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

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Message-ID: <20160916124948.GG24269@quack2.suse.cz>
Date:   Fri, 16 Sep 2016 14:49:48 +0200
From:   Jan Kara <jack@...e.cz>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Jan Kara <jack@...e.cz>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Crashes in next-20160915 (BUG at fs/notify/notification.c:66!)

On Fri 16-09-16 04:10:38, Guenter Roeck wrote:
> 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.

Right, that was the problem. spin_is_locked() without CONFIG_SPINLOCK_DEBUG
returns always 0.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR