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, EMACS_TIME time, atimer_callback fn,
  94               void *client_data)
  95 {
  96   struct atimer *t;
  97
  98   /* Round TIME up to the next full second if we don't have
  99      itimers.  */
 100 #ifndef HAVE_SETITIMER
 101   if (EMACS_USECS (time) != 0)
 102     {
 103       EMACS_SET_USECS (time, 0);
 104       EMACS_SET_SECS (time, EMACS_SECS (time) + 1);
 105     }
 106 #endif /* not HAVE_SETITIMER */
 107
 108   /* Get an atimer structure from the free-list, or allocate
 109      a new one.  */
 110   if (free_atimers)
 111     {
 112       t = free_atimers;
 113       free_atimers = t->next;
 114     }
 115   else
 116     t = (struct atimer *) xmalloc (sizeof *t);
 117
 118   /* Fill the atimer structure.  */
 119   memset (t, 0, sizeof *t);
 120   t->type = type;
 121   t->fn = fn;
 122   t->client_data = client_data;
 123
 124   BLOCK_ATIMERS;
 125
 126   /* Compute the timer's expiration time.  */
 127   switch (type)
 128     {
 129     case ATIMER_ABSOLUTE:
 130       t->expiration = time;
 131       break;
 132
 133     case ATIMER_RELATIVE:
 134       EMACS_GET_TIME (t->expiration);
 135       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 136       break;
 137
 138     case ATIMER_CONTINUOUS:
 139       EMACS_GET_TIME (t->expiration);
 140       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 141       t->interval = time;
 142       break;
 143     }
 144
 145   /* Insert the timer in the list of active atimers.  */
 146   schedule_atimer (t);
 147   UNBLOCK_ATIMERS;
 148
 149   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 150   set_alarm ();
 151
 152   return t;
 153 }
 154
 155
 156 /* Cancel and free atimer TIMER.  */
 157
 158 void
 159 cancel_atimer (struct atimer *timer)
 160 {
 161   int i;
 162
 163   BLOCK_ATIMERS;
 164
 165   for (i = 0; i < 2; ++i)
 166     {
 167       struct atimer *t, *prev;
 168       struct atimer **list = i ? &stopped_atimers : &atimers;
 169
 170       /* See if TIMER is active or stopped.  */
 171       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 172         ;
 173
 174       /* If it is, take it off its list, and put in on the free-list.
 175          We don't bother to arrange for setting a different alarm time,
 176          since a too early one doesn't hurt.  */
 177       if (t)
 178         {
 179           if (prev)
 180             prev->next = t->next;
 181           else
 182             *list = t->next;
 183
 184           t->next = free_atimers;
 185           free_atimers = t;
 186           break;
 187         }
 188     }
 189
 190   UNBLOCK_ATIMERS;
 191 }
 192
 193
 194 /* Append two lists of atimers LIST1 and LIST2 and return the
 195    result list.  */
 196
 197 static struct atimer *
 198 append_atimer_lists (struct atimer *list1, struct atimer *list2)
 199 {
 200   if (list1 == NULL)
 201     return list2;
 202   else if (list2 == NULL)
 203     return list1;
 204   else
 205     {
 206       struct atimer *p;
 207
 208       for (p = list1; p->next; p = p->next)
 209         ;
 210       p->next = list2;
 211       return list1;
 212     }
 213 }
 214
 215
 216 /* Stop all timers except timer T.  T null means stop all timers.  */
 217
 218 void
 219 stop_other_atimers (struct atimer *t)
 220 {
 221   BLOCK_ATIMERS;
 222
 223   if (t)
 224     {
 225       struct atimer *p, *prev;
 226
 227       /* See if T is active.  */
 228       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 229         ;
 230
 231       if (p == t)
 232         {
 233           if (prev)
 234             prev->next = t->next;
 235           else
 236             atimers = t->next;
 237           t->next = NULL;
 238         }
 239       else
 240         /* T is not active.  Let's handle this like T == 0.  */
 241         t = NULL;
 242     }
 243
 244   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 245   atimers = t;
 246   UNBLOCK_ATIMERS;
 247 }
 248
 249
 250 /* Run all timers again, if some have been stopped with a call to
 251    stop_other_atimers.  */
 252
 253 void
 254 run_all_atimers (void)
 255 {
 256   if (stopped_atimers)
 257     {
 258       struct atimer *t = atimers;
 259       struct atimer *next;
 260
 261       BLOCK_ATIMERS;
 262       atimers = stopped_atimers;
 263       stopped_atimers = NULL;
 264
 265       while (t)
 266         {
 267           next = t->next;
 268           schedule_atimer (t);
 269           t = next;
 270         }
 271
 272       UNBLOCK_ATIMERS;
 273     }
 274 }
 275
 276
 277 /* A version of run_all_timers suitable for a record_unwind_protect.  */
 278
 279 Lisp_Object
 280 unwind_stop_other_atimers (Lisp_Object dummy)
 281 {
 282   run_all_atimers ();
 283   return Qnil;
 284 }
 285
 286
 287 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 288
 289 static void
 290 set_alarm (void)
 291 {
 292   if (atimers)
 293     {
 294       EMACS_TIME now, time;
 295 #ifdef HAVE_SETITIMER
 296       struct itimerval it;
 297 #endif
 298
 299       /* Determine s/us till the next timer is ripe.  */
 300       EMACS_GET_TIME (now);
 301       EMACS_SUB_TIME (time, atimers->expiration, now);
 302
 303 #ifdef HAVE_SETITIMER
 304       /* Don't set the interval to 0; this disables the timer.  */
 305       if (EMACS_TIME_LE (atimers->expiration, now))
 306         {
 307           EMACS_SET_SECS (time, 0);
 308           EMACS_SET_USECS (time, 1000);
 309         }
 310
 311       memset (&it, 0, sizeof it);
 312       it.it_value = time;
 313       setitimer (ITIMER_REAL, &it, 0);
 314 #else /* not HAVE_SETITIMER */
 315       alarm (max (EMACS_SECS (time), 1));
 316 #endif /* not HAVE_SETITIMER */
 317     }
 318 }
 319
 320
 321 /* Insert timer T into the list of active atimers `atimers', keeping
 322    the list sorted by expiration time.  T must not be in this list
 323    already.  */
 324
 325 static void
 326 schedule_atimer (struct atimer *t)
 327 {
 328   struct atimer *a = atimers, *prev = NULL;
 329
 330   /* Look for the first atimer that is ripe after T.  */
 331   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 332     prev = a, a = a->next;
 333
 334   /* Insert T in front of the atimer found, if any.  */
 335   if (prev)
 336     prev->next = t;
 337   else
 338     atimers = t;
 339
 340   t->next = a;
 341 }
 342
 343 static void
 344 run_timers (void)
 345 {
 346   EMACS_TIME now;
 347
 348   EMACS_GET_TIME (now);
 349
 350   while (atimers
 351          && (pending_atimers = interrupt_input_blocked) == 0
 352          && EMACS_TIME_LE (atimers->expiration, now))
 353     {
 354       struct atimer *t;
 355
 356       t = atimers;
 357       atimers = atimers->next;
 358       t->fn (t);
 359
 360       if (t->type == ATIMER_CONTINUOUS)
 361         {
 362           EMACS_ADD_TIME (t->expiration, now, t->interval);
 363           schedule_atimer (t);
 364         }
 365       else
 366         {
 367           t->next = free_atimers;
 368           free_atimers = t;
 369         }
 370
 371       EMACS_GET_TIME (now);
 372     }
 373
 374   if (! atimers)
 375     pending_atimers = 0;
 376
 377 #ifdef SYNC_INPUT
 378   if (pending_atimers)
 379     pending_signals = 1;
 380   else
 381     {
 382       pending_signals = interrupt_input_pending;
 383       set_alarm ();
 384     }
 385 #else
 386   if (! pending_atimers)
 387     set_alarm ();
 388 #endif
 389 }
 390
 391
 392 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 393    SIGALRM.  */
 394
 395 SIGTYPE
 396 alarm_signal_handler (int signo)
 397 {
 398 #ifndef SYNC_INPUT
 399   SIGNAL_THREAD_CHECK (signo);
 400 #endif
 401
 402   pending_atimers = 1;
 403 #ifdef SYNC_INPUT
 404   pending_signals = 1;
 405 #else
 406   run_timers ();
 407 #endif
 408 }
 409
 410
 411 /* Call alarm_signal_handler for pending timers.  */
 412
 413 void
 414 do_pending_atimers (void)
 415 {
 416   if (pending_atimers)
 417     {
 418       BLOCK_ATIMERS;
 419       run_timers ();
 420       UNBLOCK_ATIMERS;
 421     }
 422 }
 423
 424
 425 /* Turn alarms on/off.  This seems to be temporarily necessary on
 426    some systems like HPUX (see process.c).  */
 427
 428 void
 429 turn_on_atimers (int on)
 430 {
 431   if (on)
 432     {
 433       signal (SIGALRM, alarm_signal_handler);
 434       set_alarm ();
 435     }
 436   else
 437     alarm (0);
 438 }
 439
 440
 441 void
 442 init_atimer (void)
 443 {
 444   free_atimers = stopped_atimers = atimers = NULL;
 445   pending_atimers = 0;
 446   /* pending_signals is initialized in init_keyboard.*/
 447   signal (SIGALRM, alarm_signal_handler);
 448 }
 449
 450 /* arch-tag: e6308261-eec6-404b-89fb-6e5909518d70
 451    (do not change this comment) */