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 static void unregister_task(struct task *t)
  36 {
  37         if (!initialized)
  38                 return;
  39         PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
  40                 t->error <0? para_strerror(-t->error) : "shutdown");
  41         if (t->pre_select)
  42                 list_del(&t->pre_select_node);
  43         if (t->post_select)
  44                 list_del(&t->post_select_node);
  45         t->error = -E_TASK_UNREGISTERED;
  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                 if (t->error >= 0)
  54                         t->pre_select(s, t);
  55 //              PARA_INFO_LOG("%s \n", t->status);
  56                 if (t->error >= 0)
  57                         continue;
  58                 /*
  59                  * We have to check whether the list is empty because the call
  60                  * to ->pre_select() might have called sched_shutdown(). In
  61                  * this case t has been unregistered already, so we must not
  62                  * unregister it again.
  63                  */
  64                 if (list_empty(&pre_select_list))
  65                         return;
  66                 unregister_task(t);
  67         }
  68 }
  69
  70 static void sched_post_select(struct sched *s)
  71 {
  72         struct task *t, *tmp;
  73
  74         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
  75                 if (t->error >= 0)
  76                         t->post_select(s, t);
  77 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
  78                 if (t->error >= 0)
  79                         continue;
  80                 /* nec., see sched_preselect() */
  81                 if (list_empty(&post_select_list))
  82                         return;
  83                 unregister_task(t);
  84         }
  85 }
  86
  87 /**
  88  * The core function for all paraslash programs.
  89  *
  90  * \param s Pointer to the scheduler struct.
  91  *
  92  * This function updates the global \a now pointer, calls all registered
  93  * pre_select hooks which may set the timeout and add any file descriptors to
  94  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
  95  * to the registered tasks by calling their post_select hook.
  96  *
  97  * \return Zero if no more tasks are left in either of the two lists, negative
  98  * if para_select returned an error.
  99  *
 100  * \sa task, now.
 101  */
 102 int schedule(struct sched *s)
 103 {
 104         int ret;
 105
 106         if (!initialized)
 107                 return -E_NOT_INITIALIZED;
 108         if (!s->select_function)
 109                 s->select_function = para_select;
 110         gettimeofday(now, NULL);
 111 again:
 112         FD_ZERO(&s->rfds);
 113         FD_ZERO(&s->wfds);
 114         s->timeout = s->default_timeout;
 115         s->max_fileno = -1;
 116         sched_preselect(s);
 117         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 118                 return 0;
 119         ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
 120         if (ret < 0)
 121                 return ret;
 122         gettimeofday(now, NULL);
 123         sched_post_select(s);
 124         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 125                 return 0;
 126         goto again;
 127 }
 128
 129 /**
 130  * Initialize the paraslash scheduler.
 131  */
 132 static void init_sched(void)
 133 {
 134         PARA_INFO_LOG("initializing scheduler\n");
 135         INIT_LIST_HEAD(&pre_select_list);
 136         INIT_LIST_HEAD(&post_select_list);
 137         initialized = 1;
 138 };
 139
 140 /**
 141  * Add a task to the scheduler.
 142  *
 143  * \param t the task to add
 144  *
 145  * If the pre_select pointer of \a t is not \p NULL, it is added to
 146  * the pre_select list of the scheduler. Same goes for post_select.
 147  *
 148  * \sa task::pre_select, task::post_select
 149  */
 150 void register_task(struct task *t)
 151 {
 152         if (!initialized)
 153                 init_sched();
 154         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 155         if (t->pre_select) {
 156                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 157                 list_add_tail(&t->pre_select_node, &pre_select_list);
 158         }
 159         if (t->post_select) {
 160                 PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
 161                 list_add_tail(&t->post_select_node, &post_select_list);
 162         }
 163 }
 164
 165 /**
 166  * Unregister all tasks.
 167  *
 168  * This will cause \a schedule() to return immediately because both the
 169  * \a pre_select_list and the \a post_select_list are empty.
 170  */
 171 void sched_shutdown(void)
 172 {
 173         struct task *t, *tmp;
 174
 175         if (!initialized)
 176                 return;
 177         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
 178                 unregister_task(t);
 179         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
 180                 unregister_task(t);
 181         initialized = 0;
 182 };
 183
 184 /**
 185  * Get the list of all registered tasks.
 186  *
 187  * \return The task list.
 188  *
 189  * Each entry of the list contains an identifier which is simply a hex number
 190  * that may be used in \a kill_task() to terminate the task.
 191  * The result ist dynamically allocated and must be freed by the caller.
 192  */
 193 char *get_task_list(void)
 194 {
 195         struct task *t, *tmp;
 196         char *msg = NULL;
 197
 198         if (!initialized)
 199                 return NULL;
 200         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 201                 char *tmp_msg;
 202                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 203                 free(msg);
 204                 msg = tmp_msg;
 205         }
 206         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 207                 char *tmp_msg;
 208 //              if (t->pre_select)
 209 //                      continue;
 210                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 211                 free(msg);
 212                 msg = tmp_msg;
 213         }
 214         //PARA_DEBUG_LOG("task list:\n%s", msg);
 215         return msg;
 216 }
 217
 218 /**
 219  * Simulate an error for the given task.
 220  *
 221  * \param id The task identifier.
 222  *
 223  * Find the task identified by \a id, set the tasks' error value to
 224  * \p -E_TASK_KILLED and unregister the task.
 225  *
 226  * \return Positive on success, negative on errors (e.g. if \a id does not
 227  * correspond to a registered task).
 228  */
 229 int kill_task(char *id)
 230 {
 231         struct task *t, *tmp;
 232         char buf[20];
 233
 234         if (!initialized)
 235                 return -E_NOT_INITIALIZED;
 236         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 237                 sprintf(buf, "%p", t);
 238                 if (strcmp(id, buf))
 239                         continue;
 240                 t->error = -E_TASK_KILLED;
 241                 return 1;
 242         }
 243         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 244                 sprintf(buf, "%p", t);
 245                 if (strcmp(id, buf))
 246                         continue;
 247                 t->error = -E_TASK_KILLED;
 248                 return 1;
 249         }
 250         return -E_NO_SUCH_TASK;
 251 }