Add a mutex to GrContext::readSurfacePixels to protect against multiple CPU raster threads accessing the same GrContext to read back GPU input data

BUG=chromium:524717

TBR=reed@google.com

Review URL: https://codereview.chromium.org/1329313002

1 files changed, 6 insertions, 0 deletions

diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index 7f1e4109fa..dcff3063b2 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -15,6 +15,7 @@
 #include "GrRenderTarget.h"
 #include "GrTextureProvider.h"
 #include "SkMatrix.h"
+#include "SkMutex.h"
 #include "SkPathEffect.h"
 #include "SkTypes.h"
 
@@ -380,6 +381,11 @@ private:
     bool                            fDidTestPMConversions;
     int                             fPMToUPMConversion;
     int                             fUPMToPMConversion;
+    // The sw backend may call GrContext::readSurfacePixels on multiple threads
+    // We may transfer the responsibilty for using a mutex to the sw backend
+    // when there are fewer code paths that lead to a readSurfacePixels call
+    // from the sw backend.
+    SkMutex                         fReadPixelsMutex;
 
     struct CleanUpData {
         PFCleanUpFunc fFunc;