Re: [ath5k-devel] Race condition in CRDA calls?

["Luis R. Rodriguez" <lrodriguez@atheros.com>]

Just FYI, you want to use linux-wireless for reporting such things,
not ath5k-devel. Also I have been real busy in March (and stil am but
just trying to reply) so if I do not reply maybe others can. In
linux-wireless you'll likely get much more review/help than ath5k-devel
for this.

More below.

On Thu, Mar 25, 2010 at 10:01:54AM -0700, Lukáš Turek wrote:
> Hi,
> 
> I've been testing current vanilla 2.6.34 from git today on a computer with 
> three Atheros PCI cards and noticed a strange behavior: although all the 
> cards have the same regulatory domain (0x36), only the last one (phy2) had 
> the correct channels enabled, the other two (phy0 and phy1) stayed in US 
> regulatory domain with channels 52-140 disabled.
> 
> It seems the reply from CRDA for the first request gets into the kernel after 
> the last card is detected and all the replies get mixed up some way:
> 
> ath5k 0000:02:01.0: PCI INT A -> GSI 22 (level, low) -> IRQ 22
> ath5k 0000:02:01.0: registered as 'phy0'
> ath: EEPROM regdomain: 0x36
> ath: EEPROM indicates we should expect a direct regpair map
> ath: Country alpha2 being used: CZ
> ath: Regpair used: 0x36
> udev: renamed network interface eth0 to eth2
> udev: renamed network interface eth1_rename to eth0
> phy0: Selected rate control algorithm 'minstrel'
> ath5k phy0: Atheros AR5414 chip found (MAC: 0xa5, PHY: 0x61)
> ath5k 0000:02:02.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
> ath5k 0000:02:02.0: registered as 'phy1'
> ath: EEPROM regdomain: 0x36
> ath: EEPROM indicates we should expect a direct regpair map
> ath: Country alpha2 being used: CZ
> ath: Regpair used: 0x36
> cfg80211: Calling CRDA for country: CZ
> phy1: Selected rate control algorithm 'minstrel'
> ath5k phy1: Atheros AR5414 chip found (MAC: 0xa5, PHY: 0x61)
> ath5k 0000:02:03.0: PCI INT A -> GSI 19 (level, low) -> IRQ 19
> ath5k 0000:02:03.0: registered as 'phy2'
> ath: EEPROM regdomain: 0x36
> ath: EEPROM indicates we should expect a direct regpair map
> ath: Country alpha2 being used: CZ
> ath: Regpair used: 0x36
> cfg80211: Calling CRDA for country: CZ
> udev: renamed network interface wlan1 to wlan3
> phy2: Selected rate control algorithm 'minstrel'
> ath5k phy2: Atheros AR5414 chip found (MAC: 0xa5, PHY: 0x61)
> cfg80211: Calling CRDA for country: CZ
> udev: renamed network interface wlan1 to wlan2
> cfg80211: Current regulatory domain intersected:
> (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
> (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm)
> (2457000 KHz - 2482000 KHz @ 20000 KHz), (N/A, 2000 mBm)
> (2474000 KHz - 2483500 KHz @ 9500 KHz), (N/A, 2000 mBm)
> (5170000 KHz - 5250000 KHz @ 40000 KHz), (N/A, 2000 mBm)
> cfg80211: Current regulatory domain intersected:
> (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
> (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm)
> (2457000 KHz - 2482000 KHz @ 20000 KHz), (N/A, 2000 mBm)
> (2474000 KHz - 2483500 KHz @ 9500 KHz), (N/A, 2000 mBm)
> (5170000 KHz - 5250000 KHz @ 40000 KHz), (N/A, 2000 mBm)
> cfg80211: Current regulatory domain intersected:
> (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
> (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm)
> (2457000 KHz - 2482000 KHz @ 20000 KHz), (N/A, 2000 mBm)
> (2474000 KHz - 2483500 KHz @ 9500 KHz), (N/A, 2000 mBm)
> (5170000 KHz - 5250000 KHz @ 40000 KHz), (N/A, 2000 mBm)
> 
> Another reason might be udev messing up with device names. I will try to debug 
> this, but any hints would be greatly appreciated, because there's not much 
> info about the CRDA <-> kernel interaction.

You forgot to supply the kernel log of when cfg80211 loads, that
would have been helpful. After cfg80211 loads then leave a window
open with 'iw event -t' running. Then load ath5k, and if you want to
debug udev you can use udevadm, for example to debug only
kernel messages:

udevadm monitor --environment kernel

In short cfg80211 will do an intersection if the core had a regulatory
domain set for some reason and then a driver suggested to use another
country. If cfg80211 was world roaming and a driver then just used
a request for CZ then it shuld stick to CZ. If a second device comes
up with CZ then -EALREADY should be expected IIRC, if this is not happening
it smells like a bug.

  Luis