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From: Alan Jenkins <alan.christopher.jenkins@gmail.com>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	syzkaller-bugs@googlegroups.com
Cc: syzbot <syzbot+c4f9cebf9d651f6e54de@syzkaller.appspotmail.com>,
	linux-block@vger.kernel.org,
	Dan Williams <dan.j.williams@intel.com>,
	Jens Axboe <axboe@kernel.dk>,
	linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org,
	dvyukov@google.com, Bart Van Assche <bart.vanassche@wdc.com>,
	Christoph Hellwig <hch@lst.de>, Hannes Reinecke <hare@suse.com>,
	Johannes Thumshirn <jthumshirn@suse.de>,
	Keith Busch <keith.busch@intel.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Martin Steigerwald <martin@lichtvoll.de>,
	Ming Lei <ming.lei@redhat.com>,
	Oleksandr Natalenko <oleksandr@natalenko.name>,
	Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: INFO: task hung in blk_queue_enter
Date: Wed, 16 May 2018 18:33:36 +0100	[thread overview]
Message-ID: <0609ee2b-fbb6-9122-918a-cc2172ee2cfa@gmail.com> (raw)
In-Reply-To: <b9c33b04-08d7-87a1-3d93-d81a84e6af12@I-love.SAKURA.ne.jp>

 > jbd2/sda1-8(PID=2271) is stuck waiting for journal commit operation.
 > I don't know how this thread is involved to this problem.

It feels like it should be a necessary link in the chain. This is the 
filesystem underneath the loop device. If that hangs, we would expect 
the loop device to hang, but not vice versa.

AIUI, you couldn't reproduce this hang on your own machine.

Don't you think, your fuzzer has just found a nice exploit for reiserfs?

Alan


(It's interesting that you found this hang just after we fixed 
block_queue_enter() to wait in D state instead of S state.[1]  I don't 
know syszkaller, so I assume from this it only flagged this case up 
because of the hung task warning. I.e. syzkaller didn't have its own 
watchdog that would have failed the test anyway.

[1] the commit that caused you to CC me. "block: do not use 
interruptible wait anywhere"

https://github.com/torvalds/linux/commit/1dc3039bc87ae7d19a990c3ee71cfd8a9068f428

)

      parent reply	other threads:[~2018-05-16 17:33 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-28 11:24 syzbot
2018-05-15 11:45 ` Tetsuo Handa
2018-05-16 13:05   ` Tetsuo Handa
2018-05-16 14:56     ` Bart Van Assche
2018-05-16 15:16       ` Dmitry Vyukov
2018-05-16 15:37         ` Bart Van Assche
2018-05-21 21:52           ` Tetsuo Handa
2018-05-22 11:20             ` Tetsuo Handa
2018-06-01 10:10               ` Tetsuo Handa
2018-06-01 17:52                 ` Jens Axboe
2018-06-01 23:49                   ` Ming Lei
2018-06-02  0:49                     ` Jens Axboe
2018-06-02  0:56                       ` Jens Axboe
2018-06-02  2:36                       ` Ming Lei
2018-06-02  4:31                         ` Jens Axboe
2018-06-02  4:54                           ` Ming Lei
2018-06-02  8:07                             ` Martin Steigerwald
2018-06-02 13:48                             ` Jens Axboe
2018-06-05  0:27                   ` Tetsuo Handa
2018-06-05  0:41                     ` Ming Lei
2018-06-07  3:29                       ` Ming Lei
2018-06-07 13:19                         ` Tetsuo Handa
2018-06-04 11:46                 ` Dmitry Vyukov
2018-06-04 13:13                   ` Tetsuo Handa
2018-05-16 17:33     ` Alan Jenkins [this message]

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