linux-kernel - [PATCH 2/7] powerpc/irq: arch_irq_stat

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Date:   Sat, 11 Sep 2021 12:48:03 +0900
From:   Alexei Lozovsky <me@...mmy.net>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Alexey Dobriyan <adobriyan@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org
Subject: [PATCH 2/7] powerpc/irq: arch_irq_stat_cpu() returns unsigned int

The interrupt counters this function sums up are all unsigned int
(see irq_cpustat_t). If the sum overflows, so be it: you should
monitor the counter and take note when it wraps around.

Summing up unsigned int values into u64 does not "handle" overflows,
but if any of the individual counters overflows then the computed
sum is inaccurate.

Signed-off-by: Alexei Lozovsky <me@...mmy.net>
---
 arch/powerpc/include/asm/hardirq.h | 2 +-
 arch/powerpc/kernel/irq.c          | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/hardirq.h b/arch/powerpc/include/asm/hardirq.h
index f133b5930ae1..5248adcb50b4 100644
--- a/arch/powerpc/include/asm/hardirq.h
+++ b/arch/powerpc/include/asm/hardirq.h
@@ -32,7 +32,7 @@ static inline void ack_bad_irq(unsigned int irq)
 	printk(KERN_CRIT "unexpected IRQ trap at vector %02x\n", irq);
 }
 
-extern u64 arch_irq_stat_cpu(unsigned int cpu);
+extern unsigned int arch_irq_stat_cpu(unsigned int cpu);
 #define arch_irq_stat_cpu	arch_irq_stat_cpu
 
 #endif /* _ASM_POWERPC_HARDIRQ_H */
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 551b653228c4..a100c967892e 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -645,9 +645,9 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 /*
  * /proc/stat helpers
  */
-u64 arch_irq_stat_cpu(unsigned int cpu)
+unsigned int arch_irq_stat_cpu(unsigned int cpu)
 {
-	u64 sum = per_cpu(irq_stat, cpu).timer_irqs_event;
+	unsigned int sum = per_cpu(irq_stat, cpu).timer_irqs_event;
 
 	sum += per_cpu(irq_stat, cpu).broadcast_irqs_event;
 	sum += per_cpu(irq_stat, cpu).pmu_irqs;
-- 
2.25.1