From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> To: LKML <linux-kernel@vger.kernel.org>, cgroups <cgroups@vger.kernel.org> Cc: Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Paul Turner <pjt@google.com>, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Subject: [PATCH 2/3] sched: fix cgroup movement of forking process Date: Thu, 15 Dec 2011 14:36:55 +0900 [thread overview] Message-ID: <20111215143655.662676b0.nishimura@mxp.nes.nec.co.jp> (raw) In-Reply-To: <20111215143506.335e443e.nishimura@mxp.nes.nec.co.jp> There is a small race between task_fork_fair() and sched_move_task(), which is trying to move the parent. task_fork_fair() sched_move_task() --------------------------------+--------------------------------- cfs_rq = task_cfs_rq(current) -> cfs_rq is the "old" one. curr = cfs_rq->curr -> curr is set to the parent. task_rq_lock() dequeue_task() ->parent.se.vruntime -= (old)cfs_rq->min_vruntime enqueue_task() ->parent.se.vruntime += (new)cfs_rq->min_vruntime task_rq_unlock() raw_spin_lock_irqsave(rq->lock) se->vruntime = curr->vruntime -> vruntime of the child is set to that of the parent which has already been updated by sched_move_task(). se->vruntime -= (old)cfs_rq->min_vruntime. raw_spin_unlock_irqrestore(rq->lock) As a result, vruntime of the child becomes far bigger than expected, if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime. This patch fixes this problem by setting "cfs_rq" and "curr" after holding the rq->lock. Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Acked-by: Paul Turner <pjt@google.com> --- kernel/sched/fair.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 43cadd0..b1db01b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5191,8 +5191,8 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) */ static void task_fork_fair(struct task_struct *p) { - struct cfs_rq *cfs_rq = task_cfs_rq(current); - struct sched_entity *se = &p->se, *curr = cfs_rq->curr; + struct cfs_rq *cfs_rq; + struct sched_entity *se = &p->se, *curr; int this_cpu = smp_processor_id(); struct rq *rq = this_rq(); unsigned long flags; @@ -5201,6 +5201,9 @@ static void task_fork_fair(struct task_struct *p) update_rq_clock(rq); + cfs_rq = task_cfs_rq(current); + curr = cfs_rq->curr; + if (unlikely(task_cpu(p) != this_cpu)) { rcu_read_lock(); __set_task_cpu(p, this_cpu); -- 1.7.1
WARNING: multiple messages have this Message-ID (diff)
From: Daisuke Nishimura <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org> To: LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> Cc: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>, Peter Zijlstra <a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org>, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Daisuke Nishimura <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org> Subject: [PATCH 2/3] sched: fix cgroup movement of forking process Date: Thu, 15 Dec 2011 14:36:55 +0900 [thread overview] Message-ID: <20111215143655.662676b0.nishimura@mxp.nes.nec.co.jp> (raw) In-Reply-To: <20111215143506.335e443e.nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org> There is a small race between task_fork_fair() and sched_move_task(), which is trying to move the parent. task_fork_fair() sched_move_task() --------------------------------+--------------------------------- cfs_rq = task_cfs_rq(current) -> cfs_rq is the "old" one. curr = cfs_rq->curr -> curr is set to the parent. task_rq_lock() dequeue_task() ->parent.se.vruntime -= (old)cfs_rq->min_vruntime enqueue_task() ->parent.se.vruntime += (new)cfs_rq->min_vruntime task_rq_unlock() raw_spin_lock_irqsave(rq->lock) se->vruntime = curr->vruntime -> vruntime of the child is set to that of the parent which has already been updated by sched_move_task(). se->vruntime -= (old)cfs_rq->min_vruntime. raw_spin_unlock_irqrestore(rq->lock) As a result, vruntime of the child becomes far bigger than expected, if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime. This patch fixes this problem by setting "cfs_rq" and "curr" after holding the rq->lock. Signed-off-by: Daisuke Nishimura <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org> Acked-by: Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> --- kernel/sched/fair.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 43cadd0..b1db01b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5191,8 +5191,8 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) */ static void task_fork_fair(struct task_struct *p) { - struct cfs_rq *cfs_rq = task_cfs_rq(current); - struct sched_entity *se = &p->se, *curr = cfs_rq->curr; + struct cfs_rq *cfs_rq; + struct sched_entity *se = &p->se, *curr; int this_cpu = smp_processor_id(); struct rq *rq = this_rq(); unsigned long flags; @@ -5201,6 +5201,9 @@ static void task_fork_fair(struct task_struct *p) update_rq_clock(rq); + cfs_rq = task_cfs_rq(current); + curr = cfs_rq->curr; + if (unlikely(task_cpu(p) != this_cpu)) { rcu_read_lock(); __set_task_cpu(p, this_cpu); -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2011-12-15 5:44 UTC|newest] Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-12-13 6:57 [PATCH 0/3] sched: some fixes for vruntime calculation related to cgroup movement Daisuke Nishimura 2011-12-13 6:57 ` Daisuke Nishimura 2011-12-13 6:57 ` [PATCH 1/3] sched: fix cgroup movement of newly created process Daisuke Nishimura 2011-12-13 6:57 ` Daisuke Nishimura 2011-12-13 12:01 ` Paul Turner 2011-12-13 12:01 ` Paul Turner 2011-12-14 1:04 ` Daisuke Nishimura 2011-12-14 1:04 ` Daisuke Nishimura 2011-12-13 12:41 ` Peter Zijlstra 2011-12-13 12:41 ` Peter Zijlstra 2011-12-14 1:05 ` Daisuke Nishimura 2011-12-14 1:05 ` Daisuke Nishimura 2011-12-13 6:58 ` [PATCH 2/3] sched: fix cgroup movement of forking process Daisuke Nishimura 2011-12-13 6:58 ` Daisuke Nishimura 2011-12-13 12:22 ` Paul Turner 2011-12-13 12:22 ` Paul Turner 2011-12-13 6:59 ` [PATCH 3/3] sched: fix cgroup movement of waking process Daisuke Nishimura 2011-12-13 6:59 ` Daisuke Nishimura 2011-12-13 12:24 ` Paul Turner 2011-12-13 12:24 ` Paul Turner 2011-12-15 5:35 ` [PATCH -tip 0/3] sched: some fixes for vruntime calculation related to cgroup movement(v2) Daisuke Nishimura 2011-12-15 5:36 ` [PATCH 1/3] sched: fix cgroup movement of newly created process Daisuke Nishimura 2011-12-15 5:36 ` Daisuke Nishimura 2011-12-21 11:45 ` [tip:sched/core] sched: Fix " tip-bot for Daisuke Nishimura 2011-12-15 5:36 ` Daisuke Nishimura [this message] 2011-12-15 5:36 ` [PATCH 2/3] sched: fix cgroup movement of forking process Daisuke Nishimura 2011-12-21 11:44 ` [tip:sched/core] sched: Fix " tip-bot for Daisuke Nishimura 2011-12-21 17:26 ` Tejun Heo 2011-12-21 17:37 ` Tejun Heo 2011-12-22 1:54 ` Frederic Weisbecker 2011-12-22 2:01 ` Tejun Heo 2011-12-15 5:37 ` [PATCH 3/3] sched: fix cgroup movement of waking process Daisuke Nishimura 2011-12-21 11:45 ` [tip:sched/core] sched: Fix " tip-bot for Daisuke Nishimura 2011-12-19 2:55 ` [PATCH -tip 0/3] sched: some fixes for vruntime calculation related to cgroup movement(v2) Daisuke Nishimura 2011-12-19 2:55 ` Daisuke Nishimura
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