linux-kernel - [PATCH v2 2/2] genirq/proc: Refine percpu kstat

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Date: Wed, 15 May 2024 18:06:32 +0800
From: Adrian Huang <adrianhuang0701@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Adrian Huang <ahuang12@...ovo.com>,
	Jiwei Sun <sunjw10@...ovo.com>
Subject: [PATCH v2 2/2] genirq/proc: Refine percpu kstat_irqs access logic

From: Adrian Huang <ahuang12@...ovo.com>

Interrupts which have no action and chained interrupts can be
ignored due to the following reasons (as per tglx's comment):

  1) Interrupts which have no action are completely uninteresting as
     there is no real information attached.

  2) Chained interrupts do not have a count at all.

Refine the condition statement, and convert the access of kstat_irqs
into the unconditional statement.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/lkml/87h6f0knau.ffs@tglx/
Tested-by: Jiwei Sun <sunjw10@...ovo.com>
Signed-off-by: Adrian Huang <ahuang12@...ovo.com>
---
 kernel/irq/proc.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 623b8136e9af..e3d03103522c 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -461,10 +461,10 @@ int show_interrupts(struct seq_file *p, void *v)
 {
 	static int prec;
 
-	unsigned long flags, any_count = 0;
 	int i = *(loff_t *) v, j;
 	struct irqaction *action;
 	struct irq_desc *desc;
+	unsigned long flags;
 
 	if (i > ACTUAL_NR_IRQS)
 		return 0;
@@ -488,18 +488,12 @@ 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)) && !any_count)
+	if (!desc->action || irq_desc_is_chained(desc) || !desc->kstat_irqs)
 		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 ", *per_cpu_ptr(desc->kstat_irqs, j));
 
 	raw_spin_lock_irqsave(&desc->lock, flags);
 	if (desc->irq_data.chip) {
-- 
2.25.1