tools/memory-model/litmus-tests/MP+polockmbonce+poacquiresilsil.litmus

   1 C MP+polockmbonce+poacquiresilsil
   2
   3 (*
   4  * Result: Never
   5  *
   6  * Do spinlocks combined with smp_mb__after_spinlock() provide order
   7  * to outside observers using spin_is_locked() to sense the lock-held
   8  * state, ordered by acquire?  Note that when the first spin_is_locked()
   9  * returns false and the second true, we know that the smp_load_acquire()
  10  * executed before the lock was acquired (loosely speaking).
  11  *)
  12
  13 {
  14         spinlock_t lo;
  15         int x;
  16 }
  17
  18 P0(spinlock_t *lo, int *x) // Producer
  19 {
  20         spin_lock(lo);
  21         smp_mb__after_spinlock();
  22         WRITE_ONCE(*x, 1);
  23         spin_unlock(lo);
  24 }
  25
  26 P1(spinlock_t *lo, int *x) // Consumer
  27 {
  28         int r1;
  29         int r2;
  30         int r3;
  31
  32         r1 = smp_load_acquire(x);
  33         r2 = spin_is_locked(lo);
  34         r3 = spin_is_locked(lo);
  35 }
  36
  37 exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1) (* Bad outcome. *)