Re: [PATCH] Avoid endless loop for vcpu migration

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

On 03/15/11 09:50, Keir Fraser wrote:
> On 15/03/2011 08:46, "Juergen Gross"<juergen.gross@ts.fujitsu.com>  wrote:
>
>>> It's not critical, and not affecting correctness. But with updating
>>> idle_bias on the first invocation you're (on the right hardware)
>>> basically guaranteeing the second invocation to return a
>>> different CPU. That way, your loop will be run minimally three
>>> times on such systems. I already find it odd to require two
>>> iterations when previously this was a strait code path.
>>
>> This was wrong. It was always required to hold the schedule lock of the
>> picked cpu as well, otherwise a race with cpu hotplug would be possible.
>
> What would that race be? CPU offlining is done in stop_machine context.

Ahh, okay.


Juergen

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