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 /* Free-list of atimer structures.  */
  39
  40 static struct atimer *free_atimers;
  41
  42 /* List of currently not running timers due to a call to
  43    lock_atimer.  */
  44
  45 static struct atimer *stopped_atimers;
  46
  47 /* List of active atimers, sorted by expiration time.  The timer that
  48    will become ripe next is always at the front of this list.  */
  49
  50 static struct atimer *atimers;
  51
  52 /* Non-zero means alarm_signal_handler has found ripe timers but
  53    interrupt_input_blocked was non-zero.  In this case, timer
  54    functions are not called until the next UNBLOCK_INPUT because timer
  55    functions are expected to call X, and X cannot be assumed to be
  56    reentrant.  */
  57
  58 int pending_atimers;
  59
  60 /* Block/unblock SIGALRM.  */
  61
  62 #define BLOCK_ATIMERS   sigblock (sigmask (SIGALRM))
  63 #define UNBLOCK_ATIMERS sigunblock (sigmask (SIGALRM))
  64
  65 /* Function prototypes.  */
  66
  67 static void set_alarm P_ ((void));
  68 static void schedule_atimer P_ ((struct atimer *));
  69 static struct atimer *append_atimer_lists P_ ((struct atimer *,
  70                                                struct atimer *));
  71 SIGTYPE alarm_signal_handler ();
  72
  73
  74 /* Start a new atimer of type TYPE.  TIME specifies when the timer is
  75    ripe.  FN is the function to call when the timer fires.
  76    CLIENT_DATA is stored in the client_data member of the atimer
  77    structure returned and so made available to FN when it is called.
  78
  79    If TYPE is ATIMER_ABSOLUTE, TIME is the absolute time at which the
  80    timer fires.
  81
  82    If TYPE is ATIMER_RELATIVE, the timer is ripe TIME s/us in the
  83    future.
  84
  85    In both cases, the timer is automatically freed after it has fired.
  86
  87    If TYPE is ATIMER_CONTINUOUS, the timer fires every TIME s/us.
  88
  89    Value is a pointer to the atimer started.  It can be used in calls
  90    to cancel_atimer; don't free it yourself.  */
  91
  92 struct atimer *
  93 start_atimer (type, time, fn, client_data)
  94      enum atimer_type type;
  95      EMACS_TIME time;
  96      atimer_callback fn;
  97      void *client_data;
  98 {
  99   struct atimer *t;
 100
 101   /* Round TIME up to the next full second if we don't have
 102      itimers.  */
 103 #ifndef HAVE_SETITIMER
 104   if (EMACS_USECS (time) != 0)
 105     {
 106       EMACS_SET_USECS (time, 0);
 107       EMACS_SET_SECS (time, EMACS_SECS (time) + 1);
 108     }
 109 #endif /* not HAVE_SETITIMER */
 110
 111   /* Get an atimer structure from the free-list, or allocate
 112      a new one.  */
 113   if (free_atimers)
 114     {
 115       t = free_atimers;
 116       free_atimers = t->next;
 117     }
 118   else
 119     t = (struct atimer *) xmalloc (sizeof *t);
 120
 121   /* Fill the atimer structure.  */
 122   bzero (t, sizeof *t);
 123   t->type = type;
 124   t->fn = fn;
 125   t->client_data = client_data;
 126
 127   BLOCK_ATIMERS;
 128
 129   /* Compute the timer's expiration time.  */
 130   switch (type)
 131     {
 132     case ATIMER_ABSOLUTE:
 133       t->expiration = time;
 134       break;
 135
 136     case ATIMER_RELATIVE:
 137       EMACS_GET_TIME (t->expiration);
 138       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 139       break;
 140
 141     case ATIMER_CONTINUOUS:
 142       EMACS_GET_TIME (t->expiration);
 143       EMACS_ADD_TIME (t->expiration, t->expiration, time);
 144       t->interval = time;
 145       break;
 146     }
 147
 148   /* Insert the timer in the list of active atimers.  */
 149   schedule_atimer (t);
 150   UNBLOCK_ATIMERS;
 151
 152   /* Arrange for a SIGALRM at the time the next atimer is ripe.  */
 153   set_alarm ();
 154
 155   return t;
 156 }
 157
 158
 159 /* Cancel and free atimer TIMER.  */
 160
 161 void
 162 cancel_atimer (timer)
 163      struct atimer *timer;
 164 {
 165   int i;
 166
 167   BLOCK_ATIMERS;
 168
 169   for (i = 0; i < 2; ++i)
 170     {
 171       struct atimer *t, *prev;
 172       struct atimer **list = i ? &stopped_atimers : &atimers;
 173
 174       /* See if TIMER is active or stopped.  */
 175       for (t = *list, prev = NULL; t && t != timer; prev = t, t = t->next)
 176         ;
 177
 178       /* If it is, take it off the its list, and put in on the
 179          free-list.  We don't bother to arrange for setting a
 180          different alarm time, since a too early one doesn't hurt.  */
 181       if (t)
 182         {
 183           if (prev)
 184             prev->next = t->next;
 185           else
 186             *list = t->next;
 187
 188           t->next = free_atimers;
 189           free_atimers = t;
 190           break;
 191         }
 192     }
 193
 194   UNBLOCK_ATIMERS;
 195 }
 196
 197
 198 /* Append two lists of atimers LIST1 and LIST2 and return the
 199    result list.  */
 200
 201 static struct atimer *
 202 append_atimer_lists (list1, list2)
 203      struct atimer *list1, *list2;
 204 {
 205   if (list1 == NULL)
 206     return list2;
 207   else if (list2 == NULL)
 208     return list1;
 209   else
 210     {
 211       struct atimer *p;
 212
 213       for (p = list1; p->next; p = p->next)
 214         ;
 215       p->next = list2;
 216       return list1;
 217     }
 218 }
 219
 220
 221 /* Stop all timers except timer T.  T null means stop all timers.  */
 222
 223 void
 224 stop_other_atimers (t)
 225      struct atimer *t;
 226 {
 227   BLOCK_ATIMERS;
 228
 229   if (t)
 230     {
 231       struct atimer *p, *prev;
 232
 233       /* See if T is active.  */
 234       for (p = atimers, prev = 0; p && p != t; p = p->next)
 235         ;
 236
 237       if (p == t)
 238         {
 239           if (prev)
 240             prev->next = t->next;
 241           else
 242             atimers = t->next;
 243           t->next = NULL;
 244         }
 245       else
 246         /* T is not active.  Let's handle this like T == 0.  */
 247         t = NULL;
 248     }
 249
 250   stopped_atimers = append_atimer_lists (atimers, stopped_atimers);
 251   atimers = t;
 252   UNBLOCK_ATIMERS;
 253 }
 254
 255
 256 /* Run all timers again, if some have been stopped with a call to
 257    stop_other_atimers.  */
 258
 259 void
 260 run_all_atimers ()
 261 {
 262   if (stopped_atimers)
 263     {
 264       struct atimer *t = atimers;
 265       struct atimer *next;
 266
 267       BLOCK_ATIMERS;
 268       atimers = stopped_atimers;
 269       stopped_atimers = NULL;
 270
 271       while (t)
 272         {
 273           next = t->next;
 274           schedule_atimer (t);
 275           t = next;
 276         }
 277
 278       UNBLOCK_ATIMERS;
 279     }
 280 }
 281
 282
 283 /* A version of run_all_timers suitable for a record_unwind_protect.  */
 284
 285 Lisp_Object
 286 unwind_stop_other_atimers (dummy)
 287      Lisp_Object dummy;
 288 {
 289   run_all_atimers ();
 290   return Qnil;
 291 }
 292
 293
 294 /* Arrange for a SIGALRM to arrive when the next timer is ripe.  */
 295
 296 static void
 297 set_alarm ()
 298 {
 299 #if defined (USG) && !defined (POSIX_SIGNALS)
 300   /* USG systems forget handlers when they are used;
 301      must reestablish each time.  */
 302   signal (SIGALRM, alarm_signal_handler);
 303 #endif /* USG */
 304
 305   if (atimers)
 306     {
 307       EMACS_TIME now, time;
 308 #ifdef HAVE_SETITIMER
 309       struct itimerval it;
 310 #endif
 311
 312       /* Determine s/us till the next timer is ripe.  */
 313       EMACS_GET_TIME (now);
 314       EMACS_SUB_TIME (time, atimers->expiration, now);
 315
 316 #ifdef HAVE_SETITIMER
 317       /* Don't set the interval to 0; this disables the timer.  */
 318       if (EMACS_TIME_LE (atimers->expiration, now))
 319         {
 320           EMACS_SET_SECS (time, 0);
 321           EMACS_SET_USECS (time, 1000);
 322         }
 323
 324       bzero (&it, sizeof it);
 325       it.it_value = time;
 326       setitimer (ITIMER_REAL, &it, 0);
 327 #else /* not HAVE_SETITIMER */
 328       alarm (max (EMACS_SECS (time), 1));
 329 #endif /* not HAVE_SETITIMER */
 330     }
 331 }
 332
 333
 334 /* Insert timer T into the list of active atimers `atimers', keeping
 335    the list sorted by expiration time.  T must not be in this list
 336    already.  */
 337
 338 static void
 339 schedule_atimer (t)
 340      struct atimer *t;
 341 {
 342   struct atimer *a = atimers, *prev = NULL;
 343
 344   /* Look for the first atimer that is ripe after T.  */
 345   while (a && EMACS_TIME_GT (t->expiration, a->expiration))
 346     prev = a, a = a->next;
 347
 348   /* Insert T in front of the atimer found, if any.  */
 349   if (prev)
 350     prev->next = t;
 351   else
 352     atimers = t;
 353
 354   t->next = a;
 355 }
 356
 357
 358 /* Signal handler for SIGALRM.  SIGNO is the signal number, i.e.
 359    SIGALRM.  */
 360
 361 SIGTYPE
 362 alarm_signal_handler (signo)
 363      int signo;
 364 {
 365   EMACS_TIME now;
 366
 367   EMACS_GET_TIME (now);
 368   pending_atimers = 0;
 369
 370   while (atimers
 371          && (pending_atimers = interrupt_input_blocked) == 0
 372          && EMACS_TIME_LE (atimers->expiration, now))
 373     {
 374       struct atimer *t;
 375
 376       t = atimers;
 377       atimers = atimers->next;
 378       t->fn (t);
 379
 380       if (t->type == ATIMER_CONTINUOUS)
 381         {
 382           EMACS_ADD_TIME (t->expiration, now, t->interval);
 383           schedule_atimer (t);
 384         }
 385       else
 386         {
 387           t->next = free_atimers;
 388           free_atimers = t;
 389         }
 390
 391       EMACS_GET_TIME (now);
 392     }
 393
 394   set_alarm ();
 395 }
 396
 397
 398 /* Call alarm_signal_handler for pending timers.  */
 399
 400 void
 401 do_pending_atimers ()
 402 {
 403   if (pending_atimers)
 404     {
 405       BLOCK_ATIMERS;
 406       alarm_signal_handler (SIGALRM);
 407       UNBLOCK_ATIMERS;
 408     }
 409 }
 410
 411
 412 /* Turn alarms on/off.  This seems to be temporarily necessary on
 413    some systems like HPUX (see process.c).  */
 414
 415 void
 416 turn_on_atimers (on)
 417      int on;
 418 {
 419   if (on)
 420     {
 421       signal (SIGALRM, alarm_signal_handler);
 422       set_alarm ();
 423     }
 424   else
 425     alarm (0);
 426 }
 427
 428
 429 void
 430 init_atimer ()
 431 {
 432   free_atimers = atimers = NULL;
 433   pending_atimers = 0;
 434   signal (SIGALRM, alarm_signal_handler);
 435 }