linux-kernel - Re: [tip:perf/urgent] perf, x86: Catch spurious interrupts after disabling counters

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Message-ID: <20100929190114.GZ26290@redhat.com>
Date:	Wed, 29 Sep 2010 15:01:14 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Robert Richter <robert.richter@....com>,
	Stephane Eranian <eranian@...gle.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"ying.huang@...el.com" <ying.huang@...el.com>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"ming.m.lin@...el.com" <ming.m.lin@...el.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...e.hu" <mingo@...e.hu>
Subject: Re: [tip:perf/urgent] perf, x86: Catch spurious interrupts after
 disabling counters

On Wed, Sep 29, 2010 at 07:27:45PM +0400, Cyrill Gorcunov wrote:
> 
>   Cyrill
> ---
> Subject: [PATCH -tip] perf, x86: Handle in flight IRQs on P4 platform
> 
> Stephane reported we've missed to guard P4 platform
> against spurious in-flight performance IRQs. Fix it.
> 
> [ the patch is a complement to commit 63e6be6d98e1 ]
> 
> Reported-by: Stephane Eranian <eranian@...gle.com>
> Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> CC: Robert Richter <robert.richter@....com>
> CC: Lin Ming <ming.m.lin@...el.com>

Thanks Cyrill,

I'll test it quickly and try to send it to Ingo.

Cheers,
Don
> ---
>  arch/x86/kernel/cpu/perf_event_p4.c |    6 +++++-
>  1 file changed, 5 insertions(+), 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
> @@ -904,8 +904,12 @@ static int p4_pmu_handle_irq(struct pt_r
>  	for (idx = 0; idx < x86_pmu.num_counters; idx++) {
>  		int overflow;
>  
> -		if (!test_bit(idx, cpuc->active_mask))
> +		if (!test_bit(idx, cpuc->active_mask)) {
> +			/* catch in-flight IRQs */
> +			if (__test_and_clear_bit(idx, cpuc->running))
> +				handled++;
>  			continue;
> +		}
>  
>  		event = cpuc->events[idx];
>  		hwc = &event->hw;
--
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