Messages in this thread | | | Date | Fri, 26 Aug 2016 11:19:53 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v5 1/3] cpu/hotplug: Allow suspend/resume CPU to be specified |
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On Fri, Aug 26, 2016 at 12:09:38PM +0200, Thomas Gleixner wrote: > On Fri, 26 Aug 2016, Will Deacon wrote: > > On Wed, Aug 17, 2016 at 01:50:25PM +0100, James Morse wrote: > > > disable_nonboot_cpus() assumes that the lowest numbered online CPU is > > > the boot CPU, and that this is the correct CPU to run any power > > > management code on. > > > > > > On x86 this is always correct, as CPU0 cannot (easily) by taken offline. > > > > > > On arm64 CPU0 can be taken offline. For hibernate/resume this means we > > > may hibernate on a CPU other than CPU0. If the system is rebooted with > > > kexec 'CPU0' will be assigned to a different physical CPU. This > > > complicates hibernate/resume as now we can't trust the CPU numbers. > > > Arch code can find the correct physical CPU, and ensure it is online > > > before resume from hibernate begins, but also needs to influence > > > disable_nonboot_cpus()s choice of CPU. > > > > > > Rename disable_nonboot_cpus() as freeze_secondary_cpus() and add an > > > argument indicating which CPU should be left standing. Follow the logic > > > in migrate_to_reboot_cpu() to use the lowest numbered online CPU if the > > > requested CPU is not online. > > > Add disable_nonboot_cpus() as an inline function that has the existing > > > behaviour. > > > > > > Signed-off-by: James Morse <james.morse@arm.com> > > > Cc: Rafael J. Wysocki <rjw@rjwysocki.net> > > > --- > > > An alternative is to provide two functions calling a common function, > > > but this would mean spilling the cpu_maps_update_begin() into these two. > > > > > > include/linux/cpu.h | 6 +++++- > > > kernel/cpu.c | 9 +++++---- > > > 2 files changed, 10 insertions(+), 5 deletions(-) > > > > Thomas, does this look ok to you? If so, would you prefer to merge this > > series via -tip, or have us take this one via the arm64 tree? > > You can take it via ARM64. It's not conflicting with the stuff I have in the > pipeline. > > Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Brill, thanks Thomas.
Will
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