linux-kernel - Re: [PATCH] perf, x86: Add hw_watchdog_set_attr() in a sake of nmi-watchdog on P4

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Date:	Tue, 28 Jun 2011 20:11:10 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Don Zickus <dzickus@...hat.com>, Ingo Molnar <mingo@...hat.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf, x86: Add hw_watchdog_set_attr() in a sake of
 nmi-watchdog on P4

On Tue, Jun 28, 2011 at 05:53:31PM +0200, Stephane Eranian wrote:
> Cyrill,
> 
> #ifdef CONFIG_HARDLOCKUP_DETECTOR
> +void __weak hw_nmi_watchdog_set_attr(struct perf_event_attr *wd_attr) { }
> 
> The weak function has to remain inside the #ifdef. Remember it's just an
> override in case you cannot using the generic cycle event. It is only needed
> when you have the HARDLOCK detector, i.e., are using the PMU to detect
> deadlocks.
> 
> I suspect P4 may be the only one so far which exhibited a problem there.
> 

heh ;) Guys, maybe we're talking about different things? Don, when you said
"Though I do wonder about this call in the watchdog" you meant the 

 	wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
-->	hw_nmi_watchdog_set_attr(wd_attr);

itself? Ie you suspect some different point where to call it?

When I said not a "best place" I meant about __weak function bare implementation
placed that near to call (which is looked somehow suspicious for me from overall
code structure), but I didn't mean the call sequence itself ;)

	Cyrill
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