libguile/async.c

   1 /*      Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42 /* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
  43    gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
  44
  45 \f
  46
  47 #include <stdio.h>
  48 #include <signal.h>
  49 #include "_scm.h"
  50 #include "eval.h"
  51 #include "throw.h"
  52 #include "smob.h"
  53
  54 #include "scm_validate.h"
  55 #include "async.h"
  56
  57 #ifdef HAVE_STRING_H
  58 #include <string.h>
  59 #endif
  60 #ifdef HAVE_UNISTD_H
  61 #include <unistd.h>
  62 #endif
  63
  64
  65 \f
  66 /* {Asynchronous Events}
  67  *
  68  *
  69  * Async == thunk + mark.
  70  *
  71  * Setting the mark guarantees future execution of the thunk.  More
  72  * than one set may be satisfied by a single execution.
  73  *
  74  * scm_tick_clock decremented once per SCM_ALLOW_INTS.
  75  * Async execution triggered by SCM_ALLOW_INTS when scm_tick_clock drops to 0.
  76  * Async execution prevented by scm_mask_ints != 0.
  77  *
  78  * If the clock reaches 0 when scm_mask_ints != 0, then reset the clock
  79  * to 1.
  80  *
  81  * If the clock reaches 0 any other time, run marked asyncs.
  82  *
  83  * From a unix signal handler, mark a corresponding async and set the clock
  84  * to 1.   Do SCM_REDEFER_INTS;/SCM_REALLOW_INTS so that if the signal handler is not
  85  * called in the dynamic scope of a critical section, it is excecuted immediately.
  86  *
  87  * Overall, closely timed signals of a particular sort may be combined.  Pending signals
  88  * are delivered in a fixed priority order, regardless of arrival order.
  89  *
  90  */
  91
  92 /* True between SCM_DEFER_INTS and SCM_ALLOW_INTS, and
  93  * when the interpreter is not running at all.
  94  */
  95 int scm_ints_disabled = 1;
  96
  97 unsigned int scm_async_clock = 20;
  98 static unsigned int scm_async_rate = 20;
  99 unsigned int scm_mask_ints = 1;
 100
 101 static unsigned int scm_tick_clock = 0;
 102 static unsigned int scm_tick_rate = 0;
 103 static unsigned int scm_desired_tick_rate = 0;
 104 static unsigned int scm_switch_clock = 0;
 105 static unsigned int scm_switch_rate = 0;
 106 static unsigned int scm_desired_switch_rate = 0;
 107
 108 static long scm_tc16_async;
 109
 110 \f
 111
 112 int
 113 scm_asyncs_pending ()
 114 {
 115   SCM pos;
 116   pos = scm_asyncs;
 117   while (pos != SCM_EOL)
 118     {
 119       SCM a;
 120       struct scm_async * it;
 121       a = SCM_CAR (pos);
 122       it = SCM_ASYNC (a);
 123       if (it->got_it)
 124         return 1;
 125       pos = SCM_CDR (pos);
 126     }
 127   return 0;
 128 }
 129
 130 #if 0
 131 static SCM
 132 scm_sys_tick_async_thunk (void)
 133 {
 134   scm_deliver_signal (SCM_TICK_SIGNAL);
 135   return SCM_BOOL_F;
 136 }
 137 #endif
 138
 139 void
 140 scm_async_click ()
 141 {
 142   int owe_switch;
 143   int owe_tick;
 144
 145   if (!scm_switch_rate)
 146     {
 147       owe_switch = 0;
 148       scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 149       scm_desired_switch_rate = 0;
 150     }
 151   else
 152     {
 153       owe_switch = (scm_async_rate >= scm_switch_clock);
 154       if (owe_switch)
 155         {
 156           if (scm_desired_switch_rate)
 157             {
 158               scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 159               scm_desired_switch_rate = 0;
 160             }
 161           else
 162             scm_switch_clock = scm_switch_rate;
 163         }
 164       else
 165         {
 166           if (scm_desired_switch_rate)
 167             {
 168               scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 169               scm_desired_switch_rate = 0;
 170             }
 171           else
 172             scm_switch_clock -= scm_async_rate;
 173         }
 174     }
 175
 176   if (scm_mask_ints)
 177     {
 178       if (owe_switch)
 179         scm_switch ();
 180       scm_async_clock = 1;
 181       return;;
 182     }
 183
 184   if (!scm_tick_rate)
 185     {
 186       unsigned int r;
 187       owe_tick = 0;
 188       r = scm_desired_tick_rate;
 189       if (r)
 190         {
 191           scm_desired_tick_rate = 0;
 192           scm_tick_rate = r;
 193           scm_tick_clock = r;
 194         }
 195     }
 196   else
 197     {
 198       owe_tick = (scm_async_rate >= scm_tick_clock);
 199       if (owe_tick)
 200         {
 201           scm_tick_clock = scm_tick_rate = scm_desired_tick_rate;
 202           scm_desired_tick_rate = 0;
 203         }
 204       else
 205         {
 206           if (scm_desired_tick_rate)
 207             {
 208               scm_tick_clock = scm_tick_rate = scm_desired_tick_rate;
 209               scm_desired_tick_rate = 0;
 210             }
 211           else
 212             scm_tick_clock -= scm_async_rate;
 213         }
 214     }
 215
 216   /*
 217      if (owe_tick)
 218        scm_async_mark (system_signal_asyncs[SCM_SIG_ORD(SCM_TICK_SIGNAL)]);
 219      */
 220
 221   SCM_DEFER_INTS;
 222   if (scm_tick_rate && scm_switch_rate)
 223     {
 224       scm_async_rate = min (scm_tick_clock,  scm_switch_clock);
 225       scm_async_clock = scm_async_rate;
 226     }
 227   else if (scm_tick_rate)
 228     {
 229       scm_async_clock = scm_async_rate = scm_tick_clock;
 230     }
 231   else if (scm_switch_rate)
 232     {
 233       scm_async_clock = scm_async_rate = scm_switch_clock;
 234     }
 235   else
 236     scm_async_clock = scm_async_rate = 1 << 16;
 237   SCM_ALLOW_INTS_ONLY;
 238
 239  tail:
 240   scm_run_asyncs (scm_asyncs);
 241
 242   SCM_DEFER_INTS;
 243   if (scm_asyncs_pending ())
 244     {
 245       SCM_ALLOW_INTS_ONLY;
 246       goto tail;
 247     }
 248   SCM_ALLOW_INTS;
 249
 250   if (owe_switch)
 251     scm_switch ();
 252 }
 253
 254
 255 \f
 256
 257
 258 void
 259 scm_switch ()
 260 {
 261 #if 0 /* Thread switching code should probably reside here, but the
 262          async switching code doesn't seem to work, so it's put in the
 263          SCM_ASYNC_TICK macro instead. /mdj */
 264   SCM_THREAD_SWITCHING_CODE;
 265 #endif
 266 }
 267
 268 \f
 269
 270 static SCM
 271 mark_async (SCM obj)
 272 {
 273   struct scm_async * it;
 274   it = SCM_ASYNC (obj);
 275   return it->thunk;
 276 }
 277
 278 \f
 279
 280 GUILE_PROC(scm_async, "async", 1, 0, 0,
 281            (SCM thunk),
 282 "")
 283 #define FUNC_NAME s_scm_async
 284 {
 285   struct scm_async * async
 286     = (struct scm_async *) scm_must_malloc (sizeof (*async), FUNC_NAME);
 287   async->got_it = 0;
 288   async->thunk = thunk;
 289   SCM_RETURN_NEWSMOB (scm_tc16_async, async);
 290 }
 291 #undef FUNC_NAME
 292
 293 GUILE_PROC(scm_system_async, "system-async", 1, 0, 0,
 294             (SCM thunk),
 295 "")
 296 #define FUNC_NAME s_scm_system_async
 297 {
 298   SCM it;
 299   SCM list;
 300
 301   it = scm_async (thunk);
 302   SCM_NEWSMOB (list, it, scm_asyncs);
 303   scm_asyncs = list;
 304   return it;
 305 }
 306 #undef FUNC_NAME
 307
 308 GUILE_PROC(scm_async_mark, "async-mark", 1, 0, 0,
 309             (SCM a),
 310 "")
 311 #define FUNC_NAME s_scm_async_mark
 312 {
 313   struct scm_async * it;
 314   SCM_VALIDATE_ASYNC_COPY(1,a,it);
 315   it->got_it = 1;
 316   return SCM_UNSPECIFIED;
 317 }
 318 #undef FUNC_NAME
 319
 320
 321 GUILE_PROC(scm_system_async_mark, "system-async-mark", 1, 0, 0,
 322            (SCM a),
 323 "")
 324 #define FUNC_NAME s_scm_system_async_mark
 325 {
 326   struct scm_async * it;
 327   SCM_VALIDATE_ASYNC_COPY(1,a,it);
 328   SCM_REDEFER_INTS;
 329   it->got_it = 1;
 330   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 331   scm_async_clock = 1;
 332   SCM_REALLOW_INTS;
 333   return SCM_UNSPECIFIED;
 334 }
 335 #undef FUNC_NAME
 336
 337
 338 GUILE_PROC(scm_run_asyncs, "run-asyncs", 1, 0, 0,
 339            (SCM list_of_a),
 340 "")
 341 #define FUNC_NAME s_scm_run_asyncs
 342 {
 343   if (scm_mask_ints)
 344     return SCM_BOOL_F;
 345   while (list_of_a != SCM_EOL)
 346     {
 347       SCM a;
 348       struct scm_async * it;
 349       SCM_VALIDATE_NIMCONS(1,list_of_a);
 350       a = SCM_CAR (list_of_a);
 351       SCM_ASSERT (SCM_NIMP (a) &&  SCM_ASYNCP (a), a, SCM_ARG1, FUNC_NAME);
 352       it = SCM_ASYNC (a);
 353       scm_mask_ints = 1;
 354       if (it->got_it)
 355         {
 356           it->got_it = 0;
 357           scm_apply (it->thunk, SCM_EOL, SCM_EOL);
 358         }
 359       scm_mask_ints = 0;
 360       list_of_a = SCM_CDR (list_of_a);
 361     }
 362   return SCM_BOOL_T;
 363 }
 364 #undef FUNC_NAME
 365
 366 \f
 367
 368
 369 GUILE_PROC(scm_noop, "noop", 0, 0, 1,
 370            (SCM args),
 371 "")
 372 #define FUNC_NAME s_scm_noop
 373 {
 374   return (SCM_NULLP (args)
 375           ? SCM_BOOL_F
 376           : SCM_CAR (args));
 377 }
 378 #undef FUNC_NAME
 379
 380
 381 \f
 382
 383 GUILE_PROC(scm_set_tick_rate, "set-tick-rate", 1, 0, 0,
 384            (SCM n),
 385 "")
 386 #define FUNC_NAME s_scm_set_tick_rate
 387 {
 388   unsigned int old_n;
 389   SCM_VALIDATE_INT(1,n);
 390   old_n = scm_tick_rate;
 391   scm_desired_tick_rate = SCM_INUM (n);
 392   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 393   scm_async_clock = 1;
 394   return SCM_MAKINUM (old_n);
 395 }
 396 #undef FUNC_NAME
 397
 398 \f
 399
 400
 401 GUILE_PROC(scm_set_switch_rate, "set-switch-rate", 1, 0, 0,
 402            (SCM n),
 403 "")
 404 #define FUNC_NAME s_scm_set_switch_rate
 405 {
 406   unsigned int old_n;
 407   SCM_VALIDATE_INT(1,n);
 408   old_n = scm_switch_rate;
 409   scm_desired_switch_rate = SCM_INUM (n);
 410   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 411   scm_async_clock = 1;
 412   return SCM_MAKINUM (old_n);
 413 }
 414 #undef FUNC_NAME
 415
 416 \f
 417
 418 /* points to the GC system-async, so that scm_gc_end can find it.  */
 419 SCM scm_gc_async;
 420
 421 /* the vcell for gc-thunk.  */
 422 static SCM scm_gc_vcell;
 423
 424 /* the thunk installed in the GC system-async, which is marked at the
 425    end of garbage collection.  */
 426 static SCM
 427 scm_sys_gc_async_thunk (void)
 428 {
 429   if (SCM_NFALSEP (scm_gc_vcell))
 430     {
 431       SCM proc = SCM_CDR (scm_gc_vcell);
 432
 433       if (SCM_NFALSEP (proc) && !SCM_UNBNDP (proc))
 434         scm_apply (proc, SCM_EOL, SCM_EOL);
 435     }
 436   return SCM_UNSPECIFIED;
 437 }
 438
 439 \f
 440
 441 GUILE_PROC(scm_unmask_signals, "unmask-signals", 0, 0, 0,
 442            (),
 443 "")
 444 #define FUNC_NAME s_scm_unmask_signals
 445 {
 446   scm_mask_ints = 0;
 447   return SCM_UNSPECIFIED;
 448 }
 449 #undef FUNC_NAME
 450
 451
 452 GUILE_PROC(scm_mask_signals, "mask-signals", 0, 0, 0,
 453            (),
 454 "")
 455 #define FUNC_NAME s_scm_mask_signals
 456 {
 457   scm_mask_ints = 1;
 458   return SCM_UNSPECIFIED;
 459 }
 460 #undef FUNC_NAME
 461
 462 \f
 463
 464 void
 465 scm_init_async ()
 466 {
 467   SCM a_thunk;
 468   scm_tc16_async = scm_make_smob_type_mfpe ("async", sizeof (struct scm_async),
 469                                            mark_async, NULL, NULL, NULL);
 470   scm_gc_vcell = scm_sysintern ("gc-thunk", SCM_BOOL_F);
 471   a_thunk = scm_make_gsubr ("%gc-thunk", 0, 0, 0, scm_sys_gc_async_thunk);
 472   scm_gc_async = scm_system_async (a_thunk);
 473
 474 #include "async.x"
 475 }