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Subject: Re: VIMAGE crashes on 9.x with hotplug net80211 devices
From: Adrian Chadd <adrian@freebsd.org>
To: Marko Zec <zec@fer.hr>
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On 21 October 2012 12:36, Marko Zec <zec@fer.hr> wrote:

> The right approach would be to do a single CURVNET_SET(vnet0) /
> CURVNET_RESTORE() somewhere near the root of the call graph being triggered
> by the hotplug attach event.  Not having any hotpluggable hardware at hand
> I cannot be more specific where that place could be...

Right; would that be at the net80211 side, or something higher up (eg
at device_attach, which gets called from the cardbus/pci bridge
enumeration code.)

> But most certainly doing CURVNET_SET(vnet0) on detach events would be wrong:
> since ifnets may be assignet to non-default vnets,
> CURVNET_SET(ifp->if_vnet) should be more appropriate there.

Thanks for that. I'll look at adding that in my next debug pass.

> Another thing that may help could be turning on options VNET_DEBUG when, as
> that should reveal excessive (and probably redundant) CURVNET_SET()
> recursions.

I've spotted a couple, however the crashing here is the important bit. :-)

So - why is it that the V_* variables are NULL pointers at this stage?
I thought the kernel would've been running with a default vnet context
of vnet0? Why doesn't this impact other network device hotplugging? Or
does it, and noone noticed?



Adrian