cache_lock_maybe_shared
cache_lock_maybe_shared(&nch, 1);
cache_lock_maybe_shared(&nch, 1);
cache_lock_maybe_shared(&nch, 1);
cache_lock_maybe_shared(nch, 0);
cache_lock_maybe_shared(&par, 0);
cache_lock_maybe_shared(nch, 0);
cache_lock_maybe_shared(&nd->nl_nch,
cache_lock_maybe_shared(&nch, wantsexcllock(nd, 0));
cache_lock_maybe_shared(&nch, 1);
void cache_lock_maybe_shared(struct nchandle *nch, int excl);