[PATCH 2/4] perf_counter: fix nmi-watchdog interaction

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

[-- Attachment #1: perf_counter-fix-nmi.patch --]
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When we don't have any perf-counters active, don't act like we know
what the NMI is for.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 arch/x86/kernel/cpu/perf_counter.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-2.6/arch/x86/kernel/cpu/perf_counter.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_counter.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_counter.c
@@ -891,6 +891,9 @@ perf_counter_nmi_handler(struct notifier
 	struct pt_regs *regs;
 	int ret;
 
+	if (!atomic_read(&num_counters))
+		return NOTIFY_DONE;
+
 	switch (cmd) {
 	case DIE_NMI:
 	case DIE_NMI_IPI:

--