Re: Mysterious hangs - cfg80211 - ath9k

[Jon Wikne <Jon.Wikne@cern.ch>]

On 06/28/2012 04:22 PM, Mohammed Shafi wrote:
> Hi,
>
> On Thu, Jun 28, 2012 at 7:33 PM, Jon Wikne<Jon.Wikne@cern.ch>  wrote:
>> On 06/19/2012 08:52 PM, Jon Wikne wrote:
>>>
>>> On 06/19/2012 11:39 AM, Mohammed Shafi wrote:
>>>>
>>>> On Tue, Jun 19, 2012 at 1:34 PM, Jon Wikne<Jon.Wikne@cern.ch>  wrote:
>>>>>
>>>>> Hi List,
>>>>>
>>>>> I am experiencing a puzzling problem with WLAN on a Toshiba Qosmio
>>>>> F750 laptop, running CERN SLC 5.8 (mostly identical to RHEL 5.8),
>>>>> but with kernel 2.6.39.4. (The kernel that came with the distro did
>>>>> not work properly with WLAN on this machine at all.)
>>>>
>>>>
>>>> please quickly try
>>>>
>>>> http://linuxwireless.org/en/users/Download#Where_to_download_bleeding_edge
>>>
>>>
>>> I tried to install compat-wireless-2012-05-10. It worked for 4½ hours,
>>> then same problem.
>>>
>>> Maybe there is something wrong with my understanding here, but I do not
>>> see why the "cfg80211: Calling CRDA to update world regulatory domain"
>>> should occur hours after the connection has been established, and what
>>> triggers it, apparently at random....
>>>
>>>> or the latest wireless testing tree
>>>>
>>>> http://linuxwireless.org/en/developers/Documentation/git-guide#Cloning_latest_wireless-testing
>>>
>>>
>>> Is there a reason to believe it could make a difference if I try
>>> this too?
>>
>>
>> Now I downloaded this (more than 1GB), just to realize that it is a
>> complete kernel tree for kernel 3.5.0-rc3. I don't really feel ready
>> for an experimental upgrade from 2.6.39.4 to that right now....
>>
>> With basis in compat-wireless-2012-05-10 I tried to comment out the
>> call to call_crda in net/wireless/reg.c and return -EALREADY in line
>> 1483, just to see if that circumvented the problem. It did not. The
>> damage (whatever that might be) already seems to be done _before_ the
>> call_crda is made in reg.c.
>>
>> I am a bit at a loss as to how to proceed. There are several things
>> i do not understand.
>>
>> 1) The call to update CRDA (even with my crude, experimental, dummy
>> return) seems to cause no trouble when it is done the first time
>> the line comes up. Could someone please explain to me what causes
>> the subsequent calls at highly irregular intervals, and why that
>> seems to be necessary or desirable?
>>
>> 2) Is this a known problem that is being worked on (in which case I
>> will just shut up and wait), or am I the first to report it?
>>
>> Thanks in advance for any further info or suggestions.
>
> please provide the complete log.

There is nothing relevant in the regular logs apart from lines like
these:

Jun 20 17:11:09 redcat kernel: cfg80211: Calling CRDA to update world 
regulatory domain
Jun 20 17:11:09 redcat kernel: ath9k 0000:03:00.0: PCI INT A -> GSI 18 
(level, low) -> IRQ 18

when the WLAN comes up normally, and and an additional line like this:

Jun 20 17:42:32 redcat kernel: cfg80211: Calling CRDA to update world 
regulatory domain

when it fails / hangs at some unpredictable point in time later.

> you can also enable ath9k debugging.
> sudo modprobe -v ath9k debug=0x601
> http://linuxwireless.org/en/users/Drivers/ath9k/debug
> so you need to bring the interface up/down to make it working right ?

OK, done. I don't know when the error might reappear, but I will copy
the /sys/kernel/debug/ieee80211/phy0/ tree and put on some server for
forensics when it does. There is a lot of info there which I do not
know how to interpret.

Regards,
-- Jon