linux-kernel - Re: [PATCH 2/4] timer: relax tick stop in idle entry

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Message-ID: <20151119190630.GP3816@twins.programming.kicks-ass.net>
Date:	Thu, 19 Nov 2015 20:06:30 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	John Stultz <john.stultz@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <len.brown@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Paul Turner <pjt@...gle.com>,
	Josh Triplett <josh@...htriplett.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH 2/4] timer: relax tick stop in idle entry

On Mon, Nov 16, 2015 at 04:09:10PM -0800, Jacob Pan wrote:
> On Mon, 16 Nov 2015 23:01:12 +0100 (CET)
> Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> > > For the second case, which is much more rare, I think we do have
> > > next timer exactly one tick away. Just don't know why tick will
> > > continue into idle loop.  
> > 
> > Well, it should not be hard to figure that out. There are not so many
> > checks involved when tick_nohz_irq_exit() is called.

> Thanks for the tip, I found the cause is in 
> int idle_cpu(int cpu)

Which one? That is, I cannot find a idle_cpu() call from
tick_nohz_irq_exit().
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