linux-kernel - [PATCH 8/9] irq: make irq_lock_sparse() independent of CONFIG_SPARSE

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Date:   Wed, 20 Apr 2022 22:05:20 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Pingfan Liu <kernelfans@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 8/9] irq: make irq_lock_sparse() independent of CONFIG_SPARSE_IRQ

Even in the case of non-sparse irq, the callsite of
for_each_active_irq() in irq_debugfs_init() still cares about the sync
of allocated_irqs bitmap. Otherwise irq_debugfs_init() may show some
disappeared irq if the irq is disactived by other driver in parallel.

As there are only a few callsites of irq_lock_sparse() in the cold path,
which means the slight performance drops can be ignored.  Hence moving
irq_lock_sparse() out of CONFIG_SPARSE_IRQ to protect both irq_desc and
allocated_irqs bitmap, instead of making irq_lock_sparse() dependent on
GENERIC_IRQ_DEBUGFS.

Signed-off-by: Pingfan Liu <kernelfans@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Mark Rutland <mark.rutland@....com>
To: linux-kernel@...r.kernel.org
---
 include/linux/irqdesc.h |  6 ++----
 kernel/irq/irqdesc.c    | 20 ++++++++++----------
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index a77584593f7d..6c01231fec00 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -104,12 +104,10 @@ struct irq_desc {
 	const char		*name;
 } ____cacheline_internodealigned_in_smp;
 
-#ifdef CONFIG_SPARSE_IRQ
 extern void irq_lock_sparse(void);
 extern void irq_unlock_sparse(void);
-#else
-static inline void irq_lock_sparse(void) { }
-static inline void irq_unlock_sparse(void) { }
+
+#ifndef CONFIG_SPARSE_IRQ
 extern struct irq_desc irq_desc[NR_IRQS];
 #endif
 
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 9feedaa08430..a5cefd7c9ef7 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -375,16 +375,6 @@ static void free_masks(struct irq_desc *desc)
 static inline void free_masks(struct irq_desc *desc) { }
 #endif
 
-void irq_lock_sparse(void)
-{
-	mutex_lock(&sparse_irq_lock);
-}
-
-void irq_unlock_sparse(void)
-{
-	mutex_unlock(&sparse_irq_lock);
-}
-
 static struct irq_desc *alloc_desc(int irq, int node, unsigned int flags,
 				   const struct cpumask *affinity,
 				   struct module *owner)
@@ -721,6 +711,16 @@ int generic_handle_domain_nmi(struct irq_domain *domain, unsigned int hwirq)
 }
 #endif
 
+void irq_lock_sparse(void)
+{
+	mutex_lock(&sparse_irq_lock);
+}
+
+void irq_unlock_sparse(void)
+{
+	mutex_unlock(&sparse_irq_lock);
+}
+
 /* Dynamic interrupt handling */
 
 /**
-- 
2.31.1