tools/memory-model/litmus-tests/R+fencembonceonces.litmus

   1 C R+fencembonceonces
   2
   3 (*
   4  * Result: Never
   5  *
   6  * This is the fully ordered (via smp_mb()) version of one of the classic
   7  * counterintuitive litmus tests that illustrates the effects of store
   8  * propagation delays.  Note that weakening either of the barriers would
   9  * cause the resulting test to be allowed.
  10  *)
  11
  12 {}
  13
  14 P0(int *x, int *y)
  15 {
  16         WRITE_ONCE(*x, 1);
  17         smp_mb();
  18         WRITE_ONCE(*y, 1);
  19 }
  20
  21 P1(int *x, int *y)
  22 {
  23         int r0;
  24
  25         WRITE_ONCE(*y, 2);
  26         smp_mb();
  27         r0 = READ_ONCE(*x);
  28 }
  29
  30 exists (y=2 /\ 1:r0=0)