Index: sys/dev/pty/pty.c
===================================================================
--- sys/dev/pty/pty.c
+++ sys/dev/pty/pty.c
@@ -52,10 +52,10 @@
  * binary emulation.
  */
 
-static unsigned int pty_warningcnt = 1;
+static unsigned pty_warningcnt = 1;
 SYSCTL_UINT(_kern, OID_AUTO, tty_pty_warningcnt, CTLFLAG_RW,
-	&pty_warningcnt, 0,
-	"Warnings that will be triggered upon legacy PTY allocation");
+    &pty_warningcnt, 0,
+    "Warnings that will be triggered upon legacy PTY allocation");
 
 static int
 ptydev_fdopen(struct cdev *dev, int fflags, struct thread *td, struct file *fp)
@@ -77,12 +77,7 @@
 	}
 
 	/* Raise a warning when a legacy PTY has been allocated. */
-	if (pty_warningcnt > 0) {
-		pty_warningcnt--;
-		log(LOG_INFO, "pid %d (%s) is using legacy pty devices%s\n",
-		    td->td_proc->p_pid, td->td_name,
-		    pty_warningcnt ? "" : " - not logging anymore");
-	}
+	counted_warning(&pty_warningcnt, "is using legacy pty devices");
 
 	return (0);
 }
Index: sys/kern/subr_prf.c
===================================================================
--- sys/kern/subr_prf.c
+++ sys/kern/subr_prf.c
@@ -1196,3 +1196,22 @@
 	}
 }
 
+void
+counted_warning(unsigned *counter, const char *msg)
+{
+	struct thread *td;
+	unsigned c;
+
+	for (;;) {
+		c = *counter;
+		if (c == 0)
+			break;
+		if (atomic_cmpset_int(counter, c, c - 1)) {
+			td = curthread;
+			log(LOG_INFO, "pid %d (%s) %s%s\n",
+			    td->td_proc->p_pid, td->td_name, msg,
+			    c > 1 ? "" : " - not logging anymore");
+			break;
+		}
+	}
+}
Index: sys/sys/systm.h
===================================================================
--- sys/sys/systm.h
+++ sys/sys/systm.h
@@ -447,4 +447,6 @@
 
 extern void (*softdep_ast_cleanup)(void);
 
+void counted_warning(unsigned *counter, const char *msg);
+
 #endif /* !_SYS_SYSTM_H_ */