Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super() and thaw_super() paths

From	Oleg Nesterov <oleg@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super() and thaw_super() paths
Date	2016-10-13 19:00 +0200
Message-ID	<srRwn-615-59@gated-at.bofh.it> (permalink)
References	(5 earlier) <spoRP-6HK-9@gated-at.bofh.it> <spGYp-3AS-5@gated-at.bofh.it> <spMhs-749-5@gated-at.bofh.it> <sqoZr-6sA-9@gated-at.bofh.it> <sqxq1-37Y-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Dave, I am sorry for delay.

On 10/10, Dave Chinner wrote:
>
> So, it's time to waste more time explaining why lockdep is telling
> us about something that *isn't a bug*.
> [... snip ...]

OK, thanks. I am not surprised although I have to admit I wasn't sure.

> Basically, what we are seeing here is yet another case of "lockdep
> is just smart enough to be really dumb" because we cannot fully
> express or cleanly annotate the contexts in which it is being asked
> to validate.

Yes... perhaps we can add the new lockdep helpers to avoid the false-
positives like this one, but so far it is not clear to me what we can do.
Somehow we need to tell it to to avoid check_prev_add() because we know
that the work function won't take sb_internal, but at the same time we
should complain if it actually does this. Lets ignore this patch for now.

Oleg.

Thread

[PATCH 0/2] (Was: BUG_ON in rcu_sync_func triggered) Oleg Nesterov <oleg@redhat.com> - 2016-09-26 18:10 +0200
  [PATCH 2/2] fs/super.c: don't fool lockdep in freeze_super() and  thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-09-26 18:10 +0200
    Re: [PATCH 2/2] fs/super.c: don't fool lockdep in freeze_super() and  thaw_super() paths Jan Kara <jack@suse.cz> - 2016-09-26 18:20 +0200
      [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super() and  thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-09-26 19:00 +0200
        Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Jan Kara <jack@suse.cz> - 2016-09-27 09:00 +0200
          Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Dave Chinner <david@fromorbit.com> - 2016-09-27 09:20 +0200
          Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-09-27 19:30 +0200
            Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-09-30 19:20 +0200
              Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Dave Chinner <david@fromorbit.com> - 2016-10-02 23:50 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in         freeze_super() and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-03 18:50 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-04 19:00 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Dave Chinner <david@fromorbit.com> - 2016-10-04 22:10 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-05 18:40 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Dave Chinner <david@fromorbit.com> - 2016-10-04 21:50 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-05 18:50 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Jan Kara <jack@suse.cz> - 2016-10-06 09:30 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-06 19:20 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Dave Chinner <david@fromorbit.com> - 2016-10-07 00:00 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-07 19:20 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Dave Chinner <david@fromorbit.com> - 2016-10-08 01:00 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in         freeze_super() and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-09 18:20 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Dave Chinner <david@fromorbit.com> - 2016-10-10 03:20 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in         freeze_super() and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-13 19:00 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in freeze_super()  and thaw_super() paths Johannes Weiner <hannes@cmpxchg.org> - 2016-10-06 15:50 +0200
                Re: [PATCH V2 2/2] fs/super.c: don't fool lockdep in         freeze_super() and thaw_super() paths Oleg Nesterov <oleg@redhat.com> - 2016-10-07 19:00 +0200
  [PATCH 1/2] fs/super.c: fix race between freeze_super() and  thaw_super() Oleg Nesterov <oleg@redhat.com> - 2016-09-26 18:10 +0200
    Re: [PATCH 1/2] fs/super.c: fix race between freeze_super() and  thaw_super() Jan Kara <jack@suse.cz> - 2016-09-26 18:20 +0200
  Re: [PATCH 0/2] (Was: BUG_ON in rcu_sync_func triggered) Oleg Nesterov <oleg@redhat.com> - 2016-10-13 19:20 +0200

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