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

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Message-ID: <20100421204926.GW15159@redhat.com>
Date:	Wed, 21 Apr 2010 16:49:26 -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 10:24:21PM +0200, Frederic Weisbecker wrote:
> On Wed, Apr 21, 2010 at 01:50:21PM -0400, Don Zickus wrote:
> > 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().
> 
> 
> 
> This is more about code clarity in fact. per_cpu() suggests we are
> fetching something from another cpu.

ah gotcha.

> 
> This is a very minor issue though.

I have no problem changing it.

Cheers,
Don
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