source: CIVL/examples/concurrency/barrier2.cvl@ b9942c9

/* Basic flag barrier.  Same algorithm as barrier.cvl, but
 * packaged to be re-used in other code.
 * 
 * civl verify barrier2.cvl
 */
#include <civlc.h>

struct _CIVL_Barrier {
  int numProcs;
  int *in_barrier;
  int num_in_barrier;
  int lock;
};

typedef struct _CIVL_Barrier CIVL_Barrier;

void CIVL_Barrier_init(int numProcs, CIVL_Barrier *barrier, int *array) {  
  barrier->numProcs = numProcs;
  barrier->num_in_barrier = 0;
  barrier->lock = 0;
  barrier->in_barrier = array;
  for (int i=0; i<numProcs; i++)
    barrier->in_barrier[i] = 0;
  return barrier;
}

void CIVL_barrier(CIVL_Barrier *barrier, int tid) {
  $atomic {
    $when (barrier->lock==0) barrier->lock = 1;
    barrier->in_barrier[tid] = 1;
    barrier->num_in_barrier++;
    if (barrier->num_in_barrier == barrier->numProcs) {
      for (int i=0; i<barrier->numProcs; i++)
        barrier->in_barrier[i] = 0;
      barrier->num_in_barrier = 0;
    }
    barrier->lock = 0;
    $when (barrier->in_barrier[tid] == 0);
  }
}


void main() {
  int N=4;
  $proc threads[N];
  int counter = 0;
  CIVL_Barrier b;
  int barrier_array[N];
  
  void run(int tid) {
    while ($true) {
      $assert counter == 0;
      CIVL_barrier(&b, tid);
      counter++;
      CIVL_barrier(&b, tid);
      $assert counter == N;
      CIVL_barrier(&b, tid);
      counter--;
      CIVL_barrier(&b, tid);
    }
  }
  
  $atomic {
    CIVL_Barrier_init(N, &b, barrier_array);
    for (int i=0; i<N; i++) threads[i] = $spawn run(i);
  }
  $atomic {
    for (int i=0; i<N; i++) $wait threads[i];
  }
}