As part of the rewrite for 5082720 special return entry points were added to the interpreter to correct the state of the fpu stack.  Stack walking the in SA has to understand this as well and changes were made there to look for the special field _call_stub_compiled_return_address and use it if it existed.  Unfortunately the SA is looking in the wrong place for the field and never finds it.  It's checking StubRoutines when in fact it should be looking for StubRoutines::x86 or StubRoutines::i486 in releases before the unifaction of the assemblers.  This results in occasional hangs when using jstack on x86.