We just started seeing this fail with Graal starting in jdk-24+5 when run with linux-aarch-debug with the arguments
-Xcomp -ea -esa -XX:CompileThreshold=100 -XX:+UnlockExperimentalVMOptions -server -XX:+TieredCompilation -XX:+VerifyOops -XX:+UnlockExperimentalVMOptions -XX:+UseJVMCICompiler

java.util.ConcurrentModificationException
at java.base/java.util.HashMap$KeySpliterator.forEachRemaining(HashMap.java:1721)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:570)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:560)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:265)
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:727)
at java.base/jdk.internal.util.ReferencedKeyMap.entrySet(ReferencedKeyMap.java:295)
at java.base/jdk.internal.util.ReferencedKeyTest.methods(ReferencedKeyTest.java:101)
at java.base/jdk.internal.util.ReferencedKeyTest.mapTest(ReferencedKeyTest.java:75)
at java.base/jdk.internal.util.ReferencedKeyTest.main(ReferencedKeyTest.java:49)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at com.sun.javatest.regtest.agent.MainWrapper$MainTask.run(MainWrapper.java:138)
at java.base/java.lang.Thread.run(Thread.java:1575)


Looking at ReferencedKeyMap.entrySet:

    @Override
    public Set<Entry<K, V>> entrySet() {
        removeStaleReferences();
        return filterKeySet()
                .map(k -> new AbstractMap.SimpleEntry<>(k, get(k)))
                .collect(Collectors.toSet());
    }

It seems to me that since the call to get(k) also calls removeStaleReferences(), a concurrent GC could trigger removal while building the set resulting in a ConcurrentModificationException. Shouldn't this method be calling map.get(k) directly instead? I'm unclear why it's failing with Graal though it might just be a timing a issue.