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Re: mac80211: sta info locking

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> >  > The problem is that RX a TX BA establishments usually happens
> >  > concurrently for single STA, those are independent state machines.  We
> >  > have to review this carefully before spinlokcs are removed.
> >
> >  I wouldn't want to remove them, but it seems overkill two have two
> >  spinlocks. What I'd like to do is remove the ampdu tx, ampdu rx and mesh
> >  spinlocks and instead use just a single one for all three uses, and then
> >  use that one to protect the flags as well.
> >
> >  It seems to me that even if the RX/TX BA establishment is happening
> >  concurrently then it's still serialized by the frames on the air so
> >  ultimately can't actually happen on different CPUs so the lock won't be
> >  contended.
> 
> I'm not sure about this, this is quite gentle and requires heavy
> testing.  I'll try to review this with Ron tomorrow and all other
> changes you've suggested.

Thanks. Yes, I do realize that this is a bit intrusive. On the other
hand, I can't see the code holding the spinlock for longer code/periods
of time (nor should it). Or do you think the driver is allowed to call
into the AMPDU TX setup path while being called from the AMPDU RX setup
path? That would be a bit weird.

> Do you have any setup to check your these changes?

Unfortunately not quite yet. I have an 11n AP now though, but broke of
one of the antennas, I'll need to see how well it works.

> Currently there is known possible deadlock when unloading driver while
> heavy HT traffic. This is happening while treering down BA session. I
> need to solve this as well.

Interesting, where does it deadlock?

johannes

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