Daemon ThreadGroups don't work properly.
| Project: | JNode Core |
| Component: | Code |
| Category: | bug report |
| Priority: | normal |
| Assigned: | Stephen Crawley |
| Status: | closed |
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Description
It seems that the JNode implementation of the 'daemon' flag for ThreadGroup is wrong. In the GNU Classpath codebase (on Savannah), a daemon ThreadGroup is destroyed when it has no remaining active threads and no remaining child ThreadGroups. I've yet to fully test this but my initial black-box testing against the Sun 1.6 implementation confirm this.
By contrast, the JNode version deletes a daemon ThreadGroup only when the last Thread exits as a result of a Thread.stop() call. This seems to be based on a literal reading of the Sun javadocs ... but the javadocs are not definitive. Anyway, the current behaviour of daemon ThreadGroups on JNode makes them next to useless.
I'm working up a complete testcase, and will check it in in due course.
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#1
Confirmed. The attached testcase runs all 3 tests without errors on Sun JDK 1.6 but fails in the 2nd and 3rd ones on JNode.
#2
The problem was that the Thread implementation was calling add(Thread) rather than addUnstarted() on a new Thread object's ThreadGroup. This caused the ThreadGroup's 'nUnstartedThreads' count to go negative, and the later call to remove(Thread) not destroying the (daemon) ThreadGroup.
I've checked in the testcase (with a minor fix) and a bug fix to Thread.java. The SVN revision number for the bug fix is 4028.