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
  64 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  65    ripe.  FN is the function to call when the timer fires.
  66    CLIENT_DATA is stored in the client_data member of the atimer
  67    structure returned and so made available to FN when it is called.
  68
  69    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  70    timer fires.
  71
  72    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  73    future.
  74
  75    In both cases, the timer is automatically freed after it has fired.
  76
  77    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  78
  79    Value is a pointer to the atimer started.  It can be used in calls
  80    to cancel_atimer; don't free it yourself.  */
  81
  82 struct atimer *
  83 start_atimer (enum atimer_type type, EMACS_TIME timestamp, atimer_callback fn,
  84               void *client_data)
  85 {
  86   struct atimer *t;
  87
  88   /* Round TIME up to the next full second if we don't have
  89      itimers.  */
  90 #ifndef HAVE_SETITIMER
  91   if (EMACS_NSECS (timestamp) != 0
  92       && EMACS_SECS (timestamp) < TYPE_MAXIMUM (time_t))
  93     timestamp = make_emacs_time (EMACS_SECS (timestamp) + 1, 0);
  94 #endif /* not HAVE_SETITIMER */
  95
  96   /* Get an atimer structure from the free-list, or allocate
  97      a new one.  */
  98   if (free_atimers)
  99     {
 100       t = free_atimers;
 101       free_atimers = t->next;
 102     }
 103   else
 104     t = xmalloc (sizeof *t);
 105
 106   /* Fill the atimer structure.  */
 107   memset (t, 0, sizeof *t);
 108   t->type = type;
 109   t->fn = fn;
 110   t->client_data = client_data;
 111
 112   BLOCK_ATIMERS;
 113
 114   /* Compute the timer's expiration time.  */
 115   switch (type)
 116     {
 117     case ATIMER_ABSOLUTE:
 118       t->expiration = timestamp;
 119       break;
 120
 121     case ATIMER_RELATIVE:
 122       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 123       break;
 124
 125     case ATIMER_CONTINUOUS:
 126       t->expiration = add_emacs_time (current_emacs_time (), timestamp);
 127       t->interval = timestamp;
 128       break;
 129     }
 130
 131   /* Insert the timer in the list of active atimers.  */
 132   schedule_atimer (t);
 133   UNBLOCK_ATIMERS;
 134
 135   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 136   set_alarm ();
 137
 138   return t;
 139 }
 140
 141
 142 /* Cancel and free atimer TIMER.  */
 143
 144 void
 145 cancel_atimer (struct atimer *timer)
 146 {
 147   int i;
 148
 149   BLOCK_ATIMERS;
 150
 151   for (i = 0; i < 2; ++i)
 152     {
 153       struct atimer *t, *prev;
 154       struct atimer **list = i ? &stopped_atimers : &atimers;
 155
 156       /* See if TIMER is active or stopped.  */
 157       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 158         ;
 159
 160       /* If it is, take it off its list, and put in on the free-list.
 161          We don't bother to arrange for setting a different alarm time,
 162          since a too early one doesn't hurt.  */
 163       if (t)
 164         {
 165           if (prev)
 166             prev->next = t->next;
 167           else
 168             *list = t->next;
 169
 170           t->next = free_atimers;
 171           free_atimers = t;
 172           break;
 173         }
 174     }
 175
 176   UNBLOCK_ATIMERS;
 177 }
 178
 179
 180 /* Append two lists of atimers LIST_1 and LIST_2 and return the
 181    result list.  */
 182
 183 static struct atimer *
 184 append_atimer_lists (struct atimer *list_1, struct atimer *list_2)
 185 {
 186   if (list_1 == NULL)
 187     return list_2;
 188   else if (list_2 == NULL)
 189     return list_1;
 190   else
 191     {
 192       struct atimer *p;
 193
 194       for (p = list_1; p->next; p = p->next)
 195         ;
 196       p->next = list_2;
 197       return list_1;
 198     }
 199 }
 200
 201
 202 /* Stop all timers except timer T.  T null means stop all timers.  */
 203
 204 void
 205 stop_other_atimers (struct atimer *t)
 206 {
 207   BLOCK_ATIMERS;
 208
 209   if (t)
 210     {
 211       struct atimer *p, *prev;
 212
 213       /* See if T is active.  */
 214       for (p = atimers, prev = NULL; p && p != t; prev = p, p = p->next)
 215         ;
 216
 217       if (p == t)
 218         {
 219           if (prev)
 220             prev->next = t->next;
 221           else
 222             atimers = t->next;
 223           t->next = NULL;
 224         }
 225       else
 226         /* T is not active.  Let's handle this like T == 0.  */
 227         t = NULL;
 228     }
 229
 230   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 231   atimers = t;
 232   UNBLOCK_ATIMERS;
 233 }
 234
 235
 236 /* Run all timers again, if some have been stopped with a call to
 237    stop_other_atimers.  */
 238
 239 static void
 240 run_all_atimers (void)
 241 {
 242   if (stopped_atimers)
 243     {
 244       struct atimer *t = atimers;
 245       struct atimer *next;
 246
 247       BLOCK_ATIMERS;
 248       atimers = stopped_atimers;
 249       stopped_atimers = NULL;
 250
 251       while (t)
 252         {
 253           next = t->next;
 254           schedule_atimer (t);
 255           t = next;
 256         }
 257
 258       UNBLOCK_ATIMERS;
 259     }
 260 }
 261
 262
 263 /* A version of run_all_atimers suitable for a record_unwind_protect.  */
 264
 265 Lisp_Object
 266 unwind_stop_other_atimers (Lisp_Object dummy)
 267 {
 268   run_all_atimers ();
 269   return Qnil;
 270 }
 271
 272
 273 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 274
 275 static void
 276 set_alarm (void)
 277 {
 278   if (atimers)
 279     {
 280 #ifdef HAVE_SETITIMER
 281       struct itimerval it;
 282 #endif
 283
 284       /* Determine s/us till the next timer is ripe.  */
 285       EMACS_TIME now = current_emacs_time ();
 286
 287       /* Don't set the interval to 0; this disables the timer.  */
 288       EMACS_TIME interval = (EMACS_TIME_LE (atimers->expiration, now)
 289                              ? make_emacs_time (0, 1000 * 1000)
 290                              : sub_emacs_time (atimers->expiration, now));
 291
 292 #ifdef HAVE_SETITIMER
 293
 294       memset (&it, 0, sizeof it);
 295       it.it_value = make_timeval (interval);
 296       setitimer (ITIMER_REAL, &it, 0);
 297 #else /* not HAVE_SETITIMER */
 298       alarm (max (EMACS_SECS (interval), 1));
 299 #endif /* not HAVE_SETITIMER */
 300     }
 301 }
 302
 303
 304 /* Insert timer T into the list of active atimers `atimers', keeping
 305    the list sorted by expiration time.  T must not be in this list
 306    already.  */
 307
 308 static void
 309 schedule_atimer (struct atimer *t)
 310 {
 311   struct atimer *a = atimers, *prev = NULL;
 312
 313   /* Look for the first atimer that is ripe after T.  */
 314   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 315     prev = a, a = a->next;
 316
 317   /* Insert T in front of the atimer found, if any.  */
 318   if (prev)
 319     prev->next = t;
 320   else
 321     atimers = t;
 322
 323   t->next = a;
 324 }
 325
 326 static void
 327 run_timers (void)
 328 {
 329   EMACS_TIME now;
 330
 331   while (atimers
 332          && (pending_atimers = interrupt_input_blocked) == 0
 333          && (now = current_emacs_time (),
 334              EMACS_TIME_LE (atimers->expiration, now)))
 335     {
 336       struct atimer *t;
 337
 338       t = atimers;
 339       atimers = atimers->next;
 340       t->fn (t);
 341
 342       if (t->type == ATIMER_CONTINUOUS)
 343         {
 344           t->expiration = add_emacs_time (now, t->interval);
 345           schedule_atimer (t);
 346         }
 347       else
 348         {
 349           t->next = free_atimers;
 350           free_atimers = t;
 351         }
 352     }
 353
 354   if (! atimers)
 355     pending_atimers = 0;
 356
 357 #ifdef SYNC_INPUT
 358   if (pending_atimers)
 359     pending_signals = 1;
 360   else
 361     {
 362       pending_signals = interrupt_input_pending;
 363       set_alarm ();
 364     }
 365 #else
 366   if (! pending_atimers)
 367     set_alarm ();
 368 #endif
 369 }
 370
 371
 372 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 373    SIGALRM.  */
 374
 375 static void
 376 handle_alarm_signal (int sig)
 377 {
 378   pending_atimers = 1;
 379 #ifdef SYNC_INPUT
 380   pending_signals = 1;
 381 #else
 382   run_timers ();
 383 #endif
 384 }
 385
 386 static void
 387 deliver_alarm_signal (int sig)
 388 {
 389   handle_on_main_thread (sig, handle_alarm_signal);
 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, deliver_alarm_signal);
 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, deliver_alarm_signal);
 430 }