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SubjectRe: [PATCH] tcm_fc: rcu_deref outside rcu lock/unlock section
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On Aug 18, 2012, at 3:35 PM, Nicholas A. Bellinger wrote:

> On Sat, 2012-08-18 at 16:10 +0400, Denis Efremov wrote:
>> Use rcu_dereference_protected in order to prevent lockdep
>> complaint. Sequel of the patch 863555be
>>
>> Found by Linux Driver Verification project (linuxtesting.org).
>>
>> Signed-off-by: Denis Efremov <yefremov.denis@gmail.com>
>> ---
>> drivers/target/tcm_fc/tfc_sess.c | 4 +++-
>> 1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/target/tcm_fc/tfc_sess.c b/drivers/target/tcm_fc/tfc_sess.c
>> index 87901fa..3c9e5b5 100644
>> --- a/drivers/target/tcm_fc/tfc_sess.c
>> +++ b/drivers/target/tcm_fc/tfc_sess.c
>> @@ -456,7 +456,9 @@ static void ft_prlo(struct fc_rport_priv *rdata)
>> struct ft_tport *tport;
>>
>> mutex_lock(&ft_lport_lock);
>> - tport = rcu_dereference(rdata->local_port->prov[FC_TYPE_FCP]);
>> + tport = rcu_dereference_protected(rdata->local_port->prov[FC_TYPE_FCP],
>> + lockdep_is_held(&ft_lport_lock));
>> +
>> if (!tport) {
>> mutex_unlock(&ft_lport_lock);
>> return;
>
> This looks OK to silence lockdep. CC'ing MDR + Kiran for good measure
> here, and will move from target-pending queue -> master with their ACK.
>
> Thanks Dennis!
>
> --nab


Ack. In fact I wonder why I didn't encounter it myself.

--
Mark Rustad, LAN Access Division, Intel Corporation



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