cpu_need_resched.9 revision 1.5
$NetBSD: cpu_need_resched.9,v 1.5 2007/05/17 15:06:25 yamt 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 May 18, 2007 .Dt CPU_NEED_RESCHED 9 .Os .Sh NAME .Nm cpu_need_resched .Nd context switch notification .Sh SYNOPSIS n sys/cpu.h .Ft void .Fn cpu_need_resched "struct cpu_info *ci" "int flags" .Sh DESCRIPTION The .Fn cpu_need_resched function is the machine-independent interface for the scheduler to notify machine-dependent code that a context switch from the current LWP, on the cpu .Fa ci , is required. This event may occur if a higher priority LWP appears on the run queue or if the current LWP has exceeded its time slice.
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 May 18, 2007 .Dt CPU_NEED_RESCHED 9 .Os .Sh NAME .Nm cpu_need_resched .Nd context switch notification .Sh SYNOPSIS n sys/cpu.h .Ft void .Fn cpu_need_resched "struct cpu_info *ci" "int flags" .Sh DESCRIPTION The .Fn cpu_need_resched function is the machine-independent interface for the scheduler to notify machine-dependent code that a context switch from the current LWP, on the cpu .Fa ci , is required. This event may occur if a higher priority LWP appears on the run queue or if the current LWP has exceeded its time slice.
p If .Dv RESCHED_IMMED flag is specified in .Fa flags , machine-dependent code should make a context switch happen as soon as possible. In that case, for example, if .Fa ci is not the current processor, .Fn cpu_need_resched typically issues an inter processor call to the processor to make it notice the need of a context switch as soon as possible. .Sh EXAMPLES Specifically, the .Fn cpu_need_resched function will perform the following operations: l -bullet -offset indent t Set a per-processor flag which is checked by .Xr userret 9 when returning to user-mode execution. t Post an asynchronous software trap (AST). t Send an inter processor interrupt to wake up .Fn cpu_idle . .El .Sh SEE ALSO .Xr scheduler 9 , .Xr userret 9