Re: [Patch net-next] bridge: fix seq check in br_mdb_dump()

From: Cong Wang <redacted>
Date: Tue, 11 Dec 2012 11:49:32 +0800

On Mon, 2012-12-10 at 13:46 -0500, David Miller wrote:

quoted

From: Cong Wang <redacted>
Date: Mon, 10 Dec 2012 20:15:35 +0800

quoted

From: Cong Wang <redacted>

In case of rehashing, introduce a global variable 'br_mdb_rehash_seq'
which gets increased every time when rehashing, and assign
net->dev_base_seq + br_mdb_rehash_seq to cb->seq.

In theory cb->seq could be wrapped to zero, but this is not
easy to fix, as net->dev_base_seq is not visible inside
br_mdb_rehash(). In practice, this is rare.

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Stephen Hemminger <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Jesper Dangaard Brouer <redacted>
Signed-off-by: Cong Wang <redacted>

No synchronization at all is applied to this variable, I can't
see how this is OK.

br_mdb_rehash() is protected by the multicast spinlock, so increasing
this variable is protected by it, and reading the variable doesn't need
locking. Am I missing anything? Or should we use atomic_t?

I missed that locking, ok, looks good.

Applied, thanks.