Re: [RFC PATCH 4/4] cgroups: Add an rlimit subsystem

[Frederic Weisbecker <fweisbec@gmail.com>]

On Tue, Jun 21, 2011 at 10:37:03AM -0700, Paul Menage wrote:
> On Sun, Jun 19, 2011 at 4:51 PM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
> > +static void rlim_cgroup_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
> > +                     struct cgroup *old_cgrp, struct task_struct *task)
> > +{
> > +       rlim_remove_proc(old_cgrp);
> > +}
> 
> Since this is used for both the exit callback and the attach callback,
> it should have a more generic name.

Right.
 
> > +static int rlim_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
> > +{
> > +       struct rlim *rlim = cgroup_rlim(cgrp);
> > +       struct res_counter *limit_fail_at;
> > +
> > +       return res_counter_charge(&rlim->proc_counter, 1, &limit_fail_at);
> > +}
> 
> Can't this fail spuriously in the presence of hierarchies?
> 
> E.g. if cgroup A has children, and A is at its limit, then moving
> tasks around between A and its children, or between different children
> of A, seems like it would fail due to the temporary double counting.

Good point. Probably I should first uncharge the old cgroup and its parents.