[lkml]   [2010]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC][PATCH] PM: Force GFP_NOIO during suspend/resume (was: Re: [linux-pm] Memory allocations in .suspend became very unreliable)

> > If suspend need lots memory, we need to make free memory before starting IO
> > suspending, I think.
> Suspend as such doesn't need a lot of memory, except for some drivers doing
> things they shouldn't do.
> However, there are a few problems that need to be addressed in general.
> First, we can't really guarantee that there's a lot of free memory available
> during suspend and some memory allocations are done indirectly, using
> GFP_KERNEL (for example, when new kernel threads are started). If one of
> these is done during suspend and it happens to cause the mm subsystem to
> start I/O on a suspended devices, the kernel will lock up.
> Second, there may be a memory allocation in progress when suspend is started
> that causes I/O to happen and races with the suspend process. If the latter
> wins the race, the I/O may be attempted on a suspended device and the kernel
> will lock up.

I think the race happen itself is bad. memory and I/O subsystem can't solve such race
elegantly. These doesn't know enough suspend state knowlege. I think the practical
solution is that higher level design prevent the race happen.

> My patch attempts to avoid these two problems as well as the problem with
> drivers using GFP_KERNEL allocations during suspend which I admit might be
> solved by reworking the drivers.

Agreed. In this case, only drivers change can solve the issue.

 \ /
  Last update: 2010-01-19 02:21    [W:0.084 / U:10.340 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site