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->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, &s->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                 unregister_task(t);
 211         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node)
 212                 unregister_task(t);
 213         initialized = 0;
 214 }
 215
 216 /**
 217  * Get the list of all registered tasks.
 218  *
 219  * \return The task list.
 220  *
 221  * Each entry of the list contains an identifier which is simply a hex number
 222  * that may be used in \a kill_task() to terminate the task.
 223  * The result is dynamically allocated and must be freed by the caller.
 224  */
 225 char *get_task_list(void)
 226 {
 227         struct task *t, *tmp;
 228         char *msg = NULL;
 229
 230         if (!initialized)
 231                 return NULL;
 232         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 233                 char *tmp_msg;
 234                 tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status);
 235                 free(msg);
 236                 msg = tmp_msg;
 237         }
 238         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 239                 char *tmp_msg;
 240 //              if (t->pre_select)
 241 //                      continue;
 242                 tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status);
 243                 free(msg);
 244                 msg = tmp_msg;
 245         }
 246         //PARA_DEBUG_LOG("task list:\n%s", msg);
 247         return msg;
 248 }
 249
 250 /**
 251  * Simulate an error for the given task.
 252  *
 253  * \param id The task identifier.
 254  *
 255  * Find the task identified by \a id, set the tasks' error value to
 256  * \p -E_TASK_KILLED and unregister the task.
 257  *
 258  * \return Positive on success, negative on errors (e.g. if \a id does not
 259  * correspond to a registered task).
 260  */
 261 int kill_task(char *id)
 262 {
 263         struct task *t, *tmp;
 264         char buf[20];
 265
 266         if (!initialized)
 267                 return -E_NOT_INITIALIZED;
 268         list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) {
 269                 sprintf(buf, "%p", t);
 270                 if (strcmp(id, buf))
 271                         continue;
 272                 t->error = -E_TASK_KILLED;
 273                 return 1;
 274         }
 275         list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) {
 276                 sprintf(buf, "%p", t);
 277                 if (strcmp(id, buf))
 278                         continue;
 279                 t->error = -E_TASK_KILLED;
 280                 return 1;
 281         }
 282         return -E_NO_SUCH_TASK;
 283 }
 284
 285 /**
 286  * Set the select timeout to the minimal possible value.
 287  *
 288  * \param s Pointer to the scheduler struct.
 289  *
 290  * This causes the next select() call to return immediately.
 291  */
 292 void sched_min_delay(struct sched *s)
 293 {
 294         s->timeout.tv_sec = 0;
 295         s->timeout.tv_usec = 1;
 296 }
 297
 298 /**
 299  * Impose an upper bound for the timeout of the next select() call.
 300  *
 301  * \param timeout Maximal allowed timeout.
 302  * \param s Pointer to the scheduler struct.
 303  *
 304  * If the current scheduler timeout is already smaller than \a timeout, this
 305  * function does nothing. Otherwise the timeout for the next select() call is
 306  * set to the given value.
 307  *
 308  * \sa sched_request_timeout_ms().
 309  */
 310 void sched_request_timeout(struct timeval *timeout, struct sched *s)
 311 {
 312         if (tv_diff(&s->timeout, timeout, NULL) > 0)
 313                 s->timeout = *timeout;
 314 }
 315
 316 /**
 317  * Force the next select() call to return before the given amount of milliseconds.
 318  *
 319  * \param ms The maximal allowed timeout in milliseconds.
 320  * \param s Pointer to the scheduler struct.
 321  *
 322  * Like sched_request_timeout() this imposes an upper bound on the timeout
 323  * value for the next select() call.
 324  */
 325 void sched_request_timeout_ms(long unsigned ms, struct sched *s)
 326 {
 327         struct timeval tv;
 328         ms2tv(ms, &tv);
 329         sched_request_timeout(&tv, s);
 330 }
 331
 332 /**
 333  * Force the next select() call to return before the given future time.
 334  *
 335  * \param barrier Absolute time before select() should return.
 336  * \param s Pointer to the scheduler struct.
 337  *
 338  * If \a barrier is in the past, this function does nothing.
 339  *
 340  * \sa sched_request_barrier_or_min_delay().
 341  */
 342 void sched_request_barrier(struct timeval *barrier, struct sched *s)
 343 {
 344         struct timeval diff;
 345
 346         if (tv_diff(now, barrier, &diff) > 0)
 347                 return;
 348         sched_request_timeout(&diff, s);
 349 }
 350
 351 /**
 352  * Force the next select() call to return before the given time.
 353  *
 354  * \param barrier Absolute time before select() should return.
 355  * \param s Pointer to the scheduler struct.
 356  *
 357  * If \a barrier is in the past, this function requests a minimal timeout.
 358  *
 359  * \sa sched_min_delay(), sched_request_barrier().
 360  */
 361 void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s)
 362 {
 363         struct timeval diff;
 364
 365         if (tv_diff(now, barrier, &diff) > 0)
 366                 return sched_min_delay(s);
 367         sched_request_timeout(&diff, s);
 368 }