src/atimer.c

   1 /* Asynchronous timers.
   2    Copyright (C) 2000-2014 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, struct timespec timestamp,
  98               atimer_callback fn, 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 (timestamp.tv_nsec != 0 && timestamp.tv_sec < TYPE_MAXIMUM (time_t))
 106     timestamp = make_timespec (timestamp.tv_sec + 1, 0);
 107 #endif /* not HAVE_SETITIMER */
 108
 109   /* Get an atimer structure from the free-list, or allocate
 110      a new one.  */
 111   if (free_atimers)
 112     {
 113       t = free_atimers;
 114       free_atimers = t->next;
 115     }
 116   else
 117     t = xmalloc (sizeof *t);
 118
 119   /* Fill the atimer structure.  */
 120   memset (t, 0, sizeof *t);
 121   t->type = type;
 122   t->fn = fn;
 123   t->client_data = client_data;
 124
 125   block_atimers ();
 126
 127   /* Compute the timer's expiration time.  */
 128   switch (type)
 129     {
 130     case ATIMER_ABSOLUTE:
 131       t->expiration = timestamp;
 132       break;
 133
 134     case ATIMER_RELATIVE:
 135       t->expiration = timespec_add (current_timespec (), timestamp);
 136       break;
 137
 138     case ATIMER_CONTINUOUS:
 139       t->expiration = timespec_add (current_timespec (), timestamp);
 140       t->interval = timestamp;
 141       break;
 142     }
 143
 144   /* Insert the timer in the list of active atimers.  */
 145   schedule_atimer (t);
 146   unblock_atimers ();
 147
 148   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 149   set_alarm ();
 150
 151   return t;
 152 }
 153
 154
 155 /* Cancel and free atimer TIMER.  */
 156
 157 void
 158 cancel_atimer (struct atimer *timer)
 159 {
 160   int i;
 161
 162   block_atimers ();
 163
 164   for (i = 0; i < 2; ++i)
 165     {
 166       struct atimer *t, *prev;
 167       struct atimer **list = i ? &stopped_atimers : &atimers;
 168
 169       /* See if TIMER is active or stopped.  */
 170       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 171         ;
 172
 173       /* If it is, take it off its list, and put in on the free-list.
 174          We don't bother to arrange for setting a different alarm time,
 175          since a too early one doesn't hurt.  */
 176       if (t)
 177         {
 178           if (prev)
 179             prev->next = t->next;
 180           else
 181             *list = t->next;
 182
 183           t->next = free_atimers;
 184           free_atimers = t;
 185           break;
 186         }
 187     }
 188
 189   unblock_atimers ();
 190 }
 191
 192
 193 /* Append two lists of atimers LIST_1 and LIST_2 and return the
 194    result list.  */
 195
 196 static struct atimer *
 197 append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 198 {
 199   if (list_1 == NULL)
 200     return list_2;
 201   else if (list_2 == NULL)
 202     return list_1;
 203   else
 204     {
 205       struct atimer *p;
 206
 207       for (p = list_1; p->next; p = p->next)
 208         ;
 209       p->next = list_2;
 210       return list_1;
 211     }
 212 }
 213
 214
 215 /* Stop all timers except timer T.  T null means stop all timers.  */
 216
 217 void
 218 stop_other_atimers (struct atimer *t)
 219 {
 220   block_atimers ();
 221
 222   if (t)
 223     {
 224       struct atimer *p, *prev;
 225
 226       /* See if T is active.  */
 227       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 228         ;
 229
 230       if (p == t)
 231         {
 232           if (prev)
 233             prev->next = t->next;
 234           else
 235             atimers = t->next;
 236           t->next = NULL;
 237         }
 238       else
 239         /* T is not active.  Let's handle this like T == 0.  */
 240         t = NULL;
 241     }
 242
 243   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 244   atimers = t;
 245   unblock_atimers ();
 246 }
 247
 248
 249 /* Run all timers again, if some have been stopped with a call to
 250    stop_other_atimers.  */
 251
 252 void
 253 run_all_atimers (void)
 254 {
 255   if (stopped_atimers)
 256     {
 257       struct atimer *t = atimers;
 258       struct atimer *next;
 259
 260       block_atimers ();
 261       atimers = stopped_atimers;
 262       stopped_atimers = NULL;
 263
 264       while (t)
 265         {
 266           next = t->next;
 267           schedule_atimer (t);
 268           t = next;
 269         }
 270
 271       unblock_atimers ();
 272     }
 273 }
 274
 275
 276 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 277
 278 static void
 279 set_alarm (void)
 280 {
 281   if (atimers)
 282     {
 283 #ifdef HAVE_SETITIMER
 284       struct itimerval it;
 285 #endif
 286       struct timespec now, interval;
 287
 288 #ifdef HAVE_ITIMERSPEC
 289       if (alarm_timer_ok)
 290         {
 291           struct itimerspec ispec;
 292           ispec.it_value = atimers->expiration;
 293           ispec.it_interval.tv_sec = ispec.it_interval.tv_nsec = 0;
 294           if (timer_settime (alarm_timer, 0, &ispec, 0) == 0)
 295             return;
 296         }
 297 #endif
 298
 299       /* Determine interval till the next timer is ripe.
 300          Don't set the interval to 0; this disables the timer.  */
 301       now = current_timespec ();
 302       interval = (timespec_cmp (atimers->expiration, now) <= 0
 303                   ? make_timespec (0, 1000 * 1000)
 304                   : timespec_sub (atimers->expiration, now));
 305
 306 #ifdef HAVE_SETITIMER
 307
 308       memset (&it, 0, sizeof it);
 309       it.it_value = make_timeval (interval);
 310       setitimer (ITIMER_REAL, &it, 0);
 311 #else /* not HAVE_SETITIMER */
 312       alarm (max (interval.tv_sec, 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 && timespec_cmp (a->expiration, t->expiration) < 0)
 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   struct timespec now = current_timespec ();
 344
 345   while (atimers && timespec_cmp (atimers->expiration, now) <= 0)
 346     {
 347       struct atimer *t = atimers;
 348       atimers = atimers->next;
 349       t->fn (t);
 350
 351       if (t->type == ATIMER_CONTINUOUS)
 352         {
 353           t->expiration = timespec_add (now, t->interval);
 354           schedule_atimer (t);
 355         }
 356       else
 357         {
 358           t->next = free_atimers;
 359           free_atimers = t;
 360         }
 361     }
 362
 363   set_alarm ();
 364 }
 365
 366
 367 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 368    SIGALRM.  */
 369
 370 static void
 371 handle_alarm_signal (int sig)
 372 {
 373   pending_signals = 1;
 374 }
 375
 376
 377 /* Do pending timers.  */
 378
 379 void
 380 do_pending_atimers (void)
 381 {
 382   if (atimers)
 383     {
 384       block_atimers ();
 385       run_timers ();
 386       unblock_atimers ();
 387     }
 388 }
 389
 390
 391 /* Turn alarms on/off.  This seems to be temporarily necessary on
 392    some systems like HPUX (see process.c).  */
 393
 394 void
 395 turn_on_atimers (bool on)
 396 {
 397   if (on)
 398     set_alarm ();
 399   else
 400     alarm (0);
 401 }
 402
 403
 404 void
 405 init_atimer (void)
 406 {
 407   struct sigaction action;
 408 #ifdef HAVE_ITIMERSPEC
 409   struct sigevent sigev;
 410   sigev.sigev_notify = SIGEV_SIGNAL;
 411   sigev.sigev_signo = SIGALRM;
 412   sigev.sigev_value.sival_ptr = &alarm_timer;
 413   alarm_timer_ok = timer_create (CLOCK_REALTIME, &sigev, &alarm_timer) == 0;
 414 #endif
 415   free_atimers = stopped_atimers = atimers = NULL;
 416   /* pending_signals is initialized in init_keyboard.*/
 417   emacs_sigaction_init (&action, handle_alarm_signal);
 418   sigaction (SIGALRM, &action, 0);
 419 }