From 47e627bc8c9a70392d2049e6af5bd55fae61fe53 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Mon, 12 Feb 2007 00:54:43 -0800 Subject: [PATCH 1/1] [PATCH] hotplug: Allow modules to use the cpu hotplug notifiers even if !CONFIG_HOTPLUG_CPU The following patchset allows a host with running virtual machines to be suspended and, on at least a subset of the machines tested, resumed. Note that this is orthogonal to suspending and resuming an individual guest to a file. A side effect of implementing suspend/resume is that cpu hotplug is now supported. This should please the owners of big iron. This patch: KVM wants the cpu hotplug notifications, both for cpu hotplug itself, but more commonly for host suspend/resume. In order to avoid extensive #ifdefs, provide stubs when CONFIG_CPU_HOTPLUG is not defined. In all, we have four cases: - UP: register and unregister stubbed out - SMP+hotplug: full register and unregister - SMP, no hotplug, core: register as __init, unregister stubbed (cpus are brought up during core initialization) - SMP, no hotplug, module: register and unregister stubbed out (cpus cannot be brought up during module lifetime) Signed-off-by: Avi Kivity Cc: Ingo Molnar Cc: Rusty Russell Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cpu.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index bfb520212d71..769ddc6df492 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -49,10 +49,20 @@ struct notifier_block; #ifdef CONFIG_SMP /* Need to know about CPUs going up/down? */ -extern int register_cpu_notifier(struct notifier_block *nb); #ifdef CONFIG_HOTPLUG_CPU +extern int register_cpu_notifier(struct notifier_block *nb); extern void unregister_cpu_notifier(struct notifier_block *nb); #else + +#ifndef MODULE +extern int register_cpu_notifier(struct notifier_block *nb); +#else +static inline int register_cpu_notifier(struct notifier_block *nb) +{ + return 0; +} +#endif + static inline void unregister_cpu_notifier(struct notifier_block *nb) { } -- 2.39.2