[PATCH v3 1/3] gpu/buddy: fix module_init() usage

[Koen Koning <koen.koning@linux.intel.com>]

Use subsys_initcall() instead of module_init() (which compiles to
device_initcall() for built-ins) for buddy, so its initialization code
always runs before any (built-in) drivers.
This happened to work correctly so far due to the order of linking in
the Makefiles, but this should not be relied upon.

An incorrect initialization order could lead to built-in drivers that
use the buddy allocator to run into NULL pointer dereferences due to
slab_blocks being uninitialized.

Fixes: 6387a3c4b0c4 ("drm: move the buddy allocator from i915 into common drm")
Fixes: ba110db8e1bc ("gpu: Move DRM buddy allocator one level up (part two)")
Cc: Joel Fernandes <joelagnelf@nvidia.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Peter Senna Tschudin <peter.senna@linux.intel.com>
Cc: intel-xe@lists.freedesktop.org
Cc: stable@vger.kernel.org
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Koen Koning <koen.koning@linux.intel.com>
---
 drivers/gpu/buddy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c
index 603c59a2013a..81f57fdf913b 100644
--- a/drivers/gpu/buddy.c
+++ b/drivers/gpu/buddy.c
@@ -1315,7 +1315,7 @@ static int __init gpu_buddy_module_init(void)
 	return 0;
 }

-module_init(gpu_buddy_module_init);
+subsys_initcall(gpu_buddy_module_init);
 module_exit(gpu_buddy_module_exit);

 MODULE_DESCRIPTION("GPU Buddy Allocator");
--
2.48.1