OK, another question about the multicast.c code:
> +static struct mcast_group *mcast_find(struct mcast_port *port,
> + union ib_gid *mgid)
> +{
> + struct rb_node *node = port->table.rb_node;
> + struct mcast_group *group;
> + int ret;
> +
> + while (node) {
> + group = rb_entry(node, struct mcast_group, node);
> + ret = memcmp(mgid->raw, group->rec.mgid.raw, sizeof *mgid);
> + if (!ret)
> + return group;
> +
> + if (ret < 0)
> + node = node->rb_left;
> + else
> + node = node->rb_right;
> + }
> + return NULL;
> +}
> +
> +static struct mcast_group *mcast_insert(struct mcast_port *port,
> + struct mcast_group *group,
> + int allow_duplicates)
> +{
> + struct rb_node **link = &port->table.rb_node;
> + struct rb_node *parent = NULL;
> + struct mcast_group *cur_group;
> + int ret;
> +
> + while (*link) {
> + parent = *link;
> + cur_group = rb_entry(parent, struct mcast_group, node);
> +
> + ret = memcmp(group->rec.mgid.raw, cur_group->rec.mgid.raw,
> + sizeof group->rec.mgid);
> + if (ret < 0)
> + link = &(*link)->rb_left;
> + else if (ret > 0)
> + link = &(*link)->rb_right;
> + else if (allow_duplicates)
> + link = &(*link)->rb_left;
> + else
> + return cur_group;
> + }
> + rb_link_node(&group->node, parent, link);
> + rb_insert_color(&group->node, &port->table);
> + return NULL;
> +}
How does it work to put duplicates into the RB tree? It seems
especially strange that the lookup code does:
> + if (ret < 0)
> + node = node->rb_left;
> + else
> + node = node->rb_right;
so if ret == 0 (ie the two GIDs being tested are the same) then it
continues to traverse to the right, while the insert code does:
> + else if (allow_duplicates)
> + link = &(*link)->rb_left;
which seems to put duplicates to the left always.
Also I'd be really worried that the rebalancing code freaks out when
duplicate keys are inserted in the tree.
- R.
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