src/atimer.c

   1 /* Asynchronous timers.
   2    Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005,
   3                  2006, 2007  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 2, or (at your option)
  10 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; see the file COPYING.  If not, write to
  19 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  20 Boston, MA 02110-1301, USA.  */
  21
  22 #include <config.h>
  23 #include <signal.h>
  24 #include <stdio.h>
  25 #include <lisp.h>
  26 #include <syssignal.h>
  27 #include <systime.h>
  28 #include <blockinput.h>
  29 #include <atimer.h>
  30
  31 #ifdef HAVE_UNISTD_H
  32 #include <unistd.h>
  33 #endif
  34
  35 #ifdef HAVE_SYS_TIME_H
  36 #include <sys/time.h>
  37 #endif
  38
  39 /* Free-list of atimer structures.  */
  40
  41 static struct atimer *free_atimers;
  42
  43 /* List of currently not running timers due to a call to
  44    lock_atimer.  */
  45
  46 static struct atimer *stopped_atimers;
  47
  48 /* List of active atimers, sorted by expiration time.  The timer that
  49    will become ripe next is always at the front of this list.  */
  50
  51 static struct atimer *atimers;
  52
  53 /* Non-zero means alarm_signal_handler has found ripe timers but
  54    interrupt_input_blocked was non-zero.  In this case, timer
  55    functions are not called until the next UNBLOCK_INPUT because timer
  56    functions are expected to call X, and X cannot be assumed to be
  57    reentrant.  */
  58
  59 int pending_atimers;
  60
  61 /* Block/unblock SIGALRM.  */
  62
  63 #define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
  64 #define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
  65
  66 /* Function prototypes.  */
  67
  68 static void set_alarm P_ ((void));
  69 static void schedule_atimer P_ ((struct atimer *));
  70 static struct atimer *append_atimer_lists P_ ((struct atimer *,
  71                                                struct atimer *));
  72 SIGTYPE alarm_signal_handler ();
  73
  74
  75 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  76    ripe.  FN is the function to call when the timer fires.
  77    CLIENT_DATA is stored in the client_data member of the atimer
  78    structure returned and so made available to FN when it is called.
  79
  80    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  81    timer fires.
  82
  83    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  84    future.
  85
  86    In both cases, the timer is automatically freed after it has fired.
  87
  88    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  89
  90    Value is a pointer to the atimer started.  It can be used in calls
  91    to cancel_atimer; don't free it yourself.  */
  92
  93 struct atimer *
  94 start_atimer (type, time, fn, client_data)
  95      enum atimer_type type;
  96      EMACS_TIME time;
  97      atimer_callback fn;
  98      void *client_data;
  99 {
 100   struct atimer *t;
 101
 102   /* Round TIME up to the next full second if we don't have
 103      itimers.  */
 104 #ifndef HAVE_SETITIMER
 105   if (EMACS_USECS (time) != 0)
 106     {
 107       EMACS_SET_USECS (time, 0);
 108       EMACS_SET_SECS (time, EMACS_SECS (time) + 1);
 109     }
 110 #endif /* not HAVE_SETITIMER */
 111
 112   /* Get an atimer structure from the free-list, or allocate
 113      a new one.  */
 114   if (free_atimers)
 115     {
 116       t = free_atimers;
 117       free_atimers = t->next;
 118     }
 119   else
 120     t = (struct atimer *) xmalloc (sizeof *t);
 121
 122   /* Fill the atimer structure.  */
 123   bzero (t, sizeof *t);
 124   t->type = type;
 125   t->fn = fn;
 126   t->client_data = client_data;
 127
 128   BLOCK_ATIMERS;
 129
 130   /* Compute the timer's expiration time.  */
 131   switch (type)
 132     {
 133     case ATIMER_ABSOLUTE:
 134       t->expiration = time;
 135       break;
 136
 137     case ATIMER_RELATIVE:
 138       EMACS_GET_TIME (t->expiration);
 139       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 140       break;
 141
 142     case ATIMER_CONTINUOUS:
 143       EMACS_GET_TIME (t->expiration);
 144       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 145       t->interval = time;
 146       break;
 147     }
 148
 149   /* Insert the timer in the list of active atimers.  */
 150   schedule_atimer (t);
 151   UNBLOCK_ATIMERS;
 152
 153   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 154   set_alarm ();
 155
 156   return t;
 157 }
 158
 159
 160 /* Cancel and free atimer TIMER.  */
 161
 162 void
 163 cancel_atimer (timer)
 164      struct atimer *timer;
 165 {
 166   int i;
 167
 168   BLOCK_ATIMERS;
 169
 170   for (i = 0; i < 2; ++i)
 171     {
 172       struct atimer *t, *prev;
 173       struct atimer **list = i ? &stopped_atimers : &atimers;
 174
 175       /* See if TIMER is active or stopped.  */
 176       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 177         ;
 178
 179       /* If it is, take it off the its list, and put in on the
 180          free-list.  We don't bother to arrange for setting a
 181          different alarm time, since a too early one doesn't hurt.  */
 182       if (t)
 183         {
 184           if (prev)
 185             prev->next = t->next;
 186           else
 187             *list = t->next;
 188
 189           t->next = free_atimers;
 190           free_atimers = t;
 191           break;
 192         }
 193     }
 194
 195   UNBLOCK_ATIMERS;
 196 }
 197
 198
 199 /* Append two lists of atimers LIST1 and LIST2 and return the
 200    result list.  */
 201
 202 static struct atimer *
 203 append_atimer_lists (list1, list2)
 204      struct atimer *list1, *list2;
 205 {
 206   if (list1 == NULL)
 207     return list2;
 208   else if (list2 == NULL)
 209     return list1;
 210   else
 211     {
 212       struct atimer *p;
 213
 214       for (p = list1; p->next; p = p->next)
 215         ;
 216       p->next = list2;
 217       return list1;
 218     }
 219 }
 220
 221
 222 /* Stop all timers except timer T.  T null means stop all timers.  */
 223
 224 void
 225 stop_other_atimers (t)
 226      struct atimer *t;
 227 {
 228   BLOCK_ATIMERS;
 229
 230   if (t)
 231     {
 232       struct atimer *p, *prev;
 233
 234       /* See if T is active.  */
 235       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 236         ;
 237
 238       if (p == t)
 239         {
 240           if (prev)
 241             prev->next = t->next;
 242           else
 243             atimers = t->next;
 244           t->next = NULL;
 245         }
 246       else
 247         /* T is not active.  Let's handle this like T == 0.  */
 248         t = NULL;
 249     }
 250
 251   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 252   atimers = t;
 253   UNBLOCK_ATIMERS;
 254 }
 255
 256
 257 /* Run all timers again, if some have been stopped with a call to
 258    stop_other_atimers.  */
 259
 260 void
 261 run_all_atimers ()
 262 {
 263   if (stopped_atimers)
 264     {
 265       struct atimer *t = atimers;
 266       struct atimer *next;
 267
 268       BLOCK_ATIMERS;
 269       atimers = stopped_atimers;
 270       stopped_atimers = NULL;
 271
 272       while (t)
 273         {
 274           next = t->next;
 275           schedule_atimer (t);
 276           t = next;
 277         }
 278
 279       UNBLOCK_ATIMERS;
 280     }
 281 }
 282
 283
 284 /* A version of run_all_timers suitable for a record_unwind_protect.  */
 285
 286 Lisp_Object
 287 unwind_stop_other_atimers (dummy)
 288      Lisp_Object dummy;
 289 {
 290   run_all_atimers ();
 291   return Qnil;
 292 }
 293
 294
 295 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 296
 297 static void
 298 set_alarm ()
 299 {
 300 #if defined (USG) && !defined (POSIX_SIGNALS)
 301   /* USG systems forget handlers when they are used;
 302      must reestablish each time.  */
 303   signal (SIGALRM, alarm_signal_handler);
 304 #endif /* USG */
 305
 306   if (atimers)
 307     {
 308       EMACS_TIME now, time;
 309 #ifdef HAVE_SETITIMER
 310       struct itimerval it;
 311 #endif
 312
 313       /* Determine s/us till the next timer is ripe.  */
 314       EMACS_GET_TIME (now);
 315       EMACS_SUB_TIME (time, atimers->expiration, now);
 316
 317 #ifdef HAVE_SETITIMER
 318       /* Don't set the interval to 0; this disables the timer.  */
 319       if (EMACS_TIME_LE (atimers->expiration, now))
 320         {
 321           EMACS_SET_SECS (time, 0);
 322           EMACS_SET_USECS (time, 1000);
 323         }
 324
 325       bzero (&it, sizeof it);
 326       it.it_value = time;
 327       setitimer (ITIMER_REAL, &it, 0);
 328 #else /* not HAVE_SETITIMER */
 329       alarm (max (EMACS_SECS (time), 1));
 330 #endif /* not HAVE_SETITIMER */
 331     }
 332 }
 333
 334
 335 /* Insert timer T into the list of active atimers `atimers', keeping
 336    the list sorted by expiration time.  T must not be in this list
 337    already.  */
 338
 339 static void
 340 schedule_atimer (t)
 341      struct atimer *t;
 342 {
 343   struct atimer *a = atimers, *prev = NULL;
 344
 345   /* Look for the first atimer that is ripe after T.  */
 346   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 347     prev = a, a = a->next;
 348
 349   /* Insert T in front of the atimer found, if any.  */
 350   if (prev)
 351     prev->next = t;
 352   else
 353     atimers = t;
 354
 355   t->next = a;
 356 }
 357
 358
 359 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 360    SIGALRM.  */
 361
 362 SIGTYPE
 363 alarm_signal_handler (signo)
 364      int signo;
 365 {
 366   EMACS_TIME now;
 367
 368   SIGNAL_THREAD_CHECK (signo);
 369
 370   EMACS_GET_TIME (now);
 371   pending_atimers = 0;
 372
 373   while (atimers
 374          && (pending_atimers = interrupt_input_blocked) == 0
 375          && EMACS_TIME_LE (atimers->expiration, now))
 376     {
 377       struct atimer *t;
 378
 379       t = atimers;
 380       atimers = atimers->next;
 381 #ifndef MAC_OSX
 382       t->fn (t);
 383 #endif
 384
 385       if (t->type == ATIMER_CONTINUOUS)
 386         {
 387           EMACS_ADD_TIME (t->expiration, now, t->interval);
 388           schedule_atimer (t);
 389         }
 390       else
 391         {
 392           t->next = free_atimers;
 393           free_atimers = t;
 394         }
 395 #ifdef MAC_OSX
 396       /* Fix for Ctrl-G.  Perhaps this should apply to all platforms. */
 397       t->fn (t);
 398 #endif
 399
 400       EMACS_GET_TIME (now);
 401     }
 402
 403   if (! pending_atimers)
 404     set_alarm ();
 405 }
 406
 407
 408 /* Call alarm_signal_handler for pending timers.  */
 409
 410 void
 411 do_pending_atimers ()
 412 {
 413   if (pending_atimers)
 414     {
 415       BLOCK_ATIMERS;
 416       alarm_signal_handler (SIGALRM);
 417       UNBLOCK_ATIMERS;
 418     }
 419 }
 420
 421
 422 /* Turn alarms on/off.  This seems to be temporarily necessary on
 423    some systems like HPUX (see process.c).  */
 424
 425 void
 426 turn_on_atimers (on)
 427      int on;
 428 {
 429   if (on)
 430     {
 431       signal (SIGALRM, alarm_signal_handler);
 432       set_alarm ();
 433     }
 434   else
 435     alarm (0);
 436 }
 437
 438
 439 void
 440 init_atimer ()
 441 {
 442   free_atimers = atimers = NULL;
 443   pending_atimers = 0;
 444   signal (SIGALRM, alarm_signal_handler);
 445 }
 446
 447 /* arch-tag: e6308261-eec6-404b-89fb-6e5909518d70
 448    (do not change this comment) */