pthread_sigmask - examine and change mask of blocked signals
#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
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).
On success,
pthread_sigmask() returns 0; on error, it returns an error
number.
See
sigprocmask(2).
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
pthread_sigmask () |
Thread safety |
MT-Safe |
POSIX.1-2001, POSIX.1-2008.
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.
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
#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 */
}
sigaction(2),
sigpending(2),
sigprocmask(2),
pthread_create(3),
pthread_kill(3),
sigsetops(3),
pthreads(7),
signal(7)