Re: [Make-wifi-fast] [PATCH RFC v4 0/4] Move TXQ scheduling into mac80211

[Rajkumar Manoharan <rmanohar@codeaurora.org>]

On 2018-09-16 10:42, Toke Høiland-Jørgensen wrote:
> Another update, addressing most of the concerns raised in the last 
> round:
> 
> - Added schedule_start()/end() functions that adds locking around the
>   whole scheduling operation, which means we can get rid of the 'first'
>   parameter to ieee80211_next_txq().
> 
Toke,

Wouldn't this start()/end() APIs cause deadlock if mac80211 tries to 
acquire
active_txq_lock[ac] again? Or am I missing?

schedule_start()
while (next_txq()) {
   push_txq -> tx_dequeue()
   return_txq()
}
schedule_end()

tx_dequeue()
  ieee80211_free_txskb
   -> ieee80211_report_used_skb
    -> ieee80211_tdls_td_tx_handle
     -> ieee80211_subif_start_xmit
     -> __ieee80211_subif_start_xmit
       -> ieee80211_xmit_fast
         -> ieee80211_queue_skb
          -> schedule_and_wake_txq

-Rajkumar