2008-04-30 17:10:46 +04:00
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.\" $NetBSD: preempt.9,v 1.6 2008/04/30 13:10:58 martin Exp $
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2002-09-22 10:26:33 +04:00
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.\"
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.\" Copyright (c) 2002 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Gregory McGarry.
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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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2002-09-27 12:38:58 +04:00
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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2002-09-22 10:26:33 +04:00
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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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2007-07-03 16:14:24 +04:00
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.Dd July 3, 2007
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2002-09-22 10:26:33 +04:00
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.Dt PREEMPT 9
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.Os
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.Sh NAME
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2007-07-03 16:14:24 +04:00
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.Nm preempt ,
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.Nm yield
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.Nd general preempt and yield functions
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2002-09-22 10:26:33 +04:00
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.Sh SYNOPSIS
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2003-04-16 17:34:34 +04:00
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.In sys/sched.h
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2002-09-22 10:26:33 +04:00
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.Ft void
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2007-07-03 16:14:24 +04:00
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.Fn preempt "void"
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.In sys/proc.h
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.Ft void
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.Fn yield "void"
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2002-09-22 10:26:33 +04:00
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.Sh DESCRIPTION
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The
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.Fn preempt
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2007-07-03 16:14:24 +04:00
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function puts the current LWP back on the system run queue
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2002-09-27 12:38:58 +04:00
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and performs an involuntary context switch.
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2002-09-22 10:26:33 +04:00
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The
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2007-07-03 16:14:24 +04:00
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.Fn yield
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function is mostly same as
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.Fn preempt ,
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except that it performs a voluntary context switch.
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.Pp
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These functions drop the kernel lock before switching
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and re-acquire it before returning.
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