C R+mbonceonces
{}
P0(int *x, int *y)
{
WRITE_ONCE(*x, 1);
smp_mb();
WRITE_ONCE(*y, 1);
}
P1(int *x, int *y)
int r0;
WRITE_ONCE(*y, 2);
r0 = READ_ONCE(*x);
exists (y=2 /\ 1:r0=0)