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Introduce rb_replace_node_rcu()

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

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
This commit is contained in:
David Howells 2016-07-01 07:53:51 +01:00
parent 1291e9d108
commit c1adf20052
3 changed files with 40 additions and 3 deletions
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2
include/linux/rbtree.h
View File

@ -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)

13
include/linux/rbtree_augmented.h
View File

@ -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));

28
lib/rbtree.c
View File

@ -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 */
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);
/* Copy the pointers/colour from the victim to the replacement */
*new = *victim;
/* 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)
{