stevedlawrence commented on a change in pull request #429: URL: https://github.com/apache/incubator-daffodil/pull/429#discussion_r500285272
########## File path: daffodil-runtime1/src/main/scala/org/apache/daffodil/processors/SuspensionTracker.scala ########## @@ -0,0 +1,114 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.daffodil.processors + +import scala.collection.mutable.Queue + +import org.apache.daffodil.dsom.RuntimeSchemaDefinitionError +import org.apache.daffodil.exceptions.Assert + +class SuspensionTracker { + + private val suspensionsYoung = new Queue[Suspension] + private val suspensionsOld = new Queue[Suspension] + + private val suspensionWaitYoung = 5 + private val suspensionWaitOld = 100 + + private var count: Int = 0 + + def trackSuspension(s: Suspension): Unit = { + suspensionsYoung.enqueue(s) + } + + /** + * Attempts to evaluate suspensions. Old suspensions are evaluated less + * frequently than young suspensions. Any young suspensions that fail to + * evaluate are moved to the old suspensions list. If we evaluate old + * suspensions, we attempt to evaluate them first, with the hope that their + * resolution might make the young suspensions more likely to evaluate. + */ + def evalSuspensions(): Unit = { + if (count % suspensionWaitOld == 0) { + evalSuspensionQueue(suspensionsOld) + } + if (count % suspensionWaitYoung == 0) { + evalSuspensionQueue(suspensionsYoung) + while (suspensionsYoung.nonEmpty) { + suspensionsOld.enqueue(suspensionsYoung.dequeue) + } + } + + if (count == suspensionWaitOld) { + count = 0 + } else { + count += 1 + } + } + + /** + * Evaluates all suspensions until either they are all evaluated or a + * deadlock is detected. This moves all young suspensions to the old queue, + * and evaluates all old suspensions. If the old queue is non-empty, that + * means some suspensions are blocked, likely due to a circular deadlock, and + * we output diagnostics. + */ + def requireFinal(): Unit = { + while (suspensionsYoung.nonEmpty) { + suspensionsOld.enqueue(suspensionsYoung.dequeue) + } + + evalSuspensionQueue(suspensionsOld) + + if (suspensionsOld.length == 1) { + Assert.invariantFailed("Single suspended expression making no forward progress. " + suspensionsOld(0)) Review comment: We don't have an invariant() function that accepts a string. I'll see if the invariant macro can be changed to allow a message that just defaults to empty string. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected]
