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                 /*
  58                  * We have to check whether the list is empty because the call
  59                  * to ->pre_select() might have called sched_shutdown(). In
  60                  * this case t has been unregistered already, so we must not
  61                  * unregister it again.
  62                  */
  63                 if (list_empty(&pre_select_list))
  64                         return;
  65                 unregister_task(t);
  66         }
  67 }
  68
  69 static void sched_post_select(struct sched *s)
  70 {
  71         struct task *t, *tmp;
  72
  73         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
  74                 t->post_select(s, t);
  75 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
  76                 if (t->error >= 0)
  77                         continue;
  78                 /* nec., see sched_preselect() */
  79                 if (list_empty(&post_select_list))
  80                         return;
  81                 unregister_task(t);
  82         }
  83 }
  84
  85 /**
  86  * the core function for all paraslash programs
  87  *
  88  * \param s pointer to the scheduler struct
  89  *
  90  * This function updates the global \a now pointer, calls all registered
  91  * pre_select hooks which may set the timeout and add any file descriptors to
  92  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
  93  * to the registered tasks by calling their post_select hook.
  94  *
  95  * \return Zero if no more tasks are left in either of the two lists, negative
  96  * if para_select returned an error.
  97  *
  98  * \sa task, now.
  99  */
 100 int schedule(struct sched *s)
 101 {
 102         int ret;
 103
 104         if (!initialized)
 105                 return -E_NOT_INITIALIZED;
 106         gettimeofday(now, NULL);
 107 again:
 108         FD_ZERO(&s->rfds);
 109         FD_ZERO(&s->wfds);
 110         s->timeout = s->default_timeout;
 111         s->max_fileno = -1;
 112         sched_preselect(s);
 113         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 114                 return 0;
 115         ret = para_select(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
 116         if (ret < 0)
 117                 return ret;
 118         gettimeofday(now, NULL);
 119         sched_post_select(s);
 120         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 121                 return 0;
 122         goto again;
 123 }
 124
 125 /**
 126  * initialize the paraslash scheduler
 127  */
 128 static void init_sched(void)
 129 {
 130         PARA_INFO_LOG("initializing scheduler\n");
 131         INIT_LIST_HEAD(&pre_select_list);
 132         INIT_LIST_HEAD(&post_select_list);
 133         initialized = 1;
 134 };
 135
 136 /**
 137  * add a task to the scheduler
 138  *
 139  * \param t the task to add
 140  *
 141  * If the pre_select pointer of \a t is not \p NULL, it is added to
 142  * the pre_select list of the scheduler. Same goes for post_select.
 143  *
 144  * \sa task::pre_select, task::post_select
 145  */
 146 void register_task(struct task *t)
 147 {
 148         if (!initialized)
 149                 init_sched();
 150         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 151         if (t->pre_select) {
 152                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 153                 list_add_tail(&t->pre_select_node, &pre_select_list);
 154         }
 155         if (t->post_select) {
 156                 PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
 157                 list_add_tail(&t->post_select_node, &post_select_list);
 158         }
 159 }
 160
 161 /**
 162  * unregister all tasks
 163  *
 164  * This will cause \a schedule() to return immediately because both the
 165  * \a pre_select_list and the \a post_select_list are empty.
 166  */
 167 void sched_shutdown(void)
 168 {
 169         struct task *t, *tmp;
 170
 171         if (!initialized)
 172                 return;
 173         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
 174                 unregister_task(t);
 175         /* remove tasks which do not have a pre_select hook */
 176         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
 177                 unregister_task(t);
 178         initialized = 0;
 179 };
 180
 181 /**
 182  * get the list of all registered tasks.
 183  *
 184  * \return the task list
 185  *
 186  * Each entry of the list contains an identifier which is simply a hex number
 187  * that may be used in \a kill_task() to terminate the task.
 188  * The result ist dynamically allocated and must be freed by the caller.
 189  */
 190 char *get_task_list(void)
 191 {
 192         struct task *t, *tmp;
 193         char *msg = NULL;
 194
 195         if (!initialized)
 196                 return NULL;
 197         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 198                 char *tmp_msg;
 199                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 200                 free(msg);
 201                 msg = tmp_msg;
 202         }
 203         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 204                 char *tmp_msg;
 205 //              if (t->pre_select)
 206 //                      continue;
 207                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 208                 free(msg);
 209                 msg = tmp_msg;
 210         }
 211         //PARA_DEBUG_LOG("task list:\n%s", msg);
 212         return msg;
 213 }
 214
 215 /**
 216  * simulate an error for the given task
 217  *
 218  * \param id the task identifier
 219  *
 220  * Find the task identified by \a id, set the tasks' error value to
 221  * \p -E_TASK_KILLED and unregister the task.
 222  *
 223  * \return Positive on success, negative on errors (e.g. if \a id does not
 224  * correspond to a registered task).
 225  */
 226 int kill_task(char *id)
 227 {
 228         struct task *t, *tmp;
 229         char buf[20];
 230
 231         if (!initialized)
 232                 return -E_NOT_INITIALIZED;
 233         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 234                 sprintf(buf, "%p", t);
 235                 if (strcmp(id, buf))
 236                         continue;
 237                 t->error = -E_TASK_KILLED;
 238                 unregister_task(t);
 239                 return 1;
 240         }
 241         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 242                 sprintf(buf, "%p", t);
 243                 if (strcmp(id, buf))
 244                         continue;
 245                 t->error = -E_TASK_KILLED;
 246                 unregister_task(t);
 247                 return 1;
 248         }
 249         return -E_NO_SUCH_TASK;
 250 }