diff -r 3a6b7da09b4f sys/kern/kern_kthread.c
--- a/sys/kern/kern_kthread.c	Mon Jan 25 11:52:47 2010 -0500
+++ b/sys/kern/kern_kthread.c	Mon Jan 25 16:12:46 2010 -0500
@@ -319,12 +319,15 @@ kthread_exit(void)
 	 * We could rely on thread_exit to call exit1() but
 	 * there is extra work that needs to be done
 	 */
-	if (curthread->td_proc->p_numthreads == 1)
-		kproc_exit(0);	/* never returns */
-
 	p = curthread->td_proc;
 	PROC_LOCK(p);
 	PROC_SLOCK(p);
+	if (curthread->td_proc->p_numthreads == 1) {
+		PROC_UNLOCK(p);
+		PROC_SUNLOCK(p);
+		kproc_exit(0);	/* never returns */
+	}
+
 	thread_exit();
 }