89 lines
3.4 KiB
Groff
89 lines
3.4 KiB
Groff
.\" $NetBSD: userret.9,v 1.2 2002/09/27 08:38:59 wiz Exp $
|
|
.\"
|
|
.\" Copyright (c) 2002 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Gregory McGarry.
|
|
.\"
|
|
.\" 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.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the NetBSD
|
|
.\" Foundation, Inc. and its contributors.
|
|
.\" 4. Neither the name of The NetBSD Foundation nor the names of its
|
|
.\" contributors may be used to endorse or promote products derived
|
|
.\" from this software without specific prior written permission.
|
|
.\"
|
|
.\" 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 September 21, 2002
|
|
.Dt USERRET 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm userret
|
|
.Nd return path to user-mode execution
|
|
.Sh SYNOPSIS
|
|
.Fd #include \*[Lt]sys/proc.h\*[Gt]
|
|
.Fd #include \*[Lt]sys/sched.h\*[Gt]
|
|
.Ft void
|
|
.Fn userret "struct proc *p"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn userret
|
|
function is executed after processing a trap
|
|
.Pq e.g., a system call or interrupt
|
|
before returning to user-mode execution.
|
|
The implementation is machine dependent and is never invoked from
|
|
machine-independent code.
|
|
The function prototype for each architecture may be different to the
|
|
prototype above, however the functionally provided by the
|
|
.Fn userret
|
|
function on each architecture is essentially the same.
|
|
.Pp
|
|
Specifically, the
|
|
.Fn userret
|
|
function performs the following procedure:
|
|
.Bl -bullet -indent
|
|
.It
|
|
Detect a change in the signal disposition of the current process and invoke
|
|
.Xr postsig 9
|
|
to post the signal to the process.
|
|
This may occur when the outcome of the trap or syscall posted a signal
|
|
to the process
|
|
.Pq e.g. invalid instruction trap .
|
|
.It
|
|
Check the
|
|
.Va want_resched
|
|
flag to see if the scheduler requires the current process to be
|
|
preempted by invoking
|
|
.Xr preempt 9
|
|
.Pq see need_resched 9 .
|
|
This may occur if the clock interrupt causes the scheduler to
|
|
determine that the current process has completed its time slice.
|
|
.It
|
|
Update the scheduler state.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr need_resched 9 ,
|
|
.Xr postsig 9 ,
|
|
.Xr preempt 9 ,
|
|
.Xr scheduler 9
|