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[72.132.29.68]) by smtp.gmail.com with ESMTPSA id u4-20020aa78484000000b0050dc762813dsm2176532pfn.23.2022.05.02.06.59.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 May 2022 06:59:49 -0700 (PDT) Message-ID: Date: Mon, 2 May 2022 07:59:47 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [REGRESSION] lxc-stop hang on 5.17.x kernels Content-Language: en-US To: Daniel Harding , Pavel Begunkov Cc: regressions@lists.linux.dev, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <7925e262-e0d4-6791-e43b-d37e9d693414@living180.net> <6ad38ecc-b2a9-f0e9-f7c7-f312a2763f97@kernel.dk> From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 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. -- Jens Axboe