Re: [PATCH] cpupools: retry cpupool-destroy if domain in cpupool is dying

[Juergen Gross <juergen.gross@ts.fujitsu.com>]

On 14.05.2014 15:13, Jan Beulich wrote:
>>>> On 14.05.14 at 15:05, <juergen.gross@ts.fujitsu.com> wrote:
>> On 14.05.2014 14:28, Jan Beulich wrote:
>>>>>> On 14.05.14 at 12:35, <juergen.gross@ts.fujitsu.com> wrote:
>>>> sched_destroy_vcpu() and sched_destroy_domain() have to happen before
>>>> cpupool_rm_domain(). This could be avoided if the domain would be moved to
>>>> cpupool0 in domain_destroy().
>>>>
>>>> Hmm, doesn't sound too bad. This would be just symmetrical to domain
>>>> creation. What do you think?
>>>
>>> I'm always in favor of symmetry, where possible and suitable. So
>>> unless George objects or sees problems with this, why don't you
>>> give this a try?
>>
>> One problem arises: sched_move_domain() can fail. Is there a preferred way to
>> handle this situation in domain_destroy() ? I could try to defer destroying
>> the domain until sched_move_domain() succeeds, but using a busy loop doing this
>> seems contra-productive and a timer based solution requires a timer
>> structure.
>>
>> I could reuse the domain watchdog_timer entries if I move
>> watchdog_domain_destroy() to domain_destroy() (which seems to be not critical).
>>
>> OTOH this seems a little bit hacky...
>
> Indeed it does. Yet - does that move have to happen in
> domain_destroy()? I.e. can't it be pulled even further ahead into
> domain_kill()? That one already is preemptable/resumable (via
> guarantees we expect from the tools side iirc), since
> domain_relinquish_resources() may take quite long a time. Of course
> that'll work only if no failure condition in sched_move_domain() is
> permanent.

Aah, excellent!

Now the patch seems to be very simple! I'll do some tests to verify it isn't
breaking something.


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
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