pthread_sigmask(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | EXAMPLES | SEE ALSO | COLOPHON

pthread_sigmask(3)      Library Functions Manual      pthread_sigmask(3)

NAME         top

       pthread_sigmask - examine and change mask of blocked signals

LIBRARY         top

       POSIX threads library (libpthread, -lpthread)

SYNOPSIS         top

       #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         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
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           Attribute     Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ pthread_sigmask()                   │ Thread safety │ MT-Safe │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS         top

       POSIX.1-2008.

HISTORY         top

       POSIX.1-2001.

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 <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) \
               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(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         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

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Linux man-pages 6.9.1          2024-06-15             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)