linux-kernel - Re: [PATCH -v2 2/2] x86, cpu hotplug: Fix cpu bringup concurrency issue

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Date:	Wed, 18 Aug 2010 21:28:58 +0200
From:	Borislav Petkov <bp@...64.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Joerg Roedel <joro@...tes.org>,
	"Roedel, Joerg" <Joerg.Roedel@....com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Herrmann3, Andreas" <Andreas.Herrmann3@....com>,
	"Seidel, Conny" <Conny.Seidel@....com>,
	"Sarathy, Bhavna" <Bhavna.Sarathy@....com>,
	"greg@...ah.com" <greg@...ah.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v2 2/2] x86, cpu hotplug: Fix cpu bringup concurrency
 issue

From: "H. Peter Anvin" <hpa@...or.com>
Date: Wed, Aug 18, 2010 at 03:03:33PM -0400

> On 08/16/2010 05:39 AM, Borislav Petkov wrote:
> > 
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index dcb0593..1598663 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -58,6 +58,7 @@ config X86
> >  	select ANON_INODES
> >  	select HAVE_ARCH_KMEMCHECK
> >  	select HAVE_USER_RETURN_NOTIFIER
> > +	select ARCH_CPU_PROBE_RELEASE
> >  
> 
> warning: (X86) selects ARCH_CPU_PROBE_RELEASE which has unmet direct
> dependencies (HOTPLUG_CPU)

well I got 

+config ARCH_CPU_PROBE_RELEASE
+       def_bool y
+       depends on HOTPLUG_CPU

but I guess ARCH_CPU_PROBE_RELEASE gets selected still. Why isn't that
"depends on" forcing it, I guess select is stronger.

> ... and build failure when compiling without CONFIG_HOTPLUG_CPU.

This hunk fixes the !CONFIG_HOTPLUG_CPU build here but I should've
caught it earlier, shame on me. Sorry for the inconvenience, can you
please drop this second patch for now, I'll send you a revised version
tomorrow.

Thanks.

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 251acea..273cfb9 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -261,7 +261,7 @@ int __init cpu_dev_init(void)
 }
 
 static struct sysdev_class_attribute *cpu_sysdev_class_attrs[] = {
-#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+#if defined(CONFIG_ARCH_CPU_PROBE_RELEASE) && defined(CONFIG_HOTPLUG_CPU)
        &attr_probe,
        &attr_release,
 #endif


-- 
Regards/Gruss,
Boris.

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