drm: Add reference counting to drm_atomic_state

drm_atomic_state has a complicated single owner model that tracks the
single reference from allocation through to destruction on another
thread - or perhaps on a local error path. We can simplify this tracking
by using reference counting (at a cost of a few more atomics). This is
even more beneficial when the lifetime of the state becomes more
convoluted than being passed to a single worker thread for the commit.

v2: Double check !intel atomic_commit functions for missing gets
v3: Update kerneldocs

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161014121833.439-27-chris@chris-wilson.co.uk

1 files changed, 24 insertions, 74 deletions

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 36f83fe..07b432f 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1208,7 +1208,7 @@ static void commit_tail(struct drm_atomic_state *state)
 
 	drm_atomic_helper_commit_cleanup_done(state);
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 }
 
 static void commit_work(struct work_struct *work)
@@ -1290,6 +1290,7 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 	 * make sure work items don't artifically stall on each another.
 	 */
 
+	drm_atomic_state_get(state);
 	if (nonblock)
 		queue_work(system_unbound_wq, &state->commit_work);
 	else
@@ -1591,7 +1592,7 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_hw_done);
  *
  * This signals completion of the atomic update @state, including any cleanup
  * work. If used, it must be called right before calling
- * drm_atomic_state_free().
+ * drm_atomic_state_put().
  *
  * This is part of the atomic helper support for nonblocking commits, see
  * drm_atomic_helper_setup_commit() for an overview.
@@ -2114,18 +2115,13 @@ retry:
 		state->legacy_cursor_update = true;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2187,18 +2183,13 @@ retry:
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2327,18 +2318,13 @@ retry:
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2480,11 +2466,8 @@ int drm_atomic_helper_disable_all(struct drm_device *dev,
 	}
 
 	err = drm_atomic_commit(state);
-
 free:
-	if (err < 0)
-		drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return err;
 }
 EXPORT_SYMBOL(drm_atomic_helper_disable_all);
@@ -2535,7 +2518,7 @@ retry:
 
 	err = drm_atomic_helper_disable_all(dev, &ctx);
 	if (err < 0) {
-		drm_atomic_state_free(state);
+		drm_atomic_state_put(state);
 		state = ERR_PTR(err);
 		goto unlock;
 	}
@@ -2624,18 +2607,13 @@ retry:
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2684,18 +2662,13 @@ retry:
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2744,18 +2717,13 @@ retry:
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2828,18 +2796,13 @@ retry:
 	}
 
 	ret = drm_atomic_nonblocking_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2915,19 +2878,14 @@ retry:
 	crtc_state->active = active;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
 	connector->dpms = old_mode;
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -3334,7 +3292,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,
 
 free:
 	if (err < 0) {
-		drm_atomic_state_free(state);
+		drm_atomic_state_put(state);
 		state = ERR_PTR(err);
 	}
 
@@ -3449,22 +3407,14 @@ retry:
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-
-	drm_property_unreference_blob(blob);
-
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 	drm_property_unreference_blob(blob);
-
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);