#include <unistd.h>
#include <sys/time.h>

/* runtime in microseconds */
#define RUNTIME 9000

int main( int argc, char** argv )
    {
    unsigned long n=0;
    unsigned long t;
    struct timeval s, e;

    while ( 1 )
	{

	/* work */
	gettimeofday( &s, NULL );
	do
	    {
	    n++;
	    gettimeofday( &e, NULL );
	    t = (e.tv_sec-s.tv_sec)*1000000
		+(e.tv_usec-s.tv_usec);
	    }
	while ( t < RUNTIME );

	/* sleep */
	usleep( 0 );
	}
    }