Re: [PATCH 6/6] sched: disabled rt-bandwidth by default

Max Krasnyansky
2008-08-28T16:19:20Z

Andi Kleen wrote:
> On Thu, Aug 28, 2008 at 01:19:13PM +0200, Peter Zijlstra wrote:
>> On Thu, 2008-08-28 at 13:09 +0200, Andi Kleen wrote:
>>>> Even if the system has multiple CPUs, and even if just a single CPU is
>>>> fully utilized by an RT task, without the rt-limit the system will still
>>>> lock up in practice due to various other factors: workqueues and tasks
>>>> being 'stuck' on CPUs that host an RT hog.
>>> The load balancer will not notice that a particular CPU is busy
>>> with real time tasks?
>> Not currently, working on that though.
>
> I wonder if it would make sense to break affinities in extreme case?
> With that even the workqueues would work again.

Please lets not break affinity :).

I'm going to submit patches (soonish) that convert drivers/etc to use
cancel_work_sync()/flush_work() instead of flush_scheduled_work().
That takes care of the
"machine getting stuck because workqueue thread is starved"
case.

Max