SIGSUSPEND(2,L)             AIX Technical Reference             SIGSUSPEND(2,L)



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sigsuspend, sigpause



PURPOSE

Atomically changes the set of blocked signals and waits for an interrupt.

SYNTAX

#include <signal.h>

int sigsuspend (sigmask)
sigset_t *sigmask;

DESCRIPTION

The sigsuspend system call replaces the process's signal mask with the signal
mask pointed to by the sigmask parameter.  It then suspends execution of the
process until delivery of a signal whose action is either to execute a
signal-catching function or to terminate the process.  The sigsuspend system
call does not allow the SIGKILL, SIGSTOP, or SIGCONT signals to be blocked.  If
a program attempts to block one of these signals, sigsuspend gives no
indication of the error.

If delivery of a signal causes the process to terminate, the sigsuspend system
call does not return.  If delivery of a signal causes a signal-catching
function to execute, the sigsuspend system call returns after the
signal-catching function returns, with the signal mask restored to the set that
existed prior to the sigsuspend call.

The sigsuspend system call sets the signal mask and waits for an unblocked
signal as one atomic operation.  This means that signals cannot occur between
the operations of setting the mask and waiting for a signal.  If a program
invokes the sigprocmask(SIG_SETMASK,...) and pause system calls separately, a
signal that occurs between these system calls might not be noticed by pause.

In normal usage, a signal is blocked by using the sigprocmask(SIG_BLOCK,...)
system call at the beginning of a critical section.  The process then
determines whether there is work for it to do.  If there is no work, the
process waits for work by calling sigsuspend with the mask previously returned
by the sigprocmask system call.

COMPATIBILITY INTERFACES

int sigpause (sigmask)
int sigmask;

The sigpause function only allows signals with values 1-32 to be masked.
Signal i is blocked if the i-th bit in the sigmask parameter is a 1.




Processed November 7, 1990      SIGSUSPEND(2,L)                               1

SIGSUSPEND(2,L)             AIX Technical Reference             SIGSUSPEND(2,L)



RETURN VALUE

If a signal is caught by the calling process and control is returned from the
signal handler, the calling process resumes execution after the sigsuspend
system call, which always returns a value of -1 and sets errno to EINTR.

RELATED INFORMATION

In this book:  "pause," "sigaction, sigvec, signal," and "sigprocmask,
sigsetmask, sigblock."













































Processed November 7, 1990      SIGSUSPEND(2,L)                               2