hg: jdk/jdk12: 8213231: ThreadSnapshot::_threadObj can become stale

[erik.helin at oracle.com]

Changeset: 391d671f222b
Author:    ehelin
Date:      2019-01-23 13:40 +0100
URL:       http://hg.openjdk.java.net/jdk/jdk12/rev/391d671f222b

8213231: ThreadSnapshot::_threadObj can become stale
Reviewed-by: dcubed, dholmes, rehn

! src/hotspot/share/runtime/vmOperations.cpp
! src/hotspot/share/runtime/vmOperations.hpp
! src/hotspot/share/services/management.cpp
! src/hotspot/share/services/threadService.cpp
! src/hotspot/share/services/threadService.hpp