Johannes Berg [off-list ref] writes:

On Sat, 2018-09-08 at 00:22 +0200, Toke H=C3=B8iland-J=C3=B8rgensen wrote:

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=20
A few things that were discussed in the last round that I did *not* chan=

ge:

Thanks for this list btw.

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- I did not add any locking around next_txq(); the driver is still suppo=

sed

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  to maintain a lock that prevents two threads from trying to schedule t=

he

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  same AC at the same time. This is what drivers already do, so I figure=

d it

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  was easier to just keep it that way rather than do it in mac80211.

I'll look at this in the code, but from a maintainer perspective I'm
somewhat worried that this will lead to issues that are really the
driver's fault, but surface in mac80211. I don't know how easy it
would be to catch that.

Yeah, I get what you mean. The alternative would be to have a
ieee80211_start_schedule(ac) and ieee80211_end_schedule(ac), which
basically just takes a lock. Would mean we could get rid of the 'first'
parameter for next_txq(), so might not be such a bad idea; and if the
driver has its own locking the extra locking in mac80211 would just be
an always-uncontested spinlock, which shouldn't be much overhead, right?

-Toke