rcuja: document that destroy free_node_cb does not need to wait for Q.S.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/rcuja/rcuja-internal.h b/rcuja/rcuja-internal.h
index d4bc32e0f33ea8c1740fb1ce801f69b44432e574..2d3f131e7764c64f2e57448c72ee385043869e1b 100644 (file)
--- a/rcuja/rcuja-internal.h
+++ b/rcuja/rcuja-internal.h
@@ -174,7 +174,7 @@ unsigned long ja_node_type(struct cds_ja_inode_flag *node);
 __attribute__((visibility("protected")))
 void rcuja_free_all_children(struct cds_ja_shadow_node *shadow_node,
                struct cds_ja_inode_flag *node_flag,
-               void (*rcu_free_node)(struct cds_ja_node *node));
+               void (*free_node_cb)(struct cds_ja_node *node));
 
 __attribute__((visibility("protected")))
 struct cds_ja_shadow_node *rcuja_shadow_lookup_lock(struct cds_lfht *ht,
@@ -204,7 +204,7 @@ int rcuja_shadow_clear(struct cds_lfht *ht,
 __attribute__((visibility("protected")))
 void rcuja_shadow_prune(struct cds_lfht *ht,
                unsigned int flags,
-               void (*rcu_free_node)(struct cds_ja_node *node));
+               void (*free_node_cb)(struct cds_ja_node *node));
 
 __attribute__((visibility("protected")))
 struct cds_lfht *rcuja_create_ht(const struct rcu_flavor_struct *flavor);

diff --git a/rcuja/rcuja-shadow-nodes.c b/rcuja/rcuja-shadow-nodes.c
index 917c6a2038e8c11a809fb4acfd5cf69be8d57b02..718c0821407c7ba9f927342b5db4e593a2a88d13 100644 (file)
--- a/rcuja/rcuja-shadow-nodes.c
+++ b/rcuja/rcuja-shadow-nodes.c
@@ -340,26 +340,27 @@ int rcuja_shadow_clear(struct cds_lfht *ht,
         * don't let RCU JA use a node being removed.
         */
        ret = cds_lfht_del(ht, lookup_node);
-       if (!ret) {
-               if ((flags & RCUJA_SHADOW_CLEAR_FREE_NODE)
-                               && shadow_node->level) {
-                       if (flags & RCUJA_SHADOW_CLEAR_FREE_LOCK) {
-                               flavor->update_call_rcu(&shadow_node->head,
-                                       free_shadow_node_and_node_and_lock);
-                       } else {
-                               flavor->update_call_rcu(&shadow_node->head,
-                                       free_shadow_node_and_node);
-                       }
+       if (ret)
+               goto unlock;
+       if ((flags & RCUJA_SHADOW_CLEAR_FREE_NODE)
+                       && shadow_node->level) {
+               if (flags & RCUJA_SHADOW_CLEAR_FREE_LOCK) {
+                       flavor->update_call_rcu(&shadow_node->head,
+                               free_shadow_node_and_node_and_lock);
                } else {
-                       if (flags & RCUJA_SHADOW_CLEAR_FREE_LOCK) {
-                               flavor->update_call_rcu(&shadow_node->head,
-                                       free_shadow_node_and_lock);
-                       } else {
-                               flavor->update_call_rcu(&shadow_node->head,
-                                       free_shadow_node);
-                       }
+                       flavor->update_call_rcu(&shadow_node->head,
+                               free_shadow_node_and_node);
+               }
+       } else {
+               if (flags & RCUJA_SHADOW_CLEAR_FREE_LOCK) {
+                       flavor->update_call_rcu(&shadow_node->head,
+                               free_shadow_node_and_lock);
+               } else {
+                       flavor->update_call_rcu(&shadow_node->head,
+                               free_shadow_node);
                }
        }
+unlock:
        if (lookup_shadow) {
                lockret = pthread_mutex_unlock(shadow_node->lock);
                assert(!lockret);
@@ -377,7 +378,7 @@ rcu_unlock:
 __attribute__((visibility("protected")))
 void rcuja_shadow_prune(struct cds_lfht *ht,
                unsigned int flags,
-               void (*rcu_free_node)(struct cds_ja_node *node))
+               void (*free_node_cb)(struct cds_ja_node *node))
 {
        const struct rcu_flavor_struct *flavor;
        struct cds_ja_shadow_node *shadow_node;
@@ -385,37 +386,42 @@ void rcuja_shadow_prune(struct cds_lfht *ht,
        int ret, lockret;
 
        flavor = cds_lfht_rcu_flavor(ht);
+       /*
+        * Read-side lock is needed to ensure hash table node existence
+        * vs concurrent resize.
+        */
        flavor->read_lock();
        cds_lfht_for_each_entry(ht, &iter, shadow_node, ht_node) {
                lockret = pthread_mutex_lock(shadow_node->lock);
                assert(!lockret);
        
                ret = cds_lfht_del(ht, &shadow_node->ht_node);
-               if (!ret) {
-                       if ((flags & RCUJA_SHADOW_CLEAR_FREE_NODE)
-                                       && shadow_node->level) {
-                               if (shadow_node->level == shadow_node->ja->tree_depth - 1) {
-                                       rcuja_free_all_children(shadow_node,
-                                                       shadow_node->node_flag,
-                                                       rcu_free_node);
-                               }
-                               if (flags & RCUJA_SHADOW_CLEAR_FREE_LOCK) {
-                                       flavor->update_call_rcu(&shadow_node->head,
-                                               free_shadow_node_and_node_and_lock);
-                               } else {
-                                       flavor->update_call_rcu(&shadow_node->head,
-                                               free_shadow_node_and_node);
-                               }
+               if (ret)
+                       goto unlock;
+               if ((flags & RCUJA_SHADOW_CLEAR_FREE_NODE)
+                               && shadow_node->level) {
+                       if (shadow_node->level == shadow_node->ja->tree_depth - 1) {
+                               rcuja_free_all_children(shadow_node,
+                                               shadow_node->node_flag,
+                                               free_node_cb);
+                       }
+                       if (flags & RCUJA_SHADOW_CLEAR_FREE_LOCK) {
+                               flavor->update_call_rcu(&shadow_node->head,
+                                       free_shadow_node_and_node_and_lock);
+                       } else {
+                               flavor->update_call_rcu(&shadow_node->head,
+                                       free_shadow_node_and_node);
+                       }
+               } else {
+                       if (flags & RCUJA_SHADOW_CLEAR_FREE_LOCK) {
+                               flavor->update_call_rcu(&shadow_node->head,
+                                       free_shadow_node_and_lock);
                        } else {
-                               if (flags & RCUJA_SHADOW_CLEAR_FREE_LOCK) {
-                                       flavor->update_call_rcu(&shadow_node->head,
-                                               free_shadow_node_and_lock);
-                               } else {
-                                       flavor->update_call_rcu(&shadow_node->head,
-                                               free_shadow_node);
-                               }
+                               flavor->update_call_rcu(&shadow_node->head,
+                                       free_shadow_node);
                        }
                }
+       unlock:
                lockret = pthread_mutex_unlock(shadow_node->lock);
                assert(!lockret);
        }

diff --git a/rcuja/rcuja.c b/rcuja/rcuja.c
index ca72e040d7087396dfb46ed307dd7f5ff4d0ee16..81ec0a8577e8fd402c4c5368070b8ab0b93cbcfa 100644 (file)
--- a/rcuja/rcuja.c
+++ b/rcuja/rcuja.c
@@ -2630,11 +2630,12 @@ int ja_final_checks(struct cds_ja *ja)
 }
 
 /*
- * There should be no more concurrent add to the judy array while it is
- * being destroyed (ensured by the caller).
+ * There should be no more concurrent add, delete, nor look-up performed
+ * on the Judy array while it is being destroyed (ensured by the
+ * caller).
  */
 int cds_ja_destroy(struct cds_ja *ja,
-               void (*rcu_free_node)(struct cds_ja_node *node))
+               void (*free_node_cb)(struct cds_ja_node *node))
 {
        const struct rcu_flavor_struct *flavor;
        int ret;
@@ -2642,7 +2643,7 @@ 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,
-               rcu_free_node);
+               free_node_cb);
        flavor->thread_offline();
        ret = rcuja_delete_ht(ja->ht);
        if (ret)

diff --git a/urcu/rcuja.h b/urcu/rcuja.h
index 2a0de286256b46bb12dabe07d95c85151ed16ccf..421e8388eb563112c894d6897b6e990d1e772911 100644 (file)
--- a/urcu/rcuja.h
+++ b/urcu/rcuja.h
@@ -143,11 +143,13 @@ struct cds_ja *cds_ja_new(unsigned int key_bits)
  * @rcu_free_node_cb: callback performing memory free of leftover nodes.
  *
  * Returns 0 on success, negative error value on error.
- * The @rcu_free_node_cb callback should internally wait for a grace
- * period before freeing the node.
+ * There should be no more concurrent add, delete, nor look-up performed
+ * on the Judy array while it is being destroyed (ensured by the caller).
+ * There is no need for the @rcu_free_node_cb callback to wait for grace
+ * periods, since there are no more concurrent users of the Judy array.
  */
 int cds_ja_destroy(struct cds_ja *ja,
-               void (*rcu_free_node_cb)(struct cds_ja_node *node));
+               void (*free_node_cb)(struct cds_ja_node *node));
 
 /*
  * Iterate through duplicates returned by cds_ja_lookup*()