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