src/atimer.c

   1 /* Asynchronous timers.
   2    Copyright (C) 2000-2013 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 <stdio.h>
  21
  22 #include "lisp.h"
  23 #include "syssignal.h"
  24 #include "systime.h"
  25 #include "blockinput.h"
  26 #include "atimer.h"
  27 #include <unistd.h>
  28
  29 /* Free-list of atimer structures.  */
  30
  31 static struct atimer *free_atimers;
  32
  33 /* List of currently not running timers due to a call to
  34    lock_atimer.  */
  35
  36 static struct atimer *stopped_atimers;
  37
  38 /* List of active atimers, sorted by expiration time.  The timer that
  39    will become ripe next is always at the front of this list.  */
  40
  41 static struct atimer *atimers;
  42
  43 /* The alarm timer and whether it was properly initialized, if
  44    POSIX timers are available.  */
  45 #ifdef HAVE_ITIMERSPEC
  46 static timer_t alarm_timer;
  47 static bool alarm_timer_ok;
  48 #endif
  49
  50 /* Block/unblock SIGALRM.  */
  51
  52 static void
  53 sigmask_atimers (int how)
  54 {
  55   sigset_t blocked;
  56   sigemptyset (&blocked);
  57   sigaddset (&blocked, SIGALRM);
  58   pthread_sigmask (how, &blocked, 0);
  59 }
  60 static void
  61 block_atimers (void)
  62 {
  63   sigmask_atimers (SIG_BLOCK);
  64 }
  65 static void
  66 unblock_atimers (void)
  67 {
  68   sigmask_atimers (SIG_UNBLOCK);
  69 }
  70
  71 /* Function prototypes.  */
  72
  73 static void set_alarm (void);
  74 static void schedule_atimer (struct atimer *);
  75 static struct atimer *append_atimer_lists (struct atimer *,
  76                                            struct atimer *);
  77
  78 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  79    ripe.  FN is the function to call when the timer fires.
  80    CLIENT_DATA is stored in the client_data member of the atimer
  81    structure returned and so made available to FN when it is called.
  82
  83    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  84    timer fires.
  85
  86    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  87    future.
  88
  89    In both cases, the timer is automatically freed after it has fired.
  90
  91    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  92
  93    Value is a pointer to the atimer started.  It can be used in calls
  94    to cancel_atimer; don't free it yourself.  */
  95
  96 struct atimer *
  97 start_atimer (enum atimer_type type, EMACS_TIME timestamp, 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_NSECS (timestamp) != 0
 106       && EMACS_SECS (timestamp) < TYPE_MAXIMUM (time_t))
 107     timestamp = make_emacs_time (EMACS_SECS (timestamp) + 1, 0);
 108 #endif /* not HAVE_SETITIMER */
 109
 110   /* Get an atimer structure from the free-list, or allocate
 111      a new one.  */
 112   if (free_atimers)
 113     {
 114       t = free_atimers;
 115       free_atimers = t->next;
 116     }
 117   else
 118     t = xmalloc (sizeof *t);
 119
 120   /* Fill the atimer structure.  */
 121   memset (t, 0, sizeof *t);
 122   t->type = type;
 123   t->fn = fn;
 124   t->client_data = client_data;
 125
 126   block_atimers ();
 127
 128   /* Compute the timer's expiration time.  */
 129   switch (type)
 130     {
 131     case ATIMER_ABSOLUTE:
 132       t->expiration = timestamp;
 133       break;
 134
 135     case ATIMER_RELATIVE:
 136       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 137       break;
 138
 139     case ATIMER_CONTINUOUS:
 140       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 141       t->interval = timestamp;
 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 LIST_1 and LIST_2 and return the
 195    result list.  */
 196
 197 static struct atimer *
 198 append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 199 {
 200   if (list_1 == NULL)
 201     return list_2;
 202   else if (list_2 == NULL)
 203     return list_1;
 204   else
 205     {
 206       struct atimer *p;
 207
 208       for (p = list_1; p->next; p = p->next)
 209         ;
 210       p->next = list_2;
 211       return list_1;
 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 static 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_atimers 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 #ifdef HAVE_SETITIMER
 295       struct itimerval it;
 296 #endif
 297       EMACS_TIME now, interval;
 298
 299 #ifdef HAVE_ITIMERSPEC
 300       if (alarm_timer_ok)
 301         {
 302           struct itimerspec ispec;
 303           ispec.it_value = atimers->expiration;
 304           ispec.it_interval.tv_sec = ispec.it_interval.tv_nsec = 0;
 305           if (timer_settime (alarm_timer, 0, &ispec, 0) == 0)
 306             return;
 307         }
 308 #endif
 309
 310       /* Determine interval till the next timer is ripe.
 311          Don't set the interval to 0; this disables the timer.  */
 312       now = current_emacs_time ();
 313       interval = (EMACS_TIME_LE (atimers->expiration, now)
 314                   ? make_emacs_time (0, 1000 * 1000)
 315                   : sub_emacs_time (atimers->expiration, now));
 316
 317 #ifdef HAVE_SETITIMER
 318
 319       memset (&it, 0, sizeof it);
 320       it.it_value = make_timeval (interval);
 321       setitimer (ITIMER_REAL, &it, 0);
 322 #else /* not HAVE_SETITIMER */
 323       alarm (max (EMACS_SECS (interval), 1));
 324 #endif /* not HAVE_SETITIMER */
 325     }
 326 }
 327
 328
 329 /* Insert timer T into the list of active atimers `atimers', keeping
 330    the list sorted by expiration time.  T must not be in this list
 331    already.  */
 332
 333 static void
 334 schedule_atimer (struct atimer *t)
 335 {
 336   struct atimer *a = atimers, *prev = NULL;
 337
 338   /* Look for the first atimer that is ripe after T.  */
 339   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 340     prev = a, a = a->next;
 341
 342   /* Insert T in front of the atimer found, if any.  */
 343   if (prev)
 344     prev->next = t;
 345   else
 346     atimers = t;
 347
 348   t->next = a;
 349 }
 350
 351 static void
 352 run_timers (void)
 353 {
 354   EMACS_TIME now = current_emacs_time ();
 355
 356   while (atimers && EMACS_TIME_LE (atimers->expiration, now))
 357     {
 358       struct atimer *t = atimers;
 359       atimers = atimers->next;
 360       t->fn (t);
 361
 362       if (t->type == ATIMER_CONTINUOUS)
 363         {
 364           t->expiration = add_emacs_time (now, t->interval);
 365           schedule_atimer (t);
 366         }
 367       else
 368         {
 369           t->next = free_atimers;
 370           free_atimers = t;
 371         }
 372     }
 373
 374   set_alarm ();
 375 }
 376
 377
 378 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 379    SIGALRM.  */
 380
 381 static void
 382 handle_alarm_signal (int sig)
 383 {
 384   pending_signals = 1;
 385 }
 386
 387
 388 /* Do pending timers.  */
 389
 390 void
 391 do_pending_atimers (void)
 392 {
 393   if (atimers)
 394     {
 395       block_atimers ();
 396       run_timers ();
 397       unblock_atimers ();
 398     }
 399 }
 400
 401
 402 /* Turn alarms on/off.  This seems to be temporarily necessary on
 403    some systems like HPUX (see process.c).  */
 404
 405 void
 406 turn_on_atimers (bool on)
 407 {
 408   if (on)
 409     set_alarm ();
 410   else
 411     alarm (0);
 412 }
 413
 414
 415 void
 416 init_atimer (void)
 417 {
 418   struct sigaction action;
 419 #ifdef HAVE_ITIMERSPEC
 420   struct sigevent sigev;
 421   sigev.sigev_notify = SIGEV_SIGNAL;
 422   sigev.sigev_signo = SIGALRM;
 423   sigev.sigev_value.sival_ptr = &alarm_timer;
 424   alarm_timer_ok = timer_create (CLOCK_REALTIME, &sigev, &alarm_timer) == 0;
 425 #endif
 426   free_atimers = stopped_atimers = atimers = NULL;
 427   /* pending_signals is initialized in init_keyboard.*/
 428   emacs_sigaction_init (&action, handle_alarm_signal);
 429   sigaction (SIGALRM, &action, 0);
 430 }