Page fault in IFNET_WLOCK_ASSERT [if.c and pccbb.c]

Julian Elischer julian at
Sun Oct 18 06:42:41 UTC 2009

Harsha wrote:
> Hi Robert,
> Apologies for not getting earlier.
> On Mon, Oct 12, 2009 at 6:46 AM, Robert N. M. Watson
> <rwatson at> wrote:
>> Looks like a NULL pointer dereference, so perhaps a more traditional bug --
>> could you convert ifindex_alloc_locked+0x71 to a line of code? You can do
>> this using kgdb on the kernel symbols file, perhaps "l
>> *ifindex_alloc_locked+0x71".
> It is the for loop in ifindex_alloc_locked() function-
>  for (idx = 1; idx <= V_if_index; idx++)
> idx is a local variable, so I figured it is V_if_index is what is
> causing the page fault. It does look like a NULL pointer reference - I
> see that V_if_index comes from that  vnet instance's value and uses
> the macro VNET_VNET_PTR() down the chain. Since the call chain is
> coming from a new thread cbb_event_thread, I believe that this
> thread's vnet context needs to be set using CURVNET_SET().

but only if you have options VIMAGE defined. if not then CURVNET_SET()
is a NOP

> I'll try this tomorrow, but if think I'm not on the right track or
> want me to try something else please let me know.
> Many thanks,
> Harsha
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