pthread_sigmask(3) — Linux manual page


PTHREAD_SIGMASK(3)      Linux Programmer's Manual     PTHREAD_SIGMASK(3)

NAME         top

       pthread_sigmask - examine and change mask of blocked signals

SYNOPSIS         top

       #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

           _POSIX_C_SOURCE >= 199506L || _XOPEN_SOURCE >= 500

DESCRIPTION         top

       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         top

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

ERRORS         top

       See sigprocmask(2).

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface                             Attribute     Value   │
       │pthread_sigmask()                     │ Thread safety │ MT-Safe │

CONFORMING TO         top

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

NOTES         top

       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         top

       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);

       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. */

           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         top

       sigaction(2), sigpending(2), sigprocmask(2),
       pthread_attr_setsigmask_np(3), pthread_create(3),
       pthread_kill(3), sigsetops(3), pthreads(7), signal(7)

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

Linux                          2021-03-22             PTHREAD_SIGMASK(3)

Pages that refer to this page: sigprocmask(2)pthread_attr_setsigmask_np(3)pthread_create(3)pthread_kill(3)pthread_sigqueue(3)sd_event_add_child(3)sd_event_add_signal(3)sigset(3)sigwait(3)nptl(7)pthreads(7)signal(7)signal-safety(7)