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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT 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 3A921C433F5 for ; Sat, 11 Sep 2021 19:41:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1BA2260F5D for ; Sat, 11 Sep 2021 19:41:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233567AbhIKTnA (ORCPT ); Sat, 11 Sep 2021 15:43:00 -0400 Received: from out30-42.freemail.mail.aliyun.com ([115.124.30.42]:36420 "EHLO out30-42.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232353AbhIKTnA (ORCPT ); Sat, 11 Sep 2021 15:43:00 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;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_---0Uo.lhDo_1631389252; Received: from e18g09479.et15sqa.tbsite.net(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0Uo.lhDo_1631389252) by smtp.aliyun-inc.com(127.0.0.1); Sun, 12 Sep 2021 03:40:59 +0800 From: Hao Xu To: Jens Axboe Cc: io-uring@vger.kernel.org, Pavel Begunkov , Joseph Qi Subject: [PATCH 4/4] io-wq: fix potential race of acct->nr_workers Date: Sun, 12 Sep 2021 03:40:52 +0800 Message-Id: <20210911194052.28063-5-haoxu@linux.alibaba.com> X-Mailer: git-send-email 2.24.4 In-Reply-To: <20210911194052.28063-1-haoxu@linux.alibaba.com> References: <20210911194052.28063-1-haoxu@linux.alibaba.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Given max_worker is 1, and we currently have 1 running and it is exiting. There may be race like: io_wqe_enqueue worker1 no work there and timeout unlock(wqe->lock) ->insert work -->io_worker_exit lock(wqe->lock) ->if(!nr_workers) //it's still 1 unlock(wqe->lock) goto run_cancel lock(wqe->lock) nr_workers-- ->dec_running ->worker creation fails unlock(wqe->lock) We enqueued one work but there is no workers, causes hung. Signed-off-by: Hao Xu --- fs/io-wq.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/io-wq.c b/fs/io-wq.c index 75e79571bdfd..b84dc8df6c68 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -176,7 +176,6 @@ static void io_worker_ref_put(struct io_wq *wq) static void io_worker_exit(struct io_worker *worker) { struct io_wqe *wqe = worker->wqe; - struct io_wqe_acct *acct = io_wqe_get_acct(worker); if (refcount_dec_and_test(&worker->ref)) complete(&worker->ref_done); @@ -186,7 +185,6 @@ static void io_worker_exit(struct io_worker *worker) if (worker->flags & IO_WORKER_F_FREE) hlist_nulls_del_rcu(&worker->nulls_node); list_del_rcu(&worker->all_list); - acct->nr_workers--; preempt_disable(); refcount_set(&worker->ref, 1); io_wqe_dec_running(worker); @@ -571,6 +569,7 @@ static int io_wqe_worker(void *data) } /* timed out, exit unless we're the last worker */ if (last_timeout && acct->nr_workers > 1) { + acct->nr_workers--; raw_spin_unlock(&wqe->lock); __set_current_state(TASK_RUNNING); break; -- 2.24.4