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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 562A7C35671 for ; Sat, 22 Feb 2020 06:46:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 252E42071E for ; Sat, 22 Feb 2020 06:46:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726917AbgBVGqS (ORCPT ); Sat, 22 Feb 2020 01:46:18 -0500 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:58507 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726832AbgBVGqS (ORCPT ); Sat, 22 Feb 2020 01:46:18 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R901e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=xiaoguang.wang@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0TqaAKPa_1582353966; Received: from localhost(mailfrom:xiaoguang.wang@linux.alibaba.com fp:SMTPD_---0TqaAKPa_1582353966) by smtp.aliyun-inc.com(127.0.0.1); Sat, 22 Feb 2020 14:46:12 +0800 From: Xiaoguang Wang To: io-uring@vger.kernel.org Cc: axboe@kernel.dk, joseph.qi@linux.alibaba.com, Xiaoguang Wang Subject: [PATCH] io_uring: fix __io_iopoll_check deadlock in io_sq_thread Date: Sat, 22 Feb 2020 14:46:05 +0800 Message-Id: <20200222064605.2571-1-xiaoguang.wang@linux.alibaba.com> X-Mailer: git-send-email 2.17.2 Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Since commit a3a0e43fd770 ("io_uring: don't enter poll loop if we have CQEs pending"), if we already events pending, we won't enter poll loop. In case SETUP_IOPOLL and SETUP_SQPOLL are both enabled, if app has been terminated and don't reap pengding events which are already in cq ring, and there are some reqs in poll_list, io_sq_thread will enter __io_iopoll_check(), and find pending events, then return, this loop will never have a chance to exit. I have seem this issue in fio stress tests, to fix this issue, let io_sq_thread call io_iopoll_getevents() with argument 'min' being zero, and remove __io_iopoll_check(). Fixes: a3a0e43fd770 ("io_uring: don't enter poll loop if we have CQEs pending") Signed-off-by: Xiaoguang Wang --- fs/io_uring.c | 27 +++++++++------------------ 1 file changed, 9 insertions(+), 18 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 77f22c3da30f..c69870b0c0ca 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1635,11 +1635,17 @@ static void io_iopoll_reap_events(struct io_ring_ctx *ctx) mutex_unlock(&ctx->uring_lock); } -static int __io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, - long min) +static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, + long min) { int iters = 0, ret = 0; + /* + * We disallow the app entering submit/complete with polling, but we + * still need to lock the ring to prevent racing with polled issue + * that got punted to a workqueue. + */ + mutex_lock(&ctx->uring_lock); do { int tmin = 0; @@ -1675,21 +1681,6 @@ static int __io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, ret = 0; } while (min && !*nr_events && !need_resched()); - return ret; -} - -static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, - long min) -{ - int ret; - - /* - * We disallow the app entering submit/complete with polling, but we - * still need to lock the ring to prevent racing with polled issue - * that got punted to a workqueue. - */ - mutex_lock(&ctx->uring_lock); - ret = __io_iopoll_check(ctx, nr_events, min); mutex_unlock(&ctx->uring_lock); return ret; } @@ -5039,7 +5030,7 @@ static int io_sq_thread(void *data) */ mutex_lock(&ctx->uring_lock); if (!list_empty(&ctx->poll_list)) - __io_iopoll_check(ctx, &nr_events, 0); + io_iopoll_getevents(ctx, &nr_events, 0); else inflight = 0; mutex_unlock(&ctx->uring_lock); -- 2.17.2