The following commit has been merged into the irq/core branch of tip:

Commit-ID:     4892e5e71ec9c942293cea7fd26e0c76179211ed
Gitweb:        https://git.kernel.org/tip/4892e5e71ec9c942293cea7fd26e0c76179211ed
Author:        Thomas Gleixner <tglx@kernel.org>
AuthorDate:    Sun, 17 May 2026 22:02:19 +02:00
Committer:     Thomas Gleixner <tglx@kernel.org>
CommitterDate: Tue, 26 May 2026 16:21:13 +02:00

genirq: Cache the condition for /proc/interrupts exposure

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@kernel.org>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Dmitry Ilvokhin <d@ilvokhin.com>
Reviewed-by: Radu Rendec <radu@rendec.net>
Link: https://patch.msgid.link/20260517194931.680943749@kernel.org
---
 include/linux/irq.h    |  1 +
 kernel/irq/chip.c      |  2 ++
 kernel/irq/internals.h |  2 ++
 kernel/irq/manage.c    |  8 +++++++-
 kernel/irq/proc.c      | 15 +++++++++++----
 kernel/irq/settings.h  | 13 +++++++++++++
 6 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index efa514e..f485369 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -103,6 +103,7 @@ enum {
 	IRQ_DISABLE_UNLAZY	= (1 << 19),
 	IRQ_HIDDEN		= (1 << 20),
 	IRQ_NO_DEBUG		= (1 << 21),
+	IRQ_RESERVED		= (1 << 22),
 };
 
 #define IRQF_MODIFY_MASK	\
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 6c9b1dc..2d283d1 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -1007,6 +1007,7 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
 		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,
@@ -1067,6 +1068,7 @@ void irq_modify_status(unsigned int irq, unsigned long clr, unsigned long set)
 			trigger = tmp;
 
 		irqd_set(&desc->irq_data, trigger);
+		irq_proc_update_valid(desc);
 	}
 }
 EXPORT_SYMBOL_GPL(irq_modify_status);
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index db359ac..e5f3d31 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -123,6 +123,7 @@ extern void register_irq_proc(unsigned int irq, struct irq_desc *desc);
 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(unsigned int irq,
 					 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);
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 8863b2d..7eb07e3 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1802,6 +1802,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		__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(struct irq_desc *desc, void *dev_id)
 		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
@@ -2047,6 +2049,8 @@ static const void *__cleanup_nmi(unsigned int irq, struct irq_desc *desc)
 		irq_shutdown_and_deactivate(desc);
 	}
 
+	irq_proc_update_valid(desc);
+
 	if (action)
 		unregister_handler_proc(irq, action);
 	kfree(action);
@@ -2433,8 +2437,10 @@ static struct irqaction *__free_percpu_irq(unsigned int irq, void __percpu *dev_
 		*action_ptr = action->next;
 
 		/* Demote from NMI if we killed the last action */
-		if (!desc->action)
+		if (!desc->action) {
 			desc->istate &= ~IRQS_NMI;
+			irq_proc_update_valid(desc);
+		}
 	}
 
 	unregister_handler_proc(irq, action);
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index d5b8126..cc9c7c9 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -440,6 +440,16 @@ 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)
@@ -516,10 +526,7 @@ int show_interrupts(struct seq_file *p, void *v)
 
 	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);
diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
index 00b3bd1..0a0c027 100644
--- 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(struct irq_desc *desc)
 {
 	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);
+}