linux-kernel - [PATCH v3 3/4] genirq: Track the number of active IRQs

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Date:   Wed,  9 Jan 2019 14:20:47 -0500
From:   Waiman Long <longman@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Miklos Szeredi <miklos@...redi.hu>,
        Daniel Colascione <dancol@...gle.com>,
        Dave Chinner <david@...morbit.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v3 3/4] genirq: Track the number of active IRQs

A new atomic variable nr_active_irqs is added to track the number of
active IRQs that have one or more interrupts serviced.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 kernel/irq/internals.h | 7 +++++--
 kernel/irq/irqdesc.c   | 5 +++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 31787c1..239ae51 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -242,10 +242,13 @@ static inline void irq_state_set_masked(struct irq_desc *desc)
 
 #undef __irqd_to_state
 
+extern atomic_t nr_active_irqs;	/* # of active IRQs */
 static inline void kstat_incr_irqs_this_cpu(struct irq_desc *desc)
 {
-	if (unlikely(__this_cpu_inc_return(*desc->kstat_irqs) == 1))
-		atomic_inc(&desc->kstat_irq_cpus);
+	if (unlikely(__this_cpu_inc_return(*desc->kstat_irqs) == 1)) {
+		if (atomic_inc_return(&desc->kstat_irq_cpus) == 1)
+			atomic_inc(&nr_active_irqs);
+	}
 	__this_cpu_inc(kstat.irqs_sum);
 }
 
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 3d2c38b..7e00c4d 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -20,6 +20,11 @@
 #include "internals.h"
 
 /*
+ * Number of active IRQs
+ */
+atomic_t nr_active_irqs;
+
+/*
  * lockdep: we want to handle all irq_desc locks as a single lock-class:
  */
 static struct lock_class_key irq_desc_lock_class;
-- 
1.8.3.1