unofficial mirror of emacs-devel@gnu.org 
 help / color / mirror / code / Atom feed
blob b638dd77f8b051f23cf44013c50ff630180d5fd4 30132 bytes (raw)
name: src/thread.c 	 # note: path name is non-authoritative(*)

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
 
/* Threading code.
Copyright (C) 2012-2020 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */


#include <config.h>
#include <setjmp.h>
#include "lisp.h"
#include "character.h"
#include "buffer.h"
#include "process.h"
#include "coding.h"
#include "syssignal.h"
#include "pdumper.h"
#include "keyboard.h"

union aligned_thread_state
{
  struct thread_state s;
  GCALIGNED_UNION_MEMBER
};
verify (GCALIGNED (union aligned_thread_state));

static union aligned_thread_state main_thread
  = {{
      .header.size = PVECHEADERSIZE (PVEC_THREAD,
				     PSEUDOVECSIZE (struct thread_state,
						    event_object),
				     VECSIZE (struct thread_state)),
      .m_last_thing_searched = LISPSYM_INITIALLY (Qnil),
      .m_saved_last_thing_searched = LISPSYM_INITIALLY (Qnil),
      .name = LISPSYM_INITIALLY (Qnil),
      .function = LISPSYM_INITIALLY (Qnil),
      .result = LISPSYM_INITIALLY (Qnil),
      .error_symbol = LISPSYM_INITIALLY (Qnil),
      .error_data = LISPSYM_INITIALLY (Qnil),
      .event_object = LISPSYM_INITIALLY (Qnil),
    }};

struct thread_state *current_thread = &main_thread.s;

static struct thread_state *all_threads = &main_thread.s;

static sys_mutex_t global_lock;

extern volatile int interrupt_input_blocked;

\f

/* m_specpdl is set when the thread is created and cleared when the
   thread dies.  */
#define thread_live_p(STATE) ((STATE)->m_specpdl != NULL)

\f

static void
release_global_lock (void)
{
  sys_mutex_unlock (&global_lock);
}

/* You must call this after acquiring the global lock.
   acquire_global_lock does it for you.  */
static void
post_acquire_global_lock (struct thread_state *self)
{
  struct thread_state *prev_thread = current_thread;

  /* Do this early on, so that code below could signal errors (e.g.,
     unbind_for_thread_switch might) correctly, because we are already
     running in the context of the thread pointed by SELF.  */
  current_thread = self;

  if (prev_thread != current_thread)
    {
      /* PREV_THREAD is NULL if the previously current thread
	 exited.  In this case, there is no reason to unbind, and
	 trying will crash.  */
      if (prev_thread != NULL)
	unbind_for_thread_switch (prev_thread);
      rebind_for_thread_switch ();

       /* Set the new thread's current buffer.  This needs to be done
	  even if it is the same buffer as that of the previous thread,
	  because of thread-local bindings.  */
      set_buffer_internal_2 (current_buffer);
    }

   /* We could have been signaled while waiting to grab the global lock
      for the first time since this thread was created, in which case
      we didn't yet have the opportunity to set up the handlers.  Delay
      raising the signal in that case (it will be actually raised when
      the thread comes here after acquiring the lock the next time).  */
  if (!NILP (current_thread->error_symbol) && handlerlist)
    {
      Lisp_Object sym = current_thread->error_symbol;
      Lisp_Object data = current_thread->error_data;

      current_thread->error_symbol = Qnil;
      current_thread->error_data = Qnil;
      Fsignal (sym, data);
    }
}

static void
acquire_global_lock (struct thread_state *self)
{
  sys_mutex_lock (&global_lock);
  post_acquire_global_lock (self);
}

/* This is called from keyboard.c when it detects that SIGINT was
   delivered to the main thread and interrupted thread_select before
   the main thread could acquire the lock.  We must acquire the lock
   to prevent a thread from running without holding the global lock,
   and to avoid repeated calls to sys_mutex_unlock, which invokes
   undefined behavior.  */
void
maybe_reacquire_global_lock (void)
{
  /* SIGINT handler is always run on the main thread, see
     deliver_process_signal, so reflect that in our thread-tracking
     variables.  */
  current_thread = &main_thread.s;

  if (current_thread->not_holding_lock)
    {
      struct thread_state *self = current_thread;

      acquire_global_lock (self);
      current_thread->not_holding_lock = 0;
    }
}

\f

static void
lisp_mutex_init (lisp_mutex_t *mutex)
{
  mutex->owner = NULL;
  mutex->count = 0;
  sys_cond_init (&mutex->condition);
}

/* Lock MUTEX for thread LOCKER, setting its lock count to COUNT, if
   non-zero, or to 1 otherwise.

   If MUTEX is locked by LOCKER, COUNT must be zero, and the MUTEX's
   lock count will be incremented.

   If MUTEX is locked by another thread, this function will release
   the global lock, giving other threads a chance to run, and will
   wait for the MUTEX to become unlocked; when MUTEX becomes unlocked,
   and will then re-acquire the global lock.

   Return value is 1 if the function waited for the MUTEX to become
   unlocked (meaning other threads could have run during the wait),
   zero otherwise.  */
static int
lisp_mutex_lock_for_thread (lisp_mutex_t *mutex, struct thread_state *locker,
			    int new_count)
{
  struct thread_state *self;

  if (mutex->owner == NULL)
    {
      mutex->owner = locker;
      mutex->count = new_count == 0 ? 1 : new_count;
      return 0;
    }
  if (mutex->owner == locker)
    {
      eassert (new_count == 0);
      ++mutex->count;
      return 0;
    }

  self = locker;
  self->wait_condvar = &mutex->condition;
  while (mutex->owner != NULL && (new_count != 0
				  || NILP (self->error_symbol)))
    sys_cond_wait (&mutex->condition, &global_lock);
  self->wait_condvar = NULL;

  if (new_count == 0 && !NILP (self->error_symbol))
    return 1;

  mutex->owner = self;
  mutex->count = new_count == 0 ? 1 : new_count;

  return 1;
}

static int
lisp_mutex_lock (lisp_mutex_t *mutex, int new_count)
{
  return lisp_mutex_lock_for_thread (mutex, current_thread, new_count);
}

/* Decrement MUTEX's lock count.  If the lock count becomes zero after
   decrementing it, meaning the mutex is now unlocked, broadcast that
   to all the threads that might be waiting to lock the mutex.  This
   function signals an error if MUTEX is locked by a thread other than
   the current one.  Return value is 1 if the mutex becomes unlocked,
   zero otherwise.  */
static int
lisp_mutex_unlock (lisp_mutex_t *mutex)
{
  if (mutex->owner != current_thread)
    error ("Cannot unlock mutex owned by another thread");

  if (--mutex->count > 0)
    return 0;

  mutex->owner = NULL;
  sys_cond_broadcast (&mutex->condition);

  return 1;
}

/* Like lisp_mutex_unlock, but sets MUTEX's lock count to zero
   regardless of its value.  Return the previous lock count.  */
static unsigned int
lisp_mutex_unlock_for_wait (lisp_mutex_t *mutex)
{
  unsigned int result = mutex->count;

  /* Ensured by condvar code.  */
  eassert (mutex->owner == current_thread);

  mutex->count = 0;
  mutex->owner = NULL;
  sys_cond_broadcast (&mutex->condition);

  return result;
}

static void
lisp_mutex_destroy (lisp_mutex_t *mutex)
{
  sys_cond_destroy (&mutex->condition);
}

static int
lisp_mutex_owned_p (lisp_mutex_t *mutex)
{
  return mutex->owner == current_thread;
}

\f

DEFUN ("make-mutex", Fmake_mutex, Smake_mutex, 0, 1, 0,
       doc: /* Create a mutex.
A mutex provides a synchronization point for threads.
Only one thread at a time can hold a mutex.  Other threads attempting
to acquire it will block until the mutex is available.

A thread can acquire a mutex any number of times.

NAME, if given, is used as the name of the mutex.  The name is
informational only.  */)
  (Lisp_Object name)
{
  if (!NILP (name))
    CHECK_STRING (name);

  struct Lisp_Mutex *mutex
    = ALLOCATE_ZEROED_PSEUDOVECTOR (struct Lisp_Mutex, name, PVEC_MUTEX);
  mutex->name = name;
  lisp_mutex_init (&mutex->mutex);

  Lisp_Object result;
  XSETMUTEX (result, mutex);
  return result;
}

static void
mutex_lock_callback (void *arg)
{
  struct Lisp_Mutex *mutex = arg;
  struct thread_state *self = current_thread;

  /* Calling lisp_mutex_lock might yield to other threads while this
     one waits for the mutex to become unlocked, so we need to
     announce us as the current thread by calling
     post_acquire_global_lock.  */
  if (lisp_mutex_lock (&mutex->mutex, 0))
    post_acquire_global_lock (self);
}

static void
do_unwind_mutex_lock (void)
{
  current_thread->event_object = Qnil;
}

DEFUN ("mutex-lock", Fmutex_lock, Smutex_lock, 1, 1, 0,
       doc: /* Acquire a mutex.
If the current thread already owns MUTEX, increment the count and
return.
Otherwise, if no thread owns MUTEX, make the current thread own it.
Otherwise, block until MUTEX is available, or until the current thread
is signaled using `thread-signal'.
Note that calls to `mutex-lock' and `mutex-unlock' must be paired.  */)
  (Lisp_Object mutex)
{
  struct Lisp_Mutex *lmutex;
  ptrdiff_t count = SPECPDL_INDEX ();

  CHECK_MUTEX (mutex);
  lmutex = XMUTEX (mutex);

  current_thread->event_object = mutex;
  record_unwind_protect_void (do_unwind_mutex_lock);
  flush_stack_call_func (mutex_lock_callback, lmutex);
  return unbind_to (count, Qnil);
}

static void
mutex_unlock_callback (void *arg)
{
  struct Lisp_Mutex *mutex = arg;
  struct thread_state *self = current_thread;

  if (lisp_mutex_unlock (&mutex->mutex))
    post_acquire_global_lock (self); /* FIXME: is this call needed? */
}

DEFUN ("mutex-unlock", Fmutex_unlock, Smutex_unlock, 1, 1, 0,
       doc: /* Release the mutex.
If this thread does not own MUTEX, signal an error.
Otherwise, decrement the mutex's count.  If the count is zero,
release MUTEX.   */)
  (Lisp_Object mutex)
{
  struct Lisp_Mutex *lmutex;

  CHECK_MUTEX (mutex);
  lmutex = XMUTEX (mutex);

  flush_stack_call_func (mutex_unlock_callback, lmutex);
  return Qnil;
}

DEFUN ("mutex-name", Fmutex_name, Smutex_name, 1, 1, 0,
       doc: /* Return the name of MUTEX.
If no name was given when MUTEX was created, return nil.  */)
  (Lisp_Object mutex)
{
  struct Lisp_Mutex *lmutex;

  CHECK_MUTEX (mutex);
  lmutex = XMUTEX (mutex);

  return lmutex->name;
}

void
finalize_one_mutex (struct Lisp_Mutex *mutex)
{
  lisp_mutex_destroy (&mutex->mutex);
}

\f

DEFUN ("make-condition-variable",
       Fmake_condition_variable, Smake_condition_variable,
       1, 2, 0,
       doc: /* Make a condition variable associated with MUTEX.
A condition variable provides a way for a thread to sleep while
waiting for a state change.

MUTEX is the mutex associated with this condition variable.
NAME, if given, is the name of this condition variable.  The name is
informational only.  */)
  (Lisp_Object mutex, Lisp_Object name)
{
  CHECK_MUTEX (mutex);
  if (!NILP (name))
    CHECK_STRING (name);

  struct Lisp_CondVar *condvar
    = ALLOCATE_ZEROED_PSEUDOVECTOR (struct Lisp_CondVar, name, PVEC_CONDVAR);
  condvar->mutex = mutex;
  condvar->name = name;
  sys_cond_init (&condvar->cond);

  Lisp_Object result;
  XSETCONDVAR (result, condvar);
  return result;
}

static void
condition_wait_callback (void *arg)
{
  struct Lisp_CondVar *cvar = arg;
  struct Lisp_Mutex *mutex = XMUTEX (cvar->mutex);
  struct thread_state *self = current_thread;
  unsigned int saved_count;
  Lisp_Object cond;

  XSETCONDVAR (cond, cvar);
  self->event_object = cond;
  saved_count = lisp_mutex_unlock_for_wait (&mutex->mutex);
  /* If signaled while unlocking, skip the wait but reacquire the lock.  */
  if (NILP (self->error_symbol))
    {
      self->wait_condvar = &cvar->cond;
      /* This call could switch to another thread.  */
      sys_cond_wait (&cvar->cond, &global_lock);
      self->wait_condvar = NULL;
    }
  self->event_object = Qnil;
  /* Since sys_cond_wait could switch threads, we need to lock the
     mutex for the thread which was the current when we were called,
     otherwise lisp_mutex_lock will record the wrong thread as the
     owner of the mutex lock.  */
  lisp_mutex_lock_for_thread (&mutex->mutex, self, saved_count);
  /* Calling lisp_mutex_lock_for_thread might yield to other threads
     while this one waits for the mutex to become unlocked, so we need
     to announce us as the current thread by calling
     post_acquire_global_lock.  */
  post_acquire_global_lock (self);
}

DEFUN ("condition-wait", Fcondition_wait, Scondition_wait, 1, 1, 0,
       doc: /* Wait for the condition variable COND to be notified.
COND is the condition variable to wait on.

The mutex associated with COND must be held when this is called.
It is an error if it is not held.

This releases the mutex and waits for COND to be notified or for
this thread to be signaled with `thread-signal'.  When
`condition-wait' returns, COND's mutex will again be locked by
this thread.  */)
  (Lisp_Object cond)
{
  struct Lisp_CondVar *cvar;
  struct Lisp_Mutex *mutex;

  CHECK_CONDVAR (cond);
  cvar = XCONDVAR (cond);

  mutex = XMUTEX (cvar->mutex);
  if (!lisp_mutex_owned_p (&mutex->mutex))
    error ("Condition variable's mutex is not held by current thread");

  flush_stack_call_func (condition_wait_callback, cvar);

  return Qnil;
}

/* Used to communicate arguments to condition_notify_callback.  */
struct notify_args
{
  struct Lisp_CondVar *cvar;
  int all;
};

static void
condition_notify_callback (void *arg)
{
  struct notify_args *na = arg;
  struct Lisp_Mutex *mutex = XMUTEX (na->cvar->mutex);
  struct thread_state *self = current_thread;
  unsigned int saved_count;
  Lisp_Object cond;

  XSETCONDVAR (cond, na->cvar);
  saved_count = lisp_mutex_unlock_for_wait (&mutex->mutex);
  if (na->all)
    sys_cond_broadcast (&na->cvar->cond);
  else
    sys_cond_signal (&na->cvar->cond);
  /* Calling lisp_mutex_lock might yield to other threads while this
     one waits for the mutex to become unlocked, so we need to
     announce us as the current thread by calling
     post_acquire_global_lock.  */
  lisp_mutex_lock (&mutex->mutex, saved_count);
  post_acquire_global_lock (self);
}

DEFUN ("condition-notify", Fcondition_notify, Scondition_notify, 1, 2, 0,
       doc: /* Notify COND, a condition variable.
This wakes a thread waiting on COND.
If ALL is non-nil, all waiting threads are awoken.

The mutex associated with COND must be held when this is called.
It is an error if it is not held.

This releases COND's mutex when notifying COND.  When
`condition-notify' returns, the mutex will again be locked by this
thread.  */)
  (Lisp_Object cond, Lisp_Object all)
{
  struct Lisp_CondVar *cvar;
  struct Lisp_Mutex *mutex;
  struct notify_args args;

  CHECK_CONDVAR (cond);
  cvar = XCONDVAR (cond);

  mutex = XMUTEX (cvar->mutex);
  if (!lisp_mutex_owned_p (&mutex->mutex))
    error ("Condition variable's mutex is not held by current thread");

  args.cvar = cvar;
  args.all = !NILP (all);
  flush_stack_call_func (condition_notify_callback, &args);

  return Qnil;
}

DEFUN ("condition-mutex", Fcondition_mutex, Scondition_mutex, 1, 1, 0,
       doc: /* Return the mutex associated with condition variable COND.  */)
  (Lisp_Object cond)
{
  struct Lisp_CondVar *cvar;

  CHECK_CONDVAR (cond);
  cvar = XCONDVAR (cond);

  return cvar->mutex;
}

DEFUN ("condition-name", Fcondition_name, Scondition_name, 1, 1, 0,
       doc: /* Return the name of condition variable COND.
If no name was given when COND was created, return nil.  */)
  (Lisp_Object cond)
{
  struct Lisp_CondVar *cvar;

  CHECK_CONDVAR (cond);
  cvar = XCONDVAR (cond);

  return cvar->name;
}

void
finalize_one_condvar (struct Lisp_CondVar *condvar)
{
  sys_cond_destroy (&condvar->cond);
}

\f

struct select_args
{
  select_func *func;
  int max_fds;
  fd_set *rfds;
  fd_set *wfds;
  fd_set *efds;
  struct timespec *timeout;
  sigset_t *sigmask;
  int result;
};

static void
really_call_select (void *arg)
{
  struct select_args *sa = arg;
  struct thread_state *self = current_thread;
  sigset_t oldset;

  block_interrupt_signal (&oldset);
  self->not_holding_lock = 1;
  release_global_lock ();
  restore_signal_mask (&oldset);

  sa->result = (sa->func) (sa->max_fds, sa->rfds, sa->wfds, sa->efds,
			   sa->timeout, sa->sigmask);

  block_interrupt_signal (&oldset);
  /* If we were interrupted by C-g while inside sa->func above, the
     signal handler could have called maybe_reacquire_global_lock, in
     which case we are already holding the lock and shouldn't try
     taking it again, or else we will hang forever.  */
  if (self->not_holding_lock)
    {
      acquire_global_lock (self);
      self->not_holding_lock = 0;
    }
  restore_signal_mask (&oldset);
}

int
thread_select (select_func *func, int max_fds, fd_set *rfds,
	       fd_set *wfds, fd_set *efds, struct timespec *timeout,
	       sigset_t *sigmask)
{
  struct select_args sa;

  sa.func = func;
  sa.max_fds = max_fds;
  sa.rfds = rfds;
  sa.wfds = wfds;
  sa.efds = efds;
  sa.timeout = timeout;
  sa.sigmask = sigmask;
  flush_stack_call_func (really_call_select, &sa);
  return sa.result;
}

\f

static void
mark_one_thread (struct thread_state *thread)
{
  /* Get the stack top now, in case mark_specpdl changes it.  */
  void const *stack_top = thread->stack_top;

  mark_specpdl (thread->m_specpdl, thread->m_specpdl_ptr);

  mark_stack (thread->m_stack_bottom, stack_top);

  for (struct handler *handler = thread->m_handlerlist;
       handler; handler = handler->next)
    {
      mark_object (handler->tag_or_ch);
      mark_object (handler->val);
    }

  if (thread->m_current_buffer)
    {
      Lisp_Object tem;
      XSETBUFFER (tem, thread->m_current_buffer);
      mark_object (tem);
    }

  /* No need to mark Lisp_Object members like m_last_thing_searched,
     as mark_threads_callback does that by calling mark_object.  */
}

static void
mark_threads_callback (void *ignore)
{
  struct thread_state *iter;

  for (iter = all_threads; iter; iter = iter->next_thread)
    {
      Lisp_Object thread_obj;

      XSETTHREAD (thread_obj, iter);
      mark_object (thread_obj);
      mark_one_thread (iter);
    }
}

void
mark_threads (void)
{
  flush_stack_call_func (mark_threads_callback, NULL);
}

void
unmark_main_thread (void)
{
  main_thread.s.header.size &= ~ARRAY_MARK_FLAG;
}

\f

static void
yield_callback (void *ignore)
{
  struct thread_state *self = current_thread;

  release_global_lock ();
  sys_thread_yield ();
  acquire_global_lock (self);
}

DEFUN ("thread-yield", Fthread_yield, Sthread_yield, 0, 0, 0,
       doc: /* Yield the CPU to another thread.  */)
     (void)
{
  flush_stack_call_func (yield_callback, NULL);
  return Qnil;
}

static Lisp_Object
invoke_thread_function (void)
{
  ptrdiff_t count = SPECPDL_INDEX ();

  current_thread->result = Ffuncall (1, &current_thread->function);
  return unbind_to (count, Qnil);
}

static Lisp_Object last_thread_error;

static Lisp_Object
record_thread_error (Lisp_Object error_form)
{
  last_thread_error = error_form;
  return error_form;
}

static void *
run_thread (void *state)
{
  /* Make sure stack_top and m_stack_bottom are properly aligned as GC
     expects.  */
  union
  {
    Lisp_Object o;
    void *p;
    char c;
  } stack_pos;

  struct thread_state *self = state;
  struct thread_state **iter;

  self->m_stack_bottom = self->stack_top = &stack_pos.c;
  self->thread_id = sys_thread_self ();

  if (self->thread_name)
    sys_thread_set_name (self->thread_name);

  acquire_global_lock (self);

  /* Put a dummy catcher at top-level so that handlerlist is never NULL.
     This is important since handlerlist->nextfree holds the freelist
     which would otherwise leak every time we unwind back to top-level.   */
  handlerlist_sentinel = xzalloc (sizeof (struct handler));
  handlerlist = handlerlist_sentinel->nextfree = handlerlist_sentinel;
  struct handler *c = push_handler (Qunbound, CATCHER);
  eassert (c == handlerlist_sentinel);
  handlerlist_sentinel->nextfree = NULL;
  handlerlist_sentinel->next = NULL;

  /* It might be nice to do something with errors here.  */
  internal_condition_case (invoke_thread_function, Qt, record_thread_error);

  update_processes_for_thread_death (Fcurrent_thread ());

  xfree (self->m_specpdl - 1);
  self->m_specpdl = NULL;
  self->m_specpdl_ptr = NULL;
  self->m_specpdl_size = 0;

  {
    struct handler *c, *c_next;
    for (c = handlerlist_sentinel; c; c = c_next)
      {
	c_next = c->nextfree;
	xfree (c);
      }
  }

  xfree (self->thread_name);

  current_thread = NULL;
  sys_cond_broadcast (&self->thread_condvar);

  /* Unlink this thread from the list of all threads.  Note that we
     have to do this very late, after broadcasting our death.
     Otherwise the GC may decide to reap the thread_state object,
     leading to crashes.  */
  for (iter = &all_threads; *iter != self; iter = &(*iter)->next_thread)
    ;
  *iter = (*iter)->next_thread;

  release_global_lock ();

  return NULL;
}

static void
free_search_regs (struct re_registers *regs)
{
  if (regs->num_regs != 0)
    {
      xfree (regs->start);
      xfree (regs->end);
    }
}

void
finalize_one_thread (struct thread_state *state)
{
  free_search_regs (&state->m_search_regs);
  free_search_regs (&state->m_saved_search_regs);
  sys_cond_destroy (&state->thread_condvar);
}

DEFUN ("make-thread", Fmake_thread, Smake_thread, 1, 2, 0,
       doc: /* Start a new thread and run FUNCTION in it.
When the function exits, the thread dies.
If NAME is given, it must be a string; it names the new thread.  */)
  (Lisp_Object function, Lisp_Object name)
{
  /* Can't start a thread in temacs.  */
  if (!initialized)
    emacs_abort ();

  if (!NILP (name))
    CHECK_STRING (name);

  struct thread_state *new_thread
    = ALLOCATE_ZEROED_PSEUDOVECTOR (struct thread_state, event_object,
				    PVEC_THREAD);
  new_thread->function = function;
  new_thread->name = name;
  /* Perhaps copy m_last_thing_searched from parent?  */
  new_thread->m_current_buffer = current_thread->m_current_buffer;

  new_thread->m_specpdl_size = 50;
  new_thread->m_specpdl = xmalloc ((1 + new_thread->m_specpdl_size)
				   * sizeof (union specbinding));
  /* Skip the dummy entry.  */
  ++new_thread->m_specpdl;
  new_thread->m_specpdl_ptr = new_thread->m_specpdl;

  sys_cond_init (&new_thread->thread_condvar);

  /* We'll need locking here eventually.  */
  new_thread->next_thread = all_threads;
  all_threads = new_thread;

  char const *c_name = !NILP (name) ? SSDATA (ENCODE_SYSTEM (name)) : NULL;
  if (c_name)
    new_thread->thread_name = xstrdup (c_name);
  else
    new_thread->thread_name = NULL;
  sys_thread_t thr;
  if (! sys_thread_create (&thr, run_thread, new_thread))
    {
      /* Restore the previous situation.  */
      all_threads = all_threads->next_thread;
#ifdef THREADS_ENABLED
      error ("Could not start a new thread");
#else
      error ("Concurrency is not supported in this configuration");
#endif
    }

  /* FIXME: race here where new thread might not be filled in?  */
  Lisp_Object result;
  XSETTHREAD (result, new_thread);
  return result;
}

DEFUN ("current-thread", Fcurrent_thread, Scurrent_thread, 0, 0, 0,
       doc: /* Return the current thread.  */)
  (void)
{
  Lisp_Object result;
  XSETTHREAD (result, current_thread);
  return result;
}

DEFUN ("thread-name", Fthread_name, Sthread_name, 1, 1, 0,
       doc: /* Return the name of the THREAD.
The name is the same object that was passed to `make-thread'.  */)
     (Lisp_Object thread)
{
  struct thread_state *tstate;

  CHECK_THREAD (thread);
  tstate = XTHREAD (thread);

  return tstate->name;
}

static void
thread_signal_callback (void *arg)
{
  struct thread_state *tstate = arg;
  struct thread_state *self = current_thread;

  sys_cond_broadcast (tstate->wait_condvar);
  post_acquire_global_lock (self);
}

DEFUN ("thread-signal", Fthread_signal, Sthread_signal, 3, 3, 0,
       doc: /* Signal an error in a thread.
This acts like `signal', but arranges for the signal to be raised
in THREAD.  If THREAD is the current thread, acts just like `signal'.
This will interrupt a blocked call to `mutex-lock', `condition-wait',
or `thread-join' in the target thread.
If THREAD is the main thread, just the error message is shown.  */)
  (Lisp_Object thread, Lisp_Object error_symbol, Lisp_Object data)
{
  struct thread_state *tstate;

  CHECK_THREAD (thread);
  tstate = XTHREAD (thread);

  if (tstate == current_thread)
    Fsignal (error_symbol, data);

#ifdef THREADS_ENABLED
  if (main_thread_p (tstate))
    {
      /* Construct an event.  */
      struct input_event event;
      EVENT_INIT (event);
      event.kind = THREAD_EVENT;
      event.frame_or_window = Qnil;
      event.arg = list3 (Fcurrent_thread (), error_symbol, data);

      /* Store it into the input event queue.  */
      kbd_buffer_store_event (&event);
    }

  else
#endif
    {
      /* What to do if thread is already signaled?  */
      /* What if error_symbol is Qnil?  */
      tstate->error_symbol = error_symbol;
      tstate->error_data = data;

      if (tstate->wait_condvar)
	flush_stack_call_func (thread_signal_callback, tstate);
    }

  return Qnil;
}

DEFUN ("thread-live-p", Fthread_live_p, Sthread_live_p, 1, 1, 0,
       doc: /* Return t if THREAD is alive, or nil if it has exited.  */)
  (Lisp_Object thread)
{
  struct thread_state *tstate;

  CHECK_THREAD (thread);
  tstate = XTHREAD (thread);

  return thread_live_p (tstate) ? Qt : Qnil;
}

DEFUN ("thread--blocker", Fthread_blocker, Sthread_blocker, 1, 1, 0,
       doc: /* Return the object that THREAD is blocking on.
If THREAD is blocked in `thread-join' on a second thread, return that
thread.
If THREAD is blocked in `mutex-lock', return the mutex.
If THREAD is blocked in `condition-wait', return the condition variable.
Otherwise, if THREAD is not blocked, return nil.  */)
  (Lisp_Object thread)
{
  struct thread_state *tstate;

  CHECK_THREAD (thread);
  tstate = XTHREAD (thread);

  return tstate->event_object;
}

static void
thread_join_callback (void *arg)
{
  struct thread_state *tstate = arg;
  struct thread_state *self = current_thread;
  Lisp_Object thread;

  XSETTHREAD (thread, tstate);
  self->event_object = thread;
  self->wait_condvar = &tstate->thread_condvar;
  while (thread_live_p (tstate) && NILP (self->error_symbol))
    sys_cond_wait (self->wait_condvar, &global_lock);

  self->wait_condvar = NULL;
  self->event_object = Qnil;
  post_acquire_global_lock (self);
}

DEFUN ("thread-join", Fthread_join, Sthread_join, 1, 1, 0,
       doc: /* Wait for THREAD to exit.
This blocks the current thread until THREAD exits or until the current
thread is signaled.  It returns the result of the THREAD function.  It
is an error for a thread to try to join itself.  */)
  (Lisp_Object thread)
{
  struct thread_state *tstate;
  Lisp_Object error_symbol, error_data;

  CHECK_THREAD (thread);
  tstate = XTHREAD (thread);

  if (tstate == current_thread)
    error ("Cannot join current thread");

  error_symbol = tstate->error_symbol;
  error_data = tstate->error_data;

  if (thread_live_p (tstate))
    flush_stack_call_func (thread_join_callback, tstate);

  if (!NILP (error_symbol))
    Fsignal (error_symbol, error_data);

  return tstate->result;
}

DEFUN ("all-threads", Fall_threads, Sall_threads, 0, 0, 0,
       doc: /* Return a list of all the live threads.  */)
  (void)
{
  Lisp_Object result = Qnil;
  struct thread_state *iter;

  for (iter = all_threads; iter; iter = iter->next_thread)
    {
      if (thread_live_p (iter))
	{
	  Lisp_Object thread;

	  XSETTHREAD (thread, iter);
	  result = Fcons (thread, result);
	}
    }

  return result;
}

DEFUN ("thread-last-error", Fthread_last_error, Sthread_last_error, 0, 1, 0,
       doc: /* Return the last error form recorded by a dying thread.
If CLEANUP is non-nil, remove this error form from history.  */)
     (Lisp_Object cleanup)
{
  Lisp_Object result = last_thread_error;

  if (!NILP (cleanup))
    last_thread_error = Qnil;

  return result;
}

\f

bool
thread_check_current_buffer (struct buffer *buffer)
{
  struct thread_state *iter;

  for (iter = all_threads; iter; iter = iter->next_thread)
    {
      if (iter == current_thread)
	continue;

      if (iter->m_current_buffer == buffer)
	return true;
    }

  return false;
}

\f

bool
main_thread_p (const void *ptr)
{
  return ptr == &main_thread.s;
}

bool
in_current_thread (void)
{
  if (current_thread == NULL)
    return false;
  return sys_thread_equal (sys_thread_self (), current_thread->thread_id);
}

void
init_threads (void)
{
  sys_cond_init (&main_thread.s.thread_condvar);
  sys_mutex_init (&global_lock);
  sys_mutex_lock (&global_lock);
  current_thread = &main_thread.s;
  main_thread.s.thread_id = sys_thread_self ();
}

void
syms_of_threads (void)
{
#ifndef THREADS_ENABLED
  if (0)
#endif
    {
      defsubr (&Sthread_yield);
      defsubr (&Smake_thread);
      defsubr (&Scurrent_thread);
      defsubr (&Sthread_name);
      defsubr (&Sthread_signal);
      defsubr (&Sthread_live_p);
      defsubr (&Sthread_join);
      defsubr (&Sthread_blocker);
      defsubr (&Sall_threads);
      defsubr (&Smake_mutex);
      defsubr (&Smutex_lock);
      defsubr (&Smutex_unlock);
      defsubr (&Smutex_name);
      defsubr (&Smake_condition_variable);
      defsubr (&Scondition_wait);
      defsubr (&Scondition_notify);
      defsubr (&Scondition_mutex);
      defsubr (&Scondition_name);
      defsubr (&Sthread_last_error);

      staticpro (&last_thread_error);
      last_thread_error = Qnil;

      Fprovide (intern_c_string ("threads"), Qnil);
    }

  DEFSYM (Qthreadp, "threadp");
  DEFSYM (Qmutexp, "mutexp");
  DEFSYM (Qcondition_variable_p, "condition-variable-p");

  DEFVAR_LISP ("main-thread", Vmain_thread,
    doc: /* The main thread of Emacs.  */);
#ifdef THREADS_ENABLED
  XSETTHREAD (Vmain_thread, &main_thread.s);
#else
  Vmain_thread = Qnil;
#endif
}

debug log:

solving b638dd77f8 ...
found b638dd77f8 in https://git.savannah.gnu.org/cgit/emacs.git

(*) Git path names are given by the tree(s) the blob belongs to.
    Blobs themselves have no identifier aside from the hash of its contents.^

Code repositories for project(s) associated with this public inbox

	https://git.savannah.gnu.org/cgit/emacs.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).