CHROMIUM: uvcvideo: Handle status_start while status_stop is in progress.

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.

BUG=chromium:226216
TEST=Manual. Repeat suspend / resume on Stout many times, verify that
open() on /dev/video0 never fails.

Change-Id: I8a69dab345a18c89e175bd916aa943edd080b6cc
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/48982
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

diff --git a/drivers/media/video/uvc/uvc_v4l2.c b/drivers/media/video/uvc/uvc_v4l2.c
index 8db90ef..ff358cb 100644 (file)
--- a/drivers/media/video/uvc/uvc_v4l2.c
+++ b/drivers/media/video/uvc/uvc_v4l2.c
@@ -476,6 +476,7 @@ 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");
@@ -496,7 +497,14 @@ 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) {
                        usb_autopm_put_interface(stream->dev->intf);
                        atomic_dec(&stream->dev->users);

diff --git a/drivers/media/video/uvc/uvcvideo.h b/drivers/media/video/uvc/uvcvideo.h
index 67f88d8..d2c81d0 100644 (file)
--- a/drivers/media/video/uvc/uvcvideo.h
+++ b/drivers/media/video/uvc/uvcvideo.h
@@ -111,6 +111,7 @@
 
 #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