netdev - Re: [net-next PATCH 3/3] net: frag queue per hash bucket locking

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Date:	Fri, 29 Mar 2013 01:33:08 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Jesper Dangaard Brouer <brouer@...hat.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Florian Westphal <fw@...len.de>,
	Daniel Borkmann <dborkman@...hat.com>
Subject: Re: [net-next PATCH 3/3] net: frag queue per hash bucket locking

On Thu, Mar 28, 2013 at 04:39:42PM -0700, Eric Dumazet wrote:
> On Fri, 2013-03-29 at 00:30 +0100, Hannes Frederic Sowa wrote:
> > On Thu, Mar 28, 2013 at 01:22:44PM -0700, Eric Dumazet wrote:
> > > On Thu, 2013-03-28 at 19:57 +0100, Hannes Frederic Sowa wrote:
> > > 
> > > > I assume that it has to do with the usage of this code in
> > > > ipv6/netfilter/nf_conntrack_reasm.c, which could be invoked from process
> > > > context, if I read it correctly.
> > > 
> > > Then there would be a possible deadlock in current code.
> > 
> > Netfilter currently does a local_bh_disable() before entering inet_fragment
> > (and later enables it, again).
> > 
> 
> Good, so no need for the _bh() as I suspected.

Ack.

I replaced the _bh spin_locks with plain spinlocks and tested the code
with sending fragments and receiving fragments (netfilter and reassmbly
logic) with lockdep and didn't get any splats. Looks good so far.

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