JDK-8221892 : ThreadPoolExecutor: Thread.isAlive() is not equivalent to not being startable
  • Type: Bug
  • Component: core-libs
  • Sub-Component: java.util.concurrent
  • Affected Version: 8,11,13
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2019-04-03
  • Updated: 2020-04-08
  • Resolved: 2019-05-02
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JDK 11 JDK 13
11.0.5Fixed 13 b20Fixed
Related Reports
Relates :  
JDK-8221657 - java.lang.Thread::setDaemon modifies the state of terminated threads
Relates :  
JDK-8221893 - ApplicationShutdownHook: Thread.isAlive() is not equivalent to not being startable
Description
As referenced by Thomas Stuefe in:

http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2019-April/033512.html

ThreadPoolExecutor.addWorker has:

 if (t.isAlive()) // precheck that t is startable
         throw new IllegalThreadStateException();

but that is not a sufficient check for being "startable" as a thread that has already terminated is "not alive". If such a thread is then "started" the code will throw IllegalThreadStateException without doing proper cleanup of the worker list.
Comments
Fix Request (11u) Fixes implementation corner case in TPE code. Applies cleanly to 11u, passes tier1, tier2.
02-07-2019
Yes, an antagonistic thread factory could return a thread that has already terminated, so the check thread.getState() == Thread.State.NEW is better.
03-04-2019