Fix rcuja: chain/unchain locking vs retry

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

diff --git a/rcuja/rcuja.c b/rcuja/rcuja.c
index 7402cf31f21119b26145bd7d90d0f11bc4b34637..e6e3a3e6bcc5a10dcc6f0f24354ac5d2788c0573 100644 (file)
--- a/rcuja/rcuja.c
+++ b/rcuja/rcuja.c
@@ -1013,7 +1013,7 @@ int ja_attach_node(struct cds_ja *ja,
                }
        }
 
-       if (node_flag_ptr && ja_node_ptr(*node_flag_ptr) != NULL) {
+       if (node_flag_ptr && ja_node_ptr(*node_flag_ptr)) {
                /*
                 * Target node is non-NULL: it has been updated between
                 * RCU lookup and lock acquisition. We need to re-try
@@ -1104,18 +1104,25 @@ end:
 static
 int ja_chain_node(struct cds_ja *ja,
                struct cds_ja_inode_flag *parent_node_flag,
+               struct cds_ja_inode_flag **node_flag_ptr,
                struct cds_hlist_head *head,
                struct cds_ja_node *node)
 {
        struct cds_ja_shadow_node *shadow_node;
+       int ret = 0;
 
        shadow_node = rcuja_shadow_lookup_lock(ja->ht, parent_node_flag);
        if (!shadow_node) {
                return -EAGAIN;
        }
+       if (!ja_node_ptr(*node_flag_ptr)) {
+               ret = -EAGAIN;
+               goto end;
+       }
        cds_hlist_add_head_rcu(&node->list, head);
+end:
        rcuja_shadow_unlock(shadow_node);
-       return 0;
+       return ret;
 }
 
 int cds_ja_add(struct cds_ja *ja, uint64_t key,
@@ -1186,6 +1193,7 @@ retry:
        } else {
                ret = ja_chain_node(ja,
                        parent_node_flag,
+                       node_flag_ptr,
                        (struct cds_hlist_head *) attach_node_flag_ptr,
                        new_node);
        }
@@ -1281,7 +1289,7 @@ int ja_detach_node(struct cds_ja *ja,
         * acquisition.
         */
        assert(node_flag_ptr);
-       if (ja_node_ptr(*node_flag_ptr) == NULL) {
+       if (!ja_node_ptr(*node_flag_ptr)) {
                ret = -ENOENT;
                goto end;
        }
@@ -1327,6 +1335,7 @@ end:
 static
 int ja_unchain_node(struct cds_ja *ja,
                struct cds_ja_inode_flag *parent_node_flag,
+               struct cds_ja_inode_flag **node_flag_ptr,
                struct cds_hlist_head *head,
                struct cds_ja_node *node)
 {
@@ -1337,9 +1346,13 @@ int ja_unchain_node(struct cds_ja *ja,
        shadow_node = rcuja_shadow_lookup_lock(ja->ht, parent_node_flag);
        if (!shadow_node)
                return -EAGAIN;
+       if (!ja_node_ptr(*node_flag_ptr)) {
+               ret = -EAGAIN;
+               goto end;
+       }
        /*
         * Retry if another thread removed all but one of duplicates
-        * since check (that was performed without lock).
+        * since check (this check was performed without lock).
         */
        cds_hlist_for_each_rcu(hlist_node, head, list) {
                count++;
@@ -1366,7 +1379,8 @@ int cds_ja_del(struct cds_ja *ja, uint64_t key,
        struct cds_ja_inode_flag **snapshot_ptr[JA_MAX_DEPTH];
        uint8_t snapshot_n[JA_MAX_DEPTH];
        struct cds_ja_inode_flag *node_flag;
-       struct cds_ja_inode_flag **prev_node_flag_ptr;
+       struct cds_ja_inode_flag **prev_node_flag_ptr,
+               **node_flag_ptr;
        int nr_snapshot;
        int ret;
 
@@ -1386,6 +1400,7 @@ retry:
        snapshot[nr_snapshot++] = (struct cds_ja_inode_flag *) &ja->root;
        node_flag = rcu_dereference(ja->root);
        prev_node_flag_ptr = &ja->root;
+       node_flag_ptr = &ja->root;
 
        /* Iterate on all internal levels */
        for (i = 1; i < tree_depth; i++) {
@@ -1402,7 +1417,7 @@ retry:
                snapshot[nr_snapshot++] = node_flag;
                node_flag = ja_node_get_nth(node_flag,
                        &prev_node_flag_ptr,
-                       NULL,
+                       &node_flag_ptr,
                        iter_key);
                dbg_printf("cds_ja_del iter key lookup %u finds node_flag %p, prev_node_flag_ptr %p\n",
                                (unsigned int) iter_key, node_flag,
@@ -1450,7 +1465,7 @@ retry:
                                        snapshot_n, nr_snapshot, key, node);
                } else {
                        ret = ja_unchain_node(ja, snapshot[nr_snapshot - 1],
-                               &hlist_head, match);
+                               node_flag_ptr, &hlist_head, match);
                }
        }
        /*