Hi Szymon,
On Tue, Feb 7, 2012 at 9:21 AM, Szymon Janc <szymon.janc@xxxxxxxxx> wrote:
> Hi,
>
>> >> Hmm, maybe we can clear ack timer only once if we check nsent in the
>> >> end of l2cap_ertm_send() instead of potentially call it several times?
>> >> Not sure if it's worth it or not, though.
>> >
>> > This is what __l2cap_send_ack is doing i.e. sends RR frame only if
>> > l2cap_ertm_send() returned 0 (or error). Would be good to have this consistent.
>> >
>> > So maybe just clear ack timer when incrementing nsent for the 1st time?
>> >
>> > if (!nsent++)
>> > __clear_ack_timer(chan);
>> >
>>
>> But that means we would be clearing ack timer even for retransmit
>> frames which Im not sure can be account as an ack?
>
> Right, only pending I-frame(s) is an acknowledgement. But that means
> __l2cap_send_ack() is broken.
Yes, it is broken because it was relying on l2cap_ertm_send()
returning if it sent any i-frame with an ack. And that wasn't
documented anywhere AFAIK and it's very easy for someone else to add a
change that breaks this assumption.
> To fix that, I think l2cap_ertm_send should return number of pending I-frames
> transmitted, not a total number of I-frames sent.
Why? Have you checked if other part of the code relies on
l2cap_ertm_send() returning number of I-frames sent?
> I've quickly looked over the code and that change should be OK.
>
> What do you think?
I've already answered in my other e-mail. I'd like to see us tracking
what we already acked and then easily check if we need to send an ack
or not.
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index 09cd860..8dece4e 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -1448,17 +1448,19 @@ static int l2cap_ertm_send(struct l2cap_chan *chan)
>
> chan->next_tx_seq = __next_seq(chan, chan->next_tx_seq);
>
> - if (bt_cb(skb)->retries == 1)
> + if (bt_cb(skb)->retries == 1) {
> chan->unacked_frames++;
>
> + if (!nsent++)
> + __clear_ack_timer(chan);
> + }
> +
> chan->frames_sent++;
>
> if (skb_queue_is_last(&chan->tx_q, skb))
> chan->tx_send_head = NULL;
> else
> chan->tx_send_head = skb_queue_next(&chan->tx_q, skb);
> -
> - nsent++;
> }
>
> return nsent;
Regards,
--
Ulisses Furquim
ProFUSION embedded systems
http://profusion.mobi
Mobile: +55 19 9250 0942
Skype: ulissesffs
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