Hi, during my coding, I found macro a bit different from other QTAIL macros.
QTAILQ_INSERT_AFTER was defined as: ----------------------------------------------------------- #define QTAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\ (elm)->field.tqe_next->field.tqe_prev = \ &(elm)->field.tqe_next; \ else \ (head)->tqh_last = &(elm)->field.tqe_next; \ (listelm)->field.tqe_next = (elm); \ (elm)->field.tqe_prev = &(listelm)->field.tqe_next; \ } while (/*CONSTCOND*/0) --------------------------------------------------------- QTAILQ_INSERT_BEFORE is defined as following: #define QTAILQ_INSERT_BEFORE(listelm, elm, field) do { (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ (elm)->field.tqe_next = (listelm); \ *(listelm)->field.tqe_prev = (elm); \ (listelm)->field.tqe_prev = &(elm)->field.tqe_next; \ } while (/*CONSTCOND*/0) ---------------------------------------------------------- It did not take care of "head" as QTAILQ_INSERT_AFTER did, so I am wondering what would happen if I use QTAILQ_INSERT_BEFORE to insert one element to a queue that have only one element in it, would it happen that the queue head pointer is not updated and the real first element is lost? Currently some codes in qemu have used this macro. -- Best Regards Wayne Xia mail:xiaw...@linux.vnet.ibm.com tel:86-010-82450803