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 \f
  42
  43 #include <stdio.h>
  44 #include <signal.h>
  45 #include "_scm.h"
  46 #include "eval.h"
  47 #include "throw.h"
  48 #include "smob.h"
  49
  50 #include "async.h"
  51
  52 #ifdef HAVE_STRING_H
  53 #include <string.h>
  54 #endif
  55 #ifdef HAVE_UNISTD_H
  56 #include <unistd.h>
  57 #endif
  58
  59
  60 \f
  61 /* {Asynchronous Events}
  62  *
  63  *
  64  * Async == thunk + mark.
  65  *
  66  * Setting the mark guarantees future execution of the thunk.  More
  67  * than one set may be satisfied by a single execution.
  68  *
  69  * scm_tick_clock decremented once per SCM_ALLOW_INTS.
  70  * Async execution triggered by SCM_ALLOW_INTS when scm_tick_clock drops to 0.
  71  * Async execution prevented by scm_mask_ints != 0.
  72  *
  73  * If the clock reaches 0 when scm_mask_ints != 0, then reset the clock
  74  * to 1.
  75  *
  76  * If the clock reaches 0 any other time, run marked asyncs.
  77  *
  78  * From a unix signal handler, mark a corresponding async and set the clock
  79  * to 1.   Do SCM_REDEFER_INTS;/SCM_REALLOW_INTS so that if the signal handler is not
  80  * called in the dynamic scope of a critical section, it is excecuted immediately.
  81  *
  82  * Overall, closely timed signals of a particular sort may be combined.  Pending signals
  83  * are delivered in a fixed priority order, regardless of arrival order.
  84  *
  85  */
  86
  87 /* True between SCM_DEFER_INTS and SCM_ALLOW_INTS, and
  88  * when the interpreter is not running at all.
  89  */
  90 int scm_ints_disabled = 1;
  91
  92 unsigned int scm_async_clock = 20;
  93 static unsigned int scm_async_rate = 20;
  94 unsigned int scm_mask_ints = 1;
  95
  96 static unsigned int scm_tick_clock = 0;
  97 static unsigned int scm_tick_rate = 0;
  98 static unsigned int scm_desired_tick_rate = 0;
  99 static unsigned int scm_switch_clock = 0;
 100 static unsigned int scm_switch_rate = 0;
 101 static unsigned int scm_desired_switch_rate = 0;
 102
 103 static long scm_tc16_async;
 104
 105 \f
 106
 107 int
 108 scm_asyncs_pending ()
 109 {
 110   SCM pos;
 111   pos = scm_asyncs;
 112   while (pos != SCM_EOL)
 113     {
 114       SCM a;
 115       struct scm_async * it;
 116       a = SCM_CAR (pos);
 117       it = SCM_ASYNC (a);
 118       if (it->got_it)
 119         return 1;
 120       pos = SCM_CDR (pos);
 121     }
 122   return 0;
 123 }
 124
 125 #if 0
 126 static SCM scm_sys_tick_async_thunk SCM_P ((void));
 127 static SCM
 128 scm_sys_tick_async_thunk ()
 129 {
 130   scm_deliver_signal (SCM_TICK_SIGNAL);
 131   return SCM_BOOL_F;
 132 }
 133 #endif
 134
 135 void
 136 scm_async_click ()
 137 {
 138   int owe_switch;
 139   int owe_tick;
 140
 141   if (!scm_switch_rate)
 142     {
 143       owe_switch = 0;
 144       scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 145       scm_desired_switch_rate = 0;
 146     }
 147   else
 148     {
 149       owe_switch = (scm_async_rate >= scm_switch_clock);
 150       if (owe_switch)
 151         {
 152           if (scm_desired_switch_rate)
 153             {
 154               scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 155               scm_desired_switch_rate = 0;
 156             }
 157           else
 158             scm_switch_clock = scm_switch_rate;
 159         }
 160       else
 161         {
 162           if (scm_desired_switch_rate)
 163             {
 164               scm_switch_clock = scm_switch_rate = scm_desired_switch_rate;
 165               scm_desired_switch_rate = 0;
 166             }
 167           else
 168             scm_switch_clock -= scm_async_rate;
 169         }
 170     }
 171
 172   if (scm_mask_ints)
 173     {
 174       if (owe_switch)
 175         scm_switch ();
 176       scm_async_clock = 1;
 177       return;;
 178     }
 179
 180   if (!scm_tick_rate)
 181     {
 182       unsigned int r;
 183       owe_tick = 0;
 184       r = scm_desired_tick_rate;
 185       if (r)
 186         {
 187           scm_desired_tick_rate = 0;
 188           scm_tick_rate = r;
 189           scm_tick_clock = r;
 190         }
 191     }
 192   else
 193     {
 194       owe_tick = (scm_async_rate >= scm_tick_clock);
 195       if (owe_tick)
 196         {
 197           scm_tick_clock = scm_tick_rate = scm_desired_tick_rate;
 198           scm_desired_tick_rate = 0;
 199         }
 200       else
 201         {
 202           if (scm_desired_tick_rate)
 203             {
 204               scm_tick_clock = scm_tick_rate = scm_desired_tick_rate;
 205               scm_desired_tick_rate = 0;
 206             }
 207           else
 208             scm_tick_clock -= scm_async_rate;
 209         }
 210     }
 211
 212   /*
 213      if (owe_tick)
 214        scm_async_mark (system_signal_asyncs[SCM_SIG_ORD(SCM_TICK_SIGNAL)]);
 215      */
 216
 217   SCM_DEFER_INTS;
 218   if (scm_tick_rate && scm_switch_rate)
 219     {
 220       scm_async_rate = min (scm_tick_clock,  scm_switch_clock);
 221       scm_async_clock = scm_async_rate;
 222     }
 223   else if (scm_tick_rate)
 224     {
 225       scm_async_clock = scm_async_rate = scm_tick_clock;
 226     }
 227   else if (scm_switch_rate)
 228     {
 229       scm_async_clock = scm_async_rate = scm_switch_clock;
 230     }
 231   else
 232     scm_async_clock = scm_async_rate = 1 << 16;
 233   SCM_ALLOW_INTS_ONLY;
 234
 235  tail:
 236   scm_run_asyncs (scm_asyncs);
 237
 238   SCM_DEFER_INTS;
 239   if (scm_asyncs_pending ())
 240     {
 241       SCM_ALLOW_INTS_ONLY;
 242       goto tail;
 243     }
 244   SCM_ALLOW_INTS;
 245
 246   if (owe_switch)
 247     scm_switch ();
 248 }
 249
 250
 251 \f
 252
 253
 254 void
 255 scm_switch ()
 256 {
 257 #if 0 /* Thread switching code should probably reside here, but the
 258          async switching code doesn't seem to work, so it's put in the
 259          SCM_ASYNC_TICK macro instead. /mdj */
 260   SCM_THREAD_SWITCHING_CODE;
 261 #endif
 262 }
 263
 264 \f
 265
 266 static SCM mark_async SCM_P ((SCM obj));
 267
 268 static SCM
 269 mark_async (obj)
 270      SCM obj;
 271 {
 272   struct scm_async * it;
 273   it = SCM_ASYNC (obj);
 274   return it->thunk;
 275 }
 276
 277 \f
 278
 279 SCM_PROC(s_async, "async", 1, 0, 0, scm_async);
 280
 281 SCM
 282 scm_async (thunk)
 283      SCM thunk;
 284 {
 285   struct scm_async * async
 286     = (struct scm_async *) scm_must_malloc (sizeof (*async), s_async);
 287   async->got_it = 0;
 288   async->thunk = thunk;
 289   SCM_RETURN_NEWSMOB (scm_tc16_async, async);
 290 }
 291
 292 SCM_PROC(s_system_async, "system-async", 1, 0, 0, scm_system_async);
 293
 294 SCM
 295 scm_system_async (thunk)
 296      SCM thunk;
 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
 307 SCM_PROC(s_async_mark, "async-mark", 1, 0, 0, scm_async_mark);
 308
 309 SCM
 310 scm_async_mark (a)
 311      SCM a;
 312 {
 313   struct scm_async * it;
 314   SCM_ASSERT (SCM_NIMP (a) &&  SCM_ASYNCP (a), a, SCM_ARG1, s_async_mark);
 315   it = SCM_ASYNC (a);
 316   it->got_it = 1;
 317   return SCM_UNSPECIFIED;
 318 }
 319
 320
 321 SCM_PROC(s_system_async_mark, "system-async-mark", 1, 0, 0, scm_system_async_mark);
 322
 323 SCM
 324 scm_system_async_mark (a)
 325      SCM a;
 326 {
 327   struct scm_async * it;
 328   SCM_ASSERT (SCM_NIMP (a) &&  SCM_ASYNCP (a), a, SCM_ARG1, s_async_mark);
 329   it = SCM_ASYNC (a);
 330   SCM_REDEFER_INTS;
 331   it->got_it = 1;
 332   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 333   scm_async_clock = 1;
 334   SCM_REALLOW_INTS;
 335   return SCM_UNSPECIFIED;
 336 }
 337
 338
 339 SCM_PROC(s_run_asyncs, "run-asyncs", 1, 0, 0, scm_run_asyncs);
 340
 341 SCM
 342 scm_run_asyncs (list_of_a)
 343      SCM list_of_a;
 344 {
 345   SCM pos;
 346
 347   if (scm_mask_ints)
 348     return SCM_BOOL_F;
 349   pos = list_of_a;
 350   while (pos != SCM_EOL)
 351     {
 352       SCM a;
 353       struct scm_async * it;
 354       SCM_ASSERT (SCM_NIMP (pos) && SCM_CONSP (pos), pos, SCM_ARG1, s_run_asyncs);
 355       a = SCM_CAR (pos);
 356       SCM_ASSERT (SCM_NIMP (a) &&  SCM_ASYNCP (a), a, SCM_ARG1, s_run_asyncs);
 357       it = SCM_ASYNC (a);
 358       scm_mask_ints = 1;
 359       if (it->got_it)
 360         {
 361           it->got_it = 0;
 362           scm_apply (it->thunk, SCM_EOL, SCM_EOL);
 363         }
 364       scm_mask_ints = 0;
 365       pos = SCM_CDR (pos);
 366     }
 367   return SCM_BOOL_T;
 368 }
 369
 370 \f
 371
 372
 373 SCM_PROC(s_noop, "noop", 0, 0, 1, scm_noop);
 374
 375 SCM
 376 scm_noop (args)
 377      SCM args;
 378 {
 379   return (SCM_NULLP (args)
 380           ? SCM_BOOL_F
 381           : SCM_CAR (args));
 382 }
 383
 384
 385 \f
 386
 387 SCM_PROC(s_set_tick_rate, "set-tick-rate", 1, 0, 0, scm_set_tick_rate);
 388
 389 SCM
 390 scm_set_tick_rate (n)
 391      SCM n;
 392 {
 393   unsigned int old_n;
 394   SCM_ASSERT (SCM_INUMP (n), n, SCM_ARG1, s_set_tick_rate);
 395   old_n = scm_tick_rate;
 396   scm_desired_tick_rate = SCM_INUM (n);
 397   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 398   scm_async_clock = 1;
 399   return SCM_MAKINUM (old_n);
 400 }
 401
 402 \f
 403
 404
 405 SCM_PROC(s_set_switch_rate, "set-switch-rate", 1, 0, 0, scm_set_switch_rate);
 406
 407 SCM
 408 scm_set_switch_rate (n)
 409      SCM n;
 410 {
 411   unsigned int old_n;
 412   SCM_ASSERT (SCM_INUMP (n), n, SCM_ARG1, s_set_switch_rate);
 413   old_n = scm_switch_rate;
 414   scm_desired_switch_rate = SCM_INUM (n);
 415   scm_async_rate = 1 + scm_async_rate - scm_async_clock;
 416   scm_async_clock = 1;
 417   return SCM_MAKINUM (old_n);
 418 }
 419
 420 \f
 421
 422 /* points to the GC system-async, so that scm_gc_end can find it.  */
 423 SCM scm_gc_async;
 424
 425 /* the vcell for gc-thunk.  */
 426 static SCM scm_gc_vcell;
 427
 428 /* the thunk installed in the GC system-async, which is marked at the
 429    end of garbage collection.  */
 430 static SCM
 431 scm_sys_gc_async_thunk (void)
 432 {
 433   if (SCM_NFALSEP (scm_gc_vcell))
 434     {
 435       SCM proc = SCM_CDR (scm_gc_vcell);
 436
 437       if (SCM_NFALSEP (proc) && !SCM_UNBNDP (proc))
 438         scm_apply (proc, SCM_EOL, SCM_EOL);
 439     }
 440   return SCM_UNSPECIFIED;
 441 }
 442
 443 \f
 444
 445 SCM_PROC(s_unmask_signals, "unmask-signals", 0, 0, 0, scm_unmask_signals);
 446
 447 SCM
 448 scm_unmask_signals ()
 449 {
 450   scm_mask_ints = 0;
 451   return SCM_UNSPECIFIED;
 452 }
 453
 454
 455 SCM_PROC(s_mask_signals, "mask-signals", 0, 0, 0, scm_mask_signals);
 456
 457 SCM
 458 scm_mask_signals ()
 459 {
 460   scm_mask_ints = 1;
 461   return SCM_UNSPECIFIED;
 462 }
 463
 464 \f
 465
 466 void
 467 scm_init_async ()
 468 {
 469   SCM a_thunk;
 470   scm_tc16_async = scm_make_smob_type_mfpe ("async", sizeof (struct scm_async),
 471                                            mark_async, NULL, NULL, NULL);
 472   scm_gc_vcell = scm_sysintern ("gc-thunk", SCM_BOOL_F);
 473   a_thunk = scm_make_gsubr ("%gc-thunk", 0, 0, 0, scm_sys_gc_async_thunk);
 474   scm_gc_async = scm_system_async (a_thunk);
 475
 476 #include "async.x"
 477 }