random MIPS TLB exceptions?

[Adrian Chadd]

I unfortunately didn't save the console log :( I'll make sure I do next
time.

For ref, twas an RSPRO w/ ath wifi hardware. Running a read-only AP image.
No mounted USB disks or normal running system.

It was in the raw xmit code path and the code itself and around it made no
sense from a crash perspective - registers pointed at correct values /
addresses.

A reboot of exactly the same kernel didn't show a problem.

I'll try to reproduce exactly what I did yesterday (which was start it up,
then do some console serial IO whilst doing network IO) But yeah, it's
tricky to track down.

This was less about "this is what the problem is" and more a solicitation
for further information from people who may have seen random crashes and
rebooted..




-adrian


On 16 September 2013 10:16, Juli Mallett <jmallett at freebsd.org> wrote:

> On Mon, Sep 16, 2013 at 1:09 AM, Adrian Chadd <adrian at freebsd.org> wrote:
>
>> Hiya,
>>
>> I just saw a random panic on MIPS in kernel code where it shouldn't occur.
>> It hasn't happened after a reboot.
>>
>> Has anyone else seen occasional TLB exceptions?
>>
>
> Not enough information.  There is no "MIPS" kernel and no "MIPS" platform,
> so it's hard to make sense of the problem space here.  My instinct would be
> that sporadic issues of this kind could often be caused by a driver or
> similar, so it would be helpful to know what hardware you're using, what
> kernel you're running, and what kind of workload is going on.  It could be
> something that others simply haven't hit for circumstantial reasons (say, a
> problem related to swapping), or based on what drivers and hardware are
> in-use.  (Is there wireless involved?  Doesn't that bring in all kinds of
> timers and occasional beacons that could be received?  That kind of thing
> seems like it could result in sporadic crashes.)
>
> Did you get any kind of backtrace?  Was it actually a "TLB exception"
> (which has a specific meaning), or do you really just mean you're seeing
> random panics and that you think the TLB might be implicated?  What kind of
> TLB exception?  Load, store, modify?
>
> I haven't seen anything like what you describe, I don't think, but I'm
> also not sure what you're describing.  Hopefully we can track this down.
>
> Thanks,
> Juli.
>