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authorRobert Foss <robert.foss@collabora.com>2016-08-09 10:54:52 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-08-10 10:15:30 +0200
commitc1da59dad0ebd3f9bd238f3fff82b1f7ffda7829 (patch)
tree5620e6f5048a292a608aca7afa96c3ee742523be
parent0775a9cbc694e8c7276688be3bbd2f386167ab54 (diff)
cdc-wdm: Clear read pipeline in case of error
Implemented queued response handling. This queue is processed every time the WDM_READ flag is cleared. In case of a read error, userspace may not actually read the data, since the driver returns an error through wdm_poll. After this, the underlying device may attempt to send us more data, but the queue is not processed. While userspace is also blocked, because the read error is never cleared. After this patch, we proactively process the queue on a read error. If there was an outstanding response to handle, that will clear the error (or go through the same logic again, if another read error occurs). If there was no outstanding response, this will bring the queue size back to 0, unblocking a future response from the underlying device. Signed-off-by: Robert Foss <robert.foss@collabora.com> Tested-by: Robert Foss <robert.foss@collabora.com> Acked-by: Oliver Neukum <oneukum@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/usb/class/cdc-wdm.c39
1 files changed, 29 insertions, 10 deletions
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 4bfc48d..56d3ab8 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;