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Subject[PATCH 3.12 27/98] perf, nmi: Fix unknown NMI warning
Date
From: Markus Metzger <markus.t.metzger@intel.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit a3ef2229c94ff70998724cb64b9cb4c77db9e950 upstream.

When using BTS on Core i7-4*, I get the below kernel warning.

$ perf record -c 1 -e branches:u ls
Message from syslogd@labpc1501 at Nov 11 15:49:25 ...
kernel:[ 438.317893] Uhhuh. NMI received for unknown reason 31 on CPU 2.

Message from syslogd@labpc1501 at Nov 11 15:49:25 ...
kernel:[ 438.317920] Do you have a strange power saving mode enabled?

Message from syslogd@labpc1501 at Nov 11 15:49:25 ...
kernel:[ 438.317945] Dazed and confused, but trying to continue

Make intel_pmu_handle_irq() take the full exit path when returning early.

Cc: eranian@google.com
Cc: peterz@infradead.org
Cc: mingo@kernel.org
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1392425048-5309-1-git-send-email-andi@firstfloor.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
arch/x86/kernel/cpu/perf_event_intel.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index b400d0be5b03..d2080aa4322a 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1341,10 +1341,8 @@ static int intel_pmu_handle_irq(struct pt_regs *regs)
intel_pmu_disable_all();
handled = intel_pmu_drain_bts_buffer();
status = intel_pmu_get_status();
- if (!status) {
- intel_pmu_enable_all(0);
- return handled;
- }
+ if (!status)
+ goto done;

loops = 0;
again:
--
2.8.1
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