Skip to main content

Programming: Windows Threading Vs Linux Threading (Part 5)

Thread Cancellation in GNU/Linux:

Today, I'm interested to explore how we can prepare thread in GNU/Linux to ignore thread cancellation. This is acvhieved with pthread_setcancelstate().

The signature of the function is:
int pthread_setcancelstate(int state, int *oldstate); 

The function is thread and signal safe. The function sets the cancel  state to one of PTHREAD_CANCEL_ENABLE or  PTHREAD_CANCEL_DISABLE and returns the old cancel state.
Please see the second parameter.
void *Print_Details(void *param)
{
     printf("This is secondary thread's entry...\n");
     int oldState;
     pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldState);
     sleep(1);
     for(int i = 0; i < 10; ++i)
     {
          printf("Inside the secondary thread...\n");
     }

     pthread_setcancelstate(oldState, NULL);

     printf("This is secondary thread's exit...\n");
     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);

     sleep (1);

     // Called secondary thread cancellation....
     printf("Called secondary thread cancellation...\n");
     pthread_cancel(thread);
     printf("Thread Cancel ignored...\n");
     sleep(2);
     printf("Main exited\n");

     return 0;
}

Output:
This is main... Creating thread with default param
This is secondary thread's entry...
Called secondary thread cancellation...
Thread Cancel ignored...
Inside the secondary thread...
Inside the secondary thread...
Inside the secondary thread...
Inside the secondary thread...
Inside the secondary thread...
Inside the secondary thread...
Inside the secondary thread...
Inside the secondary thread...
Inside the secondary thread...
Inside the secondary thread...
This is secondary thread's exit...
Main exited
Labels:

Comments

Post a Comment

Popular posts from this blog

Reversing char array without splitting the array to tokens

 I was reading about strdup, a C++ function and suddenly an idea came to my mind if this can be leveraged to aid in reversing a character array without splitting the array into words and reconstructing it again by placing spaces and removing trailing spaces. Again, I wanted an array to be passed as a function argument and an array size to be passed implicitly with the array to the function. Assumed, a well-formed char array has been passed into the function. No malformed array checking is done inside the function. So, the function signature and definition are like below: Below is the call from the client code to reverse the array without splitting tokens and reconstructing it. Finally, copy the reversed array to the destination.  For GNU C++, we should use strdup instead _strdup . On run, we get the following output: Demo code
Post a Comment
Read more

Close a Window Application from another application.

 This is just a demo application code to show how the WM_CLOSE message can be sent to the target process which has a titled window to close the application. To achieve this, either we can use SendMessage or PostMessage APIs to send required Windows messages to the target application. Though both the APIs are dispatching WM_XXXXX message to target application two APIs has some differences, these are as below: 1. SendMessage () call is a blocking call but PostMessage is a non-blocking call(Asynchronous) 2. SendMessage() APIs return type is LRESULT (LONG_PTR) but PostMessage() APIs return type is BOOL(typedef int). In Short, SendMessage () APIs return type depends on what message has been sent to the Windowed target process. For the other one, it's always a non-zero value, which indicates the message has been successfully placed on the target process message queue. Now let's see how can I close a target windowed application "Solitaire & Casual Games" from my custom-
Post a Comment
Read more

XOR (Exclusive OR) for branchless coding

The following example shows the array reversing using the  XOR operator . No need to take any additional variable to reverse the array.   int main(int argc, _TCHAR* argv[]) { char str[] = "I AM STUDENT"; int length = strlen(str); for(int i = 0; i < ((length/2)); i++) { str[i] ^= str[length - (1+i)]; str[length - (1+i)] ^= str[i]; str[i] ^= str[length - (1+i)]; } cout << str << endl; return 0; } The above example is one of the uses of XOR but XOR comes in handy when we can do branchless coding  methods like butterfly switch etc. Sometimes this is very effective in speeding up the execution.  Let's see one of the uses of XOR in branchless coding. I am taking a simple example of Y = | X |.  Yes, I am generating abs of a supplied number. So, my function signature/definition in C++ looks like below: int absoluteBranch( int x) {     if (x < 0 ) {         return -x;     }     else {         retur
1 comment
Read more