linux-kernel - Re: [patch V2 05/10] timer: Retrieve next expiry of pinned/non-pinned timers seperately

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Message-ID: <alpine.DEB.2.20.1704191154200.1829@nanos>
Date:   Wed, 19 Apr 2017 11:56:19 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     LKML <linux-kernel@...r.kernel.org>,
        John Stultz <john.stultz@...aro.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pm@...r.kernel.org, Arjan van de Ven <arjan@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Richard Cochran <rcochran@...utronix.de>
Subject: Re: [patch V2 05/10] timer: Retrieve next expiry of pinned/non-pinned
 timers seperately

On Wed, 19 Apr 2017, Peter Zijlstra wrote:
> On Tue, Apr 18, 2017 at 01:11:07PM +0200, Thomas Gleixner wrote:
> > +
> > +	/*
> > +	 * If the local queue expires first, there is no requirement for
> > +	 * queuing the CPU in the global expiry mechanism.
> 
> The comment doesn't make sense... (maybe at this stage)

Yeah, it's only useful once the real magic is in place.

> > +	 */
> > +	if (!local_first && !global_empty)
> > +		*global_evt = basem + (nextevt_global - basej) * TICK_NSEC;
> 
> I was initially thinking !local_first would have to imply !global_empty,
> but after going back and reading the previous patches again, I found
> this was not so. Still slightly surprising.

Indeed, that's confusing.

Thanks,

	tglx