QTAILQ is a doubly linked list, with a pointer-to-pointer to the last element from the head, and the previous element from each node. But if you squint enough, QTAILQ becomes a combination of a singly-linked forwards list, and another singly-linked list which goes backwards and is circular. This is the idea that lets QTAILQ implement reverse iteration: only, because the backwards list points inside the node, accessing the previous element needs to go two steps back and one forwards. What this patch does is implement it in these terms, without actually changing the in-memory layout at all. The coexistence of the two lists is realized by making QTAILQ_HEAD and QTAILQ_ENTRY unions of the forwards pointer and a generic QTailQLink node. Thq QTailQLink can walk the list in both directions; the union is needed so that the forwards pointer can have the correct type, as a sort of poor man's template. While there are other ways to get the same layout without a union, this one has the advantage of simpler operation in the debugger, because the fields tqh_first and tqe_next still exist as before the patch. Those fields are also used by scripts/qemugdb/mtree.py, so it's a good idea to preserve them. The advantage of the new representation is that the two-back-one-forward dance done by backwards accesses can be done all while operating on QTailQLinks. No casting to the head struct is needed anymore because, even though the QTailQLink's forward pointer is a void *, we can use typeof to recover the correct type. This patch only changes the implementation, not the interface. The next patch will remove the head struct name from the backwards visit macros. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
497 lines
24 KiB
C
497 lines
24 KiB
C
/* $NetBSD: queue.h,v 1.52 2009/04/20 09:56:08 mschuett Exp $ */
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/*
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* QEMU version: Copy from netbsd, removed debug code, removed some of
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* the implementations. Left in singly-linked lists, lists, simple
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* queues, and tail queues.
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*/
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/*
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)queue.h 8.5 (Berkeley) 8/20/94
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*/
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#ifndef QEMU_SYS_QUEUE_H
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#define QEMU_SYS_QUEUE_H
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/*
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* This file defines four types of data structures: singly-linked lists,
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* lists, simple queues, and tail queues.
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*
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* A singly-linked list is headed by a single forward pointer. The
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* elements are singly linked for minimum space and pointer manipulation
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* overhead at the expense of O(n) removal for arbitrary elements. New
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* elements can be added to the list after an existing element or at the
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* head of the list. Elements being removed from the head of the list
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* should use the explicit macro for this purpose for optimum
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* efficiency. A singly-linked list may only be traversed in the forward
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* direction. Singly-linked lists are ideal for applications with large
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* datasets and few or no removals or for implementing a LIFO queue.
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*
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* A list is headed by a single forward pointer (or an array of forward
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* pointers for a hash table header). The elements are doubly linked
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* so that an arbitrary element can be removed without a need to
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* traverse the list. New elements can be added to the list before
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* or after an existing element or at the head of the list. A list
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* may only be traversed in the forward direction.
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*
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* A simple queue is headed by a pair of pointers, one the head of the
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* list and the other to the tail of the list. The elements are singly
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* linked to save space, so elements can only be removed from the
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* head of the list. New elements can be added to the list after
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* an existing element, at the head of the list, or at the end of the
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* list. A simple queue may only be traversed in the forward direction.
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*
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* A tail queue is headed by a pair of pointers, one to the head of the
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* list and the other to the tail of the list. The elements are doubly
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* linked so that an arbitrary element can be removed without a need to
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* traverse the list. New elements can be added to the list before or
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* after an existing element, at the head of the list, or at the end of
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* the list. A tail queue may be traversed in either direction.
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*
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* For details on the use of these macros, see the queue(3) manual page.
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*/
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#include "qemu/atomic.h" /* for smp_wmb() */
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/*
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* List definitions.
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*/
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#define QLIST_HEAD(name, type) \
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struct name { \
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struct type *lh_first; /* first element */ \
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}
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#define QLIST_HEAD_INITIALIZER(head) \
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{ NULL }
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#define QLIST_ENTRY(type) \
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struct { \
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struct type *le_next; /* next element */ \
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struct type **le_prev; /* address of previous next element */ \
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}
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/*
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* List functions.
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*/
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#define QLIST_INIT(head) do { \
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(head)->lh_first = NULL; \
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} while (/*CONSTCOND*/0)
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#define QLIST_SWAP(dstlist, srclist, field) do { \
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void *tmplist; \
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tmplist = (srclist)->lh_first; \
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(srclist)->lh_first = (dstlist)->lh_first; \
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if ((srclist)->lh_first != NULL) { \
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(srclist)->lh_first->field.le_prev = &(srclist)->lh_first; \
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} \
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(dstlist)->lh_first = tmplist; \
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if ((dstlist)->lh_first != NULL) { \
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(dstlist)->lh_first->field.le_prev = &(dstlist)->lh_first; \
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} \
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} while (/*CONSTCOND*/0)
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#define QLIST_INSERT_AFTER(listelm, elm, field) do { \
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if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \
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(listelm)->field.le_next->field.le_prev = \
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&(elm)->field.le_next; \
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(listelm)->field.le_next = (elm); \
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(elm)->field.le_prev = &(listelm)->field.le_next; \
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} while (/*CONSTCOND*/0)
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#define QLIST_INSERT_BEFORE(listelm, elm, field) do { \
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(elm)->field.le_prev = (listelm)->field.le_prev; \
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(elm)->field.le_next = (listelm); \
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*(listelm)->field.le_prev = (elm); \
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(listelm)->field.le_prev = &(elm)->field.le_next; \
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} while (/*CONSTCOND*/0)
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#define QLIST_INSERT_HEAD(head, elm, field) do { \
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if (((elm)->field.le_next = (head)->lh_first) != NULL) \
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(head)->lh_first->field.le_prev = &(elm)->field.le_next;\
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(head)->lh_first = (elm); \
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(elm)->field.le_prev = &(head)->lh_first; \
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} while (/*CONSTCOND*/0)
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#define QLIST_REMOVE(elm, field) do { \
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if ((elm)->field.le_next != NULL) \
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(elm)->field.le_next->field.le_prev = \
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(elm)->field.le_prev; \
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*(elm)->field.le_prev = (elm)->field.le_next; \
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} while (/*CONSTCOND*/0)
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#define QLIST_FOREACH(var, head, field) \
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for ((var) = ((head)->lh_first); \
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(var); \
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(var) = ((var)->field.le_next))
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#define QLIST_FOREACH_SAFE(var, head, field, next_var) \
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for ((var) = ((head)->lh_first); \
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(var) && ((next_var) = ((var)->field.le_next), 1); \
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(var) = (next_var))
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/*
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* List access methods.
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*/
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#define QLIST_EMPTY(head) ((head)->lh_first == NULL)
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#define QLIST_FIRST(head) ((head)->lh_first)
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#define QLIST_NEXT(elm, field) ((elm)->field.le_next)
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/*
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* Singly-linked List definitions.
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*/
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#define QSLIST_HEAD(name, type) \
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struct name { \
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struct type *slh_first; /* first element */ \
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}
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#define QSLIST_HEAD_INITIALIZER(head) \
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{ NULL }
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#define QSLIST_ENTRY(type) \
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struct { \
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struct type *sle_next; /* next element */ \
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}
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/*
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* Singly-linked List functions.
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*/
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#define QSLIST_INIT(head) do { \
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(head)->slh_first = NULL; \
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} while (/*CONSTCOND*/0)
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#define QSLIST_INSERT_AFTER(slistelm, elm, field) do { \
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(elm)->field.sle_next = (slistelm)->field.sle_next; \
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(slistelm)->field.sle_next = (elm); \
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} while (/*CONSTCOND*/0)
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#define QSLIST_INSERT_HEAD(head, elm, field) do { \
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(elm)->field.sle_next = (head)->slh_first; \
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(head)->slh_first = (elm); \
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} while (/*CONSTCOND*/0)
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#define QSLIST_INSERT_HEAD_ATOMIC(head, elm, field) do { \
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typeof(elm) save_sle_next; \
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do { \
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save_sle_next = (elm)->field.sle_next = (head)->slh_first; \
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} while (atomic_cmpxchg(&(head)->slh_first, save_sle_next, (elm)) != \
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save_sle_next); \
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} while (/*CONSTCOND*/0)
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#define QSLIST_MOVE_ATOMIC(dest, src) do { \
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(dest)->slh_first = atomic_xchg(&(src)->slh_first, NULL); \
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} while (/*CONSTCOND*/0)
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#define QSLIST_REMOVE_HEAD(head, field) do { \
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(head)->slh_first = (head)->slh_first->field.sle_next; \
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} while (/*CONSTCOND*/0)
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#define QSLIST_REMOVE_AFTER(slistelm, field) do { \
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(slistelm)->field.sle_next = \
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QSLIST_NEXT(QSLIST_NEXT((slistelm), field), field); \
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} while (/*CONSTCOND*/0)
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#define QSLIST_FOREACH(var, head, field) \
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for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
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#define QSLIST_FOREACH_SAFE(var, head, field, tvar) \
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for ((var) = QSLIST_FIRST((head)); \
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(var) && ((tvar) = QSLIST_NEXT((var), field), 1); \
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(var) = (tvar))
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/*
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* Singly-linked List access methods.
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*/
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#define QSLIST_EMPTY(head) ((head)->slh_first == NULL)
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#define QSLIST_FIRST(head) ((head)->slh_first)
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#define QSLIST_NEXT(elm, field) ((elm)->field.sle_next)
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/*
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* Simple queue definitions.
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*/
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#define QSIMPLEQ_HEAD(name, type) \
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struct name { \
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struct type *sqh_first; /* first element */ \
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struct type **sqh_last; /* addr of last next element */ \
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}
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#define QSIMPLEQ_HEAD_INITIALIZER(head) \
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{ NULL, &(head).sqh_first }
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#define QSIMPLEQ_ENTRY(type) \
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struct { \
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struct type *sqe_next; /* next element */ \
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}
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/*
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* Simple queue functions.
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*/
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#define QSIMPLEQ_INIT(head) do { \
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(head)->sqh_first = NULL; \
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(head)->sqh_last = &(head)->sqh_first; \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_INSERT_HEAD(head, elm, field) do { \
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if (((elm)->field.sqe_next = (head)->sqh_first) == NULL) \
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(head)->sqh_last = &(elm)->field.sqe_next; \
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(head)->sqh_first = (elm); \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_INSERT_TAIL(head, elm, field) do { \
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(elm)->field.sqe_next = NULL; \
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*(head)->sqh_last = (elm); \
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(head)->sqh_last = &(elm)->field.sqe_next; \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { \
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if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL) \
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(head)->sqh_last = &(elm)->field.sqe_next; \
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(listelm)->field.sqe_next = (elm); \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_REMOVE_HEAD(head, field) do { \
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if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL)\
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(head)->sqh_last = &(head)->sqh_first; \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_SPLIT_AFTER(head, elm, field, removed) do { \
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QSIMPLEQ_INIT(removed); \
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if (((removed)->sqh_first = (head)->sqh_first) != NULL) { \
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if (((head)->sqh_first = (elm)->field.sqe_next) == NULL) { \
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(head)->sqh_last = &(head)->sqh_first; \
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} \
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(removed)->sqh_last = &(elm)->field.sqe_next; \
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(elm)->field.sqe_next = NULL; \
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} \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_REMOVE(head, elm, type, field) do { \
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if ((head)->sqh_first == (elm)) { \
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QSIMPLEQ_REMOVE_HEAD((head), field); \
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} else { \
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struct type *curelm = (head)->sqh_first; \
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while (curelm->field.sqe_next != (elm)) \
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curelm = curelm->field.sqe_next; \
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if ((curelm->field.sqe_next = \
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curelm->field.sqe_next->field.sqe_next) == NULL) \
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(head)->sqh_last = &(curelm)->field.sqe_next; \
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} \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_FOREACH(var, head, field) \
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for ((var) = ((head)->sqh_first); \
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(var); \
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(var) = ((var)->field.sqe_next))
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#define QSIMPLEQ_FOREACH_SAFE(var, head, field, next) \
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for ((var) = ((head)->sqh_first); \
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(var) && ((next = ((var)->field.sqe_next)), 1); \
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(var) = (next))
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#define QSIMPLEQ_CONCAT(head1, head2) do { \
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if (!QSIMPLEQ_EMPTY((head2))) { \
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*(head1)->sqh_last = (head2)->sqh_first; \
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(head1)->sqh_last = (head2)->sqh_last; \
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QSIMPLEQ_INIT((head2)); \
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} \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_PREPEND(head1, head2) do { \
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if (!QSIMPLEQ_EMPTY((head2))) { \
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*(head2)->sqh_last = (head1)->sqh_first; \
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(head1)->sqh_first = (head2)->sqh_first; \
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QSIMPLEQ_INIT((head2)); \
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} \
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} while (/*CONSTCOND*/0)
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#define QSIMPLEQ_LAST(head, type, field) \
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(QSIMPLEQ_EMPTY((head)) ? \
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NULL : \
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((struct type *)(void *) \
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((char *)((head)->sqh_last) - offsetof(struct type, field))))
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/*
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* Simple queue access methods.
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*/
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#define QSIMPLEQ_EMPTY_ATOMIC(head) (atomic_read(&((head)->sqh_first)) == NULL)
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#define QSIMPLEQ_EMPTY(head) ((head)->sqh_first == NULL)
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#define QSIMPLEQ_FIRST(head) ((head)->sqh_first)
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#define QSIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next)
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typedef struct QTailQLink {
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void *tql_next;
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struct QTailQLink *tql_prev;
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} QTailQLink;
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/*
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* Tail queue definitions. The union acts as a poor man template, as if
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* it were QTailQLink<type>.
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*/
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#define QTAILQ_HEAD(name, type) \
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union name { \
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struct type *tqh_first; /* first element */ \
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QTailQLink tqh_circ; /* link for circular backwards list */ \
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}
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#define QTAILQ_HEAD_INITIALIZER(head) \
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{ .tqh_circ = { NULL, &(head).tqh_circ } }
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#define QTAILQ_ENTRY(type) \
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union { \
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struct type *tqe_next; /* next element */ \
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QTailQLink tqe_circ; /* link for circular backwards list */ \
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}
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/*
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* Tail queue functions.
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*/
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#define QTAILQ_INIT(head) do { \
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(head)->tqh_first = NULL; \
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(head)->tqh_circ.tql_prev = &(head)->tqh_circ; \
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} while (/*CONSTCOND*/0)
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#define QTAILQ_INSERT_HEAD(head, elm, field) do { \
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if (((elm)->field.tqe_next = (head)->tqh_first) != NULL) \
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(head)->tqh_first->field.tqe_circ.tql_prev = \
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&(elm)->field.tqe_circ; \
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else \
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(head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ; \
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(head)->tqh_first = (elm); \
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(elm)->field.tqe_circ.tql_prev = &(head)->tqh_circ; \
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} while (/*CONSTCOND*/0)
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#define QTAILQ_INSERT_TAIL(head, elm, field) do { \
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(elm)->field.tqe_next = NULL; \
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(elm)->field.tqe_circ.tql_prev = (head)->tqh_circ.tql_prev; \
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(head)->tqh_circ.tql_prev->tql_next = (elm); \
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(head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ; \
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} while (/*CONSTCOND*/0)
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#define QTAILQ_INSERT_AFTER(head, listelm, elm, field) do { \
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if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
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(elm)->field.tqe_next->field.tqe_circ.tql_prev = \
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&(elm)->field.tqe_circ; \
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else \
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(head)->tqh_circ.tql_prev = &(elm)->field.tqe_circ; \
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(listelm)->field.tqe_next = (elm); \
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(elm)->field.tqe_circ.tql_prev = &(listelm)->field.tqe_circ; \
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} while (/*CONSTCOND*/0)
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#define QTAILQ_INSERT_BEFORE(listelm, elm, field) do { \
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(elm)->field.tqe_circ.tql_prev = (listelm)->field.tqe_circ.tql_prev; \
|
|
(elm)->field.tqe_next = (listelm); \
|
|
(listelm)->field.tqe_circ.tql_prev->tql_next = (elm); \
|
|
(listelm)->field.tqe_circ.tql_prev = &(elm)->field.tqe_circ; \
|
|
} while (/*CONSTCOND*/0)
|
|
|
|
#define QTAILQ_REMOVE(head, elm, field) do { \
|
|
if (((elm)->field.tqe_next) != NULL) \
|
|
(elm)->field.tqe_next->field.tqe_circ.tql_prev = \
|
|
(elm)->field.tqe_circ.tql_prev; \
|
|
else \
|
|
(head)->tqh_circ.tql_prev = (elm)->field.tqe_circ.tql_prev; \
|
|
(elm)->field.tqe_circ.tql_prev->tql_next = (elm)->field.tqe_next; \
|
|
(elm)->field.tqe_circ.tql_prev = NULL; \
|
|
} while (/*CONSTCOND*/0)
|
|
|
|
#define QTAILQ_FOREACH(var, head, field) \
|
|
for ((var) = ((head)->tqh_first); \
|
|
(var); \
|
|
(var) = ((var)->field.tqe_next))
|
|
|
|
#define QTAILQ_FOREACH_SAFE(var, head, field, next_var) \
|
|
for ((var) = ((head)->tqh_first); \
|
|
(var) && ((next_var) = ((var)->field.tqe_next), 1); \
|
|
(var) = (next_var))
|
|
|
|
#define QTAILQ_FOREACH_REVERSE(var, head, headname, field) \
|
|
for ((var) = QTAILQ_LAST(head, headname); \
|
|
(var); \
|
|
(var) = QTAILQ_PREV(var, headname, field))
|
|
|
|
#define QTAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, prev_var) \
|
|
for ((var) = QTAILQ_LAST(head, headname); \
|
|
(var) && ((prev_var) = QTAILQ_PREV(var, headname, field)); \
|
|
(var) = (prev_var))
|
|
|
|
/*
|
|
* Tail queue access methods.
|
|
*/
|
|
#define QTAILQ_EMPTY(head) ((head)->tqh_first == NULL)
|
|
#define QTAILQ_FIRST(head) ((head)->tqh_first)
|
|
#define QTAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
|
|
#define QTAILQ_IN_USE(elm, field) ((elm)->field.tqe_circ.tql_prev != NULL)
|
|
|
|
#define QTAILQ_LINK_PREV(link) \
|
|
((link).tql_prev->tql_prev->tql_next)
|
|
#define QTAILQ_LAST(head, headname) \
|
|
((typeof((head)->tqh_first)) QTAILQ_LINK_PREV((head)->tqh_circ))
|
|
#define QTAILQ_PREV(elm, headname, field) \
|
|
((typeof((elm)->field.tqe_next)) QTAILQ_LINK_PREV((elm)->field.tqe_circ))
|
|
|
|
#define field_at_offset(base, offset, type) \
|
|
((type *) (((char *) (base)) + (offset)))
|
|
|
|
/*
|
|
* Raw access of elements of a tail queue head. Offsets are all zero
|
|
* because it's a union.
|
|
*/
|
|
#define QTAILQ_RAW_FIRST(head) \
|
|
field_at_offset(head, 0, void *)
|
|
#define QTAILQ_RAW_TQH_CIRC(head) \
|
|
field_at_offset(head, 0, QTailQLink)
|
|
|
|
/*
|
|
* Raw access of elements of a tail entry
|
|
*/
|
|
#define QTAILQ_RAW_NEXT(elm, entry) \
|
|
field_at_offset(elm, entry, void *)
|
|
#define QTAILQ_RAW_TQE_CIRC(elm, entry) \
|
|
field_at_offset(elm, entry, QTailQLink)
|
|
/*
|
|
* Tail queue traversal using pointer arithmetic.
|
|
*/
|
|
#define QTAILQ_RAW_FOREACH(elm, head, entry) \
|
|
for ((elm) = *QTAILQ_RAW_FIRST(head); \
|
|
(elm); \
|
|
(elm) = *QTAILQ_RAW_NEXT(elm, entry))
|
|
/*
|
|
* Tail queue insertion using pointer arithmetic.
|
|
*/
|
|
#define QTAILQ_RAW_INSERT_TAIL(head, elm, entry) do { \
|
|
*QTAILQ_RAW_NEXT(elm, entry) = NULL; \
|
|
QTAILQ_RAW_TQE_CIRC(elm, entry)->tql_prev = QTAILQ_RAW_TQH_CIRC(head)->tql_prev; \
|
|
QTAILQ_RAW_TQH_CIRC(head)->tql_prev->tql_next = (elm); \
|
|
QTAILQ_RAW_TQH_CIRC(head)->tql_prev = QTAILQ_RAW_TQE_CIRC(elm, entry); \
|
|
} while (/*CONSTCOND*/0)
|
|
|
|
#endif /* QEMU_SYS_QUEUE_H */
|