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 38 * @modules java.base/java.util.concurrent:open 39 * @summary Checks that ForkJoinTask thrown exceptions are not leaked. 40 * This whitebox test is sensitive to forkjoin implementation details. 41 */ 42 43import static java.util.concurrent.TimeUnit.SECONDS; 44 45import java.lang.ref.WeakReference; 46import java.lang.reflect.Field; 47import java.util.ArrayList; 48import java.util.concurrent.CountDownLatch; 49import java.util.concurrent.ForkJoinPool; 50import java.util.concurrent.ForkJoinTask; 51import java.util.concurrent.RecursiveAction; 52import java.util.function.BooleanSupplier; 53 54public class FJExceptionTableLeak { 55 static class FailingTaskException extends RuntimeException {} 56 static class FailingTask extends RecursiveAction { 57 public void compute() { throw new FailingTaskException(); } 58 } 59 60 static int bucketsInuse(Object[] exceptionTable) { 61 int count = 0; 62 for (Object x : exceptionTable) 63 if (x != null) count++; 64 return count; 65 } 66 67 public static void main(String[] args) throws Exception { 68 final ForkJoinPool pool = new ForkJoinPool(4); 69 final Field exceptionTableField = 70 ForkJoinTask.class.getDeclaredField("exceptionTable"); 71 exceptionTableField.setAccessible(true); 72 final Object[] exceptionTable = (Object[]) exceptionTableField.get(null); 73 74 if (bucketsInuse(exceptionTable) != 0) throw new AssertionError(); 75 76 final ArrayList<FailingTask> tasks = new ArrayList<>(); 77 78 // Keep submitting failing tasks until most of the exception 79 // table buckets are in use 80 do { 81 for (int i = 0; i < exceptionTable.length; i++) { 82 FailingTask task = new FailingTask(); 83 pool.execute(task); 84 tasks.add(task); // retain strong refs to all tasks, for now 85 } 86 for (FailingTask task : tasks) { 87 try { 88 task.join(); 89 throw new AssertionError("should throw"); 90 } catch (FailingTaskException success) {} 91 } 92 } while (bucketsInuse(exceptionTable) < exceptionTable.length * 3 / 4); 93 94 // Retain a strong ref to one last failing task; 95 // task.join() will trigger exception table expunging. 96 FailingTask lastTask = tasks.get(0); 97 98 // Clear all other strong refs, making exception table cleanable 99 tasks.clear(); 100 101 BooleanSupplier exceptionTableIsClean = () -> { 102 try { 103 lastTask.join(); 104 throw new AssertionError("should throw"); 105 } catch (FailingTaskException expected) {} 106 int count = bucketsInuse(exceptionTable); 107 if (count == 0) 108 throw new AssertionError("expected to find last task"); 109 return count == 1; 110 }; 111 gcAwait(exceptionTableIsClean); 112 } 113 114 // --------------- GC finalization infrastructure --------------- 115 116 /** No guarantees, but effective in practice. */ 117 static void forceFullGc() { 118 CountDownLatch finalizeDone = new CountDownLatch(1); 119 WeakReference<?> ref = new WeakReference<Object>(new Object() { 120 protected void finalize() { finalizeDone.countDown(); }}); 121 try { 122 for (int i = 0; i < 10; i++) { 123 System.gc(); 124 if (finalizeDone.await(1L, SECONDS) && ref.get() == null) { 125 System.runFinalization(); // try to pick up stragglers 126 return; 127 } 128 } 129 } catch (InterruptedException unexpected) { 130 throw new AssertionError("unexpected InterruptedException"); 131 } 132 throw new AssertionError("failed to do a \"full\" gc"); 133 } 134 135 static void gcAwait(BooleanSupplier s) { 136 for (int i = 0; i < 10; i++) { 137 if (s.getAsBoolean()) 138 return; 139 forceFullGc(); 140 } 141 throw new AssertionError("failed to satisfy condition"); 142 } 143} 144