> It's not up to the block driver, that's the thing. > > The _user_mode_ requests should just be stopped (you don't need to block > the queue - you just stop the processes). Then you wait for the queue to > drain. End of story. > > BUT YOU DON*T STOP THE DEVICE QUEUE. Because if you did, that would mean > that you couldn't save the state. My experience has been that relying on userland being stopped -> no more driver activity isn't going to work. Things like read-ahead or other niceties (not even talking about filesystems that scrub things in the background or kernel based web/nfs servers ;) will defeat that. > Note the "often". Quite often you can't. Things like cardbus controllers > will be set up by the POST to have all the right things, and you literally > can't re-generate it, because it depends on the motherboard. That's when > you save it. Yeah, well, video cards enter in that category... I have code that can bring back some radeon's from D3 cold for powermac provided I saved a whole bunch of registers beforehand. > (Or, even more commonly, you save it just because it's easier than > regenerating it) > > > Of course they do. Or we have a different notion of what you call > > "state" here... > > Yes. I think that's the main stumbling block. > > You consider "state" to be everything, whether needed or not. And I don't. > I consider "state" to be the things that "resume()" _requires_ to get > going again, which is actually a lot lot smaller. > > And exactly because I don't think it means "every bit", _my_ viewpoint > actually matches reality. It matches - for example - _exactly_ what we > already do wrt X. We (and here, the "we" is obviously mostly the X server) > need to save enough state to _recreate_ the state before suspend, but that > does not need that we need to save each bit. I agree that your viewpoint matches reality, it's just that I wouldn't have called it 'state' :) > It's actually also what a lot of drivers already do. Several drivers' > suspend routines don't actually need to save anythign at all, they just > turn the device off - exactly because they can recreate all the state > _without_ saving anything. Ben.
