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 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 .