pthread_sigmask3
Examine and change mask of blocked signals
Usage
#include <signal.h>
int pthread_sigmask(int how, const sigset_t *set, sigset_t *oldset);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
pthread_sigmask():
_POSIX_C_SOURCE >= 199506L || _XOPEN_SOURCE >= 500
Library
POSIX threads library (libpthread, -lpthread)
Overview
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).
Attributes
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
| pthread_sigmask() | Thread safety | MT-Safe |
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.
Examples
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 <err.h>
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
/* Simple error handling functions */
static void *
sig_thread(void *arg)
{
sigset_t *set = arg;
int s, sig;
for (;;) {
s = sigwait(set, &sig);
if (s != 0)
errc(EXIT_FAILURE, s, "sigwait");
printf("Signal handling thread got signal %d\n", sig);
}
}
int
main(void)
{
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)
errc(EXIT_FAILURE, s, "pthread_sigmask");
s = pthread_create(&thread, NULL, &sig_thread, &set);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_create");
/* Main thread carries on to create other threads and/or do
other work. */
pause(); /* Dummy pause so we can test program */
}
Releases
12 releases since Debian 3.1 (Sarge); the text changed 10 times.