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 65D1CC433F5 for ; Fri, 24 Dec 2021 10:38:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344118AbhLXKiK (ORCPT ); Fri, 24 Dec 2021 05:38:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343932AbhLXKiK (ORCPT ); Fri, 24 Dec 2021 05:38:10 -0500 Received: from mail-wr1-x42f.google.com (mail-wr1-x42f.google.com [IPv6:2a00:1450:4864:20::42f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C81EEC061401; Fri, 24 Dec 2021 02:38:09 -0800 (PST) Received: by mail-wr1-x42f.google.com with SMTP id i22so16680146wrb.13; Fri, 24 Dec 2021 02:38:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.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=XjBGi+dJXXQnmTq7rq+KjohVrDPP5Z8h7UOS9LTpl7A=; b=Rj37lDjhRFUc7q2M+C6fi9hbOPuyZjdMGbHyY4K6HHo3T1eJHJGMoM/400ZwXdh9sB ltN6Zd82Ah1EEaxr+ol7thpVVvDzlZKSDrTC4QgoT3mkjKRc5wAFPRVV5hPf/UjNqdYl I8D5Ou9/Ofl56PLVyO+s2wNMP+TLGZkvvGYPx6yDoiPM7iYCgbFhXHwUoB/73pjTSz8k pPZTQ4BuDb+if26Rp2Hb4ItZOQZH++3kuu8SxXIVnLD36SlAMyp/E3V94KBPYPBzgJr0 5oi5+oTPgs8ujfXKyZhDhTsAyPyx9C6GK8w1cYr+bedjnMAMVNj/8xLQOLUkPxRFmrik d6yQ== 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=XjBGi+dJXXQnmTq7rq+KjohVrDPP5Z8h7UOS9LTpl7A=; b=Zhzxpo8z6PSuun6bneeo+evkMMhf8RapTv4Vo0ZhjvGNqCWffIzYZVJZHvTZ/DlC6/ vpJZwJg6O22+G0wjYkXiwgUrgLw7fiICubG/TPiQBKiOSQn46iI/j+kiOgY0T/J3Z+xH TvPtDROcEHPzh2IFmHKqBFbV1Gb308fFbkgGN4CLFVd3Gfl3xPLlsJwXVkWjnE4gQ0+7 1ObmRFexBB8IMy0nKNpXttoRhZ9XFGvZM08JxnxcSJyFCMwjOmE+agqIT3fVSIUFRxE8 R9ewkmVCNZRaRSNhaoBEL0VJmjtSnU8UtBMsL6OtEXMzwx3W+dBxhAB8JAh0tDakmmFi Vvog== X-Gm-Message-State: AOAM531VwKj+YCX0Qp977lH5/Syndz9tH0DpXPsjwY9CdKvsX4hsa/TQ iEcoxCWHhE7+zTcuXT3jQrGOUajnMlM= X-Google-Smtp-Source: ABdhPJys90a3kGzt+UsOHuNN9q/es+YbAMysaOzL5WhNevcs2Vf/ooc2d4G0kjBwoGEKL3i9w4pl7Q== X-Received: by 2002:a5d:6049:: with SMTP id j9mr4166002wrt.332.1640342288320; Fri, 24 Dec 2021 02:38:08 -0800 (PST) Received: from [192.168.8.198] ([148.252.132.189]) by smtp.gmail.com with ESMTPSA id a1sm7598466wru.113.2021.12.24.02.38.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Dec 2021 02:38:07 -0800 (PST) Message-ID: <13250a8d-1a59-4b7b-92e4-1231d73cbdda@gmail.com> Date: Fri, 24 Dec 2021 10:37:31 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [RFC] coredump: Do not interrupt dump for TIF_NOTIFY_SIGNAL Content-Language: en-US To: Olivier Langlois , "Eric W. Biederman" , linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, Alexander Viro , Jens Axboe , Oleg Nesterov , Linus Torvalds References: <192c9697e379bf084636a8213108be6c3b948d0b.camel@trillion01.com> <9692dbb420eef43a9775f425cb8f6f33c9ba2db9.camel@trillion01.com> <87h7i694ij.fsf_-_@disp2133> <1b519092-2ebf-3800-306d-c354c24a9ad1@gmail.com> From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 12/24/21 01:34, Olivier Langlois wrote: > On Fri, 2021-10-22 at 15:13 +0100, Pavel Begunkov wrote: >> On 6/9/21 21:17, Eric W. Biederman wrote: >> In short, a task creates an io_uring worker thread, then the worker >> submits a task_work item to the creator task and won't die until >> the item is executed/cancelled. And I found that the creator task is >> sleeping in do_coredump() -> wait_for_completion() >> [...] >> A hack executing tws there helps (see diff below). >> Any chance anyone knows what this is and how to fix it? >> [...] > Pavel, > > I cannot comment on the merit of the proposed hack but my proposed > patch to fix the coredump truncation issue when a process using > io_uring core dumps that I submitted back in August is still > unreviewed! That's unfortunate. Not like I can help in any case, but I assumed it was dealt with by commit 06af8679449d4ed282df13191fc52d5ba28ec536 Author: Eric W. Biederman Date: Thu Jun 10 15:11:11 2021 -0500 coredump: Limit what can interrupt coredumps Olivier Langlois has been struggling with coredumps being incompletely written in processes using io_uring. ... > https://lore.kernel.org/lkml/1625bc89782bf83d9d8c7c63e8ffcb651ccb15fa.1629655338.git.olivier@trillion01.com/ > > I have been using it since then I must have generated many dozens of > perfect core dump files with it and I have not seen a single truncated > core dump files like I used to have prior to the patch. > > I am bringing back my patch to your attention because one nice side > effect of it is that it would have avoided totally the problem that you > have encountered in coredump_wait() since it does cancel io_uring > resources before calling coredump_wait()! FWIW, I worked it around in io_uring back then by breaking the dependency. -- Pavel Begunkov