On Tue, Jun 21, 2011 at 07:55, Vivek Natarajan <vivek.natraj@xxxxxxxxx> wrote:
> On Sun, Jun 19, 2011 at 1:02 AM, Arik Nemtsov <arik@xxxxxxxxxx> wrote:
>> Use the tx_frames_pending() driver callback to determine if Tx frames are
>> pending for its internal queues. If so postpone the dynamic PS timeout
>> to avoid interrupting Tx traffic.
>>
>> The commit e8306f989483e4b97a8b37dd268de6c8c6f35e75 enabled this
>> behavior for drivers with IEEE80211_HW_PS_NULLFUNC_STACK. We enable this
>> for all drivers supporting dynamic PS.
>>
>> This patch helps improve performance in noisy environments.
>>
>> Signed-off-by: Arik Nemtsov <arik@xxxxxxxxxx>
>> ---
>> net/mac80211/mlme.c | 22 +++++++++++++---------
>> 1 files changed, 13 insertions(+), 9 deletions(-)
>>
>> diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
>> index a41f234..3a1699b 100644
>> --- a/net/mac80211/mlme.c
>> +++ b/net/mac80211/mlme.c
>> @@ -758,19 +758,23 @@ void ieee80211_dynamic_ps_enable_work(struct work_struct *work)
>> if (local->hw.conf.flags & IEEE80211_CONF_PS)
>> return;
>>
>> + /* 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.
>
> Vivek.
>
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?
Arik
--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
