* [patch 0/4] genirq/exynos timers: Fix the CPU hotplug wreckage sanely
[not found] <20140416142106.537575971@linutronix.de>
@ 2014-04-16 15:59 ` Krzysztof Kozlowski
2014-04-16 21:16 ` Thomas Gleixner
0 siblings, 1 reply; 2+ messages in thread
From: Krzysztof Kozlowski @ 2014-04-16 15:59 UTC (permalink / raw)
To: linux-arm-kernel
On ?ro, 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
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