NativeMessageQueue: ensure nativeDestroy success

android_os_MessageQueue_nativeDestroy leaves a cyclic reference between its Looper instance and its NativeMessageQueue instance, resulting in a memory and fd leak.

Solution: break the cyclic reference with weak pointer wp<>.

Bug: 244478726

Signed-off-by: Jintao Zhu <zhu.jintao@gm.com>
Change-Id: Ic2a183b5cc7c05f9ade95a0602d425badd3d97b1

core/jni/android_os_MessageQueue.cpp

@@ -51,6 +51,21 @@ public:
 
     virtual int handleEvent(int fd, int events, void* data);
 
+    /**
+     * A simple proxy that holds a weak reference to a looper callback.
+     */
+    class WeakLooperCallback : public LooperCallback {
+    protected:
+        virtual ~WeakLooperCallback();
+
+    public:
+        WeakLooperCallback(const wp<LooperCallback>& callback);
+        virtual int handleEvent(int fd, int events, void* data);
+
+    private:
+        wp<LooperCallback> mCallback;
+    };
+
 private:
     JNIEnv* mPollEnv;
     jobject mPollObj;
@@ -131,7 +146,8 @@ void NativeMessageQueue::setFileDescriptorEvents(int fd, int events) {
         if (events & CALLBACK_EVENT_OUTPUT) {
             looperEvents |= Looper::EVENT_OUTPUT;
         }
-        mLooper->addFd(fd, Looper::POLL_CALLBACK, looperEvents, this,
+        mLooper->addFd(fd, Looper::POLL_CALLBACK, looperEvents,
+                sp<WeakLooperCallback>::make(this),
                 reinterpret_cast<void*>(events));
     } else {
         mLooper->removeFd(fd);
@@ -162,6 +178,24 @@ int NativeMessageQueue::handleEvent(int fd, int looperEvents, void* data) {
 }
 
 
+// --- NativeMessageQueue::WeakLooperCallback ---
+
+NativeMessageQueue::WeakLooperCallback::WeakLooperCallback(const wp<LooperCallback>& callback) :
+        mCallback(callback) {
+}
+
+NativeMessageQueue::WeakLooperCallback::~WeakLooperCallback() {
+}
+
+int NativeMessageQueue::WeakLooperCallback::handleEvent(int fd, int events, void* data) {
+    sp<LooperCallback> callback = mCallback.promote();
+    if (callback != nullptr) {
+        return callback->handleEvent(fd, events, data);
+    }
+    return 0;
+}
+
+
 // ----------------------------------------------------------------------------
 
 sp<MessageQueue> android_os_MessageQueue_getMessageQueue(JNIEnv* env, jobject messageQueueObj) {