2007-02-17 20:48:17 +03:00
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.\" $NetBSD: cpu_switchto.9,v 1.3 2007/02/17 17:48:17 yamt Exp $
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2007-02-17 19:23:08 +03:00
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.\"
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.\" Copyright (c)2007 YAMAMOTO Takashi,
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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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.\" ------------------------------------------------------------
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.Dd February 17, 2007
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.Dt CPU_SWITCHTO 9
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.Os
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.\" ------------------------------------------------------------
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.Sh NAME
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.Nm cpu_switchto
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.Nd machine-dependent LWP context switching interface
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.\" ------------------------------------------------------------
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.Sh SYNOPSIS
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.In sys/lwp.h
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft struct lwp *
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.Fn cpu_switchto \
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"struct lwp *oldlwp" "struct lwp *newlwp"
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.\" ------------------------------------------------------------
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.Sh DESCRIPTION
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.Fn cpu_switchto
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saves the context of the LWP which is currenly running on the processor,
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and restores the context of the LWP specified by
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.Fa newlwp .
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.Pp
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.Fn cpu_switchto
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doesn't switch address spaces.
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2007-02-17 20:48:17 +03:00
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.Pp
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2007-02-17 19:23:08 +03:00
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.Fn cpu_switchto
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2007-02-17 20:48:17 +03:00
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doesn't modify or use
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.Dv curlwp
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or
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.Dv curproc .
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.Pp
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2007-02-17 20:24:01 +03:00
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.Fn cpu_switchto
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is called with spin mutexes held.
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However, implementations of
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.Fn cpu_switchto
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should not rely on it.
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.Pp
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2007-02-17 19:23:08 +03:00
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It takes the following arguments.
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.Bl -tag -width oldlwp
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.It Fa oldlwp
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Specify the lwp from which we are going to switch, i.e.,
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the calling LWP.
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If it was
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.Dv NULL ,
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the context of the LWP currently running on this processor is not saved.
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.It Fa newlwp
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Specify the lwp to which we are going to switch.
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It must not be
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.Dv NULL .
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.El
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.\" ------------------------------------------------------------
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.Sh RETURN VALUES
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.Fn cpu_switchto
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does not return until another LWP calls
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.Fn cpu_switchto
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to switch to us.
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It returns an lwp from which we have been switched, i.e.,
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an LWP which called
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.Fa cpu_switchto
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to switch to us.
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.\" ------------------------------------------------------------
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.Sh SEE ALSO
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.Xr swapcontext 3 ,
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.Xr intro 9 ,
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.Xr mutex 9 ,
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.Xr spl 9
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