netdev - Re: [RFC next-next v2 1/5] net: marvell: prestera: Add driver for Prestera family ASIC devices

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Message-ID: <20200512150714.GE31516@plvision.eu>
Date:   Tue, 12 May 2020 18:07:14 +0300
From:   Vadym Kochan <vadym.kochan@...ision.eu>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Oleksandr Mazur <oleksandr.mazur@...ision.eu>,
        Serhiy Boiko <serhiy.boiko@...ision.eu>,
        Serhiy Pshyk <serhiy.pshyk@...ision.eu>,
        Volodymyr Mytnyk <volodymyr.mytnyk@...ision.eu>,
        Taras Chornyi <taras.chornyi@...ision.eu>,
        Andrii Savka <andrii.savka@...ision.eu>,
        Jiri Pirko <jiri@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>,
        Andrew Lunn <andrew@...n.ch>,
        Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Subject: Re: [RFC next-next v2 1/5] net: marvell: prestera: Add driver for
 Prestera family ASIC devices

On Tue, May 12, 2020 at 05:03:06PM +0200, Jiri Pirko wrote:
> Tue, May 12, 2020 at 04:53:52PM CEST, vadym.kochan@...ision.eu wrote:
> >On Mon, May 11, 2020 at 12:32:22PM +0200, Jiri Pirko wrote:
> >
> >[...]
> >
> >> 
> >> This is RCU list. Treat it accordingly.
> >> 
> >> 
> >> >+	spin_unlock(&sw->ports_lock);
> >> 
> >> I don't follow, why do you need to protect the list by spinlock here?
> >> More to that, why do you need the port_list reader-writer
> >> protected (by rcu)? Is is possible that you add/remove port in the same
> >> time packets are flying in?
> >> 
> >> If yes, you need to ensure the structs are in the memory (free_rcu,
> >> synchronize_rcu). But I believe that you should disable that from
> >> happening in HW.
> >> 
> >> 
> >> >+
> >
> >[...]
> >
> >> >+
> >> >+static int prestera_switch_init(struct prestera_switch *sw)
> >> >+{
> >> >+	int err;
> >> >+
> >> >+	err = prestera_hw_switch_init(sw);
> >> >+	if (err) {
> >> >+		dev_err(prestera_dev(sw), "Failed to init Switch device\n");
> >> >+		return err;
> >> >+	}
> >> >+
> >> >+	memcpy(sw->base_mac, base_mac_addr, sizeof(sw->base_mac));
> >> >+	spin_lock_init(&sw->ports_lock);
> >> >+	INIT_LIST_HEAD(&sw->port_list);
> >> >+
> >> >+	err = prestera_hw_switch_mac_set(sw, sw->base_mac);
> >> >+	if (err)
> >> >+		return err;
> >> >+
> >> >+	err = prestera_rxtx_switch_init(sw);
> >> >+	if (err)
> >> >+		return err;
> >> >+
> >> >+	err = prestera_event_handlers_register(sw);
> >> >+	if (err)
> >> >+		goto err_evt_handlers;
> >> >+
> >> >+	err = prestera_create_ports(sw);
> >> >+	if (err)
> >> >+		goto err_ports_create;
> >> >+
> >> >+	return 0;
> >> >+
> >> >+err_ports_create:
> >> 
> >> You are missing prestera_event_handlers_unregister(sw); call here.
> >> 
> >it is handled below in prestera_switch_fini().
> 
> Sure, but you should call it here in the error path as well. That is my
> point.
> 
I understand your point - to make error path more clear, and symmetric ?

> >
> >> 
> >> >+err_evt_handlers:
> >> >+	prestera_rxtx_switch_fini(sw);
> >> >+
> >> >+	return err;
> >> >+}
> >> >+
> >> >+static void prestera_switch_fini(struct prestera_switch *sw)
> >> >+{
> >> >+	prestera_destroy_ports(sw);
> >> >+	prestera_event_handlers_unregister(sw);
> >> >+	prestera_rxtx_switch_fini(sw);
> >> >+}
> >> >+
> >> >+int prestera_device_register(struct prestera_device *dev)
> >> >+{
> >> >+	struct prestera_switch *sw;
> >> >+	int err;
> >> >+
> >> >+	sw = kzalloc(sizeof(*sw), GFP_KERNEL);
> >> >+	if (!sw)
> >> >+		return -ENOMEM;
> >> >+
> >> >+	dev->priv = sw;
> >> >+	sw->dev = dev;
> >> >+
> >> >+	err = prestera_switch_init(sw);
> >> >+	if (err) {
> >> >+		kfree(sw);
> >> >+		return err;
> >> >+	}
> >> >+
> >> >+	registered_switch = sw;
> >> >+	return 0;
> >> >+}
> >> >+EXPORT_SYMBOL(prestera_device_register);
> >> >+
> >> >+void prestera_device_unregister(struct prestera_device *dev)
> >> >+{
> >> >+	struct prestera_switch *sw = dev->priv;
> >> >+
> >> >+	registered_switch = NULL;
> >> >+	prestera_switch_fini(sw);
> >> >+	kfree(sw);
> >> >+}
> >> >+EXPORT_SYMBOL(prestera_device_unregister);
> >> >+
> >> >+static int __init prestera_module_init(void)
> >> >+{
> >> >+	if (!base_mac) {
> >> >+		pr_err("[base_mac] parameter must be specified\n");
> >> >+		return -EINVAL;
> >> >+	}
> >> >+	if (!mac_pton(base_mac, base_mac_addr)) {
> >> >+		pr_err("[base_mac] parameter has invalid format\n");
> >> >+		return -EINVAL;
> >> >+	}
> >> >+
> >> >+	prestera_wq = alloc_workqueue("prestera", 0, 0);
> >> >+	if (!prestera_wq)
> >> >+		return -ENOMEM;
> >> >+
> >> >+	return 0;
> >> >+}
> >> >+
> >> >+static void __exit prestera_module_exit(void)
> >> >+{
> >> >+	destroy_workqueue(prestera_wq);
> >> >+}
> >> >+
> >> >+module_init(prestera_module_init);
> >> >+module_exit(prestera_module_exit);
> >> >+
> >> >+MODULE_AUTHOR("Marvell Semi.");
> >> >+MODULE_LICENSE("Dual BSD/GPL");
> >> >+MODULE_DESCRIPTION("Marvell Prestera switch driver");
> >> >+
> >> >+module_param(base_mac, charp, 0);
> >> 
> >> No please.
> >> 
> >> 
> >> [..]
> >>