src/atimer.c

   1 /* Asynchronous timers.
   2    Copyright (C) 2000-2012  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software: you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation, either version 3 of the License, or
   9 (at your option) any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20 #include <signal.h>
  21 #include <stdio.h>
  22 #include <setjmp.h>
  23 #include "lisp.h"
  24 #include "syssignal.h"
  25 #include "systime.h"
  26 #include "blockinput.h"
  27 #include "atimer.h"
  28 #include <unistd.h>
  29
  30 #ifdef HAVE_SYS_TIME_H
  31 #include <sys/time.h>
  32 #endif
  33
  34 /* Free-list of atimer structures.  */
  35
  36 static struct atimer *free_atimers;
  37
  38 /* List of currently not running timers due to a call to
  39    lock_atimer.  */
  40
  41 static struct atimer *stopped_atimers;
  42
  43 /* List of active atimers, sorted by expiration time.  The timer that
  44    will become ripe next is always at the front of this list.  */
  45
  46 static struct atimer *atimers;
  47
  48 /* Non-zero means alarm_signal_handler has found ripe timers but
  49    interrupt_input_blocked was non-zero.  In this case, timer
  50    functions are not called until the next UNBLOCK_INPUT because timer
  51    functions are expected to call X, and X cannot be assumed to be
  52    reentrant.  */
  53
  54 int pending_atimers;
  55
  56 /* Block/unblock SIGALRM.  */
  57
  58 #define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
  59 #define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
  60
  61 /* Function prototypes.  */
  62
  63 static void set_alarm (void);
  64 static void schedule_atimer (struct atimer *);
  65 static struct atimer *append_atimer_lists (struct atimer *,
  66                                            struct atimer *);
  67 static void alarm_signal_handler (int signo);
  68
  69
  70 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  71    ripe.  FN is the function to call when the timer fires.
  72    CLIENT_DATA is stored in the client_data member of the atimer
  73    structure returned and so made available to FN when it is called.
  74
  75    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  76    timer fires.
  77
  78    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  79    future.
  80
  81    In both cases, the timer is automatically freed after it has fired.
  82
  83    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  84
  85    Value is a pointer to the atimer started.  It can be used in calls
  86    to cancel_atimer; don't free it yourself.  */
  87
  88 struct atimer *
  89 start_atimer (enum atimer_type type, EMACS_TIME timestamp, atimer_callback fn,
  90               void *client_data)
  91 {
  92   struct atimer *t;
  93
  94   /* Round TIME up to the next full second if we don't have
  95      itimers.  */
  96 #ifndef HAVE_SETITIMER
  97   if (EMACS_USECS (timestamp) != 0)
  98     {
  99       EMACS_SET_USECS (timestamp, 0);
 100       EMACS_SET_SECS (timestamp, EMACS_SECS (timestamp) + 1);
 101     }
 102 #endif /* not HAVE_SETITIMER */
 103
 104   /* Get an atimer structure from the free-list, or allocate
 105      a new one.  */
 106   if (free_atimers)
 107     {
 108       t = free_atimers;
 109       free_atimers = t->next;
 110     }
 111   else
 112     t = (struct atimer *) xmalloc (sizeof *t);
 113
 114   /* Fill the atimer structure.  */
 115   memset (t, 0, sizeof *t);
 116   t->type = type;
 117   t->fn = fn;
 118   t->client_data = client_data;
 119
 120   BLOCK_ATIMERS;
 121
 122   /* Compute the timer's expiration time.  */
 123   switch (type)
 124     {
 125     case ATIMER_ABSOLUTE:
 126       t->expiration = timestamp;
 127       break;
 128
 129     case ATIMER_RELATIVE:
 130       EMACS_GET_TIME (t->expiration);
 131       EMACS_ADD_TIME (t->expiration, t->expiration, timestamp);
 132       break;
 133
 134     case ATIMER_CONTINUOUS:
 135       EMACS_GET_TIME (t->expiration);
 136       EMACS_ADD_TIME (t->expiration, t->expiration, timestamp);
 137       t->interval = timestamp;
 138       break;
 139     }
 140
 141   /* Insert the timer in the list of active atimers.  */
 142   schedule_atimer (t);
 143   UNBLOCK_ATIMERS;
 144
 145   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 146   set_alarm ();
 147
 148   return t;
 149 }
 150
 151
 152 /* Cancel and free atimer TIMER.  */
 153
 154 void
 155 cancel_atimer (struct atimer *timer)
 156 {
 157   int i;
 158
 159   BLOCK_ATIMERS;
 160
 161   for (i = 0; i < 2; ++i)
 162     {
 163       struct atimer *t, *prev;
 164       struct atimer **list = i ? &stopped_atimers : &atimers;
 165
 166       /* See if TIMER is active or stopped.  */
 167       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 168         ;
 169
 170       /* If it is, take it off its list, and put in on the free-list.
 171          We don't bother to arrange for setting a different alarm time,
 172          since a too early one doesn't hurt.  */
 173       if (t)
 174         {
 175           if (prev)
 176             prev->next = t->next;
 177           else
 178             *list = t->next;
 179
 180           t->next = free_atimers;
 181           free_atimers = t;
 182           break;
 183         }
 184     }
 185
 186   UNBLOCK_ATIMERS;
 187 }
 188
 189
 190 /* Append two lists of atimers LIST_1 and LIST_2 and return the
 191    result list.  */
 192
 193 static struct atimer *
 194 append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 195 {
 196   if (list_1 == NULL)
 197     return list_2;
 198   else if (list_2 == NULL)
 199     return list_1;
 200   else
 201     {
 202       struct atimer *p;
 203
 204       for (p = list_1; p->next; p = p->next)
 205         ;
 206       p->next = list_2;
 207       return list_1;
 208     }
 209 }
 210
 211
 212 /* Stop all timers except timer T.  T null means stop all timers.  */
 213
 214 void
 215 stop_other_atimers (struct atimer *t)
 216 {
 217   BLOCK_ATIMERS;
 218
 219   if (t)
 220     {
 221       struct atimer *p, *prev;
 222
 223       /* See if T is active.  */
 224       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 225         ;
 226
 227       if (p == t)
 228         {
 229           if (prev)
 230             prev->next = t->next;
 231           else
 232             atimers = t->next;
 233           t->next = NULL;
 234         }
 235       else
 236         /* T is not active.  Let's handle this like T == 0.  */
 237         t = NULL;
 238     }
 239
 240   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 241   atimers = t;
 242   UNBLOCK_ATIMERS;
 243 }
 244
 245
 246 /* Run all timers again, if some have been stopped with a call to
 247    stop_other_atimers.  */
 248
 249 static void
 250 run_all_atimers (void)
 251 {
 252   if (stopped_atimers)
 253     {
 254       struct atimer *t = atimers;
 255       struct atimer *next;
 256
 257       BLOCK_ATIMERS;
 258       atimers = stopped_atimers;
 259       stopped_atimers = NULL;
 260
 261       while (t)
 262         {
 263           next = t->next;
 264           schedule_atimer (t);
 265           t = next;
 266         }
 267
 268       UNBLOCK_ATIMERS;
 269     }
 270 }
 271
 272
 273 /* A version of run_all_atimers suitable for a record_unwind_protect.  */
 274
 275 Lisp_Object
 276 unwind_stop_other_atimers (Lisp_Object dummy)
 277 {
 278   run_all_atimers ();
 279   return Qnil;
 280 }
 281
 282
 283 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 284
 285 static void
 286 set_alarm (void)
 287 {
 288   if (atimers)
 289     {
 290       EMACS_TIME now, timestamp;
 291 #ifdef HAVE_SETITIMER
 292       struct itimerval it;
 293 #endif
 294
 295       /* Determine s/us till the next timer is ripe.  */
 296       EMACS_GET_TIME (now);
 297       EMACS_SUB_TIME (timestamp, atimers->expiration, now);
 298
 299 #ifdef HAVE_SETITIMER
 300       /* Don't set the interval to 0; this disables the timer.  */
 301       if (EMACS_TIME_LE (atimers->expiration, now))
 302         {
 303           EMACS_SET_SECS (timestamp, 0);
 304           EMACS_SET_USECS (timestamp, 1000);
 305         }
 306
 307       memset (&it, 0, sizeof it);
 308       it.it_value = timestamp;
 309       setitimer (ITIMER_REAL, &it, 0);
 310 #else /* not HAVE_SETITIMER */
 311       alarm (max (EMACS_SECS (timestamp), 1));
 312 #endif /* not HAVE_SETITIMER */
 313     }
 314 }
 315
 316
 317 /* Insert timer T into the list of active atimers `atimers', keeping
 318    the list sorted by expiration time.  T must not be in this list
 319    already.  */
 320
 321 static void
 322 schedule_atimer (struct atimer *t)
 323 {
 324   struct atimer *a = atimers, *prev = NULL;
 325
 326   /* Look for the first atimer that is ripe after T.  */
 327   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 328     prev = a, a = a->next;
 329
 330   /* Insert T in front of the atimer found, if any.  */
 331   if (prev)
 332     prev->next = t;
 333   else
 334     atimers = t;
 335
 336   t->next = a;
 337 }
 338
 339 static void
 340 run_timers (void)
 341 {
 342   EMACS_TIME now;
 343
 344   EMACS_GET_TIME (now);
 345
 346   while (atimers
 347          && (pending_atimers = interrupt_input_blocked) == 0
 348          && EMACS_TIME_LE (atimers->expiration, now))
 349     {
 350       struct atimer *t;
 351
 352       t = atimers;
 353       atimers = atimers->next;
 354       t->fn (t);
 355
 356       if (t->type == ATIMER_CONTINUOUS)
 357         {
 358           EMACS_ADD_TIME (t->expiration, now, t->interval);
 359           schedule_atimer (t);
 360         }
 361       else
 362         {
 363           t->next = free_atimers;
 364           free_atimers = t;
 365         }
 366
 367       EMACS_GET_TIME (now);
 368     }
 369
 370   if (! atimers)
 371     pending_atimers = 0;
 372
 373 #ifdef SYNC_INPUT
 374   if (pending_atimers)
 375     pending_signals = 1;
 376   else
 377     {
 378       pending_signals = interrupt_input_pending;
 379       set_alarm ();
 380     }
 381 #else
 382   if (! pending_atimers)
 383     set_alarm ();
 384 #endif
 385 }
 386
 387
 388 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 389    SIGALRM.  */
 390
 391 void
 392 alarm_signal_handler (int signo)
 393 {
 394 #ifndef SYNC_INPUT
 395   SIGNAL_THREAD_CHECK (signo);
 396 #endif
 397
 398   pending_atimers = 1;
 399 #ifdef SYNC_INPUT
 400   pending_signals = 1;
 401 #else
 402   run_timers ();
 403 #endif
 404 }
 405
 406
 407 /* Call alarm_signal_handler for pending timers.  */
 408
 409 void
 410 do_pending_atimers (void)
 411 {
 412   if (pending_atimers)
 413     {
 414       BLOCK_ATIMERS;
 415       run_timers ();
 416       UNBLOCK_ATIMERS;
 417     }
 418 }
 419
 420
 421 /* Turn alarms on/off.  This seems to be temporarily necessary on
 422    some systems like HPUX (see process.c).  */
 423
 424 void
 425 turn_on_atimers (int on)
 426 {
 427   if (on)
 428     {
 429       signal (SIGALRM, alarm_signal_handler);
 430       set_alarm ();
 431     }
 432   else
 433     alarm (0);
 434 }
 435
 436
 437 void
 438 init_atimer (void)
 439 {
 440   free_atimers = stopped_atimers = atimers = NULL;
 441   pending_atimers = 0;
 442   /* pending_signals is initialized in init_keyboard.*/
 443   signal (SIGALRM, alarm_signal_handler);
 444 }