Notify all threads.

Question

Hello.

I did an example of my threading. The problem is, that the while loop is using 100% of cpu. Is there any another way to do that?
The notify has to be statical.

My code:

using System;
using System.Threading;
using System.Diagnostics;
namespace ConsoleApplication2
{
   class ThreadingExample
    {

        static void Main()
        {
            Console.WriteLine("main thread starting worker thread...");
            test a = new test(1);
            test b = new test(2);
            test c = new test(3);
            Thread t = new Thread(a.work);
            Thread tb = new Thread(b.work);
            Thread tc = new Thread(c.work);
            t.Start();
            tb.Start();
            tc.Start();

            Console.WriteLine("main thrad sleeping for 1 second...");
            Thread.Sleep(1000);

            Console.WriteLine("main thread signaling worker thread...2");
              test.notify(2);
            
            Thread.Sleep(1000);
            
              Console.WriteLine("main thread signaling worker thread...1");            
               test.notify(1);

            
        }
    }
    
    class test
    {
        private int i;
        static int who;
        static bool free;
        private int pwho;
        
        public test(int j)
        {
            i=j;
        }
        public void work()
        {        
            Console.WriteLine("    waiting on event... {0}",i);                        
            
            while(pwho != i)
            {
                //do nothing just waiting
    
            }
                
                pwho = who;
                free = false;
                Console.WriteLine("   worker thread reactivated, now exiting...{0}",i);
           
        }
        static public void notify(int w)
        {
            while(free){}
            free = true;
            who = w;
        }
    }

}