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

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Date:	Wed, 21 Apr 2010 19:27:33 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Don Zickus <dzickus@...hat.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

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?


> +
> +/* 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



> +
> +	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.



> +		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)



> +#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

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