Re: [RFC] mac80211: do not restart ps timer during scan

[Ben Greear <greearb@candelatech.com>]

On 02/01/2011 06:36 AM, Johannes Berg wrote:
> On Tue, 2011-02-01 at 20:04 +0530, Rajkumar Manoharan wrote:
>> While leaving oper channel, STA informs sleep state to AP to
>> stop sending data. Before sending ack for the nullfunc, AP is
>> still sending the data to STA which restarts ps_timer that
>> is causing unnecessary nullfunc exchange on timer expiry
>> when the STA is on offchannel. So don't restart ps_timer
>> on data reception during scan. This issue was identified by
>> the following warning.
>>
>> WARNING: at net/mac80211/tx.c:661 invoke_tx_handlers+0xf07/0x1330 [mac80211]
>> wlan0: Dropped data frame as no usable bitrate found while scanning and
>> associated. Target station: 00:03:7f:0b:a6:1b on 5 GHz band
>> Call Trace:
>>    [<ffffffffa0413ba7>] invoke_tx_handlers+0xf07/0x1330 [mac80211]
>>    [<ffffffffa0414056>] ieee80211_tx+0x86/0x2c0 [mac80211]
>>    [<ffffffffa0414345>] ieee80211_xmit+0xb5/0x1d0 [mac80211]
>>    [<ffffffffa04037e0>] ieee80211_dynamic_ps_enable_work+0x0/0xb0 [mac80211]
>>    [<ffffffffa04158cf>] ieee80211_tx_skb+0x4f/0x60 [mac80211]
>>    [<ffffffffa04026e6>] ieee80211_send_nullfunc+0x46/0x60 [mac80211]
>>    [<ffffffffa0403885>] ieee80211_dynamic_ps_enable_work+0xa5/0xb0 [mac80211]
>>
>> Signed-off-by: Rajkumar Manoharan<rmanoharan@atheros.com>
>> ---
>>   net/mac80211/rx.c |    4 +++-
>>   1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
>> index 7185c93..0e02ce9 100644
>> --- a/net/mac80211/rx.c
>> +++ b/net/mac80211/rx.c
>> @@ -1929,7 +1929,9 @@ ieee80211_rx_h_data(struct ieee80211_rx_data *rx)
>>   	dev->stats.rx_bytes += rx->skb->len;
>>
>>   	if (local->ps_sdata&&  local->hw.conf.dynamic_ps_timeout>  0&&
>> -	    !is_multicast_ether_addr(((struct ethhdr *)rx->skb->data)->h_dest)) {
>> +	    !is_multicast_ether_addr(
>> +		    ((struct ethhdr *)rx->skb->data)->h_dest)&&
>> +	    !local->scanning) {
>
> What if we're off-channel due to other work like P2P?

And, if I can get the scan-on-channel optimization patch in, this check
would need to be changed to check for scanning & off-channel instead of
just scanning.  I have a helper method in my patch to check if we're on
the oper-channel....

Thanks,
Ben

>
> johannes
>
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-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com