Index: kern_timeout.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_timeout.c,v
diff -u -p -r1.101 kern_timeout.c
--- kern_timeout.c	13 Jan 2025 03:21:10 -0000	1.101
+++ kern_timeout.c	27 Apr 2025 05:58:06 -0000
@@ -435,6 +435,9 @@ timeout_del(struct timeout *to)
 {
 	int ret = 0;
 
+	if (!ISSET(to->to_flags, TIMEOUT_ONQUEUE))
+		return (0);
+
 	mtx_enter(&timeout_mutex);
 	if (ISSET(to->to_flags, TIMEOUT_ONQUEUE)) {
 		CIRCQ_REMOVE(&to->to_list);
Index: kern_synch.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_synch.c,v
diff -u -p -r1.219 kern_synch.c
--- kern_synch.c	5 Feb 2025 12:21:27 -0000	1.219
+++ kern_synch.c	27 Apr 2025 05:58:06 -0000
@@ -424,14 +424,13 @@ sleep_finish(int timo, int do_sleep)
 	 */
 	atomic_clearbits_int(&p->p_flag, P_SINTR);
 
-	if (timo != 0) {
-		if (p->p_flag & P_TIMEOUT) {
-			error1 = EWOULDBLOCK;
-		} else {
-			/* This can sleep. It must not use timeouts. */
-			timeout_del_barrier(&p->p_sleep_to);
-		}
+	if (timo != 0 && !timeout_del(&p->p_sleep_to)) {
+		/* Wait for endtsleep timeout to finish running */
+		while (!ISSET(atomic_load_int(&p->p_flag), P_TIMEOUT))
+			CPU_BUSY_CYCLE();
 		atomic_clearbits_int(&p->p_flag, P_TIMEOUT);
+
+		error1 = EWOULDBLOCK;
 	}
 
 	/*
@@ -531,8 +530,10 @@ endtsleep(void *arg)
 	struct proc *p = arg;
 
 	SCHED_LOCK();
-	wakeup_proc(p, P_TIMEOUT);
+	wakeup_proc(p, 0);
 	SCHED_UNLOCK();
+
+	atomic_setbits_int(&p->p_flag, P_TIMEOUT);
 }
 
 /*