110 lines
3.6 KiB
Groff
110 lines
3.6 KiB
Groff
.\" $NetBSD: cpu_lwp_fork.9,v 1.2 2006/01/29 03:09:19 rpaulo Exp $
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.\"
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.\" Copyright (c) 2002, 2005, 2006 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; and Rui Paulo.
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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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.Dd January 29, 2006
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.Dt CPU_LWP_FORK 9
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.Os
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.Sh NAME
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.Nm cpu_lwp_fork ,
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.Nm child_return ,
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.Nm proc_trampoline
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.Nd finish a fork operation
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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_lwp_fork "struct lwp *l1" "struct lwp *l2" "void *stack" \
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"size_t stacksize" "void (*func)(void *)" "void *arg"
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.Ft void
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.Fn child_return "void *arg"
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.Sh DESCRIPTION
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.Fn cpu_lwp_fork
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is the machine-dependent portion of
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.Fn fork1
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which finishes a fork operation, with child lwp
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.Fa l2
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nearly set up.
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It copies and updates the PCB and trap frame from the parent
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.Fa l1 ,
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making the child ready to run.
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.Pp
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.Fn cpu_lwp_fork
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rigs the child's kernel stack so that it will start in
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.Fn proc_trampoline .
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.Fn proc_trampoline
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does not have a normal calling sequence and is entered by
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.Fn cpu_switch .
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If an alternate user-level stack is requested (with non-zero values
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in both the
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.Fa stack
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and
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.Fa stacksize
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arguments), the user stack pointer is set up accordingly.
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.Pp
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After being entered by
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.Fn cpu_switch
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and while running in user context (within the kernel)
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.Fn proc_trampoline
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will invoke the function
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.Fa func
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with the argument
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.Fa arg .
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If a kernel thread is being created, the return path and argument
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are specified with
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.Fa func
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and
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.Fa arg .
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If a user process is being created,
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.Fn fork1
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will pass
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.Fn child_return
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and
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.Fa l2
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to
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.Fn cpu_lwp_fork
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as
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.Fa func
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and
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.Fa arg
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respectively.
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This causes the newly-created child process to go directly to user
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level with an apparent return value of 0 from
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.Xr fork 2 ,
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while the parent process returns normally.
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.Sh SEE ALSO
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.Xr fork 2 ,
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.Xr cpu_switch 9 ,
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.Xr fork1 9
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