Use GrSemaphore rather than GrFence for external texture data

BUG=skia:

Change-Id: I0d23eb9dcf5c01c71d3571ef97690af68b900807
Reviewed-on: https://skia-review.googlesource.com/9141
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

4 files changed, 36 insertions, 11 deletions

diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 97b525d7ef..7dfee00ed2 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -546,13 +546,6 @@ void GrContext::prepareSurfaceForExternalIO(GrSurface* surface) {
     fDrawingManager->prepareSurfaceForExternalIO(surface);
 }
 
-GrFence GrContext::prepareSurfaceForExternalIOAndFlush(GrSurface* surface) {
-    this->prepareSurfaceForExternalIO(surface);
-    GrFence fence = fGpu->insertFence();
-    fGpu->flush();
-    return fence;
-}
-
 void GrContext::flushSurfaceWrites(GrSurface* surface) {
     ASSERT_SINGLE_OWNER
     RETURN_IF_ABANDONED
diff --git a/src/gpu/GrSemaphore.h b/src/gpu/GrSemaphore.h
index bdeff09ec2..717b4bb506 100644
--- a/src/gpu/GrSemaphore.h
+++ b/src/gpu/GrSemaphore.h
@@ -13,7 +13,7 @@
 class GrGpu;
 
 class GrSemaphore : public SkRefCnt {
-public:
+private:
     // This function should only be used in the case of exporting and importing a GrSemaphore object
     // from one GrContext to another. When exporting, the GrSemaphore should be set to a null GrGpu,
     // and when importing it should be set to the GrGpu of the current context. Once exported, a
@@ -23,6 +23,8 @@ public:
 protected:
     explicit GrSemaphore(const GrGpu* gpu) : fGpu(gpu) {}
 
+    friend class GrGLExternalTextureData; // resetGpu
+
     const GrGpu* fGpu;
 };
 
diff --git a/src/gpu/gl/GrGLExternalTextureData.cpp b/src/gpu/gl/GrGLExternalTextureData.cpp
new file mode 100644
index 0000000000..32c49b17a8
--- /dev/null
+++ b/src/gpu/gl/GrGLExternalTextureData.cpp
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrContext.h"
+#include "GrGpu.h"
+#include "GrSemaphore.h"
+#include "gl/GrGLTypes.h"
+
+GrGLExternalTextureData::GrGLExternalTextureData(const GrGLTextureInfo& info,
+                                                 sk_sp<GrSemaphore> semaphore)
+        : fInfo(info)
+        , fSemaphore(std::move(semaphore)) {
+    SkASSERT(fSemaphore->unique());
+    fSemaphore->resetGpu(nullptr);
+}
+
+void GrGLExternalTextureData::attachToContext(GrContext* context) {
+    fSemaphore->resetGpu(context->getGpu());
+    context->getGpu()->waitSemaphore(fSemaphore);
+}
diff --git a/src/gpu/gl/GrGLTexture.cpp b/src/gpu/gl/GrGLTexture.cpp
index a5609887c0..ee029bc9a0 100644
--- a/src/gpu/gl/GrGLTexture.cpp
+++ b/src/gpu/gl/GrGLTexture.cpp
@@ -8,6 +8,7 @@
 #include "GrContext.h"
 #include "GrGLTexture.h"
 #include "GrGLGpu.h"
+#include "GrSemaphore.h"
 #include "GrShaderCaps.h"
 #include "SkMakeUnique.h"
 #include "SkTraceMemoryDump.h"
@@ -114,11 +115,16 @@ GrBackendObject GrGLTexture::getTextureHandle() const {
 }
 
 std::unique_ptr<GrExternalTextureData> GrGLTexture::detachBackendTexture() {
-    // Flush any pending writes to this texture, as well GL itself
-    GrFence fence = this->getContext()->prepareSurfaceForExternalIOAndFlush(this);
+    // Flush any pending writes to this texture
+    this->getContext()->prepareSurfaceForExternalIO(this);
+
+    // Set up a semaphore to be signaled once the data is ready, and flush GL
+    sk_sp<GrSemaphore> semaphore = this->getGpu()->makeSemaphore();
+    this->getGpu()->insertSemaphore(semaphore);
+    this->getGpu()->flush();
 
     // Make a copy of our GL-specific information
-    auto data = skstd::make_unique<GrGLExternalTextureData>(fInfo, fence);
+    auto data = skstd::make_unique<GrGLExternalTextureData>(fInfo, std::move(semaphore));
 
     // Ensure the cache can't reach this texture anymore
     this->detachFromCache();