linux/Documentation/litmus-tests/atomic/Atomic-RMW+mb__after_atomic-is-stronger-than-acquire.litmus
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   1C Atomic-RMW+mb__after_atomic-is-stronger-than-acquire
   2
   3(*
   4 * Result: Never
   5 *
   6 * Test that an atomic RMW followed by a smp_mb__after_atomic() is
   7 * stronger than a normal acquire: both the read and write parts of
   8 * the RMW are ordered before the subsequential memory accesses.
   9 *)
  10
  11{
  12}
  13
  14P0(int *x, atomic_t *y)
  15{
  16        int r0;
  17        int r1;
  18
  19        r0 = READ_ONCE(*x);
  20        smp_rmb();
  21        r1 = atomic_read(y);
  22}
  23
  24P1(int *x, atomic_t *y)
  25{
  26        atomic_inc(y);
  27        smp_mb__after_atomic();
  28        WRITE_ONCE(*x, 1);
  29}
  30
  31exists
  32(0:r0=1 /\ 0:r1=0)
  33