On Wednesday, 5 of November 2008, KAMEZAWA Hiroyuki wrote: > On Tue, 04 Nov 2008 08:59:05 -0800 > Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote: > > > On Tue, 2008-11-04 at 17:34 +0100, Rafael J. Wysocki wrote: > > > Now, I need to do one more thing, which is to check how much memory has to be > > > freed before creating the image. For this purpose I need to lock memory > > > hotplug temporarily, count pages to free and unlock it. What interface should > > > I use for this purpose? > > > > > > [I'll also need to lock memory hotplug temporarily during resume.] > > > > We currently don't have any big switch to disable memory hotplug, like > > lock_memory_hotplug() or something. :) > > > > If you are simply scanning and counting pages, I think the best thing to > > use would be the zone_span_seq*() seqlock stuff. Do your count inside > > the seqlock's while loop. That covers detecting a zone changing while > > it is being scanned. > > > > The other case to detect is when a new zone gets added. These are > > really rare. Rare enough that we actually use a stop_machine() call in > > build_all_zonelists() to do it. All you would have to do is detect when > > one of these calls gets made. I think that's a good application for a > > new seq_lock. > > > > I've attached an utterly untested patch that should do the trick. > > Yasunori and KAME should probably take a look at it since the node > > addition code is theirs. > > > > Hmm ? I think there is no real requirement for doing hibernation while > memory is under hotplug. > > Assume following. > - memory hotplug can be triggerred by > 1. interrupt from system. > 2. "probe" interface in sysfs. > - ONLINE/OFFLINE is only trigerred by sysfs interface. > > I believe we can't block "1", but "1" cannot be raised while hibernation. > (If it happens, it's mistake of the firmware.) > > "probe" interface can be triggered from userland. Then it may be worth to be > blocked. How about to add device_pm_lock() to following place ? This is not necessary as long as we freeze the userland before hibernation. Still, this is one thing to remeber that the freezing is needed for. :-) 1. seems to be problematic, though, since we rely on zones remaining unchanged while we're counting memory pages to free before hibernation and this happens before the calling ->suspend() methods of device drivers. Of course we can count free pages in a different way, but that will be a substantial modification (I think). How's the firmware supposed to be notified that hibernation is going to happen? Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
