perf, cpu hotplug: Use cached value of smp_processor_id()

The perf_cpu_notifier() macro invokes smp_processor_id()
multiple times. Optimize it by using a local variable.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: peterz@infradead.org
Cc: acme@ghostprotocols.net
Link: http://lkml.kernel.org/r/20121016075817.3572.76733.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/perf_event.h

@@ -803,15 +803,16 @@ static inline void perf_event_task_tick(void)				{ }
 do {									\
 	static struct notifier_block fn##_nb __cpuinitdata =		\
 		{ .notifier_call = fn, .priority = CPU_PRI_PERF };	\
+	unsigned long cpu = smp_processor_id();				\
 	unsigned long flags;						\
 	fn(&fn##_nb, (unsigned long)CPU_UP_PREPARE,			\
-		(void *)(unsigned long)smp_processor_id());		\
+		(void *)(unsigned long)cpu);				\
 	local_irq_save(flags);						\
 	fn(&fn##_nb, (unsigned long)CPU_STARTING,			\
-		(void *)(unsigned long)smp_processor_id());		\
+		(void *)(unsigned long)cpu);				\
 	local_irq_restore(flags);					\
 	fn(&fn##_nb, (unsigned long)CPU_ONLINE,				\
-		(void *)(unsigned long)smp_processor_id());		\
+		(void *)(unsigned long)cpu);				\
 	register_cpu_notifier(&fn##_nb);				\
 } while (0)