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genirq: Add rcuref count to struct irq_desc

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Prepare for a smarter iterator for /proc/interrupts so that the next
interrupt descriptor can be cached after lookup.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Dmitry Ilvokhin <d@ilvokhin.com>
Link: https://patch.msgid.link/20260517194931.917415190@kernel.org
This commit is contained in:
Thomas Gleixner
2026-05-17 22:02:34 +02:00
parent 34594da765
commit 1d9c4745bf
3 changed files with 31 additions and 9 deletions
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2
include/linux/irqdesc.h
View File

@@ -70,6 +70,7 @@ struct irq_redirect {
* IRQF_NO_SUSPEND set
* @force_resume_depth: number of irqactions on a irq descriptor with
* IRQF_FORCE_RESUME set
* @refcnt: Reference count mainly for /proc/interrupts
* @rcu: rcu head for delayed free
* @kobj: kobject used to represent this struct in sysfs
* @request_mutex: mutex to protect request/free before locking desc->lock
@@ -119,6 +120,7 @@ struct irq_desc {
struct dentry *debugfs_file;
const char *dev_name;
#endif
rcuref_t refcnt;
#ifdef CONFIG_SPARSE_IRQ
struct rcu_head rcu;
struct kobject kobj;

17
kernel/irq/internals.h
View File

@@ -9,6 +9,7 @@
#include <linux/irqdesc.h>
#include <linux/kernel_stat.h>
#include <linux/pm_runtime.h>
#include <linux/rcuref.h>
#include <linux/sched/clock.h>
#ifdef CONFIG_SPARSE_IRQ
@@ -101,9 +102,23 @@ extern void unmask_irq(struct irq_desc *desc);
extern void unmask_threaded_irq(struct irq_desc *desc);
#ifdef CONFIG_SPARSE_IRQ
static inline void irq_mark_irq(unsigned int irq) { }
static __always_inline void irq_mark_irq(unsigned int irq) { }
void irq_desc_free_rcu(struct irq_desc *desc);
static __always_inline bool irq_desc_get_ref(struct irq_desc *desc)
{
return rcuref_get(&desc->refcnt);
}
static __always_inline void irq_desc_put_ref(struct irq_desc *desc)
{
if (rcuref_put(&desc->refcnt))
irq_desc_free_rcu(desc);
}
#else
extern void irq_mark_irq(unsigned int irq);
static __always_inline bool irq_desc_get_ref(struct irq_desc *desc) { return true; }
static __always_inline void irq_desc_put_ref(struct irq_desc *desc) { }
#endif
irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc);

21
kernel/irq/irqdesc.c
View File

@@ -137,6 +137,7 @@ static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node,
desc->tot_count = 0;
desc->name = NULL;
desc->owner = owner;
rcuref_init(&desc->refcnt, 1);
desc_smp_init(desc, node, affinity);
}
@@ -465,6 +466,17 @@ static void delayed_free_desc(struct rcu_head *rhp)
kobject_put(&desc->kobj);
}
void irq_desc_free_rcu(struct irq_desc *desc)
{
/*
* We free the descriptor, masks and stat fields via RCU. That
* allows demultiplex interrupts to do rcu based management of
* the child interrupts.
* This also allows us to use rcu in kstat_irqs_usr().
*/
call_rcu(&desc->rcu, delayed_free_desc);
}
static void free_desc(unsigned int irq)
{
struct irq_desc *desc = irq_to_desc(irq);
@@ -483,14 +495,7 @@ static void free_desc(unsigned int irq)
*/
irq_sysfs_del(desc);
delete_irq_desc(irq);
/*
* We free the descriptor, masks and stat fields via RCU. That
* allows demultiplex interrupts to do rcu based management of
* the child interrupts.
* This also allows us to use rcu in kstat_irqs_usr().
*/
call_rcu(&desc->rcu, delayed_free_desc);
irq_desc_put_ref(desc);
}
static int alloc_descs(unsigned int start, unsigned int cnt, int node,