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From:   Pingfan Liu <kernelfans@gmail.com>
To:     linux-kernel@vger.kernel.org
Cc:     Pingfan Liu <kernelfans@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH 1/9] irq/irqdesc: put the lock at the exact place in irq_sysfs_init()
Date:   Wed, 20 Apr 2022 22:05:13 +0800
Message-Id: <20220420140521.45361-2-kernelfans@gmail.com>
In-Reply-To: <20220420140521.45361-1-kernelfans@gmail.com>
References: <20220420140521.45361-1-kernelfans@gmail.com>
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sparse_irq_lock is used to protect irq_desc, and furthermore
irq_sysfs_init() is called only once, so put irq_lock_sparse() at the
exact place, where the race condition may start.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
To: linux-kernel@vger.kernel.org
---
 kernel/irq/irqdesc.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 939d21cd55c3..8d0982233277 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -312,15 +312,14 @@ static int __init irq_sysfs_init(void)
 	struct irq_desc *desc;
 	int irq;
 
-	/* Prevent concurrent irq alloc/free */
-	irq_lock_sparse();
-
 	irq_kobj_base = kobject_create_and_add("irq", kernel_kobj);
 	if (!irq_kobj_base) {
-		irq_unlock_sparse();
 		return -ENOMEM;
 	}
 
+	/* Prevent concurrent irq alloc/free */
+	irq_lock_sparse();
+
 	/* Add the already allocated interrupts */
 	for_each_irq_desc(irq, desc)
 		irq_sysfs_add(irq, desc);
-- 
2.31.1