MP+fencewmbonceonce+fencermbonceonce.litmus

 1C MP+fencewmbonceonce+fencermbonceonce
 2
 3(*
 4 * Result: Never
 5 *
 6 * This litmus test demonstrates that smp_wmb() and smp_rmb() provide
 7 * sufficient ordering for the message-passing pattern.  However, it
 8 * is usually better to use smp_store_release() and smp_load_acquire().
 9 *)
10
11{}
12
13P0(int *buf, int *flag) // Producer
14{
15	WRITE_ONCE(*buf, 1);
16	smp_wmb();
17	WRITE_ONCE(*flag, 1);
18}
19
20P1(int *buf, int *flag) // Consumer
21{
22	int r0;
23	int r1;
24
25	r0 = READ_ONCE(*flag);
26	smp_rmb();
27	r1 = READ_ONCE(*buf);
28}
29
30exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)