Add initializers

lib/mutex.c

@@ -32,6 +32,10 @@ static inline bool owner_is_running(uintptr_t owner) {
     return atomic_load(&((struct task*)owner)->on_cpu, ATOMIC_RELAXED);
 }
 
+void mutex_init(mutex_t* mutex) {
+    atomic_store(mutex, 0, ATOMIC_RELAXED);
+}
+
 bool mutex_trylock(mutex_t* mutex) {
     uintptr_t self = self_token();
     uintptr_t word = atomic_load(mutex, ATOMIC_RELAXED);