linux-kernel - Re: [PATCH 15/15] tick: Assume timekeeping is correctly handed over upon last offline idle call

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Message-ID: <87bk99iw8h.ffs@tglx>
Date: Thu, 25 Jan 2024 10:43:42 +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 15/15] tick: Assume timekeeping is correctly handed over
 upon last offline idle call

On Wed, Jan 24 2024 at 18:04, Frederic Weisbecker wrote:
> The timekeeping duty is handed over from the outgoing CPU on stop
> machine, then the oneshot tick is stopped right after.  Therefore it's
> guaranteed that the current CPU isn't the timekeeper upon its last call
> to idle.
>
> Besides, calling tick_nohz_idle_stop_tick() while the dying CPU goes
> into idle suggests that the tick is going to be stopped while it is
> actually stopped already from the appropriate CPU hotplug state.
>
> Remove the confusing call and the obsolete case handling and convert it
> to a sanity check that verifies the above assumption.
>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

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