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[1/2] drm/mm: Fix caching of leftmost node in the interval tree

Message ID 20180219085728.7517-1-chris@chris-wilson.co.uk (mailing list archive)
State New, archived
Headers show

Commit Message

Chris Wilson Feb. 19, 2018, 8:57 a.m. UTC
When we descend the tree to find our slot, if we step to the right, we
are no longer the leftmost node.

Fixes: f808c13fd373 ("lib/interval_tree: fast overlap detection")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/drm_mm.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Comments

Joonas Lahtinen Feb. 20, 2018, 9:33 a.m. UTC | #1
Quoting Chris Wilson (2018-02-19 10:57:27)
> When we descend the tree to find our slot, if we step to the right, we
> are no longer the leftmost node.
> 
> Fixes: f808c13fd373 ("lib/interval_tree: fast overlap detection")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Davidlohr Bueso <dbueso@suse.de>
> Cc: Jérôme Glisse <jglisse@redhat.com>
> Cc: Christian König <christian.koenig@amd.com>

<SNIP>

> @@ -208,11 +209,11 @@ static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
>                 parent = rb_entry(rb, struct drm_mm_node, rb);
>                 if (parent->__subtree_last < node->__subtree_last)
>                         parent->__subtree_last = node->__subtree_last;
> -               if (node->start < parent->start)
> +               if (node->start < parent->start) {
>                         link = &parent->rb.rb_left;
> -               else {
> +               } else {
>                         link = &parent->rb.rb_right;
> -                       leftmost = true;
> +                       leftmost = false;

As this bug didn't have any functional effect, we could go with
rb_insert_augmented and not try to cache the node if the information
ends up being unused.

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Regards, Joonas
diff mbox

Patch

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 186c4e90cc1c..a351bd888a61 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -180,7 +180,7 @@  static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
 	struct drm_mm *mm = hole_node->mm;
 	struct rb_node **link, *rb;
 	struct drm_mm_node *parent;
-	bool leftmost = true;
+	bool leftmost;
 
 	node->__subtree_last = LAST(node);
 
@@ -201,6 +201,7 @@  static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
 	} else {
 		rb = NULL;
 		link = &mm->interval_tree.rb_root.rb_node;
+		leftmost = true;
 	}
 
 	while (*link) {
@@ -208,11 +209,11 @@  static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
 		parent = rb_entry(rb, struct drm_mm_node, rb);
 		if (parent->__subtree_last < node->__subtree_last)
 			parent->__subtree_last = node->__subtree_last;
-		if (node->start < parent->start)
+		if (node->start < parent->start) {
 			link = &parent->rb.rb_left;
-		else {
+		} else {
 			link = &parent->rb.rb_right;
-			leftmost = true;
+			leftmost = false;
 		}
 	}