From: Herbert Xu <herbert@gondor.apana.org.au>
To: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Suzanne Wood <suzannew@cs.pdx.edu>,
Robert.Olsson@data.slu.se, davem@davemloft.net,
linux-kernel@vger.kernel.org, netdev@oss.sgi.com,
walpole@cs.pdx.edu
Subject: Re: [RFC][PATCH] identify in_dev_get rcu read-side critical sections
Date: Fri, 30 Sep 2005 11:04:04 +1000 [thread overview]
Message-ID: <20050930010404.GA21429@gondor.apana.org.au> (raw)
In-Reply-To: <20050930003642.GQ8177@us.ibm.com>
On Thu, Sep 29, 2005 at 05:36:42PM -0700, Paul E. McKenney wrote:
>
> > rcu_read_lock();
> > in_dev = dev->ip_ptr;
> > if (in_dev) {
> > in_dev = rcu_dereference(in_dev);
> > atomic_inc(&in_dev->refcnt);
> > }
> > rcu_read_unlock();
> > return in_dev;
>
> How about:
>
> rcu_read_lock();
> in_dev = dev->ip_ptr;
> if (rcu_dereference(in_dev)) {
> atomic_inc(&in_dev->refcnt);
> }
> rcu_read_unlock();
> return in_dev;
With this the barrier will taken even when in_dev is NULL.
I agree this isn't such a big deal since it only impacts Alpha and then
only when in_dev is NULL. But as we already do the branch anyway to
increment the reference count, we might as well make things a little
better for Alpha.
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:[~2005-09-30 1:04 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-29 23:30 [RFC][PATCH] identify in_dev_get rcu read-side critical sections 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 [this message]
2005-09-30 1:16 ` Paul E. McKenney
2005-09-30 1:19 ` Herbert Xu
-- strict thread matches above, loose matches on Subject: below --
2005-10-01 18:37 Suzanne Wood
2005-10-01 19:29 ` Herbert Xu
2005-10-01 18:00 Suzanne Wood
2005-10-01 6:56 Suzanne Wood
2005-10-01 7:12 ` Herbert Xu
2005-10-01 18:04 ` Paul E. McKenney
2005-09-30 1:06 Suzanne Wood
2005-10-01 1:13 ` Herbert Xu
2005-09-29 23:59 Suzanne Wood
2005-09-30 0:23 ` Herbert Xu
2005-09-29 23:39 Suzanne Wood
2005-09-29 16:02 Suzanne Wood
2005-09-29 21:28 ` Herbert Xu
2005-09-28 0:22 Suzanne Wood
2005-09-08 17:12 Suzanne Wood
2005-09-27 20:56 ` David S. Miller
2005-09-28 2:55 ` Herbert Xu
2005-09-28 14:51 ` Paul E. McKenney
2005-09-28 22:11 ` Herbert Xu
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