Re: [RFC][PATCH] identify in_dev_get rcu read-side critical sections

[Herbert Xu]

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@xxxxxxxxxxxxxxxxxxx>
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