Hi Niklas,
On Wed, May 24, 2017 at 02:07:27AM +0200, Niklas Söderlund wrote:
...
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index c16200c88417b151..e1e181db90f789c0 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -141,11 +141,13 @@ static void v4l2_async_cleanup(struct v4l2_subdev *sd)
> sd->dev = NULL;
> }
>
> -int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> - struct v4l2_async_notifier *notifier)
> +static int v4l2_async_do_notifier_register(struct v4l2_device *v4l2_dev,
> + struct v4l2_async_notifier *notifier,
> + bool subnotifier)
> {
> struct v4l2_subdev *sd, *tmp;
> struct v4l2_async_subdev *asd;
> + bool found;
> int i;
>
> if (!v4l2_dev || !notifier->num_subdevs ||
> @@ -174,32 +176,65 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> list_add_tail(&asd->list, ¬ifier->waiting);
> }
>
> - mutex_lock(&list_lock);
> + if (subnotifier)
> + lockdep_assert_held(&list_lock);
> + else
> + mutex_lock(&list_lock);
> +
> + /*
> + * This function can be called recursively so the list
> + * might be modified in a recursive call. Start from the
> + * top of the list each iteration.
> + */
> + found = true;
> + while (found) {
That looks a bit cumbersome. You can do:
do {
found = false;
...;
} while (found);
And remove the assignment above. Or even
for (found = true; found; found = false) {
...;
}
> + found = false;
>
> - list_for_each_entry_safe(sd, tmp, &subdev_list, async_list) {
> - int ret;
> + list_for_each_entry_safe(sd, tmp, &subdev_list, async_list) {
> + int ret;
>
> - asd = v4l2_async_belongs(notifier, sd);
> - if (!asd)
> - continue;
> + asd = v4l2_async_belongs(notifier, sd);
> + if (!asd)
> + continue;
>
> - ret = v4l2_async_test_notify(notifier, sd, asd);
> - if (ret < 0) {
> - mutex_unlock(&list_lock);
> - return ret;
> + ret = v4l2_async_test_notify(notifier, sd, asd);
> + if (ret < 0) {
> + if (!subnotifier)
> + mutex_unlock(&list_lock);
> + return ret;
> + }
> +
> + found = true;
Alternatively you could use goto and a label to restart the matching. That
would be quite clean, you'd remove one variable which is just serving as a
condition to restart the loop:
again:
list_for_each_entry_safe() {
ret = test_notify();
if (ret < 0)
return ret;
goto again;
}
I think I like this better. This considered,
Acked-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> + break;
> }
> }
>
> /* Keep also completed notifiers on the list */
> list_add(¬ifier->list, ¬ifier_list);
>
> - mutex_unlock(&list_lock);
> + if (!subnotifier)
> + mutex_unlock(&list_lock);
>
> return 0;
> }
> +
> +int v4l2_async_subnotifier_register(struct v4l2_subdev *sd,
> + struct v4l2_async_notifier *notifier)
> +{
> + return v4l2_async_do_notifier_register(sd->v4l2_dev, notifier, true);
> +}
> +EXPORT_SYMBOL(v4l2_async_subnotifier_register);
> +
> +int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> + struct v4l2_async_notifier *notifier)
> +{
> + return v4l2_async_do_notifier_register(v4l2_dev, notifier, false);
> +}
> EXPORT_SYMBOL(v4l2_async_notifier_register);
>
> -void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> +static void
> +v4l2_async_do_notifier_unregister(struct v4l2_async_notifier *notifier,
> + bool subnotifier)
> {
> struct v4l2_subdev *sd, *tmp;
> unsigned int notif_n_subdev = notifier->num_subdevs;
> @@ -216,7 +251,10 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> "Failed to allocate device cache!\n");
> }
>
> - mutex_lock(&list_lock);
> + if (subnotifier)
> + lockdep_assert_held(&list_lock);
> + else
> + mutex_lock(&list_lock);
>
> list_del(¬ifier->list);
>
> @@ -243,15 +281,20 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> put_device(d);
> }
>
> - mutex_unlock(&list_lock);
> + if (!subnotifier)
> + 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.
> + * TODO: If we are unregistering a subdevice notifier we can't reprobe
> + * since the lock_list is held by the master device and attaching that
> + * device would call v4l2_async_register_subdev() and end in a deadlock
> + * on list_lock.
> */
> - while (i--) {
> + while (i-- && !subnotifier) {
> struct device *d = dev[i];
>
> if (d && device_attach(d) < 0) {
> @@ -275,6 +318,17 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> * upon notifier registration.
> */
> }
> +
> +void v4l2_async_subnotifier_unregister(struct v4l2_async_notifier *notifier)
> +{
> + v4l2_async_do_notifier_unregister(notifier, true);
> +}
> +EXPORT_SYMBOL(v4l2_async_subnotifier_unregister);
> +
> +void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> +{
> + v4l2_async_do_notifier_unregister(notifier, false);
> +}
> EXPORT_SYMBOL(v4l2_async_notifier_unregister);
>
> int v4l2_async_register_subdev(struct v4l2_subdev *sd)
> diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> index c69d8c8a66d0093a..7d55a5b0adc86580 100644
> --- a/include/media/v4l2-async.h
> +++ b/include/media/v4l2-async.h
> @@ -105,6 +105,18 @@ struct v4l2_async_notifier {
> };
>
> /**
> + * v4l2_async_notifier_register - registers a subdevice asynchronous subnotifier
> + *
> + * @sd: pointer to &struct v4l2_subdev
> + * @notifier: pointer to &struct v4l2_async_notifier
> + *
> + * This function assumes the async list_lock is already locked, allowing
> + * it to be used from struct v4l2_subdev_internal_ops registered() callback.
> + */
> +int v4l2_async_subnotifier_register(struct v4l2_subdev *sd,
> + struct v4l2_async_notifier *notifier);
> +
> +/**
> * v4l2_async_notifier_register - registers a subdevice asynchronous notifier
> *
> * @v4l2_dev: pointer to &struct v4l2_device
> @@ -114,6 +126,16 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> struct v4l2_async_notifier *notifier);
>
> /**
> + * v4l2_async_subnotifier_unregister - unregisters a asynchronous subnotifier
> + *
> + * @notifier: pointer to &struct v4l2_async_notifier
> + *
> + * This function assumes the async list_lock is already locked, allowing
> + * it to be used from struct v4l2_subdev_internal_ops unregistered() callback.
> + */
> +void v4l2_async_subnotifier_unregister(struct v4l2_async_notifier *notifier);
> +
> +/**
> * v4l2_async_notifier_unregister - unregisters a subdevice asynchronous notifier
> *
> * @notifier: pointer to &struct v4l2_async_notifier
--
Kind regards,
Sakari Ailus
e-mail: sakari.ailus@xxxxxx XMPP: sailus@xxxxxxxxxxxxxx
