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

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Message-ID: <d9c00f01-576c-46cd-a88c-76e244460dac@gmail.com>
Date: Tue, 9 Jul 2024 20:55:43 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Oleg Nesterov <oleg@...hat.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 7/9/24 20:38, Oleg Nesterov wrote:
> On 07/09, Pavel Begunkov wrote:
>>
>> On 7/9/24 20:07, Oleg Nesterov wrote:
>>> Hi Tejun,
>>>
>>> Thanks for looking at this, can you review this V2 patch from Pavel?
> 
> Just in case, I obviously meant our next (V2) patch
> 
> [PATCH v2 2/2] kernel: rerun task_work while freezing in get_signal()
> https://lore.kernel.org/all/149ff5a762997c723880751e8a4019907a0b6457.1720534425.git.asml.silence@gmail.com/
> 
>>> Well, I don't really understand what can snapshot/restore actually mean...
>>
>> CRIU, I assume. I'll try it ...
> 
> Than I think we can forget about task_works and this patch. CRIU dumps
> the tasks in TASK_TRACED state.

And would be hard to test, io_uring (the main source of task_work)
is not supported

(00.466022) Error (criu/proc_parse.c:477): Unknown shit 600 (anon_inode:[io_uring])
...
(00.467642) Unfreezing tasks into 1
(00.467656)     Unseizing 15488 into 1
(00.468149) Error (criu/cr-dump.c:2111): Dumping FAILED.


>> ... but I'm inclined to think the patch makes sense regardless,
>> we're replacing an infinite loop with wait-wake-execute-wait.
> 
> Agreed.

-- 
Pavel Begunkov