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         t->error = -E_TASK_UNREGISTERED;
  45 };
  46
  47
  48 static void sched_preselect(struct sched *s)
  49 {
  50         struct task *t, *tmp;
  51         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
  52                 if (t->error >= 0)
  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                 if (t->error >= 0)
  75                         t->post_select(s, t);
  76 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
  77                 if (t->error >= 0)
  78                         continue;
  79                 /* nec., see sched_preselect() */
  80                 if (list_empty(&post_select_list))
  81                         return;
  82                 unregister_task(t);
  83         }
  84 }
  85
  86 /**
  87  * The core function for all paraslash programs.
  88  *
  89  * \param s Pointer to the scheduler struct.
  90  *
  91  * This function updates the global \a now pointer, calls all registered
  92  * pre_select hooks which may set the timeout and add any file descriptors to
  93  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
  94  * to the registered tasks by calling their post_select hook.
  95  *
  96  * \return Zero if no more tasks are left in either of the two lists, negative
  97  * if para_select returned an error.
  98  *
  99  * \sa task, now.
 100  */
 101 int schedule(struct sched *s)
 102 {
 103         int ret;
 104
 105         if (!initialized)
 106                 return -E_NOT_INITIALIZED;
 107         gettimeofday(now, NULL);
 108 again:
 109         FD_ZERO(&s->rfds);
 110         FD_ZERO(&s->wfds);
 111         s->timeout = s->default_timeout;
 112         s->max_fileno = -1;
 113         sched_preselect(s);
 114         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 115                 return 0;
 116         ret = para_select(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
 117         if (ret < 0)
 118                 return ret;
 119         gettimeofday(now, NULL);
 120         sched_post_select(s);
 121         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 122                 return 0;
 123         goto again;
 124 }
 125
 126 /**
 127  * Initialize the paraslash scheduler.
 128  */
 129 static void init_sched(void)
 130 {
 131         PARA_INFO_LOG("initializing scheduler\n");
 132         INIT_LIST_HEAD(&pre_select_list);
 133         INIT_LIST_HEAD(&post_select_list);
 134         initialized = 1;
 135 };
 136
 137 /**
 138  * Add a task to the scheduler.
 139  *
 140  * \param t the task to add
 141  *
 142  * If the pre_select pointer of \a t is not \p NULL, it is added to
 143  * the pre_select list of the scheduler. Same goes for post_select.
 144  *
 145  * \sa task::pre_select, task::post_select
 146  */
 147 void register_task(struct task *t)
 148 {
 149         if (!initialized)
 150                 init_sched();
 151         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 152         if (t->pre_select) {
 153                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 154                 list_add_tail(&t->pre_select_node, &pre_select_list);
 155         }
 156         if (t->post_select) {
 157                 PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
 158                 list_add_tail(&t->post_select_node, &post_select_list);
 159         }
 160 }
 161
 162 /**
 163  * Unregister all tasks.
 164  *
 165  * This will cause \a schedule() to return immediately because both the
 166  * \a pre_select_list and the \a post_select_list are empty.
 167  */
 168 void sched_shutdown(void)
 169 {
 170         struct task *t, *tmp;
 171
 172         if (!initialized)
 173                 return;
 174         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
 175                 unregister_task(t);
 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                 return 1;
 239         }
 240         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 241                 sprintf(buf, "%p", t);
 242                 if (strcmp(id, buf))
 243                         continue;
 244                 t->error = -E_TASK_KILLED;
 245                 return 1;
 246         }
 247         return -E_NO_SUCH_TASK;
 248 }