NAME

       sigsuspend, rt_sigsuspend - wait for a signal

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <signal.h>

       int sigsuspend(const sigset_t *mask);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       sigsuspend():
           _POSIX_C_SOURCE

DESCRIPTION

       sigsuspend()  temporarily  replaces the signal mask of the calling thread with the mask given by mask and
       then suspends the thread until delivery of a signal whose action is to invoke  a  signal  handler  or  to
       terminate a process.

       If  the  signal terminates the process, then sigsuspend() does not return.  If the signal is caught, then
       sigsuspend() returns after the signal handler returns, and the signal  mask  is  restored  to  the  state
       before the call to sigsuspend().

       It  is  not  possible to block SIGKILL or SIGSTOP; specifying these signals in mask, has no effect on the
       thread's signal mask.

RETURN VALUE

       sigsuspend() always returns -1, with errno set to indicate the error (normally, EINTR).

ERRORS

       EFAULT mask points to memory which is not a valid part of the process address space.

       EINTR  The call was interrupted by a signal; signal(7).

STANDARDS

       POSIX.1-2008.

HISTORY

       POSIX.1-2001.

   C library/kernel differences
       The original Linux system call was named sigsuspend().  However, with the addition of  real-time  signals
       in  Linux  2.2,  the fixed-size, 32-bit sigset_t type supported by that system call was no longer fit for
       purpose.  Consequently, a new system call, rt_sigsuspend(), was added to  support  an  enlarged  sigset_t
       type.   The new system call takes a second argument, size_t sigsetsize, which specifies the size in bytes
       of the signal set in mask.  This argument is currently required to have the  value  sizeof(sigset_t)  (or
       the  error  EINVAL  results).   The  glibc  sigsuspend()  wrapper  function  hides these details from us,
       transparently calling rt_sigsuspend() when the kernel provides it.

NOTES

       Normally, sigsuspend() is used in conjunction with sigprocmask(2) in  order  to  prevent  delivery  of  a
       signal  during  the  execution  of  a  critical  code  section.  The caller first blocks the signals with
       sigprocmask(2).  When the critical code has completed, the caller then waits for the signals  by  calling
       sigsuspend() with the signal mask that was returned by sigprocmask(2) (in the oldset argument).

       See sigsetops(3) for details on manipulating signal sets.

SEE ALSO

       kill(2),  pause(2),  sigaction(2),  signal(2),  sigprocmask(2), sigwaitinfo(2), sigsetops(3), sigwait(3),
       signal(7)