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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20136C10F00 for ; Sat, 7 Mar 2020 15:36:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DBA2420675 for ; Sat, 7 Mar 2020 15:36:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="o6S4yzpE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726246AbgCGPgd (ORCPT ); Sat, 7 Mar 2020 10:36:33 -0500 Received: from mail-pg1-f194.google.com ([209.85.215.194]:37282 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726074AbgCGPgd (ORCPT ); Sat, 7 Mar 2020 10:36:33 -0500 Received: by mail-pg1-f194.google.com with SMTP id z12so2561868pgl.4 for ; Sat, 07 Mar 2020 07:36:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=X8Q0iQvt9yySsKBxTObcLgqNokyvnZ8EgfUe1/v9Oag=; b=o6S4yzpEbBoXuEbGBPbuI2aVMha7Hq4/PaqQ+0ISNq4VryGl2gneRQo1uyI5G8y+sM MPep6y8foCYeMdjVWvSmCeZEwaoTKAss0DymSfmCUSw5mmZy8dX5EYd0dbPtFQauatHF Tq4KA4FK5iTzaF1F4yo8NafTb/L4UDtzPK83LM7ZmbnT7zKe0gGyKf3jHiMrOQMIAj1Q MfomBNKKxgx1Conwk1sof1Cok2NUDN5FKrEfTepJgbx5JaYYRiaLnCHu9LKwQNVYkhgJ FMMS37a1CReTT0N3q6GxYYXPvCZBvu2NdjFjkSSS92EVfXv6oWmHy5AHH69Fg0i8xEGb d8dQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=X8Q0iQvt9yySsKBxTObcLgqNokyvnZ8EgfUe1/v9Oag=; b=Ci9jjI+9Hkho8ma7KvFF1zmXEqnTtzG4dleFhZmn7FhxLh+A0tmsdhrq+jhL5NHMYd kYeJREU06o7+Rb9UmKULSzXWAzYclkIROb63ME6IN4oa9dTIrY6Fo5ywZ4Noy993/lAK mYi7DdbXpchLU+lsa/8cbSYgfaGWivnbG3EL/a3M7YTPihU+bsUp7M4gGwa8R0EeSwbH Yxznapl+Da3L9etQOYbXPmpDQANEWTUewG6+pF7dwXxji6tGWrKYWPoPNr0LPM5uhRLU rLfVj0ff0IWFjKeSfZ626rEg/Wl2VyK/l1xpIUpYz7w8mIPAsQALSRPG++ZW6NskXAq1 K/tw== X-Gm-Message-State: ANhLgQ3enOrKxUWD0sVqH3CrsRV4uORlu2yRPFNkhzFB0JBE5EPH4km0 dErxCVQAMLhJtg/UhuUy9gQFwkFZ5/w= X-Google-Smtp-Source: ADFU+vv/CpDAMDYJcxi9ndwAxm1jhXPFLdwR0Dr7LdLSFsjt7ExIeOBElk+ZsZWGCaJjSUGKsulRyA== X-Received: by 2002:aa7:8502:: with SMTP id v2mr8739393pfn.232.1583595392111; Sat, 07 Mar 2020 07:36:32 -0800 (PST) Received: from [192.168.1.188] ([66.219.217.145]) by smtp.gmail.com with ESMTPSA id c18sm38291906pgw.17.2020.03.07.07.36.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Mar 2020 07:36:31 -0800 (PST) Subject: Re: [PATCH 1/1] io_uring: fix lockup with timeouts To: Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <54e141c75da11f55f607d53c54943b9fee5bbd70.1583532280.git.asml.silence@gmail.com> From: Jens Axboe Message-ID: <4a96385c-52ea-cba8-455d-6fd3042bd49e@kernel.dk> Date: Sat, 7 Mar 2020 08:36:27 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <54e141c75da11f55f607d53c54943b9fee5bbd70.1583532280.git.asml.silence@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/6/20 3:15 PM, Pavel Begunkov wrote: > There is a recipe to deadlock the kernel: submit a timeout sqe with a > linked_timeout (e.g. test_single_link_timeout_ception() from liburing), > and SIGKILL the process. > > Then, io_kill_timeouts() takes @ctx->completion_lock, but the timeout > isn't flagged with REQ_F_COMP_LOCKED, and will try to double grab it > during io_put_free() to cancel the linked timeout. Probably, the same > can happen with another io_kill_timeout() call site, that is > io_commit_cqring(). Thanks, looks good, applied. -- Jens Axboe