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

[Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>]

On Thu, Sep 29, 2005 at 04:30:28PM -0700, Suzanne Wood wrote:
> 
> > BTW, could you please move the rcu_dereference in in_dev_get()
> > into the if clause? The barrier is not needed when ip_ptr is
> > NULL.
> 
> The trouble with that may be that there are three events, the
> dereference, the assignment, and the conditional test.  The
> rcu_dereference() is meant to assure deferred destruction
> throughout.

The deferred destruction is guaranteed here by the reference count.
The only purpose served by rcu_dereference() in in_dev_get() is to
prevent the user from seeing pre-initialisation data.

When the pointer is NULL, you can't see any data at all, let alone
pre-initialisation data.

Cheers,
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