xref: /freebsd/share/man/man3/sigevent.3 (revision fa9896e082a1046ff4fbc75fcba4d18d1f2efc19)

.\" -*- nroff -*-
.\"
.\" Copyright (c) 2016 John H. Baldwin <jhb@FreeBSD.org>
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd February 25, 2020
.Dt SIGEVENT 3
.Os
.Sh NAME
.Nm sigevent
.Nd "asynchronous event notification"
.Sh SYNOPSIS
.In signal.h
.Sh DESCRIPTION
Some operations permit threads to request asynchronous notification of events
via a
.Vt struct sigevent
structure.
This structure contains several fields that describe the requested notification:
.Bl -column ".Vt void (*)(union sigval)" ".Va sigev_notify_kevent_flags"
.It Sy Type Ta Sy Member Ta Sy Description
.It Vt int Ta sigev_notify Ta notification method
.It Vt int Ta sigev_signo Ta signal number
.It Vt union sigval Ta sigev_value Ta signal value
.It Vt int Ta sigev_notify_kqueue Ta
.Xr kqueue 2
file descriptor
.It Vt unsigned short Ta sigev_notify_kevent_flags Ta kevent flags
.It Vt lwpid_t Ta sigev_notify_thread_id Ta LWP ID
.It Vt void (*)(union sigval) Ta sigev_notify_function Ta
callback function pointer
.It Vt pthread_attr_t * Ta sigev_notify_attributes Ta
callback thread attributes
.El
.Pp
The
.Va sigev_notify
field specifies the notification method used when the event triggers:
.Bl -tag -width ".Dv SIGEV_THREAD_ID"
.It Dv SIGEV_NONE
No notification is sent.
.It Dv SIGEV_SIGNAL
The signal
.Va sigev_signo
is queued as a real-time signal to the calling process.
The value stored in
.Va sigev_value
will be present in the
.Va si_value
of the
.Vt siginfo_t
structure of the queued signal.
.It Dv SIGEV_THREAD
The notification function in
.Va sigev_notify_function
is called in a separate thread context.
The thread is created with the attributes specified in
.Va *sigev_notify_attributes .
The value stored in
.Va sigev_value
is passed as the sole argument to
.Va sigev_notify_function .
If
.Va sigev_notify_attributes
is
.Dv NULL ,
the thread is created with default attributes.
.It Dv SIGEV_KEVENT
A new kevent is posted to the kqueue
.Va sigev_notify_kqueue .
The
.Va udata
member of the kevent structure contains the value stored in
.Va sigev_value .
The meaning of other fields in the kevent are specific to the type of triggered
event.
.It Dv SIGEV_THREAD_ID
The signal
.Va sigev_signo
is queued to the thread whose LWP ID is
.Va sigev_notify_thread_id .
The value stored in
.Va sigev_value
will be present in the
.Va si_value
of the
.Vt siginfo_t
structure of the queued signal.
.El
.Sh NOTES
Note that programs wishing to use
.Dv SIGEV_THREAD
notifications must link against the
.Lb librt .
.Sh SEE ALSO
.Xr aio_read 2 ,
.Xr mq_notify 2 ,
.Xr timer_create 2 ,
.Xr siginfo 3
.Sh STANDARDS
The
.Vt struct sigevent
type conforms to
.St -p1003.1-2004 .
.Sh HISTORY
The
.Va sigevent
structure first appeared in
.Fx 3.3 .