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SIGSUSPEND(3P)             POSIX Programmer's Manual            SIGSUSPEND(3P)
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.
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 sig-
       suspend() 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.1-2008, <signal.h>
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 Electri-
       cal 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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                       SIGSUSPEND(3P)