C C-wmb-is-not-A-cumulative.litmus { } P0(int *x) { WRITE_ONCE(*x, 1); } P1(int *x, int *y, int *z) { r1 = READ_ONCE(*x); WRITE_ONCE(*z, r1); smp_wmb(); WRITE_ONCE(*y, 1); } P2(int *x, int *y) { r2 = READ_ONCE(*y); smp_rmb(); r3 = READ_ONCE(*x); } exists (1:r1=1 /\ 2:r2=1 /\ 2:r3=0)