i386: Allow smp_call_function_single() to current cpu

This removes the requirement for callers to get_cpu() to check in simple
cases.

Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/arch/i386/kernel/smpcommon.c b/arch/i386/kernel/smpcommon.c
index 1868ae1..bbfe85a 100644
--- a/arch/i386/kernel/smpcommon.c
+++ b/arch/i386/kernel/smpcommon.c
@@ -47,7 +47,7 @@
 EXPORT_SYMBOL(smp_call_function);
 
 /**
- * smp_call_function_single - Run a function on another CPU
+ * smp_call_function_single - Run a function on a specific CPU
  * @cpu: The target CPU.  Cannot be the calling CPU.
  * @func: The function to run. This must be fast and non-blocking.
  * @info: An arbitrary pointer to pass to the function.
@@ -66,9 +66,11 @@
 	int ret;
 	int me = get_cpu();
 	if (cpu == me) {
-		WARN_ON(1);
+		local_irq_disable();
+		func(info);
+		local_irq_enable();
 		put_cpu();
-		return -EBUSY;
+		return 0;
 	}
 
 	ret = smp_call_function_mask(cpumask_of_cpu(cpu), func, info, wait);