'\" et

.TH SIGSUSPEND "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

This manual page is part of the POSIX Programmer's Manual.

The Linux implementation of this interface may differ (consult

the corresponding Linux manual page for details of Linux behavior),

or the interface may not be implemented on Linux.

.SH NAME

sigsuspend

\(em wait for a signal

.SH SYNOPSIS

.LP

.nf

#include <signal.h>

.P

int sigsuspend(const sigset_t *\fIsigmask\fP);

.fi

.SH DESCRIPTION

The

\fIsigsuspend\fR()

function shall replace the current signal mask of the calling thread

with the set of signals pointed to by

.IR sigmask

and then suspend the thread until delivery of a signal whose action is

either to execute a signal-catching function or to terminate the

process. This shall not cause any other signals that may have been

pending on the process to become pending on the thread.

.P

If the action is to terminate the process then

\fIsigsuspend\fR()

shall never return. If the action is to execute a signal-catching

function, then

\fIsigsuspend\fR()

shall return after the signal-catching function returns, with the

signal mask restored to the set that existed prior to the

\fIsigsuspend\fR()

call.

.P

It is not possible to block signals that cannot be ignored. This is

enforced by the system without causing an error to be indicated.

.SH "RETURN VALUE"

Since

\fIsigsuspend\fR()

suspends thread execution indefinitely, there is no successful

completion return value. If a return occurs, \(mi1 shall be returned and

.IR errno

set to indicate the error.

.SH ERRORS

The

\fIsigsuspend\fR()

function shall fail if:

.TP

.BR EINTR

A signal is caught by the calling process and control is returned from

the signal-catching function.

.LP

.IR "The following sections are informative."

.SH EXAMPLES

None.

.SH "APPLICATION USAGE"

Normally, at the beginning of a critical code section, a specified set

of signals is blocked using the

\fIsigprocmask\fR()

function. When the thread has completed the critical section and

needs to wait for the previously blocked signal(s), it pauses by

calling

\fIsigsuspend\fR()

with the mask that was returned by the

\fIsigprocmask\fR()

call.

.SH RATIONALE

Code which wants to avoid the ambiguity of the signal mask for thread

cancellation handlers can install an additional cancellation handler

which resets the signal mask to the expected value.

.sp

.RS 4

.nf

\fB

void cleanup(void *arg)

{

    sigset_t *ss = (sigset_t *) arg;

    pthread_sigmask(SIG_SETMASK, ss, NULL);

}

.P

int call_sigsuspend(const sigset_t *mask)

{

    sigset_t oldmask;

    int result;

    pthread_sigmask(SIG_SETMASK, NULL, &oldmask);

    pthread_cleanup_push(cleanup, &oldmask);

    result = sigsuspend(sigmask);

    pthread_cleanup_pop(0);

    return result;

}

.fi \fR

.P

.RE

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "Section 2.4" ", " "Signal Concepts",

.IR "\fIpause\fR\^(\|)",

.IR "\fIsigaction\fR\^(\|)",

.IR "\fIsigaddset\fR\^(\|)",

.IR "\fIsigdelset\fR\^(\|)",

.IR "\fIsigemptyset\fR\^(\|)",

.IR "\fIsigfillset\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<signal.h>\fP"

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 7, Copyright (C) 2013 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group.

(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.unix.org/online.html .

Any typographical or formatting errors that appear

in this page are most likely

to have been introduced during the conversion of the source files to

man page format. To report such errors, see

https://www.kernel.org/doc/man-pages/reporting_bugs.html .