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 #include <sys/time.h>
  30
  31 /* Free-list of atimer structures.  */
  32
  33 static struct atimer *free_atimers;
  34
  35 /* List of currently not running timers due to a call to
  36    lock_atimer.  */
  37
  38 static struct atimer *stopped_atimers;
  39
  40 /* List of active atimers, sorted by expiration time.  The timer that
  41    will become ripe next is always at the front of this list.  */
  42
  43 static struct atimer *atimers;
  44
  45 /* Non-zero means alarm_signal_handler has found ripe timers but
  46    interrupt_input_blocked was non-zero.  In this case, timer
  47    functions are not called until the next UNBLOCK_INPUT because timer
  48    functions are expected to call X, and X cannot be assumed to be
  49    reentrant.  */
  50
  51 int pending_atimers;
  52
  53 /* Block/unblock SIGALRM.  */
  54
  55 #define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
  56 #define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
  57
  58 /* Function prototypes.  */
  59
  60 static void set_alarm (void);
  61 static void schedule_atimer (struct atimer *);
  62 static struct atimer *append_atimer_lists (struct atimer *,
  63                                            struct atimer *);
  64 static void alarm_signal_handler (int signo);
  65
  66
  67 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  68    ripe.  FN is the function to call when the timer fires.
  69    CLIENT_DATA is stored in the client_data member of the atimer
  70    structure returned and so made available to FN when it is called.
  71
  72    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  73    timer fires.
  74
  75    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  76    future.
  77
  78    In both cases, the timer is automatically freed after it has fired.
  79
  80    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  81
  82    Value is a pointer to the atimer started.  It can be used in calls
  83    to cancel_atimer; don't free it yourself.  */
  84
  85 struct atimer *
  86 start_atimer (enum atimer_type type, EMACS_TIME timestamp, atimer_callback fn,
  87               void *client_data)
  88 {
  89   struct atimer *t;
  90
  91   /* Round TIME up to the next full second if we don't have
  92      itimers.  */
  93 #ifndef HAVE_SETITIMER
  94   if (EMACS_NSECS (timestamp) != 0
  95       && EMACS_SECS (timestamp) < TYPE_MAXIMUM (time_t))
  96     {
  97       EMACS_SET_USECS (timestamp, 0);
  98       EMACS_SET_SECS (timestamp, EMACS_SECS (timestamp) + 1);
  99     }
 100 #endif /* not HAVE_SETITIMER */
 101
 102   /* Get an atimer structure from the free-list, or allocate
 103      a new one.  */
 104   if (free_atimers)
 105     {
 106       t = free_atimers;
 107       free_atimers = t->next;
 108     }
 109   else
 110     t = (struct atimer *) xmalloc (sizeof *t);
 111
 112   /* Fill the atimer structure.  */
 113   memset (t, 0, sizeof *t);
 114   t->type = type;
 115   t->fn = fn;
 116   t->client_data = client_data;
 117
 118   BLOCK_ATIMERS;
 119
 120   /* Compute the timer's expiration time.  */
 121   switch (type)
 122     {
 123     case ATIMER_ABSOLUTE:
 124       t->expiration = timestamp;
 125       break;
 126
 127     case ATIMER_RELATIVE:
 128       EMACS_GET_TIME (t->expiration);
 129       EMACS_ADD_TIME (t->expiration, t->expiration, timestamp);
 130       break;
 131
 132     case ATIMER_CONTINUOUS:
 133       EMACS_GET_TIME (t->expiration);
 134       EMACS_ADD_TIME (t->expiration, t->expiration, timestamp);
 135       t->interval = timestamp;
 136       break;
 137     }
 138
 139   /* Insert the timer in the list of active atimers.  */
 140   schedule_atimer (t);
 141   UNBLOCK_ATIMERS;
 142
 143   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 144   set_alarm ();
 145
 146   return t;
 147 }
 148
 149
 150 /* Cancel and free atimer TIMER.  */
 151
 152 void
 153 cancel_atimer (struct atimer *timer)
 154 {
 155   int i;
 156
 157   BLOCK_ATIMERS;
 158
 159   for (i = 0; i < 2; ++i)
 160     {
 161       struct atimer *t, *prev;
 162       struct atimer **list = i ? &stopped_atimers : &atimers;
 163
 164       /* See if TIMER is active or stopped.  */
 165       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 166         ;
 167
 168       /* If it is, take it off its list, and put in on the free-list.
 169          We don't bother to arrange for setting a different alarm time,
 170          since a too early one doesn't hurt.  */
 171       if (t)
 172         {
 173           if (prev)
 174             prev->next = t->next;
 175           else
 176             *list = t->next;
 177
 178           t->next = free_atimers;
 179           free_atimers = t;
 180           break;
 181         }
 182     }
 183
 184   UNBLOCK_ATIMERS;
 185 }
 186
 187
 188 /* Append two lists of atimers LIST_1 and LIST_2 and return the
 189    result list.  */
 190
 191 static struct atimer *
 192 append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 193 {
 194   if (list_1 == NULL)
 195     return list_2;
 196   else if (list_2 == NULL)
 197     return list_1;
 198   else
 199     {
 200       struct atimer *p;
 201
 202       for (p = list_1; p->next; p = p->next)
 203         ;
 204       p->next = list_2;
 205       return list_1;
 206     }
 207 }
 208
 209
 210 /* Stop all timers except timer T.  T null means stop all timers.  */
 211
 212 void
 213 stop_other_atimers (struct atimer *t)
 214 {
 215   BLOCK_ATIMERS;
 216
 217   if (t)
 218     {
 219       struct atimer *p, *prev;
 220
 221       /* See if T is active.  */
 222       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 223         ;
 224
 225       if (p == t)
 226         {
 227           if (prev)
 228             prev->next = t->next;
 229           else
 230             atimers = t->next;
 231           t->next = NULL;
 232         }
 233       else
 234         /* T is not active.  Let's handle this like T == 0.  */
 235         t = NULL;
 236     }
 237
 238   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 239   atimers = t;
 240   UNBLOCK_ATIMERS;
 241 }
 242
 243
 244 /* Run all timers again, if some have been stopped with a call to
 245    stop_other_atimers.  */
 246
 247 static void
 248 run_all_atimers (void)
 249 {
 250   if (stopped_atimers)
 251     {
 252       struct atimer *t = atimers;
 253       struct atimer *next;
 254
 255       BLOCK_ATIMERS;
 256       atimers = stopped_atimers;
 257       stopped_atimers = NULL;
 258
 259       while (t)
 260         {
 261           next = t->next;
 262           schedule_atimer (t);
 263           t = next;
 264         }
 265
 266       UNBLOCK_ATIMERS;
 267     }
 268 }
 269
 270
 271 /* A version of run_all_atimers suitable for a record_unwind_protect.  */
 272
 273 Lisp_Object
 274 unwind_stop_other_atimers (Lisp_Object dummy)
 275 {
 276   run_all_atimers ();
 277   return Qnil;
 278 }
 279
 280
 281 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 282
 283 static void
 284 set_alarm (void)
 285 {
 286   if (atimers)
 287     {
 288       EMACS_TIME now, timestamp;
 289 #ifdef HAVE_SETITIMER
 290       struct itimerval it;
 291 #endif
 292
 293       /* Determine s/us till the next timer is ripe.  */
 294       EMACS_GET_TIME (now);
 295
 296       /* Don't set the interval to 0; this disables the timer.  */
 297       if (EMACS_TIME_LE (atimers->expiration, now))
 298         {
 299           EMACS_SET_SECS (timestamp, 0);
 300           EMACS_SET_USECS (timestamp, 1000);
 301         }
 302       else
 303         EMACS_SUB_TIME (timestamp, atimers->expiration, now);
 304
 305
 306 #ifdef HAVE_SETITIMER
 307
 308       memset (&it, 0, sizeof it);
 309       it.it_value = make_timeval (timestamp);
 310       setitimer (ITIMER_REAL, &it, 0);
 311 #else /* not HAVE_SETITIMER */
 312       alarm (max (EMACS_SECS (timestamp), 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   while (atimers
 346          && (pending_atimers = interrupt_input_blocked) == 0
 347          && (EMACS_GET_TIME (now),
 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
 368   if (! atimers)
 369     pending_atimers = 0;
 370
 371 #ifdef SYNC_INPUT
 372   if (pending_atimers)
 373     pending_signals = 1;
 374   else
 375     {
 376       pending_signals = interrupt_input_pending;
 377       set_alarm ();
 378     }
 379 #else
 380   if (! pending_atimers)
 381     set_alarm ();
 382 #endif
 383 }
 384
 385
 386 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 387    SIGALRM.  */
 388
 389 void
 390 alarm_signal_handler (int signo)
 391 {
 392 #ifndef SYNC_INPUT
 393   SIGNAL_THREAD_CHECK (signo);
 394 #endif
 395
 396   pending_atimers = 1;
 397 #ifdef SYNC_INPUT
 398   pending_signals = 1;
 399 #else
 400   run_timers ();
 401 #endif
 402 }
 403
 404
 405 /* Call alarm_signal_handler for pending timers.  */
 406
 407 void
 408 do_pending_atimers (void)
 409 {
 410   if (pending_atimers)
 411     {
 412       BLOCK_ATIMERS;
 413       run_timers ();
 414       UNBLOCK_ATIMERS;
 415     }
 416 }
 417
 418
 419 /* Turn alarms on/off.  This seems to be temporarily necessary on
 420    some systems like HPUX (see process.c).  */
 421
 422 void
 423 turn_on_atimers (int on)
 424 {
 425   if (on)
 426     {
 427       signal (SIGALRM, alarm_signal_handler);
 428       set_alarm ();
 429     }
 430   else
 431     alarm (0);
 432 }
 433
 434
 435 void
 436 init_atimer (void)
 437 {
 438   free_atimers = stopped_atimers = atimers = NULL;
 439   pending_atimers = 0;
 440   /* pending_signals is initialized in init_keyboard.*/
 441   signal (SIGALRM, alarm_signal_handler);
 442 }