1 /* $NetBSD: queue.h,v 1.30 2001/06/22 06:18:22 chs Exp $ */ 2 3 /* 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)queue.h 8.5 (Berkeley) 8/20/94 36 */ 37 38 #ifndef _SYS_QUEUE_H_ 39 #define _SYS_QUEUE_H_ 40 41 /* 42 * This file defines five types of data structures: singly-linked lists, 43 * lists, simple queues, tail queues, and circular queues. 44 * 45 * A singly-linked list is headed by a single forward pointer. The 46 * elements are singly linked for minimum space and pointer manipulation 47 * overhead at the expense of O(n) removal for arbitrary elements. New 48 * elements can be added to the list after an existing element or at the 49 * head of the list. Elements being removed from the head of the list 50 * should use the explicit macro for this purpose for optimum 51 * efficiency. A singly-linked list may only be traversed in the forward 52 * direction. Singly-linked lists are ideal for applications with large 53 * datasets and few or no removals or for implementing a LIFO queue. 54 * 55 * A list is headed by a single forward pointer (or an array of forward 56 * pointers for a hash table header). The elements are doubly linked 57 * so that an arbitrary element can be removed without a need to 58 * traverse the list. New elements can be added to the list before 59 * or after an existing element or at the head of the list. A list 60 * may only be traversed in the forward direction. 61 * 62 * A simple queue is headed by a pair of pointers, one the head of the 63 * list and the other to the tail of the list. The elements are singly 64 * linked to save space, so only elements can only be removed from the 65 * head of the list. New elements can be added to the list after 66 * an existing element, at the head of the list, or at the end of the 67 * list. A simple queue may only be traversed in the forward direction. 68 * 69 * A tail queue is headed by a pair of pointers, one to the head of the 70 * list and the other to the tail of the list. The elements are doubly 71 * linked so that an arbitrary element can be removed without a need to 72 * traverse the list. New elements can be added to the list before or 73 * after an existing element, at the head of the list, or at the end of 74 * the list. A tail queue may be traversed in either direction. 75 * 76 * A circle queue is headed by a pair of pointers, one to the head of the 77 * list and the other to the tail of the list. The elements are doubly 78 * linked so that an arbitrary element can be removed without a need to 79 * traverse the list. New elements can be added to the list before or after 80 * an existing element, at the head of the list, or at the end of the list. 81 * A circle queue may be traversed in either direction, but has a more 82 * complex end of list detection. 83 * 84 * For details on the use of these macros, see the queue(3) manual page. 85 */ 86 87 /* 88 * List definitions. 89 */ 90 #define LIST_HEAD(name, type) \ 91 struct name { \ 92 struct type *lh_first; /* first element */ \ 93 } 94 95 #define LIST_HEAD_INITIALIZER(head) \ 96 { NULL } 97 98 #define LIST_ENTRY(type) \ 99 struct { \ 100 struct type *le_next; /* next element */ \ 101 struct type **le_prev; /* address of previous next element */ \ 102 } 103 104 /* 105 * List functions. 106 */ 107 #if defined(_KERNEL) && defined(QUEUEDEBUG) 108 #define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field) \ 109 if ((head)->lh_first && \ 110 (head)->lh_first->field.le_prev != &(head)->lh_first) \ 111 panic("LIST_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__); 112 #define QUEUEDEBUG_LIST_OP(elm, field) \ 113 if ((elm)->field.le_next && \ 114 (elm)->field.le_next->field.le_prev != \ 115 &(elm)->field.le_next) \ 116 panic("LIST_* forw %p %s:%d", (elm), __FILE__, __LINE__);\ 117 if (*(elm)->field.le_prev != (elm)) \ 118 panic("LIST_* back %p %s:%d", (elm), __FILE__, __LINE__); 119 #define QUEUEDEBUG_LIST_POSTREMOVE(elm, field) \ 120 (elm)->field.le_next = (void *)1L; \ 121 (elm)->field.le_prev = (void *)1L; 122 #else 123 #define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field) 124 #define QUEUEDEBUG_LIST_OP(elm, field) 125 #define QUEUEDEBUG_LIST_POSTREMOVE(elm, field) 126 #endif 127 128 #define LIST_INIT(head) do { \ 129 (head)->lh_first = NULL; \ 130 } while (/*CONSTCOND*/0) 131 132 #define LIST_INSERT_AFTER(listelm, elm, field) do { \ 133 QUEUEDEBUG_LIST_OP((listelm), field) \ 134 if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \ 135 (listelm)->field.le_next->field.le_prev = \ 136 &(elm)->field.le_next; \ 137 (listelm)->field.le_next = (elm); \ 138 (elm)->field.le_prev = &(listelm)->field.le_next; \ 139 } while (/*CONSTCOND*/0) 140 141 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \ 142 QUEUEDEBUG_LIST_OP((listelm), field) \ 143 (elm)->field.le_prev = (listelm)->field.le_prev; \ 144 (elm)->field.le_next = (listelm); \ 145 *(listelm)->field.le_prev = (elm); \ 146 (listelm)->field.le_prev = &(elm)->field.le_next; \ 147 } while (/*CONSTCOND*/0) 148 149 #define LIST_INSERT_HEAD(head, elm, field) do { \ 150 QUEUEDEBUG_LIST_INSERT_HEAD((head), (elm), field) \ 151 if (((elm)->field.le_next = (head)->lh_first) != NULL) \ 152 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\ 153 (head)->lh_first = (elm); \ 154 (elm)->field.le_prev = &(head)->lh_first; \ 155 } while (/*CONSTCOND*/0) 156 157 #define LIST_REMOVE(elm, field) do { \ 158 QUEUEDEBUG_LIST_OP((elm), field) \ 159 if ((elm)->field.le_next != NULL) \ 160 (elm)->field.le_next->field.le_prev = \ 161 (elm)->field.le_prev; \ 162 *(elm)->field.le_prev = (elm)->field.le_next; \ 163 QUEUEDEBUG_LIST_POSTREMOVE((elm), field) \ 164 } while (/*CONSTCOND*/0) 165 166 #define LIST_FOREACH(var, head, field) \ 167 for ((var) = ((head)->lh_first); \ 168 (var); \ 169 (var) = ((var)->field.le_next)) 170 171 /* 172 * List access methods. 173 */ 174 #define LIST_EMPTY(head) ((head)->lh_first == NULL) 175 #define LIST_FIRST(head) ((head)->lh_first) 176 #define LIST_NEXT(elm, field) ((elm)->field.le_next) 177 178 /* 179 * Singly-linked List definitions. 180 */ 181 #define SLIST_HEAD(name, type) \ 182 struct name { \ 183 struct type *slh_first; /* first element */ \ 184 } 185 186 #define SLIST_HEAD_INITIALIZER(head) \ 187 { NULL } 188 189 #define SLIST_ENTRY(type) \ 190 struct { \ 191 struct type *sle_next; /* next element */ \ 192 } 193 194 /* 195 * Singly-linked List functions. 196 */ 197 #define SLIST_EMPTY(head) ((head)->slh_first == NULL) 198 #define SLIST_FIRST(head) ((head)->slh_first) 199 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 200 201 #define SLIST_FOREACH(var, head, field) \ 202 for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next) 203 204 #define SLIST_INIT(head) do { \ 205 (head)->slh_first = NULL; \ 206 } while (/*CONSTCOND*/0) 207 208 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 209 (elm)->field.sle_next = (slistelm)->field.sle_next; \ 210 (slistelm)->field.sle_next = (elm); \ 211 } while (/*CONSTCOND*/0) 212 213 #define SLIST_INSERT_HEAD(head, elm, field) do { \ 214 (elm)->field.sle_next = (head)->slh_first; \ 215 (head)->slh_first = (elm); \ 216 } while (/*CONSTCOND*/0) 217 218 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 219 220 #define SLIST_REMOVE_HEAD(head, field) do { \ 221 (head)->slh_first = (head)->slh_first->field.sle_next; \ 222 } while (/*CONSTCOND*/0) 223 224 #define SLIST_REMOVE(head, elm, type, field) do { \ 225 if ((head)->slh_first == (elm)) { \ 226 SLIST_REMOVE_HEAD((head), field); \ 227 } \ 228 else { \ 229 struct type *curelm = (head)->slh_first; \ 230 while(curelm->field.sle_next != (elm)) \ 231 curelm = curelm->field.sle_next; \ 232 curelm->field.sle_next = \ 233 curelm->field.sle_next->field.sle_next; \ 234 } \ 235 } while (/*CONSTCOND*/0) 236 237 /* 238 * Simple queue definitions. 239 */ 240 #define SIMPLEQ_HEAD(name, type) \ 241 struct name { \ 242 struct type *sqh_first; /* first element */ \ 243 struct type **sqh_last; /* addr of last next element */ \ 244 } 245 246 #define SIMPLEQ_HEAD_INITIALIZER(head) \ 247 { NULL, &(head).sqh_first } 248 249 #define SIMPLEQ_ENTRY(type) \ 250 struct { \ 251 struct type *sqe_next; /* next element */ \ 252 } 253 254 /* 255 * Simple queue functions. 256 */ 257 #define SIMPLEQ_INIT(head) do { \ 258 (head)->sqh_first = NULL; \ 259 (head)->sqh_last = &(head)->sqh_first; \ 260 } while (/*CONSTCOND*/0) 261 262 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do { \ 263 if (((elm)->field.sqe_next = (head)->sqh_first) == NULL) \ 264 (head)->sqh_last = &(elm)->field.sqe_next; \ 265 (head)->sqh_first = (elm); \ 266 } while (/*CONSTCOND*/0) 267 268 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do { \ 269 (elm)->field.sqe_next = NULL; \ 270 *(head)->sqh_last = (elm); \ 271 (head)->sqh_last = &(elm)->field.sqe_next; \ 272 } while (/*CONSTCOND*/0) 273 274 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 275 if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\ 276 (head)->sqh_last = &(elm)->field.sqe_next; \ 277 (listelm)->field.sqe_next = (elm); \ 278 } while (/*CONSTCOND*/0) 279 280 #define SIMPLEQ_REMOVE_HEAD(head, elm, field) do { \ 281 if (((head)->sqh_first = (elm)->field.sqe_next) == NULL) \ 282 (head)->sqh_last = &(head)->sqh_first; \ 283 } while (/*CONSTCOND*/0) 284 285 #define SIMPLEQ_FOREACH(var, head, field) \ 286 for ((var) = ((head)->sqh_first); \ 287 (var); \ 288 (var) = ((var)->field.sqe_next)) 289 290 /* 291 * Simple queue access methods. 292 */ 293 #define SIMPLEQ_EMPTY(head) ((head)->sqh_first == NULL) 294 #define SIMPLEQ_FIRST(head) ((head)->sqh_first) 295 #define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next) 296 297 /* 298 * Tail queue definitions. 299 */ 300 #define TAILQ_HEAD(name, type) \ 301 struct name { \ 302 struct type *tqh_first; /* first element */ \ 303 struct type **tqh_last; /* addr of last next element */ \ 304 } 305 306 #define TAILQ_HEAD_INITIALIZER(head) \ 307 { NULL, &(head).tqh_first } 308 309 #define TAILQ_ENTRY(type) \ 310 struct { \ 311 struct type *tqe_next; /* next element */ \ 312 struct type **tqe_prev; /* address of previous next element */ \ 313 } 314 315 /* 316 * Tail queue functions. 317 */ 318 #if defined(_KERNEL) && defined(QUEUEDEBUG) 319 #define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field) \ 320 if ((head)->tqh_first && \ 321 (head)->tqh_first->field.tqe_prev != &(head)->tqh_first) \ 322 panic("TAILQ_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__); 323 #define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field) \ 324 if (*(head)->tqh_last != NULL) \ 325 panic("TAILQ_INSERT_TAIL %p %s:%d", (head), __FILE__, __LINE__); 326 #define QUEUEDEBUG_TAILQ_OP(elm, field) \ 327 if ((elm)->field.tqe_next && \ 328 (elm)->field.tqe_next->field.tqe_prev != \ 329 &(elm)->field.tqe_next) \ 330 panic("TAILQ_* forw %p %s:%d", (elm), __FILE__, __LINE__);\ 331 if (*(elm)->field.tqe_prev != (elm)) \ 332 panic("TAILQ_* back %p %s:%d", (elm), __FILE__, __LINE__); 333 #define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field) \ 334 (elm)->field.tqe_next = (void *)1L; \ 335 (elm)->field.tqe_prev = (void *)1L; 336 #else 337 #define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field) 338 #define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field) 339 #define QUEUEDEBUG_TAILQ_OP(elm, field) 340 #define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field) 341 #endif 342 343 #define TAILQ_INIT(head) do { \ 344 (head)->tqh_first = NULL; \ 345 (head)->tqh_last = &(head)->tqh_first; \ 346 } while (/*CONSTCOND*/0) 347 348 #define TAILQ_INSERT_HEAD(head, elm, field) do { \ 349 QUEUEDEBUG_TAILQ_INSERT_HEAD((head), (elm), field) \ 350 if (((elm)->field.tqe_next = (head)->tqh_first) != NULL) \ 351 (head)->tqh_first->field.tqe_prev = \ 352 &(elm)->field.tqe_next; \ 353 else \ 354 (head)->tqh_last = &(elm)->field.tqe_next; \ 355 (head)->tqh_first = (elm); \ 356 (elm)->field.tqe_prev = &(head)->tqh_first; \ 357 } while (/*CONSTCOND*/0) 358 359 #define TAILQ_INSERT_TAIL(head, elm, field) do { \ 360 QUEUEDEBUG_TAILQ_INSERT_TAIL((head), (elm), field) \ 361 (elm)->field.tqe_next = NULL; \ 362 (elm)->field.tqe_prev = (head)->tqh_last; \ 363 *(head)->tqh_last = (elm); \ 364 (head)->tqh_last = &(elm)->field.tqe_next; \ 365 } while (/*CONSTCOND*/0) 366 367 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 368 QUEUEDEBUG_TAILQ_OP((listelm), field) \ 369 if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\ 370 (elm)->field.tqe_next->field.tqe_prev = \ 371 &(elm)->field.tqe_next; \ 372 else \ 373 (head)->tqh_last = &(elm)->field.tqe_next; \ 374 (listelm)->field.tqe_next = (elm); \ 375 (elm)->field.tqe_prev = &(listelm)->field.tqe_next; \ 376 } while (/*CONSTCOND*/0) 377 378 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 379 QUEUEDEBUG_TAILQ_OP((listelm), field) \ 380 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 381 (elm)->field.tqe_next = (listelm); \ 382 *(listelm)->field.tqe_prev = (elm); \ 383 (listelm)->field.tqe_prev = &(elm)->field.tqe_next; \ 384 } while (/*CONSTCOND*/0) 385 386 #define TAILQ_REMOVE(head, elm, field) do { \ 387 QUEUEDEBUG_TAILQ_OP((elm), field) \ 388 if (((elm)->field.tqe_next) != NULL) \ 389 (elm)->field.tqe_next->field.tqe_prev = \ 390 (elm)->field.tqe_prev; \ 391 else \ 392 (head)->tqh_last = (elm)->field.tqe_prev; \ 393 *(elm)->field.tqe_prev = (elm)->field.tqe_next; \ 394 QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field); \ 395 } while (/*CONSTCOND*/0) 396 397 /* 398 * Tail queue access methods. 399 */ 400 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL) 401 #define TAILQ_FIRST(head) ((head)->tqh_first) 402 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 403 404 #define TAILQ_LAST(head, headname) \ 405 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 406 #define TAILQ_PREV(elm, headname, field) \ 407 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 408 409 #define TAILQ_FOREACH(var, head, field) \ 410 for ((var) = ((head)->tqh_first); \ 411 (var); \ 412 (var) = ((var)->field.tqe_next)) 413 414 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 415 for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last)); \ 416 (var); \ 417 (var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last))) 418 419 /* 420 * Circular queue definitions. 421 */ 422 #define CIRCLEQ_HEAD(name, type) \ 423 struct name { \ 424 struct type *cqh_first; /* first element */ \ 425 struct type *cqh_last; /* last element */ \ 426 } 427 428 #define CIRCLEQ_HEAD_INITIALIZER(head) \ 429 { (void *)&head, (void *)&head } 430 431 #define CIRCLEQ_ENTRY(type) \ 432 struct { \ 433 struct type *cqe_next; /* next element */ \ 434 struct type *cqe_prev; /* previous element */ \ 435 } 436 437 /* 438 * Circular queue functions. 439 */ 440 #define CIRCLEQ_INIT(head) do { \ 441 (head)->cqh_first = (void *)(head); \ 442 (head)->cqh_last = (void *)(head); \ 443 } while (/*CONSTCOND*/0) 444 445 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 446 (elm)->field.cqe_next = (listelm)->field.cqe_next; \ 447 (elm)->field.cqe_prev = (listelm); \ 448 if ((listelm)->field.cqe_next == (void *)(head)) \ 449 (head)->cqh_last = (elm); \ 450 else \ 451 (listelm)->field.cqe_next->field.cqe_prev = (elm); \ 452 (listelm)->field.cqe_next = (elm); \ 453 } while (/*CONSTCOND*/0) 454 455 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do { \ 456 (elm)->field.cqe_next = (listelm); \ 457 (elm)->field.cqe_prev = (listelm)->field.cqe_prev; \ 458 if ((listelm)->field.cqe_prev == (void *)(head)) \ 459 (head)->cqh_first = (elm); \ 460 else \ 461 (listelm)->field.cqe_prev->field.cqe_next = (elm); \ 462 (listelm)->field.cqe_prev = (elm); \ 463 } while (/*CONSTCOND*/0) 464 465 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do { \ 466 (elm)->field.cqe_next = (head)->cqh_first; \ 467 (elm)->field.cqe_prev = (void *)(head); \ 468 if ((head)->cqh_last == (void *)(head)) \ 469 (head)->cqh_last = (elm); \ 470 else \ 471 (head)->cqh_first->field.cqe_prev = (elm); \ 472 (head)->cqh_first = (elm); \ 473 } while (/*CONSTCOND*/0) 474 475 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do { \ 476 (elm)->field.cqe_next = (void *)(head); \ 477 (elm)->field.cqe_prev = (head)->cqh_last; \ 478 if ((head)->cqh_first == (void *)(head)) \ 479 (head)->cqh_first = (elm); \ 480 else \ 481 (head)->cqh_last->field.cqe_next = (elm); \ 482 (head)->cqh_last = (elm); \ 483 } while (/*CONSTCOND*/0) 484 485 #define CIRCLEQ_REMOVE(head, elm, field) do { \ 486 if ((elm)->field.cqe_next == (void *)(head)) \ 487 (head)->cqh_last = (elm)->field.cqe_prev; \ 488 else \ 489 (elm)->field.cqe_next->field.cqe_prev = \ 490 (elm)->field.cqe_prev; \ 491 if ((elm)->field.cqe_prev == (void *)(head)) \ 492 (head)->cqh_first = (elm)->field.cqe_next; \ 493 else \ 494 (elm)->field.cqe_prev->field.cqe_next = \ 495 (elm)->field.cqe_next; \ 496 } while (/*CONSTCOND*/0) 497 498 #define CIRCLEQ_FOREACH(var, head, field) \ 499 for ((var) = ((head)->cqh_first); \ 500 (var) != (void *)(head); \ 501 (var) = ((var)->field.cqe_next)) 502 503 #define CIRCLEQ_FOREACH_REVERSE(var, head, field) \ 504 for ((var) = ((head)->cqh_last); \ 505 (var) != (void *)(head); \ 506 (var) = ((var)->field.cqe_prev)) 507 508 /* 509 * Circular queue access methods. 510 */ 511 #define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head)) 512 #define CIRCLEQ_FIRST(head) ((head)->cqh_first) 513 #define CIRCLEQ_LAST(head) ((head)->cqh_last) 514 #define CIRCLEQ_NEXT(elm, field) ((elm)->field.cqe_next) 515 #define CIRCLEQ_PREV(elm, field) ((elm)->field.cqe_prev) 516 #endif /* !_SYS_QUEUE_H_ */ 517