From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Jens Axboe <axboe@kernel.dk>, Jan Kara <jack@suse.cz>,
Tejun Heo <tj@kernel.org>
Cc: syzbot <syzbot+c0cf869505e03bdf1a24@syzkaller.appspotmail.com>,
christophe.jaillet@wanadoo.fr,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
syzkaller-bugs@googlegroups.com,
weiping zhang <zhangweiping@didichuxing.com>
Subject: Re: INFO: task hung in wb_shutdown (2)
Date: Tue, 24 Apr 2018 21:19:54 +0900 [thread overview]
Message-ID: <e56c1600-8923-dd6b-d065-c2fd2a720404@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <94eb2c05b2d83650030568cc8bd9@google.com>
>From 39ed6be8a2c12dfe54feaa5abbc2ec46103022bf Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.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@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+c0cf869505e03bdf1a24@syzkaller.appspotmail.com>
Fixes: 5318ce7d46866e1d ("bdi: Shutdown writeback on all cgwbs in cgwb_bdi_destroy()")
Cc: Tejun Heo <tj@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@fb.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
next prev parent reply other threads:[~2018-04-24 12:20 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-01 17:10 INFO: task hung in wb_shutdown (2) syzbot
2018-04-24 12:19 ` Tetsuo Handa [this message]
2018-05-01 10:27 ` Tetsuo Handa
2018-05-01 16:06 ` Linus Torvalds
2018-05-01 21:30 ` Jens Axboe
2018-05-01 22:14 ` Tetsuo Handa
2018-05-03 15:13 ` Jan Kara
2018-05-03 15:25 ` Jens Axboe
2018-05-01 16:12 ` Jens Axboe
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