linux-kernel - [PATCH v2 03/12] powerpc/irq: Use READ

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Date:   Thu, 16 Sep 2021 02:58:39 +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 v2 03/12] powerpc/irq: Use READ_ONCE for IRQ counter reads

Just like with generic IRQ counters in the previous commit,
wrap accesses to per-CPU counters from irq_cpustat_t in READ_ONCE.
Grab that one "hmi_irqs" oddball from struct paca_struct as well.
These memory loads should not be torn, let's make it explicit.

Signed-off-by: Alexei Lozovsky <me@...mmy.net>
---
 arch/powerpc/kernel/irq.c | 40 +++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 551b653228c4..e5082d8be700 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -581,52 +581,52 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 
 	seq_printf(p, "%*s: ", prec, "LOC");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat, j).timer_irqs_event);
+		seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).timer_irqs_event));
         seq_printf(p, "  Local timer interrupts for timer event device\n");
 
 	seq_printf(p, "%*s: ", prec, "BCT");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat, j).broadcast_irqs_event);
+		seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).broadcast_irqs_event));
 	seq_printf(p, "  Broadcast timer interrupts for timer event device\n");
 
 	seq_printf(p, "%*s: ", prec, "LOC");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat, j).timer_irqs_others);
+		seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).timer_irqs_others));
         seq_printf(p, "  Local timer interrupts for others\n");
 
 	seq_printf(p, "%*s: ", prec, "SPU");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat, j).spurious_irqs);
+		seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).spurious_irqs));
 	seq_printf(p, "  Spurious interrupts\n");
 
 	seq_printf(p, "%*s: ", prec, "PMI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat, j).pmu_irqs);
+		seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).pmu_irqs));
 	seq_printf(p, "  Performance monitoring interrupts\n");
 
 	seq_printf(p, "%*s: ", prec, "MCE");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat, j).mce_exceptions);
+		seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).mce_exceptions));
 	seq_printf(p, "  Machine check exceptions\n");
 
 #ifdef CONFIG_PPC_BOOK3S_64
 	if (cpu_has_feature(CPU_FTR_HVMODE)) {
 		seq_printf(p, "%*s: ", prec, "HMI");
 		for_each_online_cpu(j)
-			seq_printf(p, "%10u ", paca_ptrs[j]->hmi_irqs);
+			seq_printf(p, "%10u ", READ_ONCE(paca_ptrs[j]->hmi_irqs));
 		seq_printf(p, "  Hypervisor Maintenance Interrupts\n");
 	}
 #endif
 
 	seq_printf(p, "%*s: ", prec, "NMI");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat, j).sreset_irqs);
+		seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).sreset_irqs));
 	seq_printf(p, "  System Reset interrupts\n");
 
 #ifdef CONFIG_PPC_WATCHDOG
 	seq_printf(p, "%*s: ", prec, "WDG");
 	for_each_online_cpu(j)
-		seq_printf(p, "%10u ", per_cpu(irq_stat, j).soft_nmi_irqs);
+		seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).soft_nmi_irqs));
 	seq_printf(p, "  Watchdog soft-NMI interrupts\n");
 #endif
 
@@ -634,7 +634,7 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	if (cpu_has_feature(CPU_FTR_DBELL)) {
 		seq_printf(p, "%*s: ", prec, "DBL");
 		for_each_online_cpu(j)
-			seq_printf(p, "%10u ", per_cpu(irq_stat, j).doorbell_irqs);
+			seq_printf(p, "%10u ", READ_ONCE(per_cpu(irq_stat, j).doorbell_irqs));
 		seq_printf(p, "  Doorbell interrupts\n");
 	}
 #endif
@@ -647,22 +647,22 @@ int arch_show_interrupts(struct seq_file *p, int prec)
  */
 u64 arch_irq_stat_cpu(unsigned int cpu)
 {
-	u64 sum = per_cpu(irq_stat, cpu).timer_irqs_event;
+	u64 sum = READ_ONCE(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;
-	sum += per_cpu(irq_stat, cpu).mce_exceptions;
-	sum += per_cpu(irq_stat, cpu).spurious_irqs;
-	sum += per_cpu(irq_stat, cpu).timer_irqs_others;
+	sum += READ_ONCE(per_cpu(irq_stat, cpu).broadcast_irqs_event);
+	sum += READ_ONCE(per_cpu(irq_stat, cpu).pmu_irqs);
+	sum += READ_ONCE(per_cpu(irq_stat, cpu).mce_exceptions);
+	sum += READ_ONCE(per_cpu(irq_stat, cpu).spurious_irqs);
+	sum += READ_ONCE(per_cpu(irq_stat, cpu).timer_irqs_others);
 #ifdef CONFIG_PPC_BOOK3S_64
-	sum += paca_ptrs[cpu]->hmi_irqs;
+	sum += READ_ONCE(paca_ptrs[cpu]->hmi_irqs);
 #endif
-	sum += per_cpu(irq_stat, cpu).sreset_irqs;
+	sum += READ_ONCE(per_cpu(irq_stat, cpu).sreset_irqs);
 #ifdef CONFIG_PPC_WATCHDOG
-	sum += per_cpu(irq_stat, cpu).soft_nmi_irqs;
+	sum += READ_ONCE(per_cpu(irq_stat, cpu).soft_nmi_irqs);
 #endif
 #ifdef CONFIG_PPC_DOORBELL
-	sum += per_cpu(irq_stat, cpu).doorbell_irqs;
+	sum += READ_ONCE(per_cpu(irq_stat, cpu).doorbell_irqs);
 #endif
 
 	return sum;
-- 
2.25.1