File content as of revision 2:0cf7e435eeb8:

/* 21_ MUTEX a Guard at door - Basic program 
MUTEX allow only one Thread / Function call inside CS, Mutex have ownership type locking mechanism.
Procees /or Thread who locked block,only same process /or thread can unlock it.
*/


//PROGRAM CREATED BY : JAYDEEP SHAH -- radheec@gmail.com
//DATE : 25 JULY 20 ,VERSION 1.0

//OUTPUT : USE SERIAL TERMINAL 9600    8-N-1


#include "mbed.h"  //MBED LIBRARY 

Mutex M_LOCK;  // Create MUTEX OBJECT  -class = MUTEX

//Create Two Thread 

Thread t2;  

Thread t3; 


//Here below section act as CS critical section

void common_function(const char *name, int state)  //TWO ARGUMENTS 1) WHO CALLED THIS FUNCTION 2)STATE OF CALLER
{
    printf("Thread arrive at door %s: %d\n\r", name, state);
    
    M_LOCK.lock();  //After arrive lock the code---------------------------LOCK THE BLOCK
    
    printf("This Thread lock the code %s: %d\n\r", name, state);
    wait(0.5); //sleep
    printf("Thread cross & unlock %s: %d\n\r", name, state); //OUTSIDE CODE BLOCK ---------   
    M_LOCK.unlock();  //After completing task unlock the code ------------- UNLOCK THE BLOCK
    
//DO NOT WRITE any print statement after  unlock() it create missunderstanding ....
/* print statement require more clk cycle,after  unlock the MUTEX Flag - schedular quickly schedule next thread before print the statement.*/
}



//Function -- We will connect more than one thread with this function
//So because of context switching this Function become sharable between multiple process.
void test_thread(void const *args)
{
    while (true) {
        common_function((const char *)args, 0);
        ThisThread::sleep_for(500);
        common_function((const char *)args, 1);
        ThisThread::sleep_for(500);
    }
}

int main()
{
    t2.start(callback(test_thread, (void *)"Th 2"));
    t3.start(callback(test_thread, (void *)"Th 3"));

    test_thread((void *)"Th 1");  // DIRECT CALL via main thread
}