Re: Hibernation considerations

david
2007-07-15T23:58:54Z

On Sun, 15 Jul 2007, Alan Stern wrote:

> On Sun, 15 Jul 2007, Al Boldi wrote:
>
>> Alan Stern wrote:
>>> On Sun, 15 Jul 2007, Al Boldi wrote:
>
>>>> This should be the responsibility of the kexec'd hibernating kernel.
>>>> Note though in (6), the normal kernel takes care of preparing devices,
>>>> then the hibernating kernel dumps the image and either calls S4 or S3.
>>>> On resume from S3 it can immediately switch over to the normal kernel,
>>>> and from S4 the known bootup would occur.
>>>
>>> Is it really that simple? Somehow I doubt it. In order for some
>>> devices to remain available for the kexec'd kernel to use, they cannot
>>> be suspended at the ACPI level. So the kexec'd kernel will have to
>>> handle the ACPI requirements for those devices. Likewise, it would
>>> have to handle the ACPI interactions which need to be done after all
>>> devices are prepared for the transition to S3 or S4.
>>
>> Ok, after applying the latest kexec patches, I was able to use the kexec'd
>> kernel to suspend to ram and resume to the normal kernel, while working
>> under a full-blown X session. It went without a hitch. All that is needed
>> now are the dump/restore hibernation-image routines.
>
> That's exactly my point. While doing suspend-to-RAM from a kexec'd
> kernel may be simple, saving the hibernation image will add
> complications.

suspend-to-RAM should not involve kexec, the only reason for doing the
kexec to to get a seperate userspace to use for suspend-to-disk operations
instead of trying to partially freeze the sustem and keep useing it.

David Lang