fixes #6205 handle the case where a transaction has not yet noted a locktree...

fixes #6205 handle the case where a transaction has not yet noted a locktree during the escalation callback


git-svn-id: file:///svn/toku/tokudb@54261 c7de825b-a66e-492c-adef-691d508d4ae1

src/ydb_row_lock.cc

@@ -86,8 +86,8 @@ void toku_db_txn_escalate_callback(TXNID txnid, const toku::locktree *lt, const
     //
     // If we did find the transaction, then it has not yet been removed
     // from the manager and therefore has not yet released its locks.
-    // We must be able to find and replace the range buffer associated
-    // with this locktree. This is impotant, otherwise it can grow out of
+    // We must try to replace the range buffer associated with this locktree,
+    // if it exists. This is impotant, otherwise it can grow out of
     // control (ticket 5961).
 
     if (ttxn != nullptr) {
@@ -103,13 +103,11 @@ void toku_db_txn_escalate_callback(TXNID txnid, const toku::locktree *lt, const
         // will not need to take the txn mutex, so the deadlock is avoided.
         toku_mutex_lock(&db_txn_struct_i(txn)->txn_mutex);
 
-        // We should be able to find this locktree. It was just escalated, and we had locks.
         uint32_t idx;
         txn_lt_key_ranges ranges;
         toku::omt<txn_lt_key_ranges> *map = &db_txn_struct_i(txn)->lt_map;
         int r = map->find_zero<const toku::locktree *, find_key_ranges_by_lt>(lt, &ranges, &idx);
-        invariant_zero(r);
-
+        if (r == 0) {
             // Destroy the old range buffer, create a new one, and insert the new ranges.
             //
             // We could theoretically steal the memory from the caller instead of copying
@@ -123,6 +121,14 @@ void toku_db_txn_escalate_callback(TXNID txnid, const toku::locktree *lt, const
                 ranges.buffer->append(rec.get_left_key(), rec.get_right_key());
                 iter.next();
             }
+        } else {
+            // In rare cases, we may not find the associated locktree, because we are
+            // racing with the transaction trying to add this locktree to the lt map
+            // after acquiring its first lock. The escalated lock set must be the single
+            // lock that this txnid just acquired. Do nothing here and let the txn
+            // take care of adding this locktree and range to its lt map as usual.
+            invariant(buffer.get_num_ranges() == 1);
+        }
 
         toku_mutex_unlock(&db_txn_struct_i(txn)->txn_mutex);
     }