linux-kernel - Re: [PATCH -tip] perf, x86: P4 PMU - Don't forget to clear cpuc->active

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Date:	Thu, 21 Apr 2011 14:34:08 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
Cc:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>,
	Don Zickus <dzickus@...hat.com>
Subject: Re: [PATCH -tip] perf, x86: P4 PMU - Don't forget to clear
 cpuc->active_mask on overflow

On Wed, 2011-04-20 at 23:13 +0800, Cyrill Gorcunov wrote:
> It's not enough to simply disable event on overflow the cpuc->active_mask
> should be cleared as well otherwise counter may stall in "active" even
> in real being already disabled (which potentially may lead to the situation
> that user may not use this counter further).
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> ---
> 
> Ming, iirc you were testing this one, but without unknown nmi fix. So
> patch from Don should fix unknown nmi issue, please give this patch a
> shot again if you have some time (Don's patch is here
> https://lkml.org/lkml/2011/4/18/404 but I think you have it already in mailbox).

Tested the 2 patches with nmi watchdog enabled and no unknown nmi was
seen when running perf tool.

Nice.

Thanks,
Lin Ming

> 
>  arch/x86/kernel/cpu/perf_event_p4.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c
> =====================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_p4.c
> +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c
> @@ -946,7 +946,7 @@ static int p4_pmu_handle_irq(struct pt_r
>  		if (!x86_perf_event_set_period(event))
>  			continue;
>  		if (perf_event_overflow(event, 1, &data, regs))
> -			p4_pmu_disable_event(event);
> +			x86_pmu_stop(event, 0);
>  	}
> 
>  	if (handled) {
> 


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