106 lines
3.5 KiB
Groff
106 lines
3.5 KiB
Groff
.\" $NetBSD: pcu.9,v 1.2 2012/12/03 07:50:29 wiz Exp $
|
|
.\"
|
|
.\" Copyright (c) 2012 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Mindaugas Rasiukevicius.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd December 2, 2012
|
|
.Dt PCU 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm pcu
|
|
.Nd per-CPU unit (PCU)
|
|
.Sh SYNOPSIS
|
|
.In sys/pcu.h
|
|
.Ft void
|
|
.Fn pcu_load "const pcu_ops_t *pcu"
|
|
.Ft void
|
|
.Fn pcu_save "const pcu_ops_t *pcu"
|
|
.Ft void
|
|
.Fn pcu_save_all "lwp_t *l"
|
|
.Ft void
|
|
.Fn pcu_discard "const pcu_ops_t *pcu"
|
|
.Ft bool
|
|
.Fn pcu_used_p "const pcu_ops_t *pcu"
|
|
.\" -----
|
|
.Sh DESCRIPTION
|
|
Per CPU Unit (PCU) is an interface to manage synchronization of any
|
|
per-CPU context (unit) tied to an LWP context.
|
|
Typical use of PCU is for "lazy-switch" synchronisation of FPU state.
|
|
Each PCU has its operations defined by a
|
|
.Vt pcu_ops_t
|
|
structure.
|
|
Members of
|
|
.Vt pcu_ops_t
|
|
are
|
|
.Bd -literal
|
|
u_int pcu_id;
|
|
void (*pcu_state_save)(lwp_t *l);
|
|
void (*pcu_state_load)(lwp_t *l, bool used);
|
|
void (*pcu_state_release)(lwp_t *l);
|
|
.Ed
|
|
.Pp
|
|
.Bl -tag -width compact
|
|
.It Fn pcu_state_save
|
|
save the current CPU's state into the given LWP's MD storage.
|
|
.It Fn pcu_state_load
|
|
load PCU state from the given LWP's MD storage to the current CPU.
|
|
The
|
|
.Ar used
|
|
argument is true if it is not the first time the LWP uses the PCU.
|
|
.It Fn pcu_state_release
|
|
indicate to MD code that the PCU ownership by the LWP was released,
|
|
therefore the next use of PCU on the LWP shall be detected and
|
|
.Fn pcu_load
|
|
be called to reacquire ownership.
|
|
For example, this would often be the changing of a bit for a CPU to
|
|
trap on the execution of one of the PCU's instructions.
|
|
.El
|
|
.Sh FUNCTIONS
|
|
.Bl -tag -width compact
|
|
.It Fn pcu_load
|
|
Load (initialize) the PCU state of the current LWP on the current CPU.
|
|
.It Fn pcu_save
|
|
Save the PCU state to the given LWP.
|
|
.It Fn pcu_discard
|
|
Discard the PCU state of the current LWP.
|
|
.It Fn pcu_used_p
|
|
Return true if PCU was used (i.e.
|
|
.Fn pcu_load
|
|
was called) by the LWP.
|
|
Otherwise, return false.
|
|
.Fn pcu_save_all
|
|
save PCU state of the given LWP, so that it could be used later.
|
|
.El
|
|
.\" -----
|
|
.Sh CODE REFERENCES
|
|
.Nm
|
|
is implemented within the file
|
|
.Pa sys/kern/subr_pcu.c .
|
|
.Sh HISTORY
|
|
PCU first appeared in
|
|
.Nx 6.0 .
|