--- a/dom/media/MediaFormatReader.cpp
+++ b/dom/media/MediaFormatReader.cpp
@@ -86,50 +86,54 @@ public:
                      MediaDataDecoderID aMediaDataDecoderID,
                      const TimeStamp& aGPUCrashTime,
                      const TimeStamp& aErrorNotifiedTime)
   {
     MOZ_ASSERT(aMediaDecoderOwnerID);
     MOZ_ASSERT(aMediaDataDecoderID);
     MOZ_ASSERT(!aGPUCrashTime.IsNull());
     MOZ_ASSERT(!aErrorNotifiedTime.IsNull());
+    StaticMutexAutoLock lock(sGPUCrashMapMutex);
     auto it = sGPUCrashDataMap.find(aMediaDecoderOwnerID);
     if (it == sGPUCrashDataMap.end()) {
       sGPUCrashDataMap.insert(std::make_pair(aMediaDecoderOwnerID,
                                              GPUCrashData(aMediaDataDecoderID,
                                                           aGPUCrashTime,
                                                           aErrorNotifiedTime)));
     }
   }
 
   static void
   ReportTelemetry(MediaDecoderOwnerID aMediaDecoderOwnerID,
                   MediaDataDecoderID aMediaDataDecoderID)
   {
     MOZ_ASSERT(aMediaDecoderOwnerID);
     MOZ_ASSERT(aMediaDataDecoderID);
+    StaticMutexAutoLock lock(sGPUCrashMapMutex);
     auto it = sGPUCrashDataMap.find(aMediaDecoderOwnerID);
     if (it != sGPUCrashDataMap.end() &&
         it->second.mMediaDataDecoderID != aMediaDataDecoderID) {
       Telemetry::AccumulateTimeDelta(
         Telemetry::VIDEO_HW_DECODER_CRASH_RECOVERY_TIME_SINCE_GPU_CRASHED_MS,
         it->second.mGPUCrashTime);
       Telemetry::AccumulateTimeDelta(
         Telemetry::VIDEO_HW_DECODER_CRASH_RECOVERY_TIME_SINCE_MFR_NOTIFIED_MS,
         it->second.mErrorNotifiedTime);
       sGPUCrashDataMap.erase(aMediaDecoderOwnerID);
     }
   }
 
 private:
   static std::map<MediaDecoderOwnerID, GPUCrashData> sGPUCrashDataMap;
+  static StaticMutex sGPUCrashMapMutex;
 };
 
 std::map<MediaDecoderOwnerID, GPUProcessCrashTelemetryLogger::GPUCrashData>
 GPUProcessCrashTelemetryLogger::sGPUCrashDataMap;
+StaticMutex GPUProcessCrashTelemetryLogger::sGPUCrashMapMutex;
 
 /**
  * This is a singleton which controls the number of decoders that can be
  * created concurrently. Before calling PDMFactory::CreateDecoder(), Alloc()
  * must be called to get a token object as a permission to create a decoder.
  * The token should stay alive until Shutdown() is called on the decoder.
  * The destructor of the token will restore the decoder count so it is available
  * for next calls of Alloc().