linux-kernel - [PATCH 3/7] x86/irq: arch_irq_stat

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Date:   Sat, 11 Sep 2021 12:48:04 +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 3/7] x86/irq: arch_irq_stat_cpu() returns unsigned int

Like with PowerPC's version, on x86 the interrupt counters that are
added here are all unsigned int too (see irq_cpustat_t for x86)
as well as mce_exception_count and mce_poll_count.

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/x86/include/asm/hardirq.h | 2 +-
 arch/x86/kernel/irq.c          | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index 275e7fd20310..461536b45391 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -54,7 +54,7 @@ DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
 
 extern void ack_bad_irq(unsigned int 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
 
 extern u64 arch_irq_stat(void);
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index e28f6a5d14f1..cefe1bc9f42c 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -188,9 +188,9 @@ 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 = irq_stats(cpu)->__nmi_count;
+	unsigned int sum = irq_stats(cpu)->__nmi_count;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 	sum += irq_stats(cpu)->apic_timer_irqs;
-- 
2.25.1