Subj : Re: IOCP problem
To   : comp.programming.threads
From : SenderX
Date : Wed Jan 26 2005 06:04 pm


"SenderX" <xxx@xxx.com> wrote in message 
news:YuSdnX08G6Bg22XcRVn-rg@comcast.com...
> Go ahead and try something like this:

If found a NASTY race-condition:



>        if ( ! ReadFile
>                ( hPipe,
>                  &read_buffer,
>                  PIPE_MSG_MAX,
>                  &dwBytesRead,
>                  lpo ) )
>        {
>          DWORD err = GetLastError();
>
>          if ( err != ERROR_IO_PENDING )
>          {
>            TRACE1("ReadFile dwLastErr = %d\n", err );
>            DisconnectNamedPipe( hPipe );
>            ConnectNamedPipe( hPipe, lpo );
>            state = 0;
>            continue;
>          }
>        }
>
>        ++state;

++state is racing with another thread that could dequeue the OVERLAPPED. You 
MUST set the state "before you enqueue a completion"!


Something like this:



      if ( ! state )
      {
        ++state; // BEFORE we enqueue

        if ( ! ReadFile
                ( hPipe,
                  &read_buffer,
                  PIPE_MSG_MAX,
                  &dwBytesRead,
                  lpo ) )
        {
          DWORD err = GetLastError();

          if ( err != ERROR_IO_PENDING )
          {
            TRACE1("ReadFile dwLastErr = %d\n", err );
            DisconnectNamedPipe( hPipe );
            ConnectNamedPipe( hPipe, lpo );
            state = 0;
            continue;
          }
        }
      }

      else if ( state == 1 )
      {
        ++state; // BEFORE we enqueue

        if ( ! WriteFile
                ( hPipe,
                  "OK",
                  3,
                  &dwBytesWritten,
                  lpo ) )
        {
          DWORD err = GetLastError();

          if ( err != ERROR_IO_PENDING )
          {
            TRACE1("WriteFile dwLastErr = %d\n", err );
            DisconnectNamedPipe( hPipe );
            ConnectNamedPipe( hPipe, lpo );
            state = 0;
            continue;
          }
        }
      }

.