[POWERPC] make pmf irq_client functions safe against pmf interrupts coming in

This fixes the pmf irq_client functions to be safe against pmf interrupts coming
in while a client is registered/unregistered.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/powermac/pfunc_core.c

@@ -871,10 +871,17 @@ int pmf_register_irq_client(struct device_node *target,
 	spin_unlock_irqrestore(&pmf_lock, flags);
 	if (func == NULL)
 		return -ENODEV;
+
+	/* guard against manipulations of list */
 	mutex_lock(&pmf_irq_mutex);
 	if (list_empty(&func->irq_clients))
 		func->dev->handlers->irq_enable(func);
+
+	/* guard against pmf_do_irq while changing list */
+	spin_lock_irqsave(&pmf_lock, flags);
 	list_add(&client->link, &func->irq_clients);
+	spin_unlock_irqrestore(&pmf_lock, flags);
+
 	client->func = func;
 	mutex_unlock(&pmf_irq_mutex);
 
@@ -885,12 +892,19 @@ EXPORT_SYMBOL_GPL(pmf_register_irq_client);
 void pmf_unregister_irq_client(struct pmf_irq_client *client)
 {
 	struct pmf_function *func = client->func;
+	unsigned long flags;
 
 	BUG_ON(func == NULL);
 
+	/* guard against manipulations of list */
 	mutex_lock(&pmf_irq_mutex);
 	client->func = NULL;
+
+	/* guard against pmf_do_irq while changing list */
+	spin_lock_irqsave(&pmf_lock, flags);
 	list_del(&client->link);
+	spin_unlock_irqrestore(&pmf_lock, flags);
+
 	if (list_empty(&func->irq_clients))
 		func->dev->handlers->irq_disable(func);
 	mutex_unlock(&pmf_irq_mutex);