#1802 Traffic channels stuck in TEARDOWN. Resolves: (#1829)

1. Tuner channel processing runnables were being interruptibly shutdown, preventing the channel from clearing any owned locks (ie DMRTrafficChannelManager) causing thread deadlock and eventually causing out of memory situation or tying up all threads in the thread pool to the point that the application stopped processing any data.

2. DMR Traffic Channel Manager was erroneously processing non-owned traffic channel events.

Co-authored-by: Dennis Sheirer <[email protected]>

Author: DSheirer

src/main/java/io/github/dsheirer/channel/state/AbstractDecoderState.java

@@ -1,23 +1,20 @@
 /*
+ * *****************************************************************************
+ * Copyright (C) 2014-2024 Dennis Sheirer
  *
- *  * ******************************************************************************
- *  * Copyright (C) 2014-2019 Dennis Sheirer
- *  *
- *  * This program is free software: you can redistribute it and/or modify
- *  * it under the terms of the GNU General Public License as published by
- *  * the Free Software Foundation, either version 3 of the License, or
- *  * (at your option) any later version.
- *  *
- *  * This program is distributed in the hope that it will be useful,
- *  * but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  * GNU General Public License for more details.
- *  *
- *  * You should have received a copy of the GNU General Public License
- *  * along with this program.  If not, see <http://www.gnu.org/licenses/>
- *  * *****************************************************************************
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
  *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
  *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * ****************************************************************************
  */
 
 package io.github.dsheirer.channel.state;
@@ -47,9 +44,37 @@ public abstract class AbstractDecoderState extends Module implements ActivitySum
     protected Broadcaster<IDecodeEvent> mDecodeEventBroadcaster = new Broadcaster<>();
     protected Listener<DecoderStateEvent> mDecoderStateListener;
     private DecoderStateEventListener mDecoderStateEventListener = new DecoderStateEventListener();
+    private boolean mRunning;
 
     public abstract DecoderType getDecoderType();
 
+    /**
+     * Implements module start and sets the mRunning flag to true so that messages can be processed.
+     */
+    @Override
+    public void start()
+    {
+        mRunning = true;
+    }
+
+    /**
+     * Implements the module stop and sets the mRunning flag to false to stop message processing
+     */
+    @Override
+    public void stop()
+    {
+        mRunning = false;
+    }
+
+    /**
+     * Indicates if this module is running and can process/pass messages down to sub-class implementations.
+     * @return true if running
+     */
+    public boolean isRunning()
+    {
+        return mRunning;
+    }
+
     /**
      * Provides subclass reference to the decode event broadcaster
      */
@@ -145,4 +170,22 @@ public void receive(DecoderStateEvent event)
         }
     }
 
+    /**
+     * Message listener that only passes messages while we're running.  This is important because each of the decoders
+     * can process blocks of samples and that can result in additional messages being generated even after shutdown
+     * and so we shut off the processing of decoded messages when we're commanded to stop.  The sample processing thread
+     * cannot be shutdown or forcefully interrupted because downstream decoder and channel states may have acquired
+     * locks that have to be properly released.
+     */
+    private class MessageListener implements Listener<IMessage>
+    {
+        @Override
+        public void receive(IMessage message)
+        {
+            if(isRunning())
+            {
+                receive(message);
+            }
+        }
+    }
 }

src/main/java/io/github/dsheirer/channel/state/AlwaysUnsquelchedDecoderState.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2022 Dennis Sheirer
+ * Copyright (C) 2014-2024 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -54,6 +54,7 @@ public DecoderState()
     @Override
     public void start()
     {
+        super.start();
         //Broadcast the existing identifiers (as add events) so that they can be received by external listeners
         mIdentifierCollection.broadcastIdentifiers();
     }

src/main/java/io/github/dsheirer/channel/state/DecoderState.java

@@ -636,6 +636,8 @@ private void stopProcessing(Channel channel) throws ChannelException
                 processingChain.removeFrequencyChangeListener(channel);
                 channel.resetFrequencyCorrection();
 
+                //Notify all processing chains that this channel is shutting down so that if this is a traffic channel,
+                //the owning parent channel's traffic channel manager can cleanup it's accounting.
                 mChannelEventBroadcaster.broadcast(new ChannelEvent(channel, ChannelEvent.Event.NOTIFICATION_PROCESSING_STOP));
                 mChannelEventBroadcaster.removeListener(processingChain);
 

src/main/java/io/github/dsheirer/controller/channel/ChannelProcessingManager.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2023 Dennis Sheirer
+ * Copyright (C) 2014-2024 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -145,11 +145,10 @@ private void endCallEvent()
     @Override
     public void start()
     {
+        super.start();
         getIdentifierCollection().update(getChannelNameIdentifier());
     }
 
-    @Override
-    public void stop() {}
     @Override
     public void init() {}
     @Override

src/main/java/io/github/dsheirer/module/decode/analog/AnalogDecoderState.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2023 Dennis Sheirer
+ * Copyright (C) 2014-2024 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -115,9 +115,4 @@ public String getActivitySummary()
     public void init()
     {
     }
-
-    @Override
-    public void stop()
-    {
-    }
 }

src/main/java/io/github/dsheirer/module/decode/dcs/DCSDecoderState.java

@@ -1472,6 +1472,8 @@ public void receiveDecoderStateEvent(DecoderStateEvent event)
     @Override
     public void start()
     {
+        super.start();
+
         //Change the default (45-second) traffic channel timeout to 1 second
         if(mChannel.isTrafficChannel())
         {
@@ -1483,9 +1485,4 @@ public void start()
     public void init()
     {
     }
-
-    @Override
-    public void stop()
-    {
-    }
 }

src/main/java/io/github/dsheirer/module/decode/dmr/DMRDecoderState.java

@@ -201,6 +201,9 @@ private void createTrafficChannels()
             }
 
             mAvailableTrafficChannels.addAll(trafficChannelList);
+
+            //Keep track of the complete list so that we can check channel events to determine if the channel event
+            //is for a traffic channel owned by this traffic channel manager.
             mAllocatedTrafficChannels = Collections.unmodifiableList(trafficChannelList);
         }
     }
@@ -795,15 +798,19 @@ else if(!decodeEvent2.getDetails().endsWith(CHANNEL_START_REJECTED))
         }
 
         /**
-         * Process traffic channel processing stop or processing start rejected events.
+         /**
+         * Process channel events from the ChannelProcessingManager to account for owned child traffic channels.
+         * Note: this method sees events for ALL channels and not just DMR channels managed by this instance.
+         *
          * @param channelEvent to process
          */
         @Override
         public synchronized void receive(ChannelEvent channelEvent)
         {
             Channel channel = channelEvent.getChannel();
 
-            if(channel.isTrafficChannel())
+            //Only process the event if it's one of the traffic channels managed by this instance.
+            if(mAllocatedTrafficChannels.contains(channel))
             {
                 switch(channelEvent.getEvent())
                 {

src/main/java/io/github/dsheirer/module/decode/dmr/DMRTrafficChannelManager.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2023 Dennis Sheirer
+ * Copyright (C) 2014-2024 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -53,20 +53,7 @@ public DecoderType getDecoderType()
     }
 
     @Override
-    public void start()
-    {
-    }
-
-    @Override
-    public void stop()
-    {
-    }
-
-    @Override
-    public void init()
-    {
-
-    }
+    public void init() {}
 
     @Override
     public void receive(IMessage message)

src/main/java/io/github/dsheirer/module/decode/fleetsync2/Fleetsync2DecoderState.java

@@ -1,6 +1,6 @@
 /*
  * *****************************************************************************
- * Copyright (C) 2014-2023 Dennis Sheirer
+ * Copyright (C) 2014-2024 Dennis Sheirer
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -150,20 +150,5 @@ public void reset()
     }
 
     @Override
-    public void start()
-    {
-
-    }
-
-    @Override
-    public void stop()
-    {
-
-    }
-
-    @Override
-    public void init()
-    {
-
-    }
+    public void init() {}
 }