Databases
StackOverflow2013
Postsdbo
POSerial Port Receive Thread Not Behaving as Expected - C++
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POSerial Port Receive Thread Not Behaving as Expected - C++
    primarykey
    data
    text
    <p>My application uses a separate thread for handling received serial data asynchronously. The PC gets into the receive-handler as expected, but from there things go weird.</p> <p>This is my thread function:</p> <pre><code>// Create event for OVERLAPPED structure. s_ov.hEvent = ::CreateEvent( NULL, // No security TRUE, // Create a manual-reset event object FALSE, // Initial state is non-signaled NULL // No name specified ); // Load event handles. pHandles[0] = s_hSerialPortRxThreadExitEvent; while ( bContinue ) { if ( !::WaitCommEvent( s_hSerialPort, &amp;dwEventMask, &amp;s_ov ) ) { if ( ::GetLastError() != ERROR_IO_PENDING ) { TRACE(_T("SerialPortRxThreadFn : Call to WaitCommEvent failed.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ::GetLastError(), __WFILE__, __LINE__); return ::GetLastError(); } } pHandles[1] = s_ov.hEvent; dwObjectWaitState = ::WaitForMultipleObjects( 2, pHandles, FALSE, INFINITE ); switch ( dwObjectWaitState ) { case WAIT_ABANDONED: TRACE(_T("SerialPortRxThreadFn : Owner thread terminated prematurely.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ERROR_ARENA_TRASHED, __WFILE__, __LINE__); return ERROR_ARENA_TRASHED; break; case WAIT_TIMEOUT: TRACE(_T("SerialPortRxThreadFn : The timeout is set to INFINITE; there should be no timeout. State is nonsignaled.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), WAIT_TIMEOUT, __WFILE__, __LINE__); return WAIT_TIMEOUT; break; case WAIT_FAILED: TRACE(_T("SerialPortRxThreadFn : Call to WaitCommEvent failed.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ::GetLastError(), __WFILE__, __LINE__); return ::GetLastError(); break; case WAIT_OBJECT_0: // thread exit event signalled bContinue = FALSE; if ( !::ResetEvent( pHandles[0] ) ) { TRACE(_T("SerialPortRxThreadFn : Failed to reset the serial port thread exit event.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ::GetLastError(), __WFILE__, __LINE__); return ::GetLastError(); } break; case WAIT_OBJECT_0 + 1: // OVERLAPPED structure event signalled // Read data from serial port. if ( !::ReadFile( s_hSerialPort, pBuf, RX_BUF_SIZE, &amp;dwWritten, &amp;s_ov ) ) // &lt;- Set breakpoint here { TRACE(_T("SerialPortRxThreadFn : Call to ReadFile filed.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ::GetLastError(), __WFILE__, __LINE__); return ::GetLastError(); } // Discontinue thread operation if there are no more bytes in the serial port receive buffer. if ( dwWritten == 0 ) // &lt;- Or, set breakpoint here { bContinue = FALSE; } // Copy the received bytes to the thread-safe buffer. else if ( !s_pobjRxRingBuffer-&gt;Add( pBuf, dwWritten, TRUE ) ) { TRACE(_T("SerialPortRxThreadFn : Failed to add bytes to ring buffer.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ERROR_INSUFFICIENT_BUFFER, __WFILE__, __LINE__); return ERROR_INSUFFICIENT_BUFFER; } else if ( s_SpCallbackFn != NULL ) { // Notify application of received data. if ( (dwRetVal = s_SpCallbackFn( s_pobjRxRingBuffer-&gt;ItemsInBuffer() )) != ERROR_SUCCESS ) { TRACE(_T("SerialPortRxThreadFn : Serial port callback function failed.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), dwRetVal, __WFILE__, __LINE__); return dwRetVal; } } if ( !::ResetEvent( pHandles[1] ) ) { TRACE(_T("SerialPortRxThreadFn : Failed to reset the OVERLAPPED structure event.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ::GetLastError(), __WFILE__, __LINE__); return ::GetLastError(); } break; default: // Do nothing. break; } } ::CloseHandle( s_ov.hEvent ); return ERROR_SUCCESS; </code></pre> <p>If I set my breakpoint on the line calling <code>ReadFile</code> everything works as I expect, and the PC gets into the callback function. However, if I set my breakpoint at the next line, where <code>dwWritten</code> is evaluated for zero, it is zero, the expression evaluates as TRUE, and the loop exits; the PC never gets to the callback. What am I doing wrong? Thanks.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USJim Fell
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POSerial Port Receive Thread Not Behaving as Expected - C++
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POSerial Port Receive Thread Not Behaving as Expected - C++
      1. USrandombrein
      1. VTFavorite
    1. COSeems like you're doing a lot more work than you need to. Why are you handling serial data asynchronously on a thread? Why not just let the thread block on I/O?
      singulars
      1. POSerial Port Receive Thread Not Behaving as Expected - C++
      1. USJay
    2. COAlso you are leaking the Handle, you may not return from the function without closing the handle but you are doing so on error conditions.
      singulars
      1. POSerial Port Receive Thread Not Behaving as Expected - C++
      1. USdoron
    3. COYou have to reset the event pHandles[1] before call to ReadFile.
      singulars
      1. POSerial Port Receive Thread Not Behaving as Expected - C++
      1. USLuis G. Costantini R.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload