SIGSUSPEND(2)                                                    SIGSUSPEND(2)


NAME
     sigsuspend - atomically release blocked signals and wait for interrupt
     (POSIX)

SYNOPSIS
     int sigsuspend(const sigset_t *maskptr);

DESCRIPTION
     sigsuspend replaces the current thread's set of masked signals with the
     set pointed to by maskptr and then suspends the thread until delivery of
     a signal whose action is either to execute a signal-catching function or
     to terminate the process.

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

     In normal usage, a signal is blocked via sigprocmask(2) to begin a
     critical section, variables modified on the occurrence of the signal are
     examined to determine that there is no work to be done, and the thread
     pauses by calling sigsuspend with the mask returned by sigprocmask.  It
     is not possible to block signals that cannot be ignored.  This is
     enforced by the system without causing an error to be indicated.

     Routines described in sigsetops(3) are used to create and manipulate the
     input-parameter signal masks submitted to sigaction(2), sigprocmask(2),
     and sigsuspend(2), and returned by sigpending(2).  These masks are of
     type sigset_t.

NOTES
     POSIX specifies (contrary to BSD and System V) that a thread may block
     SIGCONT.  However, a) SIGCONT always restarts the receiving process
     (unless it is waiting for an event such as I/O), and b) if the receiving
     process has installed a handler for SIGCONT and blocked the signal, the
     process will NOT enter its handler until it unblocks SIGCONT.  (The
     signal will remain pending.)  Therefore, if sigsuspend is called with a
     mask which blocks SIGCONT, receipt of that signal will set the process
     running, but not cause it to enter a handler.

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

ERRORS
     The sigsuspend function will fail if:

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


     [EFAULT]            maskptr points to memory that is not a part of
                         process's valid address space.

SEE ALSO
     sigaction(2), sigpending(2), sigprocmask(2), sigsetops(3).

WARNING
     The POSIX and System V signal facilities have different semantics.  Using
     both facilities in the same program is strongly discouraged and will
     result in unpredictable behavior.


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