pthread_sigmask(3)

1PTHREAD_SIGMASK(3)         Linux Programmer's Manual        PTHREAD_SIGMASK(3)
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NAME

6       pthread_sigmask - examine and change mask of blocked signals
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SYNOPSIS

9       #include <signal.h>
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11       int pthread_sigmask(int how, const sigset_t *set, sigset_t *oldset);
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13       Compile and link with -pthread.
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15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17       pthread_sigmask():
18           _POSIX_C_SOURCE >= 199506L || _XOPEN_SOURCE >= 500
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DESCRIPTION

21       The  pthread_sigmask()  function  is just like sigprocmask(2), with the
22       difference that its use in multithreaded programs is explicitly  speci‐
23       fied by POSIX.1.  Other differences are noted in this page.
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25       For  a description of the arguments and operation of this function, see
26       sigprocmask(2).
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RETURN VALUE

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

33       See sigprocmask(2).
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ATTRIBUTES

36       For   an   explanation   of   the  terms  used  in  this  section,  see
37       attributes(7).
38
39       ┌──────────────────┬───────────────┬─────────┐
40       │Interface         │ Attribute     │ Value   │
41       ├──────────────────┼───────────────┼─────────┤
42       │pthread_sigmask() │ Thread safety │ MT-Safe │
43       └──────────────────┴───────────────┴─────────┘

CONFORMING TO

45       POSIX.1-2001, POSIX.1-2008.
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NOTES

48       A new thread inherits a copy of its creator's signal mask.
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50       The glibc pthread_sigmask() function silently ignores attempts to block
51       the  two real-time signals that are used internally by the NPTL thread‐
52       ing implementation.  See nptl(7) for details.
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EXAMPLE

55       The program below blocks some signals in the main thread, and then cre‐
56       ates  a  dedicated  thread  to fetch those signals via sigwait(3).  The
57       following shell session demonstrates its use:
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59           $ ./a.out &
60           [1] 5423
61           $ kill -QUIT %1
62           Signal handling thread got signal 3
63           $ kill -USR1 %1
64           Signal handling thread got signal 10
65           $ kill -TERM %1
66           [1]+  Terminated              ./a.out
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68   Program source
69
70       #include <pthread.h>
71       #include <stdio.h>
72       #include <stdlib.h>
73       #include <unistd.h>
74       #include <signal.h>
75       #include <errno.h>
76
77       /* Simple error handling functions */
78
79       #define handle_error_en(en, msg) \
80               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
81
82       static void *
83       sig_thread(void *arg)
84       {
85           sigset_t *set = arg;
86           int s, sig;
87
88           for (;;) {
89               s = sigwait(set, &sig);
90               if (s != 0)
91                   handle_error_en(s, "sigwait");
92               printf("Signal handling thread got signal %d\n", sig);
93           }
94       }
95
96       int
97       main(int argc, char *argv[])
98       {
99           pthread_t thread;
100           sigset_t set;
101           int s;
102
103           /* Block SIGQUIT and SIGUSR1; other threads created by main()
104              will inherit a copy of the signal mask. */
105
106           sigemptyset(&set);
107           sigaddset(&set, SIGQUIT);
108           sigaddset(&set, SIGUSR1);
109           s = pthread_sigmask(SIG_BLOCK, &set, NULL);
110           if (s != 0)
111               handle_error_en(s, "pthread_sigmask");
112
113           s = pthread_create(&thread, NULL, &sig_thread, (void *) &set);
114           if (s != 0)
115               handle_error_en(s, "pthread_create");
116
117           /* Main thread carries on to create other threads and/or do
118              other work */
119
120           pause();            /* Dummy pause so we can test program */
121       }
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COLOPHON

128       This  page  is  part of release 5.04 of the Linux man-pages project.  A
129       description of the project, information about reporting bugs,  and  the
130       latest     version     of     this    page,    can    be    found    at
131       https://www.kernel.org/doc/man-pages/.
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135Linux                             2019-03-06                PTHREAD_SIGMASK(3)