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

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Message-ID: <CADvbK_dt7WEjw=o1zhObgdT5Q9HLtRAppr5iEQAOu6ggfwvv2Q@mail.gmail.com>
Date:	Thu, 18 Feb 2016 21:59:33 +0800
From:	Xin Long <lucien.xin@...il.com>
To:	Neil Horman <nhorman@...driver.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 <davem@...emloft.net>
Subject: Re: [PATCH net 1/3] sctp: move rcu_read_lock from __sctp_lookup_association
 to sctp_lookup_association

On Thu, Feb 18, 2016 at 12:11 AM, Neil Horman <nhorman@...driver.com> wrote:
> 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?
>
the resource is also accessed in threads, not only in BH, so we cannot
use rcu_read_lock_bh here.

> Neil
>