linux-kernel - Re: [RFC 6/6] x86, NMI, Remove do_nmi

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Message-ID: <20100910161319.GI4879@redhat.com>
Date:	Fri, 10 Sep 2010 12:13:19 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>
Subject: Re: [RFC 6/6] x86, NMI, Remove do_nmi_callback logic

On Fri, Sep 10, 2010 at 10:51:05AM +0800, Huang Ying wrote:
>  
> +#if defined(CONFIG_X86_LOCAL_APIC) && !defined(CONFIG_LOCKUP_DETECTOR)
> +extern int nmi_watchdog_tick(struct pt_regs *regs);
> +#else
> +static inline int nmi_watchdog_tick(struct pt_regs *regs)
> +{
> +	return 0;
> +}
> +#endif
> +
>  extern atomic_t nmi_active;
>  extern unsigned int nmi_watchdog;
>  #define NMI_NONE	0

<snip>

> @@ -421,12 +429,8 @@ static notrace __kprobes void default_do
>  	}
>  	raw_spin_unlock(&nmi_reason_lock);
>  
> -#if defined(CONFIG_X86_LOCAL_APIC) && !defined(CONFIG_LOCKUP_DETECTOR)
> -	if (nmi_watchdog_tick(regs, reason))
> -		return;
> -	if (do_nmi_callback(regs, smp_processor_id()))
> +	if (nmi_watchdog_tick(regs))
>  		return;
> -#endif
>  
>  	if (notify_die(DIE_NMIUNKNOWN, "nmi_unknown", regs, reason, 2, SIGINT)
>  	    == NOTIFY_STOP)

I wonder if these two chunks are going to confuse people when they read
the code.  The old nmi watchdog exists in the arch/x86 area but the new
nmi watchdog code is now in kernel/watchdog.c.

If someone sees nmi_watchdog_tick() here will they assume the nmi watchdog
code is still inside arch/x86?

I would suggest keep it wrapped with CONFIG_LOCKUP_DETECTOR to make it
obvious.  Thoughts?

Cheers,
Don
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