From ba47eb5e3cf6ee7b1a0b0d25fffefc7041b782e8 Mon Sep 17 00:00:00 2001
From: Willem de Bruijn <willemb@google.com>
Date: Mon, 11 Jan 2021 19:48:20 -0500
Subject: [PATCH] epoll_wait.2: Add documentation of epoll_pwait2()

Expand the epoll_wait() page with epoll_pwait2(), an epoll_wait()
variant that takes a struct timespec to enable nanosecond
resolution timeout.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
---
 man2/epoll_wait.2 | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/man2/epoll_wait.2 b/man2/epoll_wait.2
index 36001e02b..21d63503a 100644
--- a/man2/epoll_wait.2
+++ b/man2/epoll_wait.2
@@ -22,7 +22,7 @@
 .\"
 .TH EPOLL_WAIT 2 2020-04-11 "Linux" "Linux Programmer's Manual"
 .SH NAME
-epoll_wait, epoll_pwait \- wait for an I/O event on an epoll file descriptor
+epoll_wait, epoll_pwait, epoll_pwait2 \- wait for an I/O event on an epoll file descriptor
 .SH SYNOPSIS
 .nf
 .B #include <sys/epoll.h>
@@ -32,6 +32,9 @@ epoll_wait, epoll_pwait \- wait for an I/O event on an epoll file descriptor
 .BI "int epoll_pwait(int " epfd ", struct epoll_event *" events ,
 .BI "               int " maxevents ", int " timeout ,
 .BI "               const sigset_t *" sigmask );
+.BI "int epoll_pwait2(int " epfd ", struct epoll_event *" events ,
+.BI "                int " maxevents ", const struct timespec *" timeout ,
+.BI "                const sigset_t *" sigmask );
 .fi
 .SH DESCRIPTION
 The
@@ -170,6 +173,25 @@ argument may be specified as NULL, in which case
 .BR epoll_pwait ()
 is equivalent to
 .BR epoll_wait ().
+.SS epoll_pwait2 ()
+The
+.BR epoll_pwait2 ()
+system call is equivalent to
+.BR epoll_pwait ()
+except for the
+.I timeout
+argument. It takes an argument of type
+.I timespec
+to be able to specify nanosecond resolution timeout. This argument functions
+the same as in
+.BR pselect (2)
+and
+.BR ppoll (2).
+If
+.I timeout
+is NULL, then
+.BR epoll_pwait2 ()
+can block indefinitely.
 .SH RETURN VALUE
 On success,
 .BR epoll_wait ()
@@ -217,6 +239,9 @@ Library support is provided in glibc starting with version 2.3.2.
 .BR epoll_pwait ()
 was added to Linux in kernel 2.6.19.
 Library support is provided in glibc starting with version 2.6.
+.PP
+.BR epoll_pwait2 ()
+was added to Linux in kernel 5.11.
 .SH CONFORMING TO
 .BR epoll_wait ()
 and
@@ -269,7 +294,9 @@ this means that timeouts greater than 35.79 minutes are treated as infinity.
 .SS C library/kernel differences
 The raw
 .BR epoll_pwait ()
-system call has a sixth argument,
+and
+.BR epoll_pwait2 ()
+system calls have a sixth argument,
 .IR "size_t sigsetsize" ,
 which specifies the size in bytes of the
 .IR sigmask