generic-ipi: cleanup for generic_smp_call_function_interrupt()

Use smp_processor_id() instead of get_cpu() and put_cpu() in
generic_smp_call_function_interrupt(), It's no need to disable preempt,
because we must call generic_smp_call_function_interrupt() with interrupts
disabled.

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/smp.c

@@ -171,7 +171,7 @@ void generic_exec_single(int cpu, struct call_single_data *data, int wait)
 void generic_smp_call_function_interrupt(void)
 {
 	struct call_function_data *data;
-	int cpu = get_cpu();
+	int cpu = smp_processor_id();
 
 	/*
 	 * Shouldn't receive this interrupt on a cpu that is not yet online.
@@ -212,7 +212,6 @@ void generic_smp_call_function_interrupt(void)
 		csd_unlock(&data->csd);
 	}
 
-	put_cpu();
 }
 
 /*