From: bsegall@google.com
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] sched/fair: do not announce throttled next buddy in dequeue_task_fair
Date: Thu, 16 Jun 2016 10:06:00 -0700 [thread overview]
Message-ID: <xm26k2hpvzbb.fsf@bsegall-linux.mtv.corp.google.com> (raw)
In-Reply-To: <146608183552.21905.15924473394414832071.stgit@buzz> (Konstantin Khlebnikov's message of "Thu, 16 Jun 2016 15:57:15 +0300")
Konstantin Khlebnikov <khlebnikov@yandex-team.ru> writes:
> Hierarchy could be already throttled at this point. Throttled next
> buddy could trigger null pointer dereference in pick_next_task_fair().
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Ben Segall <bsegall@google.com>
> Cc: Stable <stable@vger.kernel.org> # v3.2+
> ---
> kernel/sched/fair.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index fe809fe169d2..3c6b038cb734 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4519,15 +4519,14 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>
> /* Don't dequeue parent if it has other entities besides us */
> if (cfs_rq->load.weight) {
> + /* avoid re-evaluating load for this entity */
> + se = parent_entity(se);
> /*
> * Bias pick_next to pick a task from this cfs_rq, as
> * p is sleeping when it is within its sched_slice.
> */
> - if (task_sleep && parent_entity(se))
> - set_next_buddy(parent_entity(se));
> -
> - /* avoid re-evaluating load for this entity */
> - se = parent_entity(se);
> + if (task_sleep && se && !throttled_hierarchy(cfs_rq))
> + set_next_buddy(se);
> break;
> }
> flags |= DEQUEUE_SLEEP;
next prev parent reply other threads:[~2016-06-16 17:06 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 12:57 [PATCH] sched/fair: do not announce throttled next buddy in dequeue_task_fair Konstantin Khlebnikov
2016-06-16 17:06 ` bsegall [this message]
2016-06-21 13:44 ` Konstantin Khlebnikov
2016-06-24 9:00 ` [tip:sched/urgent] sched/fair: Do not announce throttled next buddy in dequeue_task_fair() tip-bot for Konstantin Khlebnikov
2016-07-11 7:25 ` [PATCH] sched/fair: do not announce throttled next buddy in dequeue_task_fair Wanpeng Li
2016-07-11 8:15 ` Konstantin Khlebnikov
2016-07-11 8:22 ` Xunlei Pang
2016-07-11 8:42 ` Xunlei Pang
2016-07-11 9:54 ` Wanpeng Li
2016-07-11 12:12 ` Xunlei Pang
2016-07-11 12:26 ` Konstantin Khlebnikov
2016-07-12 17:25 ` bsegall
2016-07-13 1:50 ` Wanpeng Li
2016-07-13 1:58 ` Xunlei Pang
2016-07-13 2:14 ` Wanpeng Li
2016-07-13 17:06 ` bsegall
2016-07-14 12:11 ` Wanpeng Li
2016-07-14 17:54 ` bsegall
2016-07-14 22:30 ` Wanpeng Li
2016-07-14 22:49 ` bsegall
2016-07-14 23:03 ` Wanpeng Li
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