Messages in this thread | | | Date | Fri, 30 Sep 2005 10:21:44 +1000 | Subject | Re: [RFC][PATCH] identify in_dev_get rcu read-side critical sections | From | Herbert Xu <> |
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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, -- 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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