[RFC PATCH] radio-mr800: locking fixes

[Hans Verkuil]

- serialize the suspend and resume functions using the global lock.
- do not call usb_autopm_put_interface after a disconnect.
- fix a race when disconnecting the device.

Reported-by: David Ellingsworth <da...@identd.dyndns.org>
Signed-off-by: Hans Verkuil <hverk...@xs4all.nl>
---
 drivers/media/radio/radio-mr800.c |   17 ++++++++++++++---
 1 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/media/radio/radio-mr800.c 
b/drivers/media/radio/radio-mr800.c
index 2f56b26..b540e80 100644
--- a/drivers/media/radio/radio-mr800.c
+++ b/drivers/media/radio/radio-mr800.c
@@ -284,9 +284,13 @@ static void usb_amradio_disconnect(struct usb_interface 
*intf)
        struct amradio_device *radio = to_amradio_dev(usb_get_intfdata(intf));
 
        mutex_lock(&radio->lock);
+       /* increase the device node's refcount */
+       get_device(&radio->videodev.dev);
        v4l2_device_disconnect(&radio->v4l2_dev);
-       mutex_unlock(&radio->lock);
        video_unregister_device(&radio->videodev);
+       mutex_unlock(&radio->lock);
+       /* decrease the device node's refcount, allowing it to be released */
+       put_device(&radio->videodev.dev);
 }
 
 /* vidioc_querycap - query device capabilities */
@@ -515,7 +519,8 @@ static int usb_amradio_close(struct file *file)
 {
        struct amradio_device *radio = file->private_data;
 
-       usb_autopm_put_interface(radio->intf);
+       if (video_is_registered(&radio->videodev))
+               usb_autopm_put_interface(radio->intf);
        return 0;
 }
 
@@ -524,10 +529,12 @@ static int usb_amradio_suspend(struct usb_interface 
*intf, pm_message_t message)
 {
        struct amradio_device *radio = to_amradio_dev(usb_get_intfdata(intf));
 
+       mutex_lock(&radio->lock);
        if (!radio->muted && radio->initialized) {
                amradio_set_mute(radio, AMRADIO_STOP);
                radio->muted = 0;
        }
+       mutex_unlock(&radio->lock);
 
        dev_info(&intf->dev, "going into suspend..\n");
        return 0;
@@ -538,8 +545,9 @@ static int usb_amradio_resume(struct usb_interface *intf)
 {
        struct amradio_device *radio = to_amradio_dev(usb_get_intfdata(intf));
 
+       mutex_lock(&radio->lock);
        if (unlikely(!radio->initialized))
-               return 0;
+               goto unlock;
 
        if (radio->stereo)
                amradio_set_stereo(radio, WANT_STEREO);
@@ -551,6 +559,9 @@ static int usb_amradio_resume(struct usb_interface *intf)
        if (!radio->muted)
                amradio_set_mute(radio, AMRADIO_START);
 
+unlock:
+       mutex_unlock(&radio->lock);
+
        dev_info(&intf->dev, "coming out of suspend..\n");
        return 0;
 }
-- 
1.7.0.4

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