concurrency: AtomicBoolean and volatile boolean

when multiple threads may be involved
AtomicBoolean: at least once code location tests and then sets the value
volatile boolean: test and set are in different code path

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/discovery/GBScanEventProcessor.java

@@ -31,6 +31,7 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 
 import nodomain.freeyourgadget.gadgetbridge.impl.GBDeviceCandidate;
@@ -62,20 +63,21 @@ public final class GBScanEventProcessor implements Runnable {
 
     private boolean discoverUnsupported = false;
 
-    private volatile boolean running = false;
+    private final AtomicBoolean running;
     private Thread thread = null;
 
     private final Callback callback;
 
     public GBScanEventProcessor(final Callback callback) {
         this.callback = callback;
+        running = new AtomicBoolean(false);
     }
 
     @Override
     public void run() {
         LOG.info("Device Found Processor Thread started.");
 
-        while (running) {
+        while (running.get()) {
             try {
                 LOG.debug("Polling found devices queue, current size = {}", eventsToProcessQueue.size());
                 final String candidateAddress = eventsToProcessQueue.take();
@@ -93,12 +95,11 @@ public final class GBScanEventProcessor implements Runnable {
     }
 
     public void start() {
-        if (running) {
+        if (running.getAndSet(true)) {
             LOG.warn("Already running!");
             return;
         }
 
-        running = true;
         thread = new Thread("GBScanEventProcessor_" + THREAD_COUNTER.getAndIncrement()) {
             @Override
             public void run() {
@@ -109,7 +110,7 @@ public final class GBScanEventProcessor implements Runnable {
     }
 
     public void stop() {
-        running = false;
+        running.set(false);
 
         if (thread != null) {
             thread.interrupt();

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btbr/BtBRQueue.java

@@ -35,6 +35,7 @@ import java.io.IOException;
 import java.util.Arrays;
 import java.util.Locale;
 import java.util.UUID;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 
 import nodomain.freeyourgadget.gadgetbridge.GBApplication;
@@ -54,7 +55,7 @@ public final class BtBRQueue {
     private final SocketCallback mCallback;
     private final UUID mService;
 
-    private volatile boolean mDisposed;
+    private final AtomicBoolean mDisposed;
 
     private final Context mContext;
     private final int mBufferSize;
@@ -70,7 +71,7 @@ public final class BtBRQueue {
 
             LOG.debug("Read thread started, entering loop");
 
-            while (!mDisposed) {
+            while (!mDisposed.get()) {
                 try {
                     if (mBtSocket == null)
                         throw new IOException("mBtSocket was null");
@@ -107,6 +108,7 @@ public final class BtBRQueue {
         mCallback = socketCallback;
         mService = supportedService;
         mBufferSize = bufferSize;
+        mDisposed = new AtomicBoolean(false);
 
         mWriteHandlerThread.start();
 
@@ -272,11 +274,10 @@ public final class BtBRQueue {
     }
 
     public void dispose() {
-        if (mDisposed) {
+        if (mDisposed.getAndSet(true)) {
             return;
         }
 
-        mDisposed = true;
         disconnect();
 
         if (readThread != null && readThread.isAlive()) {

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btclassic/BtClassicIoThread.java

@@ -33,7 +33,6 @@ import java.io.OutputStream;
 import java.net.SocketTimeoutException;
 import java.util.UUID;
 
-import nodomain.freeyourgadget.gadgetbridge.GBApplication;
 import nodomain.freeyourgadget.gadgetbridge.deviceevents.GBDeviceEvent;
 import nodomain.freeyourgadget.gadgetbridge.impl.GBDevice;
 import nodomain.freeyourgadget.gadgetbridge.service.serial.AbstractSerialDeviceSupport;
@@ -51,7 +50,7 @@ public abstract class BtClassicIoThread extends GBDeviceIoThread {
     private BluetoothSocket mBtSocket = null;
     private InputStream mInStream = null;
     private OutputStream mOutStream = null;
-    private boolean mQuit = false;
+    private volatile boolean mQuit = false;
 
     @Override
     public void quit() {