IGMP+WiFi panic on recent kernel - in igmp_fasttimo()
Coleman Kane
cokane at FreeBSD.org
Tue Mar 17 06:06:50 PDT 2009
On Tue, 2009-03-17 at 08:12 +0000, Bruce Simpson wrote:
> Sam Leffler wrote:
> > It is the same issue but the root cause is unclear. There is much
> > code that does assumes ifma_protospec might be NULL and checks for
> > it. In my case (creating a wlan ifnet and then destroying it on
> > eject) the patch below is sufficient. I don't care to dig right now
> > to understand how this stuff is supposed to work; it should be clear
> > from comments etc but the code is lacking.
> >
>
> This is just to say I've tried to reproduce the 802.11 related
> panics, however have hit a brick wall because the PCI-CardBus bridge
> does not seem to detect anything in its slot. (1U Itox Expanding Dragon
> industrial PC w/a SiteCom branded Ricoh RL475 cardbus card). I tried
> unloading if_fxp with IGMPv3 active on the ifnet, and didn't see any
> panic, I'm assuming this is OK for the time being.
>
> Qing Li volunteered to test IGMPv3 out for any VLAN related issues
> -- I understand it stacks ifnets in a similar way to that of 802.11 --
> however I have had no feedback from him since last week.
> So I'm waiting for a HEAD build to a USB2 stick to finish, so I can
> try testing nondestructively on my laptop, where I know for sure that
> the PCI-CardBus bridge slot works, and I can detach an 802.11 card on
> the fly.
>
> Re ifma_protospec: Yes, there are tricks in the ifnet/in layer which
> set it to NULL and look for it to be NULL. I ended up doing it this way
> mainly because adding reference counting to ifnet would have simply been
> too much work, and it's really a ball that needs to be kicked around at
> a dev summit. However time presses on and it's better to get SOMETHING
> out there.
> Most likely the IGMPv3 changes are hitting this in the 802.11 case
> somehow, I don't have a complete picture of how/why/what's going on, and
> have been relying on feedback from others so far.
>
> cheers
> BMS
>
Today I played with it a bit. I've been unable to produce the crash on
my wired (if_bge) interface, however it happens regularly on my wireless
(ndis0/wlan0) interface. I was unable to get a core dump for other
reasons.
However, on my system I do not get the crash if I turn off avahi_daemon
(set avahi_daemon_enable="NO" in /etc/rc.conf). I tried booting to
single user, ran dhclient on wlan0 (after setting it up properly), and
then proceeded to boot the system multi-user. As soon as avahi went
live, the kernel panicked, as above.
If you are looking for a reliable test case, this might be it for you,
but I think you need a wlan interface to test it with:
* Install net/avahi from ports
* Set avahi_daemon_enable="YES" in rc.conf
* Configure VAP params for wlan0 card in rc.conf
* Log in and run "dhclient wlan0" to trigger the panic
--
Coleman Kane
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