1C IRIW+fencembonceonces+OnceOnce
 2
 3(*
 4 * Result: Never
 5 *
 6 * Test of independent reads from independent writes with smp_mb()
 7 * between each pairs of reads.  In other words, is smp_mb() sufficient to
 8 * cause two different reading processes to agree on the order of a pair
 9 * of writes, where each write is to a different variable by a different
10 * process?  This litmus test exercises LKMM's "propagation" rule.
11 *)
12
13{}
14
15P0(int *x)
16{
17	WRITE_ONCE(*x, 1);
18}
19
20P1(int *x, int *y)
21{
22	int r0;
23	int r1;
24
25	r0 = READ_ONCE(*x);
26	smp_mb();
27	r1 = READ_ONCE(*y);
28}
29
30P2(int *y)
31{
32	WRITE_ONCE(*y, 1);
33}
34
35P3(int *x, int *y)
36{
37	int r0;
38	int r1;
39
40	r0 = READ_ONCE(*y);
41	smp_mb();
42	r1 = READ_ONCE(*x);
43}
44
45exists (1:r0=1 /\ 1:r1=0 /\ 3:r0=1 /\ 3:r1=0)

 1C IRIW+fencembonceonces+OnceOnce
 2
 3(*
 4 * Result: Never
 5 *
 6 * Test of independent reads from independent writes with smp_mb()
 7 * between each pairs of reads.  In other words, is smp_mb() sufficient to
 8 * cause two different reading processes to agree on the order of a pair
 9 * of writes, where each write is to a different variable by a different
10 * process?  This litmus test exercises LKMM's "propagation" rule.
11 *)
12
13{}
14
15P0(int *x)
16{
17	WRITE_ONCE(*x, 1);
18}
19
20P1(int *x, int *y)
21{
22	int r0;
23	int r1;
24
25	r0 = READ_ONCE(*x);
26	smp_mb();
27	r1 = READ_ONCE(*y);
28}
29
30P2(int *y)
31{
32	WRITE_ONCE(*y, 1);
33}
34
35P3(int *x, int *y)
36{
37	int r0;
38	int r1;
39
40	r0 = READ_ONCE(*y);
41	smp_mb();
42	r1 = READ_ONCE(*x);
43}
44
45exists (1:r0=1 /\ 1:r1=0 /\ 3:r0=1 /\ 3:r1=0)