drm/i915: Unwrap top level fence-array

By first unwrapping an incoming fence-array into its child fences, we
can simplify the internal branching, and so avoid triggering a potential
bug in the next patch when not squashing the child fences on the same
timeline.

It will also have the advantage of keeping the (top-level) fence arrays
out of any fence/timeline caching since these are unordered timelines
but with a random context id.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170503093924.5320-2-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 6198f6997d055080b2df99e3dc941c3f0de06225..b68935d056c50480c50388c76fcbd42163944f4e 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -743,22 +743,9 @@ int
 i915_gem_request_await_dma_fence(struct drm_i915_gem_request *req,
                                 struct dma_fence *fence)
 {
-       struct dma_fence_array *array;
+       struct dma_fence **child = &fence;
+       unsigned int nchild = 1;
        int ret;
-       int i;
-
-       if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
-               return 0;
-
-       if (dma_fence_is_i915(fence))
-               return i915_gem_request_await_request(req, to_request(fence));
-
-       if (!dma_fence_is_array(fence)) {
-               ret = i915_sw_fence_await_dma_fence(&req->submit,
-                                                   fence, I915_FENCE_TIMEOUT,
-                                                   GFP_KERNEL);
-               return ret < 0 ? ret : 0;
-       }
 
        /* Note that if the fence-array was created in signal-on-any mode,
         * we should *not* decompose it into its individual fences. However,
@@ -767,21 +754,29 @@ i915_gem_request_await_dma_fence(struct drm_i915_gem_request *req,
         * amdgpu and we should not see any incoming fence-array from
         * sync-file being in signal-on-any mode.
         */
+       if (dma_fence_is_array(fence)) {
+               struct dma_fence_array *array = to_dma_fence_array(fence);
+
+               child = array->fences;
+               nchild = array->num_fences;
+               GEM_BUG_ON(!nchild);
+       }
 
-       array = to_dma_fence_array(fence);
-       for (i = 0; i < array->num_fences; i++) {
-               struct dma_fence *child = array->fences[i];
+       do {
+               fence = *child++;
+               if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+                       continue;
 
-               if (dma_fence_is_i915(child))
+               if (dma_fence_is_i915(fence))
                        ret = i915_gem_request_await_request(req,
-                                                            to_request(child));
+                                                            to_request(fence));
                else
-                       ret = i915_sw_fence_await_dma_fence(&req->submit,
-                                                           child, I915_FENCE_TIMEOUT,
+                       ret = i915_sw_fence_await_dma_fence(&req->submit, fence,
+                                                           I915_FENCE_TIMEOUT,
                                                            GFP_KERNEL);
                if (ret < 0)
                        return ret;
-       }
+       } while (--nchild);
 
        return 0;
 }