Re: Stalls when starting a VSOCK listening socket: soft lockups, RCU stalls, timeout

Matthieu Baerts
2026-03-10T15:51:45Z

On 10/03/2026 14:47, Thomas Gleixner wrote:
> On Tue, Mar 10 2026 at 14:40, Matthieu Baerts wrote:
>> On 10/03/2026 13:28, Thomas Gleixner wrote:
>>
>> (...)
>>
>>> I've updated the debug patch and removed the @users conditionals so it
>>> keeps searching. So it should find that magic 73.
>>
>> It looks like it does, thank you! I just tried this new debug patch, and
>> I managed to boot 100 times without issues, while before I was getting
>> it after max 20 attempts. I left the test running to boot up to 1000
>> times, just in case.
>
> Now that I actually understood the problem, I was able to write a
> reproducer which triggers the issue 100% reliable.
>
> The debug patch does cure it and it does the right thing. I have a
> better version of that in testing right now which avoid all that flaky
> accounting and especially in the vfork() case the full tasklist walk.
> I'll send out a complete patch series with changelogs etc. later.

Great, thank you!

Note that my 1000 boot iteration finished without errors.

> Thanks a lot for your patience and invaluable help. Very appreciated!

My pleasure! Thank you for your support, and for maintaining so many
important pieces in the Linux kernel!

Cheers,
Matt
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