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,
--
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