RFR: 8256643: Terminally deprecate ThreadGroup stop, destroy, isDestroyed,…

[Alan Bateman]

On Fri, 20 Nov 2020 14:05:09 GMT, Sean Mullan <mullan at openjdk.org> wrote:

>> This change terminally deprecates the following methods defined by java.lang.ThreadGroup 
>> 
>> - stop 
>> - destroy 
>> - isDestroyed 
>> - setDaemon 
>> - isDaemon 
>> 
>> The stop method has been deprecated since=1.2 because it is inherently unsafe. It is time to terminally deprecate this method so it can be removed in a future release. Thread.stop will be examined in a separate issue. 
>> 
>> The destroy, isDestroyed, setDaemon, isDaemon methods support the mechanism to explicitly or automatically destroy a thread group. As detailed in JDK-8252885, the mechanism to destroy thread groups is flawed and racy. Furthermore, this mechanism inhibits efforts to drop the reference from a thread group to its threads (so that thread creation, starting and termination do not need to coordinate with their thread group). These methods should be terminally deprecated so they can be degraded in a future release and eventually removed.
>> 
>> CSR with more information:  https://bugs.openjdk.java.net/browse/JDK-8256644
>
> src/java.base/share/classes/java/lang/ThreadGroup.java line 191:
> 
>> 189:      * @deprecated Destroying a thread group and its subgroups is not an atomic
>> 190:      *             operation and is inherently racy with respect to threads that
>> 191:      *             have been created but not have started. The concept of daemon
> 
> "a daemon group" sounds better to me.

The existing spec uses "daemon thread group" so I'd prefer to stick with that.

> src/java.base/share/classes/java/lang/ThreadGroup.java line 208:
> 
>> 206:      * @deprecated Destroying a thread group and its subgroups is not an atomic
>> 207:      *             operation and is inherently racy with respect to threads that
>> 208:      *             have been created but not have started. The ability to explicitly
> 
> "have not started"

Thanks, there's a typo there.

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PR: https://git.openjdk.java.net/jdk/pull/1318