IPMI hardware watchdogs Re: dell r420/r320 stable/9

[Attilio Rao]

On Fri, Jul 27, 2012 at 3:55 PM, Andrew Boyer <aboyer at averesystems.com> wrote:
>
> On Jul 27, 2012, at 10:42 AM, Attilio Rao wrote:
>
>> On Fri, Jul 27, 2012 at 3:33 PM, Andrew Boyer <aboyer at averesystems.com> wrote:
>>>
>>> On Jul 26, 2012, at 8:50 PM, Sean Bruno wrote:
>>>
>>>> For the time being I had to revert the following from my stable/9 tree.
>>>> Otherwise I would get a kernel panic on shutdown from ipmi(4).
>>>>
>>>> http://svnweb.freebsd.org/base?view=revision&revision=237839
>>>> http://svnweb.freebsd.org/base?view=revision&revision=221121
>>>>
>>>
>>> On a somewhat related note: We noticed recently that you can't pet or disable the IPMI hardware watchdog once SCHEDULER_STOPPED() is true.  This means it can fire unexpectedly while you're dumping core or rebooting, depending on how long the timeout was on the pet before the panic.  The ipmi driver will need to process the command differently if the scheduler is stopped.  I haven't had time to look at a fix yet.
>>
>> I recall I fixed that internally for SV, but the key here is that we
>> need to find an unified (or a default policy).
>> More specifically, do we want the watchdog also covers the kernel dump
>> part (because of possible deadlocks when dumping). If the answer is
>> yes, we likely need pat the watchdog from within the dumping cycle
>> itself. If the answer is no, then we can just disable it when entering
>> the panic path. But anyway, we need to identify a default policy that
>> makes sense first.
>>
>> Attilio
>>
>
> For our use case, we need the system to reset if the dump hangs.

This means we might likely go to control by hand the watchdog patting
in the panic path and more specifically I guess this reduces to
patting the watching from within the dumping cycle (there could be
other expensive points we can consider but nothing that pop off my
head right now). Maybe Ryan can share with us if SV can contribute the
code back about that specific part.

Attilio


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