linux-kernel - Re: INFO: task hung in fsnotify_connector_destroy

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Message-ID: <2f4ce251-cf84-8bd2-72fc-a3ff687d5188@I-love.SAKURA.ne.jp>
Date:   Sun, 16 Sep 2018 02:25:53 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     syzbot <syzbot+6fb572170402d311dd39@...kaller.appspotmail.com>,
        amir73il@...il.com, jack@...e.cz, syzkaller-bugs@...glegroups.com
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: INFO: task hung in fsnotify_connector_destroy_workfn (2)

On 2018/09/15 11:33, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    11da3a7f84f1 Linux 4.19-rc3
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=141ffbca400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9917ff4b798e1a1e
> dashboard link: https://syzkaller.appspot.com/bug?extid=6fb572170402d311dd39
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=136a60ae400000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+6fb572170402d311dd39@...kaller.appspotmail.com
> 

Since it kept printk()ing for at least 93 seconds, it might have kept for 150 seconds.

[  174.614333] hid-generic 0000:0000:0000.0003: unknown main item tag 0x0
[  268.196102] INFO: task kworker/u4:1:23 blocked for more than 140 seconds.

Since the reproducer is simple, this might be lockup due to continuous printk().
If syzbot can reliably reproduce this problem using the reproducer, try
ratelimiting printk().