panic on one cpu leaves others running...

[Peter Jeremy]

On Thu, Apr 08, 2004 at 03:25:08AM -0600, Scott Long wrote:
>Peter Jeremy wrote:
>>On Thu, Apr 08, 2004 at 12:13:39AM -0400, Robert Watson wrote:
>>
>>>Funky, eh?  I thought we used to have code to ipi the other cpu's and halt
>>>them until the cpu in ddb was out agian.  I guess I mis-remember, or that
>>>code is broken...
>>
>>
>>Look on it as a feature - most other Unices can't survive a panic.
>>Being able to continue running in a degraded mode until a suitable
>>maintenance window is available would be a real selling point in
>>HA applications.  Even being able to shutdown cleanly would be
>>better than coming to a screaming halt.  :-) (sort of).
>
>Not sure if you're joking or not here.

I was joking about the FreeBSD behaviour (hence the smiley) but serious
about the (potential) benefits of being able to degrade rather than die.

>  A panic usually means that
>something unrecoverable happened, and that continuing on is not safe.

I realise that.  Hence actually being able to continue after a panic
would be extremely difficult to do safely.  (Probably not possible in
general, though it might be in some special cases).

Peter