netdev - Re: RCU'ed dst_get

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Date:	Wed, 30 Nov 2011 00:11:01 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Marc Aurele La France <tsi@...berta.ca>
Cc:	Roland Dreier <roland@...nel.org>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-rdma@...r.kernel.org
Subject: Re: RCU'ed dst_get_neighbour()

Le mardi 29 novembre 2011 à 16:03 -0700, Marc Aurele La France a écrit :

> No, only warnings (splats as you call them) would be produced.  The fact 
> is you added side-effects to dst_get_neighbour(), and I would expect all 
> its invocations to be affected.
> 

A splat _is_ a bad thing.

We certainly have some bugs, but I sent an infiniband patch, not a
'change the world' one ;)

Most of the network stack is run under rcu_read_lock() already.

If you notice other lockdep splats, please shout :)

Some changes are needed now rcu_read_lock_bh() doesnt imply
rcu_read_lock().

For example, recently added skb_update_prio() is buggy, since it uses
rcu_dereference() while its caller, dev_queue_xmit() called
rcu_read_lock_bh()



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