From 28974348022dc7c339359ffb099ec55d2c76e457 Mon Sep 17 00:00:00 2001
From: Fabian Mastenbroek <fabianishere@outlook.com>
Date: Tue, 17 Jul 2018 16:20:47 +0200
Subject: bug: Fix crashed processes from being resumed (#28)

This change fixes a bug where a process would be resumed again after it
had crashed, bringing down the kernel.

Fixes #27
---
 .../com/atlarge/opendc/omega/OmegaSimulation.kt    | 12 +++--
 .../kotlin/com/atlarge/opendc/omega/ProcessTest.kt | 61 ++++++++++++++++++++++
 2 files changed, 69 insertions(+), 4 deletions(-)
 create mode 100644 opendc-kernel-omega/src/test/kotlin/com/atlarge/opendc/omega/ProcessTest.kt

(limited to 'opendc-kernel-omega')

diff --git a/opendc-kernel-omega/src/main/kotlin/com/atlarge/opendc/omega/OmegaSimulation.kt b/opendc-kernel-omega/src/main/kotlin/com/atlarge/opendc/omega/OmegaSimulation.kt
index 4e3aa16c..fbb4a270 100644
--- a/opendc-kernel-omega/src/main/kotlin/com/atlarge/opendc/omega/OmegaSimulation.kt
+++ b/opendc-kernel-omega/src/main/kotlin/com/atlarge/opendc/omega/OmegaSimulation.kt
@@ -184,11 +184,15 @@ internal class OmegaSimulation<M>(bootstrap: Bootstrap<M>) : Simulation<M>, Boot
             }
 
             val context = envelope.destination.context ?: continue
+            val continuation = context.continuation ?: continue
 
-            if (envelope.message !is Interrupt) {
-                context.continuation.resume(envelope)
+            // Clear the continuation to prevent resuming an already resumed continuation
+            context.continuation = null
+
+            if (envelope.message is Interrupt) {
+                continuation.resumeWithException(envelope.message)
             } else {
-                context.continuation.resumeWithException(envelope.message)
+                continuation.resume(envelope)
             }
 
             context.last = time
@@ -335,7 +339,7 @@ internal class OmegaSimulation<M>(bootstrap: Bootstrap<M>) : Simulation<M>, Boot
         /**
          * The continuation to resume the execution of the process.
          */
-        lateinit var continuation: Continuation<Envelope>
+        var continuation: Continuation<Envelope>? = null
 
         /**
          * The last point in time the process has done some work.
diff --git a/opendc-kernel-omega/src/test/kotlin/com/atlarge/opendc/omega/ProcessTest.kt b/opendc-kernel-omega/src/test/kotlin/com/atlarge/opendc/omega/ProcessTest.kt
new file mode 100644
index 00000000..334dca41
--- /dev/null
+++ b/opendc-kernel-omega/src/test/kotlin/com/atlarge/opendc/omega/ProcessTest.kt
@@ -0,0 +1,61 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2018 atlarge-research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.atlarge.opendc.omega
+
+import com.atlarge.opendc.simulator.Bootstrap
+import com.atlarge.opendc.simulator.Context
+import com.atlarge.opendc.simulator.Process
+import org.junit.jupiter.api.Test
+import kotlin.coroutines.experimental.suspendCoroutine
+
+/**
+ * A test suite for processes in simulation.
+ *
+ * @author Fabian Mastenbroek (f.s.mastenbroek@student.tudelft.nl)
+ */
+internal class ProcessTest {
+    object FreezeProcess : Process<Unit, Unit> {
+        override val initialState = Unit
+        override suspend fun Context<Unit, Unit>.run() {
+            receive()
+            suspendCoroutine<Unit> {}
+        }
+    }
+
+    /**
+     * Test whether the simulation will not resume an already resumed continuation
+     * of a process.
+     */
+    @Test
+    fun `simulation will not resume frozen process`() {
+        val bootstrap: Bootstrap<Unit> = Bootstrap.create { ctx ->
+            ctx.register(FreezeProcess)
+            ctx.schedule("Hello", destination = FreezeProcess, delay = 1)
+            ctx.schedule("Hello", destination = FreezeProcess, delay = 1)
+        }
+        val simulation = OmegaKernel.create(bootstrap)
+        simulation.run()
+    }
+}
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