Re: [RFC 6/6] x86, NMI, Remove do_nmi_callback logic

Huang Ying
2010-09-13T02:27:20Z

On Sat, 2010-09-11 at 00:13 +0800, Don Zickus wrote:
> 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?

Is it planned to remove old NMI watchdog implementation in near future?

If it is not, I think it is better to document/comment the two
implementation more explicitly, maybe in nmi_watchdog_tick() comments. I
suspect nmi_watchdog_tick() wrapped with "!
defined(CONFIG_LOCKUP_DETECTOR)" will make people more confused.

Best Regards,
Huang Ying