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 <signal.h>
  21 #include <stdio.h>
  22 #include <setjmp.h>
  23 #include "lisp.h"
  24 #include "syssignal.h"
  25 #include "systime.h"
  26 #include "blockinput.h"
  27 #include "atimer.h"
  28 #include <unistd.h>
  29
  30 /* Free-list of atimer structures.  */
  31
  32 static struct atimer *free_atimers;
  33
  34 /* List of currently not running timers due to a call to
  35    lock_atimer.  */
  36
  37 static struct atimer *stopped_atimers;
  38
  39 /* List of active atimers, sorted by expiration time.  The timer that
  40    will become ripe next is always at the front of this list.  */
  41
  42 static struct atimer *atimers;
  43
  44 /* Non-zero means alarm_signal_handler has found ripe timers but
  45    interrupt_input_blocked was non-zero.  In this case, timer
  46    functions are not called until the next UNBLOCK_INPUT because timer
  47    functions are expected to call X, and X cannot be assumed to be
  48    reentrant.  */
  49
  50 int pending_atimers;
  51
  52 /* Block/unblock SIGALRM.  */
  53
  54 #define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
  55 #define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
  56
  57 /* Function prototypes.  */
  58
  59 static void set_alarm (void);
  60 static void schedule_atimer (struct atimer *);
  61 static struct atimer *append_atimer_lists (struct atimer *,
  62                                            struct atimer *);
  63 static void alarm_signal_handler (int signo);
  64
  65
  66 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  67    ripe.  FN is the function to call when the timer fires.
  68    CLIENT_DATA is stored in the client_data member of the atimer
  69    structure returned and so made available to FN when it is called.
  70
  71    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  72    timer fires.
  73
  74    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  75    future.
  76
  77    In both cases, the timer is automatically freed after it has fired.
  78
  79    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  80
  81    Value is a pointer to the atimer started.  It can be used in calls
  82    to cancel_atimer; don't free it yourself.  */
  83
  84 struct atimer *
  85 start_atimer (enum atimer_type type, EMACS_TIME timestamp, atimer_callback fn,
  86               void *client_data)
  87 {
  88   struct atimer *t;
  89
  90   /* Round TIME up to the next full second if we don't have
  91      itimers.  */
  92 #ifndef HAVE_SETITIMER
  93   if (EMACS_NSECS (timestamp) != 0
  94       && EMACS_SECS (timestamp) < TYPE_MAXIMUM (time_t))
  95     timestamp = make_emacs_time (EMACS_SECS (timestamp) + 1, 0);
  96 #endif /* not HAVE_SETITIMER */
  97
  98   /* Get an atimer structure from the free-list, or allocate
  99      a new one.  */
 100   if (free_atimers)
 101     {
 102       t = free_atimers;
 103       free_atimers = t->next;
 104     }
 105   else
 106     t = xmalloc (sizeof *t);
 107
 108   /* Fill the atimer structure.  */
 109   memset (t, 0, sizeof *t);
 110   t->type = type;
 111   t->fn = fn;
 112   t->client_data = client_data;
 113
 114   BLOCK_ATIMERS;
 115
 116   /* Compute the timer's expiration time.  */
 117   switch (type)
 118     {
 119     case ATIMER_ABSOLUTE:
 120       t->expiration = timestamp;
 121       break;
 122
 123     case ATIMER_RELATIVE:
 124       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 125       break;
 126
 127     case ATIMER_CONTINUOUS:
 128       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 129       t->interval = timestamp;
 130       break;
 131     }
 132
 133   /* Insert the timer in the list of active atimers.  */
 134   schedule_atimer (t);
 135   UNBLOCK_ATIMERS;
 136
 137   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 138   set_alarm ();
 139
 140   return t;
 141 }
 142
 143
 144 /* Cancel and free atimer TIMER.  */
 145
 146 void
 147 cancel_atimer (struct atimer *timer)
 148 {
 149   int i;
 150
 151   BLOCK_ATIMERS;
 152
 153   for (i = 0; i < 2; ++i)
 154     {
 155       struct atimer *t, *prev;
 156       struct atimer **list = i ? &stopped_atimers : &atimers;
 157
 158       /* See if TIMER is active or stopped.  */
 159       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 160         ;
 161
 162       /* If it is, take it off its list, and put in on the free-list.
 163          We don't bother to arrange for setting a different alarm time,
 164          since a too early one doesn't hurt.  */
 165       if (t)
 166         {
 167           if (prev)
 168             prev->next = t->next;
 169           else
 170             *list = t->next;
 171
 172           t->next = free_atimers;
 173           free_atimers = t;
 174           break;
 175         }
 176     }
 177
 178   UNBLOCK_ATIMERS;
 179 }
 180
 181
 182 /* Append two lists of atimers LIST_1 and LIST_2 and return the
 183    result list.  */
 184
 185 static struct atimer *
 186 append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 187 {
 188   if (list_1 == NULL)
 189     return list_2;
 190   else if (list_2 == NULL)
 191     return list_1;
 192   else
 193     {
 194       struct atimer *p;
 195
 196       for (p = list_1; p->next; p = p->next)
 197         ;
 198       p->next = list_2;
 199       return list_1;
 200     }
 201 }
 202
 203
 204 /* Stop all timers except timer T.  T null means stop all timers.  */
 205
 206 void
 207 stop_other_atimers (struct atimer *t)
 208 {
 209   BLOCK_ATIMERS;
 210
 211   if (t)
 212     {
 213       struct atimer *p, *prev;
 214
 215       /* See if T is active.  */
 216       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 217         ;
 218
 219       if (p == t)
 220         {
 221           if (prev)
 222             prev->next = t->next;
 223           else
 224             atimers = t->next;
 225           t->next = NULL;
 226         }
 227       else
 228         /* T is not active.  Let's handle this like T == 0.  */
 229         t = NULL;
 230     }
 231
 232   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 233   atimers = t;
 234   UNBLOCK_ATIMERS;
 235 }
 236
 237
 238 /* Run all timers again, if some have been stopped with a call to
 239    stop_other_atimers.  */
 240
 241 static void
 242 run_all_atimers (void)
 243 {
 244   if (stopped_atimers)
 245     {
 246       struct atimer *t = atimers;
 247       struct atimer *next;
 248
 249       BLOCK_ATIMERS;
 250       atimers = stopped_atimers;
 251       stopped_atimers = NULL;
 252
 253       while (t)
 254         {
 255           next = t->next;
 256           schedule_atimer (t);
 257           t = next;
 258         }
 259
 260       UNBLOCK_ATIMERS;
 261     }
 262 }
 263
 264
 265 /* A version of run_all_atimers suitable for a record_unwind_protect.  */
 266
 267 Lisp_Object
 268 unwind_stop_other_atimers (Lisp_Object dummy)
 269 {
 270   run_all_atimers ();
 271   return Qnil;
 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
 286       /* Determine s/us till the next timer is ripe.  */
 287       EMACS_TIME now = current_emacs_time ();
 288
 289       /* Don't set the interval to 0; this disables the timer.  */
 290       EMACS_TIME interval = (EMACS_TIME_LE (atimers->expiration, now)
 291                              ? make_emacs_time (0, 1000 * 1000)
 292                              : sub_emacs_time (atimers->expiration, now));
 293
 294 #ifdef HAVE_SETITIMER
 295
 296       memset (&it, 0, sizeof it);
 297       it.it_value = make_timeval (interval);
 298       setitimer (ITIMER_REAL, &it, 0);
 299 #else /* not HAVE_SETITIMER */
 300       alarm (max (EMACS_SECS (interval), 1));
 301 #endif /* not HAVE_SETITIMER */
 302     }
 303 }
 304
 305
 306 /* Insert timer T into the list of active atimers `atimers', keeping
 307    the list sorted by expiration time.  T must not be in this list
 308    already.  */
 309
 310 static void
 311 schedule_atimer (struct atimer *t)
 312 {
 313   struct atimer *a = atimers, *prev = NULL;
 314
 315   /* Look for the first atimer that is ripe after T.  */
 316   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 317     prev = a, a = a->next;
 318
 319   /* Insert T in front of the atimer found, if any.  */
 320   if (prev)
 321     prev->next = t;
 322   else
 323     atimers = t;
 324
 325   t->next = a;
 326 }
 327
 328 static void
 329 run_timers (void)
 330 {
 331   EMACS_TIME now;
 332
 333   while (atimers
 334          && (pending_atimers = interrupt_input_blocked) == 0
 335          && (now = current_emacs_time (),
 336              EMACS_TIME_LE (atimers->expiration, now)))
 337     {
 338       struct atimer *t;
 339
 340       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   if (! atimers)
 357     pending_atimers = 0;
 358
 359 #ifdef SYNC_INPUT
 360   if (pending_atimers)
 361     pending_signals = 1;
 362   else
 363     {
 364       pending_signals = interrupt_input_pending;
 365       set_alarm ();
 366     }
 367 #else
 368   if (! pending_atimers)
 369     set_alarm ();
 370 #endif
 371 }
 372
 373
 374 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 375    SIGALRM.  */
 376
 377 void
 378 alarm_signal_handler (int signo)
 379 {
 380 #ifndef SYNC_INPUT
 381   SIGNAL_THREAD_CHECK (signo);
 382 #endif
 383
 384   pending_atimers = 1;
 385 #ifdef SYNC_INPUT
 386   pending_signals = 1;
 387 #else
 388   run_timers ();
 389 #endif
 390 }
 391
 392
 393 /* Call alarm_signal_handler for pending timers.  */
 394
 395 void
 396 do_pending_atimers (void)
 397 {
 398   if (pending_atimers)
 399     {
 400       BLOCK_ATIMERS;
 401       run_timers ();
 402       UNBLOCK_ATIMERS;
 403     }
 404 }
 405
 406
 407 /* Turn alarms on/off.  This seems to be temporarily necessary on
 408    some systems like HPUX (see process.c).  */
 409
 410 void
 411 turn_on_atimers (bool on)
 412 {
 413   if (on)
 414     {
 415       signal (SIGALRM, alarm_signal_handler);
 416       set_alarm ();
 417     }
 418   else
 419     alarm (0);
 420 }
 421
 422
 423 void
 424 init_atimer (void)
 425 {
 426   free_atimers = stopped_atimers = atimers = NULL;
 427   pending_atimers = 0;
 428   /* pending_signals is initialized in init_keyboard.*/
 429   signal (SIGALRM, alarm_signal_handler);
 430 }