From: "Michal Koutný" <mkoutny@suse.com>
To: Mathias Krause <minipli@grsecurity.net>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
Odin Ugedal <odin@uged.al>,
Kevin Tanguy <kevin.tanguy@corp.ovh.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: task_group unthrottling and removal race (was Re: [PATCH] sched/fair: Use rq->lock when checking cfs_rq list) presence
Date: Wed, 3 Nov 2021 12:10:36 +0100 [thread overview]
Message-ID: <20211103111036.GA10034@blackbody.suse.cz> (raw)
In-Reply-To: <e2bcfc90-18b6-8da5-517c-023d2242ba97@grsecurity.net>
On Wed, Nov 03, 2021 at 11:51:12AM +0100, Mathias Krause <minipli@grsecurity.net> wrote:
> Adding synchronize_rcu() here will ensure all concurrent RCU "readers"
> will have finished what they're doing, so we can unlink safely. That
> was, apparently, the missing piece.
What reader(s) are you referring to here? The
list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
throttled_list) in distribute_cfs_runtime()?
I'm think (not sure) that wouldn't work since the unthrottle_cfs_rq can
still be called after this synchronize_rcu() but before
free_fair_sched_group().
(But if you considered update_blocked_averages() as the reader(s) and
synchronize_rcu() within free_fair_sched_group(), that may ensure UBA
won't step on a free'd cfs_rq (+unlinking would need to happen only in
free_fair_sched_group() too.))
Michal
next prev parent reply other threads:[~2021-11-03 11:10 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-11 17:22 [PATCH] sched/fair: Use rq->lock when checking cfs_rq list presence Michal Koutný
2021-10-11 19:12 ` Odin Ugedal
2021-10-12 18:32 ` Tao Zhou
2021-10-13 18:52 ` Odin Ugedal
2021-10-13 14:39 ` Michal Koutný
2021-10-13 18:45 ` Odin Ugedal
2021-10-13 7:57 ` Vincent Guittot
2021-10-13 14:26 ` Michal Koutný
2021-11-02 16:02 ` task_group unthrottling and removal race (was Re: [PATCH] sched/fair: Use rq->lock when checking cfs_rq list) presence Michal Koutný
2021-11-02 20:20 ` Odin Ugedal
2021-11-03 9:51 ` Mathias Krause
2021-11-03 10:51 ` Mathias Krause
2021-11-03 11:10 ` Michal Koutný [this message]
2021-11-03 14:16 ` Mathias Krause
2021-11-03 19:06 ` [PATCH] sched/fair: Prevent dead task groups from regaining cfs_rq's Mathias Krause
2021-11-03 22:03 ` Benjamin Segall
2021-11-04 8:50 ` Vincent Guittot
2021-11-04 15:13 ` Mathias Krause
2021-11-04 16:49 ` Vincent Guittot
2021-11-04 17:37 ` Mathias Krause
2021-11-05 14:25 ` Vincent Guittot
2021-11-05 14:44 ` Mathias Krause
2021-11-05 16:29 ` Mathias Krause
2021-11-05 16:58 ` Peter Zijlstra
2021-11-05 17:14 ` Mathias Krause
2021-11-05 17:27 ` Peter Zijlstra
2021-11-05 17:40 ` Mathias Krause
2021-11-06 10:48 ` Peter Zijlstra
2021-11-08 10:27 ` Mathias Krause
2021-11-08 11:40 ` Peter Zijlstra
2021-11-08 15:06 ` Mathias Krause
2021-11-10 15:14 ` Vincent Guittot
2021-11-09 18:47 ` Michal Koutný
2021-11-10 15:17 ` Vincent Guittot
2021-11-04 20:46 ` Benjamin Segall
2021-11-04 18:49 ` Michal Koutný
2021-11-05 14:55 ` Mathias Krause
2021-11-05 14:58 ` Peter Zijlstra
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