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Date: Sun, 22 Feb 2015 20:33:33 -0800
From: Florian Fainelli <f.fainelli@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Guenter Roeck <linux@...ck-us.net>,
netdev <netdev@...r.kernel.org>,
David Miller <davem@...emloft.net>,
Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
jerome.oufella@...oirfairelinux.com,
Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH RFC 1/2] net: dsa: integrate with SWITCHDEV for HW bridging
2015-02-22 20:22 GMT-08:00 Andrew Lunn <andrew@...n.ch>:
> On Sun, Feb 22, 2015 at 08:07:03PM -0800, Guenter Roeck wrote:
>> On 02/22/2015 07:14 PM, Andrew Lunn wrote:
>> >On Sun, Feb 22, 2015 at 06:20:44PM -0800, Guenter Roeck wrote:
>> >>On 02/17/2015 11:26 AM, Florian Fainelli wrote:
>> >>>In order to support bridging offloads in DSA switch drivers, select
>> >>>NET_SWITCHDEV to get access to the port_stp_update and parent_get_id
>> >>>NDOs that we are required to implement.
>> >>>
>> >>>To facilitate the integratation at the DSA driver level, we implement 3
>> >>>types of operations:
>> >>>
>> >>
>> >>Hi Florian,
>> >>
>> >>>
>> >>>+/* Return a bitmask of all ports being currently bridged. Note that on
>> >>>+ * leave, the mask will still return the bitmask of ports currently bridged,
>> >>>+ * prior to port removal, and this is exactly what we want.
>> >>>+ */
>> >>>+static u32 dsa_slave_br_port_mask(struct dsa_switch *ds)
>> >>>+{
>> >>>+ unsigned int port;
>> >>>+ u32 mask = 0;
>> >>>+
>> >>>+ for (port = 0; port < DSA_MAX_PORTS; port++) {
>> >>>+ if (!((1 << port) & ds->phys_port_mask))
>> >>>+ continue;
>> >>>+
>> >>>+ if (ds->ports[port]->priv_flags & IFF_BRIDGE_PORT)
>> >>>+ mask |= 1 << port;
>> >>
>> >>Problem is that the function can be called through dsa_slave_netdevice_event
>> >>before the slave devices are fully initialized.
>> >>
>> >>After adding
>> >>
>> >>+ if (!ds->ports[port]) {
>> >>+ netdev_err(bridge,
>> >>+ "No ports data for port %d, mask=0x%x\n",
>> >>+ port, ds->phys_port_mask);
>> >>+ continue;
>> >>+ }
>> >>
>> >>and with some more debug messages added to dsa_switch_setup(), I see the following.
>> >>
>> >>[ 14.187290] e1000e 0000:00:19.0 em1: [0]: Creating slave device for port 1(port1)
>> >>[ 14.272605] e1000e 0000:00:19.0 em1: [0]: Creating slave device for port 2(port2)
>> >>[ 14.353118] e1000e 0000:00:19.0 em1: [0]: Creating slave device for port 3(port3)
>> >>[ 14.472002] br0: No ports data for port 3, mask=0x1e
>> >>[ 14.472053] br0: No ports data for port 4, mask=0x1e
>> >>[ 14.472753] e1000e 0000:00:19.0 em1: [0]: Creating slave device for port 4(host2esb)
>> >>
>> >>This happens if I add the bridge configuration to /etc/network/interfaces instead
>> >>of creating the bridge manually. Apparently dsa_switch_setup() is not yet complete
>> >>when dsa_slave_netdevice_event is executed to handle a state change on one of its
>> >>newly created slave interfaces.
>> >>
>> >>The relevant information from /etc/network/interfaces is:
>> >>
>> >>auto br0
>> >>
>> >>iface port1 inet manual
>> >>iface port2 inet manual
>> >>
>> >>iface br0 inet dhcp
>> >> bridge_ports port1 port2
>> >
>> >Hi Guenter
>> >
>> >Does this actually matter? The ports which don't exists yet are not
>> >being added to the bridge. The mask will come out correct. What
>> >happens when port4 is made a member of the bridge? I expect it
>> >works. It is the creation of the interface which triggers hotplug to
>> >read interfaces and add the interface to the port.
>> >
>>
>> if (!ds->ports[port])
>> continue;
>>
>> might be an option. However, I am not sure that what you say is correct,
>> at least not strictly speaking. dsa_slave_create() returns the created
>> slave device, which is added to ds->ports[port] in dsa_switch_setup().
>> Since there is no protection in dsa_switch_setup(), there is no guarantee
>> that the callback doesn't happen prior to the initialization of
>> ds->ports[port]. So the above would leave a race condition, where the
>> port being added to the bridge _is_ one for which ds->ports[port] is
>> not yet initialized.
>
> Yes, you are correct, there is a race here.
>
>
>> Protecting the entire slave creation loop in dsa_switch_setup()
>> and using register_netdevice() in dsa_slave_create() solves the problem
>> as far as I can see, I just don't know if it is an acceptable solution.
>
> Or:
>
> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
> index 2173402d87e0..1aa120d6d0e4 100644
> --- a/net/dsa/dsa.c
> +++ b/net/dsa/dsa.c
> @@ -325,8 +325,6 @@ dsa_switch_setup(struct dsa_switch_tree *dst, int index,
> index, i, pd->port_names[i]);
> continue;
> }
> -
> - ds->ports[i] = slave_dev;
> }
>
> #ifdef CONFIG_NET_DSA_HWMON
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index f23deadf42a0..d6004072a957 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -669,12 +669,14 @@ dsa_slave_create(struct dsa_switch *ds, struct device *parent,
> free_netdev(slave_dev);
> return NULL;
> }
> + ds->ports[port] = slave_dev;
>
> ret = register_netdev(slave_dev);
> if (ret) {
> netdev_err(master, "error %d registering interface %s\n",
> ret, slave_dev->name);
> phy_disconnect(p->phy);
> + ds->ports[port] = NULL;
> free_netdev(slave_dev);
> return NULL;
> }
>
> Not tested. But the point being, ensure everything is setup before
> calling register_netdev().
I prefer that too over using locking around the dsa slave network
device creation, provided that this works for Guenter as well.
--
Florian
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