TTM_WRITE_LOCK_PENDING
if (lock->rw == 0 && ((lock->flags & ~TTM_WRITE_LOCK_PENDING) == 0)) {
lock->flags &= ~TTM_WRITE_LOCK_PENDING;
lock->flags |= TTM_WRITE_LOCK_PENDING;
lock->flags &= ~TTM_WRITE_LOCK_PENDING;