src/atimer.c

   1 /* Asynchronous timers.
   2    Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005,
   3                  2006, 2007, 2008, 2009, 2010, 2011  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 #include <unistd.h>
  30
  31 #ifdef HAVE_SYS_TIME_H
  32 #include <sys/time.h>
  33 #endif
  34
  35 /* Free-list of atimer structures.  */
  36
  37 static struct atimer *free_atimers;
  38
  39 /* List of currently not running timers due to a call to
  40    lock_atimer.  */
  41
  42 static struct atimer *stopped_atimers;
  43
  44 /* List of active atimers, sorted by expiration time.  The timer that
  45    will become ripe next is always at the front of this list.  */
  46
  47 static struct atimer *atimers;
  48
  49 /* Non-zero means alarm_signal_handler has found ripe timers but
  50    interrupt_input_blocked was non-zero.  In this case, timer
  51    functions are not called until the next UNBLOCK_INPUT because timer
  52    functions are expected to call X, and X cannot be assumed to be
  53    reentrant.  */
  54
  55 int pending_atimers;
  56
  57 /* Block/unblock SIGALRM.  */
  58
  59 #define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
  60 #define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
  61
  62 /* Function prototypes.  */
  63
  64 static void set_alarm (void);
  65 static void schedule_atimer (struct atimer *);
  66 static struct atimer *append_atimer_lists (struct atimer *,
  67                                            struct atimer *);
  68 SIGTYPE alarm_signal_handler (int signo);
  69
  70
  71 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  72    ripe.  FN is the function to call when the timer fires.
  73    CLIENT_DATA is stored in the client_data member of the atimer
  74    structure returned and so made available to FN when it is called.
  75
  76    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  77    timer fires.
  78
  79    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  80    future.
  81
  82    In both cases, the timer is automatically freed after it has fired.
  83
  84    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  85
  86    Value is a pointer to the atimer started.  It can be used in calls
  87    to cancel_atimer; don't free it yourself.  */
  88
  89 struct atimer *
  90 start_atimer (enum atimer_type type, EMACS_TIME time, atimer_callback fn,
  91               void *client_data)
  92 {
  93   struct atimer *t;
  94
  95   /* Round TIME up to the next full second if we don't have
  96      itimers.  */
  97 #ifndef HAVE_SETITIMER
  98   if (EMACS_USECS (time) != 0)
  99     {
 100       EMACS_SET_USECS (time, 0);
 101       EMACS_SET_SECS (time, EMACS_SECS (time) + 1);
 102     }
 103 #endif /* not HAVE_SETITIMER */
 104
 105   /* Get an atimer structure from the free-list, or allocate
 106      a new one.  */
 107   if (free_atimers)
 108     {
 109       t = free_atimers;
 110       free_atimers = t->next;
 111     }
 112   else
 113     t = (struct atimer *) xmalloc (sizeof *t);
 114
 115   /* Fill the atimer structure.  */
 116   memset (t, 0, sizeof *t);
 117   t->type = type;
 118   t->fn = fn;
 119   t->client_data = client_data;
 120
 121   BLOCK_ATIMERS;
 122
 123   /* Compute the timer's expiration time.  */
 124   switch (type)
 125     {
 126     case ATIMER_ABSOLUTE:
 127       t->expiration = time;
 128       break;
 129
 130     case ATIMER_RELATIVE:
 131       EMACS_GET_TIME (t->expiration);
 132       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 133       break;
 134
 135     case ATIMER_CONTINUOUS:
 136       EMACS_GET_TIME (t->expiration);
 137       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 138       t->interval = time;
 139       break;
 140     }
 141
 142   /* Insert the timer in the list of active atimers.  */
 143   schedule_atimer (t);
 144   UNBLOCK_ATIMERS;
 145
 146   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 147   set_alarm ();
 148
 149   return t;
 150 }
 151
 152
 153 /* Cancel and free atimer TIMER.  */
 154
 155 void
 156 cancel_atimer (struct atimer *timer)
 157 {
 158   int i;
 159
 160   BLOCK_ATIMERS;
 161
 162   for (i = 0; i < 2; ++i)
 163     {
 164       struct atimer *t, *prev;
 165       struct atimer **list = i ? &stopped_atimers : &atimers;
 166
 167       /* See if TIMER is active or stopped.  */
 168       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 169         ;
 170
 171       /* If it is, take it off its list, and put in on the free-list.
 172          We don't bother to arrange for setting a different alarm time,
 173          since a too early one doesn't hurt.  */
 174       if (t)
 175         {
 176           if (prev)
 177             prev->next = t->next;
 178           else
 179             *list = t->next;
 180
 181           t->next = free_atimers;
 182           free_atimers = t;
 183           break;
 184         }
 185     }
 186
 187   UNBLOCK_ATIMERS;
 188 }
 189
 190
 191 /* Append two lists of atimers LIST1 and LIST2 and return the
 192    result list.  */
 193
 194 static struct atimer *
 195 append_atimer_lists (struct atimer *list1, struct atimer *list2)
 196 {
 197   if (list1 == NULL)
 198     return list2;
 199   else if (list2 == NULL)
 200     return list1;
 201   else
 202     {
 203       struct atimer *p;
 204
 205       for (p = list1; p->next; p = p->next)
 206         ;
 207       p->next = list2;
 208       return list1;
 209     }
 210 }
 211
 212
 213 /* Stop all timers except timer T.  T null means stop all timers.  */
 214
 215 void
 216 stop_other_atimers (struct atimer *t)
 217 {
 218   BLOCK_ATIMERS;
 219
 220   if (t)
 221     {
 222       struct atimer *p, *prev;
 223
 224       /* See if T is active.  */
 225       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 226         ;
 227
 228       if (p == t)
 229         {
 230           if (prev)
 231             prev->next = t->next;
 232           else
 233             atimers = t->next;
 234           t->next = NULL;
 235         }
 236       else
 237         /* T is not active.  Let's handle this like T == 0.  */
 238         t = NULL;
 239     }
 240
 241   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 242   atimers = t;
 243   UNBLOCK_ATIMERS;
 244 }
 245
 246
 247 /* Run all timers again, if some have been stopped with a call to
 248    stop_other_atimers.  */
 249
 250 void
 251 run_all_atimers (void)
 252 {
 253   if (stopped_atimers)
 254     {
 255       struct atimer *t = atimers;
 256       struct atimer *next;
 257
 258       BLOCK_ATIMERS;
 259       atimers = stopped_atimers;
 260       stopped_atimers = NULL;
 261
 262       while (t)
 263         {
 264           next = t->next;
 265           schedule_atimer (t);
 266           t = next;
 267         }
 268
 269       UNBLOCK_ATIMERS;
 270     }
 271 }
 272
 273
 274 /* A version of run_all_timers suitable for a record_unwind_protect.  */
 275
 276 Lisp_Object
 277 unwind_stop_other_atimers (Lisp_Object dummy)
 278 {
 279   run_all_atimers ();
 280   return Qnil;
 281 }
 282
 283
 284 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 285
 286 static void
 287 set_alarm (void)
 288 {
 289   if (atimers)
 290     {
 291       EMACS_TIME now, time;
 292 #ifdef HAVE_SETITIMER
 293       struct itimerval it;
 294 #endif
 295
 296       /* Determine s/us till the next timer is ripe.  */
 297       EMACS_GET_TIME (now);
 298       EMACS_SUB_TIME (time, atimers->expiration, now);
 299
 300 #ifdef HAVE_SETITIMER
 301       /* Don't set the interval to 0; this disables the timer.  */
 302       if (EMACS_TIME_LE (atimers->expiration, now))
 303         {
 304           EMACS_SET_SECS (time, 0);
 305           EMACS_SET_USECS (time, 1000);
 306         }
 307
 308       memset (&it, 0, sizeof it);
 309       it.it_value = time;
 310       setitimer (ITIMER_REAL, &it, 0);
 311 #else /* not HAVE_SETITIMER */
 312       alarm (max (EMACS_SECS (time), 1));
 313 #endif /* not HAVE_SETITIMER */
 314     }
 315 }
 316
 317
 318 /* Insert timer T into the list of active atimers `atimers', keeping
 319    the list sorted by expiration time.  T must not be in this list
 320    already.  */
 321
 322 static void
 323 schedule_atimer (struct atimer *t)
 324 {
 325   struct atimer *a = atimers, *prev = NULL;
 326
 327   /* Look for the first atimer that is ripe after T.  */
 328   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 329     prev = a, a = a->next;
 330
 331   /* Insert T in front of the atimer found, if any.  */
 332   if (prev)
 333     prev->next = t;
 334   else
 335     atimers = t;
 336
 337   t->next = a;
 338 }
 339
 340 static void
 341 run_timers (void)
 342 {
 343   EMACS_TIME now;
 344
 345   EMACS_GET_TIME (now);
 346
 347   while (atimers
 348          && (pending_atimers = interrupt_input_blocked) == 0
 349          && EMACS_TIME_LE (atimers->expiration, now))
 350     {
 351       struct atimer *t;
 352
 353       t = atimers;
 354       atimers = atimers->next;
 355       t->fn (t);
 356
 357       if (t->type == ATIMER_CONTINUOUS)
 358         {
 359           EMACS_ADD_TIME (t->expiration, now, t->interval);
 360           schedule_atimer (t);
 361         }
 362       else
 363         {
 364           t->next = free_atimers;
 365           free_atimers = t;
 366         }
 367
 368       EMACS_GET_TIME (now);
 369     }
 370
 371   if (! atimers)
 372     pending_atimers = 0;
 373
 374 #ifdef SYNC_INPUT
 375   if (pending_atimers)
 376     pending_signals = 1;
 377   else
 378     {
 379       pending_signals = interrupt_input_pending;
 380       set_alarm ();
 381     }
 382 #else
 383   if (! pending_atimers)
 384     set_alarm ();
 385 #endif
 386 }
 387
 388
 389 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 390    SIGALRM.  */
 391
 392 SIGTYPE
 393 alarm_signal_handler (int signo)
 394 {
 395 #ifndef SYNC_INPUT
 396   SIGNAL_THREAD_CHECK (signo);
 397 #endif
 398
 399   pending_atimers = 1;
 400 #ifdef SYNC_INPUT
 401   pending_signals = 1;
 402 #else
 403   run_timers ();
 404 #endif
 405 }
 406
 407
 408 /* Call alarm_signal_handler for pending timers.  */
 409
 410 void
 411 do_pending_atimers (void)
 412 {
 413   if (pending_atimers)
 414     {
 415       BLOCK_ATIMERS;
 416       run_timers ();
 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 (int on)
 427 {
 428   if (on)
 429     {
 430       signal (SIGALRM, alarm_signal_handler);
 431       set_alarm ();
 432     }
 433   else
 434     alarm (0);
 435 }
 436
 437
 438 void
 439 init_atimer (void)
 440 {
 441   free_atimers = stopped_atimers = atimers = NULL;
 442   pending_atimers = 0;
 443   /* pending_signals is initialized in init_keyboard.*/
 444   signal (SIGALRM, alarm_signal_handler);
 445 }
 446