On 21/05/18 10:54, Sakari Ailus wrote:
> Add a new request state (UPDATING) as well as a count for updating the
> request objects. This way, several updates may take place simultaneously
> without affecting each other. The drivers (as well as frameworks) still
> must serialise access to their own data structures; what is guaranteed by
> the new state is simply correct and optimal handling of requests.
>
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> ---
> drivers/media/media-request.c | 3 ++-
> include/media/media-request.h | 53 +++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 55 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/media-request.c b/drivers/media/media-request.c
> index a1576cf528605..03e74d72241a0 100644
> --- a/drivers/media/media-request.c
> +++ b/drivers/media/media-request.c
> @@ -22,6 +22,7 @@ static const char * const request_state[] = {
> [MEDIA_REQUEST_STATE_QUEUED] = "queued",
> [MEDIA_REQUEST_STATE_COMPLETE] = "complete",
> [MEDIA_REQUEST_STATE_CLEANING] = "cleaning",
> + [MEDIA_REQUEST_STATE_UPDATING] = "updating",
> };
>
> static const char *
> @@ -385,7 +386,7 @@ int media_request_object_bind(struct media_request *req,
>
> spin_lock_irqsave(&req->lock, flags);
>
> - if (WARN_ON(req->state != MEDIA_REQUEST_STATE_IDLE))
> + if (WARN_ON(req->state != MEDIA_REQUEST_STATE_UPDATING))
> goto unlock;
I think the 'obj->req = req' etc. lines just before the spin_lock_irqsave should be
moved to after this 'if'. Otherwise there is an unexpected side-effect of calling
this function when it returns EBUSY.
>
> list_add_tail(&obj->list, &req->objects);
> diff --git a/include/media/media-request.h b/include/media/media-request.h
> index e175538d3c669..42cc6e7f6e532 100644
> --- a/include/media/media-request.h
> +++ b/include/media/media-request.h
> @@ -28,6 +28,9 @@
> * @MEDIA_REQUEST_STATE_QUEUED: Queued
> * @MEDIA_REQUEST_STATE_COMPLETE: Completed, the request is done
> * @MEDIA_REQUEST_STATE_CLEANING: Cleaning, the request is being re-inited
> + * @MEDIA_REQUEST_STATE_UPDATING: The request is being updated, i.e.
> + * request objects are being added,
> + * modified or removed
> */
> enum media_request_state {
> MEDIA_REQUEST_STATE_IDLE,
> @@ -35,6 +38,7 @@ enum media_request_state {
> MEDIA_REQUEST_STATE_QUEUED,
> MEDIA_REQUEST_STATE_COMPLETE,
> MEDIA_REQUEST_STATE_CLEANING,
> + MEDIA_REQUEST_STATE_UPDATING,
> };
>
> struct media_request_object;
> @@ -56,6 +60,7 @@ struct media_request {
> struct kref kref;
> char debug_str[TASK_COMM_LEN + 11];
> enum media_request_state state;
> + refcount_t updating_count;
> struct list_head objects;
> unsigned int num_incomplete_objects;
> struct wait_queue_head poll_wait;
> @@ -65,6 +70,54 @@ struct media_request {
> #ifdef CONFIG_MEDIA_CONTROLLER
>
> /**
> + * media_request_lock_for_update - Lock the request for updating its objects
> + *
> + * @req: The media request
> + *
> + * Use before updating a request, i.e. adding, modifying or removing a request
> + * object in it. A reference to the request must be held during the update. This
> + * usually takes place automatically through a file handle. Use
> + * @media_request_unlock_for_update when done.
> + */
> +static inline int __must_check
> +media_request_lock_for_update(struct media_request *req)
> +{
> + unsigned long flags;
> + int ret = 0;
> +
> + spin_lock_irqsave(&req->lock, flags);
> + if (req->state == MEDIA_REQUEST_STATE_IDLE ||
> + req->state == MEDIA_REQUEST_STATE_UPDATING) {
> + req->state = MEDIA_REQUEST_STATE_UPDATING;
> + refcount_inc(&req->updating_count);
> + } else {
> + ret = -EBUSY;
> + }
> + spin_unlock_irqrestore(&req->lock, flags);
> +
> + return ret;
> +}
> +
> +/**
> + * media_request_unlock_for_update - Unlock a request previously locked for
> + * update
> + *
> + * @req: The media request
> + *
> + * Unlock a request that has previously been locked using
> + * @media_request_lock_for_update.
> + */
> +static inline void media_request_unlock_for_update(struct media_request *req)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&req->lock, flags);
> + if (refcount_dec_and_test(&req->updating_count))
> + req->state = MEDIA_REQUEST_STATE_IDLE;
> + spin_unlock_irqrestore(&req->lock, flags);
> +}
This is a very nice solution. Thank you!
Regards,
Hans
> +
> +/**
> * media_request_get - Get the media request
> *
> * @req: The request
>
