Re: possible deadlock in send_sigurg (2)

[Boqun Feng]

Hi,

On Wed, Nov 04, 2020 at 04:18:08AM -0800, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit e918188611f073063415f40fae568fa4d86d9044
> Author: Boqun Feng <boqun.feng@xxxxxxxxx>
> Date:   Fri Aug 7 07:42:20 2020 +0000
> 
>     locking: More accurate annotations for read_lock()
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14142732500000
> start commit:   4ef8451b Merge tag 'perf-tools-for-v5.10-2020-11-03' of gi..
> git tree:       upstream
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=16142732500000
> console output: https://syzkaller.appspot.com/x/log.txt?x=12142732500000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=61033507391c77ff
> dashboard link: https://syzkaller.appspot.com/bug?extid=c5e32344981ad9f33750
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15197862500000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13c59f6c500000
> 
> Reported-by: syzbot+c5e32344981ad9f33750@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: e918188611f0 ("locking: More accurate annotations for read_lock()")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Thanks for reporting this, and this is actually a deadlock potential
detected by the newly added recursive read deadlock detection as my
analysis:

	https://lore.kernel.org/lkml/20200910071523.GF7922@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Besides, other reports[1][2] are caused by the same problem. I made a
fix for this, please have a try and see if it's get fixed.

Regards,
Boqun

[1]: https://lore.kernel.org/lkml/000000000000d7136005aee14bf9@xxxxxxxxxx
[2]: https://lore.kernel.org/lkml/0000000000006e29ed05b3009b04@xxxxxxxxxx

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