libguile/async.c

   1 /* Copyright (C) 1995, 96, 97, 98, 2000 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 "root.h"
  53 #include "smob.h"
  54
  55 #include "validate.h"
  56 #include "async.h"
  57
  58 #ifdef HAVE_STRING_H
  59 #include <string.h>
  60 #endif
  61 #ifdef HAVE_UNISTD_H
  62 #include <unistd.h>
  63 #endif
  64
  65
  66 \f
  67 /* {Asynchronous Events}
  68  *
  69  *
  70  * Async == thunk + mark.
  71  *
  72  * Setting the mark guarantees future execution of the thunk.  More
  73  * than one set may be satisfied by a single execution.
  74  *
  75  * scm_tick_clock decremented once per SCM_ALLOW_INTS.
  76  * Async execution triggered by SCM_ALLOW_INTS when scm_tick_clock drops to 0.
  77  * Async execution prevented by scm_mask_ints != 0.
  78  *
  79  * If the clock reaches 0 when scm_mask_ints != 0, then reset the clock
  80  * to 1.
  81  *
  82  * If the clock reaches 0 any other time, run marked asyncs.
  83  *
  84  * From a unix signal handler, mark a corresponding async and set the clock
  85  * to 1.   Do SCM_REDEFER_INTS;/SCM_REALLOW_INTS so that if the signal handler is not
  86  * called in the dynamic scope of a critical section, it is excecuted immediately.
  87  *
  88  * Overall, closely timed signals of a particular sort may be combined.  Pending signals
  89  * are delivered in a fixed priority order, regardless of arrival order.
  90  *
  91  */
  92
  93 /* True between SCM_DEFER_INTS and SCM_ALLOW_INTS, and
  94  * when the interpreter is not running at all.
  95  */
  96 int scm_ints_disabled = 1;
  97
  98 unsigned int scm_async_clock = 20;
  99 static unsigned int scm_async_rate = 20;
 100 unsigned int scm_mask_ints = 1;
 101
 102 static unsigned int scm_tick_clock = 0;
 103 static unsigned int scm_tick_rate = 0;
 104 static unsigned int scm_desired_tick_rate = 0;
 105 static unsigned int scm_switch_clock = 0;
 106 static unsigned int scm_switch_rate = 0;
 107 static unsigned int scm_desired_switch_rate = 0;
 108
 109 static long scm_tc16_async;
 110
 111 \f
 112
 113 int
 114 scm_asyncs_pending ()
 115 {
 116   SCM pos;
 117   pos = scm_asyncs;
 118   while (pos != SCM_EOL)
 119     {
 120       SCM a;
 121       struct scm_async * it;
 122       a = SCM_CAR (pos);
 123       it = SCM_ASYNC (a);
 124       if (it->got_it)
 125         return 1;
 126       pos = SCM_CDR (pos);
 127     }
 128   return 0;
 129 }
 130
 131 #if 0
 132 static SCM
 133 scm_sys_tick_async_thunk (void)
 134 {
 135   scm_deliver_signal (SCM_TICK_SIGNAL);
 136   return SCM_BOOL_F;
 137 }
 138 #endif
 139
 140 void
 141 scm_async_click ()
 142 {
 143   int owe_switch;
 144   int owe_tick;
 145
 146   if (!scm_switch_rate)
 147     {
 148       owe_switch = 0;
 149       scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 150       scm_desired_switch_rate = 0;
 151     }
 152   else
 153     {
 154       owe_switch = (scm_async_rate >= scm_switch_clock);
 155       if (owe_switch)
 156         {
 157           if (scm_desired_switch_rate)
 158             {
 159               scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 160               scm_desired_switch_rate = 0;
 161             }
 162           else
 163             scm_switch_clock = scm_switch_rate;
 164         }
 165       else
 166         {
 167           if (scm_desired_switch_rate)
 168             {
 169               scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 170               scm_desired_switch_rate = 0;
 171             }
 172           else
 173             scm_switch_clock -= scm_async_rate;
 174         }
 175     }
 176
 177   if (scm_mask_ints)
 178     {
 179       if (owe_switch)
 180         scm_switch ();
 181       scm_async_clock = 1;
 182       return;;
 183     }
 184
 185   if (!scm_tick_rate)
 186     {
 187       unsigned int r;
 188       owe_tick = 0;
 189       r = scm_desired_tick_rate;
 190       if (r)
 191         {
 192           scm_desired_tick_rate = 0;
 193           scm_tick_rate = r;
 194           scm_tick_clock = r;
 195         }
 196     }
 197   else
 198     {
 199       owe_tick = (scm_async_rate >= scm_tick_clock);
 200       if (owe_tick)
 201         {
 202           scm_tick_clock = scm_tick_rate = scm_desired_tick_rate;
 203           scm_desired_tick_rate = 0;
 204         }
 205       else
 206         {
 207           if (scm_desired_tick_rate)
 208             {
 209               scm_tick_clock = scm_tick_rate = scm_desired_tick_rate;
 210               scm_desired_tick_rate = 0;
 211             }
 212           else
 213             scm_tick_clock -= scm_async_rate;
 214         }
 215     }
 216
 217   /*
 218      if (owe_tick)
 219        scm_async_mark (system_signal_asyncs[SCM_SIG_ORD(SCM_TICK_SIGNAL)]);
 220      */
 221
 222   SCM_DEFER_INTS;
 223   if (scm_tick_rate && scm_switch_rate)
 224     {
 225       scm_async_rate = min (scm_tick_clock,  scm_switch_clock);
 226       scm_async_clock = scm_async_rate;
 227     }
 228   else if (scm_tick_rate)
 229     {
 230       scm_async_clock = scm_async_rate = scm_tick_clock;
 231     }
 232   else if (scm_switch_rate)
 233     {
 234       scm_async_clock = scm_async_rate = scm_switch_clock;
 235     }
 236   else
 237     scm_async_clock = scm_async_rate = 1 << 16;
 238   SCM_ALLOW_INTS_ONLY;
 239
 240  tail:
 241   scm_run_asyncs (scm_asyncs);
 242
 243   SCM_DEFER_INTS;
 244   if (scm_asyncs_pending ())
 245     {
 246       SCM_ALLOW_INTS_ONLY;
 247       goto tail;
 248     }
 249   SCM_ALLOW_INTS;
 250
 251   if (owe_switch)
 252     scm_switch ();
 253 }
 254
 255
 256 \f
 257
 258
 259 void
 260 scm_switch ()
 261 {
 262 #if 0 /* Thread switching code should probably reside here, but the
 263          async switching code doesn't seem to work, so it's put in the
 264          SCM_ASYNC_TICK macro instead. /mdj */
 265   SCM_THREAD_SWITCHING_CODE;
 266 #endif
 267 }
 268
 269 \f
 270
 271 static SCM
 272 mark_async (SCM obj)
 273 {
 274   struct scm_async * it;
 275   it = SCM_ASYNC (obj);
 276   return it->thunk;
 277 }
 278
 279 \f
 280
 281 SCM_DEFINE (scm_async, "async", 1, 0, 0,
 282            (SCM thunk),
 283 "")
 284 #define FUNC_NAME s_scm_async
 285 {
 286   SCM_RETURN_NEWSMOB2 (scm_tc16_async, 0, thunk);
 287 }
 288 #undef FUNC_NAME
 289
 290 SCM_DEFINE (scm_system_async, "system-async", 1, 0, 0,
 291             (SCM thunk),
 292 "")
 293 #define FUNC_NAME s_scm_system_async
 294 {
 295   SCM it;
 296   SCM list;
 297
 298   it = scm_async (thunk);
 299   SCM_NEWCELL (list);
 300   SCM_SETCAR (list, it);
 301   SCM_SETCDR (list, scm_asyncs);
 302   scm_asyncs = list;
 303   return it;
 304 }
 305 #undef FUNC_NAME
 306
 307 SCM_DEFINE (scm_async_mark, "async-mark", 1, 0, 0,
 308             (SCM a),
 309 "")
 310 #define FUNC_NAME s_scm_async_mark
 311 {
 312   struct scm_async * it;
 313   SCM_VALIDATE_ASYNC_COPY (1,a,it);
 314   it->got_it = 1;
 315   return SCM_UNSPECIFIED;
 316 }
 317 #undef FUNC_NAME
 318
 319
 320 SCM_DEFINE (scm_system_async_mark, "system-async-mark", 1, 0, 0,
 321            (SCM a),
 322 "")
 323 #define FUNC_NAME s_scm_system_async_mark
 324 {
 325   struct scm_async * it;
 326   SCM_VALIDATE_ASYNC_COPY (1,a,it);
 327   SCM_REDEFER_INTS;
 328   it->got_it = 1;
 329   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 330   scm_async_clock = 1;
 331   SCM_REALLOW_INTS;
 332   return SCM_UNSPECIFIED;
 333 }
 334 #undef FUNC_NAME
 335
 336
 337 SCM_DEFINE (scm_run_asyncs, "run-asyncs", 1, 0, 0,
 338            (SCM list_of_a),
 339 "")
 340 #define FUNC_NAME s_scm_run_asyncs
 341 {
 342   if (scm_mask_ints)
 343     return SCM_BOOL_F;
 344   while (list_of_a != SCM_EOL)
 345     {
 346       SCM a;
 347       struct scm_async * it;
 348       SCM_VALIDATE_CONS (1,list_of_a);
 349       a = SCM_CAR (list_of_a);
 350       SCM_VALIDATE_ASYNC_COPY (SCM_ARG1,a,it);
 351       scm_mask_ints = 1;
 352       if (it->got_it)
 353         {
 354           it->got_it = 0;
 355           scm_apply (it->thunk, SCM_EOL, SCM_EOL);
 356         }
 357       scm_mask_ints = 0;
 358       list_of_a = SCM_CDR (list_of_a);
 359     }
 360   return SCM_BOOL_T;
 361 }
 362 #undef FUNC_NAME
 363
 364 \f
 365
 366
 367 SCM_DEFINE (scm_noop, "noop", 0, 0, 1,
 368            (SCM args),
 369 "")
 370 #define FUNC_NAME s_scm_noop
 371 {
 372   return (SCM_NULLP (args) ? SCM_BOOL_F : SCM_CAR (args));
 373 }
 374 #undef FUNC_NAME
 375
 376
 377 \f
 378
 379 SCM_DEFINE (scm_set_tick_rate, "set-tick-rate", 1, 0, 0,
 380            (SCM n),
 381 "")
 382 #define FUNC_NAME s_scm_set_tick_rate
 383 {
 384   unsigned int old_n;
 385
 386
 387   SCM_VALIDATE_INUM (1,n);
 388
 389   old_n = scm_tick_rate;
 390
 391
 392   scm_desired_tick_rate = SCM_UNPACK (SCM_INUM (n));
 393   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 394   scm_async_clock = 1;
 395   return SCM_MAKINUM (old_n);
 396 }
 397 #undef FUNC_NAME
 398
 399 \f
 400
 401
 402 SCM_DEFINE (scm_set_switch_rate, "set-switch-rate", 1, 0, 0,
 403            (SCM n),
 404 "")
 405 #define FUNC_NAME s_scm_set_switch_rate
 406 {
 407   unsigned int old_n;
 408   SCM_VALIDATE_INUM (1,n);
 409   old_n = scm_switch_rate;
 410   scm_desired_switch_rate = SCM_UNPACK (SCM_INUM (n));
 411   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 412   scm_async_clock = 1;
 413   return SCM_MAKINUM (old_n);
 414 }
 415 #undef FUNC_NAME
 416
 417 \f
 418
 419 /* points to the GC system-async, so that scm_gc_end can find it.  */
 420 SCM scm_gc_async;
 421
 422 /* the vcell for gc-thunk.  */
 423 static SCM scm_gc_vcell;
 424
 425 /* the thunk installed in the GC system-async, which is marked at the
 426    end of garbage collection.  */
 427 static SCM
 428 scm_sys_gc_async_thunk (void)
 429 {
 430   if (SCM_NFALSEP (scm_gc_vcell))
 431     {
 432       SCM proc = SCM_CDR (scm_gc_vcell);
 433
 434       if (SCM_NFALSEP (proc) && !SCM_UNBNDP (proc))
 435         scm_apply (proc, SCM_EOL, SCM_EOL);
 436     }
 437   return SCM_UNSPECIFIED;
 438 }
 439
 440 \f
 441
 442 SCM_DEFINE (scm_unmask_signals, "unmask-signals", 0, 0, 0,
 443            (),
 444 "")
 445 #define FUNC_NAME s_scm_unmask_signals
 446 {
 447   scm_mask_ints = 0;
 448   return SCM_UNSPECIFIED;
 449 }
 450 #undef FUNC_NAME
 451
 452
 453 SCM_DEFINE (scm_mask_signals, "mask-signals", 0, 0, 0,
 454            (),
 455 "")
 456 #define FUNC_NAME s_scm_mask_signals
 457 {
 458   scm_mask_ints = 1;
 459   return SCM_UNSPECIFIED;
 460 }
 461 #undef FUNC_NAME
 462
 463 \f
 464
 465 void
 466 scm_init_async ()
 467 {
 468   SCM a_thunk;
 469   scm_tc16_async = scm_make_smob_type_mfpe ("async", 0,
 470                                            mark_async, NULL, NULL, NULL);
 471   scm_gc_vcell = scm_sysintern ("gc-thunk", SCM_BOOL_F);
 472   a_thunk = scm_make_gsubr ("%gc-thunk", 0, 0, 0, scm_sys_gc_async_thunk);
 473   scm_gc_async = scm_system_async (a_thunk);
 474
 475 #include "async.x"
 476 }