GC_IN_SERVICE
clear_bit(GC_IN_SERVICE, &gc->flags);
if (test_and_set_bit(GC_IN_SERVICE, &gc->flags)) {
clear_bit(GC_IN_SERVICE, &gc->flags);
clear_bit(GC_IN_SERVICE, &gc->flags);
if (test_bit(GC_IN_SERVICE, &gc->flags))