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SubjectRe: [Devel] [RFC PATCH 0/4] Container Freezer: Reuse Suspend Freezer
Quoting Paul Menage (menage@google.com):
> On Thu, Apr 3, 2008 at 2:03 PM, <matthltc@us.ibm.com> wrote:
> >
> > * "freezer.kill"
> >
> > writing <n> will send signal number <n> to all tasks
> >
>
> My first thought (not having looked at the code yet) is that sending a
> signal doesn't really have anything to do with freezing, so it
> shouldn't be in the same subsystem. Maybe a separate subsystem called
> "signal"?
>
> And more than that, it's not something that requires any particular
> per-process state, so there's no reason that the subsystem that
> provides the "kill" functionality shouldn't be able to be mounted in
> multiple hierarchies.
>
> How about if I added support for stateless subsystems, that could
> potentially be mounted in multiple hierarchies at once? They wouldn't
> need an entry in the css set, since they have no state.
>
> > * Usage :
> >
> > # mkdir /containers/freezer
> > # mount -t container -ofreezer freezer /containers/freezer
> > # mkdir /containers/freezer/0
> > # echo $some_pid > /containers/freezer/0/tasks
> >
> > to get status of the freezer subsystem :
> >
> > # cat /containers/freezer/0/freezer.freeze
> > RUNNING
> >
> > to freeze all tasks in the container :
> >
> > # echo 1 > /containers/freezer/0/freezer.freeze
> > # cat /containers/freezer/0/freezer.freeze
> > FREEZING
> > # cat /containers/freezer/0/freezer.freeze
> > FROZEN
>
> Could we separate this out into two files? One called "freeze" that's
> a 0/1 for whether we're intending to freeze the subsystem, and one
> called "frozen" that indicates whether it is frozen? And maybe a
> "state" file to report the RUNNING/FREEZING/FROZEN distinction in a
> human-readable way?

One thing Oren had mentioned for checkpoint/restart was having more
states - i.e. restoring, checkpointing... So then (assuming we used
this subsys for that) we'd have more than the two files. Which is
probably fine, just wanted to point that out.

-serge


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