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