On Mon, 2012-03-19 at 14:40 +0100, Stanislaw Gruszka wrote:
> > > +static void ieee80211_free_tid_rx(struct tid_ampdu_rx *tid_rx)
> > > {
> > > - struct tid_ampdu_rx *tid_rx =
> > > - container_of(h, struct tid_ampdu_rx, rcu_head);
> > > int i;
> > >
> > > for (i = 0; i < tid_rx->buf_size; i++)
> > > @@ -90,10 +88,12 @@ void ___ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
> > > ieee80211_send_delba(sta->sdata, sta->sta.addr,
> > > tid, WLAN_BACK_RECIPIENT, reason);
> > >
> > > + synchronize_rcu();
> > > +
> > > del_timer_sync(&tid_rx->session_timer);
> > > del_timer_sync(&tid_rx->reorder_timer);
> > >
> > > - call_rcu(&tid_rx->rcu_head, ieee80211_free_tid_rx);
> > > + ieee80211_free_tid_rx(tid_rx);
> >
> > Hmmm. That synchronize_rcu() could become rather expensive. I've been
> > trying to reduce our use of synchronize_rcu() now.
>
> Expensive in what sense? Since we are in process context we are allowed
> to sleep, and some other processes will run while we sleep.
It takes a long time, and we have to wait for it. So for example, it
could delay roaming by another 100ms or however long it takes (yes, it
can take a very long time, we've seen up to 200ms I think)
johannes
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