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From: Vladimir Oltean <olteanv@gmail.com>
To: Nikolay Aleksandrov <nikolay@nvidia.com>
Cc: Jakub Kicinski <kuba@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Tobias Waldekranz <tobias@waldekranz.com>,
	Claudiu Manoil <claudiu.manoil@nxp.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Roopa Prabhu <roopa@nvidia.com>, Jiri Pirko <jiri@resnulli.us>,
	Ido Schimmel <idosch@idosch.org>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	UNGLinuxDriver@microchip.com, Ivan Vecera <ivecera@redhat.com>,
	linux-omap@vger.kernel.org,
	Vladimir Oltean <vladimir.oltean@nxp.com>
Subject: Re: [PATCH v3 net-next 08/12] net: dsa: replay port and host-joined mdb entries when joining the bridge
Date: Mon, 22 Mar 2021 18:56:14 +0200
Message-ID: <20210322165614.56sgtdxpmnp2dkja@skbuf> (raw)
In-Reply-To: <7a89fd44-98d7-072f-6215-84960e27b0d9@nvidia.com>

On Mon, Mar 22, 2021 at 06:35:10PM +0200, Nikolay Aleksandrov wrote:
> > +	hlist_for_each_entry(mp, &br->mdb_list, mdb_node) {
> 
> You cannot walk over these lists without the multicast lock or RCU. RTNL is not
> enough because of various timers and leave messages that can alter both the mdb_list
> and the port group lists. I'd prefer RCU to avoid blocking the bridge mcast.

The trouble is that I need to emulate the calling context that is
provided to SWITCHDEV_OBJ_ID_HOST_MDB and SWITCHDEV_OBJ_ID_PORT_MDB, and
that means blocking context.

So if I hold rcu_read_lock(), I need to queue up the mdb entries, and
notify the driver only after I leave the RCU critical section. The
memory footprint may temporarily blow up.

In fact this is what I did in v1:
https://patchwork.kernel.org/project/netdevbpf/patch/20210224114350.2791260-15-olteanv@gmail.com/

I just figured I could get away with rtnl_mutex protection, but it looks
like I can't. So I guess you prefer my v1?

  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-20 22:34 [PATCH v3 net-next 00/12] Better support for sandwiched LAGs with bridge and DSA Vladimir Oltean
2021-03-20 22:34 ` [PATCH v3 net-next 01/12] net: dsa: call dsa_port_bridge_join when joining a LAG that is already in a bridge Vladimir Oltean
2021-03-20 22:34 ` [PATCH v3 net-next 02/12] net: dsa: pass extack to dsa_port_{bridge,lag}_join Vladimir Oltean
2021-03-20 22:34 ` [PATCH v3 net-next 03/12] net: dsa: inherit the actual bridge port flags at join time Vladimir Oltean
2021-03-20 22:34 ` [PATCH v3 net-next 04/12] net: dsa: sync up with bridge port's STP state when joining Vladimir Oltean
2021-03-20 22:34 ` [PATCH v3 net-next 05/12] net: dsa: sync up VLAN filtering state when joining the bridge Vladimir Oltean
2021-03-20 22:34 ` [PATCH v3 net-next 06/12] net: dsa: sync multicast router " Vladimir Oltean
2021-03-20 22:34 ` [PATCH v3 net-next 07/12] net: dsa: sync ageing time " Vladimir Oltean
2021-03-22 16:02   ` Florian Fainelli
2021-03-20 22:34 ` [PATCH v3 net-next 08/12] net: dsa: replay port and host-joined mdb entries " Vladimir Oltean
2021-03-22 16:35   ` Nikolay Aleksandrov
2021-03-22 16:56     ` Vladimir Oltean [this message]
2021-03-22 17:00       ` Nikolay Aleksandrov
2021-03-20 22:34 ` [PATCH v3 net-next 09/12] net: dsa: replay port and local fdb " Vladimir Oltean
2021-03-22 16:39   ` Nikolay Aleksandrov
2021-03-20 22:34 ` [PATCH v3 net-next 10/12] net: dsa: replay VLANs installed on port " Vladimir Oltean
2021-03-22 16:48   ` Nikolay Aleksandrov
2021-03-20 22:34 ` [PATCH v3 net-next 11/12] net: ocelot: call ocelot_netdevice_bridge_join when joining a bridged LAG Vladimir Oltean
2021-03-20 22:34 ` [PATCH v3 net-next 12/12] net: ocelot: replay switchdev events when joining bridge Vladimir Oltean
2021-03-22 16:27 ` [PATCH v3 net-next 00/12] Better support for sandwiched LAGs with bridge and DSA Nikolay Aleksandrov

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