Index: share/man/man4/termios.4
===================================================================
--- share/man/man4/termios.4
+++ share/man/man4/termios.4
@@ -28,7 +28,7 @@
 .\"	@(#)termios.4	8.4 (Berkeley) 4/19/94
 .\" $FreeBSD$
 .\"
-.Dd December 26, 2009
+.Dd June 27, 2020
 .Dt TERMIOS 4
 .Os
 .Sh NAME
@@ -761,6 +761,13 @@
 wait channel, the number of user and system seconds used,
 the percentage of cpu the process is getting, and the resident
 set size of the process.
+.Pp
+In case the
+.Xr sysctl 8
+variable
+.Va kern.tty_info_kstacks
+is set to a non-zero value, the running thread's stack is
+written to the terminal for debugging purposes.
 .El
 .Pp
 The
@@ -1586,4 +1593,5 @@
 .Xr tcsendbreak 3 ,
 .Xr tcsetattr 3 ,
 .Xr tcsetsid 3 ,
-.Xr tty 4
+.Xr tty 4 ,
+.Xr stack 9