[Intel-gfx] [PATCH] drm: Make each driver's struct_mutex its own subclass

[Chris Wilson]

On Sat, Dec 10, 2016 at 09:23:35PM +0000, Chris Wilson wrote:
> On Sat, Dec 10, 2016 at 10:19:30PM +0100, Daniel Vetter wrote:
> > On Fri, Dec 09, 2016 at 04:52:32PM +0000, Chris Wilson wrote:
> > > With prime, we are running into false circular dependencies based on the
> > > order in which two drivers may lock their own struct_mutex wrt to a
> > > common lock (like the reservation->lock). Work around this by adding the
> > > lock_class_key to the struct drm_driver such that each driver can have
> > > its own subclass of struct_mutex. Circular dependencies between drivers
> > > will now be ignored, but real circular dependencies on any one mutex
> > > will still be caught. A driver creating more than one device will still
> > > need to be careful!
> > > 
> > > Reported-by: Tobias Klausmann <tobias.johannes.klausmann at mni.thm.de>
> > > Reported-by: Hans de Goede <hdegoede at redhat.com>
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > 
> > Where does this even happen? i915, msm and udl are the only drivers left
> > over that do struct_mutex, and i915 can't really share buffers with msm,
> > and udl doesn't do reservations. How exactly does this still go boom in
> > latest upstream?
> 
> How about cc: stable?
> 
> The reports are nouveau vs i915. I was quite pleased with the
> drm_driver_class!

Ah, you may have removed any direct calls to struct_mutex from nouveau,
but it is still using struct_mutex around its GEM bo references.

git grep drm_gem_object_unreference_unlocked -- drivers/gpu/drm/nouveau/ | wc -l
13
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre