Commit c1adf200 authored by David Howells's avatar David Howells
Browse files

Introduce rb_replace_node_rcu() 



Implement an RCU-safe variant of rb_replace_node() and rearrange
rb_replace_node() to do things in the same order.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent 1291e9d1

include/linux/rbtree.h

+2 −0
Original line number Diff line number Diff line
@@ -76,6 +76,8 @@ extern struct rb_node *rb_next_postorder(const struct rb_node *); 
/* Fast replacement of a single node without remove/rebalance/add/rebalance */

extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,

			    struct rb_root *root);

extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,

				struct rb_root *root);



static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,

				struct rb_node **rb_link)

include/linux/rbtree_augmented.h

+13 −0
Original line number Diff line number Diff line
@@ -130,6 +130,19 @@ __rb_change_child(struct rb_node *old, struct rb_node *new, 
		WRITE_ONCE(root->rb_node, new);

}



static inline void

__rb_change_child_rcu(struct rb_node *old, struct rb_node *new,

		      struct rb_node *parent, struct rb_root *root)

{

	if (parent) {

		if (parent->rb_left == old)

			rcu_assign_pointer(parent->rb_left, new);

		else

			rcu_assign_pointer(parent->rb_right, new);

	} else

		rcu_assign_pointer(root->rb_node, new);

}



extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,

	void (*augment_rotate)(struct rb_node *old, struct rb_node *new));

lib/rbtree.c

+24 −2
Original line number Diff line number Diff line
@@ -539,17 +539,39 @@ void rb_replace_node(struct rb_node *victim, struct rb_node *new, 
{

	struct rb_node *parent = rb_parent(victim);



	/* Copy the pointers/colour from the victim to the replacement */

	*new = *victim;



	/* Set the surrounding nodes to point to the replacement */

	__rb_change_child(victim, new, parent, root);

	if (victim->rb_left)

		rb_set_parent(victim->rb_left, new);

	if (victim->rb_right)

		rb_set_parent(victim->rb_right, new);

	__rb_change_child(victim, new, parent, root);

}

EXPORT_SYMBOL(rb_replace_node);



void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,

			 struct rb_root *root)

{

	struct rb_node *parent = rb_parent(victim);



	/* Copy the pointers/colour from the victim to the replacement */

	*new = *victim;



	/* Set the surrounding nodes to point to the replacement */

	if (victim->rb_left)

		rb_set_parent(victim->rb_left, new);

	if (victim->rb_right)

		rb_set_parent(victim->rb_right, new);



	/* Set the parent's pointer to the new node last after an RCU barrier

	 * so that the pointers onwards are seen to be set correctly when doing

	 * an RCU walk over the tree.

	 */

	__rb_change_child_rcu(victim, new, parent, root);

}

EXPORT_SYMBOL(rb_replace_node);

EXPORT_SYMBOL(rb_replace_node_rcu);



static struct rb_node *rb_left_deepest_node(const struct rb_node *node)

{