On Thu, 2008-04-03 at 16:49 -0700, Paul Menage wrote: > On Thu, Apr 3, 2008 at 2:03 PM, <matthltc@xxxxxxxxxx> 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. This seems reasonable to me. A quick look at Cedric's patches suggests there's no need for such cgroup subsystems to be tied together -- the signalling is all done internally to the freeze_task(), refrigerator(), and thaw_process() functions from what I recall. > > * Usage : > > > > # mkdir /containers/freezer > > # mount -t container -ofreezer freezer /containers/freezer > > # mkdir /containers/freezer/0 > > # echo $some_pid > /containers/freezer/0/tasks > > > > to get status of the freezer subsystem : > > > > # cat /containers/freezer/0/freezer.freeze > > RUNNING > > > > to freeze all tasks in the container : > > > > # echo 1 > /containers/freezer/0/freezer.freeze > > # cat /containers/freezer/0/freezer.freeze > > FREEZING > > # cat /containers/freezer/0/freezer.freeze > > FROZEN > > Could we separate this out into two files? One called "freeze" that's > a 0/1 for whether we're intending to freeze the subsystem, and one > called "frozen" that indicates whether it is frozen? And maybe a > "state" file to report the RUNNING/FREEZING/FROZEN distinction in a > human-readable way? 3 files seems like overkill. I think making them human-readable is good and can be done with two files: "state" (read-only) and "state-next" (read/write). Transitions between RUNNING and FROZEN are obvious when state-next != state. I think the advantages are it's pretty human-readable, you don't need separate strings and files for the transitions, it's clear what's about to happen (IMHO), and it only requires 2 files. Some examples: To initiate freezing: # cat /containers/freezer/0/freezer.state RUNNING # echo "FROZEN" > /containers/freezer/0/freezer.state-next # cat /containers/freezer/0/freezer.state RUNNING # cat /containers/freezer/0/freezer.state-next FROZEN # sleep N # cat /containers/freezer/0/freezer.state FROZEN # cat /containers/freezer/0/freezer.state-next FROZEN So to cancel freezing you might see something like: # cat /containers/freezer/0/freezer.state RUNNING # cat /containers/freezer/0/freezer.state-next FROZEN # echo "RUNNING" > /containers/freezer/0/freezer.state-next # cat /containers/freezer/0/freezer.state-next RUNNING If you wanted to know if a group was transitioning: # diff /containers/freezer/0/freezer.state /containers/freezer/0/freezer.state-next Or: # current=`cat /containers/freezer/0/freezer.state` # next=`cat /containers/freezer/0/freezer.state-next` # [ "$current" != "$next" ] && echo "Transitioning" # [ "$current" == "RUNNING" -a "$next" == "FROZEN" ] && echo "Freezing" # [ "$current" == "FROZEN" -a "$next" == "RUNNING" ] && echo "Thawing" # [ "$current" == "RUNNING" -a "$next" == "RUNNING" ] && echo "No-op" # [ "$current" == "FROZEN" -a "$next" == "FROZEN" ] && echo "No-op" etc. Cheers, -Matt Helsley _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
