1*4882a593SmuzhiyunC MP+fencewmbonceonce+fencermbonceonce
2*4882a593Smuzhiyun
3*4882a593Smuzhiyun(*
4*4882a593Smuzhiyun * Result: Never
5*4882a593Smuzhiyun *
6*4882a593Smuzhiyun * This litmus test demonstrates that smp_wmb() and smp_rmb() provide
7*4882a593Smuzhiyun * sufficient ordering for the message-passing pattern.  However, it
8*4882a593Smuzhiyun * is usually better to use smp_store_release() and smp_load_acquire().
9*4882a593Smuzhiyun *)
10*4882a593Smuzhiyun
11*4882a593Smuzhiyun{}
12*4882a593Smuzhiyun
13*4882a593SmuzhiyunP0(int *x, int *y)
14*4882a593Smuzhiyun{
15*4882a593Smuzhiyun	WRITE_ONCE(*x, 1);
16*4882a593Smuzhiyun	smp_wmb();
17*4882a593Smuzhiyun	WRITE_ONCE(*y, 1);
18*4882a593Smuzhiyun}
19*4882a593Smuzhiyun
20*4882a593SmuzhiyunP1(int *x, int *y)
21*4882a593Smuzhiyun{
22*4882a593Smuzhiyun	int r0;
23*4882a593Smuzhiyun	int r1;
24*4882a593Smuzhiyun
25*4882a593Smuzhiyun	r0 = READ_ONCE(*y);
26*4882a593Smuzhiyun	smp_rmb();
27*4882a593Smuzhiyun	r1 = READ_ONCE(*x);
28*4882a593Smuzhiyun}
29*4882a593Smuzhiyun
30*4882a593Smuzhiyunexists (1:r0=1 /\ 1:r1=0)
31