linux-kernel - Re: [PATCH] timers: Remove historical extra jiffie for timeout in msleep()

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Message-ID: <CAJZ5v0j286a-uc0xF-hkb+6qwrWruchCzABCUQJY1NaoLMY8MA@mail.gmail.com>
Date: Thu, 29 Aug 2024 11:34:03 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Anna-Maria Behnsen <anna-maria@...utronix.de>
Cc: linux-kernel@...r.kernel.org, Frederic Weisbecker <frederic@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>
Subject: Re: [PATCH] timers: Remove historical extra jiffie for timeout in msleep()

On Thu, Aug 29, 2024 at 9:41 AM Anna-Maria Behnsen
<anna-maria@...utronix.de> wrote:
>
> msleep() as well as msleep_interruptible() add a jiffie to the
> timeout. This extra jiffie was introduced in former days to ensure timeout
> will not happen earlier than specified. But the timer wheel already takes
> care during enqueue that timers will not expire earlier than specified.
>
> Remove this extra jiffie in msleep() and msleep_interruptible().
>
> Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
>  kernel/time/timer.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index 64b0d8a0aa0f..18aa759c3cae 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -2730,7 +2730,7 @@ void __init init_timers(void)
>   */
>  void msleep(unsigned int msecs)
>  {
> -       unsigned long timeout = msecs_to_jiffies(msecs) + 1;
> +       unsigned long timeout = msecs_to_jiffies(msecs);
>
>         while (timeout)
>                 timeout = schedule_timeout_uninterruptible(timeout);
> @@ -2744,7 +2744,7 @@ EXPORT_SYMBOL(msleep);
>   */
>  unsigned long msleep_interruptible(unsigned int msecs)
>  {
> -       unsigned long timeout = msecs_to_jiffies(msecs) + 1;
> +       unsigned long timeout = msecs_to_jiffies(msecs);
>
>         while (timeout && !signal_pending(current))
>                 timeout = schedule_timeout_interruptible(timeout);
> --
> 2.39.2
>