[PATCH] ARM: irq: Add IRQ_SET_MASK_OK_DONE handling in migrate_one_irq()

[PATCH] ARM: irq: Add IRQ_SET_MASK_OK_DONE handling in migrate_one_irq()

[Dietmar Eggemann]

Arm TC2 (multi_v7_defconfig plus CONFIG_ARM_BIG_LITTLE_CPUFREQ=y and
CONFIG_ARM_VEXPRESS_SPC_CPUFREQ=y) fails hotplug stress tests.

This issue was tracked down to a missing copy of the new affinity
cpumask of the vexpress-spc interrupt into struct
irq_common_data.affinity when the interrupt is migrated in
migrate_one_irq().

Commit 0407daceedfe ("irqchip/gic: Return IRQ_SET_MASK_OK_DONE in the
set_affinity method") changed the return value of the irq_set_affinity()
function of the GIC from IRQ_SET_MASK_OK to IRQ_SET_MASK_OK_DONE.

In migrate_one_irq() if the current irq affinity mask and the cpu
online mask do not share any CPU, the affinity mask is set to the cpu
online mask. In this case (ret == true) and when the irq chip
function irq_set_affinity() returns successfully (IRQ_SET_MASK_OK),
struct irq_common_data.affinity should also be updated.

Add IRQ_SET_MASK_OK_DONE next to IRQ_SET_MASK_OK when checking that the
irq chip function irq_set_affinity() returns successfully.

Commit 2cb625478f8c ("genirq: Add IRQ_SET_MASK_OK_DONE to support
stacked irqchip") only added IRQ_SET_MASK_OK_DONE handling to
irq_do_set_affinity() in the irq core and not to the Arm32 irq code.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---

The hotplug issue on Arm TC2 happens because the vexpress-spc interrupt
(irq=22) is affine to CPU0. This occurs since it is setup early when the
cpu_online_mask is still 0.
But the problem with the missing copy of the affinity mask should occur
with every interrupt which is forced to migrate.

With additional debug in irq_setup_affinity():

[0.000619] irq_setup_affinity(): irq=17 mask=0 cpu_online_mask=0 set=0-4
[0.007065] irq_setup_affinity(): irq=22 mask=0 cpu_online_mask=0 set=0-4
[3.372907] irq_setup_affinity(): irq=47 mask=0-4 cpu_online_mask=0-4
set=0-4

cat /proc/interrupts
           CPU0       CPU1       CPU2       CPU3       CPU4
22:        316          0          0          0          0     GIC-0 127
Level     vexpress-spc

cat /proc/irq/22/smp_affinity_list 
0

 arch/arm/kernel/irq.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
index 9908dacf9229..ddb828b0235b 100644
--- a/arch/arm/kernel/irq.c
+++ b/arch/arm/kernel/irq.c
@@ -117,6 +117,7 @@ static bool migrate_one_irq(struct irq_desc *desc)
 	const struct cpumask *affinity = irq_data_get_affinity_mask(d);
 	struct irq_chip *c;
 	bool ret = false;
+	int ret2;
 
 	/*
 	 * If this is a per-CPU interrupt, or the affinity does not
@@ -131,9 +132,14 @@ static bool migrate_one_irq(struct irq_desc *desc)
 	}
 
 	c = irq_data_get_irq_chip(d);
-	if (!c->irq_set_affinity)
+	if (!c->irq_set_affinity) {
 		pr_debug("IRQ%u: unable to set affinity\n", d->irq);
-	else if (c->irq_set_affinity(d, affinity, false) == IRQ_SET_MASK_OK && ret)
+		return ret;
+	}
+
+	ret2 = c->irq_set_affinity(d, affinity, false);
+
+	if ((ret2 == IRQ_SET_MASK_OK || ret2 == IRQ_SET_MASK_OK_DONE) && ret)
 		cpumask_copy(irq_data_get_affinity_mask(d), affinity);
 
 	return ret;
-- 
2.11.0

Re: [PATCH] ARM: irq: Add IRQ_SET_MASK_OK_DONE handling in migrate_one_irq()

[Marc Zyngier]

Hi Dietmar,

On 08/01/2019 13:58, Dietmar Eggemann wrote:
> Arm TC2 (multi_v7_defconfig plus CONFIG_ARM_BIG_LITTLE_CPUFREQ=y and
> CONFIG_ARM_VEXPRESS_SPC_CPUFREQ=y) fails hotplug stress tests.
> 
> This issue was tracked down to a missing copy of the new affinity
> cpumask of the vexpress-spc interrupt into struct
> irq_common_data.affinity when the interrupt is migrated in
> migrate_one_irq().
> 
> Commit 0407daceedfe ("irqchip/gic: Return IRQ_SET_MASK_OK_DONE in the
> set_affinity method") changed the return value of the irq_set_affinity()
> function of the GIC from IRQ_SET_MASK_OK to IRQ_SET_MASK_OK_DONE.
> 
> In migrate_one_irq() if the current irq affinity mask and the cpu
> online mask do not share any CPU, the affinity mask is set to the cpu
> online mask. In this case (ret == true) and when the irq chip
> function irq_set_affinity() returns successfully (IRQ_SET_MASK_OK),
> struct irq_common_data.affinity should also be updated.
> 
> Add IRQ_SET_MASK_OK_DONE next to IRQ_SET_MASK_OK when checking that the
> irq chip function irq_set_affinity() returns successfully.
> 
> Commit 2cb625478f8c ("genirq: Add IRQ_SET_MASK_OK_DONE to support
> stacked irqchip") only added IRQ_SET_MASK_OK_DONE handling to
> irq_do_set_affinity() in the irq core and not to the Arm32 irq code.
> 
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> ---
> 
> The hotplug issue on Arm TC2 happens because the vexpress-spc interrupt
> (irq=22) is affine to CPU0. This occurs since it is setup early when the
> cpu_online_mask is still 0.
> But the problem with the missing copy of the affinity mask should occur
> with every interrupt which is forced to migrate.
> 
> With additional debug in irq_setup_affinity():
> 
> [0.000619] irq_setup_affinity(): irq=17 mask=0 cpu_online_mask=0 set=0-4
> [0.007065] irq_setup_affinity(): irq=22 mask=0 cpu_online_mask=0 set=0-4
> [3.372907] irq_setup_affinity(): irq=47 mask=0-4 cpu_online_mask=0-4
> set=0-4
> 
> cat /proc/interrupts
>            CPU0       CPU1       CPU2       CPU3       CPU4
> 22:        316          0          0          0          0     GIC-0 127
> Level     vexpress-spc
> 
> cat /proc/irq/22/smp_affinity_list 
> 0
> 
>  arch/arm/kernel/irq.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
> index 9908dacf9229..ddb828b0235b 100644
> --- a/arch/arm/kernel/irq.c
> +++ b/arch/arm/kernel/irq.c
> @@ -117,6 +117,7 @@ static bool migrate_one_irq(struct irq_desc *desc)
>  	const struct cpumask *affinity = irq_data_get_affinity_mask(d);
>  	struct irq_chip *c;
>  	bool ret = false;
> +	int ret2;
>  
>  	/*
>  	 * If this is a per-CPU interrupt, or the affinity does not
> @@ -131,9 +132,14 @@ static bool migrate_one_irq(struct irq_desc *desc)
>  	}
>  
>  	c = irq_data_get_irq_chip(d);
> -	if (!c->irq_set_affinity)
> +	if (!c->irq_set_affinity) {
>  		pr_debug("IRQ%u: unable to set affinity\n", d->irq);
> -	else if (c->irq_set_affinity(d, affinity, false) == IRQ_SET_MASK_OK && ret)
> +		return ret;
> +	}
> +
> +	ret2 = c->irq_set_affinity(d, affinity, false);
> +
> +	if ((ret2 == IRQ_SET_MASK_OK || ret2 == IRQ_SET_MASK_OK_DONE) && ret)
>  		cpumask_copy(irq_data_get_affinity_mask(d), affinity);
>  
>  	return ret;
> 

On the arm64 side, we've solved the exact same issue by getting rid of
this code and using the generic implementation. See 217d453d473c5
("arm64: fix a migrating irq bug when hotplug cpu"), which uses
irq_migrate_all_off_this_cpu instead.

I'm not sure there is much value in not using the core code in this case.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH] ARM: irq: Add IRQ_SET_MASK_OK_DONE handling in migrate_one_irq()

[Dietmar Eggemann]

Hi Marc,

On 1/8/19 3:16 PM, Marc Zyngier wrote:
> Hi Dietmar,
> 
> On 08/01/2019 13:58, Dietmar Eggemann wrote:
>> Arm TC2 (multi_v7_defconfig plus CONFIG_ARM_BIG_LITTLE_CPUFREQ=y and
>> CONFIG_ARM_VEXPRESS_SPC_CPUFREQ=y) fails hotplug stress tests.
>>
>> This issue was tracked down to a missing copy of the new affinity
>> cpumask of the vexpress-spc interrupt into struct
>> irq_common_data.affinity when the interrupt is migrated in
>> migrate_one_irq().
>>
>> Commit 0407daceedfe ("irqchip/gic: Return IRQ_SET_MASK_OK_DONE in the
>> set_affinity method") changed the return value of the irq_set_affinity()
>> function of the GIC from IRQ_SET_MASK_OK to IRQ_SET_MASK_OK_DONE.
>>
>> In migrate_one_irq() if the current irq affinity mask and the cpu
>> online mask do not share any CPU, the affinity mask is set to the cpu
>> online mask. In this case (ret == true) and when the irq chip
>> function irq_set_affinity() returns successfully (IRQ_SET_MASK_OK),
>> struct irq_common_data.affinity should also be updated.
>>
>> Add IRQ_SET_MASK_OK_DONE next to IRQ_SET_MASK_OK when checking that the
>> irq chip function irq_set_affinity() returns successfully.
>>
>> Commit 2cb625478f8c ("genirq: Add IRQ_SET_MASK_OK_DONE to support
>> stacked irqchip") only added IRQ_SET_MASK_OK_DONE handling to
>> irq_do_set_affinity() in the irq core and not to the Arm32 irq code.
>>
>> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
>> ---
>>
>> The hotplug issue on Arm TC2 happens because the vexpress-spc interrupt
>> (irq=22) is affine to CPU0. This occurs since it is setup early when the
>> cpu_online_mask is still 0.
>> But the problem with the missing copy of the affinity mask should occur
>> with every interrupt which is forced to migrate.
>>
>> With additional debug in irq_setup_affinity():
>>
>> [0.000619] irq_setup_affinity(): irq=17 mask=0 cpu_online_mask=0 set=0-4
>> [0.007065] irq_setup_affinity(): irq=22 mask=0 cpu_online_mask=0 set=0-4
>> [3.372907] irq_setup_affinity(): irq=47 mask=0-4 cpu_online_mask=0-4
>> set=0-4
>>
>> cat /proc/interrupts
>>             CPU0       CPU1       CPU2       CPU3       CPU4
>> 22:        316          0          0          0          0     GIC-0 127
>> Level     vexpress-spc
>>
>> cat /proc/irq/22/smp_affinity_list
>> 0

[...]

> 
> On the arm64 side, we've solved the exact same issue by getting rid of
> this code and using the generic implementation. See 217d453d473c5
> ("arm64: fix a migrating irq bug when hotplug cpu"), which uses
> irq_migrate_all_off_this_cpu instead.
> 
> I'm not sure there is much value in not using the core code in this case.

Thanks for the hint! Much more elegant! I tried the following on TC2 and 
it worked just fine. I'm not aware on any drawbacks of using the generic 
irq migration for Arm32 as well.

-- >8 --

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 664e918e2624..26524b75970a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1400,6 +1400,7 @@ config NR_CPUS
  config HOTPLUG_CPU
         bool "Support for hot-pluggable CPUs"
         depends on SMP
+       select GENERIC_IRQ_MIGRATION
         help
           Say Y here to experiment with turning CPUs off and on.  CPUs
           can be controlled through /sys/devices/system/cpu.
diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h
index c883fcbe93b6..46d41140df27 100644
--- a/arch/arm/include/asm/irq.h
+++ b/arch/arm/include/asm/irq.h
@@ -25,7 +25,6 @@
  #ifndef __ASSEMBLY__
  struct irqaction;
  struct pt_regs;
-extern void migrate_irqs(void);

  extern void asm_do_IRQ(unsigned int, struct pt_regs *);
  void handle_IRQ(unsigned int, struct pt_regs *);
diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
index 9908dacf9229..844861368cd5 100644
--- a/arch/arm/kernel/irq.c
+++ b/arch/arm/kernel/irq.c
@@ -31,7 +31,6 @@
  #include <linux/smp.h>
  #include <linux/init.h>
  #include <linux/seq_file.h>
-#include <linux/ratelimit.h>
  #include <linux/errno.h>
  #include <linux/list.h>
  #include <linux/kallsyms.h>
@@ -109,64 +108,3 @@ int __init arch_probe_nr_irqs(void)
         return nr_irqs;
  }
  #endif
-
-#ifdef CONFIG_HOTPLUG_CPU
-static bool migrate_one_irq(struct irq_desc *desc)
-{
-       struct irq_data *d = irq_desc_get_irq_data(desc);
-       const struct cpumask *affinity = irq_data_get_affinity_mask(d);
-       struct irq_chip *c;
-       bool ret = false;
-
-       /*
-        * If this is a per-CPU interrupt, or the affinity does not
-        * include this CPU, then we have nothing to do.
-        */
-       if (irqd_is_per_cpu(d) || !cpumask_test_cpu(smp_processor_id(), 
affinity))
-               return false;
-
-       if (cpumask_any_and(affinity, cpu_online_mask) >= nr_cpu_ids) {
-               affinity = cpu_online_mask;
-               ret = true;
-       }
-
-       c = irq_data_get_irq_chip(d);
-       if (!c->irq_set_affinity)
-               pr_debug("IRQ%u: unable to set affinity\n", d->irq);
-       else if (c->irq_set_affinity(d, affinity, false) == 
IRQ_SET_MASK_OK && ret)
-               cpumask_copy(irq_data_get_affinity_mask(d), affinity);
-
-       return ret;
-}
-
-/*
- * The current CPU has been marked offline.  Migrate IRQs off this CPU.
- * If the affinity settings do not allow other CPUs, force them onto any
- * available CPU.
- *
- * Note: we must iterate over all IRQs, whether they have an attached
- * action structure or not, as we need to get chained interrupts too.
- */
-void migrate_irqs(void)
-{
-       unsigned int i;
-       struct irq_desc *desc;
-       unsigned long flags;
-
-       local_irq_save(flags);
-
-       for_each_irq_desc(i, desc) {
-               bool affinity_broken;
-
-               raw_spin_lock(&desc->lock);
-               affinity_broken = migrate_one_irq(desc);
-               raw_spin_unlock(&desc->lock);
-
-               if (affinity_broken)
-                       pr_warn_ratelimited("IRQ%u no longer affine to 
CPU%u\n",
-                               i, smp_processor_id());
-       }
-
-       local_irq_restore(flags);
-}
-#endif /* CONFIG_HOTPLUG_CPU */
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 3bf82232b1be..1d6f5ea522f4 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -254,7 +254,7 @@ int __cpu_disable(void)
         /*
          * OK - migrate IRQs away from this CPU
          */
-       migrate_irqs();
+       irq_migrate_all_off_this_cpu();

         /*
          * Flush user cache and TLB mappings, and then remove this CPU

Re: [PATCH] ARM: irq: Add IRQ_SET_MASK_OK_DONE handling in migrate_one_irq()

[Marc Zyngier]

On 09/01/2019 15:47, Dietmar Eggemann wrote:
> Hi Marc,
> 
> On 1/8/19 3:16 PM, Marc Zyngier wrote:
>> Hi Dietmar,
>>
>> On 08/01/2019 13:58, Dietmar Eggemann wrote:
>>> Arm TC2 (multi_v7_defconfig plus CONFIG_ARM_BIG_LITTLE_CPUFREQ=y and
>>> CONFIG_ARM_VEXPRESS_SPC_CPUFREQ=y) fails hotplug stress tests.
>>>
>>> This issue was tracked down to a missing copy of the new affinity
>>> cpumask of the vexpress-spc interrupt into struct
>>> irq_common_data.affinity when the interrupt is migrated in
>>> migrate_one_irq().
>>>
>>> Commit 0407daceedfe ("irqchip/gic: Return IRQ_SET_MASK_OK_DONE in the
>>> set_affinity method") changed the return value of the irq_set_affinity()
>>> function of the GIC from IRQ_SET_MASK_OK to IRQ_SET_MASK_OK_DONE.
>>>
>>> In migrate_one_irq() if the current irq affinity mask and the cpu
>>> online mask do not share any CPU, the affinity mask is set to the cpu
>>> online mask. In this case (ret == true) and when the irq chip
>>> function irq_set_affinity() returns successfully (IRQ_SET_MASK_OK),
>>> struct irq_common_data.affinity should also be updated.
>>>
>>> Add IRQ_SET_MASK_OK_DONE next to IRQ_SET_MASK_OK when checking that the
>>> irq chip function irq_set_affinity() returns successfully.
>>>
>>> Commit 2cb625478f8c ("genirq: Add IRQ_SET_MASK_OK_DONE to support
>>> stacked irqchip") only added IRQ_SET_MASK_OK_DONE handling to
>>> irq_do_set_affinity() in the irq core and not to the Arm32 irq code.
>>>
>>> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
>>> ---
>>>
>>> The hotplug issue on Arm TC2 happens because the vexpress-spc interrupt
>>> (irq=22) is affine to CPU0. This occurs since it is setup early when the
>>> cpu_online_mask is still 0.
>>> But the problem with the missing copy of the affinity mask should occur
>>> with every interrupt which is forced to migrate.
>>>
>>> With additional debug in irq_setup_affinity():
>>>
>>> [0.000619] irq_setup_affinity(): irq=17 mask=0 cpu_online_mask=0 set=0-4
>>> [0.007065] irq_setup_affinity(): irq=22 mask=0 cpu_online_mask=0 set=0-4
>>> [3.372907] irq_setup_affinity(): irq=47 mask=0-4 cpu_online_mask=0-4
>>> set=0-4
>>>
>>> cat /proc/interrupts
>>>             CPU0       CPU1       CPU2       CPU3       CPU4
>>> 22:        316          0          0          0          0     GIC-0 127
>>> Level     vexpress-spc
>>>
>>> cat /proc/irq/22/smp_affinity_list
>>> 0
> 
> [...]
> 
>>
>> On the arm64 side, we've solved the exact same issue by getting rid of
>> this code and using the generic implementation. See 217d453d473c5
>> ("arm64: fix a migrating irq bug when hotplug cpu"), which uses
>> irq_migrate_all_off_this_cpu instead.
>>
>> I'm not sure there is much value in not using the core code in this case.
> 
> Thanks for the hint! Much more elegant! I tried the following on TC2 and 
> it worked just fine. I'm not aware on any drawbacks of using the generic 
> irq migration for Arm32 as well.

[...]

Sounds great! Can you put it in a proper patch and resend it?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH] ARM: irq: Add IRQ_SET_MASK_OK_DONE handling in migrate_one_irq()

[Dietmar Eggemann]

On 1/9/19 5:21 PM, Marc Zyngier wrote:
> On 09/01/2019 15:47, Dietmar Eggemann wrote:
>> Hi Marc,
>>
>> On 1/8/19 3:16 PM, Marc Zyngier wrote:
>>> Hi Dietmar,
>>>
>>> On 08/01/2019 13:58, Dietmar Eggemann wrote:

[...]

>>> On the arm64 side, we've solved the exact same issue by getting rid of
>>> this code and using the generic implementation. See 217d453d473c5
>>> ("arm64: fix a migrating irq bug when hotplug cpu"), which uses
>>> irq_migrate_all_off_this_cpu instead.
>>>
>>> I'm not sure there is much value in not using the core code in this case.
>>
>> Thanks for the hint! Much more elegant! I tried the following on TC2 and
>> it worked just fine. I'm not aware on any drawbacks of using the generic
>> irq migration for Arm32 as well.
> 
> [...]
> 
> Sounds great! Can you put it in a proper patch and resend it?

Yes. I renamed the patch to "arm: fix a migrating irq bug when hotplug 
cpu" so it's closer to its arm64 counterpart patch.

https://lore.kernel.org/lkml/20190110100922.20280-1-dietmar.eggemann@arm.com/