sched.c

   1 /*
   2  * Copyright (C) 2006-2009 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 <regex.h>
  10 #include <dirent.h> /* readdir() */
  11 #include <assert.h>
  12 #include <sys/time.h>
  13
  14 #include "para.h"
  15 #include "ipc.h"
  16 #include "fd.h"
  17 #include "list.h"
  18 #include "sched.h"
  19 #include "string.h"
  20 #include "error.h"
  21
  22 static struct list_head pre_select_list, post_select_list;
  23 static int initialized;
  24
  25 static struct timeval now_struct;
  26 struct timeval *now = &now_struct;
  27
  28 /**
  29  * Remove a task from the scheduler.
  30  *
  31  * \param t The task to remove.
  32  *
  33  * If the pre_select pointer of \a t is not \p NULL, it is removed from
  34  * the pre_select list of the scheduler. Same goes for \a post_select.
  35  */
  36 static void unregister_task(struct task *t)
  37 {
  38         if (!initialized)
  39                 return;
  40         PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
  41                 t->error <0? para_strerror(-t->error) : "shutdown");
  42         if (t->pre_select)
  43                 list_del(&t->pre_select_node);
  44         if (t->post_select)
  45                 list_del(&t->post_select_node);
  46         t->error = -E_TASK_UNREGISTERED;
  47 }
  48
  49
  50 static void sched_preselect(struct sched *s)
  51 {
  52         struct task *t, *tmp;
  53         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
  54                 if (t->error >= 0 && t->pre_select)
  55                         t->pre_select(s, t);
  56 //              PARA_INFO_LOG("%s \n", t->status);
  57                 if (t->error >= 0)
  58                         continue;
  59                 /*
  60                  * We have to check whether the list is empty because the call
  61                  * to ->pre_select() might have called sched_shutdown(). In
  62                  * this case t has been unregistered already, so we must not
  63                  * unregister it again.
  64                  */
  65                 if (list_empty(&pre_select_list))
  66                         return;
  67                 unregister_task(t);
  68         }
  69 }
  70
  71 static void sched_post_select(struct sched *s)
  72 {
  73         struct task *t, *tmp;
  74
  75         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
  76                 if (t->error >= 0)
  77                         t->post_select(s, t);
  78 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
  79                 if (t->error >= 0)
  80                         continue;
  81                 /* nec., see sched_preselect() */
  82                 if (list_empty(&post_select_list))
  83                         return;
  84                 unregister_task(t);
  85         }
  86 }
  87
  88 /**
  89  * The core function for all paraslash programs.
  90  *
  91  * \param s Pointer to the scheduler struct.
  92  *
  93  * This function updates the global \a now pointer, calls all registered
  94  * pre_select hooks which may set the timeout and add any file descriptors to
  95  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
  96  * to the registered tasks by calling their post_select hook.
  97  *
  98  * \return Zero if no more tasks are left in either of the two lists, negative
  99  * if para_select returned an error.
 100  *
 101  * \sa task, now.
 102  */
 103 int schedule(struct sched *s)
 104 {
 105         int ret;
 106
 107         if (!initialized)
 108                 return -E_NOT_INITIALIZED;
 109         if (!s->select_function)
 110                 s->select_function = para_select;
 111 again:
 112         FD_ZERO(&s->rfds);
 113         FD_ZERO(&s->wfds);
 114         s->timeout = s->default_timeout;
 115         s->max_fileno = -1;
 116         gettimeofday(now, NULL);
 117         sched_preselect(s);
 118         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 119                 return 0;
 120         ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout);
 121         if (ret < 0)
 122                 return ret;
 123         gettimeofday(now, NULL);
 124         sched_post_select(s);
 125         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 126                 return 0;
 127         goto again;
 128 }
 129
 130 /**
 131  * Initialize the paraslash scheduler.
 132  */
 133 static void init_sched(void)
 134 {
 135         PARA_INFO_LOG("initializing scheduler\n");
 136         INIT_LIST_HEAD(&pre_select_list);
 137         INIT_LIST_HEAD(&post_select_list);
 138         initialized = 1;
 139 }
 140
 141 /**
 142  * Add a task to the scheduler.
 143  *
 144  * \param t the task to add
 145  *
 146  * If the pre_select pointer of \a t is not \p NULL, it is added to
 147  * the pre_select list of the scheduler. Same goes for post_select.
 148  *
 149  * \sa task::pre_select, task::post_select
 150  */
 151 void register_task(struct task *t)
 152 {
 153         if (!initialized)
 154                 init_sched();
 155         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 156         if (t->pre_select) {
 157                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 158                 list_add_tail(&t->pre_select_node, &pre_select_list);
 159         }
 160         if (t->post_select) {
 161                 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
 162                 list_add_tail(&t->post_select_node, &post_select_list);
 163         }
 164 }
 165
 166 /**
 167  * Unregister all tasks.
 168  *
 169  * This will cause \a schedule() to return immediately because both the
 170  * \a pre_select_list and the \a post_select_list are empty.
 171  */
 172 void sched_shutdown(void)
 173 {
 174         struct task *t, *tmp;
 175
 176         if (!initialized)
 177                 return;
 178         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
 179                 unregister_task(t);
 180         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
 181                 unregister_task(t);
 182         initialized = 0;
 183 }
 184
 185 /**
 186  * Get the list of all registered tasks.
 187  *
 188  * \return The task list.
 189  *
 190  * Each entry of the list contains an identifier which is simply a hex number
 191  * that may be used in \a kill_task() to terminate the task.
 192  * The result ist dynamically allocated and must be freed by the caller.
 193  */
 194 char *get_task_list(void)
 195 {
 196         struct task *t, *tmp;
 197         char *msg = NULL;
 198
 199         if (!initialized)
 200                 return NULL;
 201         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 202                 char *tmp_msg;
 203                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 204                 free(msg);
 205                 msg = tmp_msg;
 206         }
 207         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 208                 char *tmp_msg;
 209 //              if (t->pre_select)
 210 //                      continue;
 211                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 212                 free(msg);
 213                 msg = tmp_msg;
 214         }
 215         //PARA_DEBUG_LOG("task list:\n%s", msg);
 216         return msg;
 217 }
 218
 219 /**
 220  * Simulate an error for the given task.
 221  *
 222  * \param id The task identifier.
 223  *
 224  * Find the task identified by \a id, set the tasks' error value to
 225  * \p -E_TASK_KILLED and unregister the task.
 226  *
 227  * \return Positive on success, negative on errors (e.g. if \a id does not
 228  * correspond to a registered task).
 229  */
 230 int kill_task(char *id)
 231 {
 232         struct task *t, *tmp;
 233         char buf[20];
 234
 235         if (!initialized)
 236                 return -E_NOT_INITIALIZED;
 237         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 238                 sprintf(buf, "%p", t);
 239                 if (strcmp(id, buf))
 240                         continue;
 241                 t->error = -E_TASK_KILLED;
 242                 return 1;
 243         }
 244         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 245                 sprintf(buf, "%p", t);
 246                 if (strcmp(id, buf))
 247                         continue;
 248                 t->error = -E_TASK_KILLED;
 249                 return 1;
 250         }
 251         return -E_NO_SUCH_TASK;
 252 }