linuxthreads/queue.h

   1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
   2 /* threads for Linux.                                                   */
   3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
   4 /*                                                                      */
   5 /* This program is free software; you can redistribute it and/or        */
   6 /* modify it under the terms of the GNU Library General Public License  */
   7 /* as published by the Free Software Foundation; either version 2       */
   8 /* of the License, or (at your option) any later version.               */
   9 /*                                                                      */
  10 /* This program is distributed in the hope that it will be useful,      */
  11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
  12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
  13 /* GNU Library General Public License for more details.                 */
  14
  15 /* Waiting queues */
  16
  17 typedef struct _pthread_queue pthread_queue;
  18
  19 static inline void queue_init(pthread_queue * q)
  20 {
  21   q->head = q->tail = NULL;
  22 }
  23
  24 static inline void enqueue(pthread_queue * q, pthread_descr th)
  25 {
  26   int prio;
  27   pthread_descr * elt;
  28
  29   ASSERT(th->p_nextwaiting == NULL);
  30   if (q->tail == NULL) {
  31     q->head = th;
  32     q->tail = th;
  33     return;
  34   }
  35   prio = th->p_priority;
  36   if (prio > 0) {
  37     /* Insert in queue according to priority order */
  38     for (elt = &(q->head); *elt != NULL; elt = &((*elt)->p_nextwaiting)) {
  39       if (prio > (*elt)->p_priority) {
  40         th->p_nextwaiting = *elt;
  41         *elt = th;
  42         return;
  43       }
  44     }
  45   }
  46   /* Priority is no greater than any thread in the queue.
  47      Insert at end of queue */
  48   q->tail->p_nextwaiting = th;
  49   q->tail = th;
  50 }
  51
  52 static inline pthread_descr dequeue(pthread_queue * q)
  53 {
  54   pthread_descr th;
  55   th = q->head;
  56   if (th != NULL) {
  57     q->head = th->p_nextwaiting;
  58     if (q->head == NULL) q->tail = NULL;
  59     th->p_nextwaiting = NULL;
  60   }
  61   return th;
  62 }