[lkml]   [2012]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 0/4] CPU hotplug, cpusets: Fix CPU online handling related to cpusets
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?


Alan Stern

 \ /
  Last update: 2012-02-10 22:53    [W:0.062 / U:12.172 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site