On Wed, Jun 30, 2010 at 03:47:06PM +0530, Johannes Berg wrote: > On Wed, 2010-06-30 at 03:15 -0700, Vasanthakumar Thiagarajan wrote: > > Drivers are not supposed to call ieee80211_wake_queue() while operating > > on off channel during sw scanning, but there is no clear way for > > the driver to know that it is operating on off channel during scanning. > > There are cases (unavailablity/availability of tx buffers in ath9k, for > > example) where driver needs to stop/restart tx queues during background > > scanning state, this might result in waking up the corresponding netif > > tx queue when the device is on off channel which is not desired. This > > patches fixes this by checking SCAN_OFF_CHANNEL bit in scanning before > > restarting the tx queue. > > > > Signed-off-by: Vasanthakumar Thiagarajan <vasanth@xxxxxxxxxxx> > > --- > > net/mac80211/util.c | 3 ++- > > 1 files changed, 2 insertions(+), 1 deletions(-) > > > > diff --git a/net/mac80211/util.c b/net/mac80211/util.c > > index a54cf14..1938a67 100644 > > --- a/net/mac80211/util.c > > +++ b/net/mac80211/util.c > > @@ -277,7 +277,8 @@ static void __ieee80211_wake_queue(struct ieee80211_hw *hw, int queue, > > > > __clear_bit(reason, &local->queue_stop_reasons[queue]); > > > > - if (local->queue_stop_reasons[queue] != 0) > > + if ((local->queue_stop_reasons[queue] != 0) || > > + test_bit(SCAN_OFF_CHANNEL, &local->scanning)) > > /* someone still has this queue stopped */ > > return; > > That doesn't seem to make sense, since we treat driver and scan stop > status separately via wake_queue_by_reason() I dont know if I explained the issue properly. The issue here is waking up the queues by driver during scan, particularly when operating on off channel. With ath9k, there is a possibility that ieee80211_wake_queue() can be called while moving from operational channel (during channel set in driver). In this case driver still needs to be allowed to clear the bit in queue_stop_reasons[] but not wake up the tx queue. Vasanth -- 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
