Re: [PATCH 3.14] mac80211: fix AP powersave TX vs. wakeup race

[Stanislaw Gruszka <sgruszka@redhat.com>]

On Thu, Feb 20, 2014 at 10:27:48AM +0100, Johannes Berg wrote:
> On Thu, 2014-02-20 at 10:21 +0100, Stanislaw Gruszka wrote:
> > On Thu, Feb 20, 2014 at 09:52:45AM +0100, Johannes Berg wrote:
> > > +
> > > +		/* sync with ieee80211_sta_ps_deliver_wakeup */
> > > +		spin_lock(&sta->ps_lock);
> > > +		/*
> > > +		 * STA woke up the meantime and all the frames on ps_tx_buf have
> > > +		 * been queued to pending queue. No reordering can happen, go
> > > +		 * ahead and Tx the packet.
> > > +		 */
> > > +		if (!test_sta_flag(sta, WLAN_STA_PS_STA)) {
> > > +			spin_unlock(&sta->ps_lock);
> > 
> > Actually I'm not sure if we should check if both WLAN_STA_PS_DRIVER 
> > and WLAN_STA_PS_STA flags are clear ?
> 
> This area is a bit confusing, but I don't think WLAN_STA_PS_STA will be
> clear until after WLAN_STA_PS_DRIVER is?

Hmm, actually looks like we call ps_deliver_wakeup() with WLAN_STA_PS_STA
flag currently cleared.

tatic void sta_unblock(struct work_struct *wk)
{
        if (!test_sta_flag(sta, WLAN_STA_PS_STA)) {
                local_bh_disable();
                ieee80211_sta_ps_deliver_wakeup(sta);
                local_bh_enable();

so on TX we should rather check WLAN_STA_PS_DRIVER flag .

Stanislaw