Page fault in IFNET_WLOCK_ASSERT [if.c and pccbb.c]
julian at elischer.org
Mon Oct 19 04:22:37 UTC 2009
> On Sat, Oct 17, 2009 at 11:42 PM, Julian Elischer <julian at elischer.org> wrote:
>> Harsha wrote:
>>> <rwatson at freebsd.org> 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
>>> 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 do have the VIMAGE options turned on.
> Can someone tell me what is the right way to add the vnet context to
have you read the vimage porting document at:
> I tried adding context in two locations-
> 1. In cbb_insert() as-
> 2. In if_alloc() as-
> or as
> ifp = malloc(sizeof(struct ifnet), M_IFNET, M_WAITOK|M_ZERO);
> #ifdef VIMAGE
> ifp->if_vnet = curvnet;
> if (ifp->if_home_vnet == NULL)
> ifp->if_home_vnet = curvnet;
CURVNET_SET sets curvnet but you are using it already, 3 lines above.
> But in all the cases I get a warning/error about unused variable
> 'saved_vnet' like this-
> cc1: warnings being treated as errors
> /usr/src/sys/net/if.c: In function 'if_alloc':
> /usr/src/sys/net/if.c:418: warning: unused variable 'saved_vnet'
> The backtrace is in the link I posted earlier.
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