+#ifdef THREADED_RTS
+extern SpinLock gc_alloc_block_sync;
+#endif
+
+#if defined(PROF_SPIN) && defined(THREADED_RTS)
+extern StgWord64 whitehole_spin;
+#endif
+
+void gcWorkerThread (Capability *cap);
+void initGcThreads (void);
+void waitForGcThreads (Capability *cap);
+
+#define WORK_UNIT_WORDS 128