RFR: 8259486: Replace PreserveExceptionMark with implementation for CautiouslyPreserveExceptionMark

[Coleen Phillimore]

On Mon, 11 Jan 2021 12:55:22 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> src/hotspot/share/classfile/javaClasses.cpp line 2556:
>> 
>>> 2554: 
>>> 2555:   JavaThread* thread = JavaThread::active();
>>> 2556:   PreserveExceptionMark pm(thread);
>> 
>> The result of JavaThread::active() is not necessarily the current thread. So either the new code is wrong or else we should just be using JavaThread::current()
>
> My first iteration of this change knew there was a difference then I cleaned it up.  I'll restore the Thread::current() in the PEM constructor.

annoyingly every caller of fill_in_stack_trace has the current thread.

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PR: https://git.openjdk.java.net/jdk/pull/2007