linux-kernel - Re: [PATCH 13/15] tick: Split nohz and highres features from nohz

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Date: Thu, 25 Jan 2024 10:42:13 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Frederic Weisbecker <frederic@...nel.org>, LKML
 <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>, Ingo Molnar
 <mingo@...nel.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>, Peng
 Liu <liupeng17@...ovo.com>, Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 13/15] tick: Split nohz and highres features from nohz_mode

On Wed, Jan 24 2024 at 18:04, Frederic Weisbecker wrote:

> The nohz mode field tells about low resolution nohz mode or high
> resolution nohz mode but it doesn't tell about high resolution non-nohz
> mode.
>
> In order to retrieve the latter state, tick_cancel_sched_timer() must
> fiddle with struct hrtimer's internals to guess if the tick has been
> initialized in high resolution.
>
> Move instead the nohz mode field information into the tick flags and
> provide two new bits: one to know if the tick is in nohz mode and
> another one to know if the tick is in high resolution. The combination
> of those two flags provides all the needed informations to determine
> which of the three tick modes is running.
>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>