linux-kernel - [PATCH 2/2] drm/fence: allow fence waiting to be interrupted by userspace

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Date:	Thu, 11 Aug 2016 15:39:45 -0300
From:	Gustavo Padovan <gustavo@...ovan.org>
To:	dri-devel@...ts.freedesktop.org
Cc:	linux-kernel@...r.kernel.org, Daniel Stone <daniels@...labora.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Rob Clark <robdclark@...il.com>,
	Greg Hackmann <ghackmann@...gle.com>,
	John Harrison <John.C.Harrison@...el.com>,
	laurent.pinchart@...asonboard.com, seanpaul@...gle.com,
	marcheu@...gle.com, m.chehab@...sung.com,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>
Subject: [PATCH 2/2] drm/fence: allow fence waiting to be interrupted by userspace

From: Gustavo Padovan <gustavo.padovan@...labora.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()

v3: Rebase on top of new atomic noblocking support

Signed-off-by: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
---
 drivers/gpu/drm/drm_atomic_helper.c | 29 ++++++++++++++++++++++++-----
 include/drm/drm_crtc.h              |  2 ++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index fa263b7..5e8ed15 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1018,20 +1018,31 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
 {
 	struct drm_plane *plane;
 	struct drm_plane_state *plane_state;
+	struct fence *fence;
 	int i, ret;
 
 	for_each_plane_in_state(state, plane, plane_state, i) {
-		if (!plane->state->fence)
+		if (!plane->state->fence && !plane_state->fence)
 			continue;
 
-		WARN_ON(!plane->state->fb);
+		if (state->swapped) {
+			fence = plane->state->fence;
+			WARN_ON(!plane->state->fb);
+		} else {
+			fence = plane_state->fence;
+			WARN_ON(!plane_state->fb);
+		}
 
-		ret = fence_wait(plane->state->fence, intr);
+		ret = fence_wait(fence, intr);
 		if (ret)
 			return ret;
 
-		fence_put(plane->state->fence);
-		plane->state->fence = NULL;
+		fence_put(fence);
+
+		if (state->swapped)
+			plane->state->fence = NULL;
+		else
+			plane_state->fence = NULL;
 	}
 
 	return 0;
@@ -1240,6 +1251,12 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 	if (ret)
 		return ret;
 
+	if (!nonblock) {
+		ret = drm_atomic_helper_wait_for_fences(dev, state, true);
+		if (ret)
+			return ret;
+	}
+
 	/*
 	 * This is the point of no return - everything below never fails except
 	 * when the hw goes bonghits. Which means we can commit the new state on
@@ -2009,6 +2026,8 @@ void drm_atomic_helper_swap_state(struct drm_atomic_state *state,
 		swap(state->planes[i].state, plane->state);
 		plane->state->state = NULL;
 	}
+
+	state->swapped = true;
 }
 EXPORT_SYMBOL(drm_atomic_helper_swap_state);
 
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index b618b50..99455d8 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -2032,6 +2032,7 @@ struct __drm_connnectors_state {
  * @allow_modeset: allow full modeset
  * @legacy_cursor_update: hint to enforce legacy cursor IOCTL semantics
  * @legacy_set_config: Disable conflicting encoders instead of failing with -EINVAL.
+ * @swapped: hint to inform if the state was swapped with the device state
  * @planes: pointer to array of structures with per-plane data
  * @crtcs: pointer to array of CRTC pointers
  * @num_connector: size of the @connectors and @connector_states arrays
@@ -2043,6 +2044,7 @@ struct drm_atomic_state {
 	bool allow_modeset : 1;
 	bool legacy_cursor_update : 1;
 	bool legacy_set_config : 1;
+	bool swapped : 1;
 	struct __drm_planes_state *planes;
 	struct __drm_crtcs_state *crtcs;
 	int num_connector;
-- 
2.5.5