1.\" $NetBSD: cpu_need_resched.9,v 1.5 2007/05/17 15:06:25 yamt 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 May 18, 2007 38.Dt CPU_NEED_RESCHED 9 39.Os 40.Sh NAME 41.Nm cpu_need_resched 42.Nd context switch notification 43.Sh SYNOPSIS 44.In sys/cpu.h 45.Ft void 46.Fn cpu_need_resched "struct cpu_info *ci" "int flags" 47.Sh DESCRIPTION 48The 49.Fn cpu_need_resched 50function is the machine-independent interface for the scheduler to 51notify machine-dependent code that a context switch from the current 52LWP, on the cpu 53.Fa ci , 54is required. 55This event may occur if a higher priority LWP appears on the run 56queue or if the current LWP has exceeded its time slice. 57.Pp 58If 59.Dv 60RESCHED_IMMED 61flag is specified in 62.Fa flags , 63machine-dependent code should make a context switch happen as soon as possible. 64In that case, for example, if 65.Fa ci 66is not the current processor, 67.Fn cpu_need_resched 68typically issues an inter processor call to the processor to make it 69notice the need of a context switch as soon as possible. 70.Sh EXAMPLES 71Specifically, the 72.Fn cpu_need_resched 73function will perform the following operations: 74.Bl -bullet -offset indent 75.It 76Set a per-processor flag which is checked by 77.Xr userret 9 78when returning to user-mode execution. 79.It 80Post an asynchronous software trap (AST). 81.It 82Send an inter processor interrupt to wake up 83.Fn cpu_idle . 84.El 85.Sh SEE ALSO 86.Xr scheduler 9 , 87.Xr userret 9 88