[RFC v2 4/8] drm/fence: allow fence waiting to be interrupted by userspace

[Gustavo Padovan <gustavo@padovan.org>]

From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

If userspace is running an synchronously atomic commit and interrupts the
atomic operation during fence_wait() it will hang until the timer expires,
so here we change the wait to be interruptible so it stop immediately when
userspace wants to quit.

Also adds the necessary error checking for fence_wait().

v2: Comment by Daniel Vetter
	- Add error checking for fence_wait()

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
---
 drivers/gpu/drm/drm_atomic_helper.c | 21 +++++++++++++++------
 include/drm/drm_atomic_helper.h     |  4 ++--
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 7bf678e..f1cfcce 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -993,13 +993,15 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_modeset_enables);
  * incoming fb's and stash it in the drm_plane_state.  This is called after
  * drm_atomic_helper_swap_state() so it uses the current plane state (and
  * just uses the atomic state to find the changed planes)
+ *
+ * Return 0 on sucess or < 0 on error.
  */
-void drm_atomic_helper_wait_for_fences(struct drm_device *dev,
-			    struct drm_atomic_state *state)
+int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
+				      struct drm_atomic_state *state)
 {
 	struct drm_plane *plane;
 	struct drm_plane_state *plane_state;
-	int i;
+	int i, ret;
 
 	for_each_plane_in_state(state, plane, plane_state, i) {
 		if (!plane->state->fence)
@@ -1007,10 +1009,14 @@ void drm_atomic_helper_wait_for_fences(struct drm_device *dev,
 
 		WARN_ON(!plane->state->fb);
 
-		fence_wait(plane->state->fence, false);
+		ret = fence_wait(plane->state->fence, true);
+		if (ret)
+			return ret;
 		fence_put(plane->state->fence);
 		plane->state->fence = NULL;
 	}
+
+	return 0;
 }
 EXPORT_SYMBOL(drm_atomic_helper_wait_for_fences);
 
@@ -1174,7 +1180,9 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 	 * current layout.
 	 */
 
-	drm_atomic_helper_wait_for_fences(dev, state);
+	ret = drm_atomic_helper_wait_for_fences(dev, state);
+	if (ret)
+		goto out;
 
 	drm_atomic_helper_commit_modeset_disables(dev, state);
 
@@ -1184,11 +1192,12 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 
 	drm_atomic_helper_wait_for_vblanks(dev, state);
 
+out:
 	drm_atomic_helper_cleanup_planes(dev, state);
 
 	drm_atomic_state_free(state);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL(drm_atomic_helper_commit);
 
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index fe9d89c..3a5d2e5 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -42,8 +42,8 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 			     struct drm_atomic_state *state,
 			     bool async);
 
-void drm_atomic_helper_wait_for_fences(struct drm_device *dev,
-					struct drm_atomic_state *state);
+int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
+				      struct drm_atomic_state *state);
 bool drm_atomic_helper_framebuffer_changed(struct drm_device *dev,
 					   struct drm_atomic_state *old_state,
 					   struct drm_crtc *crtc);
-- 
2.5.5