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https://issues.apache.org/jira/browse/THRIFT-3891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15873442#comment-15873442
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ASF GitHub Bot commented on THRIFT-3891:
----------------------------------------

Github user nsuke commented on a diff in the pull request:

    https://github.com/apache/thrift/pull/1196#discussion_r101908093
  
    --- Diff: lib/cpp/src/thrift/server/TNonblockingServer.cpp ---
    @@ -820,9 +821,11 @@ void TNonblockingServer::TConnection::setFlags(short 
eventFlags) {
      * Closes a connection
      */
     void TNonblockingServer::TConnection::close() {
    -  // Delete the registered libevent
    -  if (event_del(&event_) == -1) {
    -    GlobalOutput.perror("TConnection::close() event_del", 
THRIFT_GET_SOCKET_ERROR);
    +  if (eventFlags_) {
    +    if (event_del(&event_) == -1) {
    --- End diff --
    
    nits: single `if` with `eventFlags_ && event_del...` ?


> TNonblockingServer configured with more than one IO threads does not always 
> return from serve() upon stop()
> -----------------------------------------------------------------------------------------------------------
>
>                 Key: THRIFT-3891
>                 URL: https://issues.apache.org/jira/browse/THRIFT-3891
>             Project: Thrift
>          Issue Type: Bug
>          Components: C++ - Library
>    Affects Versions: 0.9.3
>            Reporter: Buğra Gedik
>            Assignee: James E. King, III
>            Priority: Minor
>         Attachments: patch.diff
>
>
> Using {{TNonblockingServer}}, when the number of IO threads is > 1, there is 
> race condition in which {{stop()}} does not properly unblock {{serve()}}. 
> The problem manifests itself when {{stop()}} is called (obviously from a 
> different thread) soon after {{serve()}}. 
> The core issue is that, {{event_base_loopbreak()}} is called within the 
> {{stop()}} sequence without checking whether the IO thread has actually 
> entered its event loop. The documentation of {{event_base_loopbreak()}} says 
> (http://www.wangafu.net/~nickm/libevent-book/Ref3_eventloop.html)
> {quote}
> Note also that event_base_loopexit(base,NULL) and event_base_loopbreak(base) 
> act differently when no event loop is running: loopexit schedules the next 
> instance of the event loop to stop right after the next round of callbacks 
> are run (as if it had been invoked with EVLOOP_ONCE) whereas loopbreak only 
> stops a currently running loop, and has no effect if the event loop isn’t 
> running.
> {quote}
> Attached is a patch (against the released 0.9.3 version of the codebase).



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