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
  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 /* Block/unblock SIGALRM.  */
  44
  45 static void
  46 sigmask_atimers (int how)
  47 {
  48   sigset_t blocked;
  49   sigemptyset (&blocked);
  50   sigaddset (&blocked, SIGALRM);
  51   pthread_sigmask (how, &blocked, 0);
  52 }
  53 static void
  54 block_atimers (void)
  55 {
  56   sigmask_atimers (SIG_BLOCK);
  57 }
  58 static void
  59 unblock_atimers (void)
  60 {
  61   sigmask_atimers (SIG_UNBLOCK);
  62 }
  63
  64 /* Function prototypes.  */
  65
  66 static void set_alarm (void);
  67 static void schedule_atimer (struct atimer *);
  68 static struct atimer *append_atimer_lists (struct atimer *,
  69                                            struct atimer *);
  70
  71 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  72    ripe.  FN is the function to call when the timer fires.
  73    CLIENT_DATA is stored in the client_data member of the atimer
  74    structure returned and so made available to FN when it is called.
  75
  76    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  77    timer fires.
  78
  79    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  80    future.
  81
  82    In both cases, the timer is automatically freed after it has fired.
  83
  84    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  85
  86    Value is a pointer to the atimer started.  It can be used in calls
  87    to cancel_atimer; don't free it yourself.  */
  88
  89 struct atimer *
  90 start_atimer (enum atimer_type type, EMACS_TIME timestamp, atimer_callback fn,
  91               void *client_data)
  92 {
  93   struct atimer *t;
  94
  95   /* Round TIME up to the next full second if we don't have
  96      itimers.  */
  97 #ifndef HAVE_SETITIMER
  98   if (EMACS_NSECS (timestamp) != 0
  99       && EMACS_SECS (timestamp) < TYPE_MAXIMUM (time_t))
 100     timestamp = make_emacs_time (EMACS_SECS (timestamp) + 1, 0);
 101 #endif /* not HAVE_SETITIMER */
 102
 103   /* Get an atimer structure from the free-list, or allocate
 104      a new one.  */
 105   if (free_atimers)
 106     {
 107       t = free_atimers;
 108       free_atimers = t->next;
 109     }
 110   else
 111     t = xmalloc (sizeof *t);
 112
 113   /* Fill the atimer structure.  */
 114   memset (t, 0, sizeof *t);
 115   t->type = type;
 116   t->fn = fn;
 117   t->client_data = client_data;
 118
 119   block_atimers ();
 120
 121   /* Compute the timer's expiration time.  */
 122   switch (type)
 123     {
 124     case ATIMER_ABSOLUTE:
 125       t->expiration = timestamp;
 126       break;
 127
 128     case ATIMER_RELATIVE:
 129       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 130       break;
 131
 132     case ATIMER_CONTINUOUS:
 133       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 134       t->interval = timestamp;
 135       break;
 136     }
 137
 138   /* Insert the timer in the list of active atimers.  */
 139   schedule_atimer (t);
 140   unblock_atimers ();
 141
 142   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 143   set_alarm ();
 144
 145   return t;
 146 }
 147
 148
 149 /* Cancel and free atimer TIMER.  */
 150
 151 void
 152 cancel_atimer (struct atimer *timer)
 153 {
 154   int i;
 155
 156   block_atimers ();
 157
 158   for (i = 0; i < 2; ++i)
 159     {
 160       struct atimer *t, *prev;
 161       struct atimer **list = i ? &stopped_atimers : &atimers;
 162
 163       /* See if TIMER is active or stopped.  */
 164       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 165         ;
 166
 167       /* If it is, take it off its list, and put in on the free-list.
 168          We don't bother to arrange for setting a different alarm time,
 169          since a too early one doesn't hurt.  */
 170       if (t)
 171         {
 172           if (prev)
 173             prev->next = t->next;
 174           else
 175             *list = t->next;
 176
 177           t->next = free_atimers;
 178           free_atimers = t;
 179           break;
 180         }
 181     }
 182
 183   unblock_atimers ();
 184 }
 185
 186
 187 /* Append two lists of atimers LIST_1 and LIST_2 and return the
 188    result list.  */
 189
 190 static struct atimer *
 191 append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 192 {
 193   if (list_1 == NULL)
 194     return list_2;
 195   else if (list_2 == NULL)
 196     return list_1;
 197   else
 198     {
 199       struct atimer *p;
 200
 201       for (p = list_1; p->next; p = p->next)
 202         ;
 203       p->next = list_2;
 204       return list_1;
 205     }
 206 }
 207
 208
 209 /* Stop all timers except timer T.  T null means stop all timers.  */
 210
 211 void
 212 stop_other_atimers (struct atimer *t)
 213 {
 214   block_atimers ();
 215
 216   if (t)
 217     {
 218       struct atimer *p, *prev;
 219
 220       /* See if T is active.  */
 221       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 222         ;
 223
 224       if (p == t)
 225         {
 226           if (prev)
 227             prev->next = t->next;
 228           else
 229             atimers = t->next;
 230           t->next = NULL;
 231         }
 232       else
 233         /* T is not active.  Let's handle this like T == 0.  */
 234         t = NULL;
 235     }
 236
 237   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 238   atimers = t;
 239   unblock_atimers ();
 240 }
 241
 242
 243 /* Run all timers again, if some have been stopped with a call to
 244    stop_other_atimers.  */
 245
 246 static void
 247 run_all_atimers (void)
 248 {
 249   if (stopped_atimers)
 250     {
 251       struct atimer *t = atimers;
 252       struct atimer *next;
 253
 254       block_atimers ();
 255       atimers = stopped_atimers;
 256       stopped_atimers = NULL;
 257
 258       while (t)
 259         {
 260           next = t->next;
 261           schedule_atimer (t);
 262           t = next;
 263         }
 264
 265       unblock_atimers ();
 266     }
 267 }
 268
 269
 270 /* A version of run_all_atimers suitable for a record_unwind_protect.  */
 271
 272 Lisp_Object
 273 unwind_stop_other_atimers (Lisp_Object dummy)
 274 {
 275   run_all_atimers ();
 276   return Qnil;
 277 }
 278
 279
 280 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 281
 282 static void
 283 set_alarm (void)
 284 {
 285   if (atimers)
 286     {
 287 #ifdef HAVE_SETITIMER
 288       struct itimerval it;
 289 #endif
 290
 291       /* Determine s/us till the next timer is ripe.  */
 292       EMACS_TIME now = current_emacs_time ();
 293
 294       /* Don't set the interval to 0; this disables the timer.  */
 295       EMACS_TIME interval = (EMACS_TIME_LE (atimers->expiration, now)
 296                              ? make_emacs_time (0, 1000 * 1000)
 297                              : sub_emacs_time (atimers->expiration, now));
 298
 299 #ifdef HAVE_SETITIMER
 300
 301       memset (&it, 0, sizeof it);
 302       it.it_value = make_timeval (interval);
 303       setitimer (ITIMER_REAL, &it, 0);
 304 #else /* not HAVE_SETITIMER */
 305       alarm (max (EMACS_SECS (interval), 1));
 306 #endif /* not HAVE_SETITIMER */
 307     }
 308 }
 309
 310
 311 /* Insert timer T into the list of active atimers `atimers', keeping
 312    the list sorted by expiration time.  T must not be in this list
 313    already.  */
 314
 315 static void
 316 schedule_atimer (struct atimer *t)
 317 {
 318   struct atimer *a = atimers, *prev = NULL;
 319
 320   /* Look for the first atimer that is ripe after T.  */
 321   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 322     prev = a, a = a->next;
 323
 324   /* Insert T in front of the atimer found, if any.  */
 325   if (prev)
 326     prev->next = t;
 327   else
 328     atimers = t;
 329
 330   t->next = a;
 331 }
 332
 333 static void
 334 run_timers (void)
 335 {
 336   EMACS_TIME now = current_emacs_time ();
 337
 338   while (atimers && EMACS_TIME_LE (atimers->expiration, now))
 339     {
 340       struct atimer *t = atimers;
 341       atimers = atimers->next;
 342       t->fn (t);
 343
 344       if (t->type == ATIMER_CONTINUOUS)
 345         {
 346           t->expiration = add_emacs_time (now, t->interval);
 347           schedule_atimer (t);
 348         }
 349       else
 350         {
 351           t->next = free_atimers;
 352           free_atimers = t;
 353         }
 354     }
 355
 356   set_alarm ();
 357 }
 358
 359
 360 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 361    SIGALRM.  */
 362
 363 static void
 364 handle_alarm_signal (int sig)
 365 {
 366   pending_signals = 1;
 367 }
 368
 369
 370 /* Do pending timers.  */
 371
 372 void
 373 do_pending_atimers (void)
 374 {
 375   if (atimers)
 376     {
 377       block_atimers ();
 378       run_timers ();
 379       unblock_atimers ();
 380     }
 381 }
 382
 383
 384 /* Turn alarms on/off.  This seems to be temporarily necessary on
 385    some systems like HPUX (see process.c).  */
 386
 387 void
 388 turn_on_atimers (bool on)
 389 {
 390   if (on)
 391     set_alarm ();
 392   else
 393     alarm (0);
 394 }
 395
 396
 397 void
 398 init_atimer (void)
 399 {
 400   struct sigaction action;
 401   free_atimers = stopped_atimers = atimers = NULL;
 402   /* pending_signals is initialized in init_keyboard.*/
 403   emacs_sigaction_init (&action, handle_alarm_signal);
 404   sigaction (SIGALRM, &action, 0);
 405 }