1 /* 2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. 7 * 8 * This code is distributed in the hope that it will be useful, but WITHOUT 9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 11 * version 2 for more details (a copy is included in the LICENSE file that 12 * accompanied this code). 13 * 14 * You should have received a copy of the GNU General Public License version 15 * 2 along with this work; if not, write to the Free Software Foundation, 16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 17 * 18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 19 * or visit www.oracle.com if you need additional information or have any 20 * questions. 21 */ 22 23 /* 24 * This file is available under and governed by the GNU General Public 25 * License version 2 only, as published by the Free Software Foundation. 26 * However, the following notice accompanied the original version of this 27 * file: 28 * 29 * Written by Doug Lea and Martin Buchholz with assistance from 30 * members of JCP JSR-166 Expert Group and released to the public 31 * domain, as explained at 32 * http://creativecommons.org/publicdomain/zero/1.0/ 33 */ 34 35 /* 36 * @test 37 * @bug 8004138 8205576 38 * @modules java.base/java.util.concurrent:open 39 * @run testng FJExceptionTableLeak 40 * @summary Checks that ForkJoinTask thrown exceptions are not leaked. 41 * This whitebox test is sensitive to forkjoin implementation details. 42 */ 43 44 import static org.testng.Assert.*; 45 import org.testng.annotations.Test; 46 47 import static java.util.concurrent.TimeUnit.MILLISECONDS; 48 49 import java.lang.ref.ReferenceQueue; 50 import java.lang.ref.WeakReference; 51 import java.lang.invoke.MethodHandles; 52 import java.lang.invoke.VarHandle; 53 import java.util.ArrayList; 54 import java.util.concurrent.CountDownLatch; 55 import java.util.concurrent.ForkJoinPool; 56 import java.util.concurrent.ForkJoinTask; 57 import java.util.concurrent.RecursiveAction; 58 import java.util.concurrent.ThreadLocalRandom; 59 import java.util.concurrent.locks.ReentrantLock; 60 import java.util.function.BooleanSupplier; 61 62 @Test 63 public class FJExceptionTableLeak { 64 final ThreadLocalRandom rnd = ThreadLocalRandom.current(); 65 VarHandle NEXT, EX; 66 Object[] exceptionTable; 67 ReentrantLock exceptionTableLock; 68 69 FJExceptionTableLeak() { 70 // initialize separately to allow to pass with FJ versions without table 71 } 72 73 void init() throws ReflectiveOperationException { 74 MethodHandles.Lookup lookup = MethodHandles.privateLookupIn( 75 ForkJoinTask.class, MethodHandles.lookup()); 76 Class<?> nodeClass = Class.forName( 77 ForkJoinTask.class.getName() + "$ExceptionNode"); 78 VarHandle exceptionTableHandle = lookup.findStaticVarHandle( 79 ForkJoinTask.class, "exceptionTable", arrayClass(nodeClass)); 80 VarHandle exceptionTableLockHandle = lookup.findStaticVarHandle( 81 ForkJoinTask.class, "exceptionTableLock", ReentrantLock.class); 82 exceptionTable = (Object[]) exceptionTableHandle.get(); 83 exceptionTableLock = (ReentrantLock) exceptionTableLockHandle.get(); 84 85 NEXT = lookup.findVarHandle(nodeClass, "next", nodeClass); 86 EX = lookup.findVarHandle(nodeClass, "ex", Throwable.class); 87 } 88 89 static <T> Class<T[]> arrayClass(Class<T> klazz) { 90 try { 91 return (Class<T[]>) Class.forName("[L" + klazz.getName() + ";"); 92 } catch (ReflectiveOperationException ex) { 93 throw new Error(ex); 94 } 95 } 96 97 Object next(Object node) { return NEXT.get(node); } 98 Throwable ex(Object node) { return (Throwable) EX.get(node); } 99 100 static class FailingTaskException extends RuntimeException {} 101 static class FailingTask extends RecursiveAction { 102 public void compute() { throw new FailingTaskException(); } 103 } 104 105 /** Counts all FailingTaskExceptions still recorded in exceptionTable. */ 106 int retainedExceptions() { 107 exceptionTableLock.lock(); 108 try { 109 int count = 0; 110 for (Object node : exceptionTable) 111 for (; node != null; node = next(node)) 112 if (ex(node) instanceof FailingTaskException) 113 count++; 114 return count; 115 } finally { 116 exceptionTableLock.unlock(); 117 } 118 } 119 120 @Test 121 public void exceptionTableCleanup() throws Exception { 122 try { 123 init(); 124 } catch (ReflectiveOperationException ex) { 125 return; // using FJ Version without Exception table 126 } 127 ArrayList<FailingTask> failedTasks = failedTasks(); 128 129 // Retain a strong ref to one last failing task 130 FailingTask lastTask = failedTasks.get(rnd.nextInt(failedTasks.size())); 131 132 // Clear all other strong refs, making exception table cleanable 133 failedTasks.clear(); 134 135 BooleanSupplier exceptionTableIsClean = () -> { 136 try { 137 // Trigger exception table expunging as side effect 138 lastTask.join(); 139 throw new AssertionError("should throw"); 140 } catch (FailingTaskException expected) {} 141 int count = retainedExceptions(); 142 if (count == 0) 143 throw new AssertionError("expected to find last task"); 144 return count == 1; 145 }; 146 gcAwait(exceptionTableIsClean); 147 } 148 149 /** Sequestered into a separate method to inhibit GC retention. */ 150 ArrayList<FailingTask> failedTasks() 151 throws Exception { 152 final ForkJoinPool pool = new ForkJoinPool(rnd.nextInt(1, 4)); 153 154 assertEquals(0, retainedExceptions()); 155 156 final ArrayList<FailingTask> tasks = new ArrayList<>(); 157 158 for (int i = exceptionTable.length; i--> 0; ) { 159 FailingTask task = new FailingTask(); 160 pool.execute(task); 161 tasks.add(task); // retain strong refs to all tasks, for now 162 task = null; // excessive GC retention paranoia 163 } 164 for (FailingTask task : tasks) { 165 try { 166 task.join(); 167 throw new AssertionError("should throw"); 168 } catch (FailingTaskException success) {} 169 task = null; // excessive GC retention paranoia 170 } 171 172 if (rnd.nextBoolean()) 173 gcAwait(() -> retainedExceptions() == tasks.size()); 174 175 return tasks; 176 } 177 178 // --------------- GC finalization infrastructure --------------- 179 180 /** No guarantees, but effective in practice. */ 181 static void forceFullGc() { 182 long timeoutMillis = 1000L; 183 CountDownLatch finalized = new CountDownLatch(1); 184 ReferenceQueue<Object> queue = new ReferenceQueue<>(); 185 WeakReference<Object> ref = new WeakReference<>( 186 new Object() { protected void finalize() { finalized.countDown(); }}, 187 queue); 188 try { 189 for (int tries = 3; tries--> 0; ) { 190 System.gc(); 191 if (finalized.await(timeoutMillis, MILLISECONDS) 192 && queue.remove(timeoutMillis) != null 193 && ref.get() == null) { 194 System.runFinalization(); // try to pick up stragglers 195 return; 196 } 197 timeoutMillis *= 4; 198 } 199 } catch (InterruptedException unexpected) { 200 throw new AssertionError("unexpected InterruptedException"); 201 } 202 throw new AssertionError("failed to do a \"full\" gc"); 203 } 204 205 static void gcAwait(BooleanSupplier s) { 206 for (int i = 0; i < 10; i++) { 207 if (s.getAsBoolean()) 208 return; 209 forceFullGc(); 210 } 211 throw new AssertionError("failed to satisfy condition"); 212 } 213 }