From d165cb43488f906a3d56bd81ddd69ff2ac9c7942 Mon Sep 17 00:00:00 2001
From: brooks <brooks@FreeBSD.org>
Date: Thu, 18 Jul 2019 21:33:55 +0000
Subject: [PATCH] Document that setmode(3) is not thread safe.

In some circumstances, setmode(3) may call umask(2) twice to retrieve
the current mode and then restore it.  Between calls, the process will
have a umask of 0.

Reviewed by:	markj
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D20982
---
 lib/libc/gen/setmode.3 | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/libc/gen/setmode.3 b/lib/libc/gen/setmode.3
index 60a161b49144..3e6796239db0 100644
--- a/lib/libc/gen/setmode.3
+++ b/lib/libc/gen/setmode.3
@@ -28,7 +28,7 @@
 .\"     @(#)setmode.3	8.2 (Berkeley) 4/28/95
 .\" $FreeBSD$
 .\"
-.Dd February 22, 2015
+.Dd July 18, 2019
 .Dt SETMODE 3
 .Os
 .Sh NAME
@@ -125,3 +125,10 @@ and
 .Fn setmode
 functions first appeared in
 .Bx 4.4 .
+.Sh BUGS
+The
+.Fn setmode
+function is not thread safe.
+Files created in other threads while
+.Fn setmode
+is being called may be created with a umask of 0.