Thread.interrupted() is always false in debugger

[Gillespie, Oli]

There are lots of paths that clear the interrupted flag. In your example, I hit at least this one when calling Thread.currentThread from the watch panel:

```

    at java.base/java.lang.Thread.interrupted(Thread.java:1030)
    at java.base/jdk.internal.loader.Resource.getBytes(Resource.java:96)
    at java.base/jdk.internal.loader.URLClassPath$JarLoader$2.getBytes(URLClassPath.java:895)
    at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:859)
    at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760)
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681)
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:525)
    at java.base/java.lang.Class.forName0(Native Method)
    at java.base/java.lang.Class.forName(Class.java:467)

```

but the key for your example seems to be https://github.com/openjdk/jdk17u/blob/master/src/hotspot/share/prims/jvmtiRawMonitor.cpp. If you replace is_interrupted(true) with is_interrupted(false) in the 3 calls from that file, your example works as you expect. That might help your investigations.

Oli

________________________________
From: serviceability-dev <serviceability-dev-retn at openjdk.org> on behalf of Egor Ushakov <egor.ushakov at jetbrains.com>
Sent: 20 August 2024 13:32:36
To: serviceability-dev
Subject: [EXTERNAL] Thread.interrupted() is always false in debugger


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Hi everyone!

we have a long standing issue https://youtrack.jetbrains.com/issue/IDEA-169706
Maybe someone could clarify why it happens and if there's a possible workaround.
Here's the simplified test case:

public class Interruption {
    public static void main(String[] args) {
        Thread thread = Thread.currentThread();
        thread.interrupt();

        if (Thread.interrupted()) { // <----- stop on a breakpoint here
            System.out.println("Interrupted");
        } else {
            System.out.println("Not interrupted");
        }
    }
}

Obviously the program prints:
Interrupted

But if stopped on a breakpoint in the debugger, evaluation of
Thread.interrupted() always returns false.
More of that interrupted field value in the thread object is also reported as false:
[cid:part1.0kKqwZN7.J5KQ0NPA at jetbrains.com]

If interrupted method is debugged step by step it is obvious that interrupted value is true,
but the debugger continue to show it as false.

Any ideas why it could happen and how to fix it?

Thanks!
Egor




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