Re: [B.A.T.M.A.N.] [PATCH v5 03/31] batman-adv: Avoid recursive call_rcu for batadv_bla_claim

[Marek Lindner <mareklindner@neomailbox.ch>]

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On Thursday, January 14, 2016 15:28:19 Sven Eckelmann wrote:
> The batadv_claim_free_ref function uses call_rcu to delay the free of the
> batadv_bla_claim object until no (already started) rcu_read_lock is enabled
> anymore. This makes sure that no context is still trying to access the
> object which should be removed. But batadv_bla_claim also contains a
> reference to backbone_gw which must be removed.
> 
> The reference drop of backbone_gw was done in the call_rcu function
> batadv_claim_free_rcu but should actually be done in the
> batadv_claim_release function to avoid nested call_rcus. This is important
> because rcu_barrier (e.g. batadv_softif_free or batadv_exit) will not
> detect the inner call_rcu as relevant for its execution. Otherwise this
> barrier will most likely be inserted in the queue before the callback of
> the first call_rcu was executed. The caller of rcu_barrier will therefore
> continue to run before the inner call_rcu callback finished.
> 
> Fixes: a9ce0dc43e2c ("batman-adv: add basic bridge loop avoidance code")
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
> v5:
>  - fix commit message ("batadv_hardif_neigh_free_ref()" ->
>    "batadv_claim_free_ref()"

Applied in revision 2783bc2.

Thanks,
Marek

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