Hi! > > Here's what you actually did say: > > --------- > > > > > To have DMAs stopped, you need to "freeze" the devices. > > > > No you don't. > > > > You need to stop the high-level _queues_, but that's something totally > > different from actually stopping the _devices_. > > Right. > > What you _do_ need to do, is stop the user-level actions. Well, user-level actions are stopped because of refrigerator. > Before you suspend, you need to make the machine quiescent, in other > words. The devices are still working, but you really really don't want to > do this while things are still _happening_. > > Now, with suspend-to-RAM, I suspect we could even avoid that until the > very last phase (ie the actual suspend code). But quite frankly, from a > pure debuggability standpoint, I do think we want to basically try to make > everything as quiet as humanly possible. Suspend-to-RAM theoretically does not need any kind of stopping, and on ppc (IIRC) no stopping is really done. For suspend-to-disk, both user actions (so that they do not write to disk after atomic copy is done) and DMA (so that atomic image is not corrupted) needs to be stopped. > So think about what we do now: We special-case X, and we special-case the > save-to-disk device, and we special-case the console printouts, and we > special-case a lot of other things, AND WE STILL GOT IT WRONG. Try > using Actually no, we are not special-casing the disk device. There was discussion about doing that, but it is not going to happen. X are special, because they are user-level hardware driver. If/when we meet more user-level hardware drivers, we'll have to invent something extensible. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
