linux-kernel - Re: [PATCH v7 02/11] task_isolation: add initial support

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Message-ID: <alpine.DEB.2.11.1510011430390.4500@nanos>
Date:	Thu, 1 Oct 2015 14:31:06 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	Chris Metcalf <cmetcalf@...hip.com>,
	Gilad Ben Yossef <giladb@...hip.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Andy Lutomirski <luto@...capital.net>,
	linux-doc@...r.kernel.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 02/11] task_isolation: add initial support

On Thu, 1 Oct 2015, Frederic Weisbecker wrote:
> On Thu, Oct 01, 2015 at 02:18:42PM +0200, Thomas Gleixner wrote:
> > On Thu, 1 Oct 2015, Frederic Weisbecker wrote:
> > > On Mon, Sep 28, 2015 at 11:17:17AM -0400, Chris Metcalf wrote:
> > > > +
> > > > +	while (READ_ONCE(dev->next_event.tv64) != KTIME_MAX) {
> > > 
> > > You should add a function in tick-sched.c to get the next tick. This
> > > is supposed to be a private field.
> > 
> > Just to make it clear. Neither the above nor a similar check in
> > tick-sched.c is going to happen.
> > 
> > This busy waiting is just horrible. Get your act together and solve
> > the problems at the root and do not inflict your quick and dirty
> > 'solutions' on us.
> 
> That's why I proposed a wait-wake scheme instead with the tick stop
> code. What's your opinion about such direction?

Definitely more sensible than mindlessly busy looping.

Thanks,

	tglx
 
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