dtrace_enable_nullop
.dtps_enable = dtrace_enable_nullop,
if (old->dtpv_pops.dtps_enable == dtrace_enable_nullop) {
ASSERT(pvp->dtpv_pops.dtps_enable != dtrace_enable_nullop);
ASSERT(prov->dtpv_pops.dtps_enable != dtrace_enable_nullop);