Messages in this thread | | | Date | Fri, 10 Feb 2012 16:51:17 -0500 (EST) | From | Alan Stern <> | Subject | Re: [PATCH 0/4] CPU hotplug, cpusets: Fix CPU online handling related to cpusets |
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On Fri, 10 Feb 2012, Peter Zijlstra wrote:
> Now the whole problem here seems to be that suspend uses cpu-hotplug to > reduce the machine to UP -- I've no clue why it does that but I can > imagine its because the BIOS calls only work on CPU0 and/or the resume > only wakes CPU0 so you have to bootstrap the SMP thing again.. > > Some suspend person wanna clarify? Rafael?
If I understand correctly, ACPI requires that only CPU0 be running when the system is suspended (i.e., your guess is right). Of course, this doesn't apply to non-ACPI systems, but it's easiest to do the same thing everywhere.
> Anyway, the whole suspend case is magic anyway since all tasks will have > been frozen, so we could simply leave all of cpuset alone and ignore the > hotplug notifier on CPU_TASKS_FROZEN callbacks, hmm?
I don't see why not. Presumably no CPUs will be added or removed while the system is asleep.
> Do we unfreeze after we bring up the machine again?
Yes.
Alan Stern
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