Messages in this thread | | | Date | Thu, 26 Apr 2007 00:42:16 +0200 | From | Pavel Machek <> | Subject | Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy) |
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Hi!
> > 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". > > THEY HAVE ABSOLUTELY NOTHING IN COMMON! > > 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".
Example?
> 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?
Suspend syncs caches/spins down. Freeze does not do anything.
That's okay, I keep claiming "freeze" is subset of "suspend". Can you name device where that is not true?
Remember we do
suspend(PMSG_FREEZE) atomic snapshot resume() write snapshot.
So if we do spin the scsi disk down, nothing really bad happens, we'll just spin it up. (So scsi disk is not example I want. Spining down scsi disk on freeze is slow and stupid, but it is not incorrect).
Yes, If I'd knew what I know now, drivers would have suspend/freeze/thaw/resume methods. We probably still can do that change. Unfortunately, it needs driver authors to understand 4 hooks (not 2) and do the right thing. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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