[Intel-gfx] [PATCH 03/12] drm/i915: Reduce the time we hold struct mutex in sprite update_plane code

Ville Syrjälä ville.syrjala at linux.intel.com
Fri Oct 4 12:40:08 CEST 2013

On Fri, Oct 04, 2013 at 11:21:20AM +0100, Chris Wilson wrote:
> On Tue, Oct 01, 2013 at 06:02:12PM +0300, ville.syrjala at linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > We used to call the entire intel specific update_plane hook while
> > holding struct_mutex. Actually we only need to hold struct_mutex while
> > pinning/unpinning the obj. The plane state itself is protected by the
> > kms locks, and as the object is pinned we can dig out the offset and
> > tiling information from it without fearing that it would change
> > underneath us.
> > 
> > So now we don't need to drop and reacquire the lock around the
> > wait_for_vblank. Also we will need another wait_for_vblank in the IVB
> > specific update_plane hook, and this way we don't need to worry about
> > struct_mutex there either.
> > 
> > Also move the intel_plane->obj=NULL assignment outside strut_mutex in
> > disable_plane to make it clear that it's not protected by struct_mutex.
> intel_update_fbc() needs to be taken out and shot. It needs the mode
> lock, crtc lock and the struct_mutex.
> This patch looks fine, but anything touching fbc just makes me want to
> curl up in a corner and whimper. Friends don't let friends enable fbc!

Yeah, I have to fight the urge to beat that guy into shape every time I
come across it. I fear it's going to be another rathole, which is why
I'm trying to hold off until I've managed to clear my board of other
tasks a bit.

Ville Syrjälä
Intel OTC

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