[Intel-gfx] [PATCH] drm/atomic: Fix memleak on ERESTARTSYS during non-blocking commits, v2.

[Maarten Lankhorst]

From: "Leo (Sunpeng) Li" <sunpeng.li at amd.com>

During a non-blocking commit, it is possible to return before the
commit_tail work is queued (-ERESTARTSYS, for example).

Since a reference on the crtc commit object is obtained for the pending
vblank event when preparing the commit, the above situation will leave
us with an extra reference.

Therefore, if the commit_tail worker has not consumed the event at the
end of a commit, release it's reference.

Changes since v1:
- Also check for state->event->base.completion being set, to
  handle the case where stall_checks() fails in setup_crtc_commit().

Fixes: 24835e442f28 ("drm: reference count event->completion")
Cc: <stable at vger.kernel.org> # v4.11+
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li at amd.com>
Acked-by: Harry Wentland <harry.wentland at amd.com> #v1
Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index b16f1d69a0bb..1d43f3e85a7d 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3327,6 +3327,15 @@ EXPORT_SYMBOL(drm_atomic_helper_crtc_duplicate_state);
 void __drm_atomic_helper_crtc_destroy_state(struct drm_crtc_state *state)
 {
 	if (state->commit) {
+		/*
+		 * In the event that a non-blocking commit returns
+		 * -ERESTARTSYS before the commit_tail work is queued, we will
+		 * have an extra reference to the commit object. Release it, if
+		 * the event has not been consumed by the worker.
+		 */
+		if (state->event && state->event->base.completion)
+			drm_crtc_commit_put(state->commit);
+
 		kfree(state->commit->event);
 		state->commit->event = NULL;
 		drm_crtc_commit_put(state->commit);
-- 
2.15.1