Bug 1467363: Protect access to mTransparentSurface with a lock. r=rhunt

MozReview-Commit-ID: 6E9YpDIcuQk

widget/windows/WinCompositorWidget.cpp

@@ -19,6 +19,7 @@ namespace mozilla {
 namespace widget {
 
 using namespace mozilla::gfx;
+using namespace mozilla;
 
 WinCompositorWidget::WinCompositorWidget(const WinCompositorWidgetInitData& aInitData,
                                          const layers::CompositorOptions& aOptions)
@@ -26,6 +27,7 @@ WinCompositorWidget::WinCompositorWidget(const WinCompositorWidgetInitData& aIni
  , mWidgetKey(aInitData.widgetKey()),
    mWnd(reinterpret_cast<HWND>(aInitData.hWnd())),
    mCompositorWnd(nullptr),
+   mTransparentSurfaceLock("mTransparentSurfaceLock"),
    mTransparencyMode(aInitData.transparencyMode()),
    mMemoryDC(nullptr),
    mCompositeDC(nullptr),
@@ -48,6 +50,7 @@ WinCompositorWidget::~WinCompositorWidget()
 void
 WinCompositorWidget::OnDestroyWindow()
 {
+  MutexAutoLock lock(mTransparentSurfaceLock);
   mTransparentSurface = nullptr;
   mMemoryDC = nullptr;
 }
@@ -84,6 +87,8 @@ WinCompositorWidget::GetClientSize()
 already_AddRefed<gfx::DrawTarget>
 WinCompositorWidget::StartRemoteDrawing()
 {
+  MutexAutoLock lock(mTransparentSurfaceLock);
+
   MOZ_ASSERT(!mCompositeDC);
 
   RefPtr<gfxASurface> surf;
@@ -244,6 +249,7 @@ WinCompositorWidget::LeavePresentLock()
 RefPtr<gfxASurface>
 WinCompositorWidget::EnsureTransparentSurface()
 {
+  mTransparentSurfaceLock.AssertCurrentThreadOwns();
   MOZ_ASSERT(mTransparencyMode == eTransparencyTransparent);
 
   IntSize size = GetClientSize().ToUnknownSize();
@@ -260,6 +266,7 @@ WinCompositorWidget::EnsureTransparentSurface()
 void
 WinCompositorWidget::CreateTransparentSurface(const gfx::IntSize& aSize)
 {
+  mTransparentSurfaceLock.AssertCurrentThreadOwns();
   MOZ_ASSERT(!mTransparentSurface && !mMemoryDC);
   RefPtr<gfxWindowsSurface> surface = new gfxWindowsSurface(aSize, SurfaceFormat::A8R8G8B8_UINT32);
   mTransparentSurface = surface;
@@ -269,6 +276,7 @@ WinCompositorWidget::CreateTransparentSurface(const gfx::IntSize& aSize)
 void
 WinCompositorWidget::UpdateTransparency(nsTransparencyMode aMode)
 {
+  MutexAutoLock lock(mTransparentSurfaceLock);
   if (mTransparencyMode == aMode) {
     return;
   }
@@ -285,6 +293,7 @@ WinCompositorWidget::UpdateTransparency(nsTransparencyMode aMode)
 void
 WinCompositorWidget::ClearTransparentWindow()
 {
+  MutexAutoLock lock(mTransparentSurfaceLock);
   if (!mTransparentSurface) {
     return;
   }

widget/windows/WinCompositorWidget.h

@@ -10,6 +10,7 @@
 #include "gfxASurface.h"
 #include "mozilla/gfx/CriticalSection.h"
 #include "mozilla/gfx/Point.h"
+#include "mozilla/Mutex.h"
 #include "nsIWidget.h"
 
 class nsWindow;
@@ -106,6 +107,8 @@ public:
   void DestroyCompositorWindow();
   void UpdateCompositorWndSizeIfNecessary();
 
+  mozilla::Mutex& GetTransparentSurfaceLock() { return mTransparentSurfaceLock; }
+
 protected:
 
 private:
@@ -124,6 +127,7 @@ private:
   gfx::CriticalSection mPresentLock;
 
   // Transparency handling.
+  mozilla::Mutex mTransparentSurfaceLock;
   nsTransparencyMode mTransparencyMode;
   RefPtr<gfxASurface> mTransparentSurface;
   HDC mMemoryDC;

widget/windows/nsWindowGfx.cpp

@@ -325,6 +325,8 @@ bool nsWindow::OnPaint(HDC aDC, uint32_t aNestingLevel)
 #if defined(MOZ_XUL)
           // don't support transparency for non-GDI rendering, for now
           if (eTransparencyTransparent == mTransparencyMode) {
+            // This mutex needs to be held when EnsureTransparentSurface is called.
+            MutexAutoLock lock(mBasicLayersSurface->GetTransparentSurfaceLock());
             targetSurface = mBasicLayersSurface->EnsureTransparentSurface();
           }
 #endif