From: t.figa@samsung.com (Tomasz Figa)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] irqchip: gic: Allow setting affinity to offline CPUs
Date: Tue, 20 Aug 2013 18:41:54 +0200 [thread overview]
Message-ID: <3879851.vmCHJ3AcgQ@amdc1227> (raw)
In-Reply-To: <52139A5B.5040708@codeaurora.org>
On Tuesday 20 of August 2013 09:33:31 Stephen Boyd wrote:
> On 08/20/13 09:11, Tomasz Figa wrote:
> > Sometimes it is necessary to fix interrupt affinity to an offline CPU,
> > for example in initialization of local timers. This patch modifies
> > .set_affinity() operation of irq-gic driver to fall back to any
> > possible
> > CPU if no online CPU can be found in requested CPU mask.
> >
> > This fixes broken Exynos4210 support since commit
> >
> > ee98d27df6 ARM: EXYNOS4: Divorce mct from local timer API
> >
> > caused by timer initialization code unable to set affinity for local
> > timer interrupts.
>
> Care to elaborate further? I don't see how the interrupt affinity is set
> for a CPU that isn't online because the mct code runs on the CPU that
> the affinity is being set to.
Well, please look at secondary_start_kernel() in arch/arm/kernel/smp.c [1].
You can see that notify_cpu_starting() (line 348) that fires the notifier
registered in MCT driver is called before set_cpu_online() (line 359) that
marks the CPU as online. Also notice that, originally, local timer
initialization was happening after set_cpu_online() - see line 365.
[1] - http://lxr.free-electrons.com/source/arch/arm/kernel/smp.c?a=arm#L312
Best regards,
Tomasz
next prev parent reply other threads:[~2013-08-20 16:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-20 16:11 [PATCH] irqchip: gic: Allow setting affinity to offline CPUs Tomasz Figa
2013-08-20 16:33 ` Stephen Boyd
2013-08-20 16:41 ` Tomasz Figa [this message]
2013-08-20 16:48 ` Stephen Boyd
2013-08-20 16:57 ` Tomasz Figa
2013-08-20 21:14 ` Russell King - ARM Linux
2013-08-20 22:11 ` Tomasz Figa
2013-08-20 22:39 ` Stephen Boyd
2013-08-21 12:23 ` Tomasz Figa
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