[Intel-gfx] [PATCH 31/34] drm: Simplify drm_mm scan-list manipulation
Joonas Lahtinen
joonas.lahtinen at linux.intel.com
Wed Dec 14 08:27:57 UTC 2016
On ma, 2016-12-12 at 11:53 +0000, Chris Wilson wrote:
> Since we mandate a strict reverse-order of drm_mm_scan_remove_block()
kerneldoc speaks of forward-order, so better update that.
> after drm_mm_scan_add_block() we can further simplify the list
> manipulations when generating the temporary scan-hole.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
<SNIP>
> @@ -787,13 +783,8 @@ bool drm_mm_scan_add_block(struct drm_mm_scan *scan,
> mm->scan_active++;
>
> hole = list_prev_entry(node, node_list);
> -
> - node->scanned_preceeds_hole = hole->hole_follows;
> - hole->hole_follows = 1;
> - list_del(&node->node_list);
> - node->node_list.prev = &hole->node_list;
> - node->node_list.next = &scan->prev_scanned_node->node_list;
> - scan->prev_scanned_node = node;
> + DRM_MM_BUG_ON(list_next_entry(hole, node_list) != node);
> + __list_del_entry(&node->node_list);
At least be explicit by adding a comment that we avoid poisoning the
pointers to be able to unwind.
> @@ -887,8 +878,8 @@ bool drm_mm_scan_remove_block(struct drm_mm_scan *scan,
> node->mm->scan_active--;
>
> prev_node = list_prev_entry(node, node_list);
> -
> - prev_node->hole_follows = node->scanned_preceeds_hole;
Comment might be in place here too; "node->node_list has been removed
from the list but by carefully avoiding..."
> + DRM_MM_BUG_ON(list_next_entry(prev_node, node_list) !=
> + list_next_entry(node, node_list));
> list_add(&node->node_list, &prev_node->node_list);
>
> return (node->start + node->size > scan->hit_start &&
I'm feeling bit uncanny about avoiding poisoning.
Regards, Joonas
--
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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