Thread-safe state management

When managing state accessed by multiple threads, ensure thread safety through appropriate synchronization mechanisms:

1. Use thread-safe collections for multi-threaded access:

   // Incorrect
   private List<TraceListener> listeners;
      
   // Correct
   private final List<TraceListener> listeners = new CopyOnWriteArrayList<>();
   

2. Implement proper lazy initialization with either:
   • Volatile fields with double-checked locking
   • The LazyValue abstraction
   • Initialization at construction time with final fields ```java // Incorrect - not thread-safe private TraceManager traceManager;

   public TraceManager getTraceManager() { if (traceManager == null) { traceManager = new TraceManager(); // Race condition! } return traceManager; }

   // Correct - thread-safe with volatile private volatile TraceManager traceManager;

   public TraceManager getTraceManager() { TraceManager result = traceManager; if (result == null) { synchronized (this) { result = traceManager; if (result == null) { traceManager = result = new TraceManager(); } } } return result; } ```

3. For bit flag operations, use atomic operations rather than separate atomic fields:

   // Correct pattern for concurrent bit flag operations
   private boolean set(byte bitMask) {
       byte state = this.state;
       for (;;) {
           if ((state & bitMask) != 0) {
               return false;
           }
           final byte newState = (byte) (state | bitMask);
           // Use compareAndExchange for atomicity
           byte oldState = STATE_UPDATER.compareAndExchange(this, state, newState);
           if (oldState == state) {
               return true;
           }
           state = oldState;
       }
   }
   

4. Avoid storing shared mutable state in fields accessed by concurrent operations:

   // Incorrect - potential race condition
   private static AuthDevUIRecorder recorder;
      
   @BuildStep
   void doSomething(AuthDevUIRecorder recorder) {
       AuthProcessor.recorder = recorder; // Multiple build steps might race
   }
      
   // Correct - pass local parameters
   @BuildStep
   void doSomething(AuthDevUIRecorder recorder) {
       performOperation(recorder);
   }