linux-kernel - Re: PROBLEM: BUG appearing when trying to allocate interrupt on Exynos MCT after CPU hotplug

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Message-ID: <54CC9EB2.7010409@linaro.org>
Date:	Sat, 31 Jan 2015 10:21:54 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Stephen Boyd <sboyd@...eaurora.org>,
	Marcin Jabrzyk <m.jabrzyk@...sung.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Kukjin Kim <kgene.kim@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	linux-kernel@...r.kernel.org, kyungmin.park@...sung.com,
	linux-samsung-soc@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-arm-kernel@...ts.infradead.org,
	Mark Rutland <Mark.Rutland@....com>,
	Chander Kashyap <chander.kashyap@...aro.org>
Subject: Re: PROBLEM: BUG  appearing when trying to allocate interrupt on Exynos MCT after CPU hotplug

On 01/31/2015 02:08 AM, Stephen Boyd wrote:
> Kept meaning to get back to this thread. Have you resolved it?
>
> On 10/29/14 03:38, Marcin Jabrzyk wrote:
>> So I've tried this patch, it resolves one problem but introduces also
>> new ones. As expected the BUG warning is not showing after applying
>> this patch but there are some interesting side effects.
>
> Well that's half good news.
>
>> I was looking on /proc/interrupts output. IRQ for CPU0 have "MCT" name
>> and IRQ for CPU1 has unexpectedly no name at all.
>
> This is pretty confusing. I don't see how the patch could cause this to
> happen.
>
>> After making hotplug cycle of CPU1 I've observed that IRQs attached
>> originally for that CPU are generating on really low count and not in
>> order with IRQ for CPU0.
>> What's more the interrupt for CPU1 is showing to me as being counted
>> for both CPUs, so it's probably not being attached to CPU1.
>>
>
> yeah. Can you give the output of /proc/timer_list in addition to
> /proc/interrupts? It may give some hints on what's going on. It may also
> be interesting to see if irq_force_affinity() is failing. Please check
> the return value and print an error

Hi Stephen, Marcin,

can you have a look if the patch [1] fixes this issue ?

  -- Daniel

[1] https://lkml.org/lkml/2015/1/30/423


> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
> index 1800053b4644..3c4538e26731 100644
> --- a/drivers/clocksource/exynos_mct.c
> +++ b/drivers/clocksource/exynos_mct.c
> @@ -450,6 +450,7 @@ static int exynos4_local_timer_setup(struct clock_event_device *evt)
>   {
>   	struct mct_clock_event_device *mevt;
>   	unsigned int cpu = smp_processor_id();
> +	int ret;
>
>   	mevt = container_of(evt, struct mct_clock_event_device, evt);
>
> @@ -468,7 +469,9 @@ static int exynos4_local_timer_setup(struct clock_event_device *evt)
>   	if (mct_int_type == MCT_INT_SPI) {
>   		evt->irq = mct_irqs[MCT_L0_IRQ + cpu];
>   		enable_irq(evt->irq);
> -		irq_force_affinity(mct_irqs[MCT_L0_IRQ + cpu], cpumask_of(cpu));
> +		ret = irq_force_affinity(mct_irqs[MCT_L0_IRQ + cpu], cpumask_of(cpu));
> +		if (ret)
> +			pr_err("force failed %d\n", ret);
>   	} else {
>   		enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0);
>   	}
>


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