drm: Track drm_mm allocators and show leaks on shutdown

We can use the kernel's stack tracer and depot to record the allocation
site of every drm_mm user. Then on shutdown, as well as warning that
allocated nodes still reside with the drm_mm range manager, we can
display who allocated them to aide tracking down the leak.

v2: Move Kconfig around so it lies underneath the DRM options submenu.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161031090806.20073-1-chris@chris-wilson.co.uk

drivers/gpu/drm/Kconfig

@@ -33,6 +33,19 @@ config DRM_DP_AUX_CHARDEV
 	  read and write values to arbitrary DPCD registers on the DP aux
 	  channel.
 
+config DRM_DEBUG_MM
+	bool "Insert extra checks and debug info into the DRM range managers"
+	default n
+	depends on DRM
+	select STACKDEPOT
+	help
+	  Enable allocation tracking of memory manager and leak detection on
+	  shutdown.
+
+	  Recommended for driver developers only.
+
+	  If in doubt, say "N".
+
 config DRM_KMS_HELPER
 	tristate
 	depends on DRM