On Thu, Oct 09, 2014 at 12:31:43PM +0200, Pavel Machek wrote:

Hi!

quoted

+/**
+ *	register_poweroff_handler_simple - Register function to be called to power off
+ *					   the system
+ *	@handler:	Function to be called to power off the system
+ *	@priority:	Handler priority. For priority guidelines see
+ *			register_poweroff_handler.
+ *
+ *	This is a simplified version of register_poweroff_handler. It does not
+ *	take a notifier as argument, but a function pointer. The function
+ *	registers a poweroff handler with specified priority. Poweroff
+ *	handlers registered with this function can not be unregistered,
+ *	and only a single poweroff handler can be installed using it.
+ *
+ *	This function must not be called from modules and is therefore
+ *	not exported.
+ *
+ *	Returns -EBUSY if a poweroff handler has already been registered
+ *	using register_poweroff_handler_simple. Otherwise returns zero,
+ *	since atomic_notifier_chain_register() currently always returns zero.
+ */
+int register_poweroff_handler_simple(void (*handler)(void), int priority)
+{
+	char symname[KSYM_NAME_LEN];
+
+	if (poweroff_handler_data.handler) {
+		lookup_symbol_name((unsigned long)poweroff_handler_data.handler,
+				   symname);
+		pr_warn("Poweroff function already registered (%s)", symname);
+		lookup_symbol_name((unsigned long)handler, symname);
+		pr_cont(", cannot register %s\n", symname);
+		return -EBUSY;
+	}

Dunno, are you maybe overdoing the debugging infrastructure a bit?
This is not going to happen in production, and if it does happen,
developer can look the symbol name himself.

On the other side, I don't think it hurts to have that message.
Anyway, I'll use %ps as suggested by Geert.

Guenter