From: Peter Zijlstra <peterz@infradead.org>
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] sched/fair: initialize throttle_count for new task-groups lazily
Date: Tue, 21 Jun 2016 23:10:54 +0200 [thread overview]
Message-ID: <20160621211054.GV30154@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <146608182119.21870.8439834428248129633.stgit@buzz>
On Thu, Jun 16, 2016 at 03:57:01PM +0300, Konstantin Khlebnikov wrote:
> Cgroup created inside throttled group must inherit current throttle_count.
> Broken throttle_count allows to nominate throttled entries as a next buddy,
> later this leads to null pointer dereference in pick_next_task_fair().
>
> This patch initialize cfs_rq->throttle_count at first enqueue: laziness
> allows to skip locking all rq at group creation. Lazy approach also allows
> to skip full sub-tree scan at throttling hierarchy (not in this patch).
You're talking about taking rq->lock in alloc_fair_sched_group(), right?
We're about to go do that anyway... But I suppose for backports this
makes sense. Doing it at creation time also avoids the issues Ben
raised, right?
next prev parent reply other threads:[~2016-06-21 21:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 12:57 [PATCH] sched/fair: initialize throttle_count for new task-groups lazily Konstantin Khlebnikov
2016-06-16 17:03 ` bsegall
2016-06-16 17:23 ` Konstantin Khlebnikov
2016-06-16 17:33 ` bsegall
2016-06-21 13:41 ` Konstantin Khlebnikov
2016-06-21 21:10 ` Peter Zijlstra [this message]
2016-06-22 8:10 ` Konstantin Khlebnikov
2016-06-22 8:23 ` Peter Zijlstra
2016-06-24 8:59 ` [tip:sched/urgent] sched/fair: Initialize " tip-bot for Konstantin Khlebnikov
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