linux-kernel - Re: [PATCH 1/3] clocksource: exynos_mct: Fix stall after CPU hotplugging

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Date:	Wed, 16 Apr 2014 11:41:13 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
cc:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Tomasz Figa <t.figa@...sung.com>, stable@...r.kernel.org
Subject: Re: [PATCH 1/3] clocksource: exynos_mct: Fix stall after CPU
 hotplugging

On Wed, 16 Apr 2014, Krzysztof Kozlowski wrote:
> On wto, 2014-04-15 at 18:20 +0200, Thomas Gleixner wrote:
> > Here is a complete solution to the problem. We really want the drivers
> > to be fast and clean and not work around such issues.
> > 
> > I'm quite happy that I kept the 'force' argument of set_affinity
> > callbacks. I knew that I'd need it at some point.
> > 
> > So with the flag set we can disable the online mask check and force
> > the interrupt to the proper cpu.
> 
> Thanks for the solution.
> 
> I tested your patch on Exynos 3250 and it is still not sufficient. After
> hotplugging CPU1 ~10 times the stall happens (set_next_event is called
> on wrong CPU).
> 
> The patch 3/3 ("clocksource: exynos_mct: Fix too early ISR fire up on
> wrong CPU") is needed as the clockevents_config_and_register should be
> called a little later.

Ok. That makes sense.
 
> Do you have rest of patches (2/3 and 3/3) or should I resend them?
> 
> And one minor nit in your patch: 'cpu' local variable in
> exynos4_mct_cpu_notify() is no longer used so it can be removed.

Right.

I'm going to create a proper patch for the interrupt side and stick
that into irq/urgent. It's trivial enough to go in right away and I'll
tag it stable as well. You can build your changes on top then.

Thanks,

	tglx




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