rw_tryupgrade
#define VERIEXEC_RW_UPGRADE(lock) while((rw_tryupgrade(lock)) == 0){};
if (!rw_tryupgrade(&vip->vi_lock)) {
if (!rw_tryupgrade(&vip->vi_lock)) {
#define LLE_TRY_UPGRADE(lle) rw_tryupgrade(&(lle)->lle_lock)
int rw_tryupgrade(krwlock_t *);
if (__predict_false(!rw_tryupgrade(amap->am_lock))) {
if (__predict_false(!rw_tryupgrade(uobj->vmobjlock))) {