Merge 168093 - Don't wait endlessly for flushing the batched queries sent to the GPU driver

content/common/gpu/media/dxva_video_decode_accelerator.cc

Index: content/common/gpu/media/dxva_video_decode_accelerator.cc
===================================================================
--- content/common/gpu/media/dxva_video_decode_accelerator.cc	(revision 168333)
+++ content/common/gpu/media/dxva_video_decode_accelerator.cc	(working copy)
@@ -73,6 +73,11 @@
                                log << ", HRESULT: 0x" << std::hex << result, \
                                error_code, ret);
 
+// Maximum number of iterations we allow before aborting the attempt to flush
+// the batched queries to the driver and allow torn/corrupt frames to be
+// rendered.
+enum { kMaxIterationsForD3DFlush = 10 };
+
 static IMFSample* CreateEmptySample() {
   base::win::ScopedComPtr<IMFSample> sample;
   HRESULT hr = MFCreateSample(sample.Receive());
@@ -312,6 +317,7 @@
       D3DPOOL_DEFAULT,
       picture_buffer->decoding_texture_.Receive(),
       &share_handle);
+
   RETURN_ON_HR_FAILURE(hr, "Failed to create texture",
                        linked_ptr<DXVAPictureBuffer>(NULL));
   return picture_buffer;
@@ -392,15 +398,30 @@
                               D3DTEXF_NONE);
     RETURN_ON_HR_FAILURE(hr, "Colorspace conversion via StretchRect failed",
                          false);
+
     // Ideally, this should be done immediately before the draw call that uses
     // the texture. Flush it once here though.
     hr = query_->Issue(D3DISSUE_END);
     RETURN_ON_HR_FAILURE(hr, "Failed to issue END", false);
-    do {
-      hr = query_->GetData(NULL, 0, D3DGETDATA_FLUSH);
-      if (hr == S_FALSE)
-        Sleep(1);  // Poor-man's Yield().
-    } while (hr == S_FALSE);
+
+    // The DXVA decoder has its own device which it uses for decoding. ANGLE
+    // has its own device which we don't have access to.
+    // The above code attempts to copy the decoded picture into a surface
+    // which is owned by ANGLE. As there are multiple devices involved in
+    // this, the StretchRect call above is not synchronous.
+    // We attempt to flush the batched operations to ensure that the picture is
+    // copied to the surface owned by ANGLE.
+    // We need to do this in a loop and call flush multiple times.
+    // We have seen the GetData call for flushing the command buffer fail to
+    // return success occassionally on multi core machines, leading to an
+    // infinite loop.
+    // Workaround is to have an upper limit of 10 on the number of iterations to
+    // wait for the Flush to finish.
+    int iterations = 0;
+    while ((query_->GetData(NULL, 0, D3DGETDATA_FLUSH) == S_FALSE) &&
+            ++iterations < kMaxIterationsForD3DFlush) {
+      Sleep(1);  // Poor-man's Yield().
+    }
     eglBindTexImage(
         static_cast<EGLDisplay*>(eglGetDisplay(EGL_DEFAULT_DISPLAY)),
         decoding_surface_,
@@ -497,7 +518,6 @@
   // CopyOutputSampleDataToPictureBuffer).
   hr = query_->Issue(D3DISSUE_END);
   RETURN_ON_HR_FAILURE(hr, "Failed to issue END test query", false);
-
   return true;
 }