linux-kernel - Re: [PATCH] x86: tsc: Rework time_cpufreq

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Message-ID: <CAJZ5v0hyu5WcL2F-Vz8mGOjwGwEGzpeW-Agh+Gi1W6pomaZqyg@mail.gmail.com>
Date:   Thu, 18 Apr 2019 21:36:15 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        x86 Maintainers <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: tsc: Rework time_cpufreq_notifier()

On Thu, Apr 18, 2019 at 8:40 PM Borislav Petkov <bp@...en8.de> wrote:
>
> On Thu, Apr 18, 2019 at 04:11:37PM +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > There are problems with running time_cpufreq_notifier() on SMP
> > systems.
>
> Just a stupid question: that must be some old rust you're fixing because
> we set X86_FEATURE_CONSTANT_TSC on almost anything that is x86 nowadays
> and if that is set, we don't reg that notifier call...

That's totally correct.

It's never really worked AFAICS and even so, then by accident.