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 <stdio.h>
  21 #include <setjmp.h>
  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 /* Non-zero means alarm signal handler has found ripe timers but
  44    interrupt_input_blocked was non-zero.  In this case, timer
  45    functions are not called until the next UNBLOCK_INPUT because timer
  46    functions are expected to call X, and X cannot be assumed to be
  47    reentrant.  */
  48
  49 int pending_atimers;
  50
  51 /* Block/unblock SIGALRM.  */
  52
  53 static void
  54 sigmask_atimers (int how)
  55 {
  56   sigset_t blocked;
  57   sigemptyset (&blocked);
  58   sigaddset (&blocked, SIGALRM);
  59   pthread_sigmask (how, &blocked, 0);
  60 }
  61 static void
  62 block_atimers (void)
  63 {
  64   sigmask_atimers (SIG_BLOCK);
  65 }
  66 static void
  67 unblock_atimers (void)
  68 {
  69   sigmask_atimers (SIG_UNBLOCK);
  70 }
  71
  72 /* Function prototypes.  */
  73
  74 static void set_alarm (void);
  75 static void schedule_atimer (struct atimer *);
  76 static struct atimer *append_atimer_lists (struct atimer *,
  77                                            struct atimer *);
  78
  79 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  80    ripe.  FN is the function to call when the timer fires.
  81    CLIENT_DATA is stored in the client_data member of the atimer
  82    structure returned and so made available to FN when it is called.
  83
  84    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  85    timer fires.
  86
  87    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  88    future.
  89
  90    In both cases, the timer is automatically freed after it has fired.
  91
  92    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  93
  94    Value is a pointer to the atimer started.  It can be used in calls
  95    to cancel_atimer; don't free it yourself.  */
  96
  97 struct atimer *
  98 start_atimer (enum atimer_type type, EMACS_TIME timestamp, atimer_callback fn,
  99               void *client_data)
 100 {
 101   struct atimer *t;
 102
 103   /* Round TIME up to the next full second if we don't have
 104      itimers.  */
 105 #ifndef HAVE_SETITIMER
 106   if (EMACS_NSECS (timestamp) != 0
 107       && EMACS_SECS (timestamp) < TYPE_MAXIMUM (time_t))
 108     timestamp = make_emacs_time (EMACS_SECS (timestamp) + 1, 0);
 109 #endif /* not HAVE_SETITIMER */
 110
 111   /* Get an atimer structure from the free-list, or allocate
 112      a new one.  */
 113   if (free_atimers)
 114     {
 115       t = free_atimers;
 116       free_atimers = t->next;
 117     }
 118   else
 119     t = xmalloc (sizeof *t);
 120
 121   /* Fill the atimer structure.  */
 122   memset (t, 0, sizeof *t);
 123   t->type = type;
 124   t->fn = fn;
 125   t->client_data = client_data;
 126
 127   block_atimers ();
 128
 129   /* Compute the timer's expiration time.  */
 130   switch (type)
 131     {
 132     case ATIMER_ABSOLUTE:
 133       t->expiration = timestamp;
 134       break;
 135
 136     case ATIMER_RELATIVE:
 137       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 138       break;
 139
 140     case ATIMER_CONTINUOUS:
 141       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 142       t->interval = timestamp;
 143       break;
 144     }
 145
 146   /* Insert the timer in the list of active atimers.  */
 147   schedule_atimer (t);
 148   unblock_atimers ();
 149
 150   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 151   set_alarm ();
 152
 153   return t;
 154 }
 155
 156
 157 /* Cancel and free atimer TIMER.  */
 158
 159 void
 160 cancel_atimer (struct atimer *timer)
 161 {
 162   int i;
 163
 164   block_atimers ();
 165
 166   for (i = 0; i < 2; ++i)
 167     {
 168       struct atimer *t, *prev;
 169       struct atimer **list = i ? &stopped_atimers : &atimers;
 170
 171       /* See if TIMER is active or stopped.  */
 172       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 173         ;
 174
 175       /* If it is, take it off its list, and put in on the free-list.
 176          We don't bother to arrange for setting a different alarm time,
 177          since a too early one doesn't hurt.  */
 178       if (t)
 179         {
 180           if (prev)
 181             prev->next = t->next;
 182           else
 183             *list = t->next;
 184
 185           t->next = free_atimers;
 186           free_atimers = t;
 187           break;
 188         }
 189     }
 190
 191   unblock_atimers ();
 192 }
 193
 194
 195 /* Append two lists of atimers LIST_1 and LIST_2 and return the
 196    result list.  */
 197
 198 static struct atimer *
 199 append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 200 {
 201   if (list_1 == NULL)
 202     return list_2;
 203   else if (list_2 == NULL)
 204     return list_1;
 205   else
 206     {
 207       struct atimer *p;
 208
 209       for (p = list_1; p->next; p = p->next)
 210         ;
 211       p->next = list_2;
 212       return list_1;
 213     }
 214 }
 215
 216
 217 /* Stop all timers except timer T.  T null means stop all timers.  */
 218
 219 void
 220 stop_other_atimers (struct atimer *t)
 221 {
 222   block_atimers ();
 223
 224   if (t)
 225     {
 226       struct atimer *p, *prev;
 227
 228       /* See if T is active.  */
 229       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 230         ;
 231
 232       if (p == t)
 233         {
 234           if (prev)
 235             prev->next = t->next;
 236           else
 237             atimers = t->next;
 238           t->next = NULL;
 239         }
 240       else
 241         /* T is not active.  Let's handle this like T == 0.  */
 242         t = NULL;
 243     }
 244
 245   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 246   atimers = t;
 247   unblock_atimers ();
 248 }
 249
 250
 251 /* Run all timers again, if some have been stopped with a call to
 252    stop_other_atimers.  */
 253
 254 static void
 255 run_all_atimers (void)
 256 {
 257   if (stopped_atimers)
 258     {
 259       struct atimer *t = atimers;
 260       struct atimer *next;
 261
 262       block_atimers ();
 263       atimers = stopped_atimers;
 264       stopped_atimers = NULL;
 265
 266       while (t)
 267         {
 268           next = t->next;
 269           schedule_atimer (t);
 270           t = next;
 271         }
 272
 273       unblock_atimers ();
 274     }
 275 }
 276
 277
 278 /* A version of run_all_atimers suitable for a record_unwind_protect.  */
 279
 280 Lisp_Object
 281 unwind_stop_other_atimers (Lisp_Object dummy)
 282 {
 283   run_all_atimers ();
 284   return Qnil;
 285 }
 286
 287
 288 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 289
 290 static void
 291 set_alarm (void)
 292 {
 293   if (atimers)
 294     {
 295 #ifdef HAVE_SETITIMER
 296       struct itimerval it;
 297 #endif
 298
 299       /* Determine s/us till the next timer is ripe.  */
 300       EMACS_TIME now = current_emacs_time ();
 301
 302       /* Don't set the interval to 0; this disables the timer.  */
 303       EMACS_TIME interval = (EMACS_TIME_LE (atimers->expiration, now)
 304                              ? make_emacs_time (0, 1000 * 1000)
 305                              : sub_emacs_time (atimers->expiration, now));
 306
 307 #ifdef HAVE_SETITIMER
 308
 309       memset (&it, 0, sizeof it);
 310       it.it_value = make_timeval (interval);
 311       setitimer (ITIMER_REAL, &it, 0);
 312 #else /* not HAVE_SETITIMER */
 313       alarm (max (EMACS_SECS (interval), 1));
 314 #endif /* not HAVE_SETITIMER */
 315     }
 316 }
 317
 318
 319 /* Insert timer T into the list of active atimers `atimers', keeping
 320    the list sorted by expiration time.  T must not be in this list
 321    already.  */
 322
 323 static void
 324 schedule_atimer (struct atimer *t)
 325 {
 326   struct atimer *a = atimers, *prev = NULL;
 327
 328   /* Look for the first atimer that is ripe after T.  */
 329   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 330     prev = a, a = a->next;
 331
 332   /* Insert T in front of the atimer found, if any.  */
 333   if (prev)
 334     prev->next = t;
 335   else
 336     atimers = t;
 337
 338   t->next = a;
 339 }
 340
 341 static void
 342 run_timers (void)
 343 {
 344   EMACS_TIME now;
 345
 346   while (atimers
 347          && (pending_atimers = interrupt_input_blocked) == 0
 348          && (now = current_emacs_time (),
 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           t->expiration = add_emacs_time (now, t->interval);
 360           schedule_atimer (t);
 361         }
 362       else
 363         {
 364           t->next = free_atimers;
 365           free_atimers = t;
 366         }
 367     }
 368
 369   if (! atimers)
 370     pending_atimers = 0;
 371
 372 #ifdef SYNC_INPUT
 373   if (pending_atimers)
 374     pending_signals = 1;
 375   else
 376     {
 377       pending_signals = interrupt_input_pending;
 378       set_alarm ();
 379     }
 380 #else
 381   if (! pending_atimers)
 382     set_alarm ();
 383 #endif
 384 }
 385
 386
 387 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 388    SIGALRM.  */
 389
 390 static void
 391 handle_alarm_signal (int sig)
 392 {
 393   pending_atimers = 1;
 394 #ifdef SYNC_INPUT
 395   pending_signals = 1;
 396 #else
 397   run_timers ();
 398 #endif
 399 }
 400
 401 static void
 402 deliver_alarm_signal (int sig)
 403 {
 404   handle_on_main_thread (sig, handle_alarm_signal);
 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 (bool on)
 427 {
 428   if (on)
 429     {
 430       struct sigaction action;
 431       emacs_sigaction_init (&action, deliver_alarm_signal);
 432       sigaction (SIGALRM, &action, 0);
 433       set_alarm ();
 434     }
 435   else
 436     alarm (0);
 437 }
 438
 439
 440 void
 441 init_atimer (void)
 442 {
 443   struct sigaction action;
 444   free_atimers = stopped_atimers = atimers = NULL;
 445   pending_atimers = 0;
 446   /* pending_signals is initialized in init_keyboard.*/
 447   emacs_sigaction_init (&action, deliver_alarm_signal);
 448   sigaction (SIGALRM, &action, 0);
 449 }