linux-kernel - [PATCH kernel v4 4/8] genirq: Free IRQ descriptor via embedded kobject

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Date:   Tue, 24 Nov 2020 17:17:16 +1100
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     linux-kernel@...r.kernel.org
Cc:     Cédric Le Goater <clg@...d.org>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Michal Suchánek <msuchanek@...e.de>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org,
        x86@...nel.org, linuxppc-dev@...ts.ozlabs.org,
        Alexey Kardashevskiy <aik@...abs.ru>
Subject: [PATCH kernel v4 4/8] genirq: Free IRQ descriptor via embedded kobject

At the moment the IRQ descriptor is freed via the free_desc() helper.
We want to add reference counting to IRQ descriptors and there is already
kobj embedded into irq_desc which we want to reuse.

This shuffles free_desc()/etc to make it simply call kobject_put() and
moves all the cleanup into the kobject_release hook.

As a bonus, we do not need irq_sysfs_del() as kobj removes itself from
sysfs if it knows that it was added.

This should cause no behavioral change.

Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
---
 kernel/irq/irqdesc.c | 42 ++++++++++++------------------------------
 1 file changed, 12 insertions(+), 30 deletions(-)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 1a7723604399..75374b7944b5 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -295,18 +295,6 @@ static void irq_sysfs_add(int irq, struct irq_desc *desc)
 	}
 }
 
-static void irq_sysfs_del(struct irq_desc *desc)
-{
-	/*
-	 * If irq_sysfs_init() has not yet been invoked (early boot), then
-	 * irq_kobj_base is NULL and the descriptor was never added.
-	 * kobject_del() complains about a object with no parent, so make
-	 * it conditional.
-	 */
-	if (irq_kobj_base)
-		kobject_del(&desc->kobj);
-}
-
 static int __init irq_sysfs_init(void)
 {
 	struct irq_desc *desc;
@@ -337,7 +325,6 @@ static struct kobj_type irq_kobj_type = {
 };
 
 static void irq_sysfs_add(int irq, struct irq_desc *desc) {}
-static void irq_sysfs_del(struct irq_desc *desc) {}
 
 #endif /* CONFIG_SYSFS */
 
@@ -419,39 +406,34 @@ static struct irq_desc *alloc_desc(int irq, int node, unsigned int flags,
 	return NULL;
 }
 
-static void irq_kobj_release(struct kobject *kobj)
-{
-	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
-
-	free_masks(desc);
-	free_percpu(desc->kstat_irqs);
-	kfree(desc);
-}
-
 static void delayed_free_desc(struct rcu_head *rhp)
 {
 	struct irq_desc *desc = container_of(rhp, struct irq_desc, rcu);
 
+	free_masks(desc);
+	free_percpu(desc->kstat_irqs);
+	kfree(desc);
+}
+
+static void free_desc(unsigned int irq)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+
 	kobject_put(&desc->kobj);
 }
 
-static void free_desc(unsigned int irq)
+static void irq_kobj_release(struct kobject *kobj)
 {
-	struct irq_desc *desc = irq_to_desc(irq);
+	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
+	unsigned int irq = desc->irq_data.irq;
 
 	irq_remove_debugfs_entry(desc);
 	unregister_irq_proc(irq, desc);
 
 	/*
-	 * sparse_irq_lock protects also show_interrupts() and
-	 * kstat_irq_usr(). Once we deleted the descriptor from the
-	 * sparse tree we can free it. Access in proc will fail to
-	 * lookup the descriptor.
-	 *
 	 * The sysfs entry must be serialized against a concurrent
 	 * irq_sysfs_init() as well.
 	 */
-	irq_sysfs_del(desc);
 	delete_irq_desc(irq);
 
 	/*
-- 
2.17.1