Implement offscreenCanvas.getContext('webgl') on a worker thread

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 48 matching lines @@
 #include "modules/webgl/OESTextureHalfFloatLinear.h"
 #include "modules/webgl/OESVertexArrayObject.h"
 #include "modules/webgl/WebGLActiveInfo.h"
 #include "modules/webgl/WebGLBuffer.h"
 #include "modules/webgl/WebGLCompressedTextureASTC.h"
 #include "modules/webgl/WebGLCompressedTextureATC.h"
 #include "modules/webgl/WebGLCompressedTextureETC1.h"
 #include "modules/webgl/WebGLCompressedTexturePVRTC.h"
 #include "modules/webgl/WebGLCompressedTextureS3TC.h"
 #include "modules/webgl/WebGLContextAttributeHelpers.h"
-#include "modules/webgl/WebGLContextAttributes.h"
 #include "modules/webgl/WebGLContextEvent.h"
 #include "modules/webgl/WebGLContextGroup.h"
 #include "modules/webgl/WebGLDebugRendererInfo.h"
 #include "modules/webgl/WebGLDebugShaders.h"
 #include "modules/webgl/WebGLDepthTexture.h"
 #include "modules/webgl/WebGLDrawBuffers.h"
 #include "modules/webgl/WebGLFramebuffer.h"
 #include "modules/webgl/WebGLLoseContext.h"
 #include "modules/webgl/WebGLProgram.h"
 #include "modules/webgl/WebGLRenderbuffer.h"
 #include "modules/webgl/WebGLShader.h"
 #include "modules/webgl/WebGLShaderPrecisionFormat.h"
-#include "modules/webgl/WebGLTexture.h"
 #include "modules/webgl/WebGLUniformLocation.h"
 #include "modules/webgl/WebGLVertexArrayObject.h"
 #include "modules/webgl/WebGLVertexArrayObjectOES.h"
 #include "platform/CheckedInt.h"
 #include "platform/RuntimeEnabledFeatures.h"
+#include "platform/ThreadSafeFunctional.h"
+#include "platform/WaitableEvent.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/UnacceleratedImageBufferSurface.h"
 #include "platform/graphics/gpu/AcceleratedImageBufferSurface.h"
-#include "platform/graphics/gpu/DrawingBuffer.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebGraphicsContext3D.h"
-#include "public/platform/WebGraphicsContext3DProvider.h"
 #include "public/platform/functional/WebFunction.h"
 #include "wtf/Functional.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/text/StringBuilder.h"
 #include "wtf/text/StringUTF8Adaptor.h"
 #include "wtf/typed_arrays/ArrayBufferContents.h"
 
 namespace blink {
 
 namespace {
@@ skipping 390 matching lines @@
     formatWebGLStatusString("Sandboxed", info.sandboxed ? "yes" : "no", statusMessage);
     formatWebGLStatusString("Optimus", info.optimus ? "yes" : "no", statusMessage);
     formatWebGLStatusString("AMD switchable", info.amdSwitchable ? "yes" : "no", statusMessage);
     formatWebGLStatusString("Reset notification strategy", String::format("0x%04x", info.resetNotificationStrategy).utf8().data(), statusMessage);
     formatWebGLStatusString("GPU process crash count", String::number(info.processCrashCount).utf8().data(), statusMessage);
     formatWebGLStatusString("ErrorMessage", info.errorMessage.utf8().data(), statusMessage);
     statusMessage.append(".");
     return statusMessage;
 }
 
-static PassOwnPtr<WebGraphicsContext3DProvider> createWebGraphicsContext3DProviderInternal(HTMLCanvasElement* canvas, ScriptState* scriptState, WebGLContextAttributes attributes, unsigned webGLVersion)
+// A helper function, the reason it exist is because this has to be called in createWebGraphicsContext3DProviderMainThread()
+// because contextProvider->contextGL() checks whether the current thread is the same as the thread that creates contextProvider.
+static bool checkCreatedContext3DProvider(HTMLCanvasElement* canvas, WebGraphicsContext3DProvider* contextProvider, Platform::GraphicsInfo& glInfo)
+{
+    ASSERT(isMainThread());
+    if (!contextProvider || shouldFailContextCreationForTesting) {
+        shouldFailContextCreationForTesting = false;
+        if (canvas)
+            canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, extractWebGLContextCreationError(glInfo)));
+        return false;
+    }
+    gpu::gles2::GLES2Interface* gl = contextProvider->contextGL();

[xidachen, 2016/04/29 15:58:21]

The program works fine on a Release build, but crashes on a debug build. This is
the crash point, the stack trace eventually gets to:

FATAL:context_provider_command_buffer.cc(120)] Check failed:
context_thread_checker_.CalledOnValidThread()

zm@, bajones@: could you take a look? Thank you.

[bajones, 2016/04/29 19:38:25]

Many of our bots run with DCHECKs enabled, so if this is still crashing in debug
it's not appropriate to commit. Is it still failing even though you're doing the
post task to the main thread?

[xidachen, 2016/04/29 19:41:11]

Yes, the current code crashes.

I am quite surprised, as you can see, contextProvider is created on the main
thread, and this function is also called on main thread. In theory, it should
not hit the DCHECK point.

[Justin Novosad, 2016/04/29 19:43:43]

You just have to call ContextProviderCommandBuffer::DetachFromThread() to fix
that, but this is not the right place for it. There is an important design flaw
here: The gl interface should always be used from the same thread. So the calls
to the gl interface below need to happen on the thread that is going to be using
the gl interface, which is not always the main thread. This function is on the
main thread.

[xidachen, 2016/04/30 01:02:33]

Here is what I propose:

We change the WebGraphicsContext3DProvider::contextGL() to
WebGraphicsContext3DProvider::contextGL(bool shouldDetachFromThread=false), then
we change its implementation such that it would call DetachFromThread() only if
the input parameter is true. WDYT?

+    if (!String(gl->GetString(GL_EXTENSIONS)).contains("GL_OES_packed_depth_stencil")) {
+        if (canvas)
+            canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, "OES_packed_depth_stencil support is required."));
+        return false;
+    }
+    return true;
+}
+
+void WebGLRenderingContextBase::createWebGraphicsContext3DProviderMainThread(WebGLRenderingContextBase::createWebGraphicsContext3DProviderUtils* createUtils, WaitableEvent* waitableEvent)
+{
+    ASSERT(isMainThread());
+    Platform::GraphicsInfo glInfo = createUtils->glInfo();
+    OwnPtr<WebGraphicsContext3DProvider> provider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
+        createUtils->contextAttributes(), createUtils->scriptState()->getExecutionContext()->url(), 0, &glInfo));
+    if (checkCreatedContext3DProvider(nullptr, provider.get(), glInfo))
+        createUtils->setContextProvider(provider.release());
+    else
+        createUtils->setContextProvider(nullptr);
+    waitableEvent->signal();
+}
+
+PassOwnPtr<WebGraphicsContext3DProvider> WebGLRenderingContextBase::createWebGraphicsContext3DProviderInternal(HTMLCanvasElement* canvas, ScriptState* scriptState, WebGLContextAttributes attributes, unsigned webGLVersion)
 {
     Platform::ContextAttributes contextAttributes = toPlatformContextAttributes(attributes, webGLVersion);
     Platform::GraphicsInfo glInfo;
     OwnPtr<WebGraphicsContext3DProvider> contextProvider;
     if (canvas) {
         contextProvider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
             contextAttributes, canvas->document().topDocument().url(), 0, &glInfo));
+        if (!checkCreatedContext3DProvider(canvas, contextProvider.get(), glInfo))
+            return nullptr;
     } else {
-        contextProvider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
-            contextAttributes, scriptState->getExecutionContext()->url(), 0, &glInfo));
-    }
-    if (!contextProvider || shouldFailContextCreationForTesting) {
-        shouldFailContextCreationForTesting = false;
-        if (canvas)
-            canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, extractWebGLContextCreationError(glInfo)));
-        return nullptr;
-    }
-    gpu::gles2::GLES2Interface* gl = contextProvider->contextGL();
-    if (!String(gl->GetString(GL_EXTENSIONS)).contains("GL_OES_packed_depth_stencil")) {
-        if (canvas)
-            canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, "OES_packed_depth_stencil support is required."));
-        return nullptr;
+        if (isMainThread()) {
+            contextProvider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
+                contextAttributes, scriptState->getExecutionContext()->url(), 0, &glInfo));
+            if (!checkCreatedContext3DProvider(canvas, contextProvider.get(), glInfo))
+                return nullptr;
+        } else {
+            WaitableEvent waitableEvent;
+            WebTaskRunner* taskRunner = Platform::current()->mainThread()->getWebTaskRunner();
+            OwnPtr<WebGLRenderingContextBase::createWebGraphicsContext3DProviderUtils> createUtils = adoptPtr(new WebGLRenderingContextBase::createWebGraphicsContext3DProviderUtils(contextAttributes, glInfo, scriptState));
+            taskRunner->postTask(BLINK_FROM_HERE, threadSafeBind(&createWebGraphicsContext3DProviderMainThread, AllowCrossThreadAccess(createUtils.get()), AllowCrossThreadAccess(&waitableEvent)));
+            waitableEvent.wait();
+            contextProvider = createUtils->releaseContextProvider();
+        }
     }
 
     return contextProvider.release();
 }
 
 PassOwnPtr<WebGraphicsContext3DProvider> WebGLRenderingContextBase::createWebGraphicsContext3DProvider(HTMLCanvasElement* canvas, WebGLContextAttributes attributes, unsigned webGLVersion)
 {
     Document& document = canvas->document();
     LocalFrame* frame = document.frame();
     if (!frame) {
@@ skipping 5732 matching lines @@
         contextGL()->PixelStorei(GL_UNPACK_ALIGNMENT, 1);
 }
 
 void WebGLRenderingContextBase::restoreUnpackParameters()
 {
     if (m_unpackAlignment != 1)
         contextGL()->PixelStorei(GL_UNPACK_ALIGNMENT, m_unpackAlignment);
 }
 
 } // namespace blink