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	spinlock_t mylock;
16	int buf;
17	int flag;
18}
19
20P0(int *buf, int *flag, spinlock_t *mylock) // Producer
21{
22	WRITE_ONCE(*buf, 1);
23	spin_lock(mylock);
24	WRITE_ONCE(*flag, 1);
25	spin_unlock(mylock);
26}
27
28P1(int *buf, int *flag, spinlock_t *mylock) // Consumer
29{
30	int r0;
31	int r1;
32
33	spin_lock(mylock);
34	r0 = READ_ONCE(*flag);
35	spin_unlock(mylock);
36	r1 = READ_ONCE(*buf);
37}
38
39exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
40