[Intel-gfx] [PATCH 2/2] drm/i915: Drop reference to current state wait req as soon as it goes unused

[Daniel Vetter]

On Mon, Aug 8, 2016 at 1:23 PM, Maarten Lankhorst
<maarten.lankhorst at linux.intel.com> wrote:
> There are two paths into intel_cleanup_plane_fb, the normal completion
> path and the failure path.
>
> In the failure case, intel_cleanup_plane_fb is called before
> drm_atomic_helper_swap_state, so any wait_req reference made in
> intel_prepare_plane_fb will be in old_intel_state->wait_req.
>
> In the normal completion path, wait_req is not freed until
> the next commit, which is no longer used after waiting.
>
> Free it as soon as possible, so we don't hold on to it indefinitely.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Keith Packard <keithp at keithp.com>
> Cc: Daniel Vetter <daniel.vetter at intel.com>
> Cc: David Airlie <airlied at linux.ie>
> Cc: intel-gfx at lists.freedesktop.org
> Cc: dri-devel at lists.freedesktop.org
> Fixes: 849782575325 ("drm/i915: cleanup_plane_fb: also drop reference to current state wait_req")

We still need to clean up the reference in case of failure, which
means latest in intel_plane_destroy_state(). Also hanging onto a
request isn't that evil really, why can't we just only clean up in the
destroy function?
-Daniel

> ---
>  drivers/gpu/drm/i915/intel_display.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index f56707289615..e72ad97998a4 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -13754,6 +13754,8 @@ static void intel_atomic_commit_tail(struct drm_atomic_state *state)
>                 /* EIO should be eaten, and we can't get interrupted in the
>                  * worker, and blocking commits have waited already. */
>                 WARN_ON(ret);
> +
> +               i915_gem_request_assign(&intel_plane_state->wait_req, NULL);
>         }
>
>         if (!state->legacy_cursor_update)
> @@ -14190,7 +14192,6 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
>                        const struct drm_plane_state *old_state)
>  {
>         struct drm_device *dev = plane->dev;
> -       struct intel_plane_state *intel_state = to_intel_plane_state(plane->state);
>         struct drm_i915_gem_object *old_obj = intel_fb_obj(old_state->fb);
>         struct intel_plane_state *old_intel_state =
>                 to_intel_plane_state(old_state);
> @@ -14199,7 +14200,6 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
>             !INTEL_INFO(dev)->cursor_needs_physical))
>                 intel_unpin_fb_obj(old_state->fb, old_state->rotation);
>
> -       i915_gem_request_assign(&intel_state->wait_req, NULL);
>         i915_gem_request_assign(&old_intel_state->wait_req, NULL);
>  }
>
> --
> 2.7.4
>
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch