C C-atomicpo.litmus { } P0(int *x, int *y) { WRITE_ONCE(*y, 1); smp_wmb(); WRITE_ONCE(*x, 1); } P1(int *x, int *y) { r1 = xchg_relaxed(x, 1); r2 = xchg_relaxed(y, 1); } exists (1:r1=1 /\ 1:r2=0)