diff --git a/services/audioflinger/IAfThread.h b/services/audioflinger/IAfThread.h
index 7084be9..46a67e8 100644
--- a/services/audioflinger/IAfThread.h
+++ b/services/audioflinger/IAfThread.h
@@ -386,6 +386,12 @@
             const effect_uuid_t* type, bool suspend, audio_session_t sessionId)
             REQUIRES(mutex()) = 0;
 
+    // Wait while the Thread is busy.  This is done to ensure that
+    // the Thread is not busy releasing the Tracks, during which the Thread mutex
+    // may be temporarily unlocked.  Some Track methods will use this method to
+    // avoid races.
+    virtual void waitWhileThreadBusy_l(audio_utils::unique_lock& ul)
+            REQUIRES(mutex()) = 0;
     // Dynamic cast to derived interface
     virtual sp<IAfDirectOutputThread> asIAfDirectOutputThread() { return nullptr; }
     virtual sp<IAfDuplicatingThread> asIAfDuplicatingThread() { return nullptr; }