linux-kernel - [PATCH V6 3/4] misc/pvpanic: Avoid initializing multiple pvpanic devices

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Date:   Tue, 19 Feb 2019 19:27:47 +0800
From:   Peng Hao <peng.hao2@....com.cn>
To:     gregkh@...uxfoundation.org, arnd@...db.de,
        andy.shevchenko@...il.com
Cc:     linux-kernel@...r.kernel.org, Peng Hao <peng.hao2@....com.cn>
Subject: [PATCH V6 3/4]  misc/pvpanic: Avoid initializing multiple pvpanic devices

Avoid initializing multiple pvpanic devices when configure multiple
pvpanic device driver type. Make sure that only one pvpanic device
is working.

Signed-off-by: Peng Hao <peng.hao2@....com.cn>
---
 drivers/misc/pvpanic/pvpanic.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/pvpanic/pvpanic.c b/drivers/misc/pvpanic/pvpanic.c
index ccadec0..3c9d957 100644
--- a/drivers/misc/pvpanic/pvpanic.c
+++ b/drivers/misc/pvpanic/pvpanic.c
@@ -15,10 +15,13 @@
 #include <linux/types.h>
 
 static struct {
+	struct mutex lock;
 	struct platform_device *pdev;
 	void __iomem *base;
 	bool is_ioport;
-} pvpanic_data;
+} pvpanic_data = {
+	.lock = __MUTEX_INITIALIZER(pvpanic_data.lock),
+};
 
 #define PVPANIC_PANICKED        (1 << 0)
 
@@ -50,9 +53,17 @@ int pvpanic_add_device(struct device *dev, struct resource *res)
 	struct platform_device *pdev;
 	int ret;
 
+	mutex_lock(&pvpanic_data.lock);
+	if (pvpanic_data.pdev) {
+		mutex_unlock(&pvpanic_data.lock);
+		return -EEXIST;
+	}
+
 	pdev = platform_device_alloc("pvpanic", -1);
-	if (!pdev)
+	if (!pdev) {
+		mutex_unlock(&pvpanic_data.lock);
 		return -ENOMEM;
+	}
 
 	pdev->dev.parent = dev;
 
@@ -64,9 +75,11 @@ int pvpanic_add_device(struct device *dev, struct resource *res)
 	if (ret)
 		goto err;
 	pvpanic_data.pdev = pdev;
+	mutex_unlock(&pvpanic_data.lock);
 
 	return 0;
 err:
+	mutex_unlock(&pvpanic_data.lock);
 	platform_device_put(pdev);
 	return ret;
 }
@@ -74,8 +87,10 @@ int pvpanic_add_device(struct device *dev, struct resource *res)
 
 void pvpanic_remove_device(void)
 {
+	mutex_lock(&pvpanic_data.lock);
 	platform_device_unregister(pvpanic_data.pdev);
 	pvpanic_data.pdev = NULL;
+	mutex_unlock(&pvpanic_data.lock);
 }
 EXPORT_SYMBOL_GPL(pvpanic_remove_device);
 
-- 
1.8.3.1