[RFC PATCH v5] ARM hibernation / suspend-to-disk (fwd)

[frank.hofmann@tomtom.com (Frank Hofmann)]

On Wed, 29 Jun 2011, Matthieu CASTET wrote:

> Frank Hofmann a ?crit :
>> On Mon, 13 Jun 2011, Russell King - ARM Linux wrote:
>>
>> Hi Russell,
>>
>>
>> this change is perfect; with this, the hibernation support code turns into
>> the attached.
>>
>> That's both better and simpler to perform a full suspend/resume cycle (via
>> resetting in the cpu_suspend "finisher") after the snapshot image has been
>> created, instead of shoehorning a return into this.
>>
>> FrankH.
>
>
>>
>> +
>> +u8 __swsusp_resume_stk[PAGE_SIZE/2] __nosavedata;
> It look like dangerous : there is no alignment constraint, but the stack should
> be aligned on a 8 Bytes.

Uh - sorry. I used to have both the __nosavedata and 
__attribute__((__aligned__(PAGE_SIZE/2))) attributes there. That must've 
gone lost at one point.


It's an artifact of the build that things turn out ok by default; the 
__nosavedata forces a separate section (page), and arch/arm is linked 
before kernel/power (the other user of __nosavedata), hence this block, 
due to the way the kernel build works, ends up just fine.

But as you say, not by intent / declaration.


Have you seen Will Deacon's suggested kexec changes ? That keeps a "reset 
stack" page around, _elsewhere_, and I've been considering using that. In 
the end, all swsusp_arch_resume() really requires is a stack page that's 
guaranteed to be outside the target kernel data, thereby left alone by the 
restore. __nosavedata is merely one way.

>
>
> Matthieu
>
Thanks,

FrankH.