Re: fixing usb suspend/resuming

[Nigel Cunningham <ncunningham@linuxmail.org>]

Hi.

On Fri, 2004-07-30 at 08:39, Pavel Machek wrote:
> > I'm assuming (and believe I have achieved) that the only process doing
> > anything significant is suspend, in which case the image isn't going to
> > get damaged.
> 
> Well, only suspend is doing something significant, but driver might
> take arbitrary time to do its DMA... Like
> 
> Freeing some memory... [write starts]
> Suspending devices... [but you did not suspend disk!]
> Atomic copy... [oops, that disk was *still* doing DMA]

Sorry. Should have mentioned that one of my freezer changes includes
running sync between freezing userspace and freezing the kernel threads,
that I double check there are no dirty buffers afterwards and wait on
the completion of all suspend's I/O between after each part of the image
is written/read (have to be paranoid because of the way I reuse LRU
pages).

> > > need something like
> > > 
> > > suspend_fast_ill_resume_you_soon().
> > 
> > Don't understand what you're saying here, sorry.
> 
> Well, I believe we really need to suspend *all* devices. We just do
> not need to spin the disks down and make screens blank; we still need
> drivers to be stopped so that no activity happens during atomic copy.

Ah with you now. The typo got me (_ill_).