linux-kernel - Re: [PATCH 1/2] cpufreq: Allow light-weight tear down on CPU offline operation

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] [day] [month] [year] [list]

Message-ID: <CAJZ5v0jKFaF5JRuwzR=d5Zc9p86m0eBDSmC-+d3LSKgyWuUpYg@mail.gmail.com>
Date:   Mon, 11 Feb 2019 11:56:37 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] cpufreq: Allow light-weight tear down on CPU offline operation

On Mon, Feb 11, 2019 at 11:51 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Mon, Feb 11, 2019 at 9:41 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> >
> > The cpufreq core doesn't remove the cpufreq policy anymore on CPU
> > offline operation, rather that happens when the CPU device gets
> > unregistered from the kernel. This allows faster recovery when the CPU
> > comes back online. This is also very useful during system wide
> > suspend/resume where we offline all non-boot CPUs during suspend and
> > then bring them back on resume.
> >
> > This commit takes the same idea a step ahead to allow drivers to do
> > light weight tear-down during CPU offline operation.
> >
> > A new callback is introduced, light_weight_exit(), which gets called
> > when all the CPUs of a policy are removed/offlined and the existing
> > exit() callback gets called when the policy gets freed.
> >
> > Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> > ---

[cut]

> > diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> > index 9db074ecbbd7..36ce31516041 100644
> > --- a/include/linux/cpufreq.h
> > +++ b/include/linux/cpufreq.h
> > @@ -325,6 +325,7 @@ struct cpufreq_driver {
> >         /* optional */
> >         int             (*bios_limit)(int cpu, unsigned int *limit);
> >
> > +       int             (*light_weight_exit)(struct cpufreq_policy *policy);
>
> Can you call it "offline"?
>
> >         int             (*exit)(struct cpufreq_policy *policy);
> >         void            (*stop_cpu)(struct cpufreq_policy *policy);
> >         int             (*suspend)(struct cpufreq_policy *policy);
> > --

Also, I would prefer a corresponding "online" callback to be there too
for symmetry and I'd prefer the core to decide to call "online"
instead of "init" for the light-weight case instead of ->init() itself
having to figure out the context.