[Intel-gfx] [PATCH 07/17] drm/i915/perf: Schedule oa_config after modifying the contexts

[Chris Wilson]

Quoting Chris Wilson (2020-03-06 13:38:42)
>  static int i915_perf_stream_enable_sync(struct i915_perf_stream *stream)
>  {
> -       struct i915_request *rq;
> +       struct i915_active *active;
> +       int err;
>  
> -       rq = stream->perf->ops.enable_metric_set(stream);
> -       if (IS_ERR(rq))
> -               return PTR_ERR(rq);
> +       active = i915_active_create();
> +       if (!active)
> +               return -ENOMEM;
>  
> -       i915_request_wait(rq, 0, MAX_SCHEDULE_TIMEOUT);
> -       i915_request_put(rq);
> +       err = stream->perf->ops.enable_metric_set(stream, active);
> +       if (err == 0)
> +               i915_active_wait(active, TASK_UNINTERRUPTIBLE);

Why UNINTERRUPTIBLE you might ask?

Because if you've demonstrated that by having scheduled the oa config
update that by not waiting for the change, the machine becomes unusable,
that seems like a risk not worth taking.

Hence why the i915_request_wait() was uninterruptible and the
i915_active_wait() keeps the uninterruptible nature.
-Chris