18c2ecf20Sopenharmony_ciC MP+polockonce+poacquiresilsil
28c2ecf20Sopenharmony_ci
38c2ecf20Sopenharmony_ci(*
48c2ecf20Sopenharmony_ci * Result: Sometimes
58c2ecf20Sopenharmony_ci *
68c2ecf20Sopenharmony_ci * Do spinlocks provide order to outside observers using spin_is_locked()
78c2ecf20Sopenharmony_ci * to sense the lock-held state, ordered by acquire?  Note that when the
88c2ecf20Sopenharmony_ci * first spin_is_locked() returns false and the second true, we know that
98c2ecf20Sopenharmony_ci * the smp_load_acquire() executed before the lock was acquired (loosely
108c2ecf20Sopenharmony_ci * speaking).
118c2ecf20Sopenharmony_ci *)
128c2ecf20Sopenharmony_ci
138c2ecf20Sopenharmony_ci{
148c2ecf20Sopenharmony_ci}
158c2ecf20Sopenharmony_ci
168c2ecf20Sopenharmony_ciP0(spinlock_t *lo, int *x)
178c2ecf20Sopenharmony_ci{
188c2ecf20Sopenharmony_ci	spin_lock(lo);
198c2ecf20Sopenharmony_ci	WRITE_ONCE(*x, 1);
208c2ecf20Sopenharmony_ci	spin_unlock(lo);
218c2ecf20Sopenharmony_ci}
228c2ecf20Sopenharmony_ci
238c2ecf20Sopenharmony_ciP1(spinlock_t *lo, int *x)
248c2ecf20Sopenharmony_ci{
258c2ecf20Sopenharmony_ci	int r1;
268c2ecf20Sopenharmony_ci	int r2;
278c2ecf20Sopenharmony_ci	int r3;
288c2ecf20Sopenharmony_ci
298c2ecf20Sopenharmony_ci	r1 = smp_load_acquire(x);
308c2ecf20Sopenharmony_ci	r2 = spin_is_locked(lo);
318c2ecf20Sopenharmony_ci	r3 = spin_is_locked(lo);
328c2ecf20Sopenharmony_ci}
338c2ecf20Sopenharmony_ci
348c2ecf20Sopenharmony_ciexists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1)
35