From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: INFO: task hung in wb_shutdown (2) To: Jens Axboe , Jan Kara , Tejun Heo Cc: syzbot , christophe.jaillet@wanadoo.fr, LKML , linux-mm , syzkaller-bugs@googlegroups.com, weiping zhang , Linus Torvalds , Andrew Morton , Dmitry Vyukov , linux-block@vger.kernel.org References: <94eb2c05b2d83650030568cc8bd9@google.com> From: Tetsuo Handa Message-ID: <43302799-1c50-4cab-b974-9fe1ca584813@I-love.SAKURA.ne.jp> Date: Tue, 1 May 2018 19:27:14 +0900 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 List-ID: Tejun, Jan, Jens, Can you review this patch? syzbot has hit this bug for nearly 4000 times but is still unable to find a reproducer. Therefore, the only way to test would be to apply this patch upstream and test whether the problem is solved. On 2018/04/24 21:19, Tetsuo Handa wrote: >>>>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) > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754765AbeEAK1n (ORCPT ); Tue, 1 May 2018 06:27:43 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:33499 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750994AbeEAK1j (ORCPT ); Tue, 1 May 2018 06:27:39 -0400 Subject: Re: INFO: task hung in wb_shutdown (2) To: Jens Axboe , Jan Kara , Tejun Heo Cc: syzbot , christophe.jaillet@wanadoo.fr, LKML , linux-mm , syzkaller-bugs@googlegroups.com, weiping zhang , Linus Torvalds , Andrew Morton , Dmitry Vyukov , linux-block@vger.kernel.org References: <94eb2c05b2d83650030568cc8bd9@google.com> From: Tetsuo Handa Message-ID: <43302799-1c50-4cab-b974-9fe1ca584813@I-love.SAKURA.ne.jp> Date: Tue, 1 May 2018 19:27:14 +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: 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 Tejun, Jan, Jens, Can you review this patch? syzbot has hit this bug for nearly 4000 times but is still unable to find a reproducer. Therefore, the only way to test would be to apply this patch upstream and test whether the problem is solved. On 2018/04/24 21:19, Tetsuo Handa wrote: >>>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) >