[Mesa-dev] [RFC] gallium/u_queue: add barrier function

[Marek Olšák]

I think your issue is that you have self-releasing jobs with the
cleanup callback and you automatically lose fences that way, so there
is no way to wait for completion.

Since you have only 1 thread with N jobs at most, I suggest you keep
N+1 fences around (a ring of fences) that you reuse for new jobs and
keep a pointer to the most-recently-used fence. That way you know
which fence you need to wait on to make the whole queue idle.

Marek

On Mon, Jul 18, 2016 at 10:25 PM, Rob Clark <robdclark at gmail.com> wrote:
> Helper to block until all previous jobs are complete.
> ---
> So I think this might end up being useful to me in some cases.. but
> the implementation only works for a single threaded queue (which is
> all I need).  I could also just put a helper in my driver code.
>
> Opinions?
>
>  src/gallium/auxiliary/util/u_queue.c | 12 ++++++++++++
>  src/gallium/auxiliary/util/u_queue.h |  2 ++
>  2 files changed, 14 insertions(+)
>
> diff --git a/src/gallium/auxiliary/util/u_queue.c b/src/gallium/auxiliary/util/u_queue.c
> index 838464f..861faca 100644
> --- a/src/gallium/auxiliary/util/u_queue.c
> +++ b/src/gallium/auxiliary/util/u_queue.c
> @@ -242,3 +242,15 @@ util_queue_add_job(struct util_queue *queue,
>     pipe_condvar_signal(queue->has_queued_cond);
>     pipe_mutex_unlock(queue->lock);
>  }
> +
> +static void dummy_execute(void *job, int thread_index) {}
> +
> +/* blocks until all previously queued jobs complete: */
> +void util_queue_barrier(struct util_queue *queue)
> +{
> +   struct util_queue_fence fence;
> +   util_queue_fence_init(&fence);
> +   util_queue_add_job(queue, &fence /*dummy*/, &fence, dummy_execute, NULL);
> +   util_queue_job_wait(&fence);
> +   util_queue_fence_destroy(&fence);
> +}
> diff --git a/src/gallium/auxiliary/util/u_queue.h b/src/gallium/auxiliary/util/u_queue.h
> index 59646cc..8a22ee0 100644
> --- a/src/gallium/auxiliary/util/u_queue.h
> +++ b/src/gallium/auxiliary/util/u_queue.h
> @@ -85,6 +85,8 @@ void util_queue_add_job(struct util_queue *queue,
>
>  void util_queue_job_wait(struct util_queue_fence *fence);
>
> +void util_queue_barrier(struct util_queue *queue);
> +
>  /* util_queue needs to be cleared to zeroes for this to work */
>  static inline bool
>  util_queue_is_initialized(struct util_queue *queue)
> --
> 2.7.4
>