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=-9.7 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 DBD9BC433E0 for ; Sat, 6 Jun 2020 15:13:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C22CF207BC for ; Sat, 6 Jun 2020 15:13:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726089AbgFFPNJ (ORCPT ); Sat, 6 Jun 2020 11:13:09 -0400 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:54640 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728614AbgFFPNH (ORCPT ); Sat, 6 Jun 2020 11:13:07 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=xiaoguang.wang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0U-kT4Fu_1591456374; Received: from localhost(mailfrom:xiaoguang.wang@linux.alibaba.com fp:SMTPD_---0U-kT4Fu_1591456374) by smtp.aliyun-inc.com(127.0.0.1); Sat, 06 Jun 2020 23:13:01 +0800 From: Xiaoguang Wang To: io-uring@vger.kernel.org Cc: axboe@kernel.dk, asml.silence@gmail.com, joseph.qi@linux.alibaba.com, Xiaoguang Wang Subject: [PATCH] io_uring: execute task_work_run() before dropping mm Date: Sat, 6 Jun 2020 23:12:48 +0800 Message-Id: <20200606151248.17663-1-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 While testing io_uring in our internal kernel, note it's not upstream kernel, we see below panic: [ 872.498723] x29: ffff00002d553cf0 x28: 0000000000000000 [ 872.508973] x27: ffff807ef691a0e0 x26: 0000000000000000 [ 872.519116] x25: 0000000000000000 x24: ffff0000090a7980 [ 872.529184] x23: ffff000009272060 x22: 0000000100022b11 [ 872.539144] x21: 0000000046aa5668 x20: ffff80bee8562b18 [ 872.549000] x19: ffff80bee8562080 x18: 0000000000000000 [ 872.558876] x17: 0000000000000000 x16: 0000000000000000 [ 872.568976] x15: 0000000000000000 x14: 0000000000000000 [ 872.578762] x13: 0000000000000000 x12: 0000000000000000 [ 872.588474] x11: 0000000000000000 x10: 0000000000000c40 [ 872.598324] x9 : ffff000008100c00 x8 : 000000007ffff000 [ 872.608014] x7 : ffff80bee8562080 x6 : ffff80beea862d30 [ 872.617709] x5 : 0000000000000000 x4 : ffff80beea862d48 [ 872.627399] x3 : ffff80bee8562b18 x2 : 0000000000000000 [ 872.637044] x1 : ffff0000090a7000 x0 : 0000000000208040 [ 872.646575] Call trace: [ 872.653139] task_numa_work+0x4c/0x310 [ 872.660916] task_work_run+0xb0/0xe0 [ 872.668400] io_sq_thread+0x164/0x388 [ 872.675829] kthread+0x108/0x138 The reason is that once io_sq_thread has a valid mm, schedule subsystem may call task_tick_numa() adding a task_numa_work() callback, which will visit mm, then above panic will happen. To fix this bug, only call task_work_run() before dropping mm. Signed-off-by: Xiaoguang Wang --- fs/io_uring.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 6391a00ff8b7..32381984b2a6 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -6134,6 +6134,13 @@ static int io_sq_thread(void *data) * to enter the kernel to reap and flush events. */ if (!to_submit || ret == -EBUSY) { + /* + * Current task context may already have valid mm, that + * means some works that visit mm may have been queued, + * so we must execute the works before dropping mm. + */ + if (current->task_works) + task_work_run(); /* * Drop cur_mm before scheduling, we can't hold it for * long periods (or over schedule()). Do this before @@ -6152,8 +6159,6 @@ static int io_sq_thread(void *data) if (!list_empty(&ctx->poll_list) || (!time_after(jiffies, timeout) && ret != -EBUSY && !percpu_ref_is_dying(&ctx->refs))) { - if (current->task_works) - task_work_run(); cond_resched(); continue; } @@ -6185,11 +6190,7 @@ static int io_sq_thread(void *data) finish_wait(&ctx->sqo_wait, &wait); break; } - if (current->task_works) { - task_work_run(); - finish_wait(&ctx->sqo_wait, &wait); - continue; - } + if (signal_pending(current)) flush_signals(current); schedule(); -- 2.17.2