LinuxLists.cc - [PATCH] genirq: update irq stats from NMI handlers

2019-07-04 04:24:50

Subject: [PATCH] genirq: update irq stats from NMI handlers

2019-07-04 07:15:00

Subject: Re: [PATCH] genirq: update irq stats from NMI handlers

Hi Shijith,

On 04/07/2019 05:22, Shijith Thotton wrote:
> The NMI handlers handle_percpu_devid_fasteoi_nmi() and
> handle_fasteoi_nmi() added by commit 2dcf1fbcad35 ("genirq: Provide NMI
> handlers") do not update the interrupt counts. Due to that the NMI
> interrupt count does not show up correctly in /proc/interrupts.
>
> Update the functions to fix this. With this change, we can see stats of
> the perf NMI interrupts on arm64.
>
> Fixes: 2dcf1fbcad35 ("genirq: Provide NMI handlers")
>
> Signed-off-by: Shijith Thotton <[email protected]>
> ---
> kernel/irq/chip.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> index 29d6c7d070b4..88d1e054c6ea 100644
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -748,6 +748,8 @@ void handle_fasteoi_nmi(struct irq_desc *desc)
> unsigned int irq = irq_desc_get_irq(desc);
> irqreturn_t res;
>
> + kstat_incr_irqs_this_cpu(desc);
> +

This needs to be called with the desc lock taken, otherwise we're likely
to corrupt desc->tot_count.
But taking the desc lock is something we can't do in NMI context (
*spin_lock_irq*() won't prevent an NMI from happening).

> trace_irq_handler_entry(irq, action);
> /*
> * NMIs cannot be shared, there is only one action.
> @@ -962,6 +964,8 @@ void handle_percpu_devid_fasteoi_nmi(struct irq_desc *desc)
> unsigned int irq = irq_desc_get_irq(desc);
> irqreturn_t res;
>
> + __kstat_incr_irqs_this_cpu(desc);
> +

Looking at handle_percpu_irq(), I think this might be acceptable. But
does it make sense to only have kstats for percpu NMIs?

Cheers,

--
Julien Thierry

2019-07-04 10:39:31

by Shijith Thotton

[permalink] [raw]

Subject: Re: [PATCH] genirq: update irq stats from NMI handlers

Hi Julien,

On 7/4/19 12:13 AM, Julien Thierry wrote:
> On 04/07/2019 05:22, Shijith Thotton wrote:
>> The NMI handlers handle_percpu_devid_fasteoi_nmi() and
>> handle_fasteoi_nmi() added by commit 2dcf1fbcad35 ("genirq: Provide NMI
>> handlers") do not update the interrupt counts. Due to that the NMI
>> interrupt count does not show up correctly in /proc/interrupts.
>>
>> Update the functions to fix this. With this change, we can see stats of
>> the perf NMI interrupts on arm64.
>>
>> Fixes: 2dcf1fbcad35 ("genirq: Provide NMI handlers")
>>
>> Signed-off-by: Shijith Thotton <[email protected]>
>> ---
>> kernel/irq/chip.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
>> index 29d6c7d070b4..88d1e054c6ea 100644
>> --- a/kernel/irq/chip.c
>> +++ b/kernel/irq/chip.c
>> @@ -748,6 +748,8 @@ void handle_fasteoi_nmi(struct irq_desc *desc)
>> unsigned int irq = irq_desc_get_irq(desc);
>> irqreturn_t res;
>>
>> + kstat_incr_irqs_this_cpu(desc);
>> +
>
> This needs to be called with the desc lock taken, otherwise we're likely
> to corrupt desc->tot_count.
> But taking the desc lock is something we can't do in NMI context (
> *spin_lock_irq*() won't prevent an NMI from happening).
>
>> trace_irq_handler_entry(irq, action);
>> /*
>> * NMIs cannot be shared, there is only one action.
>> @@ -962,6 +964,8 @@ void handle_percpu_devid_fasteoi_nmi(struct irq_desc *desc)
>> unsigned int irq = irq_desc_get_irq(desc);
>> irqreturn_t res;
>>
>> + __kstat_incr_irqs_this_cpu(desc);
>> +
>
> Looking at handle_percpu_irq(), I think this might be acceptable. But
> does it make sense to only have kstats for percpu NMIs?
>

It would be better to have stats for both.

handle_fasteoi_nmi() can use __kstat_incr_irqs_this_cpu() if below
change can be added to kstat_irqs_cpu().

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index a92b33593b8d..9484e88dabc2 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -950,6 +950,11 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
*per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
}

+static bool irq_is_nmi(struct irq_desc *desc)
+{
+ return desc->istate & IRQS_NMI;
+}
+
/**
* kstat_irqs - Get the statistics for an interrupt
* @irq: The interrupt number
@@ -967,7 +972,8 @@ unsigned int kstat_irqs(unsigned int irq)
if (!desc || !desc->kstat_irqs)
return 0;
if (!irq_settings_is_per_cpu_devid(desc) &&
- !irq_settings_is_per_cpu(desc))
+ !irq_settings_is_per_cpu(desc) &&
+ !irq_is_nmi(desc))
return desc->tot_count;

for_each_possible_cpu(cpu)

Thomas,
Please suggest a better way if any.

Thanks,
Shijith

2019-07-04 16:35:21

by Shijith Thotton

[permalink] [raw]

Subject: Re: [PATCH] genirq: update irq stats from NMI handlers

On 7/4/19 9:19 AM, Thomas Gleixner wrote:
> On Thu, 4 Jul 2019, Shijith Thotton wrote:
>> On 7/4/19 12:13 AM, Julien Thierry wrote:
>>> Looking at handle_percpu_irq(), I think this might be acceptable. But
>>> does it make sense to only have kstats for percpu NMIs?
>>>
>>
>> It would be better to have stats for both.
>>
>> handle_fasteoi_nmi() can use __kstat_incr_irqs_this_cpu() if below
>> change can be added to kstat_irqs_cpu().
>>
>> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
>> index a92b33593b8d..9484e88dabc2 100644
>> --- a/kernel/irq/irqdesc.c
>> +++ b/kernel/irq/irqdesc.c
>> @@ -950,6 +950,11 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
>> *per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
>> }
>>
>> +static bool irq_is_nmi(struct irq_desc *desc)
>> +{
>> + return desc->istate & IRQS_NMI;
>> +}
>> +
>> /**
>> * kstat_irqs - Get the statistics for an interrupt
>> * @irq: The interrupt number
>> @@ -967,7 +972,8 @@ unsigned int kstat_irqs(unsigned int irq)
>> if (!desc || !desc->kstat_irqs)
>> return 0;
>> if (!irq_settings_is_per_cpu_devid(desc) &&
>> - !irq_settings_is_per_cpu(desc))
>> + !irq_settings_is_per_cpu(desc) &&
>> + !irq_is_nmi(desc))
>> return desc->tot_count;
>>
>> for_each_possible_cpu(cpu)
>>
>>
>> Thomas,
>> Please suggest a better way if any.
>
> Looks good.
>

Thanks Thomas. Will share v2 with the changes.

Thanks,
Shijith

2019-07-04 17:04:59

by Thomas Gleixner

[permalink] [raw]

Subject: Re: [PATCH] genirq: update irq stats from NMI handlers

On Thu, 4 Jul 2019, Shijith Thotton wrote:
> On 7/4/19 12:13 AM, Julien Thierry wrote:
> > Looking at handle_percpu_irq(), I think this might be acceptable. But
> > does it make sense to only have kstats for percpu NMIs?
> >
>
> It would be better to have stats for both.
>
> handle_fasteoi_nmi() can use __kstat_incr_irqs_this_cpu() if below
> change can be added to kstat_irqs_cpu().
>
> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
> index a92b33593b8d..9484e88dabc2 100644
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -950,6 +950,11 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
> *per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
> }
>
> +static bool irq_is_nmi(struct irq_desc *desc)
> +{
> + return desc->istate & IRQS_NMI;
> +}
> +
> /**
> * kstat_irqs - Get the statistics for an interrupt
> * @irq: The interrupt number
> @@ -967,7 +972,8 @@ unsigned int kstat_irqs(unsigned int irq)
> if (!desc || !desc->kstat_irqs)
> return 0;
> if (!irq_settings_is_per_cpu_devid(desc) &&
> - !irq_settings_is_per_cpu(desc))
> + !irq_settings_is_per_cpu(desc) &&
> + !irq_is_nmi(desc))
> return desc->tot_count;
>
> for_each_possible_cpu(cpu)
>
>
> Thomas,
> Please suggest a better way if any.

Looks good.

Thanks,

tglx

2019-07-05 08:49:45

by Shijith Thotton

[permalink] [raw]

Subject: [PATCH v2] genirq: update irq stats from NMI handlers

The NMI handlers handle_percpu_devid_fasteoi_nmi() and
handle_fasteoi_nmi() added by commit 2dcf1fbcad35 ("genirq: Provide NMI
handlers") do not update the interrupt counts. Due to that the NMI
interrupt count does not show up correctly in /proc/interrupts.

Update the functions to fix this. With this change, we can see stats of
the perf NMI interrupts on arm64.

As NMI handlers can't update tot_count in irq descriptor, kstat_irqs()
has been updated not to return tot_count for NMI.

Fixes: 2dcf1fbcad35 ("genirq: Provide NMI handlers")

Signed-off-by: Shijith Thotton <[email protected]>
---
Changes since v1:
- Don't touch tot_count from NMI handler.
- Update kstat_irqs() to not return tot_count for NMI.

kernel/irq/chip.c | 4 ++++
kernel/irq/irqdesc.c | 8 +++++++-
2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 29d6c7d070b4..04c850fb70cb 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -748,6 +748,8 @@ void handle_fasteoi_nmi(struct irq_desc *desc)
unsigned int irq = irq_desc_get_irq(desc);
irqreturn_t res;

+ __kstat_incr_irqs_this_cpu(desc);
+
trace_irq_handler_entry(irq, action);
/*
* NMIs cannot be shared, there is only one action.
@@ -962,6 +964,8 @@ void handle_percpu_devid_fasteoi_nmi(struct irq_desc *desc)
unsigned int irq = irq_desc_get_irq(desc);
irqreturn_t res;

+ __kstat_incr_irqs_this_cpu(desc);
+
trace_irq_handler_entry(irq, action);
res = action->handler(irq, raw_cpu_ptr(action->percpu_dev_id));
trace_irq_handler_exit(irq, action, res);
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index c52b737ab8e3..9149dde5a7b0 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -946,6 +946,11 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
*per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
}

+static bool irq_is_nmi(struct irq_desc *desc)
+{
+ return desc->istate & IRQS_NMI;
+}
+
/**
* kstat_irqs - Get the statistics for an interrupt
* @irq: The interrupt number
@@ -963,7 +968,8 @@ unsigned int kstat_irqs(unsigned int irq)
if (!desc || !desc->kstat_irqs)
return 0;
if (!irq_settings_is_per_cpu_devid(desc) &&
- !irq_settings_is_per_cpu(desc))
+ !irq_settings_is_per_cpu(desc) &&
+ !irq_is_nmi(desc))
return desc->tot_count;

for_each_possible_cpu(cpu)
--
2.17.0

2019-07-06 08:45:13

by tip-bot for Vasyl Gomonovych

[permalink] [raw]

Subject: [tip:irq/core] genirq: Update irq stats from NMI handlers

Commit-ID: c09cb1293523dd786ae54a12fd88001542cba2f6
Gitweb: https://git.kernel.org/tip/c09cb1293523dd786ae54a12fd88001542cba2f6
Author: Shijith Thotton <[email protected]>
AuthorDate: Fri, 5 Jul 2019 07:56:20 +0000
Committer: Thomas Gleixner <[email protected]>
CommitDate: Sat, 6 Jul 2019 10:40:19 +0200

genirq: Update irq stats from NMI handlers

The NMI handlers handle_percpu_devid_fasteoi_nmi() and handle_fasteoi_nmi()
do not update the interrupt counts. Due to that the NMI interrupt count
does not show up correctly in /proc/interrupts.

Add the statistics and treat the NMI handlers in the same way as per cpu
interrupts and prevent them from updating irq_desc::tot_count as this might
be corrupted due to concurrency.

[ tglx: Massaged changelog ]

Fixes: 2dcf1fbcad35 ("genirq: Provide NMI handlers")
Signed-off-by: Shijith Thotton <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
kernel/irq/chip.c | 4 ++++
kernel/irq/irqdesc.c | 8 +++++++-
2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 29d6c7d070b4..04c850fb70cb 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -748,6 +748,8 @@ void handle_fasteoi_nmi(struct irq_desc *desc)
unsigned int irq = irq_desc_get_irq(desc);
irqreturn_t res;

+ __kstat_incr_irqs_this_cpu(desc);
+
trace_irq_handler_entry(irq, action);
/*
* NMIs cannot be shared, there is only one action.
@@ -962,6 +964,8 @@ void handle_percpu_devid_fasteoi_nmi(struct irq_desc *desc)
unsigned int irq = irq_desc_get_irq(desc);
irqreturn_t res;

+ __kstat_incr_irqs_this_cpu(desc);
+
trace_irq_handler_entry(irq, action);
res = action->handler(irq, raw_cpu_ptr(action->percpu_dev_id));
trace_irq_handler_exit(irq, action, res);
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index c52b737ab8e3..9149dde5a7b0 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -946,6 +946,11 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
*per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
}

+static bool irq_is_nmi(struct irq_desc *desc)
+{
+ return desc->istate & IRQS_NMI;
+}
+
/**
* kstat_irqs - Get the statistics for an interrupt
* @irq: The interrupt number
@@ -963,7 +968,8 @@ unsigned int kstat_irqs(unsigned int irq)
if (!desc || !desc->kstat_irqs)
return 0;
if (!irq_settings_is_per_cpu_devid(desc) &&
- !irq_settings_is_per_cpu(desc))
+ !irq_settings_is_per_cpu(desc) &&
+ !irq_is_nmi(desc))
return desc->tot_count;

for_each_possible_cpu(cpu)