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
  15 P0(spinlock_t *lo, int *x) // Producer
  16 {
  17         spin_lock(lo);
  18         smp_mb__after_spinlock();
  19         WRITE_ONCE(*x, 1);
  20         spin_unlock(lo);
  21 }
  22
  23 P1(spinlock_t *lo, int *x) // Consumer
  24 {
  25         int r1;
  26         int r2;
  27         int r3;
  28
  29         r1 = smp_load_acquire(x);
  30         r2 = spin_is_locked(lo);
  31         r3 = spin_is_locked(lo);
  32 }
  33
  34 exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1) (* Bad outcome. *)