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

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Date:	Wed, 29 Sep 2010 19:27:45 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Robert Richter <robert.richter@....com>
Cc:	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>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"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 05:12:53PM +0200, Robert Richter wrote:
> On 29.09.10 17:01:40, Robert Richter wrote:
> > Right, I wasn't remembering correctly, it was P6 and core. And yes, P4
> > requires the fix. Will send a patch for this.
> 
> Ok, Cyrill is sending the patch.
> 
> Thanks,
> 
> -Robert
>

Managed to implement it earlier then I thought.

  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>
---
 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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