Re: [PATCH 1/2] mac80211: Dont allow to wake up netif tx queues while on off channel

[Johannes Berg <johannes@sipsolutions.net>]

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@atheros.com>
> ---
>  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()

johannes