Messages in this thread | | | Subject | Re: PATCH: Fix race in cpu_down (hotplug cpu) | From | Nick Piggin <> | Date | Mon, 19 Sep 2005 17:37:05 +1000 |
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On Mon, 2005-09-19 at 09:28 +0200, Ingo Molnar wrote: > * Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> > Oh really? I think yes, the latency should be taken care of because we > > want to be able to provide good latency even for !preempt kernels. If > > a solution can be found for acpi_processor_idle, that would be ideal. > > the ACPI idle code runs with irqs disabled anyway, so there's no issue > here. If something takes long there, we can do little about it. (but in > practice ACPI sleep latencies are pretty ok - the only latencies i found > in the past were due to need_resched bugs in the ACPI idle routine) >
Ah, in that case I agree: we have nothing to worry about by merging such a patch then.
> > IMO it always felt kind of hackish to run the idle threads with > > preempt on. > > Yes, idle threads can have preemption disabled. There's not any big > difference in terms of latencies, the execution paths are all very > short. >
Thanks for the confirmation Ingo. This is part of my "cleanup resched and cpu_idle" patch FYI. It should already be in -mm, but has some trivial EM64T bug in it that Andrew hits but I can't reproduce.
I'll dust it off and send it out, hopefully someone will be able to reproduce the problem!
-- SUSE Labs, Novell Inc.
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