C C-SB+o-mb-o+o-mb-o.litmus { } P0(int *x, int *y) { int r1; WRITE_ONCE(*x, 1); smp_mb(); r1 = READ_ONCE(*y); } P1(int *x, int *y) { int r2; WRITE_ONCE(*y, 1); smp_mb(); r2 = READ_ONCE(*x); } exists (0:r1=0 /\ 1:r2=0)