C S+wmbonceonce+poacquireonce
{}
P0(int *x, int *y)
{
WRITE_ONCE(*x, 2);
smp_wmb();
WRITE_ONCE(*y, 1);
}
P1(int *x, int *y)
int r0;
r0 = smp_load_acquire(y);
WRITE_ONCE(*x, 1);
exists (x=2 /\ 1:r0=1)