* Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote: > On Thu, 2008-10-09 at 15:17 +0200, Ingo Molnar wrote: > > * Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote > > > On Thu, 2008-10-09 at 14:46 +0200, Ingo Molnar wrote: > > > > i'm wondering about the following productization aspect: it would be > > > > very useful to applications and users if they knew whether it is safe to > > > > checkpoint a given app. I.e. whether that app has any state that cannot > > > > be stored/restored yet. > > > > > > Absolutely! > > > > > > My first inclination was to do this at checkpoint time: detect and > > > tell users why an app or container can't actually be checkpointed. > > > But, if I get you right, you're talking about something that happens > > > more during the runtime of the app than during the checkpoint. This > > > sounds like a wonderful approach to me, and much better than what I > > > was thinking of. > > > > > > What kind of mechanism do you have in mind? > > > > > > int sys_remap_file_pages(...) > > > { > > > ... > > > oh_crap_we_dont_support_this_yet(current); > > > } > > > > > > Then the oh_crap..() function sets a task flag or something? > > > > yeah, something like that. A key aspect of it is that is has to be very > > low-key on the source code level - we dont want to sprinkle the kernel > > with anything ugly. Perhaps something pretty explicit: > > > > current->flags |= PF_NOCR; > > Am I miscounting, or are we out of these suckers on 32-bit platforms? We've still got a few holes: you can pick 0x00000020, 0x00000080, 0x00004000, 0x08000000. > > as we do the same thing today for certain facilities: > > > > current->flags |= PF_NOFREEZE; > > > > you probably want to hide it behind: > > > > set_current_nocr(); > > Yeah, that all looks reasonable. Letting this be a dynamic thing > where you can move back and forth between the two states would make a > lot of sense too. But, for now, I guess it can be a one-way trip. there might be races as well, especially with proxy state - and current->flags updates are not serialized. So maybe it should be a completely separate flag after all? Stick it into the end of task_struct perhaps. Ingo _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers