[patch V3 09/14] genirq: Cache the condition for /proc/interrupts exposure

[Thomas Gleixner]

show_interrupts() evaluates a boatload of conditions to establish whether
it should expose an interrupt in /proc/interrupts or not.

That can be simplified by caching the condition in an internal status flag,
which is updated when one of the relevant inputs changes.

The irq_desc::kstat_irq check is dropped because visible interrupt
descriptors always have a valid pointer.

As a result the number of instructions and branches for reading
/proc/interrupts is reduced significantly.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Reviewed-by: Dmitry Ilvokhin <d@xxxxxxxxxxxx>
---
V3: Remove the historical kstat_irq check - Radu
V2: s/IRQF_/IRQ/ and fixup the enum treatment - Dmitry
---
 include/linux/irq.h    |    1 +
 kernel/irq/chip.c      |    2 ++
 kernel/irq/internals.h |    2 ++
 kernel/irq/manage.c    |    2 ++
 kernel/irq/proc.c      |   15 +++++++++++----
 kernel/irq/settings.h  |   13 +++++++++++++
 6 files changed, 31 insertions(+), 4 deletions(-)

--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -99,6 +99,7 @@ enum {
 	IRQ_DISABLE_UNLAZY	= (1 << 19),
 	IRQ_HIDDEN		= (1 << 20),
 	IRQ_NO_DEBUG		= (1 << 21),
+	IRQ_RESERVED		= (1 << 22),
 };
 
 #define IRQF_MODIFY_MASK	\
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -1004,6 +1004,7 @@ static void
 		WARN_ON(irq_chip_pm_get(irq_desc_get_irq_data(desc)));
 		irq_activate_and_startup(desc, IRQ_RESEND);
 	}
+	irq_proc_update_valid(desc);
 }
 
 void __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
@@ -1064,6 +1065,7 @@ void irq_modify_status(unsigned int irq,
 			trigger = tmp;
 
 		irqd_set(&desc->irq_data, trigger);
+		irq_proc_update_valid(desc);
 	}
 }
 EXPORT_SYMBOL_GPL(irq_modify_status);
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -123,6 +123,7 @@ extern void register_irq_proc(unsigned i
 extern void unregister_irq_proc(unsigned int irq, struct irq_desc *desc);
 extern void register_handler_proc(unsigned int irq, struct irqaction *action);
 extern void unregister_handler_proc(unsigned int irq, struct irqaction *action);
+void irq_proc_update_valid(struct irq_desc *desc);
 #else
 static inline void register_irq_proc(unsigned int irq, struct irq_desc *desc) { }
 static inline void unregister_irq_proc(unsigned int irq, struct irq_desc *desc) { }
@@ -130,6 +131,7 @@ static inline void register_handler_proc
 					 struct irqaction *action) { }
 static inline void unregister_handler_proc(unsigned int irq,
 					   struct irqaction *action) { }
+static inline void irq_proc_update_valid(struct irq_desc *desc) { }
 #endif
 
 extern bool irq_can_set_affinity_usr(unsigned int irq);
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1802,6 +1802,7 @@ static int
 		__enable_irq(desc);
 	}
 
+	irq_proc_update_valid(desc);
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 	chip_bus_sync_unlock(desc);
 	mutex_unlock(&desc->request_mutex);
@@ -1906,6 +1907,7 @@ static struct irqaction *__free_irq(stru
 		desc->affinity_hint = NULL;
 #endif
 
+	irq_proc_update_valid(desc);
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 	/*
 	 * Drop bus_lock here so the changes which were done in the chip
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -439,6 +439,16 @@ void init_irq_proc(void)
 		register_irq_proc(irq, desc);
 }
 
+void irq_proc_update_valid(struct irq_desc *desc)
+{
+	u32 set = _IRQ_PROC_VALID;
+
+	if (irq_settings_is_hidden(desc) || irq_desc_is_chained(desc) || !desc->action)
+		set = 0;
+
+	irq_settings_update_proc_valid(desc, set);
+}
+
 #ifdef CONFIG_GENERIC_IRQ_SHOW
 
 int __weak arch_show_interrupts(struct seq_file *p, int prec)
@@ -514,10 +524,7 @@ int show_interrupts(struct seq_file *p,
 
 	guard(rcu)();
 	desc = irq_to_desc(i);
-	if (!desc || irq_settings_is_hidden(desc))
-		return 0;
-
-	if (!desc->action || irq_desc_is_chained(desc) || !desc->kstat_irqs)
+	if (!desc || !irq_settings_proc_valid(desc))
 		return 0;
 
 	seq_printf(p, "%*d:", prec, i);
--- a/kernel/irq/settings.h
+++ b/kernel/irq/settings.h
@@ -18,6 +18,7 @@ enum {
 	_IRQ_DISABLE_UNLAZY	= IRQ_DISABLE_UNLAZY,
 	_IRQ_HIDDEN		= IRQ_HIDDEN,
 	_IRQ_NO_DEBUG		= IRQ_NO_DEBUG,
+	_IRQ_PROC_VALID		= IRQ_RESERVED,
 	_IRQF_MODIFY_MASK	= IRQF_MODIFY_MASK,
 };
 
@@ -34,6 +35,7 @@ enum {
 #define IRQ_DISABLE_UNLAZY	GOT_YOU_MORON
 #define IRQ_HIDDEN		GOT_YOU_MORON
 #define IRQ_NO_DEBUG		GOT_YOU_MORON
+#define IRQ_RESERVED		GOT_YOU_MORON
 #undef IRQF_MODIFY_MASK
 #define IRQF_MODIFY_MASK	GOT_YOU_MORON
 
@@ -180,3 +182,14 @@ static inline bool irq_settings_no_debug
 {
 	return desc->status_use_accessors & _IRQ_NO_DEBUG;
 }
+
+static inline bool irq_settings_proc_valid(struct irq_desc *desc)
+{
+	return desc->status_use_accessors & _IRQ_PROC_VALID;
+}
+
+static inline void irq_settings_update_proc_valid(struct irq_desc *desc, u32 set)
+{
+	desc->status_use_accessors &= ~_IRQ_PROC_VALID;
+	desc->status_use_accessors |= (set & _IRQ_PROC_VALID);
+}