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 87EC6C433F5 for ; Mon, 2 May 2022 18:49:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1386963AbiEBSxR (ORCPT ); Mon, 2 May 2022 14:53:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353640AbiEBSxP (ORCPT ); Mon, 2 May 2022 14:53:15 -0400 Received: from wout3-smtp.messagingengine.com (wout3-smtp.messagingengine.com [64.147.123.19]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0306BBE05; Mon, 2 May 2022 11:49:46 -0700 (PDT) Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailout.west.internal (Postfix) with ESMTP id EB1BA32009D3; Mon, 2 May 2022 14:49:44 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute4.internal (MEProxy); Mon, 02 May 2022 14:49:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=living180.net; h=cc:cc:content-transfer-encoding:content-type:date:date:from :from:in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:sender:subject:subject:to:to; s=fm2; t=1651517384; x= 1651603784; bh=TA2UFVaia1h61cNM8zIfNtZYBdMcoajUo47LJiOq4l8=; b=M pKdoxVMCy/xlYDX9nOreTIZsbrAGrRpYtYShYJbdUNzoAnfxm9HhU9eJmTViQN8l 1EXpJFG6aVF8RsolrNyG92LeNXeK8JaxSf41Y3YBheTPO8+wxOa/awTUjllmfU0v w7740700pjdTLAzNGA2N1wsHRKpwb9EIfiTT7hCDiuAJOn7YpTZZ4C18QQs/+dEz Ox+W65jFkhT/FG8Q/p+bqtP28W13HUFKDz3r42dK59I0pgv/zSXVzm1av9zmuH2W oD5joAvPeE/6FSaYlHOJmOh/F+SE7C73SU0SDrJjDfxVl0/JMazMOuOv3/9/5Tu/ V4dD1fp8eUey195upYP6w== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:date:date:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm1; t=1651517384; x=1651603784; bh=TA2UFVaia1h61 cNM8zIfNtZYBdMcoajUo47LJiOq4l8=; b=oHGf6c3x40EYjKNZ8oAWzsNvdi1uV ziwk9tq3PvX7X2GdMje2Wj6tcTDPQ0XLukxxjkYQy1Gtfk22Mb0N3NB6IpiAJcuR qHtK1nNVdNDeXBxoYA5uBW3z9a6UJt3DWG2solwDBt6f8eVmohePqFWP22/gSL7f 6SJLHstXX4v859JFiSNuxITpJka/XpdH5mlD2p1Cu87QdZqQqoVFbCflxtCsYMnT wUP5IS2ZDJYH4GMETW+nXkJ+DaDEHGAwYrCMf9HrUvp9iMl5Fl/qTSJhiuVX0Idg p+6oT4/Ljx8Szioc40jkx6XoSRk27JPxrgh604sCLIk97Rr9vdQXoPXsA== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvfedrvdehgdduvdelucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepkfffgggfuffvvehfhfgjtgfgsehtkeertddtfeejnecuhfhrohhmpeffrghn ihgvlhcujfgrrhguihhnghcuoeguhhgrrhguihhngheslhhivhhinhhgudektddrnhgvth eqnecuggftrfgrthhtvghrnhepleekheegfeeffedvhfffvdettedtjeetuedtgfdvudei feelfeeigeduhfejhfejnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrg hilhhfrhhomhepughhrghrughinhhgsehlihhvihhnghdukedtrdhnvght X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 2 May 2022 14:49:42 -0400 (EDT) Message-ID: Date: Mon, 2 May 2022 21:49:40 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; 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: Pavel Begunkov , Jens Axboe 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> <371c01dd-258c-e428-7428-ff390b664752@kernel.dk> <2436d42c-85ca-d060-6508-350c769804f1@gmail.com> From: Daniel Harding In-Reply-To: <2436d42c-85ca-d060-6508-350c769804f1@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/2/22 20:40, Pavel Begunkov wrote: > 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 OK, sorry it wasn't something simple. > # 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. It's late in my timezone, but I'll try to work on getting those traces tomorrow. -- Regards, Daniel Harding