1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
|
.\" Copyright (C) 2006, 2010 Michael Kerrisk <mtk.manpages@gmail.com>
.\" Copyright (C) 2009 Petr Baudis <pasky@suse.cz>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date. The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein. The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.TH SIGEVENT 7 2011-09-09 "GNU" "Linux Programmer's Manual"
.SH NAME
sigevent \- structure for notification from asynchronous routines
.SH SYNOPSIS
.nf
union sigval { /* Data passed with notification */
int sival_int; /* Integer value */
void *sival_ptr; /* Pointer value */
};
struct sigevent {
int sigev_notify; /* Notification method */
int sigev_signo; /* Notification signal */
union sigval sigev_value; /* Data passed with
notification */
void (*sigev_notify_function) (union sigval);
/* Function used for thread
notification (SIGEV_THREAD) */
void *sigev_notify_attributes;
/* Attributes for notification thread
(SIGEV_THREAD) */
pid_t sigev_notify_thread_id;
/* ID of thread to signal (SIGEV_THREAD_ID) */
};
.fi
.SH DESCRIPTION
.PP
The
.I sigevent
structure is used by various APIs
to describe the way a process is to be notified about an event
(e.g., completion of an asynchronous request, expiration of a timer,
or the arrival of a message).
.PP
The definition shown in the SYNOPSIS is approximate:
some of the fields in the
.I sigevent
structure may be defined as part of a union.
Programs should employ only those fields relevant
to the value specified in
.IR sigev_notify .
.PP
The
.I sigev_notify
field specifies how notification is to be performed.
This field can have one of the following values:
.TP 8
.BR SIGEV_NONE
A "null" notification: don't do anything when the event occurs.
.TP
.BR SIGEV_SIGNAL
Notify the process by sending the signal specified in
.IR sigev_signo .
.IP
If the signal is caught with a signal handler that was registered using the
.BR sigaction (2)
.B SA_SIGINFO
flag, then the following fields are set in the
.I siginfo_t
structure that is passed as the second argument of the handler:
.RS 8
.TP 10
.I si_code
This field is set to a value that depends on the API
delivering the notification.
.TP
.I si_signo
This field is set to the signal number (i.e., the same value as in
.IR sigev_signo ).
.TP
.I si_value
This field is set to the value specified in
.IR sigev_value .
.RE
.IP
Depending on the API, other fields may also be set in the
.I siginfo_t
structure.
.IP
The same information is also available if the signal is accepted using
.BR sigwaitinfo (2).
.TP
.BR SIGEV_THREAD
Notify the process by invoking
.I sigev_notify_function
"as if" it were the start function of a new thread.
(Among the implementation possibilities here are that
each timer notification could result in the creation of a new thread,
or that a single thread is created to receive all notifications.)
The function is invoked with
.I sigev_value
as its sole argument.
If
.I sigev_notify_attributes
is not NULL, it should point to a
.I pthread_attr_t
structure that defines attributes for the new thread (see
.BR pthread_attr_init (3)).
.TP
.BR SIGEV_THREAD_ID " (Linux-specific)"
.\" | SIGEV_SIGNAL vs not?
Currently used only by POSIX timers; see
.BR timer_create (2).
.SH CONFORMING TO
POSIX.1-2001.
.SH SEE ALSO
.BR timer_create (2),
.BR aio_fsync (3),
.BR aio_read (3),
.BR aio_write (3),
.BR getaddrinfo_a (3),
.BR lio_listio (3),
.BR mq_notify (3),
.BR aio (7),
.BR pthreads (7)
|
