[linux-pm] Hibernation out-of-memory problem.

[Thomas Hellstrom]

Rafael J. Wysocki wrote:
> On Saturday 10 October 2009, Thomas Hellstrom wrote:
>   
>> Hi!
>>
>> I'm trying to port a graphics DRM device driver over to the new power 
>> management hooks in
>>
>> struct dev_pm_ops.
>>
>> During the "prepare" call, Video RAM contents may be copied either to 
>> shmem objects or pages allocated using alloc_page().
>> Unfortunately, this seems to lead to the hibernation process running out 
>> of free pages.
>>
>> One possible cause is that the function swsusp_shrink_memory() is called 
>> before the prepare() call, and therefore doesn't free up enough memory.
>>
>> What would be the correct way around this? Should swsusp_shrink_memory() 
>> be moved to after prepare(), or is it possible to get some kind of 
>> notification after user space processes is stopped, but before 
>> swsusp_shrink_memory()?
>>     
>
> There are suspend/hibernation notifiers that can be used for this purpose.
>
> Thanks,
> Rafael
>   
Thanks, Rafael. I tried that and it works fine.

Now, it may be that others will hit this problem as well, as the 
documentation in <linux/pm.h> states that it is safe to make
GFP_KERNEL allocations from within a prepare() callback. Such 
allocations executed in the prepare() preceeding a freeze() will 
probably make the amount of previously freed memory insufficient.

Thanks,

Thomas