C C-po-loc { } P0(int *x, int *y) { int r0; int r1; r0 = READ_ONCE(*y); smp_rmb(); r1 = READ_ONCE(*x); WRITE_ONCE(*x, 1); } P1(int *x, int *y) { int r2; r2 = READ_ONCE(*x); WRITE_ONCE(*y, r2); } exists (0:r0=1)