fxp0 and vlan panic

[Randy Bush]

>> Fatal trap 12: page fault while in kernel mode
>> fault virtual address   = 0x80808517
>> fault code              = supervisor read, page not present
>> instruction pointer     = 0x8:0xc047d2d0
>> stack pointer           = 0x10:0xd3f78c88
>> frame pointer           = 0x10:0xd3f78cac
>> code segment            = base 0x0, limit 0xfffff, type 0x1b
>>                         = DPL 0, pres 1, def32 1, gran 1
>> processor eflags        = interrupt enabled, resume, IOPL = 0
>> current process         = 15 (irq5: fxp0)
>> [thread pid 15 tid 100008 ]
>> Stopped at      fxp_intr_body+0xd0:     cmpw    $0,0(%esi)
>> db> trace
>> Tracing pid 15 tid 100008 td 0xc155fb80
>> fxp_intr_body(c161a000,c161a000,40,ffffffff,c0630cb6) at
>> fxp_intr_body+0xd0 fxp_intr(c161a000,0,0,0,0) at fxp_intr+0x141
>> ithread_loop(c1551a00,d3f78d48,0,0,0) at ithread_loop+0x1a8
>> fork_exit(c04da530,c1551a00,d3f78d48) at fork_exit+0x7f
>> fork_trampoline() at fork_trampoline+0x8
>> --- trap 0x1, eip = 0, esp = 0xd3f78d7c, ebp = 0 ---
> 
> Hmm, can you get the panic to occur when interrupt coalescing is
> turned on?  'ifconfig fxp0 link0'

the panic is rare, takes a week or two to happen.  so it is hard to
know if changing to interrupt coalescing will fix.  but i will try
it after a while; as i am testing mux's latest patch kit right now.
but thanks for the clue!

randy