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 /* Waiting queues are represented by lists of thread descriptors
  18    linked through their p_nextwaiting field.  The lists are kept
  19    sorted by decreasing priority, and then decreasing waiting time. */
  20
  21 static inline void enqueue(pthread_descr * q, pthread_descr th)
  22 {
  23   int prio = th->p_priority;
  24   ASSERT(th->p_nextwaiting == NULL);
  25   for (; *q != NULL; q = &((*q)->p_nextwaiting)) {
  26     if (prio > (*q)->p_priority) {
  27       th->p_nextwaiting = *q;
  28       *q = th;
  29       return;
  30     }
  31   }
  32   *q = th;
  33 }
  34
  35 static inline pthread_descr dequeue(pthread_descr * q)
  36 {
  37   pthread_descr th;
  38   th = *q;
  39   if (th != NULL) {
  40     *q = th->p_nextwaiting;
  41     th->p_nextwaiting = NULL;
  42   }
  43   return th;
  44 }
  45
  46 static inline int remove_from_queue(pthread_descr * q, pthread_descr th)
  47 {
  48   for (; *q != NULL; q = &((*q)->p_nextwaiting)) {
  49     if (*q == th) {
  50       *q = th->p_nextwaiting;
  51       th->p_nextwaiting = NULL;
  52       return 1;
  53     }
  54   }
  55   return 0;
  56 }
  57
  58 static inline int queue_is_empty(pthread_descr * q)
  59 {
  60     return *q == NULL;
  61 }