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drm/mm: Use clear_bit_unlock() for releasing the drm_mm_node()

A few callers need to serialise the destruction of their drm_mm_node and ensure it is removed from the drm_mm before freeing. However, to be completely sure that any access from another thread is complete before we free the struct, we require the RELEASE semantics of clear_bit_unlock(). This allows the conditional locking such as Thread A Thread B mutex_lock(mm_lock); if (drm_mm_node_allocated(node)) { drm_mm_node_remove(node); mutex_lock(mm_lock); mutex_unlock(mm_lock); if (drm_mm_node_allocated(node)) drm_mm_node_remove(node); mutex_unlock(mm_lock); } kfree(node); to serialise correctly without any lingering accesses from A to the freed node. Allocation / insertion of the node is assumed never to race with removal or eviction scanning.

Chris Wilson committed 7 years ago

Commit 3dda22d1 parent 4ee92c71 file · +6 −5Browse files

Unified · Split

drivers/gpu/drm/drm_mm.c+6−5
@@ -424,9 +424,9 @@ int drm_mm_reserve_node(struct drm_mm *mm, struct drm_mm_node *node) · 423 unmodified lines
424 424
425 node->mm = mm;425 node->mm = mm;
426 426
427 __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
427 list_add(&node->node_list, &hole->node_list);428 list_add(&node->node_list, &hole->node_list);
428 drm_mm_interval_tree_add_node(hole, node);429 drm_mm_interval_tree_add_node(hole, node);
429 __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
430 node->hole_size = 0;430 node->hole_size = 0;
431 431
432 rm_hole(hole);432 rm_hole(hole);
@@ -543,9 +543,9 @@ int drm_mm_insert_node_in_range(struct drm_mm * const mm, · 110 unmodified lines
543 node->color = color;543 node->color = color;
544 node->hole_size = 0;544 node->hole_size = 0;
545 545
546 __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
546 list_add(&node->node_list, &hole->node_list);547 list_add(&node->node_list, &hole->node_list);
547 drm_mm_interval_tree_add_node(hole, node);548 drm_mm_interval_tree_add_node(hole, node);
548 __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
549 549
550 rm_hole(hole);550 rm_hole(hole);
551 if (adj_start > hole_start)551 if (adj_start > hole_start)
@@ -589,11 +589,12 @@ void drm_mm_remove_node(struct drm_mm_node *node) · 37 unmodified lines
589 589
590 drm_mm_interval_tree_remove(node, &mm->interval_tree);590 drm_mm_interval_tree_remove(node, &mm->interval_tree);
591 list_del(&node->node_list);591 list_del(&node->node_list);
592 __clear_bit(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
593 592
594 if (drm_mm_hole_follows(prev_node))593 if (drm_mm_hole_follows(prev_node))
595 rm_hole(prev_node);594 rm_hole(prev_node);
596 add_hole(prev_node);595 add_hole(prev_node);
596
597 clear_bit_unlock(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
597}598}
598EXPORT_SYMBOL(drm_mm_remove_node);599EXPORT_SYMBOL(drm_mm_remove_node);
599 600
@@ -614,6 +615,7 @@ void drm_mm_replace_node(struct drm_mm_node *old, struct drm_mm_node *new) · 14 unmodified lines
614 615
615 *new = *old;616 *new = *old;
616 617
618 __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &new->flags);
617 list_replace(&old->node_list, &new->node_list);619 list_replace(&old->node_list, &new->node_list);
618 rb_replace_node_cached(&old->rb, &new->rb, &mm->interval_tree);620 rb_replace_node_cached(&old->rb, &new->rb, &mm->interval_tree);
619 621
@@ -627,8 +629,7 @@ void drm_mm_replace_node(struct drm_mm_node *old, struct drm_mm_node *new) · 7 unmodified lines
627 &mm->holes_addr);629 &mm->holes_addr);
628 }630 }
629 631
630 __clear_bit(DRM_MM_NODE_ALLOCATED_BIT, &old->flags);632 clear_bit_unlock(DRM_MM_NODE_ALLOCATED_BIT, &old->flags);
631 __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &new->flags);
632}633}
633EXPORT_SYMBOL(drm_mm_replace_node);634EXPORT_SYMBOL(drm_mm_replace_node);
634 635