Bug 1514417 - Add mutex to avoid VR shmem be deadlock when VRService and VRSubmitFrame threads are accessing it. r=kip

MozReview-Commit-ID: 7uXdypiXTUH

Differential Revision: https://phabricator.services.mozilla.com/D17581

--HG--
extra : moz-landing-system : lando

gfx/vr/gfxVRExternal.cpp

@@ -426,8 +426,8 @@ VRSystemManagerExternal::VRSystemManagerExternal(
     VRExternalShmem* aAPIShmem /* = nullptr*/)
     : mExternalShmem(aAPIShmem)
 #if !defined(MOZ_WIDGET_ANDROID)
-      ,
-      mSameProcess(aAPIShmem != nullptr)
+    , mMutex("VRSystemManagerExternal::mMutex")
+    , mSameProcess(aAPIShmem != nullptr)
 #endif
 {
 #if defined(XP_MACOSX)
@@ -844,6 +844,10 @@ void VRSystemManagerExternal::PushState(VRBrowserState* aBrowserState,
       pthread_mutex_unlock((pthread_mutex_t*)&(mExternalShmem->browserMutex));
     }
 #else
+    // We need this MutexAutoLock to avoid mAPIShmem happens deadlock issue
+    // when both of VRService and VRSubmitFrame threads are writing/reading
+    // it from the memory.
+    MutexAutoLock lock(mMutex);
     mExternalShmem->browserGenerationA++;
     memcpy((void*)&(mExternalShmem->browserState), (void*)aBrowserState,
            sizeof(VRBrowserState));

gfx/vr/gfxVRExternal.h

@@ -134,6 +134,7 @@ class VRSystemManagerExternal : public VRSystemManager {
 
   volatile VRExternalShmem* mExternalShmem;
 #if !defined(MOZ_WIDGET_ANDROID)
+  Mutex mMutex;
   bool mSameProcess;
 #endif
   TimeStamp mEarliestRestartTime;

gfx/vr/service/VRService.cpp

@@ -68,6 +68,9 @@ VRService::VRService()
       mTargetShmemFile(0),
       mLastHapticState{},
       mFrameStartTime{},
+#if !defined(MOZ_WIDGET_ANDROID)
+      mMutex("VRService::mMutex"),
+#endif
       mVRProcessEnabled(gfxPrefs::VRProcessEnabled()) {
   // When we have the VR process, we map the memory
   // of mAPIShmem from GPU process.
@@ -456,6 +459,10 @@ void VRService::PullState(mozilla::gfx::VRBrowserState& aState) {
     pthread_mutex_unlock((pthread_mutex_t*)&(mExternalShmem->browserMutex));
   }
 #else
+  // We need this MutexAutoLock to avoid mAPIShmem happens deadlock issue
+  // when both of VRService and VRSubmitFrame threads are writing/reading
+  // it from the memory.
+  MutexAutoLock lock(mMutex);
   VRExternalShmem tmp;
   if (mAPIShmem->browserGenerationA != mBrowserGeneration) {
     memcpy(&tmp, mAPIShmem, sizeof(VRExternalShmem));

gfx/vr/service/VRService.h

@@ -63,6 +63,9 @@ class VRService {
   base::ProcessHandle mTargetShmemFile;
   VRHapticState mLastHapticState[kVRHapticsMaxCount];
   TimeStamp mFrameStartTime[kVRFrameTimingHistoryDepth];
+#if !defined(MOZ_WIDGET_ANDROID)
+  Mutex mMutex;
+#endif
   // We store the value of gfxPrefs::VRProcessEnabled() in mVRProcessEnabled.
   // This allows us to read the value in the VRService destructor, after
   // gfxPrefs has been shut down.  We should investigate why gfxPrefs