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 "time.h"
  21 #include "error.h"
  22
  23 static struct list_head pre_select_list, post_select_list;
  24 static int initialized;
  25
  26 static struct timeval now_struct;
  27 struct timeval *now = &now_struct;
  28
  29 /*
  30  * Remove a task from the scheduler.
  31  *
  32  * \param t The task to remove.
  33  *
  34  * If the pre_select pointer of \a t is not \p NULL, it is removed from
  35  * the pre_select list of the scheduler. Same goes for \a post_select.
  36  */
  37 static void unregister_task(struct task *t)
  38 {
  39         if (!initialized)
  40                 return;
  41         PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
  42                 t->error <0? para_strerror(-t->error) : "shutdown");
  43         if (t->pre_select)
  44                 list_del(&t->pre_select_node);
  45         if (t->post_select)
  46                 list_del(&t->post_select_node);
  47         t->error = -E_TASK_UNREGISTERED;
  48 }
  49
  50
  51 static void sched_preselect(struct sched *s)
  52 {
  53         struct task *t, *tmp;
  54         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
  55                 if (t->error >= 0 && t->pre_select)
  56                         t->pre_select(s, t);
  57 //              PARA_INFO_LOG("%s \n", t->status);
  58                 if (t->error >= 0)
  59                         continue;
  60                 /*
  61                  * We have to check whether the list is empty because the call
  62                  * to ->pre_select() might have called sched_shutdown(). In
  63                  * this case t has been unregistered already, so we must not
  64                  * unregister it again.
  65                  */
  66                 if (list_empty(&pre_select_list))
  67                         return;
  68                 unregister_task(t);
  69         }
  70 }
  71
  72 //#define SCHED_DEBUG 1
  73 static inline void call_post_select(struct sched *s, struct task *t)
  74 {
  75 #ifndef SCHED_DEBUG
  76         t->post_select(s, t);
  77 #else
  78         struct timeval t1, t2, diff;
  79         unsigned long pst;
  80
  81         gettimeofday(&t1, NULL);
  82         t->post_select(s, t);
  83         gettimeofday(&t2, NULL);
  84         tv_diff(&t1, &t2, &diff);
  85         pst = tv2ms(&diff);
  86         if (pst > 50)
  87                 PARA_WARNING_LOG("%s: post_select time: %lums\n",
  88                         t->status, pst);
  89 #endif
  90 }
  91
  92 static void sched_post_select(struct sched *s)
  93 {
  94         struct task *t, *tmp;
  95
  96         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
  97                 if (t->error >= 0)
  98                         call_post_select(s, t);
  99 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
 100                 if (t->error >= 0)
 101                         continue;
 102                 /* nec., see sched_preselect() */
 103                 if (list_empty(&post_select_list))
 104                         return;
 105                 unregister_task(t);
 106         }
 107 }
 108
 109 /**
 110  * The core function for all paraslash programs.
 111  *
 112  * \param s Pointer to the scheduler struct.
 113  *
 114  * This function updates the global \a now pointer, calls all registered
 115  * pre_select hooks which may set the timeout and add any file descriptors to
 116  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
 117  * to the registered tasks by calling their post_select hook.
 118  *
 119  * \return Zero if no more tasks are left in either of the two lists, negative
 120  * if para_select returned an error.
 121  *
 122  * \sa task, now.
 123  */
 124 int schedule(struct sched *s)
 125 {
 126         int ret;
 127
 128         if (!initialized)
 129                 return -E_NOT_INITIALIZED;
 130         if (!s->select_function)
 131                 s->select_function = para_select;
 132 again:
 133         FD_ZERO(&s->rfds);
 134         FD_ZERO(&s->wfds);
 135         s->select_timeout = s->default_timeout;
 136         s->max_fileno = -1;
 137         gettimeofday(now, NULL);
 138         sched_preselect(s);
 139         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 140                 return 0;
 141         ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
 142                 &s->select_timeout);
 143         if (ret < 0)
 144                 return ret;
 145         if (ret == 0) {
 146                 /*
 147                  * APUE: Be careful not to check the descriptor sets on return
 148                  * unless the return value is greater than zero. The return
 149                  * state of the descriptor sets is implementation dependent if
 150                  * either a signal is caught or the timer expires.
 151                  */
 152                 FD_ZERO(&s->rfds);
 153                 FD_ZERO(&s->wfds);
 154         }
 155         gettimeofday(now, NULL);
 156         sched_post_select(s);
 157         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 158                 return 0;
 159         goto again;
 160 }
 161
 162 /*
 163  * Initialize the paraslash scheduler.
 164  */
 165 static void init_sched(void)
 166 {
 167         PARA_INFO_LOG("initializing scheduler\n");
 168         INIT_LIST_HEAD(&pre_select_list);
 169         INIT_LIST_HEAD(&post_select_list);
 170         initialized = 1;
 171 }
 172
 173 /**
 174  * Add a task to the scheduler.
 175  *
 176  * \param t the task to add
 177  *
 178  * If the pre_select pointer of \a t is not \p NULL, it is added to
 179  * the pre_select list of the scheduler. Same goes for post_select.
 180  *
 181  * \sa task::pre_select, task::post_select
 182  */
 183 void register_task(struct task *t)
 184 {
 185         if (!initialized)
 186                 init_sched();
 187         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 188         if (t->pre_select) {
 189                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 190                 list_add_tail(&t->pre_select_node, &pre_select_list);
 191         }
 192         if (t->post_select) {
 193                 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
 194                 list_add_tail(&t->post_select_node, &post_select_list);
 195         }
 196 }
 197
 198 /**
 199  * Unregister all tasks.
 200  *
 201  * This will cause \a schedule() to return immediately because both the
 202  * \a pre_select_list and the \a post_select_list are empty.
 203  */
 204 void sched_shutdown(void)
 205 {
 206         struct task *t, *tmp;
 207
 208         if (!initialized)
 209                 return;
 210         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node)
 211                 unregister_task(t);
 212         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
 213                 unregister_task(t);
 214         initialized = 0;
 215 }
 216
 217 /**
 218  * Get the list of all registered tasks.
 219  *
 220  * \return The task list.
 221  *
 222  * Each entry of the list contains an identifier which is simply a hex number
 223  * that may be used in \a kill_task() to terminate the task.
 224  * The result is dynamically allocated and must be freed by the caller.
 225  */
 226 char *get_task_list(void)
 227 {
 228         struct task *t, *tmp;
 229         char *msg = NULL;
 230
 231         if (!initialized)
 232                 return NULL;
 233         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 234                 char *tmp_msg;
 235                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 236                 free(msg);
 237                 msg = tmp_msg;
 238         }
 239         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 240                 char *tmp_msg;
 241 //              if (t->pre_select)
 242 //                      continue;
 243                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 244                 free(msg);
 245                 msg = tmp_msg;
 246         }
 247         //PARA_DEBUG_LOG("task list:\n%s", msg);
 248         return msg;
 249 }
 250
 251 /**
 252  * Simulate an error for the given task.
 253  *
 254  * \param id The task identifier.
 255  *
 256  * Find the task identified by \a id, set the tasks' error value to
 257  * \p -E_TASK_KILLED and unregister the task.
 258  *
 259  * \return Positive on success, negative on errors (e.g. if \a id does not
 260  * correspond to a registered task).
 261  */
 262 int kill_task(char *id)
 263 {
 264         struct task *t, *tmp;
 265         char buf[20];
 266
 267         if (!initialized)
 268                 return -E_NOT_INITIALIZED;
 269         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 270                 sprintf(buf, "%p", t);
 271                 if (strcmp(id, buf))
 272                         continue;
 273                 t->error = -E_TASK_KILLED;
 274                 return 1;
 275         }
 276         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 277                 sprintf(buf, "%p", t);
 278                 if (strcmp(id, buf))
 279                         continue;
 280                 t->error = -E_TASK_KILLED;
 281                 return 1;
 282         }
 283         return -E_NO_SUCH_TASK;
 284 }
 285
 286 /**
 287  * Set the select timeout to the minimal possible value.
 288  *
 289  * \param s Pointer to the scheduler struct.
 290  *
 291  * This causes the next select() call to return immediately.
 292  */
 293 void sched_min_delay(struct sched *s)
 294 {
 295         s->select_timeout.tv_sec = 0;
 296         s->select_timeout.tv_usec = 1;
 297 }
 298
 299 /**
 300  * Impose an upper bound for the timeout of the next select() call.
 301  *
 302  * \param to Maximal allowed timeout.
 303  * \param s Pointer to the scheduler struct.
 304  *
 305  * If the current scheduler timeout is already smaller than \a to, this
 306  * function does nothing. Otherwise the timeout for the next select() call is
 307  * set to the given value.
 308  *
 309  * \sa sched_request_timeout_ms().
 310  */
 311 void sched_request_timeout(struct timeval *to, struct sched *s)
 312 {
 313         if (tv_diff(&s->select_timeout, to, NULL) > 0)
 314                 s->select_timeout = *to;
 315 }
 316
 317 /**
 318  * Force the next select() call to return before the given amount of milliseconds.
 319  *
 320  * \param ms The maximal allowed timeout in milliseconds.
 321  * \param s Pointer to the scheduler struct.
 322  *
 323  * Like sched_request_timeout() this imposes an upper bound on the timeout
 324  * value for the next select() call.
 325  */
 326 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
 327 {
 328         struct timeval tv;
 329         ms2tv(ms, &tv);
 330         sched_request_timeout(&tv, s);
 331 }
 332
 333 /**
 334  * Force the next select() call to return before the given future time.
 335  *
 336  * \param barrier Absolute time before select() should return.
 337  * \param s Pointer to the scheduler struct.
 338  *
 339  * If \a barrier is in the past, this function does nothing.
 340  *
 341  * \sa sched_request_barrier_or_min_delay().
 342  */
 343 void sched_request_barrier(struct timeval *barrier, struct sched *s)
 344 {
 345         struct timeval diff;
 346
 347         if (tv_diff(now, barrier, &diff) > 0)
 348                 return;
 349         sched_request_timeout(&diff, s);
 350 }
 351
 352 /**
 353  * Force the next select() call to return before the given time.
 354  *
 355  * \param barrier Absolute time before select() should return.
 356  * \param s Pointer to the scheduler struct.
 357  *
 358  * If \a barrier is in the past, this function requests a minimal timeout.
 359  *
 360  * \sa sched_min_delay(), sched_request_barrier().
 361  */
 362 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
 363 {
 364         struct timeval diff;
 365
 366         if (tv_diff(now, barrier, &diff) > 0)
 367                 return sched_min_delay(s);
 368         sched_request_timeout(&diff, s);
 369 }