sched.c

   1 /*
   2  * Copyright (C) 2006-2011 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         assert(t->error < 0);
  42         PARA_INFO_LOG("unregistering %s (%s)\n", t->status,
  43                 para_strerror(-t->error));
  44         if (t->pre_select)
  45                 list_del(&t->pre_select_node);
  46         if (t->post_select)
  47                 list_del(&t->post_select_node);
  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->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 //#define SCHED_DEBUG 1
  72 static inline void call_post_select(struct sched *s, struct task *t)
  73 {
  74 #ifndef SCHED_DEBUG
  75         t->post_select(s, t);
  76 #else
  77         struct timeval t1, t2, diff;
  78         unsigned long pst;
  79
  80         gettimeofday(&t1, NULL);
  81         t->post_select(s, t);
  82         gettimeofday(&t2, NULL);
  83         tv_diff(&t1, &t2, &diff);
  84         pst = tv2ms(&diff);
  85         if (pst > 50)
  86                 PARA_WARNING_LOG("%s: post_select time: %lums\n",
  87                         t->status, pst);
  88 #endif
  89 }
  90
  91 static void sched_post_select(struct sched *s)
  92 {
  93         struct task *t, *tmp;
  94
  95         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
  96                 if (t->error >= 0)
  97                         call_post_select(s, t);
  98 //              PARA_INFO_LOG("%s: %d\n", t->status, t->ret);
  99                 if (t->error >= 0)
 100                         continue;
 101                 /* nec., see sched_preselect() */
 102                 if (list_empty(&post_select_list))
 103                         return;
 104                 unregister_task(t);
 105         }
 106 }
 107
 108 /**
 109  * The core function for all paraslash programs.
 110  *
 111  * \param s Pointer to the scheduler struct.
 112  *
 113  * This function updates the global \a now pointer, calls all registered
 114  * pre_select hooks which may set the timeout and add any file descriptors to
 115  * the fd sets of \a s.  Next, it calls para_select() and makes the result available
 116  * to the registered tasks by calling their post_select hook.
 117  *
 118  * \return Zero if no more tasks are left in either of the two lists, negative
 119  * if para_select returned an error.
 120  *
 121  * \sa task, now.
 122  */
 123 int schedule(struct sched *s)
 124 {
 125         int ret;
 126
 127         if (!initialized)
 128                 return -E_NOT_INITIALIZED;
 129         if (!s->select_function)
 130                 s->select_function = para_select;
 131 again:
 132         FD_ZERO(&s->rfds);
 133         FD_ZERO(&s->wfds);
 134         s->select_timeout = s->default_timeout;
 135         s->max_fileno = -1;
 136         gettimeofday(now, NULL);
 137         sched_preselect(s);
 138         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 139                 return 0;
 140         ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds,
 141                 &s->select_timeout);
 142         if (ret < 0)
 143                 return ret;
 144         if (ret == 0) {
 145                 /*
 146                  * APUE: Be careful not to check the descriptor sets on return
 147                  * unless the return value is greater than zero. The return
 148                  * state of the descriptor sets is implementation dependent if
 149                  * either a signal is caught or the timer expires.
 150                  */
 151                 FD_ZERO(&s->rfds);
 152                 FD_ZERO(&s->wfds);
 153         }
 154         gettimeofday(now, NULL);
 155         sched_post_select(s);
 156         if (list_empty(&pre_select_list) && list_empty(&post_select_list))
 157                 return 0;
 158         goto again;
 159 }
 160
 161 /*
 162  * Initialize the paraslash scheduler.
 163  */
 164 static void init_sched(void)
 165 {
 166         PARA_INFO_LOG("initializing scheduler\n");
 167         INIT_LIST_HEAD(&pre_select_list);
 168         INIT_LIST_HEAD(&post_select_list);
 169         initialized = 1;
 170 }
 171
 172 /**
 173  * Add a task to the scheduler.
 174  *
 175  * \param t the task to add
 176  *
 177  * If the pre_select pointer of \a t is not \p NULL, it is added to
 178  * the pre_select list of the scheduler. Same goes for post_select.
 179  *
 180  * \sa task::pre_select, task::post_select
 181  */
 182 void register_task(struct task *t)
 183 {
 184         if (!initialized)
 185                 init_sched();
 186         PARA_INFO_LOG("registering %s (%p)\n", t->status, t);
 187         if (t->pre_select) {
 188                 PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select);
 189                 list_add_tail(&t->pre_select_node, &pre_select_list);
 190         }
 191         if (t->post_select) {
 192                 PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
 193                 list_add_tail(&t->post_select_node, &post_select_list);
 194         }
 195 }
 196
 197 /**
 198  * Unregister all tasks.
 199  *
 200  * This will cause \a schedule() to return immediately because both the
 201  * \a pre_select_list and the \a post_select_list are empty.
 202  */
 203 void sched_shutdown(void)
 204 {
 205         struct task *t, *tmp;
 206
 207         if (!initialized)
 208                 return;
 209         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 210                 t->error = -E_SCHED_SHUTDOWN;
 211                 unregister_task(t);
 212         }
 213         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 214                 t->error = -E_SCHED_SHUTDOWN;
 215                 unregister_task(t);
 216         }
 217         initialized = 0;
 218 }
 219
 220 /**
 221  * Get the list of all registered tasks.
 222  *
 223  * \return The task list.
 224  *
 225  * Each entry of the list contains an identifier which is simply a hex number.
 226  * The result is dynamically allocated and must be freed by the caller.
 227  */
 228 char *get_task_list(void)
 229 {
 230         struct task *t, *tmp;
 231         char *msg = NULL;
 232
 233         if (!initialized)
 234                 return NULL;
 235         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 236                 char *tmp_msg;
 237                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 238                 free(msg);
 239                 msg = tmp_msg;
 240         }
 241         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 242                 char *tmp_msg;
 243 //              if (t->pre_select)
 244 //                      continue;
 245                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 246                 free(msg);
 247                 msg = tmp_msg;
 248         }
 249         //PARA_DEBUG_LOG("task list:\n%s", msg);
 250         return msg;
 251 }
 252
 253 /**
 254  * Set the select timeout to the minimal possible value.
 255  *
 256  * \param s Pointer to the scheduler struct.
 257  *
 258  * This causes the next select() call to return immediately.
 259  */
 260 void sched_min_delay(struct sched *s)
 261 {
 262         s->select_timeout.tv_sec = 0;
 263         s->select_timeout.tv_usec = 1;
 264 }
 265
 266 /**
 267  * Impose an upper bound for the timeout of the next select() call.
 268  *
 269  * \param to Maximal allowed timeout.
 270  * \param s Pointer to the scheduler struct.
 271  *
 272  * If the current scheduler timeout is already smaller than \a to, this
 273  * function does nothing. Otherwise the timeout for the next select() call is
 274  * set to the given value.
 275  *
 276  * \sa sched_request_timeout_ms().
 277  */
 278 void sched_request_timeout(struct timeval *to, struct sched *s)
 279 {
 280         if (tv_diff(&s->select_timeout, to, NULL) > 0)
 281                 s->select_timeout = *to;
 282 }
 283
 284 /**
 285  * Force the next select() call to return before the given amount of milliseconds.
 286  *
 287  * \param ms The maximal allowed timeout in milliseconds.
 288  * \param s Pointer to the scheduler struct.
 289  *
 290  * Like sched_request_timeout() this imposes an upper bound on the timeout
 291  * value for the next select() call.
 292  */
 293 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
 294 {
 295         struct timeval tv;
 296         ms2tv(ms, &tv);
 297         sched_request_timeout(&tv, s);
 298 }
 299
 300 /**
 301  * Force the next select() call to return before the given future time.
 302  *
 303  * \param barrier Absolute time before select() should return.
 304  * \param s Pointer to the scheduler struct.
 305  *
 306  * If \a barrier is in the past, this function does nothing.
 307  *
 308  * \sa sched_request_barrier_or_min_delay().
 309  */
 310 void sched_request_barrier(struct timeval *barrier, struct sched *s)
 311 {
 312         struct timeval diff;
 313
 314         if (tv_diff(now, barrier, &diff) > 0)
 315                 return;
 316         sched_request_timeout(&diff, s);
 317 }
 318
 319 /**
 320  * Force the next select() call to return before the given time.
 321  *
 322  * \param barrier Absolute time before select() should return.
 323  * \param s Pointer to the scheduler struct.
 324  *
 325  * If \a barrier is in the past, this function requests a minimal timeout.
 326  *
 327  * \sa sched_min_delay(), sched_request_barrier().
 328  */
 329 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
 330 {
 331         struct timeval diff;
 332
 333         if (tv_diff(now, barrier, &diff) > 0)
 334                 return sched_min_delay(s);
 335         sched_request_timeout(&diff, s);
 336 }