Re: [PATCH 1/2] rcu: add rcu_access_pointer andrcu_dereference_protect

From: Eric Dumazet
Date: Wed Apr 07 2010 - 12:29:32 EST

Le mercredi 07 avril 2010 Ã 17:19 +0100, David Howells a Ãcrit :

> Why not:
> ASSERT(atomic_read(&sk->sk_wmem_alloc) == 0);
> filter = rcu_dereference(sk->sk_filter);
> This is much clearer, and you're not combining an unrelated assertion with the
> RCU dereference.

1) Because we want the check being done only when CONFIG_PROVE_RCU is

2) Because rcu_dereference() default condition is : 'Am I owning
rcu_read_lock() or equivalent'.
In this context, I am _not_ owning rcu lock, so we will trigger a

So this is best done as is :)

I personally find this very clear and clean, this is why I acked Paul
patch :)

If we were 100% sure testing sk_wmem_alloc is not necessary, we would
have put :

filter = rcu_dereference_check(sk->sk_filter, 1);

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