[PATCHv9 2/3] irq: use a struct for the kstat_irqs in the interrupt descriptor

Bitao Hu
2024-02-22T09:34:42Z

The current implementation uses an int for the kstat_irqs in the
interrupt descriptor.

However, we need to know the number of interrupts which happened
since softlockup detection took a snapshot in order to analyze
the problem caused by an interrupt storm.

Replacing an int with a struct and providing sensible interfaces
for the watchdog code can keep it self contained to the interrupt
core code.

Signed-off-by: Bitao Hu <yaoma@linux.alibaba.com>
---
arch/mips/dec/setup.c | 2 +-
arch/parisc/kernel/smp.c | 2 +-
arch/powerpc/kvm/book3s_hv_rm_xics.c | 2 +-
include/linux/irqdesc.h | 9 ++++++--
include/linux/kernel_stat.h | 3 +++
kernel/irq/internals.h | 2 +-
kernel/irq/irqdesc.c | 34 ++++++++++++++++++++++------
kernel/irq/proc.c | 9 +++-----
scripts/gdb/linux/interrupts.py | 6 ++---
9 files changed, 47 insertions(+), 22 deletions(-)

diff --git a/arch/mips/dec/setup.c b/arch/mips/dec/setup.c
index 6c3704f51d0d..87f0a1436bf9 100644
--- a/arch/mips/dec/setup.c
+++ b/arch/mips/dec/setup.c
@@ -756,7 +756,7 @@ void __init arch_init_irq(void)
NULL))
pr_err("Failed to register fpu interrupt\n");
desc_fpu = irq_to_desc(irq_fpu);
- fpu_kstat_irq = this_cpu_ptr(desc_fpu->kstat_irqs);
+ fpu_kstat_irq = this_cpu_ptr(&desc_fpu->kstat_irqs->cnt);
}
if (dec_interrupt[DEC_IRQ_CASCADE] >= 0) {
if (request_irq(dec_interrupt[DEC_IRQ_CASCADE], no_action,
diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index 444154271f23..800eb64e91ad 100644
--- a/arch/parisc/kernel/smp.c
+++ b/arch/parisc/kernel/smp.c
@@ -344,7 +344,7 @@ static int smp_boot_one_cpu(int cpuid, struct task_struct *idle)
struct irq_desc *desc = irq_to_desc(i);

if (desc && desc->kstat_irqs)
- *per_cpu_ptr(desc->kstat_irqs, cpuid) = 0;
+ *per_cpu_ptr(desc->kstat_irqs, cpuid) = (struct irqstat) { };
}
#endif

diff --git a/arch/powerpc/kvm/book3s_hv_rm_xics.c b/arch/powerpc/kvm/book3s_hv_rm_xics.c
index e42984878503..f2636414d82a 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_xics.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_xics.c
@@ -837,7 +837,7 @@ static inline void this_cpu_inc_rm(unsigned int __percpu *addr)
*/
static void kvmppc_rm_handle_irq_desc(struct irq_desc *desc)
{
- this_cpu_inc_rm(desc->kstat_irqs);
+ this_cpu_inc_rm(&desc->kstat_irqs->cnt);
__this_cpu_inc(kstat.irqs_sum);
}

diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index d9451d456a73..2912b1998670 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -17,6 +17,11 @@ struct irq_desc;
struct irq_domain;
struct pt_regs;

+struct irqstat {
+ unsigned int cnt;
+ unsigned int ref;
+};
+
/**
* struct irq_desc - interrupt descriptor
* @irq_common_data: per irq and chip data passed down to chip functions
@@ -55,7 +60,7 @@ struct pt_regs;
struct irq_desc {
struct irq_common_data irq_common_data;
struct irq_data irq_data;
- unsigned int __percpu *kstat_irqs;
+ struct irqstat __percpu *kstat_irqs;
irq_flow_handler_t handle_irq;
struct irqaction *action; /* IRQ action list */
unsigned int status_use_accessors;
@@ -119,7 +124,7 @@ extern struct irq_desc irq_desc[NR_IRQS];
static inline unsigned int irq_desc_kstat_cpu(struct irq_desc *desc,
unsigned int cpu)
{
- return desc->kstat_irqs ? *per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
+ return desc->kstat_irqs ? per_cpu(desc->kstat_irqs->cnt, cpu) : 0;
}

static inline struct irq_desc *irq_data_to_desc(struct irq_data *data)
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index 9935f7ecbfb9..98b3043ea5e6 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -79,6 +79,9 @@ static inline unsigned int kstat_cpu_softirqs_sum(int cpu)
return sum;
}

+extern void kstat_snapshot_irqs(void);
+extern unsigned int kstat_get_irq_since_snapshot(unsigned int irq);
+
/*
* Number of interrupts per specific IRQ source, since bootup
*/
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index bcc7f21db9ee..1d92532c2aae 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -258,7 +258,7 @@ static inline void irq_state_set_masked(struct irq_desc *desc)

static inline void __kstat_incr_irqs_this_cpu(struct irq_desc *desc)
{
- __this_cpu_inc(*desc->kstat_irqs);
+ __this_cpu_inc(desc->kstat_irqs->cnt);
__this_cpu_inc(kstat.irqs_sum);
}

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 27ca1c866f29..9cd17080b2d8 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -122,7 +122,7 @@ static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node,
desc->name = NULL;
desc->owner = owner;
for_each_possible_cpu(cpu)
- *per_cpu_ptr(desc->kstat_irqs, cpu) = 0;
+ *per_cpu_ptr(desc->kstat_irqs, cpu) = (struct irqstat) { };
desc_smp_init(desc, node, affinity);
}

@@ -418,8 +418,8 @@ static struct irq_desc *alloc_desc(int irq, int node, unsigned int flags,
desc = kzalloc_node(sizeof(*desc), GFP_KERNEL, node);
if (!desc)
return NULL;
- /* allocate based on nr_cpu_ids */
- desc->kstat_irqs = alloc_percpu(unsigned int);
+
+ desc->kstat_irqs = alloc_percpu(struct irqstat);
if (!desc->kstat_irqs)
goto err_desc;

@@ -593,7 +593,7 @@ int __init early_irq_init(void)
count = ARRAY_SIZE(irq_desc);

for (i = 0; i < count; i++) {
- desc[i].kstat_irqs = alloc_percpu(unsigned int);
+ desc[i].kstat_irqs = alloc_percpu(struct irqstat);
alloc_masks(&desc[i], node);
raw_spin_lock_init(&desc[i].lock);
lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
@@ -952,8 +952,7 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
{
struct irq_desc *desc = irq_to_desc(irq);

- return desc && desc->kstat_irqs ?
- *per_cpu_ptr(desc->kstat_irqs, cpu) : 0;
+ return desc && desc->kstat_irqs ? per_cpu(desc->kstat_irqs->cnt, cpu) : 0;
}

static bool irq_is_nmi(struct irq_desc *desc)
@@ -975,10 +974,31 @@ static unsigned int kstat_irqs(unsigned int irq)
return data_race(desc->tot_count);

for_each_possible_cpu(cpu)
- sum += data_race(*per_cpu_ptr(desc->kstat_irqs, cpu));
+ sum += data_race(per_cpu(desc->kstat_irqs->cnt, cpu));
return sum;
}

+void kstat_snapshot_irqs(void)
+{
+ struct irq_desc *desc;
+ unsigned int irq;
+
+ for_each_irq_desc(irq, desc) {
+ if (!desc->kstat_irqs)
+ continue;
+ this_cpu_write(desc->kstat_irqs->ref, this_cpu_read(desc->kstat_irqs->cnt));
+ }
+}
+
+unsigned int kstat_get_irq_since_snapshot(unsigned int irq)
+{
+ struct irq_desc *desc = irq_to_desc(irq);
+
+ if (!desc || !desc->kstat_irqs)
+ return 0;
+ return this_cpu_read(desc->kstat_irqs->cnt) - this_cpu_read(desc->kstat_irqs->ref);
+}
+
/**
* kstat_irqs_usr - Get the statistics for an interrupt from thread context
* @irq: The interrupt number
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 623b8136e9af..3ad40cf30c66 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -488,18 +488,15 @@ int show_interrupts(struct seq_file *p, void *v)
if (!desc || irq_settings_is_hidden(desc))
goto outsparse;

- if (desc->kstat_irqs) {
- for_each_online_cpu(j)
- any_count |= data_race(*per_cpu_ptr(desc->kstat_irqs, j));
- }
+ if (desc->kstat_irqs)
+ any_count = data_race(desc->tot_count);

if ((!desc->action || irq_desc_is_chained(desc)) && !any_count)
goto outsparse;

seq_printf(p, "%*d: ", prec, i);
for_each_online_cpu(j)
- seq_printf(p, "%10u ", desc->kstat_irqs ?
- *per_cpu_ptr(desc->kstat_irqs, j) : 0);
+ seq_printf(p, "%10u ", desc->kstat_irqs ? per_cpu(desc->kstat_irqs->cnt, j) : 0);

raw_spin_lock_irqsave(&desc->lock, flags);
if (desc->irq_data.chip) {
diff --git a/scripts/gdb/linux/interrupts.py b/scripts/gdb/linux/interrupts.py
index ef478e273791..7e50f3b9dfad 100644
--- a/scripts/gdb/linux/interrupts.py
+++ b/scripts/gdb/linux/interrupts.py
@@ -37,7 +37,7 @@ def show_irq_desc(prec, irq):
any_count = 0
if desc['kstat_irqs']:
for cpu in cpus.each_online_cpu():
- any_count += cpus.per_cpu(desc['kstat_irqs'], cpu)
+ any_count += cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt']

if (desc['action'] == 0 or irq_desc_is_chained(desc)) and any_count == 0:
return text;
@@ -45,7 +45,7 @@ def show_irq_desc(prec, irq):
text += "%*d: " % (prec, irq)
for cpu in cpus.each_online_cpu():
if desc['kstat_irqs']:
- count = cpus.per_cpu(desc['kstat_irqs'], cpu)
+ count = cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt']
else:
count = 0
text += "%10u" % (count)
@@ -177,7 +177,7 @@ def arm_common_show_interrupts(prec):
if desc == 0:
continue
for cpu in cpus.each_online_cpu():
- text += "%10u" % (cpus.per_cpu(desc['kstat_irqs'], cpu))
+ text += "%10u" % (cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt'])
text += " %s" % (ipi_types[ipi].string())
text += "\n"
return text
--
2.37.1 (Apple Git-137.1)