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=-5.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,UNPARSEABLE_RELAY,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 04C8CC4320A for ; Thu, 5 Aug 2021 17:37:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DF00E60F42 for ; Thu, 5 Aug 2021 17:37:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239635AbhHERhT (ORCPT ); Thu, 5 Aug 2021 13:37:19 -0400 Received: from out30-43.freemail.mail.aliyun.com ([115.124.30.43]:55670 "EHLO out30-43.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239498AbhHERhT (ORCPT ); Thu, 5 Aug 2021 13:37:19 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R851e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0Ui3wcfC_1628185022; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0Ui3wcfC_1628185022) by smtp.aliyun-inc.com(127.0.0.1); Fri, 06 Aug 2021 01:37:03 +0800 Subject: Re: [PATCH 1/3] io-wq: clean code of task state setting To: Jens Axboe Cc: io-uring@vger.kernel.org, Pavel Begunkov , Joseph Qi References: <20210805100538.127891-1-haoxu@linux.alibaba.com> <20210805100538.127891-2-haoxu@linux.alibaba.com> From: Hao Xu Message-ID: <36502b3d-bc15-53ea-6dda-789d92891873@linux.alibaba.com> Date: Fri, 6 Aug 2021 01:37:02 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 在 2021/8/5 下午10:23, Jens Axboe 写道: > On 8/5/21 4:05 AM, Hao Xu wrote: >> We don't need to set task state to TASK_INTERRUPTIBLE at the beginning >> of while() in io_wqe_worker(), which causes state resetting to >> TASK_RUNNING in other place. Move it to above schedule_timeout() and >> remove redundant task state settings. > > Not sure that is safe - the reason why the state is manipulated is to > guard from races where we do: > > A B > if (!work_available) > Work inserted > schedule(); > You are right, the patch does bring in races. Though B will then create an io-worker in that race condition, but that causes delay. Thanks Jens! > As long as setting the task runnable is part of the work being inserted, > then the above race is fine, as the schedule() turns into a no-op. >