Re: Suspicious RCU usage in mac80211

[Larry Finger <Larry.Finger@lwfinger.net>]

On 05/04/2012 01:48 AM, Mohammed Shafi wrote:
> On Fri, May 4, 2012 at 12:10 PM, Mohammed Shafi
> <shafi.wireless@gmail.com>  wrote:
>> Hi Larry,
>>
>> On Fri, May 4, 2012 at 11:47 AM, Larry Finger<Larry.Finger@lwfinger.net>  wrote:
>>> On 05/03/2012 01:38 PM, Johannes Berg wrote:
>>>>
>>>> diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
>>>> index 5b7053c..40d3ff4 100644
>>>> --- a/net/mac80211/agg-tx.c
>>>> +++ b/net/mac80211/agg-tx.c
>>>> @@ -421,16 +421,22 @@ static void
>>>> sta_tx_agg_session_timer_expired(unsigned long data)
>>>>         struct tid_ampdu_tx *tid_tx;
>>>>         unsigned long timeout;
>>>>
>>>> -       tid_tx = rcu_dereference_protected_tid_tx(sta, *ptid);
>>>> -       if (!tid_tx)
>>>> +       rcu_read_lock();
>>>> +       tid_tx = rcu_dereference(sta->ampdu_mlme.tid_tx[*ptid]);
>
> Larry, Johannes seems to use rcu_dereference straight way just like in
> 'sta_addba_resp_timer_expired'
> and have it protected by rcu_read_locks

Sorry. I missed that subtle difference. Submitted "from Johannes".

Larry