Buğra Gedik created THRIFT-3932:
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Summary: C++ ThreadManager has a rare termination race
Key: THRIFT-3932
URL: https://issues.apache.org/jira/browse/THRIFT-3932
Project: Thrift
Issue Type: Bug
Reporter: Buğra Gedik
Attachments: thrift-patch
{{ThreadManger::join}} calls {{stopImpl(true)}}, which in term calls
{{removeWorker(workerCount_);}}. The latter waits until {{while (workerCount_
!= workerMaxCount_)}}. In the run method, the last thread that detects
{{workerCount_ == workerMaxCount_}} notifies the {{removeWorker}} method.
However, the run method has the following additional code that is executed at
the very end:
{code}
{
Synchronized s(manager_->workerMonitor_);
manager_->deadWorkers_.insert(this->thread());
if (notifyManager) {
manager_->workerMonitor_.notify();
}
}
{code}
This is an independent synchronized block. Now assume 2 threads. One of them
has {{notifyManager=true}} as it detected the {{workerCount_ ==
workerMaxCount_}} condition earlier. It is possible that this thread gets to
execute the above code first, and the ThreadManager's {{removeWorker}} method
unblocks and eventually the ThreadManager's {{join}} returns and the object
destructed. When the other thread reaches the synchronized block above, it will
crash, as the manager is not around anymore.
Besides, the ThreadManager never joins its threads.
Attached is a small fix that alleviates the problem.
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