sigsuspend(2)

NAME

   sigsuspend, rt_sigsuspend - wait for a signal

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
   process with the mask given by mask and then suspends the process 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 process'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).

CONFORMING TO

   POSIX.1-2001, POSIX.1-2008.

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.

   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.

SEE ALSO

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

COLOPHON

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