18c2ecf20Sopenharmony_ciC MP+polocks
28c2ecf20Sopenharmony_ci
38c2ecf20Sopenharmony_ci(*
48c2ecf20Sopenharmony_ci * Result: Never
58c2ecf20Sopenharmony_ci *
68c2ecf20Sopenharmony_ci * This litmus test demonstrates how lock acquisitions and releases can
78c2ecf20Sopenharmony_ci * stand in for smp_load_acquire() and smp_store_release(), respectively.
88c2ecf20Sopenharmony_ci * In other words, when holding a given lock (or indeed after releasing a
98c2ecf20Sopenharmony_ci * given lock), a CPU is not only guaranteed to see the accesses that other
108c2ecf20Sopenharmony_ci * CPUs made while previously holding that lock, it is also guaranteed
118c2ecf20Sopenharmony_ci * to see all prior accesses by those other CPUs.
128c2ecf20Sopenharmony_ci *)
138c2ecf20Sopenharmony_ci
148c2ecf20Sopenharmony_ci{}
158c2ecf20Sopenharmony_ci
168c2ecf20Sopenharmony_ciP0(int *x, int *y, spinlock_t *mylock)
178c2ecf20Sopenharmony_ci{
188c2ecf20Sopenharmony_ci	WRITE_ONCE(*x, 1);
198c2ecf20Sopenharmony_ci	spin_lock(mylock);
208c2ecf20Sopenharmony_ci	WRITE_ONCE(*y, 1);
218c2ecf20Sopenharmony_ci	spin_unlock(mylock);
228c2ecf20Sopenharmony_ci}
238c2ecf20Sopenharmony_ci
248c2ecf20Sopenharmony_ciP1(int *x, int *y, spinlock_t *mylock)
258c2ecf20Sopenharmony_ci{
268c2ecf20Sopenharmony_ci	int r0;
278c2ecf20Sopenharmony_ci	int r1;
288c2ecf20Sopenharmony_ci
298c2ecf20Sopenharmony_ci	spin_lock(mylock);
308c2ecf20Sopenharmony_ci	r0 = READ_ONCE(*y);
318c2ecf20Sopenharmony_ci	spin_unlock(mylock);
328c2ecf20Sopenharmony_ci	r1 = READ_ONCE(*x);
338c2ecf20Sopenharmony_ci}
348c2ecf20Sopenharmony_ci
358c2ecf20Sopenharmony_ciexists (1:r0=1 /\ 1:r1=0)
36