From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757604AbeDXMUi (ORCPT ); Tue, 24 Apr 2018 08:20:38 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:18813 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756714AbeDXMUh (ORCPT ); Tue, 24 Apr 2018 08:20:37 -0400 Subject: Re: INFO: task hung in wb_shutdown (2) To: Jens Axboe , Jan Kara , Tejun Heo References: <94eb2c05b2d83650030568cc8bd9@google.com> Cc: syzbot , christophe.jaillet@wanadoo.fr, LKML , linux-mm , syzkaller-bugs@googlegroups.com, weiping zhang From: Tetsuo Handa Message-ID: Date: Tue, 24 Apr 2018 21:19:54 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <94eb2c05b2d83650030568cc8bd9@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>From 39ed6be8a2c12dfe54feaa5abbc2ec46103022bf Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Tue, 24 Apr 2018 11:59:08 +0900 Subject: [PATCH] bdi: wake up concurrent wb_shutdown() callers. syzbot is reporting hung tasks at wait_on_bit(WB_shutting_down) in wb_shutdown() [1]. This might be because commit 5318ce7d46866e1d ("bdi: Shutdown writeback on all cgwbs in cgwb_bdi_destroy()") forgot to call wake_up_bit(WB_shutting_down) after clear_bit(WB_shutting_down). [1] https://syzkaller.appspot.com/bug?id=b297474817af98d5796bc544e1bb806fc3da0e5e Signed-off-by: Tetsuo Handa Reported-by: syzbot Fixes: 5318ce7d46866e1d ("bdi: Shutdown writeback on all cgwbs in cgwb_bdi_destroy()") Cc: Tejun Heo Cc: Jan Kara Cc: Jens Axboe --- mm/backing-dev.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 023190c..dadac99 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -384,6 +384,8 @@ static void wb_shutdown(struct bdi_writeback *wb) */ smp_wmb(); clear_bit(WB_shutting_down, &wb->state); + smp_mb(); /* advised by wake_up_bit() */ + wake_up_bit(&wb->state, WB_shutting_down); } static void wb_exit(struct bdi_writeback *wb) -- 1.8.3.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 927056B0005 for ; Tue, 24 Apr 2018 08:20:29 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id z20so13033987pfn.11 for ; Tue, 24 Apr 2018 05:20:29 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id a9si994123pgq.655.2018.04.24.05.20.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 24 Apr 2018 05:20:28 -0700 (PDT) Subject: Re: INFO: task hung in wb_shutdown (2) References: <94eb2c05b2d83650030568cc8bd9@google.com> From: Tetsuo Handa Message-ID: Date: Tue, 24 Apr 2018 21:19:54 +0900 MIME-Version: 1.0 In-Reply-To: <94eb2c05b2d83650030568cc8bd9@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jens Axboe , Jan Kara , Tejun Heo Cc: syzbot , christophe.jaillet@wanadoo.fr, LKML , linux-mm , syzkaller-bugs@googlegroups.com, weiping zhang