-
Notifications
You must be signed in to change notification settings - Fork 42
/
Copy pathpthread_stop_world.c
1264 lines (1142 loc) · 42.9 KB
/
pthread_stop_world.c
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
/*
* Copyright (c) 1994 by Xerox Corporation. All rights reserved.
* Copyright (c) 1996 by Silicon Graphics. All rights reserved.
* Copyright (c) 1998 by Fergus Henderson. All rights reserved.
* Copyright (c) 2000-2009 by Hewlett-Packard Development Company.
* All rights reserved.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
#include "private/pthread_support.h"
#if defined(GC_PTHREADS) && !defined(GC_WIN32_THREADS) && \
!defined(GC_DARWIN_THREADS) && !defined(SN_TARGET_ORBIS) \
&& !defined(SN_TARGET_PSP2)
#ifdef NACL
# include <unistd.h>
# include <sys/time.h>
STATIC int GC_nacl_num_gc_threads = 0;
STATIC __thread int GC_nacl_thread_idx = -1;
STATIC volatile int GC_nacl_park_threads_now = 0;
STATIC volatile pthread_t GC_nacl_thread_parker = -1;
GC_INNER __thread GC_thread GC_nacl_gc_thread_self = NULL;
volatile int GC_nacl_thread_parked[MAX_NACL_GC_THREADS];
int GC_nacl_thread_used[MAX_NACL_GC_THREADS];
#elif defined(GC_OPENBSD_UTHREADS)
# include <pthread_np.h>
#else /* !GC_OPENBSD_UTHREADS && !NACL */
#include <signal.h>
#include <semaphore.h>
#include <errno.h>
#include <time.h> /* for nanosleep() */
#include <unistd.h>
#if (!defined(AO_HAVE_load_acquire) || !defined(AO_HAVE_store_release)) \
&& !defined(CPPCHECK)
# error AO_load_acquire and/or AO_store_release are missing;
# error please define AO_REQUIRE_CAS manually
#endif
/* It's safe to call original pthread_sigmask() here. */
#undef pthread_sigmask
#ifdef GC_ENABLE_SUSPEND_THREAD
static void *GC_CALLBACK suspend_self_inner(void *client_data);
#endif
#ifdef DEBUG_THREADS
# ifndef NSIG
# if defined(MAXSIG)
# define NSIG (MAXSIG+1)
# elif defined(_NSIG)
# define NSIG _NSIG
# elif defined(__SIGRTMAX)
# define NSIG (__SIGRTMAX+1)
# else
# error define NSIG
# endif
# endif /* NSIG */
void GC_print_sig_mask(void)
{
sigset_t blocked;
int i;
if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
ABORT("pthread_sigmask failed");
for (i = 1; i < NSIG; i++) {
if (sigismember(&blocked, i))
GC_printf("Signal blocked: %d\n", i);
}
}
#endif /* DEBUG_THREADS */
/* Remove the signals that we want to allow in thread stopping */
/* handler from a set. */
STATIC void GC_remove_allowed_signals(sigset_t *set)
{
if (sigdelset(set, SIGINT) != 0
|| sigdelset(set, SIGQUIT) != 0
|| sigdelset(set, SIGABRT) != 0
|| sigdelset(set, SIGTERM) != 0) {
ABORT("sigdelset failed");
}
# ifdef MPROTECT_VDB
/* Handlers write to the thread structure, which is in the heap, */
/* and hence can trigger a protection fault. */
if (sigdelset(set, SIGSEGV) != 0
# ifdef HAVE_SIGBUS
|| sigdelset(set, SIGBUS) != 0
# endif
) {
ABORT("sigdelset failed");
}
# endif
}
static sigset_t suspend_handler_mask;
STATIC volatile AO_t GC_stop_count = 0;
/* Incremented by two at the beginning of */
/* GC_stop_world (the lowest bit is always 0). */
STATIC volatile AO_t GC_world_is_stopped = FALSE;
/* FALSE ==> it is safe for threads to restart, */
/* i.e. they will see another suspend signal */
/* before they are expected to stop (unless */
/* they have stopped voluntarily). */
#if defined(GC_OSF1_THREADS) || defined(THREAD_SANITIZER) \
|| defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER)
STATIC GC_bool GC_retry_signals = TRUE;
#else
STATIC GC_bool GC_retry_signals = FALSE;
#endif
/*
* We use signals to stop threads during GC.
*
* Suspended threads wait in signal handler for SIG_THR_RESTART.
* That's more portable than semaphores or condition variables.
* (We do use sem_post from a signal handler, but that should be portable.)
*
* The thread suspension signal SIG_SUSPEND is now defined in gc_priv.h.
* Note that we can't just stop a thread; we need it to save its stack
* pointer(s) and acknowledge.
*/
#ifndef SIG_THR_RESTART
# if defined(GC_HPUX_THREADS) || defined(GC_OSF1_THREADS) \
|| defined(GC_NETBSD_THREADS) || defined(GC_USESIGRT_SIGNALS)
# if defined(_SIGRTMIN) && !defined(CPPCHECK)
# define SIG_THR_RESTART _SIGRTMIN + 5
# else
# define SIG_THR_RESTART SIGRTMIN + 5
# endif
# else
# define SIG_THR_RESTART SIGXCPU
# endif
#endif
#define SIGNAL_UNSET (-1)
/* Since SIG_SUSPEND and/or SIG_THR_RESTART could represent */
/* a non-constant expression (e.g., in case of SIGRTMIN), */
/* actual signal numbers are determined by GC_stop_init() */
/* unless manually set (before GC initialization). */
STATIC int GC_sig_suspend = SIGNAL_UNSET;
STATIC int GC_sig_thr_restart = SIGNAL_UNSET;
GC_API void GC_CALL GC_set_suspend_signal(int sig)
{
if (GC_is_initialized) return;
GC_sig_suspend = sig;
}
GC_API void GC_CALL GC_set_thr_restart_signal(int sig)
{
if (GC_is_initialized) return;
GC_sig_thr_restart = sig;
}
GC_API int GC_CALL GC_get_suspend_signal(void)
{
return GC_sig_suspend != SIGNAL_UNSET ? GC_sig_suspend : SIG_SUSPEND;
}
GC_API int GC_CALL GC_get_thr_restart_signal(void)
{
return GC_sig_thr_restart != SIGNAL_UNSET
? GC_sig_thr_restart : SIG_THR_RESTART;
}
#if defined(GC_EXPLICIT_SIGNALS_UNBLOCK) \
|| !defined(NO_SIGNALS_UNBLOCK_IN_MAIN)
/* Some targets (e.g., Solaris) might require this to be called when */
/* doing thread registering from the thread destructor. */
GC_INNER void GC_unblock_gc_signals(void)
{
sigset_t set;
sigemptyset(&set);
GC_ASSERT(GC_sig_suspend != SIGNAL_UNSET);
GC_ASSERT(GC_sig_thr_restart != SIGNAL_UNSET);
sigaddset(&set, GC_sig_suspend);
sigaddset(&set, GC_sig_thr_restart);
if (pthread_sigmask(SIG_UNBLOCK, &set, NULL) != 0)
ABORT("pthread_sigmask failed");
}
#endif /* GC_EXPLICIT_SIGNALS_UNBLOCK */
STATIC sem_t GC_suspend_ack_sem; /* also used to acknowledge restart */
STATIC void GC_suspend_handler_inner(ptr_t dummy, void *context);
#ifndef NO_SA_SIGACTION
STATIC void GC_suspend_handler(int sig, siginfo_t * info GC_ATTR_UNUSED,
void * context GC_ATTR_UNUSED)
#else
STATIC void GC_suspend_handler(int sig)
#endif
{
int old_errno = errno;
if (sig != GC_sig_suspend) {
# if defined(GC_FREEBSD_THREADS)
/* Workaround "deferred signal handling" bug in FreeBSD 9.2. */
if (0 == sig) return;
# endif
ABORT("Bad signal in suspend_handler");
}
# if defined(IA64) || defined(HP_PA) || defined(M68K)
GC_with_callee_saves_pushed(GC_suspend_handler_inner, NULL);
# else
/* We believe that in all other cases the full context is already */
/* in the signal handler frame. */
{
# ifdef NO_SA_SIGACTION
void *context = 0;
# endif
GC_suspend_handler_inner(NULL, context);
}
# endif
errno = old_errno;
}
/* The lookup here is safe, since this is done on behalf */
/* of a thread which holds the allocation lock in order */
/* to stop the world. Thus concurrent modification of the */
/* data structure is impossible. Unfortunately, we have to */
/* instruct TSan that the lookup is safe. */
#ifdef THREAD_SANITIZER
/* The implementation of the function is the same as that of */
/* GC_lookup_thread except for the attribute added here. */
GC_ATTR_NO_SANITIZE_THREAD
static GC_thread GC_lookup_thread_async(pthread_t id)
{
GC_thread p = GC_threads[THREAD_TABLE_INDEX(id)];
while (p != NULL && !THREAD_EQUAL(p->id, id))
p = p->next;
return p;
}
#else
# define GC_lookup_thread_async GC_lookup_thread
#endif
GC_INLINE void GC_store_stack_ptr(GC_thread me)
{
/* There is no data race between the suspend handler (storing */
/* stack_ptr) and GC_push_all_stacks (fetching stack_ptr) because */
/* GC_push_all_stacks is executed after GC_stop_world exits and the */
/* latter runs sem_wait repeatedly waiting for all the suspended */
/* threads to call sem_post. Nonetheless, stack_ptr is stored (here) */
/* and fetched (by GC_push_all_stacks) using the atomic primitives to */
/* avoid the related TSan warning. */
# ifdef SPARC
AO_store((volatile AO_t *)&me->stop_info.stack_ptr,
(AO_t)GC_save_regs_in_stack());
# else
# ifdef IA64
me -> backing_store_ptr = GC_save_regs_in_stack();
# endif
AO_store((volatile AO_t *)&me->stop_info.stack_ptr, (AO_t)GC_approx_sp());
# endif
}
STATIC void GC_suspend_handler_inner(ptr_t dummy GC_ATTR_UNUSED,
void * context GC_ATTR_UNUSED)
{
pthread_t self = pthread_self();
GC_thread me;
IF_CANCEL(int cancel_state;)
AO_t my_stop_count = AO_load_acquire(&GC_stop_count);
/* After the barrier, this thread should see */
/* the actual content of GC_threads. */
DISABLE_CANCEL(cancel_state);
/* pthread_setcancelstate is not defined to be async-signal-safe. */
/* But the glibc version appears to be in the absence of */
/* asynchronous cancellation. And since this signal handler */
/* to block on sigsuspend, which is both async-signal-safe */
/* and a cancellation point, there seems to be no obvious way */
/* out of it. In fact, it looks to me like an async-signal-safe */
/* cancellation point is inherently a problem, unless there is */
/* some way to disable cancellation in the handler. */
# ifdef DEBUG_THREADS
GC_log_printf("Suspending %p\n", (void *)self);
# endif
GC_ASSERT(((word)my_stop_count & 1) == 0);
me = GC_lookup_thread_async(self);
# ifdef GC_ENABLE_SUSPEND_THREAD
if (AO_load(&me->suspended_ext)) {
GC_store_stack_ptr(me);
sem_post(&GC_suspend_ack_sem);
suspend_self_inner(me);
# ifdef DEBUG_THREADS
GC_log_printf("Continuing %p on GC_resume_thread\n", (void *)self);
# endif
RESTORE_CANCEL(cancel_state);
return;
}
# endif
if (((word)me->stop_info.last_stop_count & ~(word)0x1)
== (word)my_stop_count) {
/* Duplicate signal. OK if we are retrying. */
if (!GC_retry_signals) {
WARN("Duplicate suspend signal in thread %p\n", self);
}
RESTORE_CANCEL(cancel_state);
return;
}
GC_store_stack_ptr(me);
# ifdef THREAD_SANITIZER
/* TSan disables signals around signal handlers. Without */
/* a pthread_sigmask call, sigsuspend may block forever. */
{
sigset_t set;
sigemptyset(&set);
GC_ASSERT(GC_sig_suspend != SIGNAL_UNSET);
GC_ASSERT(GC_sig_thr_restart != SIGNAL_UNSET);
sigaddset(&set, GC_sig_suspend);
sigaddset(&set, GC_sig_thr_restart);
if (pthread_sigmask(SIG_UNBLOCK, &set, NULL) != 0)
ABORT("pthread_sigmask failed in suspend handler");
}
# endif
/* Tell the thread that wants to stop the world that this */
/* thread has been stopped. Note that sem_post() is */
/* the only async-signal-safe primitive in LinuxThreads. */
sem_post(&GC_suspend_ack_sem);
AO_store_release(&me->stop_info.last_stop_count, my_stop_count);
/* Wait until that thread tells us to restart by sending */
/* this thread a GC_sig_thr_restart signal (should be masked */
/* at this point thus there is no race). */
/* We do not continue until we receive that signal, */
/* but we do not take that as authoritative. (We may be */
/* accidentally restarted by one of the user signals we */
/* don't block.) After we receive the signal, we use a */
/* primitive and expensive mechanism to wait until it's */
/* really safe to proceed. Under normal circumstances, */
/* this code should not be executed. */
do {
sigsuspend (&suspend_handler_mask);
} while (AO_load_acquire(&GC_world_is_stopped)
&& AO_load(&GC_stop_count) == my_stop_count);
# ifdef DEBUG_THREADS
GC_log_printf("Continuing %p\n", (void *)self);
# endif
# ifndef GC_NETBSD_THREADS_WORKAROUND
if (GC_retry_signals)
# endif
{
/* If the RESTART signal loss is possible (though it should be */
/* less likely than losing the SUSPEND signal as we do not do */
/* much between the first sem_post and sigsuspend calls), more */
/* handshaking is provided to work around it. */
sem_post(&GC_suspend_ack_sem);
# ifdef GC_NETBSD_THREADS_WORKAROUND
if (GC_retry_signals)
# endif
{
/* Set the flag (the lowest bit of last_stop_count) that the */
/* thread has been restarted. */
AO_store_release(&me->stop_info.last_stop_count,
(AO_t)((word)my_stop_count | 1));
}
}
RESTORE_CANCEL(cancel_state);
}
static void suspend_restart_barrier(int n_live_threads)
{
int i;
for (i = 0; i < n_live_threads; i++) {
while (0 != sem_wait(&GC_suspend_ack_sem)) {
/* On Linux, sem_wait is documented to always return zero. */
/* But the documentation appears to be incorrect. */
/* EINTR seems to happen with some versions of gdb. */
if (errno != EINTR)
ABORT("sem_wait failed");
}
}
# ifdef GC_ASSERTIONS
sem_getvalue(&GC_suspend_ack_sem, &i);
GC_ASSERT(0 == i);
# endif
}
static int resend_lost_signals(int n_live_threads,
int (*suspend_restart_all)(void))
{
# define WAIT_UNIT 3000
# define RETRY_INTERVAL 100000
if (n_live_threads > 0) {
unsigned long wait_usecs = 0; /* Total wait since retry. */
for (;;) {
int ack_count;
sem_getvalue(&GC_suspend_ack_sem, &ack_count);
if (ack_count == n_live_threads)
break;
if (wait_usecs > RETRY_INTERVAL) {
int newly_sent = suspend_restart_all();
GC_COND_LOG_PRINTF("Resent %d signals after timeout\n", newly_sent);
sem_getvalue(&GC_suspend_ack_sem, &ack_count);
if (newly_sent < n_live_threads - ack_count) {
WARN("Lost some threads while stopping or starting world?!\n", 0);
n_live_threads = ack_count + newly_sent;
}
wait_usecs = 0;
}
# ifdef LINT2
/* Workaround "waiting while holding a lock" warning. */
# undef WAIT_UNIT
# define WAIT_UNIT 1
sched_yield();
# elif defined(CPPCHECK) /* || _POSIX_C_SOURCE >= 199309L */
{
struct timespec ts;
ts.tv_sec = 0;
ts.tv_nsec = WAIT_UNIT * 1000;
(void)nanosleep(&ts, NULL);
}
# else
usleep(WAIT_UNIT);
# endif
wait_usecs += WAIT_UNIT;
}
}
return n_live_threads;
}
STATIC void GC_restart_handler(int sig)
{
# if defined(DEBUG_THREADS)
int old_errno = errno; /* Preserve errno value. */
# endif
if (sig != GC_sig_thr_restart)
ABORT("Bad signal in restart handler");
/*
** Note: even if we don't do anything useful here,
** it would still be necessary to have a signal handler,
** rather than ignoring the signals, otherwise
** the signals will not be delivered at all, and
** will thus not interrupt the sigsuspend() above.
*/
# ifdef DEBUG_THREADS
GC_log_printf("In GC_restart_handler for %p\n", (void *)pthread_self());
errno = old_errno;
# endif
}
# ifdef USE_TKILL_ON_ANDROID
EXTERN_C_BEGIN
extern int tkill(pid_t tid, int sig); /* from sys/linux-unistd.h */
EXTERN_C_END
static int android_thread_kill(pid_t tid, int sig)
{
int ret;
int old_errno = errno;
ret = tkill(tid, sig);
if (ret < 0) {
ret = errno;
errno = old_errno;
}
return ret;
}
# define THREAD_SYSTEM_ID(t) (t)->kernel_id
# define RAISE_SIGNAL(t, sig) android_thread_kill(THREAD_SYSTEM_ID(t), sig)
# else
# define THREAD_SYSTEM_ID(t) (t)->id
# define RAISE_SIGNAL(t, sig) pthread_kill(THREAD_SYSTEM_ID(t), sig)
# endif /* !USE_TKILL_ON_ANDROID */
# ifdef GC_ENABLE_SUSPEND_THREAD
# include <sys/time.h>
# include "javaxfc.h" /* to get the prototypes as extern "C" */
STATIC void GC_brief_async_signal_safe_sleep(void)
{
struct timeval tv;
tv.tv_sec = 0;
# if defined(GC_TIME_LIMIT) && !defined(CPPCHECK)
tv.tv_usec = 1000 * GC_TIME_LIMIT / 2;
# else
tv.tv_usec = 1000 * 50 / 2;
# endif
(void)select(0, 0, 0, 0, &tv);
}
static void *GC_CALLBACK suspend_self_inner(void *client_data) {
GC_thread me = (GC_thread)client_data;
while (AO_load_acquire(&me->suspended_ext)) {
/* TODO: Use sigsuspend() instead. */
GC_brief_async_signal_safe_sleep();
}
return NULL;
}
GC_API void GC_CALL GC_suspend_thread(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
IF_CANCEL(int cancel_state;)
DCL_LOCK_STATE;
LOCK();
t = GC_lookup_thread((pthread_t)thread);
if (t == NULL || t -> suspended_ext) {
UNLOCK();
return;
}
/* Set the flag making the change visible to the signal handler. */
AO_store_release(&t->suspended_ext, TRUE);
if (THREAD_EQUAL((pthread_t)thread, pthread_self())) {
UNLOCK();
/* It is safe as "t" cannot become invalid here (no race with */
/* GC_unregister_my_thread). */
(void)GC_do_blocking(suspend_self_inner, t);
return;
}
if ((t -> flags & FINISHED) != 0) {
/* Terminated but not joined yet. */
UNLOCK();
return;
}
DISABLE_CANCEL(cancel_state);
/* GC_suspend_thread is not a cancellation point. */
# ifdef PARALLEL_MARK
/* Ensure we do not suspend a thread while it is rebuilding */
/* a free list, otherwise such a dead-lock is possible: */
/* thread 1 is blocked in GC_wait_for_reclaim holding */
/* the allocation lock, thread 2 is suspended in */
/* GC_reclaim_generic invoked from GC_generic_malloc_many */
/* (with GC_fl_builder_count > 0), and thread 3 is blocked */
/* acquiring the allocation lock in GC_resume_thread. */
if (GC_parallel)
GC_wait_for_reclaim();
# endif
if (GC_manual_vdb) {
/* See the relevant comment in GC_stop_world. */
GC_acquire_dirty_lock();
}
/* Else do not acquire the lock as the write fault handler might */
/* be trying to acquire this lock too, and the suspend handler */
/* execution is deferred until the write fault handler completes. */
/* TODO: Support GC_retry_signals (not needed for TSan) */
switch (RAISE_SIGNAL(t, GC_sig_suspend)) {
/* ESRCH cannot happen as terminated threads are handled above. */
case 0:
break;
default:
ABORT("pthread_kill failed");
}
/* Wait for the thread to complete threads table lookup and */
/* stack_ptr assignment. */
GC_ASSERT(GC_thr_initialized);
while (sem_wait(&GC_suspend_ack_sem) != 0) {
if (errno != EINTR)
ABORT("sem_wait for handler failed (suspend_self)");
}
if (GC_manual_vdb)
GC_release_dirty_lock();
RESTORE_CANCEL(cancel_state);
UNLOCK();
}
GC_API void GC_CALL GC_resume_thread(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
DCL_LOCK_STATE;
LOCK();
t = GC_lookup_thread((pthread_t)thread);
if (t != NULL)
AO_store(&t->suspended_ext, FALSE);
UNLOCK();
}
GC_API int GC_CALL GC_is_thread_suspended(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
int is_suspended = 0;
DCL_LOCK_STATE;
LOCK();
t = GC_lookup_thread((pthread_t)thread);
if (t != NULL && t -> suspended_ext)
is_suspended = (int)TRUE;
UNLOCK();
return is_suspended;
}
# endif /* GC_ENABLE_SUSPEND_THREAD */
#endif /* !GC_OPENBSD_UTHREADS && !NACL */
#ifdef IA64
# define IF_IA64(x) x
#else
# define IF_IA64(x)
#endif
/* We hold allocation lock. Should do exactly the right thing if the */
/* world is stopped. Should not fail if it isn't. */
GC_INNER void GC_push_all_stacks(void)
{
GC_bool found_me = FALSE;
size_t nthreads = 0;
int i;
GC_thread p;
ptr_t lo, hi;
/* On IA64, we also need to scan the register backing store. */
IF_IA64(ptr_t bs_lo; ptr_t bs_hi;)
struct GC_traced_stack_sect_s *traced_stack_sect;
pthread_t self = pthread_self();
word total_size = 0;
if (!EXPECT(GC_thr_initialized, TRUE))
GC_thr_init();
# ifdef DEBUG_THREADS
GC_log_printf("Pushing stacks from thread %p\n", (void *)self);
# endif
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> flags & FINISHED) continue;
++nthreads;
traced_stack_sect = p -> traced_stack_sect;
if (THREAD_EQUAL(p -> id, self)) {
GC_ASSERT(!p->thread_blocked);
# ifdef SPARC
lo = (ptr_t)GC_save_regs_in_stack();
# else
lo = GC_approx_sp();
# endif
found_me = TRUE;
IF_IA64(bs_hi = (ptr_t)GC_save_regs_in_stack();)
} else {
lo = (ptr_t)AO_load((volatile AO_t *)&p->stop_info.stack_ptr);
IF_IA64(bs_hi = p -> backing_store_ptr;)
if (traced_stack_sect != NULL
&& traced_stack_sect->saved_stack_ptr == lo) {
/* If the thread has never been stopped since the recent */
/* GC_call_with_gc_active invocation then skip the top */
/* "stack section" as stack_ptr already points to. */
traced_stack_sect = traced_stack_sect->prev;
}
}
if ((p -> flags & MAIN_THREAD) == 0) {
hi = p -> stack_end;
IF_IA64(bs_lo = p -> backing_store_end);
} else {
/* The original stack. */
hi = GC_stackbottom;
IF_IA64(bs_lo = BACKING_STORE_BASE;)
}
# ifdef DEBUG_THREADS
GC_log_printf("Stack for thread %p = [%p,%p)\n",
(void *)p->id, (void *)lo, (void *)hi);
# endif
if (0 == lo) ABORT("GC_push_all_stacks: sp not set!");
if (p->altstack != NULL && (word)p->altstack <= (word)lo
&& (word)lo <= (word)p->altstack + p->altstack_size) {
hi = p->altstack + p->altstack_size;
/* FIXME: Need to scan the normal stack too, but how ? */
/* FIXME: Assume stack grows down */
}
GC_push_all_stack_sections(lo, hi, traced_stack_sect);
# ifdef STACK_GROWS_UP
total_size += lo - hi;
# else
total_size += hi - lo; /* lo <= hi */
# endif
# ifdef NACL
/* Push reg_storage as roots, this will cover the reg context. */
GC_push_all_stack((ptr_t)p -> stop_info.reg_storage,
(ptr_t)(p -> stop_info.reg_storage + NACL_GC_REG_STORAGE_SIZE));
total_size += NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t);
# endif
# ifdef IA64
# ifdef DEBUG_THREADS
GC_log_printf("Reg stack for thread %p = [%p,%p)\n",
(void *)p->id, (void *)bs_lo, (void *)bs_hi);
# endif
/* FIXME: This (if p->id==self) may add an unbounded number of */
/* entries, and hence overflow the mark stack, which is bad. */
GC_push_all_register_sections(bs_lo, bs_hi,
THREAD_EQUAL(p -> id, self),
traced_stack_sect);
total_size += bs_hi - bs_lo; /* bs_lo <= bs_hi */
# endif
}
}
GC_VERBOSE_LOG_PRINTF("Pushed %d thread stacks\n", (int)nthreads);
if (!found_me && !GC_in_thread_creation)
ABORT("Collecting from unknown thread");
GC_total_stacksize = total_size;
}
#ifdef DEBUG_THREADS
/* There seems to be a very rare thread stopping problem. To help us */
/* debug that, we save the ids of the stopping thread. */
pthread_t GC_stopping_thread;
int GC_stopping_pid = 0;
#endif
/* We hold the allocation lock. Suspend all threads that might */
/* still be running. Return the number of suspend signals that */
/* were sent. */
STATIC int GC_suspend_all(void)
{
int n_live_threads = 0;
int i;
# ifndef NACL
GC_thread p;
# ifndef GC_OPENBSD_UTHREADS
int result;
# endif
pthread_t self = pthread_self();
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (!THREAD_EQUAL(p -> id, self)) {
if ((p -> flags & FINISHED) != 0) continue;
if (p -> thread_blocked) /* Will wait */ continue;
# ifndef GC_OPENBSD_UTHREADS
# ifdef GC_ENABLE_SUSPEND_THREAD
if (p -> suspended_ext) continue;
# endif
if (AO_load(&p->stop_info.last_stop_count) == GC_stop_count)
continue; /* matters only if GC_retry_signals */
n_live_threads++;
# endif
# ifdef DEBUG_THREADS
GC_log_printf("Sending suspend signal to %p\n", (void *)p->id);
# endif
# ifdef GC_OPENBSD_UTHREADS
{
stack_t stack;
GC_acquire_dirty_lock();
if (pthread_suspend_np(p -> id) != 0)
ABORT("pthread_suspend_np failed");
GC_release_dirty_lock();
if (pthread_stackseg_np(p->id, &stack))
ABORT("pthread_stackseg_np failed");
p -> stop_info.stack_ptr = (ptr_t)stack.ss_sp - stack.ss_size;
if (GC_on_thread_event)
GC_on_thread_event(GC_EVENT_THREAD_SUSPENDED,
(void *)p->id);
}
# else
/* The synchronization between GC_dirty (based on */
/* test-and-set) and the signal-based thread suspension */
/* is performed in GC_stop_world because */
/* GC_release_dirty_lock cannot be called before */
/* acknowledging the thread is really suspended. */
result = RAISE_SIGNAL(p, GC_sig_suspend);
switch(result) {
case ESRCH:
/* Not really there anymore. Possible? */
n_live_threads--;
break;
case 0:
if (GC_on_thread_event)
GC_on_thread_event(GC_EVENT_THREAD_SUSPENDED,
(void *)(word)THREAD_SYSTEM_ID(p));
/* Note: thread id might be truncated. */
break;
default:
ABORT_ARG1("pthread_kill failed at suspend",
": errcode= %d", result);
}
# endif
}
}
}
# else /* NACL */
# ifndef NACL_PARK_WAIT_NANOSECONDS
# define NACL_PARK_WAIT_NANOSECONDS (100 * 1000)
# endif
# define NANOS_PER_SECOND (1000UL * 1000 * 1000)
unsigned long num_sleeps = 0;
# ifdef DEBUG_THREADS
GC_log_printf("pthread_stop_world: num_threads=%d\n",
GC_nacl_num_gc_threads - 1);
# endif
GC_nacl_thread_parker = pthread_self();
GC_nacl_park_threads_now = 1;
if (GC_manual_vdb)
GC_acquire_dirty_lock();
while (1) {
int num_threads_parked = 0;
struct timespec ts;
int num_used = 0;
/* Check the 'parked' flag for each thread the GC knows about. */
for (i = 0; i < MAX_NACL_GC_THREADS
&& num_used < GC_nacl_num_gc_threads; i++) {
if (GC_nacl_thread_used[i] == 1) {
num_used++;
if (GC_nacl_thread_parked[i] == 1) {
num_threads_parked++;
if (GC_on_thread_event)
GC_on_thread_event(GC_EVENT_THREAD_SUSPENDED, (void *)(word)i);
}
}
}
/* -1 for the current thread. */
if (num_threads_parked >= GC_nacl_num_gc_threads - 1)
break;
ts.tv_sec = 0;
ts.tv_nsec = NACL_PARK_WAIT_NANOSECONDS;
# ifdef DEBUG_THREADS
GC_log_printf("Sleep waiting for %d threads to park...\n",
GC_nacl_num_gc_threads - num_threads_parked - 1);
# endif
/* This requires _POSIX_TIMERS feature. */
nanosleep(&ts, 0);
if (++num_sleeps > NANOS_PER_SECOND / NACL_PARK_WAIT_NANOSECONDS) {
WARN("GC appears stalled waiting for %" WARN_PRIdPTR
" threads to park...\n",
GC_nacl_num_gc_threads - num_threads_parked - 1);
num_sleeps = 0;
}
}
if (GC_manual_vdb)
GC_release_dirty_lock();
# endif /* NACL */
return n_live_threads;
}
GC_INNER void GC_stop_world(void)
{
# if !defined(GC_OPENBSD_UTHREADS) && !defined(NACL)
int n_live_threads;
# endif
GC_ASSERT(I_HOLD_LOCK());
# ifdef DEBUG_THREADS
GC_stopping_thread = pthread_self();
GC_stopping_pid = getpid();
GC_log_printf("Stopping the world from %p\n", (void *)GC_stopping_thread);
# endif
/* Make sure all free list construction has stopped before we start. */
/* No new construction can start, since free list construction is */
/* required to acquire and release the GC lock before it starts, */
/* and we have the lock. */
# ifdef PARALLEL_MARK
if (GC_parallel) {
GC_acquire_mark_lock();
GC_ASSERT(GC_fl_builder_count == 0);
/* We should have previously waited for it to become zero. */
}
# endif /* PARALLEL_MARK */
# if defined(GC_OPENBSD_UTHREADS) || defined(NACL)
(void)GC_suspend_all();
# else
AO_store(&GC_stop_count, (AO_t)((word)GC_stop_count + 2));
/* Only concurrent reads are possible. */
if (GC_manual_vdb) {
GC_acquire_dirty_lock();
/* The write fault handler cannot be called if GC_manual_vdb */
/* (thus double-locking should not occur in */
/* async_set_pht_entry_from_index based on test-and-set). */
}
AO_store_release(&GC_world_is_stopped, TRUE);
n_live_threads = GC_suspend_all();
if (GC_retry_signals)
n_live_threads = resend_lost_signals(n_live_threads, GC_suspend_all);
suspend_restart_barrier(n_live_threads);
if (GC_manual_vdb)
GC_release_dirty_lock(); /* cannot be done in GC_suspend_all */
# endif
# ifdef PARALLEL_MARK
if (GC_parallel)
GC_release_mark_lock();
# endif
# ifdef DEBUG_THREADS
GC_log_printf("World stopped from %p\n", (void *)pthread_self());
GC_stopping_thread = 0;
# endif
}
#ifdef NACL
# if defined(__x86_64__)
# define NACL_STORE_REGS() \
do { \
__asm__ __volatile__ ("push %rbx"); \
__asm__ __volatile__ ("push %rbp"); \
__asm__ __volatile__ ("push %r12"); \
__asm__ __volatile__ ("push %r13"); \
__asm__ __volatile__ ("push %r14"); \
__asm__ __volatile__ ("push %r15"); \
__asm__ __volatile__ ("mov %%esp, %0" \
: "=m" (GC_nacl_gc_thread_self->stop_info.stack_ptr)); \
BCOPY(GC_nacl_gc_thread_self->stop_info.stack_ptr, \
GC_nacl_gc_thread_self->stop_info.reg_storage, \
NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t)); \
__asm__ __volatile__ ("naclasp $48, %r15"); \
} while (0)
# elif defined(__i386__)
# define NACL_STORE_REGS() \
do { \
__asm__ __volatile__ ("push %ebx"); \
__asm__ __volatile__ ("push %ebp"); \
__asm__ __volatile__ ("push %esi"); \
__asm__ __volatile__ ("push %edi"); \
__asm__ __volatile__ ("mov %%esp, %0" \
: "=m" (GC_nacl_gc_thread_self->stop_info.stack_ptr)); \
BCOPY(GC_nacl_gc_thread_self->stop_info.stack_ptr, \
GC_nacl_gc_thread_self->stop_info.reg_storage, \
NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t));\
__asm__ __volatile__ ("add $16, %esp"); \
} while (0)
# elif defined(__arm__)
# define NACL_STORE_REGS() \
do { \
__asm__ __volatile__ ("push {r4-r8,r10-r12,lr}"); \
__asm__ __volatile__ ("mov r0, %0" \
: : "r" (&GC_nacl_gc_thread_self->stop_info.stack_ptr)); \
__asm__ __volatile__ ("bic r0, r0, #0xc0000000"); \
__asm__ __volatile__ ("str sp, [r0]"); \
BCOPY(GC_nacl_gc_thread_self->stop_info.stack_ptr, \
GC_nacl_gc_thread_self->stop_info.reg_storage, \
NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t)); \
__asm__ __volatile__ ("add sp, sp, #40"); \
__asm__ __volatile__ ("bic sp, sp, #0xc0000000"); \
} while (0)
# else
# error TODO Please port NACL_STORE_REGS
# endif
GC_API_OSCALL void nacl_pre_syscall_hook(void)
{
if (GC_nacl_thread_idx != -1) {
NACL_STORE_REGS();
GC_nacl_gc_thread_self->stop_info.stack_ptr = GC_approx_sp();
GC_nacl_thread_parked[GC_nacl_thread_idx] = 1;
}
}
GC_API_OSCALL void __nacl_suspend_thread_if_needed(void)
{
if (GC_nacl_park_threads_now) {
pthread_t self = pthread_self();
/* Don't try to park the thread parker. */
if (GC_nacl_thread_parker == self)
return;
/* This can happen when a thread is created outside of the GC */
/* system (wthread mostly). */
if (GC_nacl_thread_idx < 0)
return;
/* If it was already 'parked', we're returning from a syscall, */
/* so don't bother storing registers again, the GC has a set. */
if (!GC_nacl_thread_parked[GC_nacl_thread_idx]) {