linux-kernel - Re: [patch] KVM, hotplug: export register_cpu

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Message-ID: <20070207091913.GA15384@elte.hu>
Date:	Wed, 7 Feb 2007 10:19:13 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Avi Kivity <avi@...ranet.com>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org
Subject: Re: [patch] KVM, hotplug: export register_cpu_notifier


* Avi Kivity <avi@...ranet.com> wrote:

> >-#ifdef CONFIG_HOTPLUG_CPU
> >-
> > EXPORT_SYMBOL(register_cpu_notifier);
> > 
> >+#ifdef CONFIG_HOTPLUG_CPU
> >+
> > void unregister_cpu_notifier(struct notifier_block *nb)
> > {
> > 	mutex_lock(&cpu_add_remove_lock);
> >  
> 
> This is broken: register_cpu_notifier() is __cpuinit, which means it 
> disappears at module time if !CONFIG_CPU_HOTPLUG.
> 
> I submitted a hackaround to Andrew some time ago with the suspend 
> patchset.

ok. What does your patch do - turns it into an inline? I fixed it up in 
-rt via the patch below.

	Ingo

---------------------->
Subject: [patch] KVM: export register_cpu_notifier
From: Ingo Molnar <mingo@...e.hu>

KVM-trunk uses register_cpu_notifier() but it's not exported
on CONFIG_HOTPLUG_CPU. Make it a nop inline.

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 include/linux/cpu.h |    6 +++++-
 kernel/cpu.c        |    4 ----
 2 files changed, 5 insertions(+), 5 deletions(-)

Index: linux/include/linux/cpu.h
===================================================================
--- linux.orig/include/linux/cpu.h
+++ linux/include/linux/cpu.h
@@ -49,10 +49,14 @@ 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
+static inline int register_cpu_notifier(struct notifier_block *nb)
+{
+	return 0;
+}
 static inline void unregister_cpu_notifier(struct notifier_block *nb)
 {
 }
Index: linux/kernel/cpu.c
===================================================================
--- linux.orig/kernel/cpu.c
+++ linux/kernel/cpu.c
@@ -63,8 +63,6 @@ void unlock_cpu_hotplug(void)
 }
 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
 
-#endif	/* CONFIG_HOTPLUG_CPU */
-
 /* Need to know about CPUs going up/down? */
 int __cpuinit register_cpu_notifier(struct notifier_block *nb)
 {
@@ -75,8 +73,6 @@ int __cpuinit register_cpu_notifier(stru
 	return ret;
 }
 
-#ifdef CONFIG_HOTPLUG_CPU
-
 EXPORT_SYMBOL(register_cpu_notifier);
 
 void unregister_cpu_notifier(struct notifier_block *nb)
-
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