468 lines
9.7 KiB
Groff
468 lines
9.7 KiB
Groff
.\" Copyright 2006,2011 John-Mark Gurney
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.\" All rights reserved.
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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 March 26, 2012
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.Dt KQUEUE 9
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.Os
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.Sh NAME
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.Nm kqueue_add_filteropts , kqueue_del_filteropts ,
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.Nm kqfd_register ,
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.Nm knote_fdclose ,
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.Nm knlist_init , knlist_init_mtx , knlist_init_rw_reader ,
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.Nm knlist_add , knlist_remove , knlist_remove_inevent , knlist_empty ,
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.Nm knlist_clear , knlist_delete , knlist_destroy ,
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.Nm KNOTE_LOCKED , KNOTE_UNLOCKED
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.Nd "event delivery subsystem"
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.Sh SYNOPSIS
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.In sys/event.h
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.Ft int
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.Fn kqueue_add_filteropts "int filt" "struct filterops *filtops"
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.Ft int
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.Fn kqueue_del_filteropts "int filt"
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.Ft int
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.Fn kqfd_register "int fd" "struct kevent *kev" "struct thread *td" "int waitok"
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.Ft void
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.Fn knote_fdclose "struct thread *td" "int fd"
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.Ft void
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.Fo knlist_init
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.Fa "struct knlist *knl"
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.Fa "void *lock"
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.Fa "void \*[lp]*kl_lock\*[rp]\*[lp]void *\*[rp]"
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.Fa "void \*[lp]*kl_unlock\*[rp]\*[lp]void *\*[rp]"
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.Fa "int \*[lp]*kl_locked\*[rp]\*[lp]void *\*[rp]"
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.Fc
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.Ft void
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.Fn knlist_init_mtx "struct knlist *knl" "struct mtx *lock"
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.Ft void
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.Fn knlist_init_rw_reader "struct knlist *knl" "struct rwlock *lock"
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.Ft void
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.Fn knlist_add "struct knlist *knl" "struct knote *kn" "int islocked"
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.Ft void
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.Fn knlist_remove "struct knlist *knl" "struct knote *kn" "int islocked"
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.Ft void
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.Fn knlist_remove_inevent "struct knlist *knl" "struct knote *kn"
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.Ft int
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.Fn knlist_empty "struct knlist *knl"
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.Ft void
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.Fn knlist_clear "struct knlist *knl" "int islocked"
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.Ft void
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.Fn knlist_delete "struct knlist *knl" "struct thread *td" "int islocked"
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.Ft void
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.Fn knlist_destroy "struct knlist *knl"
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.Ft void
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.Fn KNOTE_LOCKED "struct knlist *knl" "long hint"
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.Ft void
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.Fn KNOTE_UNLOCKED "struct knlist *knl" "long hint"
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.Sh DESCRIPTION
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The functions
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.Fn kqueue_add_filteropts
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and
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.Fn kqueue_del_filteropts
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allow for the addition and removal of a filter type.
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The filter is statically defined by the
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.Dv EVFILT_*
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macros.
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The function
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.Fn kqueue_add_filteropts
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will make
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.Fa filt
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available.
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The
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.Vt "struct filterops"
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has the following members:
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.Bl -tag -width ".Va f_attach"
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.It Va f_isfd
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If
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.Va f_isfd
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is set,
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.Va ident
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in
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.Vt "struct kevent"
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is taken to be a file descriptor.
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In this case, the
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.Vt knote
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passed into
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.Va f_attach
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will have the
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.Va kn_fp
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member initialized to the
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.Vt "struct file *"
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that represents the file descriptor.
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.It Va f_attach
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The
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.Va f_attach
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function will be called when attaching a
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.Vt knote
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to the object.
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The method should call
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.Fn knlist_add
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to add the
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.Vt knote
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to the list that was initialized with
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.Fn knlist_init .
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The call to
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.Fn knlist_add
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is only necessary if the object can have multiple
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.Vt knotes
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associated with it.
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If there is no
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.Vt knlist
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to call
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.Fn knlist_add
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with, the function
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.Va f_attach
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must clear the
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.Dv KN_DETACHED
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bit of
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.Va kn_status
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in the
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.Vt knote .
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The function shall return 0 on success, or appropriate error for the failure,
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such as when the object is being destroyed, or does not exist.
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During
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.Va f_attach ,
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it is valid to change the
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.Va kn_fops
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pointer to a different pointer.
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This will change the
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.Va f_event
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and
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.Va f_detach
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functions called when processing the
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.Vt knote .
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.It Va f_detach
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The
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.Va f_detach
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function will be called to detach the
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.Vt knote
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if the
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.Vt knote
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has not already been detached by a call to
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.Fn knlist_remove ,
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.Fn knlist_remove_inevent
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or
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.Fn knlist_delete .
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The list
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.Fa lock
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will not be held when this function is called.
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.It Va f_event
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The
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.Va f_event
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function will be called to update the status of the
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.Vt knote .
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If the function returns 0, it will be assumed that the object is not
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ready (or no longer ready) to be woken up.
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The
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.Fa hint
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argument will be 0 when scanning
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.Vt knotes
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to see which are triggered.
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Otherwise, the
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.Fa hint
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argument will be the value passed to either
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.Dv KNOTE_LOCKED
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or
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.Dv KNOTE_UNLOCKED .
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The
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.Va kn_data
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value should be updated as necessary to reflect the current value, such as
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number of bytes available for reading, or buffer space available for writing.
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If the note needs to be removed,
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.Fn knlist_remove_inevent
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must be called.
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The function
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.Fn knlist_remove_inevent
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will remove the note from the list, the
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.Va f_detach
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function will not be called and the
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.Vt knote
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will not be returned as an event.
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.Pp
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Locks
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.Em must not
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be acquired in
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.Va f_event .
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If a lock is required in
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.Va f_event ,
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it must be obtained in the
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.Fa kl_lock
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function of the
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.Vt knlist
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that the
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.Va knote
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was added to.
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.El
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.Pp
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The function
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.Fn kqfd_register
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will register the
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.Vt kevent
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on the kqueue file descriptor
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.Fa fd .
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If it is safe to sleep,
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.Fa waitok
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should be set.
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.Pp
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The function
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.Fn knote_fdclose
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is used to delete all
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.Vt knotes
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associated with
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.Fa fd .
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Once returned, there will no longer be any
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.Vt knotes
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associated with the
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.Fa fd .
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The
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.Vt knotes
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removed will never be returned from a
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.Xr kevent 2
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call, so if userland uses the
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.Vt knote
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to track resources, they will be leaked.
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The
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.Fn FILEDESC_LOCK
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lock must be held over the call to
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.Fn knote_fdclose
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so that file descriptors cannot be added or removed.
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.Pp
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The
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.Fn knlist_*
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family of functions are for managing
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.Vt knotes
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associated with an object.
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A
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.Vt knlist
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is not required, but is commonly used.
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If used, the
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.Vt knlist
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must be initialized with either
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.Fn knlist_init ,
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.Fn knlist_init_mtx
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or
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.Fn knlist_init_rw_reader .
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The
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.Vt knlist
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structure may be embedded into the object structure.
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The
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.Fa lock
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will be held over
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.Va f_event
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calls.
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.Pp
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For the
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.Fn knlist_init
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function, if
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.Fa lock
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is
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.Dv NULL ,
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a shared global lock will be used and the remaining arguments must be
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.Dv NULL .
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The function pointers
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.Fa kl_lock , kl_unlock
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and
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.Fa kl_locked
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will be used to manipulate the argument
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.Fa lock .
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If any of the function pointers are
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.Dv NULL ,
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a function operating on
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.Dv MTX_DEF
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style
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.Xr mutex 9
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locks will be used instead.
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.Pp
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The function
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.Fn knlist_init_mtx
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may be used to initialize a
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.Vt knlist
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when
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.Fa lock
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is a
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.Dv MTX_DEF
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style
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.Xr mutex 9
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lock.
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.Pp
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The function
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.Fn knlist_init_rw_reader
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may be used to initialize a
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.Vt knlist
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when
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.Fa lock
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is a
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.Xr rwlock 9
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read lock.
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Lock is acquired via
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.Fn rw_rlock
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function.
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.Pp
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The function
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.Fn knlist_empty
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returns true when there are no
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.Vt knotes
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on the list.
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The function requires that the
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.Fa lock
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be held when called.
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.Pp
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The function
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.Fn knlist_clear
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removes all
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.Vt knotes
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from the list.
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The
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.Fa islocked
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argument declares if the
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.Fa lock
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has been acquired.
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All
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.Vt knotes
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will have
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.Dv EV_ONESHOT
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set so that the
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.Vt knote
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will be returned and removed durning the next scan.
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The
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.Va f_detach
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function will be called when the
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.Vt knote
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is deleted durning the next scan.
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This function must not be used when
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.Va f_isfd
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is set in
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.Vt "struct filterops" ,
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as the
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.Fa td
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argument of
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.Fn fdrop
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will be
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.Dv NULL .
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.Pp
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The function
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.Fn knlist_delete
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removes and deletes all
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.Vt knotes
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on the list.
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The function
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.Va f_detach
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will not be called, and the
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.Vt knote
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will not be returned on the next scan.
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Using this function could leak user land resources if a process uses the
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.Vt knote
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to track resources.
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.Pp
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Both the
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.Fn knlist_clear
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and
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.Fn knlist_delete
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functions may sleep.
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They also may release the
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.Fa lock
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to wait for other
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.Vt knotes
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to drain.
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.Pp
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The
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.Fn knlist_destroy
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function is used to destroy a
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.Vt knlist .
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There must be no
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.Vt knotes
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associated with the
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.Vt knlist
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.Po Fn knlist_empty
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returns true
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.Pc
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and no more
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.Vt knotes
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may be attached to the object.
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A
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.Vt knlist
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may be emptied by calling
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.Fn knlist_clear
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or
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.Fn knlist_delete .
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.Pp
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The macros
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.Fn KNOTE_LOCKED
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and
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.Fn KNOTE_UNLOCKED
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are used to notify
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.Vt knotes
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about events associated with the object.
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It will iterate over all
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.Vt knotes
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on the list calling the
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.Va f_event
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function associated with the
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.Vt knote .
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The macro
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.Fn KNOTE_LOCKED
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must be used if the lock associated with the
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.Fa knl
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is held.
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The function
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.Fn KNOTE_UNLOCKED
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will acquire the lock before iterating over the list of
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.Vt knotes .
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.Sh RETURN VALUES
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The function
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.Fn kqueue_add_filteropts
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will return zero on success,
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.Er EINVAL
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in the case of an invalid
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.Fa filt ,
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or
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.Er EEXIST
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if the filter has already been installed.
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.Pp
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The function
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.Fn kqueue_del_filteropts
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will return zero on success,
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.Er EINVAL
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in the case of an invalid
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.Fa filt ,
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or
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.Er EBUSY
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if the filter is still in use.
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.Pp
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The function
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.Fn kqfd_register
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will return zero on success,
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.Er EBADF
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if the file descriptor is not a kqueue, or any of the possible values returned
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by
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.Xr kevent 2 .
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.Sh SEE ALSO
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.Xr kevent 2 ,
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.Xr kqueue 2
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.Sh AUTHORS
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This
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manual page was written by
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.An John-Mark Gurney Aq Mt jmg@FreeBSD.org .
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