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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 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).

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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