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Commit 35d7cd47 authored by Gyumin Sim's avatar Gyumin Sim
Browse files

Avoid blocking outgoing binder call for setQueue 

There has been a blocking binder call out of system_server for
MediaSession#setQueue because ParceledListSlice internally creates
another binder on the caller side and calls the binder from callee
if the list is too large to fit in a single IPC transaction.

It introduces ParcelableListBinder to do multiple transactions in the
same direction, so that the binder call doesn't block system_server.

Bug: 147703076
Test: atest CtsMediaTestCases:android.media.cts.MediaSessionTest
Change-Id: I5623c20d615d25c88999d80615958d6cb6e51a77
parent 2503bf24

media/java/android/media/session/ISession.aidl

+2 −1
Original line number Diff line number Diff line
@@ -41,7 +41,8 @@ interface ISession { 
    // These commands are for the TransportPerformer

    void setMetadata(in MediaMetadata metadata, long duration, String metadataDescription);

    void setPlaybackState(in PlaybackState state);

    void setQueue(in ParceledListSlice queue);

    void resetQueue();

    IBinder getBinderForSetQueue();

    void setQueueTitle(CharSequence title);

    void setExtras(in Bundle extras);

    void setRatingType(int type);

media/java/android/media/session/MediaSession.java

+7 −2
Original line number Diff line number Diff line
@@ -25,7 +25,6 @@ import android.app.PendingIntent; 
import android.compat.annotation.UnsupportedAppUsage;

import android.content.Context;

import android.content.Intent;

import android.content.pm.ParceledListSlice;

import android.media.AudioAttributes;

import android.media.MediaDescription;

import android.media.MediaMetadata;
@@ -36,6 +35,7 @@ import android.net.Uri; 
import android.os.BadParcelableException;

import android.os.Bundle;

import android.os.Handler;

import android.os.IBinder;

import android.os.Looper;

import android.os.Message;

import android.os.Parcel;
@@ -491,7 +491,12 @@ public final class MediaSession { 
     */

    public void setQueue(@Nullable List<QueueItem> queue) {

        try {

            mBinder.setQueue(queue == null ? null : new ParceledListSlice(queue));

            if (queue == null) {

                mBinder.resetQueue();

            } else {

                IBinder binder = mBinder.getBinderForSetQueue();

                ParcelableListBinder.send(binder, queue);

            }

        } catch (RemoteException e) {

            Log.wtf("Dead object in setQueue.", e);

        }

media/java/android/media/session/ParcelableListBinder.java

0 → 100644
+131 −0
Original line number Diff line number Diff line 
/*

 * Copyright 2020 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */



package android.media.session;



import android.annotation.NonNull;

import android.os.Binder;

import android.os.IBinder;

import android.os.Parcel;

import android.os.Parcelable;

import android.os.RemoteException;



import com.android.internal.annotations.GuardedBy;



import java.util.ArrayList;

import java.util.List;

import java.util.function.Consumer;



/**

 * Binder to receive a list that has a large number of {@link Parcelable} items.

 *

 * It's similar to {@link android.content.pm.ParceledListSlice}, but transactions are performed in

 * the opposite direction.

 *

 * @param <T> the type of {@link Parcelable}

 * @hide

 */

public class ParcelableListBinder<T extends Parcelable> extends Binder {



    private static final int SUGGESTED_MAX_IPC_SIZE = IBinder.getSuggestedMaxIpcSizeBytes();



    private static final int END_OF_PARCEL = 0;

    private static final int ITEM_CONTINUED = 1;



    private final Consumer<List<T>> mConsumer;



    private final Object mLock = new Object();



    @GuardedBy("mLock")

    private final List<T> mList = new ArrayList<>();



    @GuardedBy("mLock")

    private int mCount;



    @GuardedBy("mLock")

    private boolean mConsumed;



    /**

     * Creates an instance.

     *

     * @param consumer a consumer that consumes the list received

     */

    public ParcelableListBinder(@NonNull Consumer<List<T>> consumer) {

        mConsumer = consumer;

    }



    @Override

    protected boolean onTransact(int code, Parcel data, Parcel reply, int flags)

            throws RemoteException {

        if (code != FIRST_CALL_TRANSACTION) {

            return super.onTransact(code, data, reply, flags);

        }

        List<T> listToBeConsumed;

        synchronized (mLock) {

            if (mConsumed) {

                return false;

            }

            int i = mList.size();

            if (i == 0) {

                mCount = data.readInt();

            }

            while (i < mCount && data.readInt() != END_OF_PARCEL) {

                mList.add(data.readParcelable(null));

                i++;

            }

            if (i >= mCount) {

                listToBeConsumed = mList;

                mConsumed = true;

            } else {

                listToBeConsumed = null;

            }

        }

        if (listToBeConsumed != null) {

            mConsumer.accept(listToBeConsumed);

        }

        return true;

    }



    /**

     * Sends a list of {@link Parcelable} to a binder.

     *

     * @param binder a binder interface backed by {@link ParcelableListBinder}

     * @param list a list to send

     */

    public static <T extends Parcelable> void send(@NonNull IBinder binder, @NonNull List<T> list)

            throws RemoteException {

        int count = list.size();

        int i = 0;

        while (i < count) {

            Parcel data = Parcel.obtain();

            Parcel reply = Parcel.obtain();

            if (i == 0) {

                data.writeInt(count);

            }

            while (i < count && data.dataSize() < SUGGESTED_MAX_IPC_SIZE) {

                data.writeInt(ITEM_CONTINUED);

                data.writeParcelable(list.get(i), 0);

                i++;

            }

            if (i < count) {

                data.writeInt(END_OF_PARCEL);

            }

            binder.transact(FIRST_CALL_TRANSACTION, data, reply, 0);

            reply.recycle();

            data.recycle();

        }

    }

}

services/core/java/com/android/server/media/MediaSessionRecord.java

+13 −2
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ import android.media.session.MediaController; 
import android.media.session.MediaController.PlaybackInfo;

import android.media.session.MediaSession;

import android.media.session.MediaSession.QueueItem;

import android.media.session.ParcelableListBinder;

import android.media.session.PlaybackState;

import android.net.Uri;

import android.os.Binder;
@@ -905,13 +906,23 @@ public class MediaSessionRecord implements IBinder.DeathRecipient, MediaSessionR 
        }



        @Override

        public void setQueue(ParceledListSlice queue) throws RemoteException {

        public void resetQueue() throws RemoteException {

            synchronized (mLock) {

                mQueue = queue == null ? null : (List<QueueItem>) queue.getList();

                mQueue = null;

            }

            mHandler.post(MessageHandler.MSG_UPDATE_QUEUE);

        }



        @Override

        public IBinder getBinderForSetQueue() throws RemoteException {

            return new ParcelableListBinder<QueueItem>((list) -> {

                synchronized (mLock) {

                    mQueue = list;

                }

                mHandler.post(MessageHandler.MSG_UPDATE_QUEUE);

            });

        }



        @Override

        public void setQueueTitle(CharSequence title) throws RemoteException {

            mQueueTitle = title;