1.\" $NetBSD: userret.9,v 1.3 2002/11/11 06:06:27 gmcgarry Exp $ 2.\" 3.\" Copyright (c) 2002 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Gregory McGarry. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 29.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.Dd September 21, 2002 38.Dt USERRET 9 39.Os 40.Sh NAME 41.Nm userret 42.Nd return path to user-mode execution 43.Sh SYNOPSIS 44.Fd #include \*[Lt]sys/proc.h\*[Gt] 45.Fd #include \*[Lt]sys/sched.h\*[Gt] 46.Ft void 47.Fn userret "struct proc *p" 48.Sh DESCRIPTION 49The 50.Fn userret 51function is executed after processing a trap 52.Pq e.g., a system call or interrupt 53before returning to user-mode execution. 54The implementation is machine dependent and is never invoked from 55machine-independent code. 56The function prototype for each architecture may be different to the 57prototype above, however the functionally provided by the 58.Fn userret 59function on each architecture is essentially the same. 60.Pp 61Specifically, the 62.Fn userret 63function performs the following procedure: 64.Bl -bullet -indent 65.It 66Detect a change in the signal disposition of the current process and invoke 67.Xr postsig 9 68to post the signal to the process. 69This may occur when the outcome of the trap or syscall posted a signal 70to the process 71.Pq e.g. invalid instruction trap . 72.It 73Check the 74.Va want_resched 75flag to see if the scheduler requires the current process to be 76preempted by invoking 77.Xr preempt 9 78.Pq see Xr need_resched 9 . 79This may occur if the clock interrupt causes the scheduler to 80determine that the current process has completed its time slice. 81.It 82Update the scheduler state. 83.El 84.Sh SEE ALSO 85.Xr need_resched 9 , 86.Xr postsig 9 , 87.Xr preempt 9 , 88.Xr scheduler 9 89