1 #include "private/pthread_support.h"
3 #if defined(GC_PTHREADS) && !defined(GC_SOLARIS_THREADS) \
4 && !defined(GC_WIN32_THREADS) && !defined(GC_DARWIN_THREADS)
12 # include <sys/select.h>
13 /* Doesn't exist on HP/UX 11.11. */
22 # define NSIG (MAXSIG+1)
25 # elif defined(__SIGRTMAX)
26 # define NSIG (__SIGRTMAX+1)
32 void GC_print_sig_mask()
37 if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
38 ABORT("pthread_sigmask");
39 GC_printf0("Blocked: ");
40 for (i = 1; i < NSIG; i++) {
41 if (sigismember(&blocked, i)) { GC_printf1("%ld ",(long) i); }
48 /* Remove the signals that we want to allow in thread stopping */
49 /* handler from a set. */
50 void GC_remove_allowed_signals(sigset_t *set)
53 if (sigdelset(set, SIGINT) != 0
54 || sigdelset(set, SIGQUIT) != 0
55 || sigdelset(set, SIGABRT) != 0
56 || sigdelset(set, SIGTERM) != 0) {
57 ABORT("sigdelset() failed");
62 /* Handlers write to the thread structure, which is in the heap, */
63 /* and hence can trigger a protection fault. */
64 if (sigdelset(set, SIGSEGV) != 0
66 || sigdelset(set, SIGBUS) != 0
69 ABORT("sigdelset() failed");
74 static sigset_t suspend_handler_mask;
76 volatile sig_atomic_t GC_stop_count;
77 /* Incremented at the beginning of GC_stop_world. */
79 volatile sig_atomic_t GC_world_is_stopped = FALSE;
80 /* FALSE ==> it is safe for threads to restart, i.e. */
81 /* they will see another suspend signal before they */
82 /* are expected to stop (unless they have voluntarily */
85 void GC_brief_async_signal_safe_sleep()
89 tv.tv_usec = 1000 * TIME_LIMIT / 2;
90 select(0, 0, 0, 0, &tv);
93 #ifdef GC_OSF1_THREADS
94 GC_bool GC_retry_signals = TRUE;
96 GC_bool GC_retry_signals = FALSE;
100 * We use signals to stop threads during GC.
102 * Suspended threads wait in signal handler for SIG_THR_RESTART.
103 * That's more portable than semaphores or condition variables.
104 * (We do use sem_post from a signal handler, but that should be portable.)
106 * The thread suspension signal SIG_SUSPEND is now defined in gc_priv.h.
107 * Note that we can't just stop a thread; we need it to save its stack
108 * pointer(s) and acknowledge.
111 #ifndef SIG_THR_RESTART
112 # if defined(GC_HPUX_THREADS) || defined(GC_OSF1_THREADS)
114 # define SIG_THR_RESTART _SIGRTMIN + 5
116 # define SIG_THR_RESTART SIGRTMIN + 5
119 # define SIG_THR_RESTART SIGXCPU
123 sem_t GC_suspend_ack_sem;
125 void GC_suspend_handler_inner(ptr_t sig_arg);
127 #if defined(IA64) || defined(HP_PA) || defined(M68K)
128 extern void GC_with_callee_saves_pushed();
130 void GC_suspend_handler(int sig)
132 GC_thread me = GC_lookup_thread (pthread_self());
133 if (me -> flags & SUSPENDED)
136 int old_errno = errno;
137 GC_with_callee_saves_pushed(GC_suspend_handler_inner, (ptr_t)(word)sig);
143 /* We believe that in all other cases the full context is already */
144 /* in the signal handler frame. */
145 void GC_suspend_handler(int sig)
147 GC_thread me = GC_lookup_thread(pthread_self());
148 if (me -> flags & SUSPENDED)
151 int old_errno = errno;
152 GC_suspend_handler_inner((ptr_t)(word)sig);
158 void GC_suspend_handler_inner(ptr_t sig_arg)
160 int sig = (int)(word)sig_arg;
162 pthread_t my_thread = pthread_self();
164 # ifdef PARALLEL_MARK
165 word my_mark_no = GC_mark_no;
166 /* Marker can't proceed until we acknowledge. Thus this is */
167 /* guaranteed to be the mark_no correspending to our */
168 /* suspension, i.e. the marker can't have incremented it yet. */
170 word my_stop_count = GC_stop_count;
172 if (sig != SIG_SUSPEND) ABORT("Bad signal in suspend_handler");
175 GC_printf1("Suspending 0x%lx\n", my_thread);
178 me = GC_lookup_thread(my_thread);
179 /* The lookup here is safe, since I'm doing this on behalf */
180 /* of a thread which holds the allocation lock in order */
181 /* to stop the world. Thus concurrent modification of the */
182 /* data structure is impossible. */
183 if (me -> stop_info.last_stop_count == my_stop_count) {
184 /* Duplicate signal. OK if we are retrying. */
185 if (!GC_retry_signals) {
186 WARN("Duplicate suspend signal in thread %lx\n",
192 me -> stop_info.stack_ptr = (ptr_t)GC_save_regs_in_stack();
194 me -> stop_info.stack_ptr = (ptr_t)(&dummy);
197 me -> backing_store_ptr = (ptr_t)GC_save_regs_in_stack();
200 /* Tell the thread that wants to stop the world that this */
201 /* thread has been stopped. Note that sem_post() is */
202 /* the only async-signal-safe primitive in LinuxThreads. */
203 sem_post(&GC_suspend_ack_sem);
204 me -> stop_info.last_stop_count = my_stop_count;
206 /* Wait until that thread tells us to restart by sending */
207 /* this thread a SIG_THR_RESTART signal. */
208 /* SIG_THR_RESTART should be masked at this point. Thus there */
210 /* We do not continue until we receive a SIG_THR_RESTART, */
211 /* but we do not take that as authoritative. (We may be */
212 /* accidentally restarted by one of the user signals we */
213 /* don't block.) After we receive the signal, we use a */
214 /* primitive and expensive mechanism to wait until it's */
215 /* really safe to proceed. Under normal circumstances, */
216 /* this code should not be executed. */
217 sigsuspend(&suspend_handler_mask); /* Wait for signal */
218 while (GC_world_is_stopped && GC_stop_count == my_stop_count) {
219 GC_brief_async_signal_safe_sleep();
221 GC_err_printf0("Sleeping in signal handler");
224 /* If the RESTART signal gets lost, we can still lose. That should be */
225 /* less likely than losing the SUSPEND signal, since we don't do much */
226 /* between the sem_post and sigsuspend. */
227 /* We'd need more handshaking to work around that. */
228 /* Simply dropping the sigsuspend call should be safe, but is unlikely */
229 /* to be efficient. */
232 GC_printf1("Continuing 0x%lx\n", my_thread);
236 void GC_restart_handler(int sig)
238 pthread_t my_thread = pthread_self();
240 if (sig != SIG_THR_RESTART) ABORT("Bad signal in suspend_handler");
243 ** Note: even if we don't do anything useful here,
244 ** it would still be necessary to have a signal handler,
245 ** rather than ignoring the signals, otherwise
246 ** the signals will not be delivered at all, and
247 ** will thus not interrupt the sigsuspend() above.
251 GC_printf1("In GC_restart_handler for 0x%lx\n", pthread_self());
256 # define IF_IA64(x) x
260 /* We hold allocation lock. Should do exactly the right thing if the */
261 /* world is stopped. Should not fail if it isn't. */
262 void GC_push_all_stacks()
264 GC_bool found_me = FALSE;
268 /* On IA64, we also need to scan the register backing store. */
269 IF_IA64(ptr_t bs_lo; ptr_t bs_hi;)
270 pthread_t me = pthread_self();
272 if (!GC_thr_initialized) GC_thr_init();
274 GC_printf1("Pushing stacks from thread 0x%lx\n", (unsigned long) me);
276 for (i = 0; i < THREAD_TABLE_SZ; i++) {
277 for (p = GC_threads[i]; p != 0; p = p -> next) {
278 if (p -> flags & FINISHED) continue;
279 if (pthread_equal(p -> id, me)) {
281 lo = (ptr_t)GC_save_regs_in_stack();
286 IF_IA64(bs_hi = (ptr_t)GC_save_regs_in_stack();)
288 lo = p -> stop_info.stack_ptr;
289 IF_IA64(bs_hi = p -> backing_store_ptr;)
291 if ((p -> flags & MAIN_THREAD) == 0) {
293 IF_IA64(bs_lo = p -> backing_store_end);
295 /* The original stack. */
297 IF_IA64(bs_lo = BACKING_STORE_BASE;)
300 GC_printf3("Stack for thread 0x%lx = [%lx,%lx)\n",
301 (unsigned long) p -> id,
302 (unsigned long) lo, (unsigned long) hi);
304 if (0 == lo) ABORT("GC_push_all_stacks: sp not set!\n");
305 # ifdef STACK_GROWS_UP
306 /* We got them backwards! */
307 GC_push_all_stack(hi, lo);
309 GC_push_all_stack(lo, hi);
313 GC_printf3("Reg stack for thread 0x%lx = [%lx,%lx)\n",
314 (unsigned long) p -> id,
315 (unsigned long) bs_lo, (unsigned long) bs_hi);
317 if (pthread_equal(p -> id, me)) {
318 GC_push_all_eager(bs_lo, bs_hi);
320 GC_push_all_stack(bs_lo, bs_hi);
325 if (!found_me && !GC_in_thread_creation)
326 ABORT("Collecting from unknown thread.");
329 /* There seems to be a very rare thread stopping problem. To help us */
330 /* debug that, we save the ids of the stopping thread. */
331 pthread_t GC_stopping_thread;
334 /* We hold the allocation lock. Suspend all threads that might */
335 /* still be running. Return the number of suspend signals that */
339 int n_live_threads = 0;
343 pthread_t my_thread = pthread_self();
345 GC_stopping_thread = my_thread; /* debugging only. */
346 GC_stopping_pid = getpid(); /* debugging only. */
347 for (i = 0; i < THREAD_TABLE_SZ; i++) {
348 for (p = GC_threads[i]; p != 0; p = p -> next) {
349 if (p -> id != my_thread) {
350 if (p -> flags & FINISHED) continue;
351 if (p -> stop_info.last_stop_count == GC_stop_count) continue;
352 if (p -> thread_blocked) /* Will wait */ continue;
355 GC_printf1("Sending suspend signal to 0x%lx\n", p -> id);
358 result = pthread_kill(p -> id, SIG_SUSPEND);
361 /* Not really there anymore. Possible? */
367 ABORT("pthread_kill failed");
372 return n_live_threads;
375 /* Caller holds allocation lock. */
383 GC_printf1("Stopping the world from 0x%lx\n", pthread_self());
386 /* Make sure all free list construction has stopped before we start. */
387 /* No new construction can start, since free list construction is */
388 /* required to acquire and release the GC lock before it starts, */
389 /* and we have the lock. */
390 # ifdef PARALLEL_MARK
391 GC_acquire_mark_lock();
392 GC_ASSERT(GC_fl_builder_count == 0);
393 /* We should have previously waited for it to become zero. */
394 # endif /* PARALLEL_MARK */
396 GC_world_is_stopped = TRUE;
397 n_live_threads = GC_suspend_all();
399 if (GC_retry_signals) {
400 unsigned long wait_usecs = 0; /* Total wait since retry. */
401 # define WAIT_UNIT 3000
402 # define RETRY_INTERVAL 100000
406 sem_getvalue(&GC_suspend_ack_sem, &ack_count);
407 if (ack_count == n_live_threads) break;
408 if (wait_usecs > RETRY_INTERVAL) {
409 int newly_sent = GC_suspend_all();
412 if (GC_print_stats) {
413 GC_printf1("Resent %ld signals after timeout\n",
417 sem_getvalue(&GC_suspend_ack_sem, &ack_count);
418 if (newly_sent < n_live_threads - ack_count) {
419 WARN("Lost some threads during GC_stop_world?!\n",0);
420 n_live_threads = ack_count + newly_sent;
425 wait_usecs += WAIT_UNIT;
428 for (i = 0; i < n_live_threads; i++) {
429 while (0 != (code = sem_wait(&GC_suspend_ack_sem))) {
430 if (errno != EINTR) {
431 GC_err_printf1("Sem_wait returned %ld\n", (unsigned long)code);
432 ABORT("sem_wait for handler failed");
436 # ifdef PARALLEL_MARK
437 GC_release_mark_lock();
440 GC_printf1("World stopped from 0x%lx\n", pthread_self());
442 GC_stopping_thread = 0; /* debugging only */
445 void suspend_self() {
446 GC_thread me = GC_lookup_thread(pthread_self());
448 ABORT("attempting to suspend unknown thread");
450 me -> flags |= SUSPENDED;
452 while (me -> flags & SUSPENDED)
453 GC_brief_async_signal_safe_sleep();
457 void GC_suspend_thread(pthread_t thread) {
458 if (thread == pthread_self())
462 GC_thread t = GC_lookup_thread(thread);
464 ABORT("attempting to suspend unknown thread");
466 t -> flags |= SUSPENDED;
467 result = pthread_kill (t -> id, SIG_SUSPEND);
473 ABORT("pthread_kill failed");
478 void GC_resume_thread(pthread_t thread) {
479 GC_thread t = GC_lookup_thread(thread);
481 ABORT("attempting to resume unknown thread");
483 t -> flags &= ~SUSPENDED;
486 int GC_is_thread_suspended(pthread_t thread) {
487 GC_thread t = GC_lookup_thread(thread);
489 ABORT("querying suspension state of unknown thread");
491 return (t -> flags & SUSPENDED);
494 /* Caller holds allocation lock, and has held it continuously since */
495 /* the world stopped. */
496 void GC_start_world()
498 pthread_t my_thread = pthread_self();
500 register GC_thread p;
501 register int n_live_threads = 0;
505 GC_printf0("World starting\n");
508 GC_world_is_stopped = FALSE;
509 for (i = 0; i < THREAD_TABLE_SZ; i++) {
510 for (p = GC_threads[i]; p != 0; p = p -> next) {
511 if (p -> id != my_thread) {
512 if (p -> flags & FINISHED) continue;
513 if (p -> thread_blocked) continue;
516 GC_printf1("Sending restart signal to 0x%lx\n", p -> id);
518 result = pthread_kill(p -> id, SIG_THR_RESTART);
521 /* Not really there anymore. Possible? */
527 ABORT("pthread_kill failed");
533 GC_printf0("World started\n");
537 void GC_stop_init() {
538 struct sigaction act;
540 if (sem_init(&GC_suspend_ack_sem, 0, 0) != 0)
541 ABORT("sem_init failed");
543 act.sa_flags = SA_RESTART;
544 if (sigfillset(&act.sa_mask) != 0) {
545 ABORT("sigfillset() failed");
547 GC_remove_allowed_signals(&act.sa_mask);
548 /* SIG_THR_RESTART is set in the resulting mask. */
549 /* It is unmasked by the handler when necessary. */
550 act.sa_handler = GC_suspend_handler;
551 if (sigaction(SIG_SUSPEND, &act, NULL) != 0) {
552 ABORT("Cannot set SIG_SUSPEND handler");
555 act.sa_handler = GC_restart_handler;
556 if (sigaction(SIG_THR_RESTART, &act, NULL) != 0) {
557 ABORT("Cannot set SIG_THR_RESTART handler");
560 /* Inititialize suspend_handler_mask. It excludes SIG_THR_RESTART. */
561 if (sigfillset(&suspend_handler_mask) != 0) ABORT("sigfillset() failed");
562 GC_remove_allowed_signals(&suspend_handler_mask);
563 if (sigdelset(&suspend_handler_mask, SIG_THR_RESTART) != 0)
564 ABORT("sigdelset() failed");
566 /* Check for GC_RETRY_SIGNALS. */
567 if (0 != GETENV("GC_RETRY_SIGNALS")) {
568 GC_retry_signals = TRUE;
570 if (0 != GETENV("GC_NO_RETRY_SIGNALS")) {
571 GC_retry_signals = FALSE;
574 if (GC_print_stats && GC_retry_signals) {
575 GC_printf0("Will retry suspend signal if necessary.\n");