iwlagn + some accesspoint = hardlock

[Nils Radtke <Nils.Radtke@Think-Future.de>]

  Hello there,

 today a somewhat unprecise report:

When connecting to the local university's wireless APs, rather regularly 
presumably the kernel crashes.

So, connecting to one of those the system hardlocks. No panic LED blinking, no mouse cursor moving, 
no magic sysreq key working. Poweroff is the only way to revive the machine. Until the upcoming
lock-up.

What might serve as a hint: using knemo and kwifimanager (with wpa_supplicant in the bg) it feels like it is 
freezing more frequently. Not running kwifimanager seems to reduce the frequency w/o however eliminating it
completely. Sometimes iceweasel has been touched and then the crash occurred. 
Maybe some TX (or subsequent RX) provokes the crash? Some idea that also came up was that accessing iwlagn 
drivers isn't clean when it's happening from more that one place at the same time 
(->wpa_supplicant + kwifimanager)?

This behaviour is currently only known to happen in this exact place/location. So one assumption is that it
is somehow correlated to a particular type of access point, firmware respectively. Nonetheless, even
if there's some fw sending kill packets, the kernel should not crash, obviously.

The access points in range are of type:

- one 0:1d:8b PIRELLI BROADBAND SOLUTIONS 
- couple of those 0:40:96 Cisco Systems, Inc.
- one 0:1a:70 Cisco-Linksys

This notebook has no serial port, so we haven't been able to get a glimpse on what is happening at that 
precise moment. xconsole or dmesg haven't been helpful as the system just freezes and that's it.

Comments, ideas, fixes welcome...

Cheers,

  Nils