1 files changed, 29 insertions, 10 deletions

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 4bfc48d18654..56d3ab86be7f 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -155,6 +155,9 @@ static void wdm_out_callback(struct urb *urb)
 	wake_up(&desc->wait);
 }
 
+/* forward declaration */
+static int service_outstanding_interrupt(struct wdm_device *desc);
+
 static void wdm_in_callback(struct urb *urb)
 {
 	struct wdm_device *desc = urb->context;
@@ -189,7 +192,13 @@ static void wdm_in_callback(struct urb *urb)
 		}
 	}
 
-	desc->rerr = status;
+	/*
+	 * only set a new error if there is no previous error.
+	 * Errors are only cleared during read/open
+	 */
+	if (desc->rerr  == 0)
+		desc->rerr = status;
+
 	if (length + desc->length > desc->wMaxCommand) {
 		/* The buffer would overflow */
 		set_bit(WDM_OVERFLOW, &desc->flags);
@@ -221,9 +230,19 @@ static void wdm_in_callback(struct urb *urb)
 	}
 
 skip_error:
+	set_bit(WDM_READ, &desc->flags);
 	wake_up(&desc->wait);
 
-	set_bit(WDM_READ, &desc->flags);
+	if (desc->rerr) {
+		/*
+		 * Since there was an error, userspace may decide to not read
+		 * any data after poll'ing.
+		 * We should respond to further attempts from the device to send
+		 * data, so that we can get unstuck.
+		 */
+		service_outstanding_interrupt(desc);
+	}
+
 unlock:
 	spin_unlock(&desc->iuspin);
 }
@@ -457,17 +476,14 @@ out_free_mem:
 }
 
 /*
- * clear WDM_READ flag and possibly submit the read urb if resp_count
- * is non-zero.
+ * Submit the read urb if resp_count is non-zero.
  *
  * Called with desc->iuspin locked
  */
-static int clear_wdm_read_flag(struct wdm_device *desc)
+static int service_outstanding_interrupt(struct wdm_device *desc)
 {
 	int rv = 0;
 
-	clear_bit(WDM_READ, &desc->flags);
-
 	/* submit read urb only if the device is waiting for it */
 	if (!desc->resp_count || !--desc->resp_count)
 		goto out;
@@ -559,7 +575,8 @@ retry:
 
 		if (!desc->reslength) { /* zero length read */
 			dev_dbg(&desc->intf->dev, "%s: zero length - clearing WDM_READ\n", __func__);
-			rv = clear_wdm_read_flag(desc);
+			clear_bit(WDM_READ, &desc->flags);
+			rv = service_outstanding_interrupt(desc);
 			spin_unlock_irq(&desc->iuspin);
 			if (rv < 0)
 				goto err;
@@ -584,8 +601,10 @@ retry:
 
 	desc->length -= cntr;
 	/* in case we had outstanding data */
-	if (!desc->length)
-		clear_wdm_read_flag(desc);
+	if (!desc->length) {
+		clear_bit(WDM_READ, &desc->flags);
+		service_outstanding_interrupt(desc);
+	}
 	spin_unlock_irq(&desc->iuspin);
 	rv = cntr;