fix(feedback): Synchronize SampleQueue access across threads

romtsn · claude · romtsn · commit a1a22312508e · 2026-05-05T12:18:53.000+02:00
stop() runs on the main thread while onSensorChanged() runs on the
background HandlerThread. Without synchronization, concurrent access
to the linked list and object pool can corrupt next-pointers and
cause clear() to loop forever.

Co-Authored-By: Claude Opus 4.6 &lt;noreply@anthropic.com&gt;
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/SentryShakeDetector.java b/sentry-android-core/src/main/java/io/sentry/android/core/SentryShakeDetector.java
@@ -91,10 +91,12 @@ public void start(final @NotNull Context context, final @NotNull Listener shakeL
 
   public void stop() {
     listener = null;
-    queue.clear();
     if (sensorManager != null) {
       sensorManager.unregisterListener(this);
     }
+    synchronized (queue) {
+      queue.clear();
+    }
   }
 
   /** Stops detection and releases the background thread. */
@@ -117,14 +119,19 @@ public void onSensorChanged(final @NotNull SensorEvent event) {
     final float az = event.values[2];
     final boolean accelerating = Math.sqrt(ax * ax + ay * ay + az * az) > ACCELERATION_THRESHOLD;
 
-    queue.add(event.timestamp, accelerating);
-    if (queue.isShaking()) {
-      queue.clear();
-      final @Nullable Listener currentListener = listener;
-      if (currentListener != null) {
-        currentListener.onShake();
+    final @Nullable Listener currentListener;
+    synchronized (queue) {
+      queue.add(event.timestamp, accelerating);
+      if (queue.isShaking()) {
+        queue.clear();
+        currentListener = listener;
+      } else {
+        currentListener = null;
       }
     }
+    if (currentListener != null) {
+      currentListener.onShake();
+    }
   }
 
   @Override
