[PATCH] wip: USB: lsusb: fix ring-buffer locking

[Johan Hovold]

Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
---
 drivers/usb/misc/ldusb.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
index f3108d85e768..c8d09ac7ade9 100644
--- a/drivers/usb/misc/ldusb.c
+++ b/drivers/usb/misc/ldusb.c
@@ -467,7 +467,7 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
 
 	/* wait for data */
 	spin_lock_irq(&dev->rbsl);
-	if (dev->ring_head == dev->ring_tail) {
+	while (dev->ring_head == dev->ring_tail) {
 		dev->interrupt_in_done = 0;
 		spin_unlock_irq(&dev->rbsl);
 		if (file->f_flags & O_NONBLOCK) {
@@ -477,8 +477,8 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
 		retval = wait_event_interruptible(dev->read_wait, dev->interrupt_in_done);
 		if (retval < 0)
 			goto unlock_exit;
-	} else {
-		spin_unlock_irq(&dev->rbsl);
+
+		spin_lock_irq(&dev->rbsl);
 	}
 
 	/* actual_buffer contains actual_length + interrupt_in_buffer */
@@ -487,17 +487,19 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
 	if (bytes_to_read < *actual_buffer)
 		dev_warn(&dev->intf->dev, "Read buffer overflow, %zd bytes dropped\n",
 			 *actual_buffer-bytes_to_read);
+	spin_unlock_irq(&dev->rbsl);
 
 	/* copy one interrupt_in_buffer from ring_buffer into userspace */
 	if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) {
 		retval = -EFAULT;
 		goto unlock_exit;
 	}
-	dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size;
-
 	retval = bytes_to_read;
 
 	spin_lock_irq(&dev->rbsl);
+
+	dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size;
+
 	if (dev->buffer_overflow) {
 		dev->buffer_overflow = 0;
 		spin_unlock_irq(&dev->rbsl);
@@ -693,12 +695,17 @@ static int ld_usb_probe(struct usb_interface *intf, const struct usb_device_id *
 		dev_warn(&intf->dev, "Interrupt out endpoint not found (using control endpoint instead)\n");
 
 	dev->interrupt_in_endpoint_size = usb_endpoint_maxp(dev->interrupt_in_endpoint);
+	dev_info(&intf->dev, "%s - interrupt_in_endpoint_size = %zu\n",
+			__func__, dev->interrupt_in_endpoint_size);
 	dev->ring_buffer =
 		kmalloc_array(ring_buffer_size,
 			      sizeof(size_t) + dev->interrupt_in_endpoint_size,
 			      GFP_KERNEL);
 	if (!dev->ring_buffer)
 		goto error;
+	dev_info(&intf->dev, "%s - ring_buffer = %px\n", __func__,
+			dev->ring_buffer);
+
 	dev->interrupt_in_buffer = kmalloc(dev->interrupt_in_endpoint_size, GFP_KERNEL);
 	if (!dev->interrupt_in_buffer)
 		goto error;
-- 
2.23.0