[PATCH 3/5] PM / Hibernate: Allow architectures to specify the hibernate/resume CPU

Hi Rafael,

On 13/06/16 23:10, Rafael J. Wysocki wrote:

On Tuesday, June 14, 2016 12:05:28 AM Rafael J. Wysocki wrote:

quoted

On Thursday, June 02, 2016 03:10:55 PM James Morse wrote:

quoted

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@arm.com>
Cc: Rafael J. Wysocki <redacted>
Cc: Pavel Machek <redacted>
---
I would have preferred a macro, but there is no hibernate-relevant header
file that all arch's have. arm, arm64 and x86 have a suspend.h, but powerpc
doesn't.

What about include/linux/suspend.h?

There are arch_ things declared in there.

I mean, what about using something like

#ifndef arch_hibernation_disable_cpus
#define arch_hibernation_disable_cpus disable_nonboot_cpus
#endif

in there or in another header file?

This would work fine for an architecture that doesn't need to use
arch_hibernation_disable_cpus(), but which header file should we use for an
architecture that does?

As a macro it needs to be in an arch-specific header included before the #ifndef
above.

Of those:
include/linux/suspend.h only includes <asm/errno.h>
kernel/power/power.h doesn't include any 'asm' headers.
snapshot.c includes:

#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/io.h>

... but none of those are appropriate.


I initially added an include for <asm/suspend.h> to kernel/power/power.h, but it
broke powerpc, as there is no suspend.h there. I took this as a dead-end for the
macro approach, unless someone has a clever trick?!



Thanks,

James