linux-kernel - Re: [PATCH 10/25] hrtimer: Make handling of hrtimer reprogramming and enqueuing not conditional

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Message-ID: <20170926121435.sr35j6anagg5ckof@hirez.programming.kicks-ass.net>
Date:   Tue, 26 Sep 2017 14:14:35 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Anna-Maria Gleixner <anna-maria@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Christoph Hellwig <hch@....org>, keescook@...omium.org,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 10/25] hrtimer: Make handling of hrtimer reprogramming
 and enqueuing not conditional

On Thu, Aug 31, 2017 at 12:23:38PM -0000, Anna-Maria Gleixner wrote:
> The hrtimer_reprogramming, remote timer enqueuing and handling of the
> hrtimer_cpu_base struct member expires_next depend on the active high
> resolution timers. This makes the code harder to understand.
> 
> To simplify the code, the hrtimer reprogramming is now executed
> independently except for the real reprogramming part. The expires_next
> stores now the first enqueued timer. Due to the adaption of the
> check_target function, remote enqueuing is now only possible when the
> expiry time is after the currently first expiry time independent of the
> active high resolution timers.

Sorry, very hard to follow. What?

So we do this to unconditionally track expire_next, such that we can
(later) use hrtimer_check_target()?