From: Steffen Klassert <steffen.klassert@secunet.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>, netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH] inetpeer: fix a race in inetpeer_gc_worker()
Date: Tue, 5 Jun 2012 15:01:42 +0200 [thread overview]
Message-ID: <20120605130142.GF27795@secunet.com> (raw)
In-Reply-To: <1338900966.2760.2596.camel@edumazet-glaptop>
On Tue, Jun 05, 2012 at 02:56:06PM +0200, Eric Dumazet wrote:
> On Tue, 2012-06-05 at 14:42 +0200, Steffen Klassert wrote:
> >
> > Hm, I agree that we need rcu protection when we remove single entries
> > from an inetpeer tree. But in this case we invalidate the entire tree.
> >
> > The first lookup after inetpeer_invalidate_tree() was invoked should
> > find an empty tree, base->root initialized to peer_avl_empty_rcu.
> >
> > Maybe I'm wrong, but I don't see how a lookup should find such an
> > old invalidated tree.
> >
>
> You are absolutely wrong yes.
>
> A concurrent lookup can read previous values of the root pointer, even
> if you wrote a new value in it. Thats whole RCU point.
Argh, yes. You are absolutely right of course, now I got it :)
Thanks for your explaination.
prev parent reply other threads:[~2012-06-05 13:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-05 9:28 [PATCH] inetpeer: fix a race in inetpeer_gc_worker() Eric Dumazet
2012-06-05 11:56 ` Steffen Klassert
2012-06-05 12:19 ` Eric Dumazet
2012-06-05 12:42 ` Steffen Klassert
2012-06-05 12:56 ` Eric Dumazet
2012-06-05 13:01 ` Steffen Klassert [this message]
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