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

Chris Wilson chris at chris-wilson.co.uk
Fri Oct 4 12:21:20 CEST 2013

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!

Chris Wilson, Intel Open Source Technology Centre

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