1 files changed, 63 insertions, 34 deletions

diff --git a/drivers/platform/x86/intel_speed_select_if/isst_if_common.c b/drivers/platform/x86/intel_speed_select_if/isst_if_common.c
index 3de5a3c66529..cf7b6dee8219 100644
--- a/drivers/platform/x86/intel_speed_select_if/isst_if_common.c
+++ b/drivers/platform/x86/intel_speed_select_if/isst_if_common.c
@@ -529,7 +529,10 @@ static long isst_if_def_ioctl(struct file *file, unsigned int cmd,
 	return ret;
 }
 
-static DEFINE_MUTEX(punit_misc_dev_lock);
+/* Lock to prevent module registration when already opened by user space */
+static DEFINE_MUTEX(punit_misc_dev_open_lock);
+/* Lock to allow one share misc device for all ISST interace */
+static DEFINE_MUTEX(punit_misc_dev_reg_lock);
 static int misc_usage_count;
 static int misc_device_ret;
 static int misc_device_open;
@@ -539,7 +542,7 @@ static int isst_if_open(struct inode *inode, struct file *file)
 	int i, ret = 0;
 
 	/* Fail open, if a module is going away */
-	mutex_lock(&punit_misc_dev_lock);
+	mutex_lock(&punit_misc_dev_open_lock);
 	for (i = 0; i < ISST_IF_DEV_MAX; ++i) {
 		struct isst_if_cmd_cb *cb = &punit_callbacks[i];
 
@@ -561,7 +564,7 @@ static int isst_if_open(struct inode *inode, struct file *file)
 	} else {
 		misc_device_open++;
 	}
-	mutex_unlock(&punit_misc_dev_lock);
+	mutex_unlock(&punit_misc_dev_open_lock);
 
 	return ret;
 }
@@ -570,7 +573,7 @@ static int isst_if_relase(struct inode *inode, struct file *f)
 {
 	int i;
 
-	mutex_lock(&punit_misc_dev_lock);
+	mutex_lock(&punit_misc_dev_open_lock);
 	misc_device_open--;
 	for (i = 0; i < ISST_IF_DEV_MAX; ++i) {
 		struct isst_if_cmd_cb *cb = &punit_callbacks[i];
@@ -578,7 +581,7 @@ static int isst_if_relase(struct inode *inode, struct file *f)
 		if (cb->registered)
 			module_put(cb->owner);
 	}
-	mutex_unlock(&punit_misc_dev_lock);
+	mutex_unlock(&punit_misc_dev_open_lock);
 
 	return 0;
 }
@@ -595,6 +598,43 @@ static struct miscdevice isst_if_char_driver = {
 	.fops		= &isst_if_char_driver_ops,
 };
 
+static int isst_misc_reg(void)
+{
+	mutex_lock(&punit_misc_dev_reg_lock);
+	if (misc_device_ret)
+		goto unlock_exit;
+
+	if (!misc_usage_count) {
+		misc_device_ret = isst_if_cpu_info_init();
+		if (misc_device_ret)
+			goto unlock_exit;
+
+		misc_device_ret = misc_register(&isst_if_char_driver);
+		if (misc_device_ret) {
+			isst_if_cpu_info_exit();
+			goto unlock_exit;
+		}
+	}
+	misc_usage_count++;
+
+unlock_exit:
+	mutex_unlock(&punit_misc_dev_reg_lock);
+
+	return misc_device_ret;
+}
+
+static void isst_misc_unreg(void)
+{
+	mutex_lock(&punit_misc_dev_reg_lock);
+	if (misc_usage_count)
+		misc_usage_count--;
+	if (!misc_usage_count && !misc_device_ret) {
+		misc_deregister(&isst_if_char_driver);
+		isst_if_cpu_info_exit();
+	}
+	mutex_unlock(&punit_misc_dev_reg_lock);
+}
+
 /**
  * isst_if_cdev_register() - Register callback for IOCTL
  * @device_type: The device type this callback handling.
@@ -612,38 +652,31 @@ static struct miscdevice isst_if_char_driver = {
  */
 int isst_if_cdev_register(int device_type, struct isst_if_cmd_cb *cb)
 {
-	if (misc_device_ret)
-		return misc_device_ret;
+	int ret;
 
 	if (device_type >= ISST_IF_DEV_MAX)
 		return -EINVAL;
 
-	mutex_lock(&punit_misc_dev_lock);
+	mutex_lock(&punit_misc_dev_open_lock);
+	/* Device is already open, we don't want to add new callbacks */
 	if (misc_device_open) {
-		mutex_unlock(&punit_misc_dev_lock);
+		mutex_unlock(&punit_misc_dev_open_lock);
 		return -EAGAIN;
 	}
-	if (!misc_usage_count) {
-		int ret;
-
-		misc_device_ret = misc_register(&isst_if_char_driver);
-		if (misc_device_ret)
-			goto unlock_exit;
-
-		ret = isst_if_cpu_info_init();
-		if (ret) {
-			misc_deregister(&isst_if_char_driver);
-			misc_device_ret = ret;
-			goto unlock_exit;
-		}
-	}
 	memcpy(&punit_callbacks[device_type], cb, sizeof(*cb));
 	punit_callbacks[device_type].registered = 1;
-	misc_usage_count++;
-unlock_exit:
-	mutex_unlock(&punit_misc_dev_lock);
+	mutex_unlock(&punit_misc_dev_open_lock);
 
-	return misc_device_ret;
+	ret = isst_misc_reg();
+	if (ret) {
+		/*
+		 * No need of mutex as the misc device register failed
+		 * as no one can open device yet. Hence no contention.
+		 */
+		punit_callbacks[device_type].registered = 0;
+		return ret;
+	}
+	return 0;
 }
 EXPORT_SYMBOL_GPL(isst_if_cdev_register);
 
@@ -658,16 +691,12 @@ EXPORT_SYMBOL_GPL(isst_if_cdev_register);
  */
 void isst_if_cdev_unregister(int device_type)
 {
-	mutex_lock(&punit_misc_dev_lock);
-	misc_usage_count--;
+	isst_misc_unreg();
+	mutex_lock(&punit_misc_dev_open_lock);
 	punit_callbacks[device_type].registered = 0;
 	if (device_type == ISST_IF_DEV_MBOX)
 		isst_delete_hash();
-	if (!misc_usage_count && !misc_device_ret) {
-		misc_deregister(&isst_if_char_driver);
-		isst_if_cpu_info_exit();
-	}
-	mutex_unlock(&punit_misc_dev_lock);
+	mutex_unlock(&punit_misc_dev_open_lock);
 }
 EXPORT_SYMBOL_GPL(isst_if_cdev_unregister);