1.\" $NetBSD: cpu_switchto.9,v 1.8 2007/12/02 19:44:02 wiz Exp $ 2.\" 3.\" Copyright (c)2007 YAMAMOTO Takashi, 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" ------------------------------------------------------------ 28.Dd May 21, 2007 29.Dt CPU_SWITCHTO 9 30.Os 31.\" ------------------------------------------------------------ 32.Sh NAME 33.Nm cpu_switchto 34.Nd machine-dependent LWP context switching interface 35.\" ------------------------------------------------------------ 36.Sh SYNOPSIS 37.In sys/cpu.h 38.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 39.Ft lwp_t * 40.Fn cpu_switchto \ 41"lwp_t *oldlwp" "lwp_t *newlwp" 42.\" ------------------------------------------------------------ 43.Sh DESCRIPTION 44.Fn cpu_switchto 45saves the context of the LWP which is currently running on the processor, 46and restores the context of the LWP specified by 47.Fa newlwp . 48.Pp 49.Fn cpu_switchto 50doesn't switch address spaces. 51.Pp 52.Fn cpu_switchto 53sets 54.Dv curlwp 55to 56.Fa newlwp . 57.Pp 58.Fn cpu_switchto 59should be called at 60.Dv IPL_SCHED . 61When 62.Fn cpu_switchto 63returns, the caller should lower the priority level as soon as possible. 64.Pp 65.Fn cpu_switchto 66might be called with spin mutexes held. 67.Pp 68It takes the following arguments. 69.Bl -tag -width oldlwp 70.It Fa oldlwp 71Specify the lwp from which we are going to switch, i.e., 72the calling LWP. 73If it was 74.Dv NULL , 75the context of the LWP currently running on this processor is not saved. 76.It Fa newlwp 77Specify the lwp to which we are going to switch. 78It must not be 79.Dv NULL . 80.El 81.\" ------------------------------------------------------------ 82.Sh RETURN VALUES 83.Fn cpu_switchto 84does not return until another LWP calls 85.Fn cpu_switchto 86to switch to us. 87It returns the 88.Dv oldlwp 89argument of the 90.Fn cpu_switchto 91which is called to switch back to our LWP. 92It's either an LWP which called 93.Fa cpu_switchto 94to switch to us or 95.Dv NULL 96in the case that the LWP was exiting. 97.\" ------------------------------------------------------------ 98.Sh SEE ALSO 99.Xr swapcontext 3 , 100.Xr intro 9 , 101.Xr mutex 9 , 102.Xr spl 9 103