From: Jens Axboe <[email protected]>
To: Daniel Harding <[email protected]>,
Pavel Begunkov <[email protected]>
Cc: [email protected], [email protected],
[email protected]
Subject: Re: [REGRESSION] lxc-stop hang on 5.17.x kernels
Date: Mon, 2 May 2022 11:00:38 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 5/2/22 7:59 AM, Jens Axboe wrote:
> On 5/2/22 7:36 AM, Daniel Harding wrote:
>> On 5/2/22 16:26, Jens Axboe wrote:
>>> On 5/2/22 7:17 AM, Daniel Harding wrote:
>>>> I use lxc-4.0.12 on Gentoo, built with io-uring support
>>>> (--enable-liburing), targeting liburing-2.1. My kernel config is a
>>>> very lightly modified version of Fedora's generic kernel config. After
>>>> moving from the 5.16.x series to the 5.17.x kernel series, I started
>>>> noticed frequent hangs in lxc-stop. It doesn't happen 100% of the
>>>> time, but definitely more than 50% of the time. Bisecting narrowed
>>>> down the issue to commit aa43477b040251f451db0d844073ac00a8ab66ee:
>>>> io_uring: poll rework. Testing indicates the problem is still present
>>>> in 5.18-rc5. Unfortunately I do not have the expertise with the
>>>> codebases of either lxc or io-uring to try to debug the problem
>>>> further on my own, but I can easily apply patches to any of the
>>>> involved components (lxc, liburing, kernel) and rebuild for testing or
>>>> validation. I am also happy to provide any further information that
>>>> would be helpful with reproducing or debugging the problem.
>>> Do you have a recipe to reproduce the hang? That would make it
>>> significantly easier to figure out.
>>
>> I can reproduce it with just the following:
>>
>> sudo lxc-create --n lxc-test --template download --bdev dir --dir /var/lib/lxc/lxc-test/rootfs -- -d ubuntu -r bionic -a amd64
>> sudo lxc-start -n lxc-test
>> sudo lxc-stop -n lxc-test
>>
>> The lxc-stop command never exits and the container continues running.
>> If that isn't sufficient to reproduce, please let me know.
>
> Thanks, that's useful! I'm at a conference this week and hence have
> limited amount of time to debug, hopefully Pavel has time to take a look
> at this.
Didn't manage to reproduce. Can you try, on both the good and bad
kernel, to do:
# echo 1 > /sys/kernel/debug/tracing/events/io_uring/enable
run lxc-stop
# cp /sys/kernel/debug/tracing/trace ~/iou-trace
so we can see what's going on? Looking at the source, lxc is just using
plain POLL_ADD, so I'm guessing it's not getting a notification when it
expects to, or it's POLL_REMOVE not doing its job. If we have a trace
from both a working and broken kernel, that might shed some light on it.
--
Jens Axboe
next prev parent reply other threads:[~2022-05-02 17:02 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-02 13:17 [REGRESSION] lxc-stop hang on 5.17.x kernels Daniel Harding
2022-05-02 13:26 ` Jens Axboe
2022-05-02 13:36 ` Daniel Harding
2022-05-02 13:59 ` Jens Axboe
2022-05-02 17:00 ` Jens Axboe [this message]
2022-05-02 17:40 ` Pavel Begunkov
2022-05-02 18:49 ` Daniel Harding
2022-05-02 23:14 ` Pavel Begunkov
2022-05-03 7:37 ` Daniel Harding
2022-05-03 14:14 ` Pavel Begunkov
2022-05-04 6:54 ` Daniel Harding
2022-05-15 8:20 ` Thorsten Leemhuis
2022-05-15 18:34 ` Daniel Harding
2022-05-16 12:12 ` Pavel Begunkov
2022-05-16 13:25 ` Pavel Begunkov
2022-05-16 13:57 ` Daniel Harding
2022-05-16 15:13 ` Daniel Harding
2022-05-16 18:13 ` Pavel Begunkov
2022-05-17 8:19 ` Christian Brauner
2022-05-17 10:31 ` Pavel Begunkov
2022-05-16 18:17 ` Thorsten Leemhuis
2022-05-16 18:22 ` Jens Axboe
2022-05-16 18:34 ` Thorsten Leemhuis
2022-05-16 18:39 ` Jens Axboe
2022-05-16 19:07 ` Thorsten Leemhuis
2022-05-16 19:14 ` Jens Axboe
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