[PATCH 1/4] drm/i915: fix ilk rc6 teardown locking

[Ben Widawsky <ben@bwidawsk.net>]

In the failure cases during rc6 initialization, both the power context
and render context may get !refcount without holding struct_mutex.

However, on rc6 disabling, the lock is held by the caller.

Added a simple parameter to control whether or not to acquire the lock.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/intel_display.c |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 49fb54f..790af25 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6541,10 +6541,13 @@ void intel_enable_clock_gating(struct drm_device *dev)
 	}
 }
 
-static void ironlake_teardown_rc6(struct drm_device *dev)
+static void ironlake_teardown_rc6(struct drm_device *dev, bool need_lock)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	if (need_lock)
+		mutex_lock(&dev->struct_mutex);
+
 	if (dev_priv->renderctx) {
 		i915_gem_object_unpin(dev_priv->renderctx);
 		drm_gem_object_unreference(&dev_priv->renderctx->base);
@@ -6556,6 +6559,9 @@ static void ironlake_teardown_rc6(struct drm_device *dev)
 		drm_gem_object_unreference(&dev_priv->pwrctx->base);
 		dev_priv->pwrctx = NULL;
 	}
+
+	if (need_lock)
+		mutex_unlock(&dev->struct_mutex);
 }
 
 static void ironlake_disable_rc6(struct drm_device *dev)
@@ -6575,7 +6581,7 @@ static void ironlake_disable_rc6(struct drm_device *dev)
 		POSTING_READ(RSTDBYCTL);
 	}
 
-	ironlake_teardown_rc6(dev);
+	ironlake_teardown_rc6(dev, false);
 }
 
 static int ironlake_setup_rc6(struct drm_device *dev)
@@ -6590,7 +6596,7 @@ static int ironlake_setup_rc6(struct drm_device *dev)
 	if (dev_priv->pwrctx == NULL)
 		dev_priv->pwrctx = intel_alloc_context_page(dev);
 	if (!dev_priv->pwrctx) {
-		ironlake_teardown_rc6(dev);
+		ironlake_teardown_rc6(dev, true);
 		return -ENOMEM;
 	}
 
@@ -6618,7 +6624,7 @@ void ironlake_enable_rc6(struct drm_device *dev)
 	 */
 	ret = BEGIN_LP_RING(6);
 	if (ret) {
-		ironlake_teardown_rc6(dev);
+		ironlake_teardown_rc6(dev, true);
 		return;
 	}
 
-- 
1.7.3.4