On Monday, 3 of November 2008, Dave Hansen wrote: > On Mon, 2008-11-03 at 12:51 -0800, Andrew Morton wrote: > > On Wed, 29 Oct 2008 13:25:00 +0100 > > "Rafael J. Wysocki" <rjw@xxxxxxx> wrote: > > > On Wednesday, 29 of October 2008, Pavel Machek wrote: > > > > > > > > hibernation + memory hotplug was disabled in kconfig because we could > > > > not handle hibernation + sparse mem at some point. It seems to work > > > > now, so I guess we can enable it. > > > > > > OK, if "it seems to work now" means that it has been tested and confirmed to > > > work, no objection from me. > > > > yes, that was not a terribly confidence-inspiring commit message. > > > > 3947be1969a9ce455ec30f60ef51efb10e4323d1 said "For now, disable memory > > hotplug when swsusp is enabled. There's a lot of churn there right > > now. We'll fix it up properly once it calms down." which is also > > rather rubbery. > > > > Cough up, guys: what was the issue with memory hotplug and swsusp, and > > is it indeed now fixed? > > I suck. That commit message was horrid and I'm racking my brain now to > remember what I meant. Don't end up like me, kids. > > I've attached the message that I sent to the swsusp folks. I never got > a reply from that as far as I can tell. > > http://sourceforge.net/mailarchive/forum.php?thread_name=1118682535.22631.22.camel%40localhost&forum_name=lhms-devel > > As I look at it now, it hasn't improved much since 2005. Take a look at > kernel/power/snapshot.c::copy_data_pages(). It still assumes that the > list of zones that a system has is static. Memory hotplug needs to be > excluded while that operation is going on. This operation is carried out on one CPU with interrupts disabled. Is that not enough? > page_is_saveable() checks for pfn_valid(). But, with memory hotplug, > things can become invalid at any time since no references are held or > taken on the page. Or, a page that *was* invalid may become valid and > get missed. Can that really happen given the conditions above? > The "missing a page" thing is probably correctable via the > zone_span_seqbegin() locks. The "page becoming invalid" thing is > probably mostly fixable by acquiring a reference to the page itself. > I'd need to look how the locking on the hot remove side is working these > days to be much more constructive than that. Well, I don't think any locking is necessary for the image creation. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
