NetBSD/share/man/man9/cpu_switchto.9

.\"	$NetBSD: cpu_switchto.9,v 1.5 2007/04/18 12:19:45 yamt Exp $
.\"
.\" Copyright (c)2007 YAMAMOTO Takashi,
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.\" ------------------------------------------------------------
.Dd April 18, 2007
.Dt CPU_SWITCHTO 9
.Os
.\" ------------------------------------------------------------
.Sh NAME
.Nm cpu_switchto
.Nd machine-dependent LWP context switching interface
.\" ------------------------------------------------------------
.Sh SYNOPSIS
.In sys/cpu.h
.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
.Ft struct lwp *
.Fn cpu_switchto \
"struct lwp *oldlwp" "struct lwp *newlwp"
.\" ------------------------------------------------------------
.Sh DESCRIPTION
.Fn cpu_switchto
saves the context of the LWP which is currenly running on the processor,
and restores the context of the LWP specified by
.Fa newlwp .
.Pp
.Fn cpu_switchto
doesn't switch address spaces.
.Pp
.Fn cpu_switchto
sets
.Dv curlwp
to
.Fa newlwp .
.Pp
.Fn cpu_switchto
should be called at
.Dv IPL_SCHED .
When
.Fn cpu_switchto
returns, the caller should lower the priority level as soon as possible.
.Pp
.Fn cpu_switchto
might be called with spin mutexes held.
.Pp
It takes the following arguments.
.Bl -tag -width oldlwp
.It Fa oldlwp
Specify the lwp from which we are going to switch, i.e.,
the calling LWP.
If it was
.Dv NULL ,
the context of the LWP currently running on this processor is not saved.
.It Fa newlwp
Specify the lwp to which we are going to switch.
It must not be
.Dv NULL .
.El
.\" ------------------------------------------------------------
.Sh RETURN VALUES
.Fn cpu_switchto
does not return until another LWP calls
.Fn cpu_switchto
to switch to us.
It returns an lwp from which we have been switched, i.e.,
an LWP which called
.Fa cpu_switchto
to switch to us.
.\" ------------------------------------------------------------
.Sh SEE ALSO
.Xr swapcontext 3 ,
.Xr intro 9 ,
.Xr mutex 9 ,
.Xr spl 9