From: Tejun Heo <tj@kernel.org>
To: Pavel Begunkov <asml.silence@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>,
io-uring@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Andrew Morton <akpm@linux-foundation.org>,
Christian Brauner <brauner@kernel.org>,
Tycho Andersen <tandersen@netflix.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, Julian Orth <ju.orth@gmail.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/2] kernel: rerun task_work while freezing in get_signal()
Date: Tue, 9 Jul 2024 06:39:17 -1000 [thread overview]
Message-ID: <Zo1ntduTPiF8Gmfl@slm.duckdns.org> (raw)
In-Reply-To: <658da3fe-fa02-423b-aff0-52f54e1332ee@gmail.com>
Hello,
On Tue, Jul 09, 2024 at 03:05:21PM +0100, Pavel Begunkov wrote:
> > -----------------------------------------------------------------------
> > Either way I have no idea whether a cgroup_task_frozen() task should
> > react to task_work_add(TWA_SIGNAL) or not.
> >
> > Documentation/admin-guide/cgroup-v2.rst says
> >
> > Writing "1" to the file causes freezing of the cgroup and all
> > descendant cgroups. This means that all belonging processes will
> > be stopped and will not run until the cgroup will be explicitly
> > unfrozen.
> >
> > AFAICS this is not accurate, they can run but can't return to user-mode.
> > So I guess task_work_run() is fine.
>
> IIUC it's a user facing doc, so maybe it's accurate enough from that
> perspective. But I do agree that the semantics around task_work is
> not exactly clear.
A good correctness test for cgroup freezer is whether it'd be safe to
snapshot and restore the tasks in the cgroup while frozen. If that works,
it's most likely fine.
Thanks.
--
tejun
next prev parent reply other threads:[~2024-07-09 16:39 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-07 16:32 [PATCH 0/2] fix task_work interation with freezing Pavel Begunkov
2024-07-07 16:32 ` [PATCH 1/2] io_uring/io-wq: limit retrying worker initialisation Pavel Begunkov
2024-07-07 16:32 ` [PATCH 2/2] kernel: rerun task_work while freezing in get_signal() Pavel Begunkov
2024-07-08 10:42 ` Oleg Nesterov
2024-07-08 15:40 ` Pavel Begunkov
2024-07-08 18:48 ` Peter Zijlstra
2024-07-09 10:36 ` Oleg Nesterov
2024-07-09 14:05 ` Pavel Begunkov
2024-07-09 16:39 ` Tejun Heo [this message]
2024-07-09 19:07 ` Oleg Nesterov
2024-07-09 19:26 ` Pavel Begunkov
2024-07-09 19:38 ` Oleg Nesterov
2024-07-09 19:55 ` Pavel Begunkov
2024-07-10 0:54 ` Tejun Heo
2024-07-10 17:53 ` Pavel Begunkov
2024-07-10 19:10 ` Oleg Nesterov
2024-07-10 19:20 ` Tejun Heo
2024-07-10 21:34 ` Oleg Nesterov
2024-07-10 22:01 ` Tejun Heo
2024-07-10 22:17 ` Oleg Nesterov
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