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

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Message-ID: <BANLkTin_MA+Yc7=q=cK5s2CbCfu_xmqTAQ@mail.gmail.com>
Date:	Tue, 21 Jun 2011 10:37:03 -0700
From:	Paul Menage <menage@...gle.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Li Zefan <lizf@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 4/4] cgroups: Add an rlimit subsystem

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

> +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.

Paul
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