Re: [CI 10/21] drm/i915: Mark up all locked waiters

["chris@chris-wilson.co.uk" <chris@chris-wilson.co.uk>]

On Tue, Sep 13, 2016 at 03:21:48PM +0300, Mika Kuoppala wrote:
> Mika Kuoppala <mika.kuoppala@linux.intel.com> writes:
> > "Zanoni, Paulo R" <paulo.r.zanoni@intel.com> writes:
> >>> +#if IS_ENABLED(CONFIG_LOCKDEP)
> >>> +	GEM_BUG_ON(!!lockdep_is_held(&req->i915->drm.struct_mutex)
> >>> !=
> >>> +		   !!(flags & I915_WAIT_LOCKED));
> >>> +#endif
> >>
> >> I'm hitting this on my SKL. It usually happens right after the login,
> >> when I click the terminal icon on the toolbar in order to open it (on
> >> Cinnamon). When it doesn't happen at that time, I just open a browser
> >> and browse for like 30 seconds until it happens.
> >>
> >> I did manual reverts of this series up to this patch and obviously the
> >> problem goes away (no more GEM_BUG_ON to hit). I didn't try to do a
> >> real bisect to check if this is the first bad commit or if it's
> >> something later on the series. It could even be an older problem that
> >> just got exposed by the new BUG(). I'm available to test patches, just
> >> send them to me.
> >
> > No patches yet but there is a comment on 
> > intel_prepare_plane_fb() that says that it must be called with mutex
> > held.
> >
> > Quite likely the new GEM_BUG_ON catches this not being true.
> >
> 
> As Chris pointed out in irc, its about the reverse. Waiting
> with mutex when you shouldn't.

Fwiw, the fix is now on the list.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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