[Intel-gfx] [PATCH 26/43] drm/i915: Only clear the GPU domains upon a successful finish

[Eric Anholt]

On Wed, 14 Dec 2011 13:57:23 +0100, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> From: Chris Wilson <chris at chris-wilson.co.uk>
> 
> By clearing the GPU read domains before waiting upon the buffer, we run
> the risk of the wait being interrupted and the domains prematurely
> cleared. The next time we attempt to wait upon the buffer (after
> userspace handles the signal), we believe that the buffer is idle and so
> skip the wait.
> 
> There are a number of bugs across all generations which show signs of an
> overly haste reuse of active buffers.

I think this patch is better as:

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 683ff1e..cb5ff10 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3126,9 +3126,6 @@ i915_gem_object_finish_gpu(struct drm_i915_gem_object *obj)
 {
        int ret;
 
-       if ((obj->base.read_domains & I915_GEM_GPU_DOMAINS) == 0)
-               return 0;
-
        if (obj->base.write_domain & I915_GEM_GPU_DOMAINS) {
                ret = i915_gem_flush_ring(obj->ring, 0, obj->base.write_domain);
                if (ret)

While I think it was valid other than in this function, the implication
between (read_domains & I915_GEM_GPU_DOMAINS) <-> obj->active is less
clear than just relying on i915_gem_object_wait_rendering()'s use of
obj->active.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 197 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/intel-gfx/attachments/20111216/9e87d6b0/attachment.sig>