Use sched_yield() as fallback for preemption yield.
@@ -157,8 +157,8 @@ void *_dispatch_wait_for_enqueuer(void **ptr);
#define _dispatch_preemption_yield(n) { (void)n; Sleep(0); }
#define _dispatch_preemption_yield_to(th, n) { (void)n; Sleep(0); }
#else
-#define _dispatch_preemption_yield(n) { (void)n; pthread_yield(); }
-#define _dispatch_preemption_yield_to(th, n) { (void)n; pthread_yield(); }
+#define _dispatch_preemption_yield(n) { (void)n; sched_yield(); }
+#define _dispatch_preemption_yield_to(th, n) { (void)n; sched_yield(); }
#endif // HAVE_MACH
#pragma mark -
