linux-kernel - Re: [PATCH 1/6] [watchdog] combine nmi

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Date:	Wed, 21 Apr 2010 13:50:21 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	mingo@...e.hu, peterz@...radead.org, gorcunov@...il.com,
	aris@...hat.com, linux-kernel@...r.kernel.org,
	randy.dunlap@...cle.com
Subject: Re: [PATCH 1/6] [watchdog] combine nmi_watchdog and softlockup

On Wed, Apr 21, 2010 at 07:27:33PM +0200, Frederic Weisbecker wrote:
> Some minor things:
> 
> 
> On Tue, Apr 20, 2010 at 11:23:58AM -0400, Don Zickus wrote:
> > +#ifdef CONFIG_PERF_EVENTS_NMI
> > +struct perf_event_attr wd_hw_attr = {
> > +	.type		= PERF_TYPE_HARDWARE,
> > +	.config		= PERF_COUNT_HW_CPU_CYCLES,
> > +	.size		= sizeof(struct perf_event_attr),
> > +	.pinned		= 1,
> > +	.disabled	= 1,
> > +};
> 
> 
> 
> Shouldn't it be static?

yes.  thanks.

> 
> 
> > +
> > +/* Callback function for perf event subsystem */
> > +void watchdog_overflow_callback(struct perf_event *event, int nmi,
> > +		 struct perf_sample_data *data,
> > +		 struct pt_regs *regs)
> > +{
> > +	int this_cpu = smp_processor_id();
> > +	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
> > +	char warn = per_cpu(watchdog_warn, this_cpu);
> 
> 
> 
> You can use __get_cpu_var() here

well, I already have this_cpu and need it later, I figured I would just
use it with per_cpu and save _get_cpu_var the work of re-running
smp_processor_id().

> 
> 
> 
> > +
> > +	if (touch_ts == 0) {
> > +		__touch_watchdog();
> > +		return;
> > +	}
> > +
> > +	/* check for a hardlockup
> > +	 * This is done by making sure our timer interrupt
> > +	 * is incrementing.  The timer interrupt should have
> > +	 * fired multiple times before we overflow'd.  If it hasn't
> > +	 * then this is a good indication the cpu is stuck
> > +	 */
> > +	if (is_hardlockup(this_cpu)) {
> > +		/* only print hardlockups once */
> > +		if (warn & HARDLOCKUP)
> > +			return;
> > +
> > +		if (hardlockup_panic)
> > +			panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
> > +		else
> > +			WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
> > +
> > +		per_cpu(watchdog_warn, this_cpu) = warn | HARDLOCKUP;
> 
> 
> 
> and here.

same arguement as above.

> 
> 
> 
> > +		return;
> > +	}
> > +
> > +	per_cpu(watchdog_warn, this_cpu) = warn & ~HARDLOCKUP;
> > +	return;
> > +}
> > +static void watchdog_interrupt_count(void)
> > +{
> > +	__get_cpu_var(hrtimer_interrupts)++;
> > +}
> > +#else
> > +static void watchdog_interrupt_count(void) { return; }
> 
> 
> 
> Off case should be inline (although gcc will probably inline it by itself)

yup.  thanks.

> 
> 
> 
> > +#endif /* CONFIG_PERF_EVENTS_NMI */
> > +
> > +/* watchdog kicker functions */
> > +static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
> > +{
> > +	int this_cpu = smp_processor_id();
> > +	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
> 
> 
> 
> __get_cpu_var

again same as above.

Thanks for the review.

Cheers,
Don
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