Re: Crashes in next-20160915 (BUG at fs/notify/notification.c:66!)

[Guenter Roeck]

On 09/15/2016 11:45 PM, Jan Kara wrote:
> Hi,
>
> On Thu 15-09-16 19:20:10, Guenter Roeck wrote:
> > I see various architectures crashing in -next with the following error.
> >
> > ------------[ cut here ]------------
> > kernel BUG at fs/notify/notification.c:66!
>
> Thanks for report!
>
> ...
>
> > Call Trace:
> >  [<ffffffff811bd532>] inotify_poll+0x42/0x70
> >  [<ffffffff811bfeba>] SyS_epoll_ctl+0x84a/0xf60
> >  [<ffffffff811be4a0>] ? ep_send_events_proc+0x180/0x180
> >  [<ffffffff8176be98>] entry_SYSCALL_64_fastpath+0x13/0x8f
> > Code: 90 90 0f 1f 44 00 00 55 b8 01 00 00 00 48 89 e5 0f c1 05 bb e4 d4 00 83 c0 01 5d c3 66 0f 1f 44 00 00 0f 1f 44 00 00 55 48 89 e5 <0f> 0b 0f 1f 44 00 00 0f 1f 44 00 00 55 48 89 e5 48 83 ec 10 48
> > RIP  [<ffffffff811bb399>] fsnotify_notify_queue_is_empty+0x9/0x10
> >  RSP <ffffc90000253e68>
> > ---[ end trace 7dc4a27003f0b575 ]---
> >
> > I didn't bisect, but I would guess the culprit is one of the new patches in the
> > affected file.
> >
> > 22e9cf146d3b fanotify: fix possible false warning when freeing events
> > ced89591817c fsnotify: convert notification_mutex to a spinlock
> > f82fa3d0e7f5 fsnotify: drop notification_mutex before destroying event
> > 782fbc7e8685 fanotify: fix list corruption in fanotify_get_response()
> > 56cf1c8a1b35 fsnotify: add a way to stop queueing events on group shutdown
>
> Yes, very likely my patches cause this. But it must be some config issue
> because my test machine does not hit this and the code is "obviously
> correct" - famous last words ;). I've seen zero-day robot complain as well
> so I'll try the config it had sent me and see what's going on (likely
> spin_is_locked() does not do what I thought under some configs...).

Your builds are probably all SMP builds. Looks like this happens if SMP is disabled.

Guenter