summaryrefslogtreecommitdiff
path: root/mjit.c
blob: beb59d96468932dd2d5c2ea4b8b3a63e42ae1c99 (plain)
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
/**********************************************************************

  mjit.c - MRI method JIT compiler functions for Ruby's main thread

  Copyright (C) 2017 Vladimir Makarov <vmakarov@redhat.com>.

**********************************************************************/

/* Functions in this file are never executed on MJIT worker thread.
   So you can safely use Ruby methods and GC in this file. */

/* To share variables privately, include mjit_worker.c instead of linking. */
#include "mjit_worker.c"

#include "constant.h"
#include "id_table.h"

extern int rb_thread_create_mjit_thread(void (*worker_func)(void));

/* Return an unique file name in /tmp with PREFIX and SUFFIX and
   number ID.  Use getpid if ID == 0.  The return file name exists
   until the next function call.  */
static char *
get_uniq_filename(unsigned long id, const char *prefix, const char *suffix)
{
    char buff[70], *str = buff;
    int size = sprint_uniq_filename(buff, sizeof(buff), id, prefix, suffix);
    str = 0;
    ++size;
    str = xmalloc(size);
    if (size <= (int)sizeof(buff)) {
        memcpy(str, buff, size);
    }
    else {
        sprint_uniq_filename(str, size, id, prefix, suffix);
    }
    return str;
}

/* Wait until workers don't compile any iseq.  It is called at the
   start of GC.  */
void
mjit_gc_start_hook(void)
{
    if (!mjit_enabled)
        return;
    CRITICAL_SECTION_START(4, "mjit_gc_start_hook");
    while (in_jit) {
        verbose(4, "Waiting wakeup from a worker for GC");
        rb_native_cond_wait(&mjit_client_wakeup, &mjit_engine_mutex);
        verbose(4, "Getting wakeup from a worker for GC");
    }
    in_gc = TRUE;
    CRITICAL_SECTION_FINISH(4, "mjit_gc_start_hook");
}

/* Send a signal to workers to continue iseq compilations.  It is
   called at the end of GC.  */
void
mjit_gc_finish_hook(void)
{
    if (!mjit_enabled)
        return;
    CRITICAL_SECTION_START(4, "mjit_gc_finish_hook");
    in_gc = FALSE;
    verbose(4, "Sending wakeup signal to workers after GC");
    rb_native_cond_broadcast(&mjit_gc_wakeup);
    CRITICAL_SECTION_FINISH(4, "mjit_gc_finish_hook");
}

/* Iseqs can be garbage collected.  This function should call when it
   happens.  It removes iseq from the unit.  */
void
mjit_free_iseq(const rb_iseq_t *iseq)
{
    if (!mjit_enabled)
        return;
    CRITICAL_SECTION_START(4, "mjit_free_iseq");
    if (iseq->body->jit_unit) {
        /* jit_unit is not freed here because it may be referred by multiple
           lists of units. `get_from_list` and `mjit_finish` do the job. */
        iseq->body->jit_unit->iseq = NULL;
    }
    CRITICAL_SECTION_FINISH(4, "mjit_free_iseq");
}

/* Do we need this...? */
static void
init_list(struct rb_mjit_unit_list *list)
{
    list->head = NULL;
    list->length = 0;
}

/* Free unit list. This should be called only when worker is finished
   because node of unit_queue and one of active_units may have the same unit
   during proceeding unit. */
static void
free_list(struct rb_mjit_unit_list *list)
{
    struct rb_mjit_unit_node *node, *next;
    for (node = list->head; node != NULL; node = next) {
        next = node->next;
        free_unit(node->unit);
        xfree(node);
    }
}

/* MJIT info related to an existing continutaion.  */
struct mjit_cont {
    rb_execution_context_t *ec; /* continuation ec */
    struct mjit_cont *prev, *next; /* used to form lists */
};

/* Double linked list of registered continuations. This is used to detect
   units which are in use in unload_units. */
static struct mjit_cont *first_cont;

/* Register a new continuation with thread TH.  Return MJIT info about
   the continuation.  */
struct mjit_cont *
mjit_cont_new(rb_execution_context_t *ec)
{
    struct mjit_cont *cont;

    cont = ZALLOC(struct mjit_cont);
    cont->ec = ec;

    CRITICAL_SECTION_START(3, "in mjit_cont_new");
    if (first_cont == NULL) {
        cont->next = cont->prev = NULL;
    }
    else {
        cont->prev = NULL;
        cont->next = first_cont;
        first_cont->prev = cont;
    }
    first_cont = cont;
    CRITICAL_SECTION_FINISH(3, "in mjit_cont_new");

    return cont;
}

/* Unregister continuation CONT.  */
void
mjit_cont_free(struct mjit_cont *cont)
{
    CRITICAL_SECTION_START(3, "in mjit_cont_new");
    if (cont == first_cont) {
        first_cont = cont->next;
        if (first_cont != NULL)
            first_cont->prev = NULL;
    }
    else {
        cont->prev->next = cont->next;
        if (cont->next != NULL)
            cont->next->prev = cont->prev;
    }
    CRITICAL_SECTION_FINISH(3, "in mjit_cont_new");

    xfree(cont);
}

/* Finish work with continuation info. */
static void
finish_conts(void)
{
    struct mjit_cont *cont, *next;

    for (cont = first_cont; cont != NULL; cont = next) {
        next = cont->next;
        xfree(cont);
    }
}

/* Create unit for ISEQ. */
static void
create_unit(const rb_iseq_t *iseq)
{
    struct rb_mjit_unit *unit;

    unit = ZALLOC(struct rb_mjit_unit);
    if (unit == NULL)
        return;

    unit->id = current_unit_num++;
    unit->iseq = iseq;
    iseq->body->jit_unit = unit;
}

/* Set up field used_code_p for unit iseqs whose iseq on the stack of ec. */
static void
mark_ec_units(rb_execution_context_t *ec)
{
    const rb_control_frame_t *cfp;

    if (ec->vm_stack == NULL)
        return;
    for (cfp = RUBY_VM_END_CONTROL_FRAME(ec) - 1; ; cfp = RUBY_VM_NEXT_CONTROL_FRAME(cfp)) {
        const rb_iseq_t *iseq;
        if (cfp->pc && (iseq = cfp->iseq) != NULL
            && imemo_type((VALUE) iseq) == imemo_iseq
            && (iseq->body->jit_unit) != NULL) {
            iseq->body->jit_unit->used_code_p = TRUE;
        }

        if (cfp == ec->cfp)
            break; /* reached the most recent cfp */
    }
}

/* Unload JIT code of some units to satisfy the maximum permitted
   number of units with a loaded code.  */
static void
unload_units(void)
{
    rb_vm_t *vm = GET_THREAD()->vm;
    rb_thread_t *th = NULL;
    struct rb_mjit_unit_node *node, *next, *worst_node;
    struct mjit_cont *cont;
    int delete_num, units_num = active_units.length;

    /* For now, we don't unload units when ISeq is GCed. We should
       unload such ISeqs first here. */
    for (node = active_units.head; node != NULL; node = next) {
        next = node->next;
        if (node->unit->iseq == NULL) { /* ISeq is GCed. */
            free_unit(node->unit);
            remove_from_list(node, &active_units);
        }
    }

    /* Detect units which are in use and can't be unloaded. */
    for (node = active_units.head; node != NULL; node = node->next) {
        assert(node->unit != NULL && node->unit->iseq != NULL && node->unit->handle != NULL);
        node->unit->used_code_p = FALSE;
    }
    list_for_each(&vm->living_threads, th, vmlt_node) {
        mark_ec_units(th->ec);
    }
    for (cont = first_cont; cont != NULL; cont = cont->next) {
        mark_ec_units(cont->ec);
    }

    /* Remove 1/10 units more to decrease unloading calls.  */
    /* TODO: Calculate max total_calls in unit_queue and don't unload units
       whose total_calls are larger than the max. */
    delete_num = active_units.length / 10;
    for (; active_units.length > mjit_opts.max_cache_size - delete_num;) {
        /* Find one unit that has the minimum total_calls. */
        worst_node = NULL;
        for (node = active_units.head; node != NULL; node = node->next) {
            if (node->unit->used_code_p) /* We can't unload code on stack. */
                continue;

            if (worst_node == NULL || worst_node->unit->iseq->body->total_calls > node->unit->iseq->body->total_calls) {
                worst_node = node;
            }
        }
        if (worst_node == NULL)
            break;

        /* Unload the worst node. */
        verbose(2, "Unloading unit %d (calls=%lu)", worst_node->unit->id, worst_node->unit->iseq->body->total_calls);
        assert(worst_node->unit->handle != NULL);
        free_unit(worst_node->unit);
        remove_from_list(worst_node, &active_units);
    }
    verbose(1, "Too many JIT code -- %d units unloaded", units_num - active_units.length);
}

/* Add ISEQ to be JITed in parallel with the current thread.
   Unload some JIT codes if there are too many of them.  */
void
mjit_add_iseq_to_process(const rb_iseq_t *iseq)
{
    struct rb_mjit_unit_node *node;

    if (!mjit_enabled || pch_status == PCH_FAILED)
        return;

    iseq->body->jit_func = (mjit_func_t)NOT_READY_JIT_ISEQ_FUNC;
    create_unit(iseq);
    if (iseq->body->jit_unit == NULL)
        /* Failure in creating the unit.  */
        return;

    node = create_list_node(iseq->body->jit_unit);
    if (node == NULL) {
        mjit_warning("failed to allocate a node to be added to unit_queue");
        return;
    }

    CRITICAL_SECTION_START(3, "in add_iseq_to_process");
    add_to_list(node, &unit_queue);
    if (active_units.length >= mjit_opts.max_cache_size) {
        unload_units();
    }
    verbose(3, "Sending wakeup signal to workers in mjit_add_iseq_to_process");
    rb_native_cond_broadcast(&mjit_worker_wakeup);
    CRITICAL_SECTION_FINISH(3, "in add_iseq_to_process");
}

/* For this timeout seconds, --jit-wait will wait for JIT compilation finish. */
#define MJIT_WAIT_TIMEOUT_SECONDS 60

/* Wait for JIT compilation finish for --jit-wait. This should only return a function pointer
   or NOT_COMPILED_JIT_ISEQ_FUNC. */
mjit_func_t
mjit_get_iseq_func(struct rb_iseq_constant_body *body)
{
    struct timeval tv;
    int tries = 0;
    tv.tv_sec = 0;
    tv.tv_usec = 1000;
    while (body->jit_func == (mjit_func_t)NOT_READY_JIT_ISEQ_FUNC) {
        tries++;
        if (tries / 1000 > MJIT_WAIT_TIMEOUT_SECONDS || pch_status == PCH_FAILED) {
            CRITICAL_SECTION_START(3, "in mjit_get_iseq_func to set jit_func");
            body->jit_func = (mjit_func_t)NOT_COMPILED_JIT_ISEQ_FUNC; /* JIT worker seems dead. Give up. */
            CRITICAL_SECTION_FINISH(3, "in mjit_get_iseq_func to set jit_func");
            mjit_warning("timed out to wait for JIT finish");
            break;
        }

        CRITICAL_SECTION_START(3, "in mjit_get_iseq_func for a client wakeup");
        rb_native_cond_broadcast(&mjit_worker_wakeup);
        CRITICAL_SECTION_FINISH(3, "in mjit_get_iseq_func for a client wakeup");
        rb_thread_wait_for(tv);
    }
    return body->jit_func;
}

extern VALUE ruby_archlibdir_path, ruby_prefix_path;

/* Initialize header_file, pch_file, libruby_pathflag. Return TRUE on success. */
static int
init_header_filename(void)
{
    int fd;
    /* Root path of the running ruby process. Equal to RbConfig::TOPDIR.  */
    VALUE basedir_val;
    const char *basedir;
    size_t baselen;
    char *p;
#ifdef _WIN32
    static const char libpathflag[] =
# ifdef _MSC_VER
        "-LIBPATH:"
# else
        "-L"
# endif
        ;
    const size_t libpathflag_len = sizeof(libpathflag) - 1;
#endif

    basedir_val = ruby_prefix_path;
    basedir = StringValuePtr(basedir_val);
    baselen = RSTRING_LEN(basedir_val);

#ifndef LOAD_RELATIVE
    if (getenv("MJIT_SEARCH_BUILD_DIR")) {
        /* This path is not intended to be used on production, but using build directory's
           header file here because people want to run `make test-all` without running
           `make install`. Don't use $MJIT_SEARCH_BUILD_DIR except for test-all. */
        basedir = MJIT_BUILD_DIR;
        baselen = strlen(basedir);
    }
#endif

#ifndef _MSC_VER
    {
        /* A name of the header file included in any C file generated by MJIT for iseqs. */
        static const char header_name[] = MJIT_MIN_HEADER_NAME;
        const size_t header_name_len = sizeof(header_name) - 1;

        header_file = xmalloc(baselen + header_name_len + 1);
        p = append_str2(header_file, basedir, baselen);
        p = append_str2(p, header_name, header_name_len + 1);
        if ((fd = rb_cloexec_open(header_file, O_RDONLY, 0)) < 0) {
            verbose(1, "Cannot access header file: %s", header_file);
            xfree(header_file);
            header_file = NULL;
            return FALSE;
        }
        (void)close(fd);
    }

    pch_file = get_uniq_filename(0, MJIT_TMP_PREFIX "h", ".h.gch");
    if (pch_file == NULL)
        return FALSE;
#else
    {
        static const char pch_name[] = MJIT_PRECOMPILED_HEADER_NAME;
        const size_t pch_name_len = sizeof(pch_name) - 1;

        pch_file = xmalloc(baselen + pch_name_len + 1);
        p = append_str2(pch_file, basedir, baselen);
        p = append_str2(p, pch_name, pch_name_len + 1);
        if ((fd = rb_cloexec_open(pch_file, O_RDONLY, 0)) < 0) {
            verbose(1, "Cannot access precompiled header file: %s", pch_file);
            xfree(pch_file);
            pch_file = NULL;
            return FALSE;
        }
        (void)close(fd);
    }
#endif

#ifdef _WIN32
    basedir_val = ruby_archlibdir_path;
    basedir = StringValuePtr(basedir_val);
    baselen = RSTRING_LEN(basedir_val);
    libruby_pathflag = p = xmalloc(libpathflag_len + baselen + 1);
    p = append_str(p, libpathflag);
    p = append_str2(p, basedir, baselen);
    *p = '\0';
#endif

    return TRUE;
}

/* This is called after each fork in the child in to switch off MJIT
   engine in the child as it does not inherit MJIT threads.  */
void
mjit_child_after_fork(void)
{
    if (mjit_enabled) {
        verbose(3, "Switching off MJIT in a forked child");
        mjit_enabled = FALSE;
    }
    /* TODO: Should we initiate MJIT in the forked Ruby.  */
}

static enum rb_id_table_iterator_result
valid_class_serials_add_i(ID key, VALUE v, void *unused)
{
    rb_const_entry_t *ce = (rb_const_entry_t *)v;
    VALUE value = ce->value;

    if (!rb_is_const_id(key)) return ID_TABLE_CONTINUE;
    if (RB_TYPE_P(value, T_MODULE) || RB_TYPE_P(value, T_CLASS)) {
        mjit_add_class_serial(RCLASS_SERIAL(value));
    }
    return ID_TABLE_CONTINUE;
}

#ifdef _WIN32
UINT rb_w32_system_tmpdir(WCHAR *path, UINT len);
#endif

static char *
system_default_tmpdir(void)
{
    /* c.f. ext/etc/etc.c:etc_systmpdir() */
#ifdef _WIN32
    WCHAR tmppath[_MAX_PATH];
    UINT len = rb_w32_system_tmpdir(tmppath, numberof(tmppath));
    if (len) {
        int blen = WideCharToMultiByte(CP_UTF8, 0, tmppath, len, NULL, 0, NULL, NULL);
        char *tmpdir = xmalloc(blen + 1);
        WideCharToMultiByte(CP_UTF8, 0, tmppath, len, tmpdir, blen, NULL, NULL);
        tmpdir[blen] = '\0';
        return tmpdir;
    }
#elif defined _CS_DARWIN_USER_TEMP_DIR
    char path[MAXPATHLEN];
    size_t len = confstr(_CS_DARWIN_USER_TEMP_DIR, path, sizeof(path));
    if (len > 0) {
        char *tmpdir = xmalloc(len);
        if (len > sizeof(path)) {
            confstr(_CS_DARWIN_USER_TEMP_DIR, tmpdir, len);
        }
        else {
            memcpy(tmpdir, path, len);
        }
        return tmpdir;
    }
#endif
    return 0;
}

static int
check_tmpdir(const char *dir)
{
    struct stat st;

    if (!dir) return FALSE;
    if (stat(dir, &st)) return FALSE;
#ifndef S_ISDIR
#   define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
#endif
    if (!S_ISDIR(st.st_mode)) return FALSE;
#ifndef _WIN32
# ifndef S_IWOTH
#   define S_IWOTH 002
# endif
    if (st.st_mode & S_IWOTH) {
# ifdef S_ISVTX
        if (!(st.st_mode & S_ISVTX)) return FALSE;
# else
        return FALSE;
# endif
    }
    if (access(dir, W_OK)) return FALSE;
#endif
    return TRUE;
}

static char *
system_tmpdir(void)
{
    char *tmpdir;
# define RETURN_ENV(name) \
    if (check_tmpdir(tmpdir = getenv(name))) return ruby_strdup(tmpdir)
    RETURN_ENV("TMPDIR");
    RETURN_ENV("TMP");
    tmpdir = system_default_tmpdir();
    if (check_tmpdir(tmpdir)) return tmpdir;
    return ruby_strdup("/tmp");
# undef RETURN_ENV
}

/* Default permitted number of units with a JIT code kept in
   memory.  */
#define DEFAULT_CACHE_SIZE 1000
/* A default threshold used to add iseq to JIT. */
#define DEFAULT_MIN_CALLS_TO_ADD 5
/* Minimum value for JIT cache size.  */
#define MIN_CACHE_SIZE 10

/* Start MJIT worker. Return TRUE if worker is sucessfully started. */
static int
start_worker(void)
{
    stop_worker_p = FALSE;
    worker_stopped = FALSE;

    if (!rb_thread_create_mjit_thread(mjit_worker)) {
        mjit_enabled = FALSE;
        rb_native_mutex_destroy(&mjit_engine_mutex);
        rb_native_cond_destroy(&mjit_pch_wakeup);
        rb_native_cond_destroy(&mjit_client_wakeup);
        rb_native_cond_destroy(&mjit_worker_wakeup);
        rb_native_cond_destroy(&mjit_gc_wakeup);
        verbose(1, "Failure in MJIT thread initialization\n");
        return FALSE;
    }
    return TRUE;
}

/* Initialize MJIT.  Start a thread creating the precompiled header and
   processing ISeqs.  The function should be called first for using MJIT.
   If everything is successfull, MJIT_INIT_P will be TRUE.  */
void
mjit_init(struct mjit_options *opts)
{
    mjit_opts = *opts;
    mjit_enabled = TRUE;
    mjit_call_p = TRUE;

    /* Normalize options */
    if (mjit_opts.min_calls == 0)
        mjit_opts.min_calls = DEFAULT_MIN_CALLS_TO_ADD;
    if (mjit_opts.max_cache_size <= 0)
        mjit_opts.max_cache_size = DEFAULT_CACHE_SIZE;
    if (mjit_opts.max_cache_size < MIN_CACHE_SIZE)
        mjit_opts.max_cache_size = MIN_CACHE_SIZE;

    verbose(2, "MJIT: CC defaults to %s", CC_PATH);

    /* Initialize variables for compilation */
#ifdef _MSC_VER
    pch_status = PCH_SUCCESS; /* has prebuilt precompiled header */
#else
    pch_status = PCH_NOT_READY;
#endif
    cc_path = CC_PATH;

    tmp_dir = system_tmpdir();
    verbose(2, "MJIT: tmp_dir is %s", tmp_dir);

    if (!init_header_filename()) {
        mjit_enabled = FALSE;
        verbose(1, "Failure in MJIT header file name initialization\n");
        return;
    }

    init_list(&unit_queue);
    init_list(&active_units);
    init_list(&compact_units);

    /* Initialize mutex */
    rb_native_mutex_initialize(&mjit_engine_mutex);
    rb_native_cond_initialize(&mjit_pch_wakeup);
    rb_native_cond_initialize(&mjit_client_wakeup);
    rb_native_cond_initialize(&mjit_worker_wakeup);
    rb_native_cond_initialize(&mjit_gc_wakeup);

    /* Initialize class_serials cache for compilation */
    valid_class_serials = rb_hash_new();
    rb_obj_hide(valid_class_serials);
    rb_gc_register_mark_object(valid_class_serials);
    mjit_add_class_serial(RCLASS_SERIAL(rb_cObject));
    mjit_add_class_serial(RCLASS_SERIAL(CLASS_OF(rb_vm_top_self())));
    if (RCLASS_CONST_TBL(rb_cObject)) {
        rb_id_table_foreach(RCLASS_CONST_TBL(rb_cObject), valid_class_serials_add_i, NULL);
    }

    /* Initialize worker thread */
    start_worker();
}

static void
stop_worker(void)
{
    rb_execution_context_t *ec = GET_EC();

    stop_worker_p = TRUE;
    while (!worker_stopped) {
        verbose(3, "Sending cancel signal to worker");
        CRITICAL_SECTION_START(3, "in stop_worker");
        rb_native_cond_broadcast(&mjit_worker_wakeup);
        CRITICAL_SECTION_FINISH(3, "in stop_worker");
        RUBY_VM_CHECK_INTS(ec);
    }
}

/* Stop JIT-compiling methods but compiled code is kept available. */
VALUE
mjit_pause(int wait_p)
{
    if (!mjit_enabled) {
        rb_raise(rb_eRuntimeError, "MJIT is not enabled");
    }
    if (worker_stopped) {
        return Qfalse;
    }

    /* Flush all queued units with no option or `wait: true` */
    if (wait_p) {
        struct timeval tv;
        tv.tv_sec = 0;
        tv.tv_usec = 1000;

        while (unit_queue.length > 0) {
            CRITICAL_SECTION_START(3, "in mjit_pause for a worker wakeup");
            rb_native_cond_broadcast(&mjit_worker_wakeup);
            CRITICAL_SECTION_FINISH(3, "in mjit_pause for a worker wakeup");
            rb_thread_wait_for(tv);
        }
    }

    stop_worker();
    return Qtrue;
}

/* Restart JIT-compiling methods after mjit_pause. */
VALUE
mjit_resume(void)
{
    if (!mjit_enabled) {
        rb_raise(rb_eRuntimeError, "MJIT is not enabled");
    }
    if (!worker_stopped) {
        return Qfalse;
    }

    if (!start_worker()) {
        rb_raise(rb_eRuntimeError, "Failed to resume MJIT worker");
    }
    return Qtrue;
}

/* Finish the threads processing units and creating PCH, finalize
   and free MJIT data.  It should be called last during MJIT
   life.  */
void
mjit_finish(void)
{
    if (!mjit_enabled)
        return;

    /* Wait for pch finish */
    verbose(2, "Stopping worker thread");
    CRITICAL_SECTION_START(3, "in mjit_finish to wakeup from pch");
    /* As our threads are detached, we could just cancel them.  But it
       is a bad idea because OS processes (C compiler) started by
       threads can produce temp files.  And even if the temp files are
       removed, the used C compiler still complaint about their
       absence.  So wait for a clean finish of the threads.  */
    while (pch_status == PCH_NOT_READY) {
        verbose(3, "Waiting wakeup from make_pch");
        rb_native_cond_wait(&mjit_pch_wakeup, &mjit_engine_mutex);
    }
    CRITICAL_SECTION_FINISH(3, "in mjit_finish to wakeup from pch");

    /* Stop worker */
    stop_worker();

    rb_native_mutex_destroy(&mjit_engine_mutex);
    rb_native_cond_destroy(&mjit_pch_wakeup);
    rb_native_cond_destroy(&mjit_client_wakeup);
    rb_native_cond_destroy(&mjit_worker_wakeup);
    rb_native_cond_destroy(&mjit_gc_wakeup);

#ifndef _MSC_VER /* mswin has prebuilt precompiled header */
    if (!mjit_opts.save_temps)
        remove_file(pch_file);

    xfree(header_file); header_file = NULL;
#endif
    xfree(tmp_dir); tmp_dir = NULL;
    xfree(pch_file); pch_file = NULL;

    mjit_call_p = FALSE;
    free_list(&unit_queue);
    free_list(&active_units);
    free_list(&compact_units);
    finish_conts();

    mjit_enabled = FALSE;
    verbose(1, "Successful MJIT finish");
}

void
mjit_mark(void)
{
    struct rb_mjit_unit_node *node;
    if (!mjit_enabled)
        return;
    RUBY_MARK_ENTER("mjit");
    CRITICAL_SECTION_START(4, "mjit_mark");
    for (node = unit_queue.head; node != NULL; node = node->next) {
        if (node->unit->iseq) { /* ISeq is still not GCed */
            VALUE iseq = (VALUE)node->unit->iseq;
            CRITICAL_SECTION_FINISH(4, "mjit_mark rb_gc_mark");

            /* Don't wrap critical section with this. This may trigger GC,
               and in that case mjit_gc_start_hook causes deadlock. */
            rb_gc_mark(iseq);

            CRITICAL_SECTION_START(4, "mjit_mark rb_gc_mark");
        }
    }
    CRITICAL_SECTION_FINISH(4, "mjit_mark");
    RUBY_MARK_LEAVE("mjit");
}

/* A hook to update valid_class_serials. */
void
mjit_add_class_serial(rb_serial_t class_serial)
{
    if (!mjit_enabled)
        return;

    /* Do not wrap CRITICAL_SECTION here. This function is only called in main thread
       and guarded by GVL, and `rb_hash_aset` may cause GC and deadlock in it. */
    rb_hash_aset(valid_class_serials, LONG2FIX(class_serial), Qtrue);
}

/* A hook to update valid_class_serials. */
void
mjit_remove_class_serial(rb_serial_t class_serial)
{
    if (!mjit_enabled)
        return;

    CRITICAL_SECTION_START(3, "in mjit_remove_class_serial");
    rb_hash_delete_entry(valid_class_serials, LONG2FIX(class_serial));
    CRITICAL_SECTION_FINISH(3, "in mjit_remove_class_serial");
}