SIGSUSPEND(2)              Linux Programmer's Manual             SIGSUSPEND(2)

       sigsuspend, rt_sigsuspend - wait for a signal

       #include <signal.h>

       int sigsuspend(const sigset_t *mask);

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

       sigsuspend(): _POSIX_C_SOURCE

       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.

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

       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).

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

       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.

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

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Linux                             2019-03-06                     SIGSUSPEND(2)