st_index
DTRACE_PROBE2(qlevel, unsigned int, stp->st_index,
unsigned int index = stp->st_index;
stp->st_index = index;
stp->st_index = 0;
unsigned int, stp->st_index,
unsigned int, stp->st_index,
DTRACE_PROBE1(defer, unsigned int, stp->st_index);
stp->st_index = 0;