src/atimer.c

   1 /* Asynchronous timers.
   2    Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005,
   3                  2006, 2007, 2008, 2009, 2010  Free Software Foundation, Inc.
   4
   5 This file is part of GNU Emacs.
   6
   7 GNU Emacs is free software: you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation, either version 3 of the License, or
  10 (at your option) any later version.
  11
  12 GNU Emacs is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include <config.h>
  21 #include <signal.h>
  22 #include <stdio.h>
  23 #include <setjmp.h>
  24 #include <lisp.h>
  25 #include <syssignal.h>
  26 #include <systime.h>
  27 #include <blockinput.h>
  28 #include <atimer.h>
  29
  30 #ifdef HAVE_UNISTD_H
  31 #include <unistd.h>
  32 #endif
  33
  34 #ifdef HAVE_SYS_TIME_H
  35 #include <sys/time.h>
  36 #endif
  37
  38 /* Free-list of atimer structures.  */
  39
  40 static struct atimer *free_atimers;
  41
  42 /* List of currently not running timers due to a call to
  43    lock_atimer.  */
  44
  45 static struct atimer *stopped_atimers;
  46
  47 /* List of active atimers, sorted by expiration time.  The timer that
  48    will become ripe next is always at the front of this list.  */
  49
  50 static struct atimer *atimers;
  51
  52 /* Non-zero means alarm_signal_handler has found ripe timers but
  53    interrupt_input_blocked was non-zero.  In this case, timer
  54    functions are not called until the next UNBLOCK_INPUT because timer
  55    functions are expected to call X, and X cannot be assumed to be
  56    reentrant.  */
  57
  58 int pending_atimers;
  59
  60 /* Block/unblock SIGALRM.  */
  61
  62 #define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
  63 #define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
  64
  65 /* Function prototypes.  */
  66
  67 static void set_alarm (void);
  68 static void schedule_atimer (struct atimer *);
  69 static struct atimer *append_atimer_lists (struct atimer *,
  70                                            struct atimer *);
  71 SIGTYPE alarm_signal_handler (int signo);
  72
  73
  74 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  75    ripe.  FN is the function to call when the timer fires.
  76    CLIENT_DATA is stored in the client_data member of the atimer
  77    structure returned and so made available to FN when it is called.
  78
  79    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  80    timer fires.
  81
  82    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  83    future.
  84
  85    In both cases, the timer is automatically freed after it has fired.
  86
  87    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  88
  89    Value is a pointer to the atimer started.  It can be used in calls
  90    to cancel_atimer; don't free it yourself.  */
  91
  92 struct atimer *
  93 start_atimer (enum atimer_type type, struct timeval time, atimer_callback fn, void *client_data)
  94 {
  95   struct atimer *t;
  96
  97   /* Round TIME up to the next full second if we don't have
  98      itimers.  */
  99 #ifndef HAVE_SETITIMER
 100   if (EMACS_USECS (time) != 0)
 101     {
 102       EMACS_SET_USECS (time, 0);
 103       EMACS_SET_SECS (time, EMACS_SECS (time) + 1);
 104     }
 105 #endif /* not HAVE_SETITIMER */
 106
 107   /* Get an atimer structure from the free-list, or allocate
 108      a new one.  */
 109   if (free_atimers)
 110     {
 111       t = free_atimers;
 112       free_atimers = t->next;
 113     }
 114   else
 115     t = (struct atimer *) xmalloc (sizeof *t);
 116
 117   /* Fill the atimer structure.  */
 118   bzero (t, sizeof *t);
 119   t->type = type;
 120   t->fn = fn;
 121   t->client_data = client_data;
 122
 123   BLOCK_ATIMERS;
 124
 125   /* Compute the timer's expiration time.  */
 126   switch (type)
 127     {
 128     case ATIMER_ABSOLUTE:
 129       t->expiration = time;
 130       break;
 131
 132     case ATIMER_RELATIVE:
 133       EMACS_GET_TIME (t->expiration);
 134       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 135       break;
 136
 137     case ATIMER_CONTINUOUS:
 138       EMACS_GET_TIME (t->expiration);
 139       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 140       t->interval = time;
 141       break;
 142     }
 143
 144   /* Insert the timer in the list of active atimers.  */
 145   schedule_atimer (t);
 146   UNBLOCK_ATIMERS;
 147
 148   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 149   set_alarm ();
 150
 151   return t;
 152 }
 153
 154
 155 /* Cancel and free atimer TIMER.  */
 156
 157 void
 158 cancel_atimer (struct atimer *timer)
 159 {
 160   int i;
 161
 162   BLOCK_ATIMERS;
 163
 164   for (i = 0; i < 2; ++i)
 165     {
 166       struct atimer *t, *prev;
 167       struct atimer **list = i ? &stopped_atimers : &atimers;
 168
 169       /* See if TIMER is active or stopped.  */
 170       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 171         ;
 172
 173       /* If it is, take it off the its list, and put in on the
 174          free-list.  We don't bother to arrange for setting a
 175          different alarm time, since a too early one doesn't hurt.  */
 176       if (t)
 177         {
 178           if (prev)
 179             prev->next = t->next;
 180           else
 181             *list = t->next;
 182
 183           t->next = free_atimers;
 184           free_atimers = t;
 185           break;
 186         }
 187     }
 188
 189   UNBLOCK_ATIMERS;
 190 }
 191
 192
 193 /* Append two lists of atimers LIST1 and LIST2 and return the
 194    result list.  */
 195
 196 static struct atimer *
 197 append_atimer_lists (struct atimer *list1, struct atimer *list2)
 198 {
 199   if (list1 == NULL)
 200     return list2;
 201   else if (list2 == NULL)
 202     return list1;
 203   else
 204     {
 205       struct atimer *p;
 206
 207       for (p = list1; p->next; p = p->next)
 208         ;
 209       p->next = list2;
 210       return list1;
 211     }
 212 }
 213
 214
 215 /* Stop all timers except timer T.  T null means stop all timers.  */
 216
 217 void
 218 stop_other_atimers (struct atimer *t)
 219 {
 220   BLOCK_ATIMERS;
 221
 222   if (t)
 223     {
 224       struct atimer *p, *prev;
 225
 226       /* See if T is active.  */
 227       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 228         ;
 229
 230       if (p == t)
 231         {
 232           if (prev)
 233             prev->next = t->next;
 234           else
 235             atimers = t->next;
 236           t->next = NULL;
 237         }
 238       else
 239         /* T is not active.  Let's handle this like T == 0.  */
 240         t = NULL;
 241     }
 242
 243   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 244   atimers = t;
 245   UNBLOCK_ATIMERS;
 246 }
 247
 248
 249 /* Run all timers again, if some have been stopped with a call to
 250    stop_other_atimers.  */
 251
 252 void
 253 run_all_atimers (void)
 254 {
 255   if (stopped_atimers)
 256     {
 257       struct atimer *t = atimers;
 258       struct atimer *next;
 259
 260       BLOCK_ATIMERS;
 261       atimers = stopped_atimers;
 262       stopped_atimers = NULL;
 263
 264       while (t)
 265         {
 266           next = t->next;
 267           schedule_atimer (t);
 268           t = next;
 269         }
 270
 271       UNBLOCK_ATIMERS;
 272     }
 273 }
 274
 275
 276 /* A version of run_all_timers suitable for a record_unwind_protect.  */
 277
 278 Lisp_Object
 279 unwind_stop_other_atimers (Lisp_Object dummy)
 280 {
 281   run_all_atimers ();
 282   return Qnil;
 283 }
 284
 285
 286 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 287
 288 static void
 289 set_alarm (void)
 290 {
 291   if (atimers)
 292     {
 293       EMACS_TIME now, time;
 294 #ifdef HAVE_SETITIMER
 295       struct itimerval it;
 296 #endif
 297
 298       /* Determine s/us till the next timer is ripe.  */
 299       EMACS_GET_TIME (now);
 300       EMACS_SUB_TIME (time, atimers->expiration, now);
 301
 302 #ifdef HAVE_SETITIMER
 303       /* Don't set the interval to 0; this disables the timer.  */
 304       if (EMACS_TIME_LE (atimers->expiration, now))
 305         {
 306           EMACS_SET_SECS (time, 0);
 307           EMACS_SET_USECS (time, 1000);
 308         }
 309
 310       bzero (&it, sizeof it);
 311       it.it_value = time;
 312       setitimer (ITIMER_REAL, &it, 0);
 313 #else /* not HAVE_SETITIMER */
 314       alarm (max (EMACS_SECS (time), 1));
 315 #endif /* not HAVE_SETITIMER */
 316     }
 317 }
 318
 319
 320 /* Insert timer T into the list of active atimers `atimers', keeping
 321    the list sorted by expiration time.  T must not be in this list
 322    already.  */
 323
 324 static void
 325 schedule_atimer (struct atimer *t)
 326 {
 327   struct atimer *a = atimers, *prev = NULL;
 328
 329   /* Look for the first atimer that is ripe after T.  */
 330   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 331     prev = a, a = a->next;
 332
 333   /* Insert T in front of the atimer found, if any.  */
 334   if (prev)
 335     prev->next = t;
 336   else
 337     atimers = t;
 338
 339   t->next = a;
 340 }
 341
 342 static void
 343 run_timers (void)
 344 {
 345   EMACS_TIME now;
 346
 347   EMACS_GET_TIME (now);
 348
 349   while (atimers
 350          && (pending_atimers = interrupt_input_blocked) == 0
 351          && EMACS_TIME_LE (atimers->expiration, now))
 352     {
 353       struct atimer *t;
 354
 355       t = atimers;
 356       atimers = atimers->next;
 357       t->fn (t);
 358
 359       if (t->type == ATIMER_CONTINUOUS)
 360         {
 361           EMACS_ADD_TIME (t->expiration, now, t->interval);
 362           schedule_atimer (t);
 363         }
 364       else
 365         {
 366           t->next = free_atimers;
 367           free_atimers = t;
 368         }
 369
 370       EMACS_GET_TIME (now);
 371     }
 372
 373   if (! atimers)
 374     pending_atimers = 0;
 375
 376 #ifdef SYNC_INPUT
 377   if (pending_atimers)
 378     pending_signals = 1;
 379   else
 380     {
 381       pending_signals = interrupt_input_pending;
 382       set_alarm ();
 383     }
 384 #else
 385   if (! pending_atimers)
 386     set_alarm ();
 387 #endif
 388 }
 389
 390
 391 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 392    SIGALRM.  */
 393
 394 SIGTYPE
 395 alarm_signal_handler (int signo)
 396 {
 397 #ifndef SYNC_INPUT
 398   SIGNAL_THREAD_CHECK (signo);
 399 #endif
 400
 401   pending_atimers = 1;
 402 #ifdef SYNC_INPUT
 403   pending_signals = 1;
 404 #else
 405   run_timers ();
 406 #endif
 407 }
 408
 409
 410 /* Call alarm_signal_handler for pending timers.  */
 411
 412 void
 413 do_pending_atimers (void)
 414 {
 415   if (pending_atimers)
 416     {
 417       BLOCK_ATIMERS;
 418       run_timers ();
 419       UNBLOCK_ATIMERS;
 420     }
 421 }
 422
 423
 424 /* Turn alarms on/off.  This seems to be temporarily necessary on
 425    some systems like HPUX (see process.c).  */
 426
 427 void
 428 turn_on_atimers (int on)
 429 {
 430   if (on)
 431     {
 432       signal (SIGALRM, alarm_signal_handler);
 433       set_alarm ();
 434     }
 435   else
 436     alarm (0);
 437 }
 438
 439
 440 void
 441 init_atimer (void)
 442 {
 443   free_atimers = stopped_atimers = atimers = NULL;
 444   pending_atimers = 0;
 445   /* pending_signals is initialized in init_keyboard.*/
 446   signal (SIGALRM, alarm_signal_handler);
 447 }
 448
 449 /* arch-tag: e6308261-eec6-404b-89fb-6e5909518d70
 450    (do not change this comment) */