debugging frequent kernel panics on 8.2-RELEASE

[Andriy Gapon]

on 15/08/2011 17:56 Steven Hartland said the following:
> 
> ----- Original Message ----- From: "Andriy Gapon" <avg at FreeBSD.org>
> To: "Steven Hartland" <killing at multiplay.co.uk>
> Cc: <freebsd-stable at FreeBSD.org>
> Sent: Monday, August 15, 2011 2:20 PM
> Subject: Re: debugging frequent kernel panics on 8.2-RELEASE
> 
> 
>> on 15/08/2011 15:51 Steven Hartland said the following:
>>> ----- Original Message ----- From: "Andriy Gapon" <avg at FreeBSD.org>
>>>
>>>
>>>> on 15/08/2011 13:34 Steven Hartland said the following:
>>>>> (kgdb) list *0xffffffff8053b691
>>>>> 0xffffffff8053b691 is in vm_fault (/usr/src/sys/vm/vm_fault.c:239).
>>>>> 234             /*
>>>>> 235              * Find the backing store object and offset into it to begin the
>>>>> 236              * search.
>>>>> 237              */
>>>>> 238             fs.map = map;
>>>>> 239             result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
>>>>> 240                 &fs.first_object, &fs.first_pindex, &prot, &wired);
>>>>> 241             if (result != KERN_SUCCESS) {
>>>>> 242                     if (result != KERN_PROTECTION_FAILURE ||
>>>>> 243                         (fault_flags & VM_FAULT_WIRE_MASK) !=
>>>>> VM_FAULT_USER_WIRE) {
>>>>>
>>>>
>>>> Interesting... thanks!
[snip]
> (kgdb) x/512a 0xffffff8d8f357210

This is not conclusive, but that stack looks like the following recursive chain:
vm_fault -> {vm_map_lookup, vm_map_growstack} -> trap -> trap_pfault -> vm_fault
So I suspect that increasing kernel stack size won't help here much.
Where does this chain come from?  I have no answer at the moment, maybe other
developers could help here.  I suspect that we shouldn't be getting that trap in
vm_map_growstack or should handle it in a different way.

> 0xffffff8d8f357210:     0xffffff8d8f357280      0xffffffff805807d3 <trap_pfault+307>
> 0xffffff8d8f357220:     0x0     0xffffff8d8f357370
> 0xffffff8d8f357230:     0xffffff06b7f9c000      0x30
> 0xffffff8d8f357240:     0x100000000     0x0
> 0xffffff8d8f357250:     0x0     0x9
> 0xffffff8d8f357260:     0xc     0xffffff8d8f357370
> 0xffffff8d8f357270:     0xffffff06b7f9c000      0x0
> 0xffffff8d8f357280:     0xffffff8d8f357360      0xffffffff80580e0f <trap+991>
> 0xffffff8d8f357290:     0x0     0x0
> 0xffffff8d8f3572a0:     0x80074e49e     0x2
> 0xffffff8d8f3572b0:     0x80071cba0     0x80071cdc0
> 0xffffff8d8f3572c0:     0x80071c9a0     0x0
> 0xffffff8d8f3572d0:     0x0     0x0
> 0xffffff8d8f3572e0:     0x0     0x0
> 0xffffff8d8f3572f0:     0x0     0x0
> 0xffffff8d8f357300:     0x80074e49e     0x1
> 0xffffff8d8f357310:     0x80071cba0     0x80071cdc0
> 0xffffff8d8f357320:     0x80071c9a0     0x0
> 0xffffff8d8f357330:     0x0     0x4
> 0xffffff8d8f357340:     0xffffff070b5a48c0      0xffffff06b7f9c000
> 0xffffff8d8f357350:     0x0     0xffffffff8083e920 <vmspace0>
> 0xffffff8d8f357360:     0xffffff8d8f357430      0xffffffff80568f04 <calltrap+8>
> 0xffffff8d8f357370:     0xffffff070b5a48c0      0x3
> 0xffffff8d8f357380:     0xffffff8d8f357440      0x0
> 0xffffff8d8f357390:     0xffffff8d8f357440      0x30
> 0xffffff8d8f3573a0:     0xffffff06b7f9c000      0x4
> 0xffffff8d8f3573b0:     0xffffff8d8f357430      0xffffffff8083e920 <vmspace0>
> 0xffffff8d8f3573c0:     0xffffff06b7f9c000      0xffffff070b5a48c0
> 0xffffff8d8f3573d0:     0xffffff06b7f9c000      0x0
> 0xffffff8d8f3573e0:     0xffffffff8083e920 <vmspace0>   0x1b00130000000c
> 0xffffff8d8f3573f0:     0x30    0x3b003b00000001
> 0xffffff8d8f357400:     0x0     0xffffffff80384632 <lim_rlimit+18>
> 0xffffff8d8f357410:     0x20    0x10206
> 0xffffff8d8f357420:     0xffffff8d8f357430      0x28
> 0xffffff8d8f357430:     0xffffff8d8f357450      0xffffffff80384681 <lim_cur+17>
> 0xffffff8d8f357440:     0x4     0xffffff070b5a48c0
> 0xffffff8d8f357450:     0xffffff8d8f357500      0xffffffff80543ffd
> <vm_map_growstack+93>
> 0xffffff8d8f357460:     0xffffff8d8f357470      0xffffff8d8f3576d8
> 0xffffff8d8f357470:     0xffffff8d8f357500      0xffffffff80544ef8
> <vm_map_lookup+808>
[trim]

-- 
Andriy Gapon