110 lines
3.3 KiB
Groff
110 lines
3.3 KiB
Groff
.\" $NetBSD: knote.9,v 1.17 2017/04/15 09:50:57 abhinav Exp $
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.\"
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.\" Copyright (c) 2001, 2002, 2003 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This documentation is derived from text contributed by
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.\" Luke Mewburn.
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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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd February 18, 2004
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.Dt KNOTE 9
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.Os
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.Sh NAME
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.Nm knote ,
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.Nm KNOTE
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.Nd raise kernel event
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.Sh SYNOPSIS
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.In sys/event.h
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.Ft void
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.Fn knote "struct klist *list" "long hint"
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.Fn KNOTE "struct klist *list" "long hint"
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.Sh DESCRIPTION
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The
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.Fn knote
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function provides a hook into the kqueue kernel event notification
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mechanism to allow sections of the kernel to raise a kernel event
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in the form of a
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.Sq knote ,
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which is a
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.Fa struct knote
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as defined in
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.In sys/event.h .
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.Pp
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.Fn knote
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takes a singly linked
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.Fa list
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of knotes, along with a
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.Fa hint
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(which is passed to the appropriate filter routine).
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.Fn knote
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then walks the
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.Fa list
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making calls to the filter routine for each knote.
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As each knote contains a reference to the data structure that it is
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attached to, the filter may choose to examine the data structure in
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deciding whether an event should be reported.
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The
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.Fa hint
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is used to pass in additional information, which may not be present in
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the data structure that the filter examines.
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.Pp
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If the filter decides that the event should be returned, it returns a
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non-zero value and
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.Fn knote
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links the knote onto the tail end of the active list in the
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corresponding kqueue for the application to retrieve.
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If the knote is already on the active list, no action is taken, but the
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call to the filter occurs in order to provide an opportunity for the
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filter to record the activity.
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.Pp
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.Fn knote
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must not be called from interrupt contexts running at an interrupt
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priority level higher than
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.Xr splsched 9 .
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.Pp
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.Fn KNOTE
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is a macro that calls
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.Fn knote list hint
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if
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.Fa list
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is not empty.
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.\" .Sh ERRORS
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.Sh SEE ALSO
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.Xr kqueue 2 ,
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.Xr kfilter_register 9
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.Sh HISTORY
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The
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.Fn knote
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and
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.Fn KNOTE
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functions first appeared in
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.Fx 4.1 ,
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and then in
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.Nx 2.0 .
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.Sh AUTHORS
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The
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.Xr kqueue 2
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system was written by
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.An Jonathan Lemon Aq Mt jlemon@FreeBSD.org .
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