From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-il1-f178.google.com (mail-il1-f178.google.com [209.85.166.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 185CF136B for ; Mon, 16 May 2022 18:22:10 +0000 (UTC) Received: by mail-il1-f178.google.com with SMTP id f9so1348936ils.7 for ; Mon, 16 May 2022 11:22:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=fi2MKK4RDnx6306yvIj3WqOA9+3aIysOXF+Rc+RJb4Y=; b=ZoeYipp1srp2zffS6xSdw3auO/PUsqr9RF6aFDmflEnta+cN9h3QQekvih8nXjtLzx denBn/B1SfVOfEOGy2MF80u8pStM64jj/Q2zsXN+0DFTuPMdMb/kksBYYo5pDGgM6Yt+ fQrwdiKbkUsAUy4DQF5f5RGSkh1OWCthVya+Z8j8X4Bt7hdKTcT7PU0zWixT1OJgcek/ srWG6vzSTBHbi3Je60NibFukSh1mtN5de+TrSHi34uZCkJcKJYnVvJECuvwSJucjknSV D6xDfmCN71FptFkL1m+92AWgmDlknvKgLHAtCLgI4FND7h1wZvCv4Q/JcGlY1n3RjpjN 00JA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=fi2MKK4RDnx6306yvIj3WqOA9+3aIysOXF+Rc+RJb4Y=; b=lFat+gS8skhblGC4cy6VAmdoTFJJY9ZgbMjliymEMcWMBSCJu02gjMovxOquJFUaYw AHGmaLwUaQzzccCi2u0ucKXAM18L+e3jezY+DHULewlsV9Z9MOsfsxUOpyXonnm30r9q bcrtQplB433706FIYeGsRYO3hOv7UP8KrjB8WRiKetF6Izoh+IDUNcvgX8Xz3uq0qyYd zzrtxSBbKdbTcc+1OdO0Vt4St3a7cJDqDPdCHGzO5Ohhzv46V4LdOvb6oWaEOCXFSgV/ 6fcypGobpIpS68WaONZ9gTG8eu+I1FFSRnJzROldcTq9RC6dlOKZkAAV5ciwCSnxXh50 M7uQ== X-Gm-Message-State: AOAM533siqlGbv6Mby5jMhzK39ycezqhE3AaReL1htKcDH6tLwKDVlnY Ga6dU2e9HwiLDbcq7ozWsw9Sew== X-Google-Smtp-Source: ABdhPJwu+uko3W1bDT97qFkqQc86IbLg5bTX+TVEm+Bg5/uK411UrX/M11NqCONlxy6V9sq7qROTPA== X-Received: by 2002:a05:6e02:1c27:b0:2cf:6de9:5342 with SMTP id m7-20020a056e021c2700b002cf6de95342mr9584457ilh.176.1652725329933; Mon, 16 May 2022 11:22:09 -0700 (PDT) Received: from [192.168.1.172] ([207.135.234.126]) by smtp.gmail.com with ESMTPSA id l44-20020a026a2c000000b0032b3a7817d3sm2964148jac.151.2022.05.16.11.22.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 May 2022 11:22:08 -0700 (PDT) Message-ID: Date: Mon, 16 May 2022 12:22:07 -0600 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 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: Thorsten Leemhuis , 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: Jens Axboe In-Reply-To: <469e5a9b-c7e0-6365-c353-d831ff1c5071@leemhuis.info> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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. -- Jens Axboe I