linux-kernel - Re: [PATCH v2] time: Make sure jiffies_to_msecs() preserves non-zero time periods

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Message-ID: <CAK8P3a3OHT-tEHoh7MbGMU5m-L3mNkBVf=L5YgwgP4jQVV9SCA@mail.gmail.com>
Date:   Fri, 22 Jun 2018 10:19:51 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] time: Make sure jiffies_to_msecs() preserves non-zero
 time periods

On Fri, Jun 22, 2018 at 9:54 AM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> For the common cases where 1000 is a multiple of HZ, or HZ is a multiple
> of 1000, jiffies_to_msecs() never returns zero when passed a non-zero
> time period.
>
> However, if HZ > 1000 and not an integer multiple of 1000 (e.g. 1024 or
> 1200, as used on alpha and DECstation), jiffies_to_msecs() may return
> zero for small non-zero time periods.  This may break code that relies
> on receiving back a non-zero value.
>
> jiffies_to_usecs() does not need such a fix, as <linux/jiffies.h> does
> not support values of HZ larger than 12287, thus rejecting any
> problematic huge values of HZ.
>
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---

Looks good to me,

Reviewed-by: Arnd Bergmann <arnd@...db.de>