[Intel-gfx] [PATCH] RFC: drm/i915: Switch obj->mm.lock lockdep annotations on its head

[Chris Wilson]

Quoting Daniel Vetter (2019-08-15 08:23:01)
> On Wed, Aug 14, 2019 at 07:57:57PM +0100, Chris Wilson wrote:
> > Quoting Daniel Vetter (2019-08-14 19:49:41)
> > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> > > index d474c6ac4100..1ea3c3c96a5a 100644
> > > --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> > > @@ -157,7 +157,15 @@ struct drm_i915_gem_object {
> > >         unsigned int pin_global;
> > >  
> > >         struct {
> > > -               struct mutex lock; /* protects the pages and their use */
> > > +               /*
> > > +                * Protects the pages and their use.
> > 
> > "Their use" is still a misleading suggest of mine. This should be
> > "protects the pinning of pages". The couple of other things it is used
> > for are tied to the concept of the pages being pinned; further use should
> > be discouraged; direct use prohibited.
> 
> So something like "Protects the pinning of pages. Do not use directly, but
> instead go through the get/put_pages and pin/unpin interfaces." There's a
> few too many of those to list them all imo ...

I would say only pin/unpin. get/put is the for implementation.

Fwiw, elsewhere we adopted the name pin_mutex / pin_count. But there's
also variations on that naming scheme. The pattern of "that who is being
pinned may unpin others" is repeating.
-Chris