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 492F5C433EF for ; Wed, 15 Sep 2021 10:48:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2DDC06127A for ; Wed, 15 Sep 2021 10:48:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232365AbhIOKtl (ORCPT ); Wed, 15 Sep 2021 06:49:41 -0400 Received: from out30-45.freemail.mail.aliyun.com ([115.124.30.45]:39090 "EHLO out30-45.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232290AbhIOKtk (ORCPT ); Wed, 15 Sep 2021 06:49:40 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R391e4;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_---0UoTgs50_1631702899; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UoTgs50_1631702899) by smtp.aliyun-inc.com(127.0.0.1); Wed, 15 Sep 2021 18:48:20 +0800 Subject: Re: [PATCH 1/2] io_uring: fix tw list mess-up by adding tw while it's already in tw list To: Pavel Begunkov , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <20210912162345.51651-1-haoxu@linux.alibaba.com> <20210912162345.51651-2-haoxu@linux.alibaba.com> <6b9d818b-468e-e409-8dc1-9d4bd586635e@gmail.com> From: Hao Xu Message-ID: <665861ee-7688-73ca-e553-177df4159cff@linux.alibaba.com> Date: Wed, 15 Sep 2021 18:48:19 +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: <6b9d818b-468e-e409-8dc1-9d4bd586635e@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5:44, Pavel Begunkov 写道: > On 9/12/21 5:23 PM, Hao Xu wrote: >> For multishot mode, there may be cases like: >> io_poll_task_func() >> -> add_wait_queue() >> async_wake() >> ->io_req_task_work_add() >> this one mess up the running task_work list >> since req->io_task_work.node is in use. >> >> similar situation for req->io_task_work.fallback_node. >> Fix it by set node->next = NULL before we run the tw, so that when we >> add req back to the wait queue in middle of tw running, we can safely >> re-add it to the tw list. > > It may get screwed before we get to "node->next = NULL;", > > -> async_wake() > -> io_req_task_work_add() > -> async_wake() > -> io_req_task_work_add() > tctx_task_work() True, this may happen if there is second poll wait entry. This pacth is for single wait entry only.. I'm thinking about the second poll entry issue, would be in a separate patch. > > >> Fixes: 7cbf1722d5fc ("io_uring: provide FIFO ordering for task_work") >> Signed-off-by: Hao Xu >> --- >> >> fs/io_uring.c | 11 ++++++++--- >> 1 file changed, 8 insertions(+), 3 deletions(-) >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index 30d959416eba..c16f6be3d46b 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -1216,13 +1216,17 @@ static void io_fallback_req_func(struct work_struct *work) >> struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx, >> fallback_work.work); >> struct llist_node *node = llist_del_all(&ctx->fallback_llist); >> - struct io_kiocb *req, *tmp; >> + struct io_kiocb *req; >> bool locked = false; >> >> percpu_ref_get(&ctx->refs); >> - llist_for_each_entry_safe(req, tmp, node, io_task_work.fallback_node) >> + req = llist_entry(node, struct io_kiocb, io_task_work.fallback_node); >> + while (member_address_is_nonnull(req, io_task_work.fallback_node)) { >> + node = req->io_task_work.fallback_node.next; >> + req->io_task_work.fallback_node.next = NULL; >> req->io_task_work.func(req, &locked); >> - >> + req = llist_entry(node, struct io_kiocb, io_task_work.fallback_node); >> + } >> if (locked) { >> if (ctx->submit_state.compl_nr) >> io_submit_flush_completions(ctx); >> @@ -2126,6 +2130,7 @@ static void tctx_task_work(struct callback_head *cb) >> locked = mutex_trylock(&ctx->uring_lock); >> percpu_ref_get(&ctx->refs); >> } >> + node->next = NULL; >> req->io_task_work.func(req, &locked); >> node = next; >> } while (node); >> >