linux-kernel - Re: [PATCH] timers: fix offset calculation when the expires align with LVL

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Message-ID: <alpine.DEB.2.21.1807311633430.1610@nanos.tec.linutronix.de>
Date:   Tue, 31 Jul 2018 16:34:37 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Xu YiPing <xuyiping@...ilicon.com>
cc:     john.stultz@...aro.org, sboyd@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] timers: fix offset calculation when the expires align
 with LVL_GRAN



On Tue, 31 Jul 2018, Thomas Gleixner wrote:

> On Tue, 31 Jul 2018, Xu YiPing wrote:
> > On 2018/7/30 19:03, Thomas Gleixner wrote:
> > >
> > > __internal_add_timer(base, timer)
> > > {  
> > >    idx = calc_wheel_index(1, 1)
> > >        {
> > >            delta = 1 - 1;	<-   0
> > > 
> > >            if (0 < LVL_START(1))
> > >                idx = calc_index(1, 0)
> > >                     {
> > >                         expires = (1 + LVL_GRAN(0) - 1) >> LVL_SHIFT(0);
> > > 			----> expires = 0
> > 			
> > 			LVL_GRAN(0) = 1 and LVL_SHIFT(0) = 0
> > 			
> > 			after the calculation, expires = 1 ?
> 
> Indeed. You're right. Math is hard... So the index would be 1 and still not
> fulfil the below:

Hmm, crap. Let me think about it some more. 34C is way too hot to think.

Thanks,

	tglx