[PATCH 2/2] genirq/proc: Refine percpu kstat_irqs access logic

From: Adrian Huang
Date: Mon May 13 2024 - 08:07:09 EST


From: Adrian Huang <ahuang12@xxxxxxxxxx>

There is no need to accumulate all CPUs' kstat_irqs to determine whether
the corresponding irq should be printed. Instead, stop the iteration
once one of kstat_irqs is nonzero.

In addition, no need to check if kstat_irqs address is available
for each iteration when printing each CPU irq statistic.

Tested-by: Jiwei Sun <sunjw10@xxxxxxxxxx>
Signed-off-by: Adrian Huang <ahuang12@xxxxxxxxxx>
---
kernel/irq/proc.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 623b8136e9af..bfa341fac687 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -461,7 +461,7 @@ int show_interrupts(struct seq_file *p, void *v)
{
static int prec;

- unsigned long flags, any_count = 0;
+ unsigned long flags, print_irq = 1;
int i = *(loff_t *) v, j;
struct irqaction *action;
struct irq_desc *desc;
@@ -488,18 +488,28 @@ 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->action || irq_desc_is_chained(desc)) && desc->kstat_irqs) {
+ print_irq = 0;
+ for_each_online_cpu(j) {
+ if (data_race(*per_cpu_ptr(desc->kstat_irqs, j))) {
+ print_irq = 1;
+ break;
+ }
+ }
}

- if ((!desc->action || irq_desc_is_chained(desc)) && !any_count)
+ if (!print_irq)
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);
+
+ if (desc->kstat_irqs) {
+ for_each_online_cpu(j)
+ seq_printf(p, "%10u ", *per_cpu_ptr(desc->kstat_irqs, j));
+ } else {
+ for_each_online_cpu(j)
+ seq_printf(p, "%10u ", 0);
+ }

raw_spin_lock_irqsave(&desc->lock, flags);
if (desc->irq_data.chip) {
--
2.25.1