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Message-ID: <e56c1600-8923-dd6b-d065-c2fd2a720404@I-love.SAKURA.ne.jp> Date: Tue, 24 Apr 2018 21:19:54 +0900 From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> To: Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>, Tejun Heo <tj@...nel.org> Cc: syzbot <syzbot+c0cf869505e03bdf1a24@...kaller.appspotmail.com>, christophe.jaillet@...adoo.fr, LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, syzkaller-bugs@...glegroups.com, weiping zhang <zhangweiping@...ichuxing.com> Subject: Re: INFO: task hung in wb_shutdown (2) >From 39ed6be8a2c12dfe54feaa5abbc2ec46103022bf Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> 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 <penguin-kernel@...ove.SAKURA.ne.jp> Reported-by: syzbot <syzbot+c0cf869505e03bdf1a24@...kaller.appspotmail.com> Fixes: 5318ce7d46866e1d ("bdi: Shutdown writeback on all cgwbs in cgwb_bdi_destroy()") Cc: Tejun Heo <tj@...nel.org> Cc: Jan Kara <jack@...e.cz> Cc: Jens Axboe <axboe@...com> --- 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
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