Skip to main content

Programming: Windows Threading Vs Linux Threading (Part 6)

A thread cleanup handler in Linux and Windows thread cancellation:

A cleanup handler is a measure, used to deallocate a resource only if the thread exits or canceled. To register a cleanup handler, need to call pthread_cleanup_push() and
pass a pointer to cleanup function and the void * argument. The pthread_cleanup_pop() function removes the routine at the top of the calling thread's cancellation cleanup
stack and optionally invokes it (if execute is non-zero).

The following sample code shows how a dynamically allocated buffer from a thread can be deallocated on canceling the thread in Linux.

#include < pthread.h >
#include < stdio.h >
#include < string.h >
#include < unistd.h > 

char *pgArray = 0;

/* Buffer allocation */
char * allocate_array (size_t size)
    return new char[size];

void release_array (void *pArg)
        printf("release_array() called..\n");
        delete []pgArray;

void *Print_Details(void *param)
    printf("This is secondary thread's entry...\n");
    printf("Allocating a buffer of size 20...\n");

    pgArray = allocate_array(20);
    strcpy(pgArray, "This is a test");
    /*Registering the cleanup handler in case thread cancelled/exit*/
    pthread_cleanup_push(release_array, NULL);

    size_t sIndex = 0;

    // An infinite loop to keep the thread busy until thread cancel gets called...   
    while (pgArray[sIndex] != '\0')
        printf ("%c\n", pgArray[sIndex]);
        if(pgArray[sIndex] == '\0')
            sIndex = 0;
    printf("This is secondary thread's exit...\n");
    /*Unregister the cleanup handler by passing a nonzero value,
    this actually calls the release_array()*/
    return NULL;

/* Main program */

int main()
    pthread_t thread;
    int thread_ret;
    void *status;

    printf("This is main... Creating thread with default param\n");   
    pthread_create(&thread, NULL, &Print_Details, NULL);

    // Called secondary thread cancellation....
    printf("Called secondary thread cancellation...\n");
    printf("Main exited\n");
    return 0;

In Windows, as per Microsoft we should call TerminateThread only when there is no other go. Then the question comes what's the way in Windows, a thread/threads can be
canceled/stopped as required. Microsoft provided a way to do this by implementing following steps:

a.    Create an event object using the CreateEvent function.
b.    Create the threads.
c.    Each thread monitors the event state by calling the WaitForSingleObject function. Use a wait time-out interval of zero.
d.    Each thread terminates its own execution when the event is set to the signaled state (WaitForSingleObject returns WAIT_OBJECT_0).


Popular posts from this blog

Variadic template class to add numbers recursively during compilation

 The idea of having a class to add numbers (variable parameters) during compilation time recursively. Also wanted to restrict types to a single type while sending parameters to class member function. That said, if we mix int, float and double types to add function shall result in compilation error. How do we achieve this. The below is the code which actually helps to achieve this: <code> #include < fmt/format.h > template < typename T> class MyVarSumClass{     private :         T _sum = 0 ;     public :         template < typename ... TRest>         T add(T num, TRest... nums){             static_assert (std::conjunction<std::is_same<TRest, T>...>{}); /* Assert fails                if types are different */             _sum += num;             return add(nums...); // Next parameter packs gets picked recursively         }         // Base case         T add(T num){             _sum += num;             return _sum;         } }; int main() {     My

A simple approach to generate Fibonacci series via multi-threading

T his is a very simple approach taken to generate the Fibonacci series through multithreading. Here instead of a function, used a function object. The code is very simple and self-explanatory.  #include <iostream> #include <mutex> #include <thread> class Fib { public:     Fib() : _num0(1), _num1(1) {}     unsigned long operator()(); private:     unsigned long _num0, _num1;     std::mutex mu; }; unsigned long Fib::operator()() {     mu.lock(); // critical section, exclusive access to the below code by locking the mutex     unsigned long  temp = _num0;     _num0 = _num1;     _num1 = temp + _num0;     mu.unlock();     return temp; } int main() {     Fib f;          int i = 0;     unsigned long res = 0, res2= 0, res3 = 0;     std::cout << "Fibonacci series: ";     while (i <= 15) {         std::thread t1([&] { res = f(); }); // Capturing result to respective variable via lambda         std::thread t2([&] { res2 = f(); });         std::thread t3(

A concept to a product (Kimidori [ 黄緑]) - Part 2

In the previous part , we have seen KIMIDORI [ 黄緑] detect if a URL is malicious. In this part, we will see the details that KIMIDORI [ 黄緑] fetches out of the URL provided. As an example, provided a safe URL,, and let's see what it brings out: As we can see, the link is safe and the link is active, which means we can just click on the link to open it on IE.  Now it's time to look into the URL report (still under development):  We have URLs IP, Location, and HTTP Status code. The Report part is a sliding window, the Show Report button shows as well as hides the report. Show / Hide Report is a toggle button. Let's see if we get the same details for any bad (phishing / malicious) URL: Took an URL example from a phishing link and tested it. The tool detected it as not a good link (Screen Shot Below) & link does not activate unlike a safe URL: Now let's see the report part for more details including domain registration details: It looks like it&