[PATCH v2 4/6] PM / Hibernate: Allow architectures to specify the hibernate/resume CPU

Rafael J. Wysocki rjw at rjwysocki.net
Tue Jun 28 17:03:51 PDT 2016

On Tuesday, June 28, 2016 03:51:39 PM James Morse wrote:
> Hi Rafael,
> On 15/06/16 22:10, Rafael J. Wysocki wrote:
> > On Wed, Jun 15, 2016 at 7:35 PM, James Morse <james.morse at arm.com> wrote:
> >> On arm64 the cpu with logical id 0 is assumed to be the boot CPU. If a
> >> user hotplugs this CPU out, then uses kexec to boot a new kernel, the new
> >> kernel will assign logical id 0 to a different physical CPU.
> >> This breaks hibernate as hibernate and resume will be attempted on different
> >> CPUs.
> >>
> >> Define a weak symbol arch_hibernation_disable_cpus(), which defaults to
> >> calling disable_nonboot_cpus). Architectures that allow CPU 0 to be
> >> hotplugged can use this to control which CPU is used for hibernate/resume.
> >>
> >> Signed-off-by: James Morse <james.morse at arm.com>
> >> Cc: Rafael J. Wysocki <rjw at rjwysocki.net>
> >> Cc: Pavel Machek <pavel at ucw.cz>
> >> ---
> >> If this approach is acceptable, this patch should go with 4&5 via the arm64
> >> tree.
> > 
> > I'm not entirely happy with this, but if you absolutely need it and if
> > you can't think about any cleaner way to achieve the goal, feel free
> > to add my ACK to this patch if necessary.
> I would prefer you to be happy with it.
> On the weak symbol: After staring at this some more I've made the macro approach
> work, so the weak symbol can go. (a new version of this series should arrive soon)
> On the arch-specific odour coming from this, it may also be useful for Chen Yu's
> 'Use hlt instead of mwait when resuming from hibernation' series[0]. (I don't
> understand the x86 specifics)

Yes, it looks like both x86 and ARM64 want/need to do something special around
disabling/enabling nonboot CPUs during hibernation/restore.

Let me comment on the new submission, though.


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