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From: Tejun Heo <tj@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	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>,
	Valentin Schneider <vschneid@redhat.com>,
	Zefan Li <lizefan.x@bytedance.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Will Deacon <will@kernel.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v4 3/3] cgroup/cpuset: Keep user set cpus affinity
Date: Tue, 16 Aug 2022 07:52:51 -1000	[thread overview]
Message-ID: <YvvZc7KgZT/bRoKl@slm.duckdns.org> (raw)
In-Reply-To: <349849aa-937d-8b08-a836-7c5c70168139@redhat.com>

Hello,

On Tue, Aug 16, 2022 at 01:38:17PM -0400, Waiman Long wrote:
> Yes, a race like this is possible. To completely eliminate the race may
> require taking task_rq_lock() and then calling
> __set_cpus_allowed_ptr_locked() which is internal to kernel/sched/core.c.
> 
> Alternatively, we can check user_cpus_ptr again after the scond
> set_cpus_allowed_ptr() and retry it with the other path if set. That will
> probably address your concern. Please let me know if you are OK with that.

I think this would look better if structured the other way around - make the
scheduler side call out to cpuset to query the current restrictions and
apply it atomically.

Thanks.

-- 
tejun

  reply	other threads:[~2022-08-16 17:53 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-16 15:11 [PATCH v4 0/3] sched, " Waiman Long
2022-08-16 15:11 ` [PATCH v4 1/3] sched: Use user_cpus_ptr for saving user provided cpumask in sched_setaffinity() Waiman Long
2022-08-16 15:11 ` [PATCH v4 2/3] sched: Provide copy_user_cpus_mask() to copy out user mask Waiman Long
2022-08-16 15:11 ` [PATCH v4 3/3] cgroup/cpuset: Keep user set cpus affinity Waiman Long
2022-08-16 17:20   ` Tejun Heo
2022-08-16 17:38     ` Waiman Long
2022-08-16 17:52       ` Tejun Heo [this message]
2022-08-16 18:20         ` Waiman Long

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