On Tue, Jun 21, 2011 at 11:13 AM, Arik Nemtsov <arik@xxxxxxxxxx> wrote:
> On Tue, Jun 21, 2011 at 07:55, Vivek Natarajan <vivek.natraj@xxxxxxxxx> wrote:
>>>
>>> + /* don't enter PS if dynamic PS is enabled and TX frames are pending */
>>> + if (local->hw.conf.dynamic_ps_timeout > 0 &&
>>> + !local->disable_dynamic_ps && drv_tx_frames_pending(local)) {
>>
>> netif_tx_stop_all_queues has to be called before checking
>> frames_pending(), so that we can make sure no data is transmitted in
>> the time between checking frames_pending and transmitting null data
>> frames. If it is not done, this might cause some power save states
>> mismatch between the AP and the station in some corner cases.
>
> That's a good point. But I guess its only relevant to drivers using
> IEEE80211_HW_PS_NULLFUNC_STACK.
> Still seems racy to me - even if queues are stopped it doesn't mean
> mac80211 is not in the middle of ieee80211_tx(). Is there a way to
> make sure?
Well, I can't find any way to stop this race. :)
Atleast the other race could be fixed with stop_queues.
How about the below patch? I am not sure about the disable_dynamic_ps
and its BT/WLAN antenna sharing. Please add that if you see it as
appropriate.
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index faca503..67ecad1 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -778,15 +778,14 @@ void ieee80211_dynamic_ps_enable_work(struct
work_struct *work)
}
spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
- if ((local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK) &&
- (!(ifmgd->flags & IEEE80211_STA_NULLFUNC_ACKED))) {
+ if (!(ifmgd->flags & IEEE80211_STA_NULLFUNC_ACKED)) {
netif_tx_stop_all_queues(sdata->dev);
if (drv_tx_frames_pending(local))
mod_timer(&local->dynamic_ps_timer, jiffies +
msecs_to_jiffies(
local->hw.conf.dynamic_ps_timeout));
- else {
+ else if (local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK) {
ieee80211_send_nullfunc(local, sdata, 1);
/* Flush to get the tx status of nullfunc frame */
drv_flush(local, false);
Vivek.
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