LibC: Make pthread_once block with a futex instead of yielding

userspace/libraries/LibC/include/bits/types/pthread_types.h

@@ -13,7 +13,7 @@ __BEGIN_DECLS
 
 #include <stdint.h>
 
-typedef int pthread_once_t;
+typedef uint32_t pthread_once_t;
 
 typedef pthread_t pthread_spinlock_t;
 

userspace/libraries/LibC/pthread.cpp

@@ -591,10 +591,14 @@ int pthread_once(pthread_once_t* once_control, void (*init_routine)(void))
 	{
 		init_routine();
 		BAN::atomic_store(*once_control, 2);
+		futex(FUTEX_WAKE_PRIVATE, once_control, -1, nullptr);
+	}
+	else
+	{
+		while (BAN::atomic_load(*once_control) == 1)
+			futex(FUTEX_WAIT_PRIVATE, once_control, 1, nullptr);
 	}
 
-	while (BAN::atomic_load(*once_control) != 2)
-		sched_yield();
 	return 0;
 }