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From "Li-Gang Wang (JIRA)" <j...@apache.org>
Subject [jira] Created: (HARMONY-3647) Issues with native threads creation and termination
Date Fri, 13 Apr 2007 08:18:15 GMT
Issues with native threads creation and termination
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                 Key: HARMONY-3647
                 URL: https://issues.apache.org/jira/browse/HARMONY-3647
             Project: Harmony
          Issue Type: Bug
          Components: DRLVM
         Environment: Win/Linux
            Reporter: Li-Gang Wang


While I tested the native finref (finalizer & ref enqueue) thread implementation, I met
two issues about native thread creation and termination. I have only temporary workarounds
for them currently. The basic issue is how to create/terminate a native thread that has associated
java.lang.Thread object.

1.        On Win & Linux, jvmti.test failed occasionally

CAUSE: We couldn't attach finref threads as Java threads atomically with the according interface,
attach_current_thread(). The attaching action may contend some lock with the main thread.
When we ran jvmti.test, if the main thread held the lock firstly, finref threads had to run
Thread class's constructor before they were associated to a Java thread structure. This would
incur failure.

The related issue is on Jira is https://issues.apache.org/jira/browse/HARMONY-3578.

In this patch I make the main thread wait until all finref threads finish their attaching
actions.
 

2.    On Win, gc.FinAlloc test hung after it printed "PASSED" once per tens of times.

CAUSE: In vm_destroy(), finref threads are signaled to terminate and then the main thread
terminates itself. But the termination of native threads is not atomic, so sometimes finref
threads were not terminated properly and held a shared lock after termination. In this situation
when the main thread was calling Thread.detach() method to detach itself, it could not hold
the lock and was blocked.

The related issue is on Jira is https://issues.apache.org/jira/browse/HARMONY-3588.

In this patch, when VM signals finref threads to terminate, it will wait until the termination
action finishes.


With the exploration, I suspect that current design in DRLVM might require this kind of native
thread (that has associated j.l.thread object) to be treated as real Java thread, and created
in Java code. That is, it doesn't allow the VM to simply create a native thread to be associated
with a j.l.thread object. We need this kind of thread because we need them to run Java methods
(the finalizers). I guess  this should be a bug in current design, since the main thread must
be created from native thread but able to run main() method of the entry class.



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