LXR linux/tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus

   1C MP+onceassign+derefonce
   2
   3(*
   4 * Result: Never
   5 *
   6 * This litmus test demonstrates that rcu_assign_pointer() and
   7 * rcu_dereference() suffice to ensure that an RCU reader will not see
   8 * pre-initialization garbage when it traverses an RCU-protected data
   9 * structure containing a newly inserted element.
  10 *)
  11
  12{
  13p=y;
  14}
  15
  16P0(int *x, int **p) // Producer
  17{
  18        WRITE_ONCE(*x, 1);
  19        rcu_assign_pointer(*p, x);
  20}
  21
  22P1(int *x, int **p) // Consumer
  23{
  24        int *r0;
  25        int r1;
  26
  27        rcu_read_lock();
  28        r0 = rcu_dereference(*p);
  29        r1 = READ_ONCE(*r0);
  30        rcu_read_unlock();
  31}
  32
  33exists (1:r0=x /\ 1:r1=0) (* Bad outcome. *)
  34