netdev - Re: [PATCH net 1/3] sctp: move rcu_read_lock from __sctp_lookup_association to sctp_lookup

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Date:	Wed, 17 Feb 2016 11:11:04 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Xin Long <lucien.xin@...il.com>
Cc:	network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
	Vlad Yasevich <vyasevich@...il.com>, davem@...emloft.net
Subject: Re: [PATCH net 1/3] sctp: move rcu_read_lock from
 __sctp_lookup_association to sctp_lookup_association

On Mon, Feb 15, 2016 at 02:28:03PM +0800, Xin Long wrote:
> __sctp_lookup_association() is only invoked by sctp_v4_err() and
> sctp_rcv(), both which run on the rx BH, and it has been protected
> by rcu_read_lock [see ip_local_deliver_finish() / ipv6_rcv()].
> 
> So we can move it to sctp_lookup_association, only let
> sctp_lookup_association use rcu_read_lock.
> 
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Not that it was right before if this is true, but if we're using rcu in a bottom
half path, shouldn't rcu_read_lock_bh be used instead here?

Neil

> ---
>  net/sctp/input.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sctp/input.c b/net/sctp/input.c
> index 49d2cc7..21a2d6b 100644
> --- a/net/sctp/input.c
> +++ b/net/sctp/input.c
> @@ -937,7 +937,6 @@ static struct sctp_association *__sctp_lookup_association(
>  	struct sctp_transport *t;
>  	struct sctp_association *asoc = NULL;
>  
> -	rcu_read_lock();
>  	t = sctp_addrs_lookup_transport(net, local, peer);
>  	if (!t || !sctp_transport_hold(t))
>  		goto out;
> @@ -949,7 +948,6 @@ static struct sctp_association *__sctp_lookup_association(
>  	sctp_transport_put(t);
>  
>  out:
> -	rcu_read_unlock();
>  	return asoc;
>  }
>  
> @@ -962,7 +960,9 @@ struct sctp_association *sctp_lookup_association(struct net *net,
>  {
>  	struct sctp_association *asoc;
>  
> +	rcu_read_lock();
>  	asoc = __sctp_lookup_association(net, laddr, paddr, transportp);
> +	rcu_read_unlock();
>  
>  	return asoc;
>  }
> -- 
> 2.1.0
> 
> --
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