sched.c

   1 /*
   2  * Copyright (C) 2006-2007 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file sched.c paraslash's scheduling functions */
   8
   9 #include <dirent.h> /* readdir() */
  10 #include <assert.h>
  11 #include <sys/time.h>
  12
  13 #include "para.h"
  14 #include "ipc.h"
  15 #include "fd.h"
  16 #include "list.h"
  17 #include "sched.h"
  18 #include "string.h"
  19 #include "error.h"
  20
  21 static struct list_head pre_select_list, post_select_list;
  22 static int initialized;
  23
  24 static struct timeval now_struct;
  25 struct timeval *now = &now_struct;
  26
  27 static void sched_preselect(struct sched *s)
  28 {
  29         struct task *t, *tmp;
  30 again:
  31         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
  32                 t->pre_select(s, t);
  33 //              PARA_INFO_LOG("%s \n", t->status);
  34                 if (t->ret > 0)
  35                         continue;
  36                 if (!t->event_handler)
  37                         continue;
  38                 t->event_handler(t);
  39                 goto again;
  40         }
  41 }
  42
  43 static void sched_post_select(struct sched *s)
  44 {
  45         struct task *t, *tmp;
  46
  47         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
  48                 t->post_select(s, t);
  49 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
  50                 if (t->ret > 0 || !t->event_handler)
  51                         continue;
  52                 t->event_handler(t);
  53         }
  54 }
  55
  56 /**
  57  * the core function for all paraslash programs
  58  *
  59  * \param s pointer to the scheduler struct
  60  *
  61  * This function updates the global \a now pointer, calls all registered
  62  * pre_select hooks which may set the timeout and add any file descriptors to
  63  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
  64  * to the registered tasks by calling their post_select hook.
  65  *
  66  * \return Zero if no more tasks are left in either of the two lists, negative
  67  * if para_select returned an error.
  68  *
  69  * \sa task, now.
  70  */
  71 int sched(struct sched *s)
  72 {
  73         if (!initialized)
  74                 return -E_NOT_INITIALIZED;
  75         gettimeofday(now, NULL);
  76 again:
  77         FD_ZERO(&s->rfds);
  78         FD_ZERO(&s->wfds);
  79         s->timeout = s->default_timeout;
  80         s->max_fileno = -1;
  81         sched_preselect(s);
  82         s->select_ret = para_select(s->max_fileno + 1, &s->rfds,
  83                 &s->wfds, &s->timeout);
  84         if (s->select_ret < 0)
  85                 return s->select_ret;
  86         gettimeofday(now, NULL);
  87         sched_post_select(s);
  88         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
  89                 return 0;
  90         goto again;
  91 }
  92
  93 /**
  94  * initialize the paraslash scheduler
  95  */
  96 static void init_sched(void)
  97 {
  98         PARA_INFO_LOG("%s", "initializing scheduler\n");
  99         INIT_LIST_HEAD(&pre_select_list);
 100         INIT_LIST_HEAD(&post_select_list);
 101         initialized = 1;
 102 };
 103
 104 /**
 105  * add a task to the scheduler
 106  *
 107  * \param t the task to add
 108  *
 109  * If the pre_select pointer of \a t is not \p NULL, it is added to
 110  * the pre_select list of the scheduler. Same goes for post_select.
 111  *
 112  * \sa task::pre_select, task::post_select
 113  */
 114 void register_task(struct task *t)
 115 {
 116         if (!initialized)
 117                 init_sched();
 118         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 119         if (t->pre_select) {
 120                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 121                 para_list_add(&t->pre_select_node, &pre_select_list);
 122         }
 123         if (t->post_select) {
 124                 PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
 125                 para_list_add(&t->post_select_node, &post_select_list);
 126         }
 127 }
 128
 129 /**
 130  * remove a task from the scheduler
 131  *
 132  * \param t the task to remove
 133  *
 134  * If the pre_select pointer of \a t is not \p NULL, it is removed from
 135  * the pre_select list of the scheduler. Same goes for \a post_select.
 136  */
 137 void unregister_task(struct task *t)
 138 {
 139         if (!initialized)
 140                 return;
 141         PARA_INFO_LOG("unregistering %s (%p)\n", t->status, t);
 142         if (t->pre_select)
 143                 list_del(&t->pre_select_node);
 144         if (t->post_select)
 145                 list_del(&t->post_select_node);
 146 };
 147
 148 /**
 149  * unregister all tasks
 150  *
 151  * This will cause \a sched() to return immediately because both the
 152  * \a pre_select_list and the \a post_select_list are empty.
 153  */
 154 void sched_shutdown(void)
 155 {
 156         struct task *t, *tmp;
 157
 158         if (!initialized)
 159                 return;
 160         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
 161                 unregister_task(t);
 162         /* remove tasks which do not have a pre_select hook */
 163         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
 164                 unregister_task(t);
 165         initialized = 0;
 166 };
 167
 168 /**
 169  * get the list of all registered tasks.
 170  *
 171  * \return the task list
 172  *
 173  * Each entry of the list contains an identifier which is simply a hex number
 174  * that may be used in \a kill_task() to terminate the task.
 175  * The result ist dynamically allocated and must be freed by the caller.
 176  */
 177 char *get_task_list(void)
 178 {
 179         struct task *t, *tmp;
 180         char *msg = NULL;
 181
 182         if (!initialized)
 183                 return NULL;
 184         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 185                 char *tmp_msg;
 186                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 187                 free(msg);
 188                 msg = tmp_msg;
 189         }
 190         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 191                 char *tmp_msg;
 192 //              if (t->pre_select)
 193 //                      continue;
 194                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 195                 free(msg);
 196                 msg = tmp_msg;
 197         }
 198         //PARA_DEBUG_LOG("task list:\n%s", msg);
 199         return msg;
 200 }
 201
 202 /**
 203  * simulate an error for the given task
 204  *
 205  * \param id the task identifier
 206  *
 207  * Find the task identified by \a id, set the tasks' return value to
 208  * \p -E_TASK_KILLED and call the event handler of the task.
 209  *
 210  * \return Positive on success, negative on errors (e.g. if \a id does not
 211  * correspond to a registered task).
 212  */
 213 int kill_task(char *id)
 214 {
 215         struct task *t, *tmp;
 216         char buf[20];
 217
 218         if (!initialized)
 219                 return -E_NOT_INITIALIZED;
 220         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 221                 sprintf(buf, "%p", t);
 222                 if (strcmp(id, buf))
 223                         continue;
 224                 t->ret = -E_TASK_KILLED;
 225                 if (t->event_handler)
 226                         t->event_handler(t);
 227                 return 1;
 228         }
 229         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 230                 sprintf(buf, "%p", t);
 231                 if (strcmp(id, buf))
 232                         continue;
 233                 t->ret = -E_TASK_KILLED;
 234                 if (t->event_handler)
 235                         t->event_handler(t);
 236                 return 1;
 237         }
 238         return -E_NO_SUCH_TASK;
 239 }