Re: [REGRESSION] lxc-stop hang on 5.17.x kernels

[Daniel Harding]

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.

--
Regards,

Daniel Harding