[tip:perf/urgent] perf, x86: Handle in flight NMIs on P4 platform

[tip-bot for Cyrill Gorcunov]

Commit-ID:  03e22198d2379ffa746c9ea332fbb1f094f9423b
Gitweb:     http://git.kernel.org/tip/03e22198d2379ffa746c9ea332fbb1f094f9423b
Author:     Cyrill Gorcunov <gorcunov@xxxxxxxxx>
AuthorDate: Wed, 29 Sep 2010 23:01:38 -0400
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 30 Sep 2010 09:17:59 +0200

perf, x86: Handle in flight NMIs on P4 platform

Stephane reported we've forgot to guard the P4 platform
against spurious in-flight performance IRQs. Fix it.

This fixes potential spurious 'dazed and confused' NMI
messages.

Reported-by: Stephane Eranian <eranian@xxxxxxxxxx>
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Signed-off-by: Don Zickus <dzickus@xxxxxxxxxx>
Cc: fweisbec@xxxxxxxxx
Cc: peterz@xxxxxxxxxxxxx
Cc: Robert Richter <robert.richter@xxxxxxx>
Cc: Lin Ming <ming.m.lin@xxxxxxxxx>
LKML-Reference: <1285815698-4298-1-git-send-email-dzickus@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 arch/x86/kernel/cpu/perf_event_p4.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c
index b560db3..2490151 100644
--- a/arch/x86/kernel/cpu/perf_event_p4.c
+++ b/arch/x86/kernel/cpu/perf_event_p4.c
@@ -660,8 +660,12 @@ static int p4_pmu_handle_irq(struct pt_regs *regs)
 	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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