linux-kernel - Re: [PATCH v1 0/5] cpuidle: Take possible negative "sleep length" values into account

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Message-ID: <CAJZ5v0iMpOtNdnAvx3fRP-wNz4OBG9ZyDXVG0KnHDdGz2U4ipA@mail.gmail.com>
Date:   Wed, 7 Apr 2021 19:24:39 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Zhou Ti (x2019cwm)" <x2019cwm@...x.ca>
Subject: Re: [PATCH v1 0/5] cpuidle: Take possible negative "sleep length"
 values into account

On Mon, Mar 29, 2021 at 8:38 PM Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> Hi All,
>
> As follows from the discussion triggered by the patch at
>
> https://lore.kernel.org/lkml/20210311123708.23501-2-frederic@kernel.org/
>
> the cpuidle governors using tick_nohz_get_sleep_length() assume it to always
> return positive values which is not correct in general.
>
> To address this issues, first document the fact that negative values can
> be returned by tick_nohz_get_sleep_length() (patch [1/5]).  Then, in
> preparation for more substantial changes, change the data type of two
> fields in struct cpuidle_state to s64 so they can be used in computations
> involving negative numbers safely (patch [2/5]).
>
> Next, adjust the teo governor a bit so that negative "sleep length" values
> are counted like zero by it (patch [3/5]) and modify it so as to avoid
> mishandling negative "sleep length" values (patch [4/5]).
>
> Finally, make the menu governor take negative "sleep length" values into
> account properly (patch [5/5]).
>
> Please see the changelogs of the patches for details.

Given no objections or concerns regarding this lot, let me queue it up.

Thanks!