linux-kernel - [PATCH] genirq: Pass desc to __irq

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Date:   Mon, 19 Mar 2018 11:52:02 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     kernel@...gutronix.de, linux-kernel@...r.kernel.org
Subject: [PATCH] genirq: Pass desc to __irq_free instead of irq number

Given that irq_to_desc() is a radix_tree_lookup and the reverse
operation is only a pointer dereference and that all callers of
__free_irq already have the desc, pass the desc instead of the irq
number.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
Hello,

this is a micro optimisation I noticed while looking at the irq code.

Best regards
Uwe

 kernel/irq/manage.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 0f922729bab9..a08ba9a8da14 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1519,9 +1519,9 @@ EXPORT_SYMBOL_GPL(setup_irq);
  * Internal function to unregister an irqaction - used to free
  * regular and special interrupts that are part of the architecture.
  */
-static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
+static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id)
 {
-	struct irq_desc *desc = irq_to_desc(irq);
+	unsigned irq = desc->irq_data.irq;
 	struct irqaction *action, **action_ptr;
 	unsigned long flags;
 
@@ -1651,7 +1651,7 @@ void remove_irq(unsigned int irq, struct irqaction *act)
 	struct irq_desc *desc = irq_to_desc(irq);
 
 	if (desc && !WARN_ON(irq_settings_is_per_cpu_devid(desc)))
-		__free_irq(irq, act->dev_id);
+		__free_irq(desc, act->dev_id);
 }
 EXPORT_SYMBOL_GPL(remove_irq);
 
@@ -1685,7 +1685,7 @@ const void *free_irq(unsigned int irq, void *dev_id)
 		desc->affinity_notify = NULL;
 #endif
 
-	action = __free_irq(irq, dev_id);
+	action = __free_irq(desc, dev_id);
 
 	if (!action)
 		return NULL;
-- 
2.16.2