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

[Mark Rutland <mark.rutland@arm.com>]

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.