+#if defined(RTS_SUPPORTS_THREADS)
+/* number of worker threads waiting for a return capability
+ */
+extern nat rts_n_waiting_workers;
+
+extern void grabReturnCapability(Mutex* pMutex, Capability** pCap);
+extern void yieldToReturningWorker(Mutex* pMutex, Capability** pCap);
+extern void waitForWorkCapability(Mutex* pMutex, Capability** pCap, rtsBool runnable);
+
+
+static inline rtsBool needToYieldToReturningWorker(void)
+{
+ return rts_n_waiting_workers > 0;
+}