1.\" $NetBSD: cpu_idle.9,v 1.9 2007/04/20 13:45:43 yamt 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 April 20, 2007 29.Dt CPU_IDLE 9 30.Os 31.\" ------------------------------------------------------------ 32.Sh NAME 33.Nm cpu_idle 34.Nd machine-dependent processor idling interface 35.\" ------------------------------------------------------------ 36.Sh SYNOPSIS 37.In sys/cpu.h 38.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 39.Ft void 40.Fn cpu_idle \ 41"void" 42.\" ------------------------------------------------------------ 43.Sh DESCRIPTION 44.Fn cpu_idle 45is called by machine-independent code when the processor has 46nothing to do. 47It can be used to conserve the processor power, for example. 48.Pp 49.Fn cpu_idle 50returns immediately if 51.Fn cpu_need_resched 52has been called for the processor after 53the last call of 54.Fn cpu_idle 55or 56.Fn cpu_did_resched 57on the processor. 58.Fn cpu_idle 59returns as soon as possible when 60.Fn cpu_need_resched 61is called for the processor. 62Otherwise, it returns whenever it likes. 63.Pp 64.Fn cpu_idle 65is called at 66.Dv IPL_NONE , 67without any locks held. 68.\" ------------------------------------------------------------ 69.Sh EXAMPLES 70The simplest (and, in some cases, the best) implementation of 71.Fn cpu_idle 72is the following. 73.Bd -literal 74 void 75 cpu_idle(void) 76 { 77 /* nothing */ 78 } 79.Ed 80.\" ------------------------------------------------------------ 81.Sh SEE ALSO 82.Xr cpu_need_resched 9 , 83.Xr cpu_switchto 9 , 84.Xr intro 9 , 85.Xr spl 9 86