thread related function - pthread_sigmask

just a copy of man page:http://man7.org/linux/man-pages/man3/pthread_sigmask.3.html

NAME

pthread_sigmask - examine and change mask of blocked signals

SYNOPSIS

#include <signal.h>

int pthread_sigmask(int how, const sigset_t *set, sigset_t *oldset);

Compile and link with -pthread.

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

pthread_sigmask():
_POSIX_C_SOURCE >= 199506L || _XOPEN_SOURCE >= 500

DESCRIPTION

The pthread_sigmask() function is just like sigprocmask(2), with the
difference that its use in multithreaded programs is explicitly
specified by POSIX.1.  Other differences are noted in this page.

For a description of the arguments and operation of this function,
see sigprocmask(2).

RETURN VALUE

On success, pthread_sigmask() returns 0; on error, it returns an
error number.

ERRORS

See sigprocmask(2).

NOTES

A new thread inherits a copy of its creator's signal mask.

The glibc pthread_sigmask() function silently ignores attempts to
block the two real-time signals that are used internally by the NPTL
threading implementation.  See nptl(7) for details.

EXAMPLE

The program below blocks some signals in the main thread, and then
creates a dedicated thread to fetch those signals via sigwait(3).
The following shell session demonstrates its use:

$ ./a.out &
[1] 5423
$ kill -QUIT %1
Signal handling thread got signal 3
$ kill -USR1 %1
Signal handling thread got signal 10
$ kill -TERM %1
[1]+  Terminated              ./a.out

Program source

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>

/* Simple error handling functions */

#define handle_error_en(en, msg) \
do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

static void *
sig_thread(void *arg)
{
sigset_t *set = arg;
int s, sig;

for (;;) {
s = sigwait(set, &sig);
if (s != 0)
handle_error_en(s, "sigwait");
printf("Signal handling thread got signal %d\n", sig);
}
}

int
main(int argc, char *argv[])
{
pthread_t thread;
sigset_t set;
int s;

/* Block SIGQUIT and SIGUSR1; other threads created by main()
will inherit a copy of the signal mask. */

sigemptyset(&set);
sigaddset(&set, SIGQUIT);
sigaddset(&set, SIGUSR1);
s = pthread_sigmask(SIG_BLOCK, &set, NULL);
if (s != 0)
handle_error_en(s, "pthread_sigmask");

s = pthread_create(&thread, NULL, &sig_thread, (void *) &set);
if (s != 0)
handle_error_en(s, "pthread_create");

/* Main thread carries on to create other threads and/or do
other work */

pause();            /* Dummy pause so we can test program */
}