Am 12.02.2018 um 18:14 schrieb Ville Syrjälä:
On Mon, Feb 12, 2018 at 02:55:33PM +0000, Chris Wilson wrote:
Use the new idr_init_base() function to create an IDR that knows id==0
is never allocated as it maps to an invalid identifier. By knowing that
id==0 is invalid, the IDR can start from id=1 instead avoiding the issue
of having to start each lookup from the zeroth leaf as id==0 is always
unused (and thus the tree-of-bitmaps indicate that is the first

References: 6ce711f27500 ("idr: Make 1-based IDRs more efficient")
Signed-off-by: Chris Wilson <>
Cc: Daniel Vetter <>
Cc: Christian Konig <>
Cc: Dave Airlie <>
Yep, looks like all of these pass start==1 to idr_alloc().
Reviewed-by: Ville Syrjälä <>

Acked-by: Christian König <> as well.

Probably going to do this for the command submission context handles in amdgpu as well.


Looks like at least tile_idr and crtc_idr could use this as well,
although I suppose they're not hit nearly as hard as the gem stuff.
Also someone should really s/crtc_idr/obj_id_idr/ or something
along those lines.

Note this requires 4.16-rc1.
  drivers/gpu/drm/drm_gem.c     | 4 ++--
  drivers/gpu/drm/drm_syncobj.c | 2 +-
  2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 01f8d9481211..4975ba9a7bc8 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -98,7 +98,7 @@ drm_gem_init(struct drm_device *dev)
        struct drm_vma_offset_manager *vma_offset_manager;
-       idr_init(&dev->object_name_idr);
+       idr_init_base(&dev->object_name_idr, 1);
vma_offset_manager = kzalloc(sizeof(*vma_offset_manager), GFP_KERNEL);
        if (!vma_offset_manager) {
@@ -776,7 +776,7 @@ drm_gem_open_ioctl(struct drm_device *dev, void *data,
  drm_gem_open(struct drm_device *dev, struct drm_file *file_private)
-       idr_init(&file_private->object_idr);
+       idr_init_base(&file_private->object_idr, 1);
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 0b7b0d1ad2d5..d4f4ce484529 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -546,7 +546,7 @@ static int drm_syncobj_export_sync_file(struct drm_file 
  drm_syncobj_open(struct drm_file *file_private)
-       idr_init(&file_private->syncobj_idr);
+       idr_init_base(&file_private->syncobj_idr, 1);

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