linux-kernel - Re: [PATCH 2/3] clockevents: Restart clockevent device before using it again

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Date:	Thu, 2 Apr 2015 18:04:35 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kevin Hilman <khilman@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 2/3] clockevents: Restart clockevent device before using
 it again


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Thu, Apr 02, 2015 at 07:20:50PM +0530, Viresh Kumar wrote:
> > > Or am I completely missing something?
> > 
> > So yes, if we would have done that in tick_program_event(), it would have
> > been a single place for doing this change..
> > 
> > But, when Thomas ranted [1] at me on this earlier, he said:
> > 
> > "
> > No, we are not doing a state change behind the scene and a magic
> > restore.
> > 
> > 2B) Implement the ONESHOT_STOPPED logic and make sure all of the core
> >     code is aware of it.
> > "
> > 
> 
> lkml.org didn't work for me, alternative link:
> 
> http://marc.info/?l=linux-kernel&m=139966616803683&w=2
> 
> So I've read that (several times) and I thing Thomas meant something
> else.
> 
> So I think he disliked what you did to the clockevent layer, not so much
> you touching tick_program_event(). But the last_state thing (which was
> broken), and you imposing the SHUTDOWN policy for everybody.
> 
> But with the optional ONESHOT_STOPPED state both those are gone, and
> we'd end up with the much simpler patch below.
> 
> Further note that tick-oneshot is the natural place to do this, that is
> the glue layer between the (oneshot) clockevents stuff and the timer
> stuff. Pulling clockevents into hrtimers feels wrong.
> 
> Ingo, do you agree with that after reading Thomas' email?

Yeah, I suppose ...

Thanks,

	Ingo
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