On Wednesday, 30 May 2007 22:44, Rafael J. Wysocki wrote: > Hi, > > On Wednesday, 30 May 2007 17:37, Pavel Machek wrote: > > Hi! > > > > > +Suspend notifiers > > > + (C) 2007 Rafael J. Wysocki <[EMAIL PROTECTED]>, GPL > > > + > > > +There are some operations that device drivers may want to carry out in > > > their > > > +.suspend() routines, but shouldn't, because they can cause the > > > hibernation or > > > +suspend to fail. For example, a driver may want to allocate a > > > substantial amount > > > +of memory (like 50 MB) in .suspend(), but that shouldn't be done after > > > the > > > +swsusp's memory shrinker has run. > > > + > > > +Also, there may be some operations, that subsystems want to carry out > > > before a > > > +hibernation/suspend or after a restore/resume, requiring the system to > > > be fully > > > +functional, so the drivers' .suspend() and .resume() routines are not > > > suitable > > > +for this purpose. For example, device drivers may want to upload > > > firmware to > > > +their devices after a restore from a hibernation image, but they cannot > > > do it by > > > +calling request_firmware() from their .resume() routines (user land > > > processes > > > +are frozen at this point). The solution may be to load the firmware into > > > +memory before processes are frozen and upload it from there in the > > > .resume() > > > +routine. Of course, a hibernation notifier may be used for this purpose. > > > + > > > +The subsystems that have such needs can register suspend notifiers that > > > will be > > > +called upon the following events by the suspend core: > > > + > > > +PM_PRE_FREEZE The system is going to hibernate or suspend, > > > tasks will > > > + be frozen immediately > > > > Hmm, looks like bad idea if we are going to remove freezer from > > suspend...? > > We need PM_PRE_FREEZE anyway and it's a different question whether or not > it'll be used for suspend (STR) too. > > The timing is not the best one, but so far the freezer is in the suspend code > path and I need to take this into account. > > > > +PM_POST_THAW Tasks have just been thawed after a resume or > > > restore > > > + from a hibernation image > > > + > > > +PM_HIBERNATION_PREPARE The system is preparing for hibernation. Tasks > > > have > > > + been frozen, memory is going to be freed and devices > > > + are going to be suspended. > > > > Is not PRE_FREEZE enough? We can allocate memory for drivers there, > > too... > > Well, there is a reason for not doing this. Namely, if the memory if freed on > PM_POST_HIBERNATION after the image has been created, we can use it for saving > the image (and speed up the saving). > > Besides, if the freezer is dropped from the suspend code, the notifiers will > be > useful to it anyway IMO, and PRE_FREEZE won't make sense in that case. > > I think the rule should be: If you need to do something _before_ tasks are > frozen, do it in PM_PRE_FREEZE, but if you can do that after the tasks have > been frozen, do it on PM_HIBERNATION_PREPARE (or PM_SUSPEND_PREPARE in the > suspend case).
OTOH, having considered it for a while, I think that for now I can add just PM_PRE_FREEZE and PM_POST_THAW, as I don't have any user for the other ones. The other events may be added in the future if need be (along with some users). I'll post revised patches in a new thread. Greetings, Rafael - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
