Simple User Threads Library (uth_lib)

<< Features >>

A)  Preemptive thread library
    o Multiple threads of control 
    o Periodic clock handler
    o RR scheduling within high and low priority tasks

B)  Synchronization primitives
    o Synchronization primitives (locks and condition variables)

<< Example >>

const int	N = 8;
enum uth_priority_t { HI_PRI=0, LO_PRI, IDLE_PRI };
struct thr_arg {
    int	id;
    int	n;
  };
typdef struct thr_arg thr_arg_t;
typedef void func0_t( void );

int
main (...) {
  int		tickSz;
  int		debug;
  thr_arg_t	thr_arg[N];
  uth_tid_t	thr[N+1];
  int		result;

  if ( uth_init( N+1, tickSz=10, debug=0 ) < 0 ) { ... Error ... }
  for (int i=0; i<N; i++) {
    thr_arg[i].id = i;	thr_arg[i].n = ... something ...;
    if ( uth_create( &thr[i], LO_PRI, (func0_t *)&thr_compute, &thr_arg[i] ) < 0 )
      { ... Error ... }
  }

  thr_arg[N].id = N;	thr_arg[N].n = ... something ...;
  if ( uth_create( &thr[i], HI_PRI, (func0_t *)&thr_mon, &thr_arg[i] ) < 0 )
    { ... Error ... }

  for (int i=0; i<(N+1); i++) {
    if ( uth_join( thr[i], &result ) )
      printf( "Task %d result: %d\n", i, result );
  }
}

void
thr_compute( void *arg ) {
  int	myid	= arg->id;
  int	n	= arg->n;
  int	result;
  ... compute ...
  uth_exit( result );
}

void
thr_mon( void *arg ) {
  ... save cpu usage of each thread once per second ...
}