Merge "Revert "Prevent onImageAvailable from being called on stale listeners""

media/java/android/media/ImageReader.java

@@ -43,7 +43,6 @@ import java.util.Objects;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.locks.StampedLock;
 
 /**
  * <p>The ImageReader class allows direct application access to image data
@@ -676,8 +675,7 @@ public class ImageReader implements AutoCloseable {
      *            If no handler specified and the calling thread has no looper.
      */
     public void setOnImageAvailableListener(OnImageAvailableListener listener, Handler handler) {
-        long writeStamp = mListenerLock.writeLock();
-        try {
+        synchronized (mListenerLock) {
             if (listener != null) {
                 Looper looper = handler != null ? handler.getLooper() : Looper.myLooper();
                 if (looper == null) {
@@ -693,8 +691,6 @@ public class ImageReader implements AutoCloseable {
                 mListenerExecutor = null;
             }
             mListener = listener;
-        } finally {
-            mListenerLock.unlockWrite(writeStamp);
         }
     }
 
@@ -717,12 +713,9 @@ public class ImageReader implements AutoCloseable {
             throw new IllegalArgumentException("executor must not be null");
         }
 
-        long writeStamp = mListenerLock.writeLock();
-        try {
+        synchronized (mListenerLock) {
             mListenerExecutor = executor;
             mListener = listener;
-        } finally {
-            mListenerLock.unlockWrite(writeStamp);
         }
     }
 
@@ -738,8 +731,6 @@ public class ImageReader implements AutoCloseable {
         /**
          * Callback that is called when a new image is available from ImageReader.
          *
-         * This callback must not modify or close the passed {@code reader}.
-         *
          * @param reader the ImageReader the callback is associated with.
          * @see ImageReader
          * @see Image
@@ -898,41 +889,28 @@ public class ImageReader implements AutoCloseable {
             return;
         }
 
-        synchronized (ir.mCloseLock) {
-            if (!ir.mIsReaderValid) {
-                // It's dangerous to fire onImageAvailable() callback when the ImageReader
-                // is being closed, as application could acquire next image in the
-                // onImageAvailable() callback.
-                return;
-            }
-        }
-
         final Executor executor;
-        final long readStamp = ir.mListenerLock.readLock();
-        try {
+        final OnImageAvailableListener listener;
+        synchronized (ir.mListenerLock) {
             executor = ir.mListenerExecutor;
-            if (executor == null) {
-                return;
-            }
-        } finally {
-            ir.mListenerLock.unlockRead(readStamp);
+            listener = ir.mListener;
+        }
+        final boolean isReaderValid;
+        synchronized (ir.mCloseLock) {
+            isReaderValid = ir.mIsReaderValid;
         }
 
-        executor.execute(() -> {
-            // Acquire readlock to ensure that the ImageReader does not change its
-            // state while a listener is actively processing.
-            final long rStamp = ir.mListenerLock.readLock();
-            try {
-                // Fire onImageAvailable of the latest non-null listener
-                // This ensures that if the listener changes while messages are in queue, the
-                // in-flight messages will call onImageAvailable of the new listener instead
-                if (ir.mListener != null) {
-                    ir.mListener.onImageAvailable(ir);
+        // It's dangerous to fire onImageAvailable() callback when the ImageReader
+        // is being closed, as application could acquire next image in the
+        // onImageAvailable() callback.
+        if (executor != null && listener != null && isReaderValid) {
+            executor.execute(new Runnable() {
+                @Override
+                public void run() {
+                    listener.onImageAvailable(ir);
                 }
-            } finally {
-                ir.mListenerLock.unlockRead(rStamp);
-            }
-        });
+            });
+        }
     }
 
     /**
@@ -1092,7 +1070,7 @@ public class ImageReader implements AutoCloseable {
     private Surface mSurface;
     private int mEstimatedNativeAllocBytes;
 
-    private final StampedLock mListenerLock = new StampedLock();
+    private final Object mListenerLock = new Object();
     private final Object mCloseLock = new Object();
     private boolean mIsReaderValid = false;
     private OnImageAvailableListener mListener;