linux-kernel - [PATCH manpages RFC] epoll_wait.2: add epoll

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Date:   Wed, 18 Nov 2020 09:46:16 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
        akpm@...ux-foundation.org, soheil.kdev@...il.com, arnd@...db.de,
        shuochen@...gle.com, linux-man@...r.kernel.org,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH manpages RFC] epoll_wait.2: add epoll_pwait2

From: Willem de Bruijn <willemb@...gle.com>

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

    int epoll_pwait2(int fd, struct epoll_event *events,
                     int maxevents,
                     const struct timespec *timeout,
                     const sigset_t *sigset);

Signed-off-by: Willem de Bruijn <willemb@...gle.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 55890c82a53a..01047df28cb1 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 timeouts. 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
 When successful,
 .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 ()
 is Linux-specific.
@@ -267,7 +292,9 @@ 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
-- 
2.29.2.454.gaff20da3a2-goog