From: Krzysztof Kozlowski <k.kozlowski@samsung.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Kyungmin Park <kyungmin.park@samsung.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Tomasz Figa <t.figa@samsung.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Kukjin Kim <kgene.kim@samsung.com>,
linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org
Subject: Re: [patch 0/4] genirq/exynos timers: Fix the CPU hotplug wreckage sanely
Date: Wed, 16 Apr 2014 17:59:55 +0200 [thread overview]
Message-ID: <1397663995.19782.4.camel@AMDC1943> (raw)
In-Reply-To: <20140416142106.537575971@linutronix.de>
On śro, 2014-04-16 at 14:36 +0000, Thomas Gleixner wrote:
> The current implementation of irq_set_affinity() refuses rightfully to
> route an interrupt to an offline cpu.
>
> But there is a special case, where this is actually desired. Some of
> the ARM SoCs have per cpu timers which require setting the affinity
> during cpu startup where the cpu is not yet in the online mask.
>
> If we can't do that, then the local timer interrupt for the about to
> become online cpu is routed to some random online cpu.
>
> The developers of the affected machines tried to work around that
> issue, but that results in a massive mess in that timer code.
>
> It's saner to provide a facility to force the affinity and make the
> affected machines use that.
>
> The following series implements that logic w/o impact on any existing
> users.
>
> The change to the genirq core code is not that bad:
>
> arch/mips/cavium-octeon/octeon-irq.c | 2 +-
> include/linux/interrupt.h | 35 ++++++++++++++++++++++++++++++++++-
> include/linux/irq.h | 3 ++-
> kernel/irq/manage.c | 17 ++++++-----------
> 4 files changed, 43 insertions(+), 14 deletions(-)
>
> The resulting fixup for gic/exynos_mct is:
>
> clocksource/exynos_mct.c | 12 +++---------
> irqchip/irq-gic.c | 8 ++++++--
> 2 files changed, 9 insertions(+), 11 deletions(-)
>
> Krzysztofs proposed workaround was slightly smaller than that, but I
> prefer having a clean solution for backporting to stable rather than a
> messy hack around which works.
>
> @Krzysztof: Can you please retest the series? I've changed the core
> implementation versus the first attempt to make it less intrusive.
Works fine. Tested whole patchset on board with Exynos 3250.
Best regards,
Krzysztof
next prev parent reply other threads:[~2014-04-16 16:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-16 14:36 [patch 0/4] genirq/exynos timers: Fix the CPU hotplug wreckage sanely Thomas Gleixner
2014-04-16 14:36 ` [patch 2/4] irqchip: gic: Support forced affinity setting Thomas Gleixner
2014-04-17 21:39 ` [tip:irq/urgent] irqchip: Gic: " tip-bot for Thomas Gleixner
2014-04-16 14:36 ` [patch 1/4] genirq: Allow forcing cpu affinity of interrupts Thomas Gleixner
2014-04-17 21:39 ` [tip:irq/urgent] " tip-bot for Thomas Gleixner
2014-04-16 14:36 ` [patch 4/4] clocksource: exynos_mct: Register clock event after request_irq() Thomas Gleixner
2014-04-17 21:40 ` [tip:irq/urgent] clocksource: Exynos_mct: " tip-bot for Krzysztof Kozlowski
2014-04-16 14:36 ` [patch 3/4] clocksource: exynos_mct: Use irq_force_affinity() in cpu bringup Thomas Gleixner
2014-04-17 21:40 ` [tip:irq/urgent] clocksource: Exynos_mct: Use irq_force_affinity( ) " tip-bot for Thomas Gleixner
2014-04-16 15:59 ` Krzysztof Kozlowski [this message]
2014-04-16 21:16 ` [patch 0/4] genirq/exynos timers: Fix the CPU hotplug wreckage sanely Thomas Gleixner
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