RFR: JDK-8277056: Combining several C2 Print* flags asserts in xmlStream::pop_tag

[Dean Long]

On Thu, 21 Apr 2022 08:16:05 GMT, Tobias Holenstein <duke at openjdk.java.net> wrote:

> > If the problem is the native --> VM transition while holding the tty lock, then how about if we enter VM mode first, then grab the tty lock?
> 
> Unfortunately, there are already `VM_ENTRY_MARK`'s for example in `dump_asm_on` -> `CallStaticJavaDirectNode::format` -> `CallStaticJavaDirectNode::format` -> `JVMState::print_method_with_lineno` -> `ciMethod:line_number_from_bci`. The `VM_ENTRY_MARK` requires the thread to be in native mode for the transition and cannot be called if it was already called before.

There are ways to fix that.  I see other methods that use GUARDED_VM_ENTRY, for example.  But maybe it's not worth it.

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PR: https://git.openjdk.java.net/jdk/pull/8203