Re: [PATCH] irqchip/gic-v3-its: fix ITS queue timeout

From: Yang Yingliang
Date: Tue Jun 05 2018 - 21:43:35 EST


Hi, Julien

On 2018/6/5 18:16, Julien Thierry wrote:
Hi Yang,

On 05/06/18 07:30, Yang Yingliang wrote:
When the kernel booted with maxcpus=x, 'x' is smaller
than actual cpu numbers, the TAs of offline cpus won't
be set to its->collection.

If LPI is bind to offline cpu, sync cmd will use zero TA,
it leads to ITS queue timeout. Fix this by choosing a
online cpu, if there is no online cpu in cpu_mask.

Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
---
drivers/irqchip/irq-gic-v3-its.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 5416f2b..edd92a9 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -2309,7 +2309,9 @@ static int its_irq_domain_activate(struct irq_domain *domain,
cpu_mask = cpumask_of_node(its_dev->its->numa_node);
/* Bind the LPI to the first possible CPU */
- cpu = cpumask_first(cpu_mask);
+ cpu = cpumask_first_and(cpu_mask, cpu_online_mask);
+ if (!cpu_online(cpu))

Testing for cpu being online here feels a bit redundant.

Since cpu is online if the cpumask_first_and returns a valid cpu, I think you could replace this test with:

if (cpu >= nr_cpu_ids)
Yes, I used wrong check here, according to comment of cpumask_first_and, this func will returns >= nr_cpu_ids if no cpus set in both.

I'll send v2 later.

+ cpu = cpumask_first(cpu_online_mask);
its_dev->event_map.col_map[event] = cpu;
irq_data_update_effective_affinity(d, cpumask_of(cpu));
@@ -2466,7 +2468,10 @@ static int its_vpe_set_affinity(struct irq_data *d,
bool force)
{
struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
- int cpu = cpumask_first(mask_val);
+ int cpu = cpumask_first_and(mask_val, cpu_online_mask);
+
+ if (!cpu_online(cpu))

Same thing here.

+ cpu = cpumask_first(cpu_online_mask);
/*
* Changing affinity is mega expensive, so let's be as lazy as


Cheers,


Thanks,
Yang