linux-kernel - Re: [PATCH v2 22/25] timekeeping: Rework timekeeping_suspend() to use shadow

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Message-ID: <CANDhNCrniG3ehXxzFn4ULOdr6=tmzhR9Ti=gSdf5mQpftcG_tQ@mail.gmail.com>
Date: Thu, 24 Oct 2024 15:21:24 -0700
From: John Stultz <jstultz@...gle.com>
To: Anna-Maria Behnsen <anna-maria@...utronix.de>
Cc: Frederic Weisbecker <frederic@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	Miroslav Lichvar <mlichvar@...hat.com>, Richard Cochran <richardcochran@...il.com>, 
	Christopher S Hall <christopher.s.hall@...el.com>
Subject: Re: [PATCH v2 22/25] timekeeping: Rework timekeeping_suspend() to use shadow_timekeeper

On Wed, Oct 9, 2024 at 1:29 AM Anna-Maria Behnsen
<anna-maria@...utronix.de> wrote:
>
> From: Anna-Maria Behnsen <anna-maria@...utronix.de>
>
> Updates of the timekeeper can be done by operating on the shadow timekeeper
> and afterwards copying the result into the real timekeeper. This has the
> advantage, that the sequence count write protected region is kept as small
> as possible.
>
> While the sequence count held time is not relevant for the resume path as
> there is no concurrency, there is no reason to have this function
> different than all the other update sites.
>
> Convert timekeeping_inject_offset() to use this scheme and cleanup the
> variable declarations while at it.
>
> As halt_fast_timekeeper() does not need protection sequence counter, it is
> no problem to move it with this change outside of the sequence counter
> protected area. But it still needs to be executed while holding the lock.
>
> Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>

tk_shadow naming nit, but otherwise:
Acked-by: John Stultz <jstultz@...gle.com>