On 05/18/11 14:41, Mohammed Shafi wrote: > On Wed, May 18, 2011 at 5:26 PM, Walter Goldens > <goldenstranger@xxxxxxxxx> wrote: >>>> A very peculiar bug. >>>> >>>> With compat-wireless from 16.05 a nasty bug started to >>> manifest itself. Right around association time, the >>> rt2800usb causes kernel panic. The system freezes and the >>> Caps Lock and Num Lock leds on the keyboard begin to flash. >>> >>> also ath9k, iwlagn. >>> >>>> >>>> Unfortunately there are no recoverable traces after >>> the system failure to aid this bug report or to indicate its >>> origin. >>>> >>>> I believe it may somehow be related to Ubuntu's >>> network-manager. If I turn off the network-manager service, >>> I can go into monitor mode for example, but if >>> network-manager is running and I plug my USB dongle, it >>> starts to associate, a second or two later the system is in >>> complete meltdown. >>> >>> same thing, monitor mode worked perfectly fine. >>> >>>> >>>> Nothing concrete, but a hunch is telling me this has >>> something to do with the association mechanism of the >>> rt2800usb. Compat-wireless from few days back exhibits no >>> such foul play. >>> >>> yes just right at the association complete freeze. >>> >> >> That's strange. I wonder what's the connection with this bug and network-manager. Because when I manually tried to associate, dmesg reported the association attempt timed out. > > no even when we use iw dev connect command we can see the panic. Yeah, I've seen this freeze as well using one of the later compat-wireless packages using just iw and wpa_supplicant to bring up the card. This is on all sorts of rt2x00 supported devices. However, I don't believe this to be an rt2x00-specific bug, as exactly the same rt2x00 sources inside a compat-wireless-2.6.39rc7 package do not produce the freeze. > some expert suspected that there is a chance of kfree_rcu in > compat-wireless may have caused the problem > That's where my suspicion is as well, but I didn't have the time to further investigate. Since my focus was on rt2x00 I used the compat-wireless-2.6.39rc7 package to test my patches. I only did a quick check, and the kfree_rcu compatibility fix that was done in compat-wireless did seem to match the kfree_rcu code is present in linux-next, but maybe there is an odd side-effect. --- Gertjan -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
