remove aggressive thread exits when oversubscribed; was causing significant churn

Author: dgrove-oss

src/queue.c

@@ -5523,15 +5523,10 @@ _dispatch_worker_thread(void *context)
 
 	const int64_t timeout = 5ull * NSEC_PER_SEC;
 	pthread_priority_t old_pri = _dispatch_get_priority();
-	bool oversubscribed = false;
 	do {
 		_dispatch_root_queue_drain(dq, old_pri);
 		_dispatch_reset_priority_and_voucher(old_pri, NULL);
-#if HAVE_INTERNAL_PTHREAD_WORKQUEUE
-		oversubscribed = os_atomic_load2o(qc, dgq_thread_pool_size, ordered) < 0;
-#endif
-	} while (!oversubscribed &&
-			 dispatch_semaphore_wait(&pqc->dpq_thread_mediator,
+	} while (dispatch_semaphore_wait(&pqc->dpq_thread_mediator,
 			dispatch_time(0, timeout)) == 0);
 
 #if HAVE_INTERNAL_PTHREAD_WORKQUEUE