diff --git a/lib/libc/gen/tcgetpgrp.3 b/lib/libc/gen/tcgetpgrp.3
--- a/lib/libc/gen/tcgetpgrp.3
+++ b/lib/libc/gen/tcgetpgrp.3
@@ -62,9 +62,27 @@
 .Fa fd
 is not the controlling terminal.
 .El
+.Sh NOTES
+If
+.Fn tcgetpgrp
+is called from a background process and the terminal supports job control,
+a
+.Dv SIGTTIN
+signal will be generated unless it is blocked or ignored.
+If the signal is defaulted, the calling process will be stopped.
+If the signal is caught and a handler is installed, the system call will fail
+with
+.Er EINTR .
+To avoid this, applications should block or ignore
+.Dv SIGTTIN
+when invoking
+.Fn tcgetpgrp
+from a background process.
 .Sh SEE ALSO
 .Xr setpgid 2 ,
 .Xr setsid 2 ,
+.Xr sigaction 2 ,
+.Xr signal 3 ,
 .Xr tcsetpgrp 3
 .Sh STANDARDS
 The
diff --git a/lib/libc/gen/tcsetpgrp.3 b/lib/libc/gen/tcsetpgrp.3
--- a/lib/libc/gen/tcsetpgrp.3
+++ b/lib/libc/gen/tcsetpgrp.3
@@ -79,9 +79,28 @@
 argument does not match the process group ID of a process in the same
 session as the calling process.
 .El
+.Sh NOTES
+If
+.Fn tcsetpgrp
+is called from a background process and the terminal supports
+job control, a
+.Dv SIGTTOU
+signal will be generated unless it is blocked or ignored.
+If the signal is defaulted, the calling process will be stopped.
+If the signal is caught and a handler is installed,
+the system call will fail
+with
+.Er EINTR .
+To avoid this, applications should block or ignore
+.Dv SIGTTOU
+when invoking
+.Fn tcsetpgrp
+from a background process.
 .Sh SEE ALSO
 .Xr setpgid 2 ,
 .Xr setsid 2 ,
+.Xr sigaction 2 ,
+.Xr signal 3 ,
 .Xr tcgetpgrp 3
 .Sh STANDARDS
 The