////////////////////////////////////////////////////////////
//
//	mutexTester.c
//
//	Jeff Ondich, 5/7/98
//
//	This program illustrates the use of the mutex_t
//	type in conjunction with Mach C-threads.  If you
//	remove the mutex_lock() and mutex_unlock() calls,
// 	then the parent and child threads can interrupt
//	each other in the midst of important business.
//	With the mutex_lock() and mutex_unlock() calls,
//	the parent and child can finish their important
//	business without interruption.
//
////////////////////////////////////////////////////////////


#include		<mach/cthreads.h>
#include		<stdio.h>

// Global variable(s)

mutex_t				lock;

// Prototype(s)

void Child( int childID );



int main( void )
{
	// This is C, not C++, so I need to declare local
	// variables up here.  Our cc compiler is kind enough,
	// however, to allow me C++ comments.

	int		i;

	// You have to tell Mach that you intend to use a
	// mutex_t variable before you actually use it.
	
	lock = mutex_alloc();

	// Spawn a child thread that starts execution in the
	// function Child().

    cthread_detach( cthread_fork( (cthread_fn_t)Child, (any_t)0 ) );

	
	// This code is executed only by the parent, though
	// it bears an uncanny resemblance to the code
	// executed by the child.

	while( 1 == 1 )
	{
		// Fool around for a while
		for( i=0; i < 1000000; i++ )
		{
		}

		// Now do some serious business, reporting
		// when the business starts and when it
		// finishes.  Lock the lock first, to 
		// make sure you don't get interrupted.

	    mutex_lock( lock );
		printf( "\tPARENT START\n" );
		for( i=0; i < 1000000; i++ )
		{
		}
		printf( "\tPARENT STOP\n" );
		mutex_unlock( lock );
	}
}


void Child( int childID )
{
	int		i;

	while( 1 == 1 )
	{
		// Fool around for a while
		for( i=0; i < 1000000; i++ )
		{
		}

		// Now do some serious business, reporting
		// when the business starts and when it
		// finishes.  Lock the lock first, to 
		// make sure you don't get interrupted.

	    mutex_lock( lock );
		printf( "Child %d start\n", childID );
		for( i=0; i < 1000000; i++ )
		{
		}
		printf( "Child %d stop\n", childID );
		mutex_unlock( lock );
	}
}