Messages in this thread | | | Date | Mon, 2 May 2022 18:40:36 +0100 | Subject | Re: [REGRESSION] lxc-stop hang on 5.17.x kernels | From | Pavel Begunkov <> |
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On 5/2/22 18:00, Jens Axboe wrote: > 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:
Same here, it doesn't reproduce for me
> # 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.
-- Pavel Begunkov
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