From cb90c260fc84e6f2b5660b2d48be49859351ae3d Mon Sep 17 00:00:00 2001
From: Dichen Zhang <dichenzhang@google.com>
Date: Tue, 20 Nov 2018 11:34:34 -0800
Subject: Fix setAudioSessionId() Racing Issue

Pointed out by Wei: a later setAudioSessionId() could override the
previous one whose task has not completed.

Bug: 112549970
Test: MediaPlayer2Test
Change-Id: Ib5862d6dfd1ea4ddcbccb421906510ab4a3bae87
---
 media/java/android/media/MediaPlayer2.java | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/media/java/android/media/MediaPlayer2.java b/media/java/android/media/MediaPlayer2.java
index 548dc881d733..82889761b592 100644
--- a/media/java/android/media/MediaPlayer2.java
+++ b/media/java/android/media/MediaPlayer2.java
@@ -1763,10 +1763,13 @@ public class MediaPlayer2 implements AutoCloseable
      */
     // This is an asynchronous call.
     public Object setAudioSessionId(int sessionId) {
-        keepAudioSessionIdAlive(sessionId);
+        final AudioTrack dummyAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 44100,
+                    AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT, 2,
+                    AudioTrack.MODE_STATIC, sessionId);
         return addTask(new Task(CALL_COMPLETED_SET_AUDIO_SESSION_ID, false) {
             @Override
             void process() {
+                keepAudioSessionIdAlive(dummyAudioTrack);
                 native_setAudioSessionId(sessionId);
             }
         });
@@ -4621,4 +4624,17 @@ public class MediaPlayer2 implements AutoCloseable
                     AudioTrack.MODE_STATIC, sessionId);
         }
     }
+
+    private void keepAudioSessionIdAlive(AudioTrack at) {
+        synchronized (mSessionIdLock) {
+            if (mDummyAudioTrack != null) {
+                if (mDummyAudioTrack.getAudioSessionId() == at.getAudioSessionId()) {
+                    at.release();
+                    return;
+                }
+                mDummyAudioTrack.release();
+            }
+            mDummyAudioTrack = at;
+        }
+    }
 }
-- 
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