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

From: Paul Menage
Date: Tue Jun 21 2011 - 13:37:31 EST

On Sun, Jun 19, 2011 at 4:51 PM, Frederic Weisbecker <fweisbec@xxxxxxxxx> 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.

> +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.

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