linux-kernel - [PATCH 2/2] drm/atomic: clear new_state pointers at hw

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Message-Id: <20191101180713.5470-2-robdclark@gmail.com>
Date:   Fri,  1 Nov 2019 11:07:13 -0700
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Sean Paul <seanpaul@...omium.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Rob Clark <robdclark@...omium.org>,
        Maxime Ripard <mripard@...nel.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 2/2] drm/atomic: clear new_state pointers at hw_done

From: Rob Clark <robdclark@...omium.org>

The new state should not be accessed after this point.  Clear the
pointers to make that explicit.

This makes the error corrected in the previous patch more obvious.

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/gpu/drm/drm_atomic_helper.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 732bd0ce9241..176831df8163 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -2234,13 +2234,42 @@ EXPORT_SYMBOL(drm_atomic_helper_fake_vblank);
  */
 void drm_atomic_helper_commit_hw_done(struct drm_atomic_state *old_state)
 {
+	struct drm_connector *connector;
+	struct drm_connector_state *old_conn_state, *new_conn_state;
 	struct drm_crtc *crtc;
 	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
+	struct drm_plane *plane;
+	struct drm_plane_state *old_plane_state, *new_plane_state;
 	struct drm_crtc_commit *commit;
+	struct drm_private_obj *obj;
+	struct drm_private_state *old_obj_state, *new_obj_state;
 	int i;
 
+	/*
+	 * After this point, drivers should not access the permanent modeset
+	 * state, so we also clear the new_state pointers to make this
+	 * restriction explicit.
+	 *
+	 * For the CRTC state, we do this in the same loop where we signal
+	 * hw_done, since we still need to new_crtc_state to fish out the
+	 * commit.
+	 */
+
+	for_each_oldnew_connector_in_state(old_state, connector, old_conn_state, new_conn_state, i) {
+		old_state->connectors[i].new_state = NULL;
+	}
+
+	for_each_oldnew_plane_in_state(old_state, plane, old_plane_state, new_plane_state, i) {
+		old_state->planes[i].new_state = NULL;
+	}
+
+	for_each_oldnew_private_obj_in_state(old_state, obj, old_obj_state, new_obj_state, i) {
+		old_state->private_objs[i].new_state = NULL;
+	}
+
 	for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
 		old_state->crtcs[i].new_self_refresh_active = new_crtc_state->self_refresh_active;
+		old_state->crtcs[i].new_state = NULL;
 
 		commit = new_crtc_state->commit;
 		if (!commit)
-- 
2.21.0