sched.c

   1 /*
   2  * Copyright (C) 2006-2010 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         if (ret == 0) {
 124                 /*
 125                  * APUE: Be careful not to check the descriptor sets on return
 126                  * unless the return value is greater than zero. The return
 127                  * state of the descriptor sets is implementation dependent if
 128                  * either a signal is caught or the timer expires.
 129                  */
 130                 FD_ZERO(&s->rfds);
 131                 FD_ZERO(&s->wfds);
 132         }
 133         gettimeofday(now, NULL);
 134         sched_post_select(s);
 135         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 136                 return 0;
 137         goto again;
 138 }
 139
 140 /*
 141  * Initialize the paraslash scheduler.
 142  */
 143 static void init_sched(void)
 144 {
 145         PARA_INFO_LOG("initializing scheduler\n");
 146         INIT_LIST_HEAD(&pre_select_list);
 147         INIT_LIST_HEAD(&post_select_list);
 148         initialized = 1;
 149 }
 150
 151 /**
 152  * Add a task to the scheduler.
 153  *
 154  * \param t the task to add
 155  *
 156  * If the pre_select pointer of \a t is not \p NULL, it is added to
 157  * the pre_select list of the scheduler. Same goes for post_select.
 158  *
 159  * \sa task::pre_select, task::post_select
 160  */
 161 void register_task(struct task *t)
 162 {
 163         if (!initialized)
 164                 init_sched();
 165         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 166         if (t->pre_select) {
 167                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 168                 list_add_tail(&t->pre_select_node, &pre_select_list);
 169         }
 170         if (t->post_select) {
 171                 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
 172                 list_add_tail(&t->post_select_node, &post_select_list);
 173         }
 174 }
 175
 176 /**
 177  * Unregister all tasks.
 178  *
 179  * This will cause \a schedule() to return immediately because both the
 180  * \a pre_select_list and the \a post_select_list are empty.
 181  */
 182 void sched_shutdown(void)
 183 {
 184         struct task *t, *tmp;
 185
 186         if (!initialized)
 187                 return;
 188         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
 189                 unregister_task(t);
 190         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
 191                 unregister_task(t);
 192         initialized = 0;
 193 }
 194
 195 /**
 196  * Get the list of all registered tasks.
 197  *
 198  * \return The task list.
 199  *
 200  * Each entry of the list contains an identifier which is simply a hex number
 201  * that may be used in \a kill_task() to terminate the task.
 202  * The result is dynamically allocated and must be freed by the caller.
 203  */
 204 char *get_task_list(void)
 205 {
 206         struct task *t, *tmp;
 207         char *msg = NULL;
 208
 209         if (!initialized)
 210                 return NULL;
 211         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 212                 char *tmp_msg;
 213                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 214                 free(msg);
 215                 msg = tmp_msg;
 216         }
 217         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 218                 char *tmp_msg;
 219 //              if (t->pre_select)
 220 //                      continue;
 221                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 222                 free(msg);
 223                 msg = tmp_msg;
 224         }
 225         //PARA_DEBUG_LOG("task list:\n%s", msg);
 226         return msg;
 227 }
 228
 229 /**
 230  * Simulate an error for the given task.
 231  *
 232  * \param id The task identifier.
 233  *
 234  * Find the task identified by \a id, set the tasks' error value to
 235  * \p -E_TASK_KILLED and unregister the task.
 236  *
 237  * \return Positive on success, negative on errors (e.g. if \a id does not
 238  * correspond to a registered task).
 239  */
 240 int kill_task(char *id)
 241 {
 242         struct task *t, *tmp;
 243         char buf[20];
 244
 245         if (!initialized)
 246                 return -E_NOT_INITIALIZED;
 247         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 248                 sprintf(buf, "%p", t);
 249                 if (strcmp(id, buf))
 250                         continue;
 251                 t->error = -E_TASK_KILLED;
 252                 return 1;
 253         }
 254         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 255                 sprintf(buf, "%p", t);
 256                 if (strcmp(id, buf))
 257                         continue;
 258                 t->error = -E_TASK_KILLED;
 259                 return 1;
 260         }
 261         return -E_NO_SUCH_TASK;
 262 }
 263
 264 /**
 265  * Set the select timeout to the minimal possible value.
 266  *
 267  * \param s Pointer to the scheduler struct.
 268  *
 269  * This causes the next select() call to return immediately.
 270  */
 271 void sched_min_delay(struct sched *s)
 272 {
 273         s->timeout.tv_sec = 0;
 274         s->timeout.tv_usec = 1;
 275 }
 276
 277 /**
 278  * Impose an upper bound for the timeout of the next select() call.
 279  *
 280  * \param timeout Maximal allowed timeout.
 281  * \param s Pointer to the scheduler struct.
 282  *
 283  * If the current scheduler timeout is already smaller than \a timeout, this
 284  * function does nothing. Otherwise the timeout for the next select() call is
 285  * set to the given value.
 286  *
 287  * \sa sched_request_timeout_ms().
 288  */
 289 void sched_request_timeout(struct timeval *timeout, struct sched *s)
 290 {
 291         if (tv_diff(&s->timeout, timeout, NULL) > 0)
 292                 s->timeout = *timeout;
 293 }
 294
 295 /**
 296  * Force the next select() call to return before the given amount of milliseconds.
 297  *
 298  * \param ms The maximal allowed timeout in milliseconds.
 299  * \param s Pointer to the scheduler struct.
 300  *
 301  * Like sched_request_timeout() this imposes an upper bound on the timeout
 302  * value for the next select() call.
 303  */
 304 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
 305 {
 306         struct timeval tv;
 307         ms2tv(ms, &tv);
 308         sched_request_timeout(&tv, s);
 309 }
 310
 311 /**
 312  * Force the next select() call to return before the given future time.
 313  *
 314  * \param barrier Absolute time before select() should return.
 315  * \param s Pointer to the scheduler struct.
 316  *
 317  * If \a barrier is in the past, this function does nothing.
 318  *
 319  * \sa sched_request_barrier_or_min_delay().
 320  */
 321 void sched_request_barrier(struct timeval *barrier, struct sched *s)
 322 {
 323         struct timeval diff;
 324
 325         if (tv_diff(now, barrier, &diff) > 0)
 326                 return;
 327         sched_request_timeout(&diff, s);
 328 }
 329
 330 /**
 331  * Force the next select() call to return before the given time.
 332  *
 333  * \param barrier Absolute time before select() should return.
 334  * \param s Pointer to the scheduler struct.
 335  *
 336  * If \a barrier is in the past, this function requests a minimal timeout.
 337  *
 338  * \sa sched_min_delay(), sched_request_barrier().
 339  */
 340 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
 341 {
 342         struct timeval diff;
 343
 344         if (tv_diff(now, barrier, &diff) > 0)
 345                 return sched_min_delay(s);
 346         sched_request_timeout(&diff, s);
 347 }