Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64

From	Mark Rutland <mark.rutland@arm.com>
Newsgroups	linux.kernel
Subject	Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64
Date	2017-08-08 19:10 +0200
Message-ID	<ucgaZ-2XK-5@gated-at.bofh.it> (permalink)
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On Tue, Aug 08, 2017 at 05:44:22PM +0100, Mel Gorman wrote:
> On Tue, Aug 08, 2017 at 09:06:48AM -0700, Linus Torvalds wrote:
> > On Tue, Aug 8, 2017 at 8:41 AM, Mark Rutland <mark.rutland@arm.com> wrote:
> > >
> > > With my __BUG_FLAGS() issue corrected, the WARN_ON_ONCE() fires once,
> > > and everything else seems fine. I'll have a go with additional debug
> > > enabled just in case.
> > 
> > Ok, great, a - mostly - false alarm.

Indeed; sorry for the somewhat bogus report.

> > I do wonder if we should just remove even that WARN_ON_ONCE() - I
> > think it was added to be careful, and the code seems to do the right
> > thing.

> If Mark confirms that removing the warning is ok for his test case, I'll
> send a patch to Thomas with a tag for stable and it should arrive at your
> inbox eventually. If I don't hear from Mark, I'll have time to try the
> test case in the morning and go from there.

So far my test case hasn't triggered any other noticeable issue, nor
splats from any debug option I have enabled, so removing the warning
sounds good to me.

I'll throw Syzkaller at a kernel with the warning removed. Given this is
the first time I've hit this after many days worth of fuzzing recent
kernels, I suspect it won't hit anything interesting by tomorrow
morning.

Thanks,
Mark.

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kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64 Mark Rutland <mark.rutland@arm.com> - 2017-08-08 13:00 +0200
  Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64 Mark Rutland <mark.rutland@arm.com> - 2017-08-08 17:00 +0200
    Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64 Mark Rutland <mark.rutland@arm.com> - 2017-08-08 17:20 +0200
  Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64 Mel Gorman <mgorman@suse.de> - 2017-08-08 17:40 +0200
    Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64 Mark Rutland <mark.rutland@arm.com> - 2017-08-08 17:50 +0200
      Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64 Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-08 18:10 +0200
        Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64 Mel Gorman <mgorman@suse.de> - 2017-08-08 18:50 +0200
          Re: kernel BUG at kernel/futex.c:679 on v4.13-rc3-ish on arm64 Mark Rutland <mark.rutland@arm.com> - 2017-08-08 19:10 +0200

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