Re: [Regression] rt2800usb - Wifi performance issues and connection drops

[Alexander Wetzel]

On 08.03.23 08:52, Felix Fietkau wrote:

> > I'm also planning to provide some more debug patches, to figuring out
> > which part of commit 4444bc2116ae ("wifi: mac80211: Proper mark iTXQs
> > for resumption") fixes the issue for you. Assuming my understanding
> > above is correct the patch should not really fix/break anything for
> > you...With the findings above I would have expected your git bisec to
> > identify commit a790cc3a4fad ("wifi: mac80211: add wake_tx_queue
> > callback to drivers") as the first broken commit...
> I can't point to any specific series of events where it would go wrong, 
> but I suspect that the problem might be the fact that you're doing tx 
> scheduling from within ieee80211_handle_wake_tx_queue. I don't see how 
> it's properly protected from potentially being called on different CPUs 
> concurrently.
>
> Back when I was debugging some iTXQ issues in mt76, I also had problems 
> when tx scheduling could happen from multiple places. My solution was to 
> have a single worker thread that handles tx, which is scheduled from the 
> wake_tx_queue op.
> Maybe you could do something similar in mac80211 for non-iTXQ drivers.

I think it's already doing all of that:
ieee80211_handle_wake_tx_queue() is the mac80211 implementation for the 
wake_tx_queue op. The drivers without native iTXQ support simply link it 
to this handler.

Alexander