Name
pthread_sigmask - examine and change mask of blocked signalsLibrary
POSIX threads library ( libpthread ", " -lpthread )Synopsis
#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
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).Attributes
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
T} | Thread safety | MT-Safe |
Standards
POSIX.1-2008.History
POSIX.1-2001.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 <errno.h> #include <pthread.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> /* Simple error handling functions */ #define handle_error_en(en, msg) \e 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\en", 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) handle_error_en(s, "pthread_sigmask"); s = pthread_create(&thread, NULL, &sig_thread, &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 */ }
See Also
- sigaction(2),
- sigpending(2),
- sigprocmask(2),
- pthread_attr_setsigmask_np(3),
- pthread_create(3),
- pthread_kill(3),
- sigsetops(3),
- pthreads(7),
- signal(7)