[PATCH 3.12 27/98] perf, nmi: Fix unknown NMI warning

[Jiri Slaby]

From: Markus Metzger <markus.t.metzger@xxxxxxxxx>

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@xxxxxxxxxx
Cc: peterz@xxxxxxxxxxxxx
Cc: mingo@xxxxxxxxxx
Signed-off-by: Markus Metzger <markus.t.metzger@xxxxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1392425048-5309-1-git-send-email-andi@xxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 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