On 17/07/17 18:59, Niklas Söderlund wrote:
> There is no good reason to hold the list_lock when reprobing the devices
> and it prevents a clean implementation of subdevice notifiers. Move the
> actual release of the devices outside of the loop which requires the
> lock to be held.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> ---
> drivers/media/v4l2-core/v4l2-async.c | 29 ++++++++++-------------------
> 1 file changed, 10 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 0acf288d7227ba97..8fc84f7962386ddd 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -206,7 +206,7 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> unsigned int notif_n_subdev = notifier->num_subdevs;
> unsigned int n_subdev = min(notif_n_subdev, V4L2_MAX_SUBDEVS);
> struct device **dev;
> - int i = 0;
> + int i, count = 0;
>
> if (!notifier->v4l2_dev)
> return;
> @@ -222,37 +222,28 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> list_del(¬ifier->list);
>
> list_for_each_entry_safe(sd, tmp, ¬ifier->done, async_list) {
> - struct device *d;
> -
> - d = get_device(sd->dev);
> + if (dev)
> + dev[count] = get_device(sd->dev);
> + count++;
>
> if (notifier->unbind)
> notifier->unbind(notifier, sd, sd->asd);
>
> v4l2_async_cleanup(sd);
> + }
>
> - /* If we handled USB devices, we'd have to lock the parent too */
> - device_release_driver(d);
> + mutex_unlock(&list_lock);
>
> - /*
> - * Store device at the device cache, in order to call
> - * put_device() on the final step
> - */
> + for (i = 0; i < count; i++) {
> + /* If we handled USB devices, we'd have to lock the parent too */
> if (dev)
> - dev[i++] = d;
> - else
> - put_device(d);
> + device_release_driver(dev[i]);
This changes the behavior. If the alloc failed, then at least put_device was still called.
Now that no longer happens.
Frankly I don't understand this code, it is in desperate need of some comments explaining
this whole reprobing thing.
I have this strong feeling that this function needs to be reworked.
Regards,
Hans
> }
>
> - mutex_unlock(&list_lock);
> -
> /*
> * Call device_attach() to reprobe devices
> - *
> - * NOTE: If dev allocation fails, i is 0, and the whole loop won't be
> - * executed.
> */
> - while (i--) {
> + for (i = 0; dev && i < count; i++) {
> struct device *d = dev[i];
>
> if (d && device_attach(d) < 0) {
>
