Kan Yan <kyan@xxxxxxxxxx> writes:
> It is most likely just insufficient locking. active_txq_lock is per
> AC, can't protect local->aql_total_pending_airtime against racing
> conditions:
> void ieee80211_sta_update_pending_airtime(...)
> {
> spin_lock_bh(&local->active_txq_lock[ac]);
> ...
> local->aql_total_pending_airtime -= tx_airtime;
> ...
> spin_unlock_bh(&local->active_txq_lock[ac]);
> }
Ohh, right; didn't even realise those were not per-AC as well...
> After changing it to atomic_t, no more aql_total_pending_airtime
> underflow so far :). Using atomic operation should also help reduce
> CPU overhead due to lock contention, as
> ieee80211_sta_update_pending_airtime() is often called from the tx
> completion routine triggered by interrupts, often in a different core
> than where __ieee80211_schedule_txq() is running.
>
> I will post a new version a bit later if the test goes well.
Awesome! :)
-Toke
