1C MP+polocks
2
3(*
4 * Result: Never
5 *
6 * This litmus test demonstrates how lock acquisitions and releases can
7 * stand in for smp_load_acquire() and smp_store_release(), respectively.
8 * In other words, when holding a given lock (or indeed after releasing a
9 * given lock), a CPU is not only guaranteed to see the accesses that other
10 * CPUs made while previously holding that lock, it is also guaranteed
11 * to see all prior accesses by those other CPUs.
12 *)
13
14{}
15
16P0(int *buf, int *flag, spinlock_t *mylock) // Producer
17{
18	WRITE_ONCE(*buf, 1);
19	spin_lock(mylock);
20	WRITE_ONCE(*flag, 1);
21	spin_unlock(mylock);
22}
23
24P1(int *buf, int *flag, spinlock_t *mylock) // Consumer
25{
26	int r0;
27	int r1;
28
29	spin_lock(mylock);
30	r0 = READ_ONCE(*flag);
31	spin_unlock(mylock);
32	r1 = READ_ONCE(*buf);
33}
34
35exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
36