linux-kernel - [PATCH 3.16.y-ckt 126/165] drm/vmwgfx: Fix a couple of lock dependency violations

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Date:	Wed, 25 Mar 2015 14:01:39 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Thomas Hellstrom <thellstrom@...are.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 126/165] drm/vmwgfx: Fix a couple of lock dependency violations

3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Hellstrom <thellstrom@...are.com>

commit 5151adb37a5918957f4c33a8d8e7629c0fb00563 upstream.

Experimental lockdep annotation added to the TTM lock has unveiled a
couple of lock dependency violations in the vmwgfx driver. In both
cases it turns out that the device_private::reservation_sem is not
needed so the offending code is moved out of that lock.

Acked-by: Sinclair Yeh <syeh@...are.com>
Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c |  8 +++-----
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.c     | 14 +++-----------
 2 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index 87df0b3674fd..6f6fa7d2db47 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -2759,13 +2759,11 @@ int vmw_execbuf_ioctl(struct drm_device *dev, void *data,
 				  NULL, arg->command_size, arg->throttle_us,
 				  (void __user *)(unsigned long)arg->fence_rep,
 				  NULL);
-
+	ttm_read_unlock(&dev_priv->reservation_sem);
 	if (unlikely(ret != 0))
-		goto out_unlock;
+		return ret;
 
 	vmw_kms_cursor_post_execbuf(dev_priv);
 
-out_unlock:
-	ttm_read_unlock(&dev_priv->reservation_sem);
-	return ret;
+	return 0;
 }
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index bedf18c054d1..d61f6d5ae094 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -2037,23 +2037,17 @@ int vmw_kms_update_layout_ioctl(struct drm_device *dev, void *data,
 	int i;
 	struct drm_mode_config *mode_config = &dev->mode_config;
 
-	ret = ttm_read_lock(&dev_priv->reservation_sem, true);
-	if (unlikely(ret != 0))
-		return ret;
-
 	if (!arg->num_outputs) {
 		struct drm_vmw_rect def_rect = {0, 0, 800, 600};
 		vmw_du_update_layout(dev_priv, 1, &def_rect);
-		goto out_unlock;
+		return 0;
 	}
 
 	rects_size = arg->num_outputs * sizeof(struct drm_vmw_rect);
 	rects = kcalloc(arg->num_outputs, sizeof(struct drm_vmw_rect),
 			GFP_KERNEL);
-	if (unlikely(!rects)) {
-		ret = -ENOMEM;
-		goto out_unlock;
-	}
+	if (unlikely(!rects))
+		return -ENOMEM;
 
 	user_rects = (void __user *)(unsigned long)arg->rects;
 	ret = copy_from_user(rects, user_rects, rects_size);
@@ -2078,7 +2072,5 @@ int vmw_kms_update_layout_ioctl(struct drm_device *dev, void *data,
 
 out_free:
 	kfree(rects);
-out_unlock:
-	ttm_read_unlock(&dev_priv->reservation_sem);
 	return ret;
 }
--
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