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.\" $NetBSD: cpu_need_resched.9,v 1.2 2007/02/17 17:25:34 yamt Exp $
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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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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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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2007-02-17 20:18:31 +03:00
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.Dd February 18, 2007
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.Dt CPU_NEED_RESCHED 9
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.Os
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.Sh NAME
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.Nm cpu_need_resched
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.Nd context switch notification
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.Sh SYNOPSIS
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.In sys/proc.h
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.Ft void
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.Fn cpu_need_resched "struct cpu_info *ci"
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.Sh DESCRIPTION
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The
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.Fn cpu_need_resched
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function is the machine-independent interface for the scheduler to
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notify machine-dependent code that a context switch from the current
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process is required.
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This event may occur if a higher priority process appears on the run
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queue or if the current process has exceeded its time slice.
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.Pp
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Specifically, the
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.Fn cpu_need_resched
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function will perform the following operations:
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.Bl -bullet -offset indent
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.It
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Set a global flag which is checked by
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.Xr userret 9
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when returning to user-mode execution.
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.It
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Post an asynchronous software trap (AST).
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.El
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.Sh SEE ALSO
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.Xr scheduler 9 ,
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.Xr userret 9
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