linux-kernel - Re: [RFC PATCH 3/5] x86: add a sysctl parameter to panic on stack overflow

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Date:	Thu, 17 Nov 2011 11:00:21 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	HAYASAKA Mitsuo <mitsuo.hayasaka.hu@...achi.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Randy Dunlap <rdunlap@...otime.net>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	yrl.pp-manager.tt@...achi.com
Subject: Re: [RFC PATCH 3/5] x86: add a sysctl parameter to panic on stack
 overflow

On Thu, Nov 17, 2011 at 04:11:07PM +0900, HAYASAKA Mitsuo wrote:
> Hi Konrad,
> 
> >> diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
> >> index 530cfd0..d720813 100644
> >> --- a/arch/x86/kernel/irq_64.c
> >> +++ b/arch/x86/kernel/irq_64.c
> >> @@ -20,6 +20,8 @@
> >>  #include <asm/idle.h>
> >>  #include <asm/apic.h>
> >>  
> >> +int sysctl_panic_on_stackoverflow;
> > __read_mostly
> 
> I don't mind if I add __read_mostly here, but I think it's not
> necessary because this variable is seldom read as well.

The definition of __read_mostly is that it moves this variable to a cold cache area.
Which is what you want.

> 
> 
> >> diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
> >> index 6318b51..24fc654 100644
> >> --- a/kernel/sysctl_binary.c
> >> +++ b/kernel/sysctl_binary.c
> >> @@ -137,6 +137,7 @@ static const struct bin_table bin_kern_table[] = {
> >>  	{ CTL_INT,	KERN_COMPAT_LOG,		"compat-log" },
> >>  	{ CTL_INT,	KERN_MAX_LOCK_DEPTH,		"max_lock_depth" },
> >>  	{ CTL_INT,	KERN_PANIC_ON_NMI,		"panic_on_unrecovered_nmi" },
> >> +	{ CTL_INT,	KERN_PANIC_ON_STACKOVERFLOW,	"panic_on_stackoverflow" },
> > This shouldn't be wrapped in the #ifdef?
> >
> 
> It seems that we do not need to add this entry to bin_kern_table[]
> according to the following information and patch series:
> 
> [Removing binary sysctl]
> 	http://lwn.net/Articles/361453/
> 
> [Removal of binary sysctl support]
> 	http://lwn.net/Articles/361001/
> 
> So, I'm going to remove this changes for sysctl.h and sysctl_binary.c.

<nods>
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