Date: Thu, 19 Nov 2015 20:06:30 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        John Stultz <john.stultz@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Arjan van de Ven <arjan@linux.intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Len Brown <len.brown@intel.com>,
        Rafael Wysocki <rafael.j.wysocki@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>, Paul Turner <pjt@google.com>,
        Josh Triplett <josh@joshtriplett.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH 2/4] timer: relax tick stop in idle entry
Message-ID: <20151119190630.GP3816@twins.programming.kicks-ass.net>
References: <1447444387-23525-1-git-send-email-jacob.jun.pan@linux.intel.com>
 <1447444387-23525-3-git-send-email-jacob.jun.pan@linux.intel.com>
 <alpine.DEB.2.11.1511131516180.3987@nanos>
 <20151113142438.3144d47d@icelake>
 <alpine.DEB.2.11.1511161558550.3761@nanos>
 <20151116135126.5a50e45d@icelake>
 <alpine.DEB.2.11.1511162255430.3761@nanos>
 <20151116160910.3811c8ca@icelake>
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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@linutronix.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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