From 4d9d8d5d59259699150dc07602fc732eba9a1b93 Mon Sep 17 00:00:00 2001
From: David Anderson <danderson@mozilla.com>
Date: Tue, 21 Nov 2017 10:52:38 -0500
Subject: [PATCH] Bug 1416864 - Synchronize how snapshots detach in
 DrawTargetD2D1. r=bas

---
 gfx/2d/DrawTargetD2D1.cpp    | 5 +++++
 gfx/2d/DrawTargetD2D1.h      | 1 +
 gfx/2d/SourceSurfaceD2D1.cpp | 6 ++++++
 gfx/2d/SourceSurfaceD2D1.h   | 1 +
 4 files changed, 13 insertions(+)

diff --git a/gfx/2d/DrawTargetD2D1.cpp b/gfx/2d/DrawTargetD2D1.cpp
index 94a14e0b8d38..70188cbd60ff 100644
--- a/gfx/2d/DrawTargetD2D1.cpp
+++ b/gfx/2d/DrawTargetD2D1.cpp
@@ -57,6 +57,7 @@ DrawTargetD2D1::~DrawTargetD2D1()
   PopAllClips();
 
   if (mSnapshot) {
+    MutexAutoLock lock(*mSnapshotLock);
     // We may hold the only reference. MarkIndependent will clear mSnapshot;
     // keep the snapshot object alive so it doesn't get destroyed while
     // MarkIndependent is running.
@@ -90,6 +91,9 @@ DrawTargetD2D1::~DrawTargetD2D1()
 already_AddRefed<SourceSurface>
 DrawTargetD2D1::Snapshot()
 {
+  if (!mSnapshotLock) {
+    mSnapshotLock = make_shared<Mutex>("DrawTargetD2D1::mSnapshotLock");
+  }
   if (mSnapshot) {
     RefPtr<SourceSurface> snapshot(mSnapshot);
     return snapshot.forget();
@@ -1274,6 +1278,7 @@ void
 DrawTargetD2D1::MarkChanged()
 {
   if (mSnapshot) {
+    MutexAutoLock lock(*mSnapshotLock);
     if (mSnapshot->hasOneRef()) {
       // Just destroy it, since no-one else knows about it.
       mSnapshot = nullptr;
diff --git a/gfx/2d/DrawTargetD2D1.h b/gfx/2d/DrawTargetD2D1.h
index 0b98657d7f65..3199eb30294e 100644
--- a/gfx/2d/DrawTargetD2D1.h
+++ b/gfx/2d/DrawTargetD2D1.h
@@ -280,6 +280,7 @@ private:
   // The latest snapshot of this surface. This needs to be told when this
   // target is modified. We keep it alive as a cache.
   RefPtr<SourceSurfaceD2D1> mSnapshot;
+  std::shared_ptr<Mutex> mSnapshotLock;
   // A list of targets we need to flush when we're modified.
   TargetSet mDependentTargets;
   // A list of targets which have this object in their mDependentTargets set
diff --git a/gfx/2d/SourceSurfaceD2D1.cpp b/gfx/2d/SourceSurfaceD2D1.cpp
index d4b6bc6282bb..0a1238a0f4d2 100644
--- a/gfx/2d/SourceSurfaceD2D1.cpp
+++ b/gfx/2d/SourceSurfaceD2D1.cpp
@@ -23,6 +23,9 @@ SourceSurfaceD2D1::SourceSurfaceD2D1(ID2D1Image *aImage, ID2D1DeviceContext *aDC
 
   mFormat = aFormat;
   mSize = aSize;
+  if (aDT) {
+    mSnapshotLock = aDT->mSnapshotLock;
+  }
 }
 
 SourceSurfaceD2D1::~SourceSurfaceD2D1()
@@ -109,6 +112,9 @@ SourceSurfaceD2D1::EnsureRealizedBitmap()
 void
 SourceSurfaceD2D1::DrawTargetWillChange()
 {
+  MOZ_ASSERT(mSnapshotLock);
+  mSnapshotLock->AssertCurrentThreadOwns();
+
   // At this point in time this should always be true here.
   MOZ_ASSERT(mRealizedBitmap);
 
diff --git a/gfx/2d/SourceSurfaceD2D1.h b/gfx/2d/SourceSurfaceD2D1.h
index 7620637f8ee4..0d99a27ddea3 100644
--- a/gfx/2d/SourceSurfaceD2D1.h
+++ b/gfx/2d/SourceSurfaceD2D1.h
@@ -62,6 +62,7 @@ private:
   SurfaceFormat mFormat;
   IntSize mSize;
   DrawTargetD2D1* mDrawTarget;
+  std::shared_ptr<Mutex> mSnapshotLock;
 };
 
 class DataSourceSurfaceD2D1 : public DataSourceSurface