From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB9D8C433FE for ; Mon, 16 May 2022 18:22:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344704AbiEPSWP (ORCPT ); Mon, 16 May 2022 14:22:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344665AbiEPSWM (ORCPT ); Mon, 16 May 2022 14:22:12 -0400 Received: from mail-il1-x12c.google.com (mail-il1-x12c.google.com [IPv6:2607:f8b0:4864:20::12c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BAF682BB00 for ; Mon, 16 May 2022 11:22:10 -0700 (PDT) Received: by mail-il1-x12c.google.com with SMTP id l15so11085656ilh.3 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=JuV+tNW70+Sg1FiaDx4UyXe4z/i7/cMQog9e8tDv++Q3LjZq9oDMFDJZDLIz3sd01O lsLfOI2CMRl7i2Ray5czMe/RgwcdD6617ZP5qfnMXEdtd0av3uiy9h2DTKHBzhJI0b3N GDczfUT3QbA6zfHjgowznKVtcGeWbUiKMPDV+0PNhcR+lsKCTTx/ngoFzpNO2ih8DVM6 EyHFtZAE2qydyBL3tNpIw8HMaE4Fz28+8Tnp08gt2Gq6QJpuVI41G8tZMgpPPSZmvc/1 +TqbrYv8MmJfqimw/YO3bNW43PhYlGH2FVK6VgkGB1JOMpdA5ZtMCDP4aRH5N5WPbYZj 0MbA== X-Gm-Message-State: AOAM532lavbinc8ypd936b51+XorBkqxXdf2sB8W7NblguSR0b6xk3tI dt/qG0KPw3Za9eYDt4X5yUOIbw== 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 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 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 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