jdk/test/hotspot/jtreg/gc/parallel/TestObjectCountAfterGC.java
Thomas Schatzl d0fd898a96 8375314: Parallel: Crash iterating over unloaded classes for ObjectCountAfterGC event
Reviewed-by: iwalulya
Backport-of: f3381f0ffe2207e1765558f6f49e5a0280a3f920
2026-01-26 09:19:14 +00:00

105 lines
4.1 KiB
Java

/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* under the terms of the GNU General Public License version 2 only, as
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*
* 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
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*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
package gc.parallel;
/*
* @test TestObjectCountAfterGC
* @bug 8375314
* @summary Verifies that the HeapInspection VM operation for the ObjectCountAfterGC JFR event does not crash the VM.
* Creates a set of custom classes that are about to be unloaded to cause metaspace to uncommit pages. When
* the execution of the heap inspection iterates over the heap, it will come across these unloaded classes
* referencing uncommitted memory, crashing.
* @requires vm.gc.Parallel
* @requires vm.opt.final.ClassUnloading
* @library /test/lib
* @library /testlibrary/asm
* @modules java.base/jdk.internal.misc
* @run main/othervm -XX:+UseParallelGC -Xlog:gc=debug,metaspace=info -XX:StartFlightRecording:gc=all,duration=1s,filename=myrecording.jfr
* gc.parallel.TestObjectCountAfterGC
*/
import java.lang.ref.Reference;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
public class TestObjectCountAfterGC {
static final String className = "ClassToLoadUnload";
public static void main(String args[]) throws Exception {
final int KEEPALIVE_LENGTH = 100;
Object[] keepalive = new Object[KEEPALIVE_LENGTH];
for (int i = 1; i < 1000; i++) {
ClassLoader cl = new MyClassLoader();
Object o = null;
// Create some random kept alive objects so that the
// compaction regions are not totally empty and the
// heap inspection VM operation needs to iterate them.
keepalive[(i / KEEPALIVE_LENGTH) % KEEPALIVE_LENGTH] = new int[100];
o = cl.loadClass(className + i).newInstance();
cl = null;
o = null;
}
// There is heap inspection VM operation for the ObjectCountAfterGC event
// when JFR stops recording.
Reference.reachabilityFence(keepalive);
}
}
class MyClassLoader extends ClassLoader {
// Create a class of the given name with a default constructor.
public byte[] createClass(String name) {
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC | Opcodes.ACC_SUPER, name, null, "java/lang/Object", null);
// Add default constructor that just calls the super class constructor.
MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>", "()V", null, null);
mv.visitCode();
mv.visitVarInsn(Opcodes.ALOAD, 0);
mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
mv.visitInsn(Opcodes.RETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
return cw.toByteArray();
}
// If the given name starts with "TestObjectCountAfterGC" create a new class on the fly,
// delegate otherwise.
public Class<?> loadClass(String name) throws ClassNotFoundException {
if (!name.startsWith(TestObjectCountAfterGC.className)) {
return super.loadClass(name);
}
byte[] cls = createClass(name);
return defineClass(name, cls, 0, cls.length, null);
}
}