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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 autolearn=ham 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 96274C4338F for ; Mon, 9 Aug 2021 16:12:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E68360EB9 for ; Mon, 9 Aug 2021 16:12:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229488AbhHIQM7 (ORCPT ); Mon, 9 Aug 2021 12:12:59 -0400 Received: from out30-57.freemail.mail.aliyun.com ([115.124.30.57]:51074 "EHLO out30-57.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229456AbhHIQM6 (ORCPT ); Mon, 9 Aug 2021 12:12:58 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R111e4;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_---0UiWKlej_1628525555; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UiWKlej_1628525555) by smtp.aliyun-inc.com(127.0.0.1); Tue, 10 Aug 2021 00:12:36 +0800 Subject: Re: [PATCH 1/2] io-wq: fix bug of creating io-wokers unconditionally To: Jens Axboe Cc: io-uring@vger.kernel.org, Pavel Begunkov , Joseph Qi References: <20210808135434.68667-1-haoxu@linux.alibaba.com> <20210808135434.68667-2-haoxu@linux.alibaba.com> <36fa131c-0a86-81de-2a93-265af921c38a@linux.alibaba.com> <2df89a6c-edf4-8b1d-85d2-720ee25d816c@kernel.dk> From: Hao Xu Message-ID: <0760b085-0d10-eea2-eedf-76d4047a7084@linux.alibaba.com> Date: Tue, 10 Aug 2021 00:12:35 +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: <2df89a6c-edf4-8b1d-85d2-720ee25d816c@kernel.dk> 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 2021/8/9 下午10:18, Jens Axboe 写道: > On 8/9/21 8:08 AM, Hao Xu wrote: >> 在 2021/8/9 下午10:01, Jens Axboe 写道: >>> On 8/8/21 7:54 AM, Hao Xu wrote: >>>> The former patch to add check between nr_workers and max_workers has a >>>> bug, which will cause unconditionally creating io-workers. That's >>>> because the result of the check doesn't affect the call of >>>> create_io_worker(), fix it by bringing in a boolean value for it. >>>> >>>> Fixes: 21698274da5b ("io-wq: fix lack of acct->nr_workers < acct->max_workers judgement") >>>> Signed-off-by: Hao Xu >>>> --- >>>> fs/io-wq.c | 19 ++++++++++++++----- >>>> 1 file changed, 14 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/fs/io-wq.c b/fs/io-wq.c >>>> index 12fc19353bb0..5536b2a008d1 100644 >>>> --- a/fs/io-wq.c >>>> +++ b/fs/io-wq.c >>>> @@ -252,14 +252,15 @@ static void io_wqe_wake_worker(struct io_wqe *wqe, struct io_wqe_acct *acct) >>>> >>>> raw_spin_lock_irq(&wqe->lock); >>>> if (acct->nr_workers < acct->max_workers) { >>>> - atomic_inc(&acct->nr_running); >>>> - atomic_inc(&wqe->wq->worker_refs); >>>> acct->nr_workers++; >>>> do_create = true; >>>> } >>>> raw_spin_unlock_irq(&wqe->lock); >>>> - if (do_create) >>>> + if (do_create) { >>>> + atomic_inc(&acct->nr_running); >>>> + atomic_inc(&wqe->wq->worker_refs); >>>> create_io_worker(wqe->wq, wqe, acct->index); >>>> + } >>>> } >>> >>> I don't get this hunk - we already know we're creating a worker, what's the >>> point in moving the incs? >>> >> Actually not much difference, I think we don't need to protect >> nr_running and worker_refs by wqe->lock, so narrow the range of >> raw_spin_lock_irq - raw_spin_unlock_irq > > Agree, we don't need it, but it's not a fix as such. I'd rather defer that > one to a separate cleanup for the next release. I'll send it later. >