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=-15.7 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 54284C4320E for ; Mon, 26 Jul 2021 14:40:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 385C560EB2 for ; Mon, 26 Jul 2021 14:40:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234733AbhGZN7a (ORCPT ); Mon, 26 Jul 2021 09:59:30 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:50348 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233206AbhGZN7Z (ORCPT ); Mon, 26 Jul 2021 09:59:25 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01424;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0Uh4Jw3J_1627310392; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0Uh4Jw3J_1627310392) by smtp.aliyun-inc.com(127.0.0.1); Mon, 26 Jul 2021 22:39:52 +0800 Subject: Re: [PATCH io_uring-5.14 v2] io_uring: remove double poll wait entry for pure poll To: Pavel Begunkov , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <20210723092227.137526-1-haoxu@linux.alibaba.com> <824dcbe0-34da-a075-12eb-ce7529f3e3f7@linux.alibaba.com> <28ce8b3d-e9d2-2fed-e73c-fb09913eea78@gmail.com> From: Hao Xu Message-ID: Date: Mon, 26 Jul 2021 22:39:51 +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: <28ce8b3d-e9d2-2fed-e73c-fb09913eea78@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 2021/7/26 下午8:40, Pavel Begunkov 写道: > On 7/24/21 5:48 AM, Hao Xu wrote: >> 在 2021/7/23 下午10:31, Pavel Begunkov 写道: >>> On 7/23/21 10:22 AM, Hao Xu wrote: >>>> For pure poll requests, we should remove the double poll wait entry. >>>> And io_poll_remove_double() is good enough for it compared with >>>> io_poll_remove_waitqs(). >>> >>> 5.14 in the subject hints me that it's a fix. Is it? >>> Can you add what it fixes or expand on why it's better? >> Hi Pavel, I found that for poll_add() requests, it doesn't remove the >> double poll wait entry when it's done, neither after vfs_poll() or in >> the poll completion handler. The patch is mainly to fix it. > > Ok, sounds good. Please resend with updated description, and > let's add some tags. > > Fixes: 88e41cf928a6 ("io_uring: add multishot mode for IORING_OP_POLL_ADD") > Cc: stable@vger.kernel.org # 5.13+ > > Also, I'd prefer the commit title to make more clear that it's a > fix. E.g. "io_uring: fix poll requests leaking second poll entries". > > Btw, seems it should fix hangs in ./poll-mshot-update Sure，I'll send v3 soon, sorry for my unprofessionalism.. > > >>> >>>> Signed-off-by: Hao Xu >>>> --- >>>> >>>> v1-->v2 >>>>    delete redundant io_poll_remove_double() >>>> >>>>   fs/io_uring.c | 5 ++--- >>>>   1 file changed, 2 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>>> index f2fe4eca150b..c5fe8b9e26b4 100644 >>>> --- a/fs/io_uring.c >>>> +++ b/fs/io_uring.c >>>> @@ -4903,7 +4903,6 @@ 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)) { >>>> -        io_poll_remove_waitqs(req); >> Currently I only see it does that with io_poll_remove_waitqs() when >> cqring overflow and then ocqe allocation failed. Using >> io_poll_remove_waitqs() here is not very suitable since (1) it calls >> __io_poll_remove_one() which set poll->cancelled = true, why do we set >> poll->cancelled and poll->done to true at the same time though I think >> that doesn't cause any problem. (2) it does >> list_del_init(&poll->wait.entry) and hash_del(&req->hash_node) which >> has been already done. >> Correct me if I'm wrong since I may misunderstand the code. >> >> Regards, >> Hao >>>>           req->poll.done = true; >>>>           flags = 0; >>>>       } >>>> @@ -4926,6 +4925,7 @@ static void io_poll_task_func(struct io_kiocb *req) >>>>             done = io_poll_complete(req, req->result); >>>>           if (done) { >>>> +            io_poll_remove_double(req); >>>>               hash_del(&req->hash_node); >>>>           } else { >>>>               req->result = 0; >>>> @@ -5113,7 +5113,7 @@ static __poll_t __io_arm_poll_handler(struct io_kiocb *req, >>>>           ipt->error = -EINVAL; >>>>         spin_lock_irq(&ctx->completion_lock); >>>> -    if (ipt->error) >>>> +    if (ipt->error || (mask && (poll->events & EPOLLONESHOT))) >>>>           io_poll_remove_double(req); >>>>       if (likely(poll->head)) { >>>>           spin_lock(&poll->head->lock); >>>> @@ -5185,7 +5185,6 @@ static int io_arm_poll_handler(struct io_kiocb *req) >>>>       ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask, >>>>                       io_async_wake); >>>>       if (ret || ipt.error) { >>>> -        io_poll_remove_double(req); >>>>           spin_unlock_irq(&ctx->completion_lock); >>>>           if (ret) >>>>               return IO_APOLL_READY; >>>> >>> >> >