162306a36Sopenharmony_ciC MP+polocks
262306a36Sopenharmony_ci
362306a36Sopenharmony_ci(*
462306a36Sopenharmony_ci * Result: Never
562306a36Sopenharmony_ci *
662306a36Sopenharmony_ci * This litmus test demonstrates how lock acquisitions and releases can
762306a36Sopenharmony_ci * stand in for smp_load_acquire() and smp_store_release(), respectively.
862306a36Sopenharmony_ci * In other words, when holding a given lock (or indeed after releasing a
962306a36Sopenharmony_ci * given lock), a CPU is not only guaranteed to see the accesses that other
1062306a36Sopenharmony_ci * CPUs made while previously holding that lock, it is also guaranteed
1162306a36Sopenharmony_ci * to see all prior accesses by those other CPUs.
1262306a36Sopenharmony_ci *)
1362306a36Sopenharmony_ci
1462306a36Sopenharmony_ci{}
1562306a36Sopenharmony_ci
1662306a36Sopenharmony_ciP0(int *buf, int *flag, spinlock_t *mylock) // Producer
1762306a36Sopenharmony_ci{
1862306a36Sopenharmony_ci	WRITE_ONCE(*buf, 1);
1962306a36Sopenharmony_ci	spin_lock(mylock);
2062306a36Sopenharmony_ci	WRITE_ONCE(*flag, 1);
2162306a36Sopenharmony_ci	spin_unlock(mylock);
2262306a36Sopenharmony_ci}
2362306a36Sopenharmony_ci
2462306a36Sopenharmony_ciP1(int *buf, int *flag, spinlock_t *mylock) // Consumer
2562306a36Sopenharmony_ci{
2662306a36Sopenharmony_ci	int r0;
2762306a36Sopenharmony_ci	int r1;
2862306a36Sopenharmony_ci
2962306a36Sopenharmony_ci	spin_lock(mylock);
3062306a36Sopenharmony_ci	r0 = READ_ONCE(*flag);
3162306a36Sopenharmony_ci	spin_unlock(mylock);
3262306a36Sopenharmony_ci	r1 = READ_ONCE(*buf);
3362306a36Sopenharmony_ci}
3462306a36Sopenharmony_ci
3562306a36Sopenharmony_ciexists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
36