Re: [ath9k-devel] ath9k, multiple stations, and AMPDUs

[Felix Fietkau <nbd@openwrt.org>]

On 2010-09-21 8:04 PM, Ben Greear wrote:
> On 09/21/2010 11:00 AM, Felix Fietkau wrote:
>> On 2010-09-21 7:25 PM, Ben Greear wrote:
>>> On 09/21/2010 05:19 AM, Felix Fietkau wrote:
>>>> On 2010-09-21 2:08 PM, Ben Greear wrote:
>>>
>>>>> If you have any more details on this, please let me know.  I'm going to
>>>>> attempt to fix it...I certainly have a good test case :)
>>>> ath_tx_complete_aggr completes an A-MPDU frame, which typically triggers
>>>> the release of the next A-MPDU to the hw queue.
>>>> To keep track of the Block ACK window, it needs to look up the TID, for
>>>> which it needs a STA pointer. At that level, the driver typically
>>>> doesn't have access to the vif.
>>>>
>>>> It might be possible to fix this by adding another sta lookup helper
>>>> function in mac80211 that takes another address argument for the BSSID,
>>>> so that it can get the sta entry for the correct vif. I don't know if
>>>> Johannes wants something like that though.
>>>
>>> Could we just poke a pointer to the STA into the ath_buf structure?
>> No, that doesn't work because of RCU.
> 
> Would it also be bad to use skb->dev to find an STA?
It would be bad to keep a STA pointer around anywhere in the skb or the
ath_buf. You can only use it within a rcu_read_lock()/rcu_read_unlock()
pair.

- Felix