[jira] [Commented] (THRIFT-4004) ThreadManager deadlock when adding new task

["James E. King, III (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/THRIFT-4004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15749098#comment-15749098 ] 

James E. King, III commented on THRIFT-4004:
--------------------------------------------

Significant work went into 0.10.0 to refactor and provide unit testing for ThreadManager.  As a result we were able to turn on a number of unit tests that hadn't been running in the CI environment.  Please check the current master branch to see if your analysis still holds true.

> ThreadManager deadlock when adding new task
> -------------------------------------------
>
>                 Key: THRIFT-4004
>                 URL: https://issues.apache.org/jira/browse/THRIFT-4004
>             Project: Thrift
>          Issue Type: Bug
>          Components: C++ - Library
>    Affects Versions: 0.9.3
>            Reporter: Liu Lin 
>
> Set pendingTaskCountMax = 1. 
> Add only 1 worker into ThreadManager.
> When adding task, set timeout > 0.
> If there is no task, worker thread will sleep, because manager_->monitor_.wait(Line 259) is called in function ThreadManager::Worker::run.
> Then suppose we have 2 tasks. We add the first task by calling ThreadManager::Impl::add, which will nofity monitor_. But before manager_->monitor_.wait() returns, we call ThreadManager::Impl::add again. If ThreadManager::Impl::add gets lock mutex_ successfully, ThreadManager::Worker::run will fall asleep again because it can not lock mutex_.
> Now we have tasks_.size() == pendingTaskCountMax_, so ThreadManager::Impl::add will wait on maxMonitor_(Line 462). Becasue the worker cannot fetch a task(because it can not lock mutex_, it will not notify maxMonitor_), so ThreadManager::Impl::add will wait forever. 
> Now both the two threads wait for each other, result in deadlock. 



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