From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from wp530.webpack.hosteurope.de (wp530.webpack.hosteurope.de [80.237.130.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4522E1376 for ; Mon, 16 May 2022 18:34:21 +0000 (UTC) Received: from [2a02:8108:963f:de38:eca4:7d19:f9a2:22c5]; authenticated by wp530.webpack.hosteurope.de running ExIM with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) id 1nqfXu-0001nq-QR; Mon, 16 May 2022 20:34:18 +0200 Message-ID: <1ce76b24-9185-6b2e-844e-d6a0ce42bb0f@leemhuis.info> Date: Mon, 16 May 2022 20:34:17 +0200 Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [REGRESSION] lxc-stop hang on 5.17.x kernels Content-Language: en-US To: Jens Axboe , Daniel Harding , Pavel Begunkov Cc: regressions@lists.linux.dev, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Christian Brauner References: <7925e262-e0d4-6791-e43b-d37e9d693414@living180.net> <6ad38ecc-b2a9-f0e9-f7c7-f312a2763f97@kernel.dk> <371c01dd-258c-e428-7428-ff390b664752@kernel.dk> <2436d42c-85ca-d060-6508-350c769804f1@gmail.com> <12a57dd9-4423-a13d-559b-2b1dd2fb0ef3@living180.net> <897dc597-fc0a-34ec-84b8-7e1c4901e0fc@leemhuis.info> <41c86189-0d1f-60f0-ca8e-f80b3ccf5130@gmail.com> <3fc08243-f9e0-9cec-4207-883c55ccff78@living180.net> <13028ff4-3565-f09e-818c-19e5f95fa60f@living180.net> <469e5a9b-c7e0-6365-c353-d831ff1c5071@leemhuis.info> From: Thorsten Leemhuis In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-bounce-key: webpack.hosteurope.de;regressions@leemhuis.info;1652726061;02ccf4ca; X-HE-SMSGID: 1nqfXu-0001nq-QR On 16.05.22 20:22, Jens Axboe wrote: > On 5/16/22 12:17 PM, Thorsten Leemhuis wrote: >>>> Pavel, I had actually just started a draft email with the same theory >>>> (although you stated it much more clearly than I could have). I'm >>>> working on debugging the LXC side, but I'm pretty sure the issue is >>>> due to LXC using blocking reads and getting stuck exactly as you >>>> describe. If I can confirm this, I'll go ahead and mark this >>>> regression as invalid and file an issue with LXC. Thanks for your help >>>> and patience. >>> >>> Yes, it does appear that was the problem. The attach POC patch against >>> LXC fixes the hang. The kernel is working as intended. >>> >>> #regzbot invalid: userspace programming error >> >> Hmmm, not sure if I like this. So yes, this might be a bug in LXC, but >> afaics it's a bug that was exposed by kernel change in 5.17 (correct me >> if I'm wrong!). The problem thus still qualifies as a kernel regression >> that normally needs to be fixed, as can be seen my some of the quotes >> from Linus in this file: >> https://www.kernel.org/doc/html/latest/process/handling-regressions.html > > Sorry, but that's really BS in this particularly case. This could always > have triggered, it's the way multishot works. Will we count eg timing > changes as potential regressions, because an application relied on > something there? That does not make it ABI. > > In general I agree with Linus on this, a change in behavior breaking > something should be investigated and figured out (and reverted, if need > be). This is not that. Sorry, I have to deal with various subsystems and a lot of regressions reports. I can't know the details of each of issue and there are developers around that are not that familiar with all the practical implications of the "no regressions". That's why I was just trying to ensure that this is something safe to ignore. If you say it is, than I'm totally happy and now rest my case. :-D Ciao, Thorsten