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

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Message-ID: <20151117102449.GR3816@twins.programming.kicks-ass.net>
Date:	Tue, 17 Nov 2015 11:24:49 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Josh Triplett <josh@...htriplett.org>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	John Stultz <john.stultz@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	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>
Subject: Re: [PATCH 2/4] timer: relax tick stop in idle entry

On Mon, Nov 16, 2015 at 09:04:03PM -0800, Paul E. McKenney wrote:
> On Mon, Nov 16, 2015 at 06:57:14PM -0800, Arjan van de Ven wrote:
> > On 11/16/2015 6:53 PM, Paul E. McKenney wrote:
> > >Fair point.  When in the five-jiffy throttling state, what can wake up
> > >a CPU?  In an earlier version of this proposal, the answer was "nothing",
> > >but maybe that has changed.
> > 
> > device interrupts are likely to wake the cpus.
> 
> OK, that I cannot help you with.  But presumably if the interrupt handler
> does a wakeup (or similar), that is deferred to the end of the throttling
> interval?  Timers are also deferred, including hrtimers?

This throttling thing only throttles 'normal' tasks, real-time tasks
will still run.
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