linux-kernel - Re: [PATCH v6 19/21] timer: Implement the hierarchical pull model

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Message-ID: <52a33c96-70ff-e670-acdf-7fc9b25884d7@linutronix.de>
Date:   Tue, 16 May 2023 14:49:56 +0200 (CEST)
From:   Anna-Maria Behnsen <anna-maria@...utronix.de>
To:     Sebastian Siewior <bigeasy@...utronix.de>
cc:     Frederic Weisbecker <frederic@...nel.org>,
        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>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Rik van Riel <riel@...riel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Lukasz Luba <lukasz.luba@....com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>
Subject: Re: [PATCH v6 19/21] timer: Implement the hierarchical pull model

On Mon, 15 May 2023, Sebastian Siewior wrote:

> On 2023-05-15 12:50:25 [+0200], Anna-Maria Behnsen wrote:
> > The part will be replaced by:
> > 
> > ---8<----
> > 
> > 	local_irq_disable();
> > 	timer_lock_remote_bases(cpu);
> 
> Do you s/raw_spin_lock_irq/raw_spin_lock/ in timer_lock_remote_bases()?
> Otherwise you disable interrupts twice. Not wrong but not needed.

Yes, I do so. And I also drop the return value and take the locks
unconditianlly.

> > 	raw_spin_lock(&tmc->lock);
> > 
> > 	if (!tmc->online || !tmc->idle) {
> > 		timer_unlock_remote_bases(cpu);
> > 		goto unlock;
> > 	} else {
> > 	        fetch_next_timer_interrupt_remote(jif, now, &tevt, cpu);
> > 	}
> > 
> > 	timer_unlock_remote_bases(cpu);
> 
> The locking, unlocking and fetch_next_timer_interrupt_remote() is only
> used here. So it if it wouldn't be for tmc-> then you could do
> everything timer.c in once place…

I thought about it, but then the logic has to be moved to timer.c but it is
timer_migration related code... I would like to keep the logic here in
timer_migration code... will send a v7 soon.

Thanks,

	Anna-Maria