Re: mac80211 keeps trying to start ampdu session??

[Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>]

On Tue, 23 Oct 2018 10:18:54 +0200
Johannes Berg <johannes@sipsolutions.net> wrote:
> On Tue, 2018-10-23 at 10:44 +0300, Ali MJ Al-Nasrawy wrote:
> > Hi,
> > 
> > I am trying to debug brcmsmac wireless driver for spamming the log
> > with the message:
> > [...] START: tid 2 is not agg'able
> > for it does not support AMPDU aggreggation for TID 2.
> > 
> > And after quick tracing, I found that mac80211 keeps trying to start
> > AMPDU session for the _same TID and STA_ despite that the driver
> > returns non-zero code via its ampdu_action callback and that
> > non-zero return codes are recognized as the "HW unavailable" for
> > such session (agg-tx.c:ieee80211_tx_ba_session_handle_start)
> > 
> > So, Is that an expected behaviour from mac80211 or not??  
> 
> This depends on the rate control algorithm, it triggers this.

In this case, it is minstrel_ht.

> 
> I think - perhaps depending on the return value - mac80211 *does* give
> up eventually, but not really sure.

The return value is handled only in
agg-tx.c:ieee80211_tx_ba_session_handle_start and it doesn't pass it
down or recognize difference between non-zero return values.

And I don't think that it gives up retrying: I already have 800MB of
compressed logs for the last four days only full of this message and
additionally I ran a simple test for the last hour and found that it
tries to start ampdu session for every frame to be sent with that TID!

> Perhaps just remove the message?

OK, I report this just in case of it being unintended behavior with
probably a negative performance impact.