src/atimer.c

   1 /* Asynchronous timers.
   2    Copyright (C) 2000 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 2, or (at your option)
   9 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; see the file COPYING.  If not, write to
  18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21 #include <config.h>
  22 #include <lisp.h>
  23 #include <signal.h>
  24 #include <syssignal.h>
  25 #include <systime.h>
  26 #include <blockinput.h>
  27 #include <atimer.h>
  28 #include <stdio.h>
  29
  30 #ifdef HAVE_UNISTD_H
  31 #include <unistd.h>
  32 #endif
  33
  34 #ifdef HAVE_SYS_TIME_H
  35 #include <sys/time.h>
  36 #endif
  37
  38 /* The ubiquitous min/max macros.  */
  39
  40 #define max(X, Y) ((X) > (Y) ? (X) : (Y))
  41 #define min(X, Y) ((X) < (Y) ? (X) : (Y))
  42
  43 /* Free-list of atimer structures.  */
  44
  45 static struct atimer *free_atimers;
  46
  47 /* List of currently not running timers due to a call to
  48    lock_atimer.  */
  49
  50 static struct atimer *stopped_atimers;
  51
  52 /* List of active atimers, sorted by expiration time.  The timer that
  53    will become ripe next is always at the front of this list.  */
  54
  55 static struct atimer *atimers;
  56
  57 /* Non-zero means alarm_signal_handler has found ripe timers but
  58    interrupt_input_blocked was non-zero.  In this case, timer
  59    functions are not called until the next UNBLOCK_INPUT because timer
  60    functions are expected to call X, and X cannot be assumed to be
  61    reentrant.  */
  62
  63 int pending_atimers;
  64
  65 /* Block/unblock SIGALRM.. */
  66
  67 #define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
  68 #define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
  69
  70 /* Function prototypes.  */
  71
  72 static void set_alarm P_ ((void));
  73 static void schedule_atimer P_ ((struct atimer *));
  74 static struct atimer *append_atimer_lists P_ ((struct atimer *,
  75                                                struct atimer *));
  76
  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 (type, time, fn, client_data)
  98      enum atimer_type type;
  99      EMACS_TIME time;
 100      atimer_callback fn;
 101      void *client_data;
 102 {
 103   struct atimer *t;
 104
 105   /* Round TIME up to the next full second if we don't have
 106      itimers.  */
 107 #ifndef HAVE_SETITIMER
 108   if (EMACS_USECS (time) != 0)
 109     {
 110       EMACS_SET_USECS (time, 0);
 111       EMACS_SET_SECS (time, EMACS_SECS (time) + 1);
 112     }
 113 #endif /* not HAVE_SETITIMER */
 114
 115   /* Get an atimer structure from the free-list, or allocate
 116      a new one.  */
 117   if (free_atimers)
 118     {
 119       t = free_atimers;
 120       free_atimers = t->next;
 121     }
 122   else
 123     t = (struct atimer *) xmalloc (sizeof *t);
 124
 125   /* Fill the atimer structure.  */
 126   bzero (t, sizeof *t);
 127   t->type = type;
 128   t->fn = fn;
 129   t->client_data = client_data;
 130
 131   BLOCK_ATIMERS;
 132
 133   /* Compute the timer's expiration time.  */
 134   switch (type)
 135     {
 136     case ATIMER_ABSOLUTE:
 137       t->expiration = time;
 138       break;
 139
 140     case ATIMER_RELATIVE:
 141       EMACS_GET_TIME (t->expiration);
 142       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 143       break;
 144
 145     case ATIMER_CONTINUOUS:
 146       EMACS_GET_TIME (t->expiration);
 147       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 148       t->interval = time;
 149       break;
 150     }
 151
 152   /* Insert the timer in the list of active atimers.  */
 153   schedule_atimer (t);
 154   UNBLOCK_ATIMERS;
 155
 156   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 157   set_alarm ();
 158
 159   return t;
 160 }
 161
 162
 163 /* Cancel and free atimer TIMER.  */
 164
 165 void
 166 cancel_atimer (timer)
 167      struct atimer *timer;
 168 {
 169   int i;
 170
 171   BLOCK_ATIMERS;
 172
 173   for (i = 0; i < 2; ++i)
 174     {
 175       struct atimer *t, *prev;
 176       struct atimer **list = i ? &stopped_atimers : &atimers;
 177
 178       /* See if TIMER is active or stopped.  */
 179       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 180         ;
 181
 182       /* If it is, take it off the its list, and put in on the
 183          free-list.  We don't bother to arrange for setting a
 184          different alarm time, since a too early one doesn't hurt.  */
 185       if (t)
 186         {
 187           if (prev)
 188             prev->next = t->next;
 189           else
 190             *list = t->next;
 191
 192           t->next = free_atimers;
 193           free_atimers = t;
 194           break;
 195         }
 196     }
 197
 198   UNBLOCK_ATIMERS;
 199 }
 200
 201
 202 /* Append two lists of atimers LIST1 and LIST2 and return the
 203    result list.  */
 204
 205 static struct atimer *
 206 append_atimer_lists (list1, list2)
 207      struct atimer *list1, *list2;
 208 {
 209   if (list1 == NULL)
 210     return list2;
 211   else if (list2 == NULL)
 212     return list1;
 213   else
 214     {
 215       struct atimer *p;
 216
 217       for (p = list1; p->next; p = p->next)
 218         ;
 219       p->next = list2;
 220       return list1;
 221     }
 222 }
 223
 224
 225 /* Stop all timers except timer T.  T null means stop all timers.  */
 226
 227 void
 228 stop_other_atimers (t)
 229      struct atimer *t;
 230 {
 231   BLOCK_ATIMERS;
 232
 233   if (t)
 234     {
 235       struct atimer *p, *prev;
 236
 237       /* See if T is active.  */
 238       for (p = atimers, prev = 0; p && p != t; p = p->next)
 239         ;
 240
 241       if (p == t)
 242         {
 243           if (prev)
 244             prev->next = t->next;
 245           else
 246             atimers = t->next;
 247           t->next = NULL;
 248         }
 249       else
 250         /* T is not active.  Let's handle this like T == 0.  */
 251         t = NULL;
 252     }
 253
 254   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 255   atimers = t;
 256   UNBLOCK_ATIMERS;
 257 }
 258
 259
 260 /* Run all timers again, if some have been stopped with a call to
 261    stop_other_atimers.  */
 262
 263 void
 264 run_all_atimers ()
 265 {
 266   if (stopped_atimers)
 267     {
 268       struct atimer *t = atimers;
 269       struct atimer *next;
 270
 271       BLOCK_ATIMERS;
 272       atimers = stopped_atimers;
 273       stopped_atimers = NULL;
 274
 275       while (t)
 276         {
 277           next = t->next;
 278           schedule_atimer (t);
 279           t = next;
 280         }
 281
 282       UNBLOCK_ATIMERS;
 283     }
 284 }
 285
 286
 287 /* A version of run_all_timers suitable for a record_unwind_protect.  */
 288
 289 Lisp_Object
 290 unwind_stop_other_atimers (dummy)
 291      Lisp_Object dummy;
 292 {
 293   run_all_atimers ();
 294   return Qnil;
 295 }
 296
 297
 298 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 299
 300 static void
 301 set_alarm ()
 302 {
 303 #if defined (USG) && !defined (POSIX_SIGNALS)
 304   /* USG systems forget handlers when they are used;
 305      must reestablish each time.  */
 306   signal (SIGALRM, alarm_signal_handler);
 307 #endif /* USG */
 308
 309   if (atimers)
 310     {
 311       EMACS_TIME now, time;
 312 #ifdef HAVE_SETITIMER
 313       struct itimerval it;
 314 #endif
 315
 316       /* Determine s/us till the next timer is ripe.  */
 317       EMACS_GET_TIME (now);
 318       EMACS_SUB_TIME (time, atimers->expiration, now);
 319
 320 #ifdef HAVE_SETITIMER
 321       /* Don't set the interval to 0; this disables the timer.  */
 322       if (EMACS_TIME_LE (atimers->expiration, now))
 323         {
 324           EMACS_SET_SECS (time, 0);
 325           EMACS_SET_USECS (time, 1000);
 326         }
 327
 328       bzero (&it, sizeof it);
 329       it.it_value = time;
 330       setitimer (ITIMER_REAL, &it, 0);
 331 #else /* not HAVE_SETITIMER */
 332       alarm (max (EMACS_SECS (time), 1));
 333 #endif /* not HAVE_SETITIMER */
 334     }
 335 }
 336
 337
 338 /* Insert timer T into the list of active atimers `atimers', keeping
 339    the list sorted by expiration time.  T must not be in this list
 340    already.  */
 341
 342 static void
 343 schedule_atimer (t)
 344      struct atimer *t;
 345 {
 346   struct atimer *a = atimers, *prev = NULL;
 347
 348   /* Look for the first atimer that is ripe after T.  */
 349   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 350     prev = a, a = a->next;
 351
 352   /* Insert T in front of the atimer found, if any.  */
 353   if (prev)
 354     prev->next = t;
 355   else
 356     atimers = t;
 357
 358   t->next = a;
 359 }
 360
 361
 362 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 363    SIGALRM.  */
 364
 365 SIGTYPE
 366 alarm_signal_handler (signo)
 367      int signo;
 368 {
 369   EMACS_TIME now;
 370
 371   EMACS_GET_TIME (now);
 372   pending_atimers = 0;
 373
 374   while (atimers
 375          && (pending_atimers = interrupt_input_blocked) == 0
 376          && EMACS_TIME_LE (atimers->expiration, now))
 377     {
 378       struct atimer *t;
 379
 380       t = atimers;
 381       atimers = atimers->next;
 382       t->fn (t);
 383
 384       if (t->type == ATIMER_CONTINUOUS)
 385         {
 386           EMACS_ADD_TIME (t->expiration, now, t->interval);
 387           schedule_atimer (t);
 388         }
 389       else
 390         {
 391           t->next = free_atimers;
 392           free_atimers = t;
 393         }
 394
 395       EMACS_GET_TIME (now);
 396     }
 397
 398 #if defined (USG) && !defined (POSIX_SIGNALS)
 399   /* USG systems forget handlers when they are used;
 400      must reestablish each time.  */
 401   signal (SIGALRM, alarm_signal_handler);
 402 #endif /* USG */
 403
 404   set_alarm ();
 405 }
 406
 407
 408 /* Call alarm_signal_handler for pending timers.  */
 409
 410 void
 411 do_pending_atimers ()
 412 {
 413   if (pending_atimers)
 414     {
 415       BLOCK_ATIMERS;
 416       alarm_signal_handler (SIGALRM);
 417       UNBLOCK_ATIMERS;
 418     }
 419 }
 420
 421
 422 /* Turn alarms on/off.  This seems to be temporarily necessary on
 423    some systems like HPUX (see process.c).  */
 424
 425 void
 426 turn_on_atimers (on)
 427      int on;
 428 {
 429   if (on)
 430     {
 431       signal (SIGALRM, alarm_signal_handler);
 432       set_alarm ();
 433     }
 434   else
 435     alarm (0);
 436 }
 437
 438
 439 void
 440 init_atimer ()
 441 {
 442   free_atimers = atimers = NULL;
 443   pending_atimers = 0;
 444   signal (SIGALRM, alarm_signal_handler);
 445 }