Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2:hang in atomic copy)

From: Nigel Cunningham
Date: Thu Apr 26 2007 - 02:45:52 EST


On Wed, 2007-04-25 at 15:18 -0700, Linus Torvalds wrote:
> On Wed, 25 Apr 2007, Pavel Machek wrote:
> >
> > Not the same... but they are still related. "freeze" (for atomic
> > snapshot) is actually subset of "suspend"... freeze needs DMAs off and
> > saved state, and you need DMAs off and saved state for "suspend".
> Nobody in their right mind thinks that "disable DMA" and "suspend" are
> similar operations.
> > So it is actually correct to do "suspend" when you want "freeze"; it
> > is just slow. That's why they only differ in parameter these days.
> It is *not* correct to "suspend" when you want "freeze".
> I don't understand how you can even *claim* something like that.
> Here's a trivial example:
> - SCSI disk
> Tell me, what does "suspend" do, and what does "freeze" (snapshot) do?
> And name *one* thing that have in common.

Set/reset the scsi transaction id thingy? Hibernation didn't work with
SCSI for a long time precisely because that support was missing.

Don't get me wrong, I agree on the whole - Suspend2 worked fine on the
whole under 2.4 without a driver model. But they do have a bit in



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