Whenever an ath(4) 11n station reassociates or downgrades from aggregation to no aggregation, there's a chance that it'll hang and refuse to queue more frames. The session needs to be fully torn down (eg ifconfig wlanX down) for things to go back to normal. Fix: I actually have debugged this a little already. So the problem seems to be that there's more than one entry point into ath_tx_tid_cleanup(). It's likely a couple of calls into the reassociation path or one into reassociate and one into aggregation teardown. I'll go figure that bit out soon. But what it leads to is thus: * the caller causes ath_tx_tid_pause(); * ath_tx_tid_cleanup() is called; * the first time this happens it sees there's 1 or more frames to cleanup, so it sets tid->cleanup_inprogress; * the caller then checks if that's set to 1 - if so, it assumes that it should wait until the cleanup is finished; * otherwise it calls ath_tx_tid_resume(). If tid->cleanup_inprogress is set to 1 then the normal TX completion path will eventually call ath_tx_comp_cleanup_unaggr() or ath_tx_comp_cleanup_aggr() which will clear the flag and resume the TID. If a second path through ath_tx_tid_cleanup() occurs, then: * the caller pauses; * ath_tx_tid_cleanup() is called; * tid->cleanup_inprogress is set to 1, but there's no code to check whether this call actually set it or not - so it doesn't call ath_tx_tid_resume(). So once the frames complete and ath_tx_tid_resume() is called, there's still a pending paused reference and thus traffic never continues flowing.
Responsible Changed From-To: freebsd-bugs->freebsd-wireless Over to maintainer(s).
I believe this is fixed in FreeBSD-HEAD. I found and squished these until I had it constantly doing AMPDU upgrade/downgrade due to high packet loss whilst doing constant traffic. I'll re-open this if it pops up again.