[Boost-bugs] [Boost C++ Libraries] #7552: win_iocp_io_service hangs due to a race condition

Subject: [Boost-bugs] [Boost C++ Libraries] #7552: win_iocp_io_service hangs due to a race condition
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-10-22 14:31:12

#7552: win_iocp_io_service hangs due to a race condition
-----------------------------------+----------------------------------------
 Reporter:  danielg@…              |       Owner:  chris_kohlhoff
     Type:  Bugs                   |      Status:  new           
Milestone:  To Be Determined       |   Component:  asio          
  Version:  Boost 1.49.0           |    Severity:  Regression    
 Keywords:  asio windows hang      |  
-----------------------------------+----------------------------------------
 The fix to #6321 introduced a bug that can cause the io_service to hang.

 Example code (hangs eventually):
 {{{
 int main()
 {
         for (;;)
         {
                 boost::asio::io_service ios;
                 ios.post([]{ std::cout << '.'; });

                 boost::thread_group threads;
                 for (size_t i = 0; i < 2; ++i)
                         threads.create_thread([&]{ ios.run(); });
                 threads.join_all();
         }
 }
 }}}

 Suppose that one of the threads read the posted operation, completed it
 and got to the ''work_finished'' function where it decremented
 ''outstanding_work'' to 0 and entered the ''stop'' function. Now the
 second thread starts. In the ''run'' function it sees that
 ''outstanding_work'' is 0 so it sets ''stopped'' to 1 and returns. Back in
 the first thread ''PostQueuedCompletionStatus(iocp_.handle, 0, 0, 0)''
 isn't called since ''stopped'' is already 1. ''do_one'' returns 1 and is
 called again. ''GetQueuedCompletionStatus'' returns WAIT_TIMEOUT because
 the operation queue is empty, which causes the loop to continue to the
 next iteration ad infinitum.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7552>
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