mailbox: mailbox-test: make data_ready a per-instance variable

[ Upstream commit 6e937f4 ]

While not the default case, multiple tests can be run simultaneously.
Then, data_ready being a global variable will be overwritten and the
per-instance lock will not help. Turn the global variable into a
per-instance one to avoid this problem.

Fixes: e339c80 ("mailbox: mailbox-test: don't rely on rx_buffer content to signal data ready")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Wolfram Sang

drivers/mailbox/mailbox-test.c

@@ -28,8 +28,6 @@
 #define MBOX_HEXDUMP_MAX_LEN	(MBOX_HEXDUMP_LINE_LEN *		\
 				 (MBOX_MAX_MSG_LEN / MBOX_BYTES_PER_LINE))
 
-static bool mbox_data_ready;
-
 struct mbox_test_device {
 	struct device		*dev;
 	void __iomem		*tx_mmio;
@@ -42,6 +40,7 @@ struct mbox_test_device {
 	spinlock_t		lock;
 	struct mutex		mutex;
 	wait_queue_head_t	waitq;
+	bool			data_ready;
 	struct fasync_struct	*async_queue;
 	struct dentry		*root_debugfs_dir;
 };
@@ -162,7 +161,7 @@ static bool mbox_test_message_data_ready(struct mbox_test_device *tdev)
 	unsigned long flags;
 
 	spin_lock_irqsave(&tdev->lock, flags);
-	data_ready = mbox_data_ready;
+	data_ready = tdev->data_ready;
 	spin_unlock_irqrestore(&tdev->lock, flags);
 
 	return data_ready;
@@ -227,7 +226,7 @@ static ssize_t mbox_test_message_read(struct file *filp, char __user *userbuf,
 	*(touser + l) = '\0';
 
 	memset(tdev->rx_buffer, 0, MBOX_MAX_MSG_LEN);
-	mbox_data_ready = false;
+	tdev->data_ready = false;
 
 	spin_unlock_irqrestore(&tdev->lock, flags);
 
@@ -297,7 +296,7 @@ static void mbox_test_receive_message(struct mbox_client *client, void *message)
 				     message, MBOX_MAX_MSG_LEN);
 		memcpy(tdev->rx_buffer, message, MBOX_MAX_MSG_LEN);
 	}
-	mbox_data_ready = true;
+	tdev->data_ready = true;
 	spin_unlock_irqrestore(&tdev->lock, flags);
 
 	wake_up_interruptible(&tdev->waitq);