Messages in this thread | | | Subject | Re: [linux-pm] [PATCH] hibernation should work ok with memory hotplug | From | Dave Hansen <> | Date | Wed, 05 Nov 2008 16:28:01 -0800 |
| |
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
| |