103 lines
3.1 KiB
Groff
103 lines
3.1 KiB
Groff
.\" $NetBSD: cpu_lwp_fork.9,v 1.7 2018/04/26 14:59:11 scole Exp $
|
|
.\"
|
|
.\" Copyright (c) 2002, 2005, 2006 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Gregory McGarry; and Rui Paulo.
|
|
.\"
|
|
.\" 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 April 26, 2018
|
|
.Dt CPU_LWP_FORK 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm cpu_lwp_fork ,
|
|
.Nm child_return ,
|
|
.Nm lwp_trampoline
|
|
.Nd finish a fork operation
|
|
.Sh SYNOPSIS
|
|
.In sys/proc.h
|
|
.Ft void
|
|
.Fn cpu_lwp_fork "struct lwp *l1" "struct lwp *l2" "void *stack" \
|
|
"size_t stacksize" "void (*func)(void *)" "void *arg"
|
|
.Ft void
|
|
.Fn child_return "void *arg"
|
|
.Sh DESCRIPTION
|
|
.Fn cpu_lwp_fork
|
|
is the machine-dependent portion of
|
|
.Fn fork1
|
|
which finishes a fork operation, with child lwp
|
|
.Fa l2
|
|
nearly set up.
|
|
It copies and updates the PCB and trap frame from the parent
|
|
.Fa l1 ,
|
|
making the child ready to run.
|
|
.Pp
|
|
.Fn cpu_lwp_fork
|
|
rigs the child's kernel stack so that it will start in
|
|
.Fn lwp_trampoline .
|
|
.Fn lwp_trampoline
|
|
does not have a normal calling sequence and is entered by
|
|
.Fn cpu_switchto .
|
|
If an alternate user-level stack is requested (with non-zero values
|
|
in both the
|
|
.Fa stack
|
|
and
|
|
.Fa stacksize
|
|
arguments), the user stack pointer is set up accordingly.
|
|
.Pp
|
|
After being entered by
|
|
.Fn cpu_switchto
|
|
and while running in user context (within the kernel)
|
|
.Fn lwp_trampoline
|
|
will invoke the function
|
|
.Fa func
|
|
with the argument
|
|
.Fa arg .
|
|
If a kernel thread is being created, the return path and argument
|
|
are specified with
|
|
.Fa func
|
|
and
|
|
.Fa arg .
|
|
If a user process is being created,
|
|
.Fn fork1
|
|
will pass
|
|
.Fn child_return
|
|
and
|
|
.Fa l2
|
|
to
|
|
.Fn cpu_lwp_fork
|
|
as
|
|
.Fa func
|
|
and
|
|
.Fa arg
|
|
respectively.
|
|
This causes the newly-created child process to go directly to user
|
|
level with an apparent return value of 0 from
|
|
.Xr fork 2 ,
|
|
while the parent process returns normally.
|
|
.Sh SEE ALSO
|
|
.Xr fork 2 ,
|
|
.Xr cpu_switchto 9 ,
|
|
.Xr fork1 9
|