132 lines
3.9 KiB
Groff
132 lines
3.9 KiB
Groff
.\" $NetBSD: select.9,v 1.3 2008/05/13 15:52:51 tnn Exp $
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.\"
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.\" Copyright (C) 2002 Chad David <davidc@acns.ab.ca>. 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(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), 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 COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" 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 SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD: src/share/man/man9/selrecord.9,v 1.2 2002/05/30 13:29:17 ru Exp $
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.\"
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.\" FreeBSD: .Dd March 20, 2002
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.Dd May 13, 2008
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.Dt SELECT 9
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.Os
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.Sh NAME
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.Nm seldestroy ,
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.Nm selinit ,
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.Nm selrecord ,
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.Nm selnotify
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.Nd select and poll subsystem
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/select.h
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.Ft void
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.Fn seldestroy "struct selinfo *sip"
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.Ft void
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.Fn selinit "struct selinfo *sip"
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.Ft void
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.Fn selrecord "struct lwp *selector" "struct selinfo *sip"
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.Ft void
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.Fn selnotify "struct selinfo *sip" "int events" "long knhint"
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.Sh DESCRIPTION
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.Fn selinit
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and
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.Fn seldestroy
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functions must be used to initialize and destroy the
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.Va struct selinfo .
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The
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.Fn seldestroy
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function may block.
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.Pp
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.Fn selrecord
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and
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.Fn selnotify
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are used by device drivers to coordinate
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with the kernel implementation of
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.Xr select 2
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and
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.Xr poll 2 .
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Each object that can be polled contains a
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.Dv selinfo
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record.
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Device drivers provide locking for the
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.Dv selinfo
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record.
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.Pp
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.Fn selrecord
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records that the calling thread is interested in events related to a given
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object.
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.Fn selrecord
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should only be called when the poll routine determines that the object
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is not ready for I/O: there are no events of interest pending.
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The check for pending I/O and call to
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.Fn selrecord
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must be atomic.
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Atomicity can be provided by holding the object's lock across the test
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and call to
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.Fn selrecord .
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For non-MPSAFE drivers, the global
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.Dv kernel_lock
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is enough to provide atomicity.
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.Pp
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.Fn selnotify
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is called by the underlying object handling code in order to notify any waiting
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threads that an event of interest has occurred.
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The same lock held across the poll method and call to
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.Fn selrecord
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must be held across the call to
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.Fn selnotify .
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The lock prevents an event of interest being signalled while a thread is
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in the process of recording its interest.
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.Pp
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The
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.Fa events
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indicates which event happen.
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Zero may be used if unknown.
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.Pp
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.Fn selnotify
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also calls
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.Fn KNOTE
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passing
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.Va knhint
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as an argument.
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.Sh CODE REFERENCES
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This section describes places within the
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.Nx
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source tree where actual code implementing select and poll
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subsystem can be found.
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All pathnames are relative to
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.Pa /usr/src .
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.Pp
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The core of the select and poll subsystem implementation is in
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.Pa sys/kern/sys_select.c .
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Data structures and function prototypes are located in
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.Pa sys/sys/select.h ,
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.Pa sys/sys/poll.h
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and
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.Pa sys/sys/selinfo.h .
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.Sh SEE ALSO
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.Xr poll 2 ,
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.Xr select 2 ,
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.Xr knote 9
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