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