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

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Message-ID: <87k2e6sro3.fsf@concordia.ellerman.id.au>
Date:   Tue, 20 Sep 2016 22:05:00 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Jan Kara <jack@...e.cz>, Guenter Roeck <linux@...ck-us.net>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Crashes in next-20160915 (BUG at fs/notify/notification.c:66!)

Andrew Morton <akpm@...ux-foundation.org> writes:
> On Tue, 20 Sep 2016 11:10:35 +1000 Michael Ellerman <mpe@...erman.id.au> wrote:
>> Jan Kara <jack@...e.cz> writes:
>> >
>> > Right, that was the problem. spin_is_locked() without CONFIG_SPINLOCK_DEBUG
>> > returns always 0.
>> 
>> Can we get this fixed soon please? It's breaking all my CI runs.
>
> It should be fixed in next -next.

Great thanks.

I did search LKML to see if Jan had sent a fix but I guess I missed it.

> diff -puN fs/notify/fanotify/fanotify_user.c~fsnotify-convert-notification_mutex-to-a-spinlock-fix fs/notify/fanotify/fanotify_user.c
> --- a/fs/notify/fanotify/fanotify_user.c~fsnotify-convert-notification_mutex-to-a-spinlock-fix
> +++ a/fs/notify/fanotify/fanotify_user.c
> @@ -54,7 +54,8 @@ struct kmem_cache *fanotify_perm_event_c
>  static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
>  					    size_t count)
>  {
> -	BUG_ON(!spin_is_locked(&group->notification_lock));
> +	BUG_ON(IS_ENABLED(CONFIG_SMP) &&
> +	       !spin_is_locked(&group->notification_lock));
  
I thought lockdep_assert_held() was preferred for checks like this that
are purely sanity checking, ie. not part of the algorithm.

cheers