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

Rafael J. Wysocki rjw at sisk.pl
Tue Oct 13 13:35:55 PDT 2009


On Tuesday 13 October 2009, Thomas Hellstrom wrote:
> 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.

Could you please prepare a patch fixing that comment?

Rafael


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