SIGSUSPEND(3)              POSIX Programmer's Manual             SIGSUSPEND(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       sigsuspend -- wait for a signal

SYNOPSIS
       #include <signal.h>

       int sigsuspend(const sigset_t *sigmask);

DESCRIPTION
       The sigsuspend() function shall replace the current signal mask of the
       calling thread with the set of signals pointed to by 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.

       If the action is to terminate the process then sigsuspend() shall never
       return. If the action is to execute a signal-catching function, then
       sigsuspend() shall return after the signal-catching function returns,
       with the signal mask restored to the set that existed prior to the
       sigsuspend() call.

       It is not possible to block signals that cannot be ignored. This is
       enforced by the system without causing an error to be indicated.

RETURN VALUE
       Since sigsuspend() suspends thread execution indefinitely, there is no
       successful completion return value. If a return occurs, -1 shall be
       returned and errno set to indicate the error.

ERRORS
       The sigsuspend() function shall fail if:

       EINTR  A signal is caught by the calling process and control is
              returned from the signal-catching function.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       Normally, at the beginning of a critical code section, a specified set
       of signals is blocked using the sigprocmask() function. When the thread
       has completed the critical section and needs to wait for the previously
       blocked signal(s), it pauses by calling sigsuspend() with the mask that
       was returned by the sigprocmask() call.

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.


           void cleanup(void *arg)
           {
               sigset_t *ss = (sigset_t *) arg;
               pthread_sigmask(SIG_SETMASK, ss, NULL);
           }

           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;
           }

FUTURE DIRECTIONS
       None.

SEE ALSO
       Section 2.4, Signal Concepts, pause(), sigaction(), sigaddset(),
       sigdelset(), sigemptyset(), sigfillset()

       The Base Definitions volume of POSIX.1-2017, <signal.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  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.opengroup.org/unix/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 .



IEEE/The Open Group                  2017                        SIGSUSPEND(3)
