Re: Compat-wireless-3.2-rc6-3 is broken for rt2860 device

On Thu, Jan 5, 2012 at 9:44 AM, Andreas Hartmann
[off-list ref] wrote:

Helmut Schaa schrieb:

quoted

Hi,

Am Mittwoch, 4. Januar 2012, 09:38:02 schrieb Andreas Hartmann:

quoted

Helmut Schaa schrieb:

quoted

quoted

Removing this patch

mac80211: retry sending failed BAR frames later instead of tearing down
aggr (http://www.spinics.net/lists/linux-wireless/msg76379.html) makes
it working again.

Device is: RaLink RT2800 802.11n PCI

What's the client device connected to the rt2x00 AP?

It's a rt3572 usb chip (Linksys WUSB600N v2), driven with the rt3572sta
module.

quoted

Mind to send a
802.11 capture wen this stall happens?

Andreas provided me with a capture now. The interesting part is that
the rt2x00 AP sends bursts of BARs with the same sequence number when
the stall happens. I only had a quick look at the code in question but
couldn't see anything wrong at a first glance.

Some additional information:

- The AP initiates BARs for 6 different, successive sequence numbers.
- The first 5 sequence numbers are finished after sending of about 8 (!)
BAR's.
Important: each BAR is responded *instantly* by the STA.
- The BAR for the next sequence number is sent "endless" though the STA
responses to each BAR instantly again.


Another thing: it is striking, that the performance from STA -> AP is at
max 8,5 MBit/s, whereas the performance from AP -> STA can be 15 MBit/s
(all measured with netperf).


Could it be, that somewhere in the stack of the AP the response packet
from STA -> AP get's lost or ignored or blocked?

The BlockAck is solely handled in hardware. But I need to check, maybe
the BAR tx status is reported as unacknowledged when the BA contains
a BA bitmap of only zeros ...

Don't know when I can find time to do this but if you like to test something
you could try to add some printks in the rt2x00 tx status path to see if any
BAR frames are reported as acknowledged (and if these have a bitmap != 0).

Helmut