PT_CANCEL_DISABLED
atomic_store_relaxed(&self->pt_cancel, PT_CANCEL_DISABLED);
if ((old & PT_CANCEL_DISABLED) == 0) {
flags = PT_CANCEL_DISABLED;
new = (old & ~PT_CANCEL_DISABLED) | flags;
(PT_CANCEL_DISABLED|PT_CANCEL_CANCELLED))) {
if (old & PT_CANCEL_DISABLED)