Index: thread/rthread_mutex.c
===================================================================
RCS file: /cvs/src/lib/libc/thread/rthread_mutex.c,v
diff -u -p -r1.6 rthread_mutex.c
--- thread/rthread_mutex.c	20 Sep 2024 02:00:46 -0000	1.6
+++ thread/rthread_mutex.c	13 Jul 2025 01:14:52 -0000
@@ -43,7 +43,7 @@ enum {
 #define SPIN_WAIT()	do { } while (0)
 #endif
 
-static _atomic_lock_t static_init_lock = _SPINLOCK_UNLOCKED;
+static struct __cmtx static_init_lock = __CMTX_INITIALIZER();
 
 int
 pthread_mutex_init(pthread_mutex_t *mutexp, const pthread_mutexattr_t *attr)
@@ -151,10 +151,10 @@ _rthread_mutex_timedlock(pthread_mutex_t
 	 * is NULL.
 	 */
 	if (*mutexp == NULL) {
-		_spinlock(&static_init_lock);
+		__cmtx_enter(&static_init_lock);
 		if (*mutexp == NULL)
 			error = pthread_mutex_init(mutexp, NULL);
-		_spinunlock(&static_init_lock);
+		__cmtx_leave(&static_init_lock);
 		if (error != 0)
 			return (EINVAL);
 	}