Quoting Oren Laadan (orenl@xxxxxxxxxxxxxxx): > > > Serge E. Hallyn wrote: > >Quoting Oren Laadan (orenl@xxxxxxxxxxxxxxx): > >> > >>Sukadev Bhattiprolu wrote: > >>>The help message for --freezer=CGROUP option says: > >>> > >>> freeze tasks in freezer group CGROUP on success > >>> > >>>and if this option specifies an existing cgroup, then (and only > >>>then) is the RESTART_FROZEN flag to sys_restart() set. > >>> > >>>Does the --freezer option have to specify an existing cgroup ? > >>As it is now - yes; > >> > >>In theory I would like use -F (--freezer) without an argument, > >>to use RESTART_FROZEN without explicitly adding tasks to a > >>target cgroup. > >> > >>The trick is that we need to put all the restarted tasks in the > >>traget cgroup. The coordinator must remain outside that cgroup, > >>or it will be frozen as well when restart succeeds. > >> > >>This means that restarted tasks (at least the root task) have > >>to be explicitly added to the cgroup - which is why I require > >>that the cgroup name be passed. > >> > >>This could be avoided if we could add 'restart' to a cgruop and > >>then after spawning the entire tree, we could remove 'restart' > >>from that cgroup. I don't think this is possible ? > > > >Why not? You can certainly move to freezer:/restart.XYZ, spawn > >tasks, then move back to freezer:/. And since the tasks should > >hang in sys_restart() until the coordinator calls sys_restart() > >itself, there should be no race issues. Do you mean that something > >else won't work? > > No, I just wasn't thinking right... > > But even in this case, we need some more wisdom: we need to know > where the coordinator starts (in which cgroup) before moving it > to a new cgroup, so we can put it back in the original cgroup. Is > there an API for that ? Yup - cat /proc/self/cgroup, or I suspect the libcgroup API gives you a friendlier interface (so you don't have to parse the file yourself). > >>>Is there a way to specify that the restarted application belong > >>>to a new (yet-to-be created) cgroup AND to leave the application > >>>FROZEN after restart ? Or would we need a new command line option > >>>and field in 'struct app_restart_args' to specify this ? > >>This is exactly what --freezer does. Well, alsmot - except for > >>"yet-to-be created". Do you want 'restart' to create the cgroup > >>if it doesn't exist ? > > > >I thought that was what Suka was asking for. > > If he wants to add it to the 'restart' utility, then sure, with > a proper argument. > > I'm not sure that creating a control group fits into the mandate > of a library call/api. Instead, I'd expect the caller to arrange > for a cgroup to be created. > > Oren. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
