.\" Copyright (c) 2005 Michael Kerrisk

.\" based on earlier work by faith@cs.unc.edu and

.\" Mike Battersby <mib@deakin.edu.au>

.\"

.\" %%%LICENSE_START(VERBATIM)

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.\" manual provided the copyright notice and this permission notice are

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.\" entire resulting derived work is distributed under the terms of a

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.\" Since the Linux kernel and libraries are constantly changing, this

.\" manual page may be incorrect or out-of-date.  The author(s) assume no

.\" responsibility for errors or omissions, or for damages resulting from

.\" the use of the information contained herein.  The author(s) may not

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.\" %%%LICENSE_END

.\"

.\" 2005-09-15, mtk, Created new page by splitting off from sigaction.2

.\"

.TH SIGSUSPEND 2 2017-09-15 "Linux" "Linux Programmer's Manual"

.SH NAME

sigsuspend, rt_sigsuspend \- wait for a signal

.SH SYNOPSIS

.B #include <signal.h>

.PP

.BI "int sigsuspend(const sigset_t *" mask );

.PP

.in -4n

Feature Test Macro Requirements for glibc (see

.BR feature_test_macros (7)):

.in

.PP

.ad l

.BR sigsuspend ():

_POSIX_C_SOURCE

.ad b

.SH DESCRIPTION

.BR sigsuspend ()

temporarily replaces the signal mask of the calling process with the

mask given by

.I mask

and then suspends the process until delivery of a signal whose

action is to invoke a signal handler or to terminate a process.

.PP

If the signal terminates the process, then

.BR sigsuspend ()

does not return.

If the signal is caught, then

.BR sigsuspend ()

returns after the signal handler returns,

and the signal mask is restored to the state before the call to

.BR sigsuspend ().

.PP

It is not possible to block

.B SIGKILL

or

.BR SIGSTOP ;

specifying these signals in

.IR mask ,

has no effect on the process's signal mask.

.SH RETURN VALUE

.BR sigsuspend ()

always returns \-1, with

.I errno

set to indicate the error (normally,

.BR EINTR ).

.SH ERRORS

.TP

.B EFAULT

.I mask

points to memory which is not a valid part of the process address space.

.TP

.B EINTR

The call was interrupted by a signal;

.BR signal (7).

.SH CONFORMING TO

POSIX.1-2001, POSIX.1-2008.

.SH NOTES

.PP

Normally,

.BR sigsuspend ()

is used in conjunction with

.BR sigprocmask (2)

in order to prevent delivery of a signal during the execution of a

critical code section.

The caller first blocks the signals with

.BR sigprocmask (2).

When the critical code has completed, the caller then waits for the

signals by calling

.BR sigsuspend ()

with the signal mask that was returned by

.BR sigprocmask (2)

(in the

.I oldset

argument).

.PP

See

.BR sigsetops (3)

for details on manipulating signal sets.

.\"

.SS C library/kernel differences

The original Linux system call was named

.BR sigsuspend ().

However, with the addition of real-time signals in Linux 2.2,

the fixed-size, 32-bit

.IR sigset_t

type supported by that system call was no longer fit for purpose.

Consequently, a new system call,

.BR rt_sigsuspend (),

was added to support an enlarged

.IR sigset_t

type.

The new system call takes a second argument,

.IR "size_t sigsetsize" ,

which specifies the size in bytes of the signal set in

.IR mask .

This argument is currently required to have the value

.IR sizeof(sigset_t)

(or the error

.B EINVAL

results).

The glibc

.BR sigsuspend ()

wrapper function hides these details from us, transparently calling

.BR rt_sigsuspend ()

when the kernel provides it.

.\"

.SH SEE ALSO

.BR kill (2),

.BR pause (2),

.BR sigaction (2),

.BR signal (2),

.BR sigprocmask (2),

.BR sigwaitinfo (2),

.BR sigsetops (3),

.BR sigwait (3),

.BR signal (7)

.SH COLOPHON

This page is part of release 4.15 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

\%https://www.kernel.org/doc/man\-pages/.