Fix thread leak due to race condition

main/src/main/java/com/sedmelluq/discord/lavaplayer/player/DefaultAudioPlayer.java

@@ -241,9 +241,12 @@ public boolean provide(MutableAudioFrame targetFrame, long timeout, TimeUnit uni
     private void handleTerminator(InternalAudioTrack track) {
         synchronized (trackSwitchLock) {
             if (activeTrack == track) {
-                activeTrack = null;
-
-                dispatchEvent(new TrackEndEvent(this, track, track.getActiveExecutor().failedBeforeLoad() ? LOAD_FAILED : FINISHED));
+                try {
+                    activeTrack = null;
+                    dispatchEvent(new TrackEndEvent(this, track, track.getActiveExecutor().failedBeforeLoad() ? LOAD_FAILED : FINISHED));
+                } finally {
+                    track.stop();
+                }
             }
         }
     }

main/src/main/java/com/sedmelluq/discord/lavaplayer/track/BaseAudioTrack.java

@@ -11,14 +11,15 @@
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.AtomicReference;
 
 /**
  * Abstract base for all audio tracks with an executor
  */
 public abstract class BaseAudioTrack implements InternalAudioTrack {
     private final PrimordialAudioTrackExecutor initialExecutor;
     private final AtomicBoolean executorAssigned;
-    private volatile AudioTrackExecutor activeExecutor;
+    private final AtomicReference<AudioTrackExecutor> activeExecutor;
     protected final AudioTrackInfo trackInfo;
     protected final AtomicLong accurateDuration;
     private volatile Object userData;
@@ -29,7 +30,7 @@ public abstract class BaseAudioTrack implements InternalAudioTrack {
     public BaseAudioTrack(AudioTrackInfo trackInfo) {
         this.initialExecutor = new PrimordialAudioTrackExecutor(trackInfo);
         this.executorAssigned = new AtomicBoolean();
-        this.activeExecutor = null;
+        this.activeExecutor = new AtomicReference<>();
         this.trackInfo = trackInfo;
         this.accurateDuration = new AtomicLong();
     }
@@ -40,21 +41,25 @@ public void assignExecutor(AudioTrackExecutor executor, boolean applyPrimordialS
             if (applyPrimordialState) {
                 initialExecutor.applyStateToExecutor(executor);
             }
-            activeExecutor = executor;
+            activeExecutor.set(executor);
         } else {
             throw new IllegalStateException("Cannot play the same instance of a track twice, use track.makeClone().");
         }
     }
 
     @Override
     public AudioTrackExecutor getActiveExecutor() {
-        AudioTrackExecutor executor = activeExecutor;
+        AudioTrackExecutor executor = activeExecutor.get();
         return executor != null ? executor : initialExecutor;
     }
 
     @Override
     public void stop() {
-        getActiveExecutor().stop();
+        AudioTrackExecutor executor = activeExecutor.getAndSet(null);
+        if (executor == null) return;
+
+        initialExecutor.setPosition(executor.getPosition());
+        executor.stop();
     }
 
     @Override

main/src/main/java/com/sedmelluq/discord/lavaplayer/track/playback/AudioTrackExecutor.java

@@ -21,7 +21,8 @@ public interface AudioTrackExecutor extends AudioFrameProvider {
     void execute(TrackStateListener listener);
 
     /**
-     * Stop playing the track, terminating the thread that is filling the frame buffer.
+     * Stop playing the track, terminating the thread that is filling the frame buffer. Subsequent playback requires
+     *  a new executor.
      */
     void stop();
 

main/src/main/java/com/sedmelluq/discord/lavaplayer/track/playback/LocalAudioTrackExecutor.java

@@ -33,7 +33,7 @@ public class LocalAudioTrackExecutor implements AudioTrackExecutor {
     private final boolean useSeekGhosting;
     private final AudioFrameBuffer frameBuffer;
     private final AtomicReference<Thread> playingThread = new AtomicReference<>();
-    private final AtomicBoolean queuedStop = new AtomicBoolean(false);
+    private final AtomicBoolean disposedOf = new AtomicBoolean(false);
     private final AtomicLong queuedSeek = new AtomicLong(-1);
     private final AtomicLong lastFrameTimecode = new AtomicLong(0);
     private final AtomicReference<AudioTrackState> state = new AtomicReference<>(AudioTrackState.INACTIVE);
@@ -56,7 +56,7 @@ public LocalAudioTrackExecutor(InternalAudioTrack audioTrack, AudioConfiguration
 
         this.audioTrack = audioTrack;
         AudioDataFormat currentFormat = configuration.getOutputFormat();
-        this.frameBuffer = configuration.getFrameBufferFactory().create(bufferDuration, currentFormat, queuedStop);
+        this.frameBuffer = configuration.getFrameBufferFactory().create(bufferDuration, currentFormat, disposedOf);
         this.processingContext = new AudioProcessingContext(configuration, frameBuffer, playerOptions, currentFormat);
         this.useSeekGhosting = useSeekGhosting;
     }
@@ -92,7 +92,15 @@ public void execute(TrackStateListener listener) {
             log.debug("Cleared a stray interrupt.");
         }
 
-        if (playingThread.compareAndSet(null, Thread.currentThread())) {
+        synchronized (actionSynchronizer) {
+            if (disposedOf.get()) {
+                log.warn("Attempt to execute executor that has been disposed of");
+                return;
+            }
+        }
+
+        boolean wasUpdated = playingThread.compareAndSet(null, Thread.currentThread());
+        if (wasUpdated) {
             log.debug("Starting to play track {} locally with listener {}", audioTrack.getInfo().identifier, listener);
 
             state.set(AudioTrackState.LOADING);
@@ -105,7 +113,7 @@ public void execute(TrackStateListener listener) {
                 // Temporarily clear the interrupted status so it would not disrupt listener methods.
                 interrupt = findInterrupt(e);
 
-                if (interrupt != null && checkStopped()) {
+                if (interrupt != null) {
                     log.debug("Track {} was interrupted outside of execution loop.", audioTrack.getIdentifier());
                 } else {
                     frameBuffer.setTerminateOnEmpty();
@@ -140,31 +148,18 @@ public void execute(TrackStateListener listener) {
     @Override
     public void stop() {
         synchronized (actionSynchronizer) {
+            disposedOf.set(true);
             Thread thread = playingThread.get();
 
             if (thread != null) {
                 log.debug("Requesting stop for track {}", audioTrack.getIdentifier());
-
-                queuedStop.compareAndSet(false, true);
                 thread.interrupt();
             } else {
                 log.debug("Tried to stop track {} which is not playing.", audioTrack.getIdentifier());
             }
         }
     }
 
-    /**
-     * @return True if the track has been scheduled to stop and then clears the scheduled stop bit.
-     */
-    public boolean checkStopped() {
-        if (queuedStop.compareAndSet(true, false)) {
-            state.set(AudioTrackState.STOPPING);
-            return true;
-        }
-
-        return false;
-    }
-
     /**
      * Wait until all the frames from the frame buffer have been consumed. Keeps the buffering thread alive to keep it
      * interruptible for seeking until buffer is empty.
@@ -176,24 +171,6 @@ public void waitOnEnd() throws InterruptedException {
         frameBuffer.waitForTermination();
     }
 
-    /**
-     * Interrupt the buffering thread, either stop or seek should have been set beforehand.
-     *
-     * @return True if there was a thread to interrupt.
-     */
-    public boolean interrupt() {
-        synchronized (actionSynchronizer) {
-            Thread thread = playingThread.get();
-
-            if (thread != null) {
-                thread.interrupt();
-                return true;
-            }
-
-            return false;
-        }
-    }
-
     @Override
     public long getPosition() {
         long seek = queuedSeek.get();
@@ -336,7 +313,7 @@ private void interruptForSeek() {
     private boolean handlePlaybackInterrupt(InterruptedException interruption, SeekExecutor seekExecutor) {
         Thread.interrupted();
 
-        if (checkStopped()) {
+        if (disposedOf.get()) {
             markerTracker.trigger(STOPPED);
             return false;
         }
@@ -345,7 +322,7 @@ private boolean handlePlaybackInterrupt(InterruptedException interruption, SeekE
 
         if (seekResult != SeekResult.NO_SEEK) {
             // Double-check, might have received a stop request while seeking
-            if (checkStopped()) {
+            if (disposedOf.get()) {
                 markerTracker.trigger(STOPPED);
                 return false;
             } else {