Re: madwifi makes board crash after bursting packets

Hi Dennis-

I run almost the same thing you do.
Alix 3D2 boards with Ubiquiti XR5 (atheros 5414) in bottom slot and 
Wistron CM-9 in top slot on some setups and an Ubiquiti SR2 on others.  
They all have the XR5 for the 5.8 ghz side of things.

I run the XR5's in ahdemo mode w/ OLSR to do a mesh setup.
I'm using MADWIFI 0.9.4.1 (from the 0.9.4 branch from not too long ago) 
with kernel 2.6.26.3
I'm able to get similar throughput -- possibly even a little more (maybe 
28 megabits ... but can't remember my "peak" number).

I've also run the XR5 as an AP with an Ubiquiti SR5 as client on same 
MADWIFI 0.9.4.1 on kernel 2.6.28.4 on a setup at my day job.
The XR5 AP never crashes or anything -- we have a constant stream of UDP 
traffic every 10 ms in both directions and only miss 1 packet a handful 
of times per hour and it runs for days.
We can also stream data over a TCP connection in parallel with the UDP 
stuff but nowhere near 23Mbit/s and it works fine.

We have a problem with the SR5 (Ubiquiti's earlier 400 mW radio that 
predates the XR5) that uses the older Atheros 5213
About once per month, it will have it's Tx queue get hung up.  The board 
can't transmit but can still receive just fine.
The Tx function in the driver re-schedules a softirq and gets in some 
type of a loop and you see a Ksoftirqd taking up tons of CPU making 
everything very sluggish.
It looks like this problem mentioned in the mailing list from some time ago:

http://article.gmane.org/gmane.linux.drivers.madwifi.user/15084

You may want to try and get on the serial console of your Alix when the 
problem is happening and see if you can manage to get CPU time to get 
logged in and run "top" or something and see if Ksoftirqd is killing the 
CPU.  You'll also see the Tx packets increasing on the athX interface, 
but not on the corresponding wifiX interface.

This may totally not be your problem, but may be worth checking.

My only other suggestion would be to try an XR5 in place of your alfa 
board and see if the problem goes away.
This is based on the fact that I really have zero issues with my XR5 
whether ahdemo mode or AP mode.  Maybe I haven't pushed them enough like 
you.

As one more side point -- I have an older Soekris net4826 I use as an AP 
in my house that runs the same software with CM-9 and it uses hostapd 
with AES256 encryption etc. (probably not quite as new) and that setup 
runs w/ no issues for the general use AP in my house.  So I know the 
software combination should be ok.

Good Luck

-Eric Malkowski

Dennis Borgmann wrote:
> Hello madwifi-lists!
> Hello hostapd-list!
>
> Since I do not know, which of the madwifi-lists is still active and
> read, I post my question to both madwifi-users and madwifi-dev.
>
> See my setup below. If I burst data from one point to the other (lets
> say with 'scp' a file of about 2GB size) at full speed (with the
> distance I got right now (1m) about 23Mbit/s) the AP crashes after quite
> some time (~1 hour). I am not able to check what is going on on the
> machine that runs the AP, because the attached serial console won't
> respond anymore and I cannot establish any connection to the AP anymore.
> It is still transmitting beacons and can be recognized by any wireless
> station (with the one being the client with 'iwlist ath0 scan' and with
> a laptop not involved in the wireless connection on my desk with 'iwlist
> wlan0 scan'). So I fear, I cannot give that much debug output, since I
> can't access the AP anymore.
>
> Rebooting the AP solves the problem immediately and the client connects
> to the AP directly making data transfer possible again.
>
> I could not reproduce this problem with low traffic, since I did a 'ping
> -f IP' last night and it was still up this morning after 14 hours.
>
> Running an iperf yesterday got the client crashed. Same problem - I
> couldn't connect to it anymore via the serial console. Since it is not
> transmitting beacons while being a station, I cannot tell, if the
> wireless device was still up in any way.
>
> My setup:
>
> madwifi 0.9.4 - running on AP and Client
> hostapd v0.6.9 on AP side with RSN-encryption
> wpa_supplicant v0.6.9 on client side with RSN-encryption
> 2 PC Engines ALIX3D2-Boards (x86, 500MHz, headless systems)
> Alfa networks MiniPCI-WAN cards with Atheros AR5414 chipset
>
> I am using madwifi-0.9.4 on a productive system and I am not able to
> switch to a newer driver within a recent kernel in a rush. Therefore I'd
> like to stick with it, if that's possible.
>
> Does this problem sound familiar to anyone? Are there any hints, what I
> still might try before I am urged to move to a recent driver?
>
> Thanks for any hint.
>
> Kind regards,
> Dennis
>
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Beautiful is writing same markup. Internet Explorer 9 supports
standards for HTML5, CSS3, SVG 1.1,  ECMAScript5, and DOM L2 & L3.
Spend less time writing and  rewriting code and more time creating great
experiences on the web. Be a part of the beta today
http://p.sf.net/sfu/msIE9-sfdev2dev