From: Herbert Xu <herbert@gondor.apana.org.au>
To: davem@davemloft.net (David S. Miller)
Cc: suzannew@cs.pdx.edu, linux-kernel@vger.kernel.org,
Robert.Olsson@data.slu.se, paulmck@us.ibm.com,
walpole@cs.pdx.edu, netdev@oss.sgi.com
Subject: Re: [RFC][PATCH] identify in_dev_get rcu read-side critical sections
Date: Wed, 28 Sep 2005 12:55:45 +1000 [thread overview]
Message-ID: <E1EKS6j-0006s4-00@gondolin.me.apana.org.au> (raw)
In-Reply-To: <20050927.135626.88296134.davem@davemloft.net>
David S. Miller <davem@davemloft.net> wrote:
>
> I agree with the changes to add rcu_dereference() use.
> Those were definitely lacking and needed.
Actually I'm not so sure that they are all needed. I only looked
at the very first one in the patch which is in in_dev_get(). That
one certainly isn't necessary because the old value of ip_ptr
is valid as long as the reference count does not hit zero.
The later is guaranteed by the increment in in_dev_get().
Because the pervasiveness of reference counting in the network stack,
I believe that we should scrutinise the other bits in the patch too
to make sure that they are all needed.
In general, using rcu_dereference/rcu_assign_pointer does not
guarantee correct code. We really need to look at each case
individually.
Cheers,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2005-09-28 2:56 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-08 17:12 [RFC][PATCH] identify in_dev_get rcu read-side critical sections Suzanne Wood
2005-09-27 20:56 ` David S. Miller
2005-09-28 2:55 ` Herbert Xu [this message]
2005-09-28 14:51 ` Paul E. McKenney
2005-09-28 22:11 ` Herbert Xu
2005-09-28 0:22 Suzanne Wood
2005-09-29 16:02 Suzanne Wood
2005-09-29 21:28 ` Herbert Xu
2005-09-29 23:30 Suzanne Wood
2005-09-30 0:21 ` Herbert Xu
2005-09-30 0:23 ` Paul E. McKenney
2005-09-30 0:27 ` Herbert Xu
2005-09-30 0:36 ` Paul E. McKenney
2005-09-30 1:04 ` Herbert Xu
2005-09-30 1:16 ` Paul E. McKenney
2005-09-30 1:19 ` Herbert Xu
2005-09-29 23:39 Suzanne Wood
2005-09-29 23:59 Suzanne Wood
2005-09-30 0:23 ` Herbert Xu
2005-09-30 1:06 Suzanne Wood
2005-10-01 1:13 ` Herbert Xu
2005-10-01 6:56 Suzanne Wood
2005-10-01 7:12 ` Herbert Xu
2005-10-01 18:04 ` Paul E. McKenney
2005-10-01 18:00 Suzanne Wood
2005-10-01 18:37 Suzanne Wood
2005-10-01 19:29 ` Herbert Xu
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