Re: [Boost-bugs] [Boost C++ Libraries] #8967: Spurious zero bytes written and eof notifications highlight ASIO IOCP issues

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #8967: Spurious zero bytes written and eof notifications highlight ASIO IOCP issues
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-08-10 07:06:48

#8967: Spurious zero bytes written and eof notifications highlight ASIO IOCP
issues
-------------------------+-------------------------------------------------
  Reporter:              |      Owner:  chris_kohlhoff
  simoncperkins@…        |     Status:  new
      Type:  Bugs        |  Component:  asio
 Milestone:  To Be       |   Severity:  Problem
  Determined             |   Keywords:  eof GetQueuedCompletionStatus
   Version:  Boost       |  WSARecv WSASend overlapped
  1.54.0                 |
Resolution:              |
-------------------------+-------------------------------------------------

Comment (by Shane Powell <killerbee@…>):

 Hi,

 I found and fixed the same problem:
 https://svn.boost.org/trac/boost/ticket/8933


 I disagree with your patch tho as I think it's dangerous removing how the
 on_pending works.  It's there to delay the calling of the complete handler
 until after the returning of the winsock functions as they are not
 reentrant for a single socket. Removing the it completely would result in
 existing asio programs not working correctly in all situations.

 The ASIO documentation says the the complete handler is not called until
 after the call to the sockets function has returned.  This means that it's
 safe to call the next read/write cycle again.  Taking away how the
 on_pending works will mean that it's possible that you can call back into
 the read/write functions before you are allowed to, which can caused
 undefined behaviour.

 Quote from MSDN:
 WSARecv should not be called on the same socket simultaneously from
 different threads, because it can result in an unpredictable buffer order.


 Check out my patch, it's much simpler (basically it reverts the code back
 to how it used to work), as the actual bug is that on_pending should be
 calling PostQueuedCompletionStatus with the 'overlapped_contains_result'
 value so that the io completion routine knows that it's a delayed result
 rather than a real result.  Because it got changed from
 'overlapped_contains_result' to zero, the io completion routine thinks
 it's a result from a winsock type function rather than a delayed result
 where the result is stored in the overlapped structure.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8967#comment:1>
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