rcuja: API change: move rcu_head to user code

[userspace-rcu.git] / rcuja / rcuja.c

diff --git a/rcuja/rcuja.c b/rcuja/rcuja.c
index b9ece1a9e47a2e98e901bc919b5703f91e4391af..4d1f2b435a1433c44cdc3a8ae0983178000e0160 100644 (file)
--- a/rcuja/rcuja.c
+++ b/rcuja/rcuja.c
@@ -34,7 +34,6 @@
 #include <stdint.h>
 
 #include "rcuja-internal.h"
-#include "bitfield.h"
 
 #ifndef abs
 #define abs_int(a)     ((int) (a) > 0 ? (int) (a) : -((int) (a)))
@@ -1800,6 +1799,14 @@ struct cds_hlist_head cds_ja_lookup_lower_equal(struct cds_ja *ja, uint64_t key)
        }
 
        level++;
+
+       /*
+        * From this point, we are guaranteed to be able to find a
+        * "lower than" match. ja_attach_node() and ja_detach_node()
+        * both guarantee that it is not possible for a lookup to reach
+        * a dead-end.
+        */
+
        /* Find rightmost child of rightmost child (recursively). */
        for (; level < tree_depth; level++) {
                node_flag = ja_node_get_rightmost(node_flag);
@@ -1808,13 +1815,9 @@ struct cds_hlist_head cds_ja_lookup_lower_equal(struct cds_ja *ja, uint64_t key)
                        break;
        }
 
-       if (level == tree_depth) {
-               /* Last level lookup succeded. We got a "lower than" match. */
-               head.next = (struct cds_hlist_node *) node_flag;
-               return head;
-       }
+       assert(level == tree_depth);
 
-       /* No match */
+       head.next = (struct cds_hlist_node *) node_flag;
        return head;
 }
 
@@ -1829,6 +1832,12 @@ struct cds_hlist_head cds_ja_lookup_lower_equal(struct cds_ja *ja, uint64_t key)
  * parent lock (if needed).  Then we can proceed to create the new
  * branch. Publish the new branch, and release locks.
  * TODO: we currently always take the parent lock even when not needed.
+ *
+ * ja_attach_node() ensures that a lookup will _never_ see a branch that
+ * leads to a dead-end: before attaching a branch, the entire content of
+ * the new branch is populated, thus creating a cluster, before
+ * attaching the cluster to the rest of the tree, thus making it visible
+ * to lookups.
  */
 static
 int ja_attach_node(struct cds_ja *ja,
@@ -2144,6 +2153,11 @@ struct cds_ja_node *cds_ja_add_unique(struct cds_ja *ja, uint64_t key,
  * However, when a child is removed from "linear" nodes, its pointer
  * is set to NULL. We therefore check, while holding the locks, if this
  * pointer is NULL, and return -ENOENT to the caller if it is the case.
+ *
+ * ja_detach_node() ensures that a lookup will _never_ see a branch that
+ * leads to a dead-end: when removing branch, it makes sure to perform
+ * the "cut" at the highest node that has only one child, effectively
+ * replacing it with a NULL pointer.
  */
 static
 int ja_detach_node(struct cds_ja *ja,
@@ -2515,14 +2529,12 @@ ja_error:
 __attribute__((visibility("protected")))
 void rcuja_free_all_children(struct cds_ja_shadow_node *shadow_node,
                struct cds_ja_inode_flag *node_flag,
-               void (*free_node_cb)(struct rcu_head *head))
+               void (*rcu_free_node)(struct cds_ja_node *node))
 {
-       const struct rcu_flavor_struct *flavor;
        unsigned int type_index;
        struct cds_ja_inode *node;
        const struct cds_ja_type *type;
 
-       flavor = cds_lfht_rcu_flavor(shadow_node->ja->ht);
        node = ja_node_ptr(node_flag);
        assert(node != NULL);
        type_index = ja_node_type(node_flag);
@@ -2547,7 +2559,7 @@ void rcuja_free_all_children(struct cds_ja_shadow_node *shadow_node,
                                continue;
                        head.next = (struct cds_hlist_node *) iter;
                        cds_hlist_for_each_entry_safe(entry, pos, tmp, &head, list) {
-                               flavor->update_call_rcu(&entry->head, free_node_cb);
+                               rcu_free_node(entry);
                        }
                }
                break;
@@ -2575,7 +2587,7 @@ void rcuja_free_all_children(struct cds_ja_shadow_node *shadow_node,
                                        continue;
                                head.next = (struct cds_hlist_node *) iter;
                                cds_hlist_for_each_entry_safe(entry, pos, tmp, &head, list) {
-                                       flavor->update_call_rcu(&entry->head, free_node_cb);
+                                       rcu_free_node(entry);
                                }
                        }
                }
@@ -2598,7 +2610,7 @@ void rcuja_free_all_children(struct cds_ja_shadow_node *shadow_node,
                                continue;
                        head.next = (struct cds_hlist_node *) iter;
                        cds_hlist_for_each_entry_safe(entry, pos, tmp, &head, list) {
-                               flavor->update_call_rcu(&entry->head, free_node_cb);
+                               rcu_free_node(entry);
                        }
                }
                break;
@@ -2657,7 +2669,7 @@ int ja_final_checks(struct cds_ja *ja)
  * being destroyed (ensured by the caller).
  */
 int cds_ja_destroy(struct cds_ja *ja,
-               void (*free_node_cb)(struct rcu_head *head))
+               void (*rcu_free_node)(struct cds_ja_node *node))
 {
        const struct rcu_flavor_struct *flavor;
        int ret;
@@ -2665,7 +2677,7 @@ int cds_ja_destroy(struct cds_ja *ja,
        flavor = cds_lfht_rcu_flavor(ja->ht);
        rcuja_shadow_prune(ja->ht,
                RCUJA_SHADOW_CLEAR_FREE_NODE | RCUJA_SHADOW_CLEAR_FREE_LOCK,
-               free_node_cb);
+               rcu_free_node);
        flavor->thread_offline();
        ret = rcuja_delete_ht(ja->ht);
        if (ret)