sched.c

   1 /*
   2  * Copyright (C) 2006-2008 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 /**
  28  * Remove a task from the scheduler.
  29  *
  30  * \param t the task to remove
  31  *
  32  * If the pre_select pointer of \a t is not \p NULL, it is removed from
  33  * the pre_select list of the scheduler. Same goes for \a post_select.
  34  */
  35 void unregister_task(struct task *t)
  36 {
  37         if (!initialized)
  38                 return;
  39         PARA_INFO_LOG("unregistering %s (%p)\n", t->status, t);
  40         if (t->pre_select)
  41                 list_del(&t->pre_select_node);
  42         if (t->post_select)
  43                 list_del(&t->post_select_node);
  44         if (t->error >= 0)
  45                 t->error = -E_TASK_KILLED;
  46 };
  47
  48
  49 static void sched_preselect(struct sched *s)
  50 {
  51         struct task *t, *tmp;
  52         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
  53                 t->pre_select(s, t);
  54 //              PARA_INFO_LOG("%s \n", t->status);
  55                 if (t->error >= 0)
  56                         continue;
  57                 unregister_task(t);
  58         }
  59 }
  60
  61 static void sched_post_select(struct sched *s)
  62 {
  63         struct task *t, *tmp;
  64
  65         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
  66                 t->post_select(s, t);
  67 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
  68                 if (t->error >= 0)
  69                         continue;
  70                 unregister_task(t);
  71         }
  72 }
  73
  74 /**
  75  * the core function for all paraslash programs
  76  *
  77  * \param s pointer to the scheduler struct
  78  *
  79  * This function updates the global \a now pointer, calls all registered
  80  * pre_select hooks which may set the timeout and add any file descriptors to
  81  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
  82  * to the registered tasks by calling their post_select hook.
  83  *
  84  * \return Zero if no more tasks are left in either of the two lists, negative
  85  * if para_select returned an error.
  86  *
  87  * \sa task, now.
  88  */
  89 int schedule(struct sched *s)
  90 {
  91         int ret;
  92
  93         if (!initialized)
  94                 return -E_NOT_INITIALIZED;
  95         gettimeofday(now, NULL);
  96 again:
  97         FD_ZERO(&s->rfds);
  98         FD_ZERO(&s->wfds);
  99         s->timeout = s->default_timeout;
 100         s->max_fileno = -1;
 101         sched_preselect(s);
 102         ret = para_select(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
 103         if (ret < 0)
 104                 return ret;
 105         gettimeofday(now, NULL);
 106         sched_post_select(s);
 107         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 108                 return 0;
 109         goto again;
 110 }
 111
 112 /**
 113  * initialize the paraslash scheduler
 114  */
 115 static void init_sched(void)
 116 {
 117         PARA_INFO_LOG("initializing scheduler\n");
 118         INIT_LIST_HEAD(&pre_select_list);
 119         INIT_LIST_HEAD(&post_select_list);
 120         initialized = 1;
 121 };
 122
 123 /**
 124  * add a task to the scheduler
 125  *
 126  * \param t the task to add
 127  *
 128  * If the pre_select pointer of \a t is not \p NULL, it is added to
 129  * the pre_select list of the scheduler. Same goes for post_select.
 130  *
 131  * \sa task::pre_select, task::post_select
 132  */
 133 void register_task(struct task *t)
 134 {
 135         if (!initialized)
 136                 init_sched();
 137         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 138         if (t->pre_select) {
 139                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 140                 list_add_tail(&t->pre_select_node, &pre_select_list);
 141         }
 142         if (t->post_select) {
 143                 PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
 144                 list_add_tail(&t->post_select_node, &post_select_list);
 145         }
 146 }
 147
 148 /**
 149  * unregister all tasks
 150  *
 151  * This will cause \a schedule() 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' error value to
 208  * \p -E_TASK_KILLED and unregister 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->error = -E_TASK_KILLED;
 225                 unregister_task(t);
 226                 return 1;
 227         }
 228         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 229                 sprintf(buf, "%p", t);
 230                 if (strcmp(id, buf))
 231                         continue;
 232                 t->error = -E_TASK_KILLED;
 233                 unregister_task(t);
 234                 return 1;
 235         }
 236         return -E_NO_SUCH_TASK;
 237 }