On Thu, 2008-11-06 at 09:14 +0900, KAMEZAWA Hiroyuki wrote: > Ok, please consider "when memory hotplug happens." > > In general, it happens when > 1. memory is inserted to slot. > 2. the firmware notifes the system to enable already inserted memory. > > To trigger "1", you have to open cover of server/pc. Do you open pc while the system > starts hibernation ? for usual people, no. You're right, this won't happen very often. We're trying to close a theoretical hole that hasn't ever been observed in practice. But, we don't exactly leave races in code just because we haven't observed them. I think this is a classic race. If we don't close it now, then someone doing some really weirdo hotplug is going to run into it at some point. Who knows what tomorrow's hardware/firmware will do? > To trigger "2", the user have special console to tell firmware "enable this memory". > Such firmware console or users have to know "the system works well." And, more important, > when the system is suspended, the firmware can't do hotplug because the kernel is sleeping. > So, such firmware console or operator have to know the system status. > > Am I missing some ? Current linux can know PCI/USB hotplug while the > system is suspended ? * echo 'disk' > /sys/power/state * count number of pages to write to disk * turn all interrupts off * copy pages to disk * power down I think the race we're trying to close is the one between when we count pages and when we turn interrupts off. I assume that there is a reason that we don't do the *entire* hibernation process with interrupts off, probably because it would "lock" the system up for too long, and can even possibly fail. -- Dave _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
