linux-kernel - Re: [RFC v3 1/5] sched/core: add capacity constraints to CPU controller

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAEi0qNkAK_3a_2x9BgvyEC+bFvckGFoQX1fjFba6boC1ws_R5w@mail.gmail.com>
Date:   Mon, 13 Mar 2017 03:46:13 -0700
From:   "Joel Fernandes (Google)" <joel.opensrc@...il.com>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>, Joel Fernandes <joelaf@...gle.com>
Subject: Re: [RFC v3 1/5] sched/core: add capacity constraints to CPU controller

On Tue, Feb 28, 2017 at 6:38 AM, Patrick Bellasi
<patrick.bellasi@....com> wrote:
> The CPU CGroup controller allows to assign a specified (maximum)
> bandwidth to tasks within a group, however it does not enforce any
> constraint on how such bandwidth can be consumed.
> With the integration of schedutil, the scheduler has now the proper
> information about a task to select  the most suitable frequency to
> satisfy tasks needs.
[..]

> +static u64 cpu_capacity_min_read_u64(struct cgroup_subsys_state *css,
> +                                    struct cftype *cft)
> +{
> +       struct task_group *tg;
> +       u64 min_capacity;
> +
> +       rcu_read_lock();
> +       tg = css_tg(css);
> +       min_capacity = tg->cap_clamp[CAP_CLAMP_MIN];

Shouldn't the cap_clamp be accessed with READ_ONCE (and WRITE_ONCE in
the write path) to avoid load-tearing?

Thanks,
Joel