linux-kernel - Re: [PATCH v10 05/20] timers: Introduce add_timer() variants which modify timer flags

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Date: Wed, 17 Jan 2024 18:01:07 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Anna-Maria Behnsen <anna-maria@...utronix.de>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	John Stultz <jstultz@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Eric Dumazet <edumazet@...gle.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Arjan van de Ven <arjan@...radead.org>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Rik van Riel <riel@...riel.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sebastian Siewior <bigeasy@...utronix.de>,
	Giovanni Gherdovich <ggherdovich@...e.cz>,
	Lukasz Luba <lukasz.luba@....com>,
	"Gautham R . Shenoy" <gautham.shenoy@....com>,
	Srinivas Pandruvada <srinivas.pandruvada@...el.com>,
	K Prateek Nayak <kprateek.nayak@....com>
Subject: Re: [PATCH v10 05/20] timers: Introduce add_timer() variants which
 modify timer flags

Le Mon, Jan 15, 2024 at 03:37:28PM +0100, Anna-Maria Behnsen a écrit :
>  timer flags

Yes ;-)

> 
> A timer might be used as a pinned timer (using add_timer_on()) and later on
> as non-pinned timer using add_timer(). When the "NOHZ timer pull at expiry
> model" is in place, the TIMER_PINNED flag is required to be used whenever a
> timer needs to expire on a dedicated CPU. Otherwise the flag must not be
> set if expiration on a dedicated CPU is not required.
> 
> add_timer_on()'s behavior will be changed during the preparation patches
> for the "NOHZ timer pull at expiry model" to unconditionally set
> TIMER_PINNED flag. To be able to clear/ set the flag when queueing a
> timer, two variants of add_timer() are introduced.
> 
> This is a preparatory patch and has no functional change.
> 
> Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>

Reviewed-by: Frederic Weisbecker <frederic@...nel.org>