linux-kernel - [PATCH v2 21/22] genirq: Switch to irq_get_nr

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Message-ID: <20241008202601.3737326-22-bvanassche@acm.org>
Date: Tue,  8 Oct 2024 13:26:00 -0700
From: Bart Van Assche <bvanassche@....org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Russell King <linux@...linux.org.uk>,
	linux-kernel@...r.kernel.org,
	Bart Van Assche <bvanassche@....org>
Subject: [PATCH v2 21/22] genirq: Switch to irq_get_nr_irqs()

Use the irq_get_nr_irqs() function instead of the global variable
'nr_irqs'. Cache the result of this function in a local variable in
order not to rely on CSE (common subexpression elimination). This patch
prepares for changing 'nr_irqs' from an exported global variable into a
variable with file scope.

Signed-off-by: Bart Van Assche <bvanassche@....org>
---
 include/linux/irqnr.h  | 33 +++++++++++++++++++--------------
 kernel/irq/irqdomain.c |  2 +-
 kernel/irq/proc.c      |  3 ++-
 3 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/include/linux/irqnr.h b/include/linux/irqnr.h
index 7419b807b71b..a33088d27c54 100644
--- a/include/linux/irqnr.h
+++ b/include/linux/irqnr.h
@@ -11,26 +11,31 @@ unsigned int irq_set_nr_irqs(unsigned int nr);
 extern struct irq_desc *irq_to_desc(unsigned int irq);
 unsigned int irq_get_next_irq(unsigned int offset);
 
-# define for_each_irq_desc(irq, desc)					\
-	for (irq = 0, desc = irq_to_desc(irq); irq < nr_irqs;		\
-	     irq++, desc = irq_to_desc(irq))				\
-		if (!desc)						\
-			;						\
-		else
-
+#define for_each_irq_desc(irq, desc)                                      \
+	for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__;   \
+	     __nr_irqs__ = 0)                                             \
+		for (irq = 0, desc = irq_to_desc(irq); irq < __nr_irqs__; \
+		     irq++, desc = irq_to_desc(irq))                      \
+			if (!desc)                                        \
+				;                                         \
+			else
 
 # define for_each_irq_desc_reverse(irq, desc)				\
-	for (irq = nr_irqs - 1, desc = irq_to_desc(irq); irq >= 0;	\
-	     irq--, desc = irq_to_desc(irq))				\
+	for (irq = irq_get_nr_irqs() - 1, desc = irq_to_desc(irq);	\
+	     irq >= 0; irq--, desc = irq_to_desc(irq))			\
 		if (!desc)						\
 			;						\
 		else
 
-# define for_each_active_irq(irq)			\
-	for (irq = irq_get_next_irq(0); irq < nr_irqs;	\
-	     irq = irq_get_next_irq(irq + 1))
+#define for_each_active_irq(irq)                                        \
+	for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__; \
+	     __nr_irqs__ = 0)                                           \
+		for (irq = irq_get_next_irq(0); irq < __nr_irqs__;      \
+		     irq = irq_get_next_irq(irq + 1))
 
-#define for_each_irq_nr(irq)                   \
-       for (irq = 0; irq < nr_irqs; irq++)
+#define for_each_irq_nr(irq)                                            \
+	for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__; \
+	     __nr_irqs__ = 0)                                           \
+		for (irq = 0; irq < __nr_irqs__; irq++)
 
 #endif
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index e0bff21f30e0..ec6d8e72d980 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -1225,7 +1225,7 @@ int irq_domain_alloc_descs(int virq, unsigned int cnt, irq_hw_number_t hwirq,
 		virq = __irq_alloc_descs(virq, virq, cnt, node, THIS_MODULE,
 					 affinity);
 	} else {
-		hint = hwirq % nr_irqs;
+		hint = hwirq % irq_get_nr_irqs();
 		if (hint == 0)
 			hint++;
 		virq = __irq_alloc_descs(-1, hint, cnt, node, THIS_MODULE,
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 9081ada81c3d..d226282c5b66 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -457,11 +457,12 @@ int __weak arch_show_interrupts(struct seq_file *p, int prec)
 }
 
 #ifndef ACTUAL_NR_IRQS
-# define ACTUAL_NR_IRQS nr_irqs
+# define ACTUAL_NR_IRQS irq_get_nr_irqs()
 #endif
 
 int show_interrupts(struct seq_file *p, void *v)
 {
+	const unsigned int nr_irqs = irq_get_nr_irqs();
 	static int prec;
 
 	int i = *(loff_t *) v, j;