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Commit eb039c3f authored by Avichal Rakesh's avatar Avichal Rakesh
Browse files

ImageWriter: remove mCloseLock guard from queue and dequeue operations 

mCloseLock currently guards #queueInputImage, #dequeueInputImage, and
#postEventFromNative. However, there have been cases reported where a
contention between #postEventFromNative and #queueInputImage would lead
to a deadlock. This CL removes the mCloseLock guard from #queueInputImage
and #dequeInputImage as the native implementations are already
synchronized on `this` and there are no reported bugs from race
conditions in those two functions.

It also drops the mCloseLock guard from #postEventFromNative and moves
the responsibility of ensuring ImageWriter is valid to the
ListenerHandler. This ensures that mCloseLock is never in contention
in the JNI thread that calls #postEventFromNative.

#close() is still protected by mCloseLock to prevent multiple
simultaneous closes.

Bug: 263395157
Test: Existing ImageWriter tests pass
      Ran the sequence that led to deadlock 30 times without a single
      deadlock.
Change-Id: I5b0d367cce7df9401386e5a53c5e9b539d8c1f40
parent da209b10

media/java/android/media/ImageWriter.java

+52 −58
Original line number Diff line number Diff line
@@ -452,7 +452,6 @@ public class ImageWriter implements AutoCloseable { 
     * @see Image#close

     */

    public Image dequeueInputImage() {

        synchronized (mCloseLock) {

        if (mDequeuedImages.size() >= mMaxImages) {

            throw new IllegalStateException(

                    "Already dequeued max number of Images " + mMaxImages);
@@ -463,7 +462,6 @@ public class ImageWriter implements AutoCloseable { 
        newImage.mIsImageValid = true;

        return newImage;

    }

    }



    /**

     * <p>
@@ -521,7 +519,6 @@ public class ImageWriter implements AutoCloseable { 
            throw new IllegalArgumentException("image shouldn't be null");

        }



        synchronized (mCloseLock) {

        boolean ownedByMe = isImageOwnedByMe(image);

        if (ownedByMe && !(((WriterSurfaceImage) image).mIsImageValid)) {

            throw new IllegalStateException("Image from ImageWriter is invalid");
@@ -568,7 +565,6 @@ public class ImageWriter implements AutoCloseable { 
            wi.mIsImageValid = false;

        }

    }

    }



    /**

     * Get the ImageWriter format.
@@ -702,11 +698,11 @@ public class ImageWriter implements AutoCloseable { 
     */

    @Override

    public void close() {

        setOnImageReleasedListener(null, null);

        synchronized (mCloseLock) {

            if (!mIsWriterValid) {

                return;

            }

            setOnImageReleasedListener(null, null);

            for (Image image : mDequeuedImages) {

                image.close();

            }
@@ -836,14 +832,12 @@ public class ImageWriter implements AutoCloseable { 
        }



        final Handler handler;

        final boolean isWriterValid;

        synchronized (iw.mListenerLock) {

            handler = iw.mListenerHandler;

        }

        synchronized (iw.mCloseLock) {

            isWriterValid = iw.mIsWriterValid;

        }

        if (handler != null && isWriterValid) {



        if (handler != null) {

            // The ListenerHandler will take care of ensuring that the parent ImageWriter is valid

            handler.sendEmptyMessage(0);

        }

    }