On Mon, 2018-09-10 at 13:17 +0200, Toke Høiland-Jørgensen wrote: > > > - I did not add any locking around next_txq(); the driver is still supposed > > > to maintain a lock that prevents two threads from trying to schedule the > > > same AC at the same time. This is what drivers already do, so I figured it > > > 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. And I guess start would increment the schedule number, which is now dependent on first > Would mean we could get rid of the 'first' > parameter for next_txq(), so might not be such a bad idea; Right, that's what I meant. > 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? It may still bounce around CPUs if you call this from other places, but I suspect that wouldn't be the biggest issue. There are a lot of calculations going on too... johannes
