4925,10 @@ static void task_move_group_fair(struct task_struct *p, int on_rq) > * to another cgroup's rq. This does somewhat interfere with the > * fair sleeper stuff for the first placement, but who cares. > */ > - if (!on_rq && p->state != TASK_RUNNING) > + if (!on_rq && p->state != TASK_RUNNING && p->state != TASK_WAKING) !p->se.sum_exec_runtime is starting to look more attractive here... > p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime; > set_task_rq(p, task_cpu(p)); > - if (!on_rq && p->state != TASK_RUNNING) > + if (!on_rq && p->state != TASK_RUNNING && p->state != TASK_WAKING) > p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime; > } > #endif > -- > 1.7.1 > > -- > To unsubscribe from this list: send the line "unsubscribe cgroups" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
