.\" Copyright (c) 2002 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
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-.TH SIGWAITINFO 2 2008-10-04 "Linux" "Linux Programmer's Manual"
+.TH SIGWAITINFO 2 2014-08-19 "Linux" "Linux Programmer's Manual"
.SH NAME
sigwaitinfo, sigtimedwait \- synchronously wait for queued signals
.SH SYNOPSIS
.BR sigwaitinfo ()
suspends execution of the calling thread until one of the signals in
.I set
-is delivered.
+is pending
(If one of the signals in
.I set
is already pending for the calling thread,
.BR sigwaitinfo ()
-will return immediately with information about that signal.)
+will return immediately.)
.BR sigwaitinfo ()
-removes the delivered signal from the set of pending
+removes the signal from the set of pending
signals and returns the signal number as its function result.
If the
.I info
argument is not NULL,
-then it returns a structure of type
+then the buffer that it points to is used to return a structure of type
.I siginfo_t
(see
.BR sigaction (2))
containing information about the signal.
.PP
-Signals returned via
+If multiple signals in
+.I set
+are pending for the caller, the signal that is retrieved by
.BR sigwaitinfo ()
-are delivered in the usual order; see
+is determined according to the usual ordering rules; see
.BR signal (7)
for further details.
.PP
.BR sigwaitinfo ()
except that it has an additional argument,
.IR timeout ,
-which enables an upper bound to be placed on the time for which
-the thread is suspended.
+which specifies the interval for which
+the thread is suspended waiting for a signal.
+(This interval will be rounded up to the system clock granularity,
+and kernel scheduling delays mean that the interval
+may overrun by a small amount.)
This argument is of the following type:
.sp
.in +4n
if none of the signals in
.I set
was pending.
-.SH "RETURN VALUE"
+.SH RETURN VALUE
On success, both
.BR sigwaitinfo ()
and
.B EAGAIN
No signal in
.I set
-was delivered within the
+was became pending within the
.I timeout
period specified to
.BR sigtimedwait ().
.B EINVAL
.I timeout
was invalid.
-.SH "CONFORMING TO"
+.SH CONFORMING TO
POSIX.1-2001.
.SH NOTES
In normal usage, the calling program blocks the signals in
via a prior call to
.BR sigprocmask (2)
(so that the default disposition for these signals does not occur if they
-are delivered between successive calls to
+become pending between successive calls to
.BR sigwaitinfo ()
or
.BR sigtimedwait ())
and does not establish handlers for these signals.
In a multithreaded program,
-the signal should be blocked in all threads to prevent
-the signal being delivered to a thread other than the one calling
+the signal should be blocked in all threads, in order to prevent
+the signal being treated according to its default disposition in
+a thread other than the one calling
.BR sigwaitinfo ()
or
.BR sigtimedwait ()).
and the set of signals that is pending for the process as a whole (see
.BR signal (7)).
+Attempts to wait for
+.B SIGKILL
+and
+.B SIGSTOP
+are silently ignored.
+
If multiple threads of a process are blocked
waiting for the same signal(s) in
.BR sigwaitinfo ()
or
.BR sigtimedwait (),
then exactly one of the threads will actually receive the
-signal if it is delivered to the process as a whole;
+signal if it becomes pending for the process as a whole;
which of the threads receives the signal is indeterminate.
POSIX leaves the meaning of a NULL value for the
as a call to
.BR sigwaitinfo (),
and indeed this is what is done on Linux.
-
+.\"
+.SS C library/kernel ABI differences
On Linux,
.BR sigwaitinfo ()
is a library function implemented on top of
.BR sigtimedwait ().
-.SH "SEE ALSO"
+
+The raw
+.BR sigtimedwait ()
+system call has a fifth argument,
+.IR "size_t sigsetsize" ,
+which specifies the size in bytes of the
+.IR set
+argument.
+The glibc
+.BR sigtimedwait ()
+wrapper function specifies this argument as a fixed value
+(equal to
+.IR sizeof(sigset_t) ).
+.SH SEE ALSO
.BR kill (2),
.BR sigaction (2),
.BR signal (2),
.BR signalfd (2),
.BR sigpending (2),
.BR sigprocmask (2),
-.BR sigqueue (2),
+.BR sigqueue (3),
.BR sigsetops (3),
.BR sigwait (3),
.BR signal (7),
.BR time (7)
+.SH COLOPHON
+This page is part of release 3.79 of the Linux
+.I man-pages
+project.
+A description of the project,
+information about reporting bugs,
+and the latest version of this page,
+can be found at
+\%http://www.kernel.org/doc/man\-pages/.
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