Re: Thread deadlock misery

"Ben Voigt" <rbv@nospam.nospam>
Tue, 13 Mar 2007 11:03:49 -0500
"PaulH" <> wrote in message

I used the critical section because I read in another post on this
group that it might be necessary despite the Interlocked() operation
being atomic. In this case it obviously doesn't help me any, so I'll
remove it. Thanks!

The Sleep() call in the transmit thread is to regulate the number of
transmissions per second. The Sleep() call in the StatCalc thread is
to regulate the number of statistical samples per second.

Below is some actual code from my transmit thread. After it sends
about 300 frames, this thread halts.

/// count of frames sent
volatile long m_nSentFrames;

// Method public static CMainFrame::TransmitThread
/// @brief Transmit unicast frames to a client at a specified rate.
/// @param TFP - [in] allocated pointer to the parameters
/// @return DWORD WINAPI - 0
/*static*/ DWORD WINAPI CMainFrame::TransmitThread( TTCB* TFP )

Declare your thread procedure properly, with a void* parameter, and use a
cast inside the function.

Never never never cast a function pointer.

   std::auto_ptr< TTCB > pATFP( TFP );

You use this pointer constantly, so place all your logic inside a member
function of class TTCB.

Then your thread procedure becomes just:

    std::auto_ptr<TTCB> pATFP( static_cast<TTCB*>(TFP) ); // might need

   WSAData wsaData = { 0 };
   WSAStartup( MAKEWORD( 2, 2 ), &wsaData );

If possible, call WSAStartup only once, from your main thread.

   // Get the address info for the DUT
   struct addrinfo *DUTAddr = NULL,
                   hints = { 0 };
   hints.ai_family = AF_UNSPEC;
   hints.ai_socktype = SOCK_DGRAM;
   hints.ai_protocol = IPPROTO_UDP;
   char cPort[ 10 ] = { 0 };
   _itoa_s( TFP->port, cPort, 9, 10 );
   if( getaddrinfo( pATFP->TFP.address, cPort, &hints, &DUTAddr ) !=
0 )

mixing TFP-> with pATFP-> ??? Isn't really a problem, just bad style.

Using a member function will eliminate issues like this.

I guess you are using getaddrinfo instead of filling in a sockaddr_in
yourself in order to handle IPv6? Looks ok.

       // error handling

   // open a UDP, DGRAM socket for the connection
   if( DUTSocket < 0 )
       // error handling

   // create an empty buffer to pad the frames to the appropriate
   std::vector< char > buffer( pATFP->TFP.size );
   WSABUF wsaBuf = { pATFP->TFP.size, &buffer.front() };

I don't know if that's guaranteed to be contiguous memory, better to use:

std::auto_ptr buffer = new char[TFP.size];

   // Throw unicast frames at the given rate & size to the DUT
   CMainFrame* pParent = reinterpret_cast< CMainFrame* >( pATFP-

pParent );

   while( pATFP->pParent->m_bRunning )

m_bRunning probably needs to be volatile too

       DWORD dwStartTime = GetTickCount();
       DWORD sent = 0;
       if( WSASendTo( DUTSocket,
                      sizeof( SOCKADDR ),

This looks wrong. sizeof(SOCKADDR) is meaningless. Isn't the actual size
available in DUTAddr?

                      NULL ) < 0 )

you're not doing overlapped I/O, so just use BSD-style sendto

           // error handling
       InterlockedIncrement( &pParent->m_nSentFrames );
       DWORD dwSleepTime = ( 1000 / pATFP->TFP.FPS ) -
( GetTickCount() - dwStartTime );
       if( dwSleepTime > 0 )
           Sleep( dwSleepTime );

What happens when GetTickCount() overflows back to zero? Also, you're
accounting for the delay in your processing, but not the variation in Sleep
times, so your overall transmit rate is lower than you think. Use a
waitable timer instead.


   // Test finished successfully, cleanup
   closesocket( DUTSocket );
   freeaddrinfo( DUTAddr );
   return 0;

If you can tell where I'm going wrong here, please let me know.

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