Segfault in CompiledMethod::is_unloading()

[Andrew Haley]

I'm seeing a segfault at

  state_is_unloading = IsUnloadingBehaviour::current()->is_unloading(this);

because

  IsUnloadingBehaviour::_current == NULL

I see IsUnloadingBehaviour::set_current called earlier by the VM thread
with NULL as its argument.

Should this segfault be impossible? If so, why?

  _is_unloading_state == 4 at this point.

Surely we should check that sUnloadingBehaviour::_current != NULL
before calling it?

The method being processed by NMethodSweeper::process_compiled_method
is:

 755674 12888     aot[ 1]   jdk.internal.reflect.Label.add(Ljdk/internal/reflect/ClassFileAssembler;SSI)V   AOTCompiledMethod

This is a complex and hard-to-reproduce test case, so if anyone
can give me a clue about what's supposed to happen I'd appreciate
it.

-- 
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
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