Re: PROBLEM:ÂBUG appearing when trying to allocate interrupt on Exynos MCT after CPU hotplug

From: Marcin Jabrzyk
Date: Mon Feb 02 2015 - 03:47:42 EST




On 31/01/15 10:21, Daniel Lezcano wrote:
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


Hi Daniel,

I've checked this patch on the board that have problems and it fixes this issue completely. Everything looks fine after power cycle of the CPU.

Best regards,
Marcin Jabrzyk

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);
}




--
Samsung R&D Institute Poland
Samsung Electronics
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