Hi Hans,
On Mon, Apr 9, 2018 at 11:21 PM Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
[snip]
> +static void media_request_clean(struct media_request *req)
> +{
> + struct media_request_object *obj, *obj_safe;
> +
> + WARN_ON(req->state != MEDIA_REQUEST_STATE_CLEANING);
> +
> + list_for_each_entry_safe(obj, obj_safe, &req->objects, list) {
> + media_request_object_unbind(obj);
> + media_request_object_put(obj);
> + }
> +
> + req->num_incomplete_objects = 0;
> + wake_up_interruptible(&req->poll_wait);
Do we intentionally wake up only one waiter here (as opposed to calling
wake_up_interruptible_all())?
> +}
> +
> +static void media_request_release(struct kref *kref)
> +{
> + struct media_request *req =
> + container_of(kref, struct media_request, kref);
> + struct media_device *mdev = req->mdev;
> + unsigned long flags;
> +
> + dev_dbg(mdev->dev, "request: release %s\n", req->debug_str);
> +
> + spin_lock_irqsave(&req->lock, flags);
> + req->state = MEDIA_REQUEST_STATE_CLEANING;
> + spin_unlock_irqrestore(&req->lock, flags);
> +
> + media_request_clean(req);
> +
> + if (mdev->ops->req_free)
> + mdev->ops->req_free(req);
> + else
> + kfree(req);
> +}
> +
> +void media_request_put(struct media_request *req)
> +{
> + kref_put(&req->kref, media_request_release);
> +}
> +EXPORT_SYMBOL_GPL(media_request_put);
> +
> +void media_request_cancel(struct media_request *req)
> +{
> + struct media_request_object *obj, *obj_safe;
> +
> + if (req->state != MEDIA_REQUEST_STATE_QUEUED)
> + return;
I can see that media_request_release() guards the state change with
req->lock. However we access the state here without holding the spinlock.
Also, should we perhaps have MEDIA_REQUEST_STATE_CANCELLED (or maybe just
reset to MEDIA_REQUEST_STATE_IDLE?), so that we can guard against calling
this multiple times?
Or perhaps we're expecting this to be called with req_queue_mutex held?
> +
> + list_for_each_entry_safe(obj, obj_safe, &req->objects, list)
> + if (obj->ops->cancel)
> + obj->ops->cancel(obj);
> +}
> +EXPORT_SYMBOL_GPL(media_request_cancel);
[snip]
> +void media_request_object_init(struct media_request_object *obj)
> +{
> + obj->ops = NULL;
> + obj->req = NULL;
> + obj->priv = NULL;
Perhaps it could make sense to pass ops and priv as arguments here? There
is probably not much value in having a request object with both set to NULL.
> + obj->completed = false;
> + INIT_LIST_HEAD(&obj->list);
> + kref_init(&obj->kref);
> +}
> +EXPORT_SYMBOL_GPL(media_request_object_init);
> +
> +void media_request_object_bind(struct media_request *req,
> + const struct media_request_object_ops *ops,
> + void *priv,
> + struct media_request_object *obj)
> +{
> + unsigned long flags;
> +
> + if (WARN_ON(!ops->release || !ops->cancel))
> + return;
> +
> + obj->req = req;
> + obj->ops = ops;
> + obj->priv = priv;
Ah, I see, they're being set here. I guess it's just the matter of how we
define the semantics.
I wonder, though, what happens with a media_request_object struct that was
allocated, initialized, but not bound to a request, because the client
terminated. We would want to call media_request_object_put(obj), but
obj->ops would be NULL.
> + spin_lock_irqsave(&req->lock, flags);
> + if (WARN_ON(req->state != MEDIA_REQUEST_STATE_IDLE))
> + goto unlock;
> + list_add_tail(&obj->list, &req->objects);
> + req->num_incomplete_objects++;
> +unlock:
> + spin_unlock_irqrestore(&req->lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(media_request_object_bind);
> +
> +void media_request_object_unbind(struct media_request_object *obj)
> +{
> + struct media_request *req = obj->req;
> + unsigned long flags;
> + bool completed = false;
> +
> + if (!req)
> + return;
No need for any locking here?
> +
> + spin_lock_irqsave(&req->lock, flags);
> + list_del(&obj->list);
> + obj->req = NULL;
> +
> + if (req->state == MEDIA_REQUEST_STATE_COMPLETE ||
> + req->state == MEDIA_REQUEST_STATE_CLEANING)
> + goto unlock;
> +
> + if (WARN_ON(req->state == MEDIA_REQUEST_STATE_QUEUEING))
> + goto unlock;
> +
> + if (WARN_ON(!req->num_incomplete_objects))
> + goto unlock;
> +
> + req->num_incomplete_objects--;
> + if (req->state == MEDIA_REQUEST_STATE_QUEUED &&
> + !req->num_incomplete_objects) {
> + req->state = MEDIA_REQUEST_STATE_COMPLETE;
> + completed = true;
> + wake_up_interruptible(&req->poll_wait);
Is this intentionally waking up only 1 waiter?
> + }
> +unlock:
> + spin_unlock_irqrestore(&req->lock, flags);
> + if (obj->ops->unbind)
> + obj->ops->unbind(obj);
> + if (completed)
> + media_request_put(req);
> +}
> +EXPORT_SYMBOL_GPL(media_request_object_unbind);
> +
> +void media_request_object_complete(struct media_request_object *obj)
> +{
> + struct media_request *req = obj->req;
> + unsigned long flags;
> + bool completed = false;
> +
> + spin_lock_irqsave(&req->lock, flags);
> + if (obj->completed)
> + goto unlock;
> + obj->completed = true;
> + if (WARN_ON(!req->num_incomplete_objects) ||
> + WARN_ON(req->state != MEDIA_REQUEST_STATE_QUEUED))
> + goto unlock;
> +
> + if (!--req->num_incomplete_objects) {
> + req->state = MEDIA_REQUEST_STATE_COMPLETE;
> + wake_up_interruptible(&req->poll_wait);
Is this intentionally waking up only 1 waiter?
> + completed = true;
> + }
> +unlock:
> + spin_unlock_irqrestore(&req->lock, flags);
> + if (completed)
> + media_request_put(req);
> }
> +EXPORT_SYMBOL_GPL(media_request_object_complete);
> diff --git a/include/media/media-request.h b/include/media/media-request.h
> index dae3eccd9aa7..082c3cae04ac 100644
> --- a/include/media/media-request.h
> +++ b/include/media/media-request.h
> @@ -16,7 +16,163 @@
> #include <media/media-device.h>
> +enum media_request_state {
> + MEDIA_REQUEST_STATE_IDLE,
> + MEDIA_REQUEST_STATE_QUEUEING,
> + MEDIA_REQUEST_STATE_QUEUED,
> + MEDIA_REQUEST_STATE_COMPLETE,
> + MEDIA_REQUEST_STATE_CLEANING,
> +};
> +
> +struct media_request_object;
> +
> +/**
> + * struct media_request - Media device request
> + * @mdev: Media device this request belongs to
> + * @kref: Reference count
> + * @debug_prefix: Prefix for debug messages (process name:fd)
debug_str?
> + * @state: The state of the request
> + * @objects: List of @struct media_request_object request objects
> + * @num_objects: The number objects in the request
> + * @num_completed_objects: The number of completed objects in the request
num_incomplete_objects?
> + * @poll_wait: Wait queue for poll
> + * @lock: Serializes access to this struct
Does it have to be acquired to access any field?
> + */
> +struct media_request {
> + struct media_device *mdev;
> + struct kref kref;
> + char debug_str[TASK_COMM_LEN + 11];
> + enum media_request_state state;
> + struct list_head objects;
> + unsigned int num_incomplete_objects;
> + struct wait_queue_head poll_wait;
> + spinlock_t lock;
> +};
> +
> +#ifdef CONFIG_MEDIA_CONTROLLER
> +
> +static inline void media_request_get(struct media_request *req)
> +{
> + kref_get(&req->kref);
> +}
> +
> +void media_request_put(struct media_request *req);
> +void media_request_cancel(struct media_request *req);
> +
> int media_request_alloc(struct media_device *mdev,
> struct media_request_alloc *alloc);
> +#else
> +static inline void media_request_get(struct media_request *req)
> +{
> +}
> +
> +static inline void media_request_put(struct media_request *req)
> +{
> +}
> +
> +static inline void media_request_cancel(struct media_request *req)
> +{
> +}
> +
> +#endif
> +
Documentation. (Disclaimer from cover letter acknowledged, though. Just
marking.)
> +struct media_request_object_ops {
> + int (*prepare)(struct media_request_object *object);
> + void (*unprepare)(struct media_request_object *object);
> + void (*queue)(struct media_request_object *object);
> + void (*unbind)(struct media_request_object *object);
> + void (*cancel)(struct media_request_object *object);
> + void (*release)(struct media_request_object *object);
> +};
> +
> +/**
> + * struct media_request_object - An opaque object that belongs to a media
> + * request
> + *
ops
> + * @priv: object's priv pointer
req
> + * @list: List entry of the object for @struct media_request
> + * @kref: Reference count of the object, acquire before releasing
req->lock
completed
> + *
> + * An object related to the request. This struct is embedded in the
> + * larger object data.
> + */
> +struct media_request_object {
> + const struct media_request_object_ops *ops;
> + void *priv;
> + struct media_request *req;
> + struct list_head list;
> + struct kref kref;
> + bool completed;
> +};
> +
> +#ifdef CONFIG_MEDIA_CONTROLLER
> +static inline void media_request_object_get(struct media_request_object
*obj)
> +{
> + kref_get(&obj->kref);
> +}
> +
> +/**
> + * media_request_object_put - Put a media request object
> + *
> + * @obj: The object
> + *
> + * Put a media request object. Once all references are gone, the
> + * object's memory is released.
> + */
> +void media_request_object_put(struct media_request_object *obj);
> +
> +/**
> + * media_request_object_init - Initialise a media request object
> + *
> + * Initialise a media request object. The object will be released using
the
> + * release callback of the ops once it has no references (this function
> + * initialises references to one).
> + */
> +void media_request_object_init(struct media_request_object *obj);
> +
> +/**
> + * media_request_object_bind - Bind a media request object to a request
> + */
> +void media_request_object_bind(struct media_request *req,
> + const struct media_request_object_ops *ops,
> + void *priv,
> + struct media_request_object *obj);
> +
> +void media_request_object_unbind(struct media_request_object *obj);
> +
> +/**
> + * media_request_object_complete - Mark the media request object as
complete
> + */
> +void media_request_object_complete(struct media_request_object *obj);
> +#else
> +static inline void media_request_object_get(struct media_request_object
*obj)
> +{
> +}
> +
> +static inline void media_request_object_put(struct media_request_object
*obj)
> +{
> +}
> +
> +static inline void media_request_object_init(struct media_request_object
*obj)
> +{
> + obj->ops = NULL;
> + obj->req = NULL;
Hmm. Do we need to do anything here if !defined(CONFIG_MEDIA_CONTROLLER)?
Best regards,
Tomasz
