netdev - Re: [PATCH net-next] xfrm: fix RCU bugs

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Date:	Wed, 22 Aug 2012 22:40:17 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, fan.du@...driver.com,
	fengguang.wu@...el.com, Priyanka.Jain@...escale.com
Subject: Re: [PATCH net-next] xfrm: fix RCU bugs

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sun, 19 Aug 2012 12:31:48 +0200

> From: Eric Dumazet <edumazet@...gle.com>
> 
> This patch reverts commit 56892261ed1a (xfrm: Use rcu_dereference_bh to
> deference pointer protected by rcu_read_lock_bh), and fixes bugs
> introduced in commit 418a99ac6ad ( Replace rwlock on xfrm_policy_afinfo
> with rcu )
> 
> 1) We properly use RCU variant in this file, not a mix of RCU/RCU_BH
> 
> 2) We must defer some writes after the synchronize_rcu() call or a reader
>  can crash dereferencing NULL pointer.
> 
> 3) Now we use the xfrm_policy_afinfo_lock spinlock only from process
> context, we no longer need to block BH in xfrm_policy_register_afinfo()
> and xfrm_policy_unregister_afinfo()
> 
> 4) Can use RCU_INIT_POINTER() instead of rcu_assign_pointer() in
> xfrm_policy_unregister_afinfo()
> 
> 5) Remove a forward inline declaration (xfrm_policy_put_afinfo()),
>   and also move xfrm_policy_get_afinfo() declaration.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks Eric.
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