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=-16.9 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 0E933C433F5 for ; Wed, 15 Sep 2021 10:49:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E84BE61279 for ; Wed, 15 Sep 2021 10:49:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232290AbhIOKvH (ORCPT ); Wed, 15 Sep 2021 06:51:07 -0400 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:51357 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232286AbhIOKvG (ORCPT ); Wed, 15 Sep 2021 06:51:06 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0UoTgsKt_1631702985; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UoTgsKt_1631702985) by smtp.aliyun-inc.com(127.0.0.1); Wed, 15 Sep 2021 18:49:46 +0800 Subject: Re: [PATCH 2/2] io_uring: fix race between poll completion and cancel_hash insertion To: Pavel Begunkov , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <20210912162345.51651-1-haoxu@linux.alibaba.com> <20210912162345.51651-3-haoxu@linux.alibaba.com> <8f4826c9-2234-bea2-cd1c-88a4a8b8d914@gmail.com> From: Hao Xu Message-ID: <94a47e79-fbe7-3084-1b55-3f1bd06ef8ee@linux.alibaba.com> Date: Wed, 15 Sep 2021 18:49:45 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <8f4826c9-2234-bea2-cd1c-88a4a8b8d914@gmail.com> 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 2021/9/15 下午5:50, Pavel Begunkov 写道: > On 9/12/21 5:23 PM, Hao Xu wrote: >> If poll arming and poll completion runs parallelly, there maybe races. >> For instance, run io_poll_add in iowq and io_poll_task_func in original >> context, then: >> iowq original context >> io_poll_add >> vfs_poll >> (interruption happens >> tw queued to original >> context) io_poll_task_func >> generate cqe >> del from cancel_hash[] >> if !poll.done >> insert to cancel_hash[] >> >> The entry left in cancel_hash[], similar case for fast poll. >> Fix it by set poll.done = true when del from cancel_hash[]. > > Sounds like a valid concern. And the code looks good, but one > of two patches crashed the kernel somewhere in io_read(). > > ./232c93d07b74-test I'll run it too, didn't meet that when I did the test. > > will be retesting > > >> Signed-off-by: Hao Xu >> --- >> >> Didn't find the exact commit to add Fixes: for.. > > That's ok. Maybe you can find which kernel versions are > affected? So we can add stable and specify where it should > be backported? E.g. Sure, will do that. > > Cc: stable@vger.kernel.org # 5.12+ > > >> fs/io_uring.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index c16f6be3d46b..988679e5063f 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -5118,10 +5118,8 @@ static bool __io_poll_complete(struct io_kiocb *req, __poll_t mask) >> } >> if (req->poll.events & EPOLLONESHOT) >> flags = 0; >> - if (!io_cqring_fill_event(ctx, req->user_data, error, flags)) { >> - req->poll.done = true; >> + if (!io_cqring_fill_event(ctx, req->user_data, error, flags)) >> flags = 0; >> - } >> if (flags & IORING_CQE_F_MORE) >> ctx->cq_extra++; >> >> @@ -5152,6 +5150,7 @@ static void io_poll_task_func(struct io_kiocb *req, bool *locked) >> if (done) { >> io_poll_remove_double(req); >> hash_del(&req->hash_node); >> + req->poll.done = true; >> } else { >> req->result = 0; >> add_wait_queue(req->poll.head, &req->poll.wait); >> @@ -5289,6 +5288,7 @@ static void io_async_task_func(struct io_kiocb *req, bool *locked) >> >> hash_del(&req->hash_node); >> io_poll_remove_double(req); >> + req->poll.done = true; >> spin_unlock(&ctx->completion_lock); >> >> if (!READ_ONCE(apoll->poll.canceled)) >> >