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Commit 1b6cc77f authored by lijilou's avatar lijilou
Browse files

Remove the mRemoteTaskStackListeners lock. 

RemoteCallbackList sychronizes on RemoteCallbackList.mInterfaces for the following methods:

RemoteCallbackList.register
RemoteCallbackList.unregister
RemoteCallbackList.beginBroadcast (creates a copy-on-write of the list, also under mLock)
RemoteCallbackList.finishBroadcast (clears copy-on-write of the list, also under mLock)

The last two are done under mLock. The following method doesn't need to hold RemoteCallbackList.mInterfaces because it only accesses an immutable copy of the list, not the modifiable list.

RemoteCallbackList.getBroadcastItem (reads copy-on-write array, without mLock)

The only requirement to be thread-safe with RemoteCallbackList seems to be to beginBroadcast+getBroadcastItem+finishBroadcast all in the same handler thread, so we do not need another lock to protect.

Bug: none
Flag: EXEMPT minor optimization
Change-Id: Ia40a1570daa48945c0b82d7bc5d8d7960c16f6f7
parent 23ba0666

services/core/java/com/android/server/wm/TaskChangeNotificationController.java

+9 −16
Original line number Diff line number Diff line
@@ -72,7 +72,6 @@ class TaskChangeNotificationController { 
    private final Handler mHandler;



    // Task stack change listeners in a remote process.

    @GuardedBy("mRemoteTaskStackListeners")

    private final RemoteCallbackList<ITaskStackListener> mRemoteTaskStackListeners =

            new RemoteCallbackList<>();
@@ -311,11 +310,9 @@ class TaskChangeNotificationController { 
                }

            }

        } else if (listener != null) {

            synchronized (mRemoteTaskStackListeners) {

            mRemoteTaskStackListeners.register(listener);

        }

    }

    }



    public void unregisterTaskStackListener(ITaskStackListener listener) {

        if (listener instanceof Binder) {
@@ -323,14 +320,11 @@ class TaskChangeNotificationController { 
                mLocalTaskStackListeners.remove(listener);

            }

        } else if (listener != null) {

            synchronized (mRemoteTaskStackListeners) {

            mRemoteTaskStackListeners.unregister(listener);

        }

    }

    }



    private void forAllRemoteListeners(TaskStackConsumer callback, Message message) {

        synchronized (mRemoteTaskStackListeners) {

        for (int i = mRemoteTaskStackListeners.beginBroadcast() - 1; i >= 0; i--) {

            try {

                // Make a one-way callback to the listener
@@ -341,7 +335,6 @@ class TaskChangeNotificationController { 
        }

        mRemoteTaskStackListeners.finishBroadcast();

    }

    }



    private void forAllLocalListeners(TaskStackConsumer callback, Message message) {

        synchronized (mLocalTaskStackListeners) {