jdb has a probably very little used command called "threadgroup" which is used
to set the current TheadGroup. The only purpose of the current ThreadGroup is
as the default ThreadGroup to use for the "threads" command when no ThreadGroup
argument is passed to it.
"threads" prints out every thread in the ThreadGroup specified as the first
argument. If none is specified, it uses the current ThreadGroup. If the current
ThreadGroup has not yet been specified, it automatically gets set to the top
level ThreadGroup.
Once the current ThreadGroup has been set by using the threadgroup command,
it's not that obvious how to reset it back to the default. It turns out the way
to do this to set it to the "system" ThreadGroup, which is the top level
ThreadGroup (and therefore the initial current ThreadGroup).
With this enhancement I've made it so if you use the "threadgroup" command with
no argument, it resets the current ThreadGroup back to the top level
ThreadGroup ("system"). Previously with no argument it produces an error for
not specifying the ThreadGroup argument.
-------------
Commit messages:
- threadgroup with no args resets the current threadgroup back to the default.
Changes: https://git.openjdk.java.net/jdk/pull/7687/files
Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7687&range=00
Issue: https://bugs.openjdk.java.net/browse/JDK-8282641
Stats: 29 lines in 5 files changed: 14 ins; 3 del; 12 mod
Patch: https://git.openjdk.java.net/jdk/pull/7687.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/7687/head:pull/7687
PR: https://git.openjdk.java.net/jdk/pull/7687
