Bug 860075 - Avoid duplicate BT signal observer registration from child process. r=echou, r=gyeh

dom/bluetooth/BluetoothService.cpp

@@ -378,6 +378,10 @@ BluetoothService::UnregisterBluetoothSignalHandler(
   BluetoothSignalObserverList* ol;
   if (mBluetoothSignalObserverTable.Get(aNodeName, &ol)) {
     ol->RemoveObserver(aHandler);
+    // We shouldn't have duplicate instances in the ObserverList, but there's
+    // no appropriate way to do duplication check while registering, so
+    // assertions are added here.
+    MOZ_ASSERT(!ol->RemoveObserver(aHandler));
     if (ol->Length() == 0) {
       mBluetoothSignalObserverTable.Remove(aNodeName);
     }
@@ -392,7 +396,12 @@ RemoveAllSignalHandlers(const nsAString& aKey,
                         nsAutoPtr<BluetoothSignalObserverList>& aData,
                         void* aUserArg)
 {
-  aData->RemoveObserver(static_cast<BluetoothSignalObserver*>(aUserArg));
+  BluetoothSignalObserver* handler = static_cast<BluetoothSignalObserver*>(aUserArg);
+  aData->RemoveObserver(handler);
+  // We shouldn't have duplicate instances in the ObserverList, but there's
+  // no appropriate way to do duplication check while registering, so
+  // assertions are added here.
+  MOZ_ASSERT(!aData->RemoveObserver(handler));
   return aData->Length() ? PL_DHASH_NEXT : PL_DHASH_REMOVE;
 }
 

dom/bluetooth/ipc/BluetoothServiceChildProcess.cpp

@@ -77,7 +77,7 @@ BluetoothServiceChildProcess::RegisterBluetoothSignalHandler(
                                               const nsAString& aNodeName,
                                               BluetoothSignalObserver* aHandler)
 {
-  if (gBluetoothChild) {
+  if (gBluetoothChild && !IsSignalRegistered(aNodeName)) {
     gBluetoothChild->SendRegisterSignalHandler(nsString(aNodeName));
   }
   BluetoothService::RegisterBluetoothSignalHandler(aNodeName, aHandler);
@@ -88,10 +88,10 @@ BluetoothServiceChildProcess::UnregisterBluetoothSignalHandler(
                                               const nsAString& aNodeName,
                                               BluetoothSignalObserver* aHandler)
 {
-  if (gBluetoothChild) {
+  BluetoothService::UnregisterBluetoothSignalHandler(aNodeName, aHandler);
+  if (gBluetoothChild && !IsSignalRegistered(aNodeName)) {
     gBluetoothChild->SendUnregisterSignalHandler(nsString(aNodeName));
   }
-  BluetoothService::UnregisterBluetoothSignalHandler(aNodeName, aHandler);
 }
 
 nsresult

dom/bluetooth/ipc/BluetoothServiceChildProcess.h

@@ -174,6 +174,11 @@ private:
   // This method should never be called from the child.
   virtual nsresult
   PrepareAdapterInternal() MOZ_OVERRIDE;
+
+  bool
+  IsSignalRegistered(const nsAString& aNodeName) {
+    return !!mBluetoothSignalObserverTable.Get(aNodeName);
+  }
 };
 
 END_BLUETOOTH_NAMESPACE