commit 961c996c901743fb1f04c437b899476b0c0e99ab
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Apr 8 21:22:56 2010 +0200

    add locking around chipset flush

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7ff797a..16c9b74 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5047,7 +5047,10 @@ i915_gem_phys_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
 	if (ret)
 		return -EFAULT;
 
+	mutex_lock(&dev->struct_mutex);
 	drm_agp_chipset_flush(dev);
+	mutex_unlock(&dev->struct_mutex);
+
 	return 0;
 }