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

[Attilio Rao]

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


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