ADDITIONAL SYSTEM INFORMATION :
Property settings:
    file.encoding = UTF-8
    file.separator = /
    java.class.path =
    java.class.version = 65.0
    java.home = /root/hotspot-21/build/linux-x86_64-server-release/jdk
    java.io.tmpdir = /tmp
    java.library.path = /usr/java/packages/lib
        /usr/lib64
        /lib64
        /lib
        /usr/lib
    java.runtime.name = OpenJDK Runtime Environment
    java.runtime.version = 21.0.10-internal-adhoc.root.hotspot-21
    java.specification.name = Java Platform API Specification
    java.specification.vendor = Oracle Corporation
    java.specification.version = 21
    java.vendor = N/A
    java.vendor.url = https://openjdk.org/
    java.vendor.url.bug = https://bugreport.java.com/bugreport/
    java.version = 21.0.10-internal
    java.version.date = 2026-01-20
    java.vm.compressedOopsMode = Zero based
    java.vm.info = mixed mode
    java.vm.name = OpenJDK 64-Bit Server VM
    java.vm.specification.name = Java Virtual Machine Specification
    java.vm.specification.vendor = Oracle Corporation
    java.vm.specification.version = 21
    java.vm.vendor = Oracle Corporation
    java.vm.version = 21.0.10-internal-adhoc.root.hotspot-21
    jdk.debug = release
    line.separator = \n
    native.encoding = ANSI_X3.4-1968
    os.arch = amd64
    os.name = Linux
    os.version = 5.15.0-60-generic
    path.separator = :
    stderr.encoding = ANSI_X3.4-1968
    stdout.encoding = ANSI_X3.4-1968
    sun.arch.data.model = 64
    sun.boot.library.path = /root/hotspot-21/build/linux-x86_64-server-release/jdk/lib
    sun.cpu.endian = little
    sun.io.unicode.encoding = UnicodeLittle
    sun.java.launcher = SUN_STANDARD
    sun.jnu.encoding = ANSI_X3.4-1968
    sun.management.compiler = HotSpot 64-Bit Tiered Compilers
    user.country = US

    user.home = /root
    user.language = en
    user.name = root

openjdk version "21.0.10-internal" 2026-01-20
OpenJDK Runtime Environment (build 21.0.10-internal-adhoc.root.hotspot-21)
OpenJDK 64-Bit Server VM (build 21.0.10-internal-adhoc.root.hotspot-21, mixed mode)


A DESCRIPTION OF THE PROBLEM :
When terminating a thread executing a tight infinite loop using `Thread.stop()`, JDK 21 will timeout (>60s), while other LTS versions (8, 11, 17) exit quickly (~0.2s).
I investigated the behavior using `-XX:+UnlockDiagnosticVMOptions -XX:+PrintCompilation`.
+ JDK 17: The logs show no "idle" related operations during execution.
+ JDK 21: The logs indicate the presence of OSR (On-Stack Replacement) compilation associated with "idle" operations, which appears to be the cause of the delay/hang.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
```
javac Test.java
java Test
```


---------- BEGIN SOURCE ----------
```
public class Test {
    static long counter = 0;

    static void idle() {
        while (true) {
            counter++;
        }
    }

    public static void main(String[] args) throws Exception {
        Thread worker = new Thread(() -> {
            try {
                idle();
            } catch (Throwable t) {
            }
        }, "worker");

        worker.start();
        worker.stop();
    }
}
```

---------- END SOURCE ----------

FREQUENCY :
ALWAYS