While usb_kill_urb is in progress, calls to usb_submit_urb will fail
with -EPERM (documented in Documentation/usb/URB.txt). The UVC driver
does not correctly handle this case -- there is no synchronization
between uvc_v4l2_open / uvc_status_start and uvc_v4l2_release /
uvc_status_stop.
This patch adds a retry / timeout when uvc_status_open / usb_submit_urb
returns -EPERM. This usually means that usb_kill_urb is in progress, and
we just need to wait a while.
Signed-off-by: Shawn Nematbakhsh <sha...@chromium.org>
---
drivers/media/usb/uvc/uvc_v4l2.c | 10 +++++++++-
drivers/media/usb/uvc/uvcvideo.h | 1 +
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index b2dc326..f1498a8 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -479,6 +479,7 @@ static int uvc_v4l2_open(struct file *file)
{
struct uvc_streaming *stream;
struct uvc_fh *handle;
+ unsigned long timeout;
int ret = 0;
uvc_trace(UVC_TRACE_CALLS, "uvc_v4l2_open\n");
@@ -499,7 +500,14 @@ static int uvc_v4l2_open(struct file *file)
}
if (atomic_inc_return(&stream->dev->users) == 1) {
- ret = uvc_status_start(stream->dev);
+ timeout = jiffies + msecs_to_jiffies(UVC_STATUS_START_TIMEOUT);
+ /* -EPERM means stop in progress, wait for completion */
+ do {
+ ret = uvc_status_start(stream->dev);
+ if (ret == -EPERM)
+ usleep_range(5000, 6000);
+ } while (ret == -EPERM && time_before(jiffies, timeout));
+
if (ret < 0) {
atomic_dec(&stream->dev->users);
usb_autopm_put_interface(stream->dev->intf);
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index af505fd..a47e1d3 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -122,6 +122,7 @@
#define UVC_CTRL_CONTROL_TIMEOUT 300
#define UVC_CTRL_STREAMING_TIMEOUT 5000
+#define UVC_STATUS_START_TIMEOUT 100
/* Maximum allowed number of control mappings per device */
#define UVC_MAX_CONTROL_MAPPINGS 1024
--
1.7.12.4
--
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