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8280454: G1: ClassLoaderData verification keeps CLDs live that causes…
… problems with VerifyDuringGC during Remark Reviewed-by: stefank, coleenp
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Thomas Schatzl
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Jun 10, 2022
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98 changes: 98 additions & 0 deletions
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test/hotspot/jtreg/runtime/ClassUnload/UnloadTestWithVerifyDuringGC.java
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/* | ||
* Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved. | ||
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
* | ||
* This code is free software; you can redistribute it and/or modify it | ||
* under the terms of the GNU General Public License version 2 only, as | ||
* published by the Free Software Foundation. | ||
* | ||
* This code is distributed in the hope that it will be useful, but WITHOUT | ||
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
* version 2 for more details (a copy is included in the LICENSE file that | ||
* accompanied this code). | ||
* | ||
* You should have received a copy of the GNU General Public License version | ||
* 2 along with this work; if not, write to the Free Software Foundation, | ||
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
* | ||
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
* or visit www.oracle.com if you need additional information or have any | ||
* questions. | ||
*/ | ||
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/* | ||
* @test Class unloading test with concurrent mark | ||
* @summary Make sure that verification during gc does not prevent class unloading | ||
* @bug 8280454 | ||
* @requires vm.gc.G1 | ||
* @requires vm.opt.final.ClassUnloading | ||
* @requires vm.opt.final.ClassUnloadingWithConcurrentMark | ||
* @modules java.base/jdk.internal.misc | ||
* @library /test/lib | ||
* @library classes | ||
* @build sun.hotspot.WhiteBox test.Empty | ||
* @run driver jdk.test.lib.helpers.ClassFileInstaller sun.hotspot.WhiteBox | ||
* @run main/othervm -Xbootclasspath/a:. -Xmn8m -XX:+UseG1GC -XX:+VerifyDuringGC -XX:+AlwaysTenure -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -Xlog:gc,class+unload=debug UnloadTestWithVerifyDuringGC | ||
*/ | ||
import sun.hotspot.WhiteBox; | ||
import jdk.test.lib.classloader.ClassUnloadCommon; | ||
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/** | ||
* Test that verifies that classes are unloaded using concurrent mark with G1 when they are no | ||
* longer reachable even when -XX:+VerifyDuringGC is enabled | ||
* | ||
* The test creates a class loader, uses the loader to load a class and creates an instance | ||
* of that class. The it nulls out all the references to the instance, class and class loader | ||
* and tries to trigger class unloading using a concurrent mark. Then it verifies that the class | ||
* is no longer loaded by the VM. | ||
*/ | ||
public class UnloadTestWithVerifyDuringGC { | ||
private static final WhiteBox wb = WhiteBox.getWhiteBox(); | ||
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private static void waitUntilConcMarkFinished() throws Exception { | ||
while (wb.g1InConcurrentMark()) { | ||
try { | ||
Thread.sleep(1); | ||
} catch (InterruptedException e) { | ||
System.out.println("Got InterruptedException while waiting for concurrent mark to finish"); | ||
throw e; | ||
} | ||
} | ||
} | ||
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private static void triggerUnloadingWithConcurrentMark() throws Exception { | ||
// Try to unload classes using concurrent mark. First wait for any currently running concurrent | ||
// cycle. | ||
waitUntilConcMarkFinished(); | ||
wb.g1StartConcMarkCycle(); | ||
waitUntilConcMarkFinished(); | ||
} | ||
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private static String className = "test.Empty"; | ||
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public static void main(String... args) throws Exception { | ||
ClassUnloadCommon.failIf(wb.isClassAlive(className), "is not expected to be alive yet"); | ||
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ClassLoader cl = ClassUnloadCommon.newClassLoader(); | ||
Class<?> c = cl.loadClass(className); | ||
Object o = c.newInstance(); | ||
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ClassUnloadCommon.failIf(!wb.isClassAlive(className), "should be live here"); | ||
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String loaderName = cl.getName(); | ||
int loadedRefcount = wb.getSymbolRefcount(loaderName); | ||
System.out.println("Refcount of symbol " + loaderName + " is " + loadedRefcount); | ||
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// Move everything into the old gen so that concurrent mark can unload. | ||
wb.youngGC(); | ||
cl = null; c = null; o = null; | ||
triggerUnloadingWithConcurrentMark(); | ||
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ClassUnloadCommon.failIf(wb.isClassAlive(className), "should have been unloaded"); | ||
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int unloadedRefcount = wb.getSymbolRefcount(loaderName); | ||
System.out.println("Refcount of symbol " + loaderName + " is " + unloadedRefcount); | ||
ClassUnloadCommon.failIf(unloadedRefcount != (loadedRefcount - 1), "Refcount must be decremented"); | ||
} | ||
} |