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SubjectRe: [RFC][PATCH] avoid cpu hot remove of cpus which have special RT tasks.
On Fri, 16 Jun 2006 12:36:50 +0200
Andi Kleen <ak@suse.de> wrote:

> > Assume there are some multi-threaded tasks with SCHED_FIFO.
> > If they uses some kind of synchronization in user land and task is migrated to
> > other cpus, it will cause dead-lock.
>
> If its CPU fails much worse things than that will happen.
>
> One way might be to break affinity of all processes in the system on hot unplug
> - then your deadlock would be avoided - but it might be a bit radical.
>
Hmm, ok. I undestand your point.
In "cpu is broken, so we have to remove it" case, my patch is harmful.

But (unpredictable) forced migration will cause something bad to user regardless
of scheduling type.

Should we send signal (kill or stop) to tasks whose cpus_allowed only contains
removed cpu rather than simple migration ?
(if this was discussed in past, I'm sorry)


-Kame

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