Re: [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm2-V0.7.1

From: Ingo Molnar
Date: Mon Nov 08 2004 - 10:56:36 EST

* Esben Nielsen <simlo@xxxxxxxxxx> wrote:

> On a SMP system you don't have these nice properties. You always have
> to take into account that N processes are really running at the same
> time.

not necessarily. In theory we could introduce the notion of
"hyper-high-priority tasks" (e.g. SCHED_HYPER_FIFO), which tasks not
only get preempted on one CPU immediately, but cause the kernel to stop
and loop on all other CPUs as well. That way the same 'nice' properties
of UP kernels get carried over to the SMP system as well, at the cost of
serializing all execution while the hyper-high-prio task is running.
Once the task stops running, the other CPUs can continue as well.

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