Vivek Natarajan wrote:
> On Tue, Feb 15, 2011 at 12:46 PM, Sujith <m.sujith@xxxxxxxxx> wrote:
> > Vivek Natarajan wrote:
> >> void ieee80211_dynamic_ps_timer(unsigned long data)
> >> diff --git a/net/mac80211/status.c b/net/mac80211/status.c
> >> index 010a559..51caa0d 100644
> >> --- a/net/mac80211/status.c
> >> +++ b/net/mac80211/status.c
> >> @@ -315,7 +315,10 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
> >> (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) &&
> >> !(info->flags & IEEE80211_TX_CTL_INJECTED) &&
> >> local->ps_sdata && !(local->scanning)) {
> >> - if (info->flags & IEEE80211_TX_STAT_ACK) {
> >> + if ((info->flags & IEEE80211_TX_STAT_ACK) &&
> >> + (local->ps_sdata->u.mgd.flags & IEEE80211_STA_PS_PENDING)) {
> >> + ieee80211_stop_queues_by_reason(&local->hw,
> >> + IEEE80211_QUEUE_STOP_REASON_PS);
> >
> > I am not too familiar with the PS code, but why are the queues being stopped
> > after the nullfunc frame has been sent out and acked ? And it is a bit unclear why
> > the new flag IEEE80211_STA_PS_PENDING is required at all... Can't IEEE80211_STA_NULLFUNC_ACKED
> > be used to fix this race ?
>
> The new flag is required to prevent mac80211 to go into power save if
> a frame is sent during the interval of sending nullfunc frame and
> receiving ack for that. The queues are stopped to avoid sending any
> frame between the interval of receiving ack and setting CONF_PS and it
> mainly addresses the race that Johannes pointed out in the previous
> version.
Well ok, I still don't grok the details, though. :)
Sujith
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