MSXML, deadlock in multithreading application

Question

Hello,

I try to use msxml in multithreading application: one thread read value and another thread write value (I work with different subnodes). But I get a deadlock in application.

I create a simple example for demonstrait it:

// MSXMLMultithreadingTest.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <msxml6.h>
#include <comutil.h>

// Macro that calls a COM method returning HRESULT value.
#define CHK_HR(stmt)        do { hr=(stmt); if (FAILED(hr)) goto CleanUp; } while(0)

// Macro to verify memory allcation.
#define CHK_ALLOC(p)        do { if (!(p)) { hr = E_OUTOFMEMORY; goto CleanUp; } } while(0)

// Macro that releases a COM object if not NULL.
#define SAFE_RELEASE(p)     do { if ((p)) { (p)->Release(); (p) = NULL; } } while(0)\

// Helper function to create a VT_BSTR variant from a null terminated string. 
HRESULT VariantFromString(PCWSTR wszValue, VARIANT &Variant)
{
    HRESULT hr = S_OK;
    BSTR bstr = SysAllocString(wszValue);
    CHK_ALLOC(bstr);

    V_VT(&Variant)   = VT_BSTR;
    V_BSTR(&Variant) = bstr;

CleanUp:
    return hr;
}

DWORD WINAPI SetAttributeThreadFunction( LPVOID lpParam ) 
{
    auto pXMLDom = reinterpret_cast<IXMLDOMDocument *>(lpParam);
    BSTR queryString = L"/portfolio";
    IXMLDOMNode* tmp;
    if( FAILED(pXMLDom->selectSingleNode(queryString, &tmp)) )
    {
        OutputDebugString(L"FAILED(pXMLDom->selectSingleNode(queryString, &tmp))");
    }
    IXMLDOMElement* root;
    if( FAILED(tmp->QueryInterface(IID_IXMLDOMElement, (void **)&root)) )
    {
        OutputDebugString(L"FAILED(tmp->QueryInterface(IID_IXMLDOMElement, (void **)&root))");
    }
    BSTR attrName = L"TestAttribute";
    _variant_t value = 10;
    while(true)
    {
        root->setAttribute(attrName, value);
        OutputDebugString(L"setAttribute - Ok\n");
    }
}

DWORD WINAPI GetNodeTypedValueThreadFunction( LPVOID lpParam ) 
{
    auto pXMLDom = reinterpret_cast<IXMLDOMDocument *>(lpParam);
    BSTR queryString = L"/";
    IXMLDOMNode* tmp;
    if( FAILED(pXMLDom->selectSingleNode(queryString, &tmp)) )
    {
        OutputDebugString(L"FAILED(pXMLDom->selectSingleNode(queryString, &tmp))");
    }
    VARIANT _result;
    VariantInit(&_result);

    while(true)
    {
        tmp->get_nodeTypedValue(&_result);
        OutputDebugString(L"get_nodeTypedValue - Ok\n");
    }
}

// Helper function to create a DOM instance. 
HRESULT CreateAndInitDOM(IXMLDOMDocument **ppDoc)
{
    HRESULT hr = CoCreateInstance(__uuidof(FreeThreadedDOMDocument60), NULL, CLSCTX_INPROC_SERVER, IID_PPV_ARGS(ppDoc));
    if (SUCCEEDED(hr))
    {
        // these methods should not fail so don't inspect result
        (*ppDoc)->put_async(VARIANT_FALSE);  
        (*ppDoc)->put_validateOnParse(VARIANT_FALSE);
        (*ppDoc)->put_resolveExternals(VARIANT_FALSE);
    }
    return hr;
}

void loadDOMRaw()
{
    HRESULT hr = S_OK;
    IXMLDOMDocument *pXMLDom = NULL;
    IXMLDOMParseError *pXMLErr = NULL;

    BSTR bstrXML = L"<portfolio xmlns:dt=\"urn:schemas-microsoft-com:datatypes\"></portfolio>";
    BSTR bstrErr = NULL;
    VARIANT_BOOL varStatus;
    VARIANT varFileName;
    VariantInit(&varFileName);

    CHK_HR(CreateAndInitDOM(&pXMLDom));

    // XML file name to load
    CHK_HR(pXMLDom->loadXML(bstrXML, &varStatus));
    if (varStatus == VARIANT_TRUE)
    {
        CHK_HR(pXMLDom->get_xml(&bstrXML));
        printf("XML DOM loaded from stocks.xml:\n%S\n", bstrXML);
    }
    else
    {
        // Failed to load xml, get last parsing error
        CHK_HR(pXMLDom->get_parseError(&pXMLErr));
        CHK_HR(pXMLErr->get_reason(&bstrErr));
        printf("Failed to load DOM from stocks.xml. %S\n", bstrErr);
    }
    auto handle1 = CreateThread( 
            NULL,                   // default security attributes
            0,                      // use default stack size  
            SetAttributeThreadFunction,       // thread function name
            pXMLDom,          // argument to thread function 
            0,                      // use default creation flags 
            NULL);   // returns the thread identifier
    auto handle2 = CreateThread( 
            NULL,                   // default security attributes
            0,                      // use default stack size  
            GetNodeTypedValueThreadFunction,       // thread function name
            pXMLDom,          // argument to thread function 
            0,                      // use default creation flags 
            NULL);   // returns the thread identifier 

    Sleep(1000 * 300);

    TerminateThread(handle1, 0);
    TerminateThread(handle2, 0);

CleanUp:
    SAFE_RELEASE(pXMLDom);
    SAFE_RELEASE(pXMLErr);
    SysFreeString(bstrXML);
    SysFreeString(bstrErr);
    VariantClear(&varFileName);
}

int _tmain(int argc, _TCHAR* argv[])
{
     HRESULT hr = CoInitialize(NULL);
    if(SUCCEEDED(hr))
    {
        loadDOMRaw();
        CoUninitialize();
    }
    return 0;
}

What I am doing wrong?

Answer 1

Hi Evgeniy Mironov,

Welcome!
We will do some more pending research  about your problem and come back as soon as possible, Thanks for understanding.

Have a nice day.

---

Alan Chen[MSFT]
MSDN Community Support | Feedback to us
Get or Request Code Sample from Microsoft
Please remember to mark the replies as answers if they help and unmark them if they provide no help.

Answer 2

Hi Evgeniy,

While I would like to help you this particular question falls into the paid support category which requires a more in-depth level of support. Please visit the below link to see the various paid support options that are available to better meet your needs. http://support.microsoft.com/default.aspx?id=fh;en-us;offerprophone

Provide the sample code and the xml files it is parsing. We would try to create a repro at our end and find the cause of the multi-threading issue with the resolution.

Regards,

Angshuman Nayak