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.
31

ERRORS

33       See sigprocmask(2).
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ATTRIBUTES

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

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

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

56       The program below blocks some signals in the main thread, and then cre‐
57       ates  a  dedicated  thread  to fetch those signals via sigwait(3).  The
58       following shell session demonstrates its use:
59
60           $ ./a.out &
61           [1] 5423
62           $ kill -QUIT %1
63           Signal handling thread got signal 3
64           $ kill -USR1 %1
65           Signal handling thread got signal 10
66           $ kill -TERM %1
67           [1]+  Terminated              ./a.out
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69   Program source
70
71       #include <pthread.h>
72       #include <stdio.h>
73       #include <stdlib.h>
74       #include <unistd.h>
75       #include <signal.h>
76       #include <errno.h>
77
78       /* Simple error handling functions */
79
80       #define handle_error_en(en, msg) \
81               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
82
83       static void *
84       sig_thread(void *arg)
85       {
86           sigset_t *set = arg;
87           int s, sig;
88
89           for (;;) {
90               s = sigwait(set, &sig);
91               if (s != 0)
92                   handle_error_en(s, "sigwait");
93               printf("Signal handling thread got signal %d\n", sig);
94           }
95       }
96
97       int
98       main(int argc, char *argv[])
99       {
100           pthread_t thread;
101           sigset_t set;
102           int s;
103
104           /* Block SIGQUIT and SIGUSR1; other threads created by main()
105              will inherit a copy of the signal mask. */
106
107           sigemptyset(&set);
108           sigaddset(&set, SIGQUIT);
109           sigaddset(&set, SIGUSR1);
110           s = pthread_sigmask(SIG_BLOCK, &set, NULL);
111           if (s != 0)
112               handle_error_en(s, "pthread_sigmask");
113
114           s = pthread_create(&thread, NULL, &sig_thread, &set);
115           if (s != 0)
116               handle_error_en(s, "pthread_create");
117
118           /* Main thread carries on to create other threads and/or do
119              other work. */
120
121           pause();            /* Dummy pause so we can test program */
122       }
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COLOPHON

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131       description  of  the project, information about reporting bugs, and the
132       latest    version    of    this    page,    can     be     found     at
133       https://www.kernel.org/doc/man-pages/.
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137Linux                             2021-03-22                PTHREAD_SIGMASK(3)