[MIPS] Add smp_call_function_single()

In the other archs, there is more factoring of smp call code, and more care
in the use of get_cpu(). That can be a follow-up MIPS patch.
Signed-off-by: Peter Watkins <pwatkins@sicortex.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/smp.c

@@ -194,6 +194,61 @@ void smp_call_function_interrupt(void)
 	}
 }
 
+int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
+			     int retry, int wait)
+{
+	struct call_data_struct data;
+	int me;
+
+	/*
+	 * Can die spectacularly if this CPU isn't yet marked online
+	 */
+	if (!cpu_online(cpu))
+		return 0;
+
+	me = get_cpu();
+	BUG_ON(!cpu_online(me));
+
+	if (cpu == me) {
+		local_irq_disable();
+		func(info);
+		local_irq_enable();
+		put_cpu();
+		return 0;
+	}
+
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
+	data.func = func;
+	data.info = info;
+	atomic_set(&data.started, 0);
+	data.wait = wait;
+	if (wait)
+		atomic_set(&data.finished, 0);
+
+	spin_lock(&smp_call_lock);
+	call_data = &data;
+	smp_mb();
+
+	/* Send a message to the other CPU */
+	core_send_ipi(cpu, SMP_CALL_FUNCTION);
+
+	/* Wait for response */
+	/* FIXME: lock-up detection, backtrace on lock-up */
+	while (atomic_read(&data.started) != 1)
+		barrier();
+
+	if (wait)
+		while (atomic_read(&data.finished) != 1)
+			barrier();
+	call_data = NULL;
+	spin_unlock(&smp_call_lock);
+
+	put_cpu();
+	return 0;
+}
+
 static void stop_this_cpu(void *dummy)
 {
 	/*