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 SIGTYPE alarm_signal_handler ();
  77
  78
  79 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  80    ripe.  FN is the function to call when the timer fires.
  81    CLIENT_DATA is stored in the client_data member of the atimer
  82    structure returned and so made available to FN when it is called.
  83
  84    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  85    timer fires.
  86
  87    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  88    future.
  89
  90    In both cases, the timer is automatically freed after it has fired.
  91
  92    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  93
  94    Value is a pointer to the atimer started.  It can be used in calls
  95    to cancel_atimer; don't free it yourself.  */
  96
  97 struct atimer *
  98 start_atimer (type, time, fn, client_data)
  99      enum atimer_type type;
 100      EMACS_TIME time;
 101      atimer_callback fn;
 102      void *client_data;
 103 {
 104   struct atimer *t;
 105
 106   /* Round TIME up to the next full second if we don't have
 107      itimers.  */
 108 #ifndef HAVE_SETITIMER
 109   if (EMACS_USECS (time) != 0)
 110     {
 111       EMACS_SET_USECS (time, 0);
 112       EMACS_SET_SECS (time, EMACS_SECS (time) + 1);
 113     }
 114 #endif /* not HAVE_SETITIMER */
 115
 116   /* Get an atimer structure from the free-list, or allocate
 117      a new one.  */
 118   if (free_atimers)
 119     {
 120       t = free_atimers;
 121       free_atimers = t->next;
 122     }
 123   else
 124     t = (struct atimer *) xmalloc (sizeof *t);
 125
 126   /* Fill the atimer structure.  */
 127   bzero (t, sizeof *t);
 128   t->type = type;
 129   t->fn = fn;
 130   t->client_data = client_data;
 131
 132   BLOCK_ATIMERS;
 133
 134   /* Compute the timer's expiration time.  */
 135   switch (type)
 136     {
 137     case ATIMER_ABSOLUTE:
 138       t->expiration = time;
 139       break;
 140
 141     case ATIMER_RELATIVE:
 142       EMACS_GET_TIME (t->expiration);
 143       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 144       break;
 145
 146     case ATIMER_CONTINUOUS:
 147       EMACS_GET_TIME (t->expiration);
 148       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 149       t->interval = time;
 150       break;
 151     }
 152
 153   /* Insert the timer in the list of active atimers.  */
 154   schedule_atimer (t);
 155   UNBLOCK_ATIMERS;
 156
 157   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 158   set_alarm ();
 159
 160   return t;
 161 }
 162
 163
 164 /* Cancel and free atimer TIMER.  */
 165
 166 void
 167 cancel_atimer (timer)
 168      struct atimer *timer;
 169 {
 170   int i;
 171
 172   BLOCK_ATIMERS;
 173
 174   for (i = 0; i < 2; ++i)
 175     {
 176       struct atimer *t, *prev;
 177       struct atimer **list = i ? &stopped_atimers : &atimers;
 178
 179       /* See if TIMER is active or stopped.  */
 180       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 181         ;
 182
 183       /* If it is, take it off the its list, and put in on the
 184          free-list.  We don't bother to arrange for setting a
 185          different alarm time, since a too early one doesn't hurt.  */
 186       if (t)
 187         {
 188           if (prev)
 189             prev->next = t->next;
 190           else
 191             *list = t->next;
 192
 193           t->next = free_atimers;
 194           free_atimers = t;
 195           break;
 196         }
 197     }
 198
 199   UNBLOCK_ATIMERS;
 200 }
 201
 202
 203 /* Append two lists of atimers LIST1 and LIST2 and return the
 204    result list.  */
 205
 206 static struct atimer *
 207 append_atimer_lists (list1, list2)
 208      struct atimer *list1, *list2;
 209 {
 210   if (list1 == NULL)
 211     return list2;
 212   else if (list2 == NULL)
 213     return list1;
 214   else
 215     {
 216       struct atimer *p;
 217
 218       for (p = list1; p->next; p = p->next)
 219         ;
 220       p->next = list2;
 221       return list1;
 222     }
 223 }
 224
 225
 226 /* Stop all timers except timer T.  T null means stop all timers.  */
 227
 228 void
 229 stop_other_atimers (t)
 230      struct atimer *t;
 231 {
 232   BLOCK_ATIMERS;
 233
 234   if (t)
 235     {
 236       struct atimer *p, *prev;
 237
 238       /* See if T is active.  */
 239       for (p = atimers, prev = 0; p && p != t; p = p->next)
 240         ;
 241
 242       if (p == t)
 243         {
 244           if (prev)
 245             prev->next = t->next;
 246           else
 247             atimers = t->next;
 248           t->next = NULL;
 249         }
 250       else
 251         /* T is not active.  Let's handle this like T == 0.  */
 252         t = NULL;
 253     }
 254
 255   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 256   atimers = t;
 257   UNBLOCK_ATIMERS;
 258 }
 259
 260
 261 /* Run all timers again, if some have been stopped with a call to
 262    stop_other_atimers.  */
 263
 264 void
 265 run_all_atimers ()
 266 {
 267   if (stopped_atimers)
 268     {
 269       struct atimer *t = atimers;
 270       struct atimer *next;
 271
 272       BLOCK_ATIMERS;
 273       atimers = stopped_atimers;
 274       stopped_atimers = NULL;
 275
 276       while (t)
 277         {
 278           next = t->next;
 279           schedule_atimer (t);
 280           t = next;
 281         }
 282
 283       UNBLOCK_ATIMERS;
 284     }
 285 }
 286
 287
 288 /* A version of run_all_timers suitable for a record_unwind_protect.  */
 289
 290 Lisp_Object
 291 unwind_stop_other_atimers (dummy)
 292      Lisp_Object dummy;
 293 {
 294   run_all_atimers ();
 295   return Qnil;
 296 }
 297
 298
 299 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 300
 301 static void
 302 set_alarm ()
 303 {
 304 #if defined (USG) && !defined (POSIX_SIGNALS)
 305   /* USG systems forget handlers when they are used;
 306      must reestablish each time.  */
 307   signal (SIGALRM, alarm_signal_handler);
 308 #endif /* USG */
 309
 310   if (atimers)
 311     {
 312       EMACS_TIME now, time;
 313 #ifdef HAVE_SETITIMER
 314       struct itimerval it;
 315 #endif
 316
 317       /* Determine s/us till the next timer is ripe.  */
 318       EMACS_GET_TIME (now);
 319       EMACS_SUB_TIME (time, atimers->expiration, now);
 320
 321 #ifdef HAVE_SETITIMER
 322       /* Don't set the interval to 0; this disables the timer.  */
 323       if (EMACS_TIME_LE (atimers->expiration, now))
 324         {
 325           EMACS_SET_SECS (time, 0);
 326           EMACS_SET_USECS (time, 1000);
 327         }
 328
 329       bzero (&it, sizeof it);
 330       it.it_value = time;
 331       setitimer (ITIMER_REAL, &it, 0);
 332 #else /* not HAVE_SETITIMER */
 333       alarm (max (EMACS_SECS (time), 1));
 334 #endif /* not HAVE_SETITIMER */
 335     }
 336 }
 337
 338
 339 /* Insert timer T into the list of active atimers `atimers', keeping
 340    the list sorted by expiration time.  T must not be in this list
 341    already.  */
 342
 343 static void
 344 schedule_atimer (t)
 345      struct atimer *t;
 346 {
 347   struct atimer *a = atimers, *prev = NULL;
 348
 349   /* Look for the first atimer that is ripe after T.  */
 350   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 351     prev = a, a = a->next;
 352
 353   /* Insert T in front of the atimer found, if any.  */
 354   if (prev)
 355     prev->next = t;
 356   else
 357     atimers = t;
 358
 359   t->next = a;
 360 }
 361
 362
 363 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 364    SIGALRM.  */
 365
 366 SIGTYPE
 367 alarm_signal_handler (signo)
 368      int signo;
 369 {
 370   EMACS_TIME now;
 371
 372   EMACS_GET_TIME (now);
 373   pending_atimers = 0;
 374
 375   while (atimers
 376          && (pending_atimers = interrupt_input_blocked) == 0
 377          && EMACS_TIME_LE (atimers->expiration, now))
 378     {
 379       struct atimer *t;
 380
 381       t = atimers;
 382       atimers = atimers->next;
 383       t->fn (t);
 384
 385       if (t->type == ATIMER_CONTINUOUS)
 386         {
 387           EMACS_ADD_TIME (t->expiration, now, t->interval);
 388           schedule_atimer (t);
 389         }
 390       else
 391         {
 392           t->next = free_atimers;
 393           free_atimers = t;
 394         }
 395
 396       EMACS_GET_TIME (now);
 397     }
 398
 399 #if defined (USG) && !defined (POSIX_SIGNALS)
 400   /* USG systems forget handlers when they are used;
 401      must reestablish each time.  */
 402   signal (SIGALRM, alarm_signal_handler);
 403 #endif /* USG */
 404
 405   set_alarm ();
 406 }
 407
 408
 409 /* Call alarm_signal_handler for pending timers.  */
 410
 411 void
 412 do_pending_atimers ()
 413 {
 414   if (pending_atimers)
 415     {
 416       BLOCK_ATIMERS;
 417       alarm_signal_handler (SIGALRM);
 418       UNBLOCK_ATIMERS;
 419     }
 420 }
 421
 422
 423 /* Turn alarms on/off.  This seems to be temporarily necessary on
 424    some systems like HPUX (see process.c).  */
 425
 426 void
 427 turn_on_atimers (on)
 428      int on;
 429 {
 430   if (on)
 431     {
 432       signal (SIGALRM, alarm_signal_handler);
 433       set_alarm ();
 434     }
 435   else
 436     alarm (0);
 437 }
 438
 439
 440 void
 441 init_atimer ()
 442 {
 443   free_atimers = atimers = NULL;
 444   pending_atimers = 0;
 445   signal (SIGALRM, alarm_signal_handler);
 446 }