ip: refactor ip4_mtrie to use atomic store-release

ip4_mtrie used full memory barrier compare-and-swap in set_leaf () and
set_root_leaf () even though only one thread updates the trie. Replaced
such instances of compare-and-swap with atomic store-release.

Type: refactor

Change-Id: Ic6e3c84480697915541acd16dcc630d1c436137d
Signed-off-by: Jason Zhang <jason.zhang2@arm.com>
Reviewed-by: Lijian Zhang <Lijian.Zhang@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>

diff --git a/src/vnet/ip/ip4_mtrie.c b/src/vnet/ip/ip4_mtrie.c
index be79883..380ca32 100755 (executable)
--- a/src/vnet/ip/ip4_mtrie.c
+++ b/src/vnet/ip/ip4_mtrie.c
@@ -254,8 +254,7 @@ set_ply_with_more_specific_leaf (ip4_fib_mtrie_t * m,
       else if (new_leaf_dst_address_bits >=
               ply->dst_address_bits_of_leaves[i])
        {
-         clib_atomic_cmp_and_swap (&ply->leaves[i], old_leaf, new_leaf);
-         ASSERT (ply->leaves[i] == new_leaf);
+         clib_atomic_store_rel_n (&ply->leaves[i], new_leaf);
          ply->dst_address_bits_of_leaves[i] = new_leaf_dst_address_bits;
          ply->n_non_empty_leafs += ip4_fib_mtrie_leaf_is_non_empty (ply, i);
        }
@@ -319,9 +318,7 @@ set_leaf (ip4_fib_mtrie_t * m,
 
                  old_ply->dst_address_bits_of_leaves[i] =
                    a->dst_address_length;
-                 clib_atomic_cmp_and_swap (&old_ply->leaves[i], old_leaf,
-                                           new_leaf);
-                 ASSERT (old_ply->leaves[i] == new_leaf);
+                 clib_atomic_store_rel_n (&old_ply->leaves[i], new_leaf);
 
                  old_ply->n_non_empty_leafs +=
                    ip4_fib_mtrie_leaf_is_non_empty (old_ply, i);
@@ -378,9 +375,7 @@ set_leaf (ip4_fib_mtrie_t * m,
          /* Refetch since ply_create may move pool. */
          old_ply = pool_elt_at_index (ip4_ply_pool, old_ply_index);
 
-         clib_atomic_cmp_and_swap (&old_ply->leaves[dst_byte], old_leaf,
-                                   new_leaf);
-         ASSERT (old_ply->leaves[dst_byte] == new_leaf);
+         clib_atomic_store_rel_n (&old_ply->leaves[dst_byte], new_leaf);
          old_ply->dst_address_bits_of_leaves[dst_byte] = ply_base_len;
 
          old_ply->n_non_empty_leafs +=
@@ -451,9 +446,7 @@ set_root_leaf (ip4_fib_mtrie_t * m,
                   * the new one */
                  old_ply->dst_address_bits_of_leaves[slot] =
                    a->dst_address_length;
-                 clib_atomic_cmp_and_swap (&old_ply->leaves[slot],
-                                           old_leaf, new_leaf);
-                 ASSERT (old_ply->leaves[slot] == new_leaf);
+                 clib_atomic_store_rel_n (&old_ply->leaves[slot], new_leaf);
                }
              else
                {
@@ -498,9 +491,7 @@ set_root_leaf (ip4_fib_mtrie_t * m,
                        ply_base_len);
          new_ply = get_next_ply_for_leaf (m, new_leaf);
 
-         clib_atomic_cmp_and_swap (&old_ply->leaves[dst_byte], old_leaf,
-                                   new_leaf);
-         ASSERT (old_ply->leaves[dst_byte] == new_leaf);
+         clib_atomic_store_rel_n (&old_ply->leaves[dst_byte], new_leaf);
          old_ply->dst_address_bits_of_leaves[dst_byte] = ply_base_len;
        }
       else