linux-kernel - Re: [PATCH 2/2] kernel: rerun task_work while freezing in get

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Message-ID: <20240710191015.GC9228@redhat.com>
Date: Wed, 10 Jul 2024 21:10:16 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Pavel Begunkov <asml.silence@...il.com>
Cc: Tejun Heo <tj@...nel.org>, io-uring@...r.kernel.org,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christian Brauner <brauner@...nel.org>,
	Tycho Andersen <tandersen@...flix.com>,
	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	Julian Orth <ju.orth@...il.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 2/2] kernel: rerun task_work while freezing in
 get_signal()

On 07/10, Pavel Begunkov wrote:
>
> On 7/10/24 01:54, Tejun Heo wrote:
> >Yeah, the question is: If CRIU is to use cgroup freezer to freeze the tasks
> >and then go around tracing each to make dump, would the freezer be enough in
> >avoiding interim state changes? Using CRIU implementation is a bit arbitrary
> >but I think checkpoint-restart is a useful bar to measure what should stay
> >stable while a cgroup is frozen.
>
> Sounds like in the long run we might want to ignore task_work while
> it's frozen,

Just in case, this is what I have in mind right now, but I am still not sure
and can't make a "clean" patch.

If nothing else. CRIU needs to attach and make this task TASK_TRACED, right?
And once the target task is traced, it won't react to task_work_add(TWA_SIGNAL).

Oleg.