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. */
20 # define NSIG (MAXSIG+1)
23 # elif defined(__SIGRTMAX)
24 # define NSIG (__SIGRTMAX+1)
30 void GC_print_sig_mask()
35 if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
36 ABORT("pthread_sigmask");
37 GC_printf0("Blocked: ");
38 for (i = 1; i < NSIG; i++) {
39 if (sigismember(&blocked, i)) { GC_printf1("%ld ",(long) i); }
46 /* Remove the signals that we want to allow in thread stopping */
47 /* handler from a set. */
48 void GC_remove_allowed_signals(sigset_t *set)
51 if (sigdelset(set, SIGINT) != 0
52 || sigdelset(set, SIGQUIT) != 0
53 || sigdelset(set, SIGABRT) != 0
54 || sigdelset(set, SIGTERM) != 0) {
55 ABORT("sigdelset() failed");
60 /* Handlers write to the thread structure, which is in the heap, */
61 /* and hence can trigger a protection fault. */
62 if (sigdelset(set, SIGSEGV) != 0
64 || sigdelset(set, SIGBUS) != 0
67 ABORT("sigdelset() failed");
72 static sigset_t suspend_handler_mask;
74 volatile sig_atomic_t GC_stop_count;
75 /* Incremented at the beginning of GC_stop_world. */
77 volatile sig_atomic_t GC_world_is_stopped = FALSE;
78 /* FALSE ==> it is safe for threads to restart, i.e. */
79 /* they will see another suspend signal before they */
80 /* are expected to stop (unless they have voluntarily */
83 void GC_brief_async_signal_safe_sleep()
87 tv.tv_usec = 1000 * TIME_LIMIT / 2;
88 select(0, 0, 0, 0, &tv);
91 #ifdef GC_OSF1_THREADS
92 GC_bool GC_retry_signals = TRUE;
94 GC_bool GC_retry_signals = FALSE;
98 * We use signals to stop threads during GC.
100 * Suspended threads wait in signal handler for SIG_THR_RESTART.
101 * That's more portable than semaphores or condition variables.
102 * (We do use sem_post from a signal handler, but that should be portable.)
104 * The thread suspension signal SIG_SUSPEND is now defined in gc_priv.h.
105 * Note that we can't just stop a thread; we need it to save its stack
106 * pointer(s) and acknowledge.
109 #ifndef SIG_THR_RESTART
110 # if defined(GC_HPUX_THREADS) || defined(GC_OSF1_THREADS)
112 # define SIG_THR_RESTART _SIGRTMIN + 5
114 # define SIG_THR_RESTART SIGRTMIN + 5
117 # define SIG_THR_RESTART SIGXCPU
121 sem_t GC_suspend_ack_sem;
123 void GC_suspend_handler_inner(ptr_t sig_arg);
125 #if defined(IA64) || defined(HP_PA)
126 extern void GC_with_callee_saves_pushed();
128 void GC_suspend_handler(int sig)
130 int old_errno = errno;
131 GC_with_callee_saves_pushed(GC_suspend_handler_inner, (ptr_t)(word)sig);
136 /* We believe that in all other cases the full context is already */
137 /* in the signal handler frame. */
138 void GC_suspend_handler(int sig)
140 int old_errno = errno;
141 GC_suspend_handler_inner((ptr_t)(word)sig);
146 void GC_suspend_handler_inner(ptr_t sig_arg)
148 int sig = (int)(word)sig_arg;
150 pthread_t my_thread = pthread_self();
152 # ifdef PARALLEL_MARK
153 word my_mark_no = GC_mark_no;
154 /* Marker can't proceed until we acknowledge. Thus this is */
155 /* guaranteed to be the mark_no correspending to our */
156 /* suspension, i.e. the marker can't have incremented it yet. */
158 word my_stop_count = GC_stop_count;
160 if (sig != SIG_SUSPEND) ABORT("Bad signal in suspend_handler");
163 GC_printf1("Suspending 0x%lx\n", my_thread);
166 me = GC_lookup_thread(my_thread);
167 /* The lookup here is safe, since I'm doing this on behalf */
168 /* of a thread which holds the allocation lock in order */
169 /* to stop the world. Thus concurrent modification of the */
170 /* data structure is impossible. */
171 if (me -> stop_info.last_stop_count == my_stop_count) {
172 /* Duplicate signal. OK if we are retrying. */
173 if (!GC_retry_signals) {
174 WARN("Duplicate suspend signal in thread %lx\n",
180 me -> stop_info.stack_ptr = (ptr_t)GC_save_regs_in_stack();
182 me -> stop_info.stack_ptr = (ptr_t)(&dummy);
185 me -> backing_store_ptr = (ptr_t)GC_save_regs_in_stack();
188 /* Tell the thread that wants to stop the world that this */
189 /* thread has been stopped. Note that sem_post() is */
190 /* the only async-signal-safe primitive in LinuxThreads. */
191 sem_post(&GC_suspend_ack_sem);
192 me -> stop_info.last_stop_count = my_stop_count;
194 /* Wait until that thread tells us to restart by sending */
195 /* this thread a SIG_THR_RESTART signal. */
196 /* SIG_THR_RESTART should be masked at this point. Thus there */
198 /* We do not continue until we receive a SIG_THR_RESTART, */
199 /* but we do not take that as authoritative. (We may be */
200 /* accidentally restarted by one of the user signals we */
201 /* don't block.) After we receive the signal, we use a */
202 /* primitive and expensive mechanism to wait until it's */
203 /* really safe to proceed. Under normal circumstances, */
204 /* this code should not be executed. */
205 sigsuspend(&suspend_handler_mask); /* Wait for signal */
206 while (GC_world_is_stopped && GC_stop_count == my_stop_count) {
207 GC_brief_async_signal_safe_sleep();
209 GC_err_printf0("Sleeping in signal handler");
212 /* If the RESTART signal gets lost, we can still lose. That should be */
213 /* less likely than losing the SUSPEND signal, since we don't do much */
214 /* between the sem_post and sigsuspend. */
215 /* We'd need more handshaking to work around that. */
216 /* Simply dropping the sigsuspend call should be safe, but is unlikely */
217 /* to be efficient. */
220 GC_printf1("Continuing 0x%lx\n", my_thread);
224 void GC_restart_handler(int sig)
226 pthread_t my_thread = pthread_self();
228 if (sig != SIG_THR_RESTART) ABORT("Bad signal in suspend_handler");
231 ** Note: even if we don't do anything useful here,
232 ** it would still be necessary to have a signal handler,
233 ** rather than ignoring the signals, otherwise
234 ** the signals will not be delivered at all, and
235 ** will thus not interrupt the sigsuspend() above.
239 GC_printf1("In GC_restart_handler for 0x%lx\n", pthread_self());
244 # define IF_IA64(x) x
248 /* We hold allocation lock. Should do exactly the right thing if the */
249 /* world is stopped. Should not fail if it isn't. */
250 void GC_push_all_stacks()
252 GC_bool found_me = FALSE;
256 /* On IA64, we also need to scan the register backing store. */
257 IF_IA64(ptr_t bs_lo; ptr_t bs_hi;)
258 pthread_t me = pthread_self();
260 if (!GC_thr_initialized) GC_thr_init();
262 GC_printf1("Pushing stacks from thread 0x%lx\n", (unsigned long) me);
264 for (i = 0; i < THREAD_TABLE_SZ; i++) {
265 for (p = GC_threads[i]; p != 0; p = p -> next) {
266 if (p -> flags & FINISHED) continue;
267 if (pthread_equal(p -> id, me)) {
269 lo = (ptr_t)GC_save_regs_in_stack();
274 IF_IA64(bs_hi = (ptr_t)GC_save_regs_in_stack();)
276 lo = p -> stop_info.stack_ptr;
277 IF_IA64(bs_hi = p -> backing_store_ptr;)
279 if ((p -> flags & MAIN_THREAD) == 0) {
281 IF_IA64(bs_lo = p -> backing_store_end);
283 /* The original stack. */
285 IF_IA64(bs_lo = BACKING_STORE_BASE;)
288 GC_printf3("Stack for thread 0x%lx = [%lx,%lx)\n",
289 (unsigned long) p -> id,
290 (unsigned long) lo, (unsigned long) hi);
292 if (0 == lo) ABORT("GC_push_all_stacks: sp not set!\n");
293 # ifdef STACK_GROWS_UP
294 /* We got them backwards! */
295 GC_push_all_stack(hi, lo);
297 GC_push_all_stack(lo, hi);
301 GC_printf3("Reg stack for thread 0x%lx = [%lx,%lx)\n",
302 (unsigned long) p -> id,
303 (unsigned long) bs_lo, (unsigned long) bs_hi);
305 if (pthread_equal(p -> id, me)) {
306 GC_push_all_eager(bs_lo, bs_hi);
308 GC_push_all_stack(bs_lo, bs_hi);
313 if (!found_me && !GC_in_thread_creation)
314 ABORT("Collecting from unknown thread.");
317 /* There seems to be a very rare thread stopping problem. To help us */
318 /* debug that, we save the ids of the stopping thread. */
319 pthread_t GC_stopping_thread;
322 /* We hold the allocation lock. Suspend all threads that might */
323 /* still be running. Return the number of suspend signals that */
327 int n_live_threads = 0;
331 pthread_t my_thread = pthread_self();
333 GC_stopping_thread = my_thread; /* debugging only. */
334 GC_stopping_pid = getpid(); /* debugging only. */
335 for (i = 0; i < THREAD_TABLE_SZ; i++) {
336 for (p = GC_threads[i]; p != 0; p = p -> next) {
337 if (p -> id != my_thread) {
338 if (p -> flags & FINISHED) continue;
339 if (p -> stop_info.last_stop_count == GC_stop_count) continue;
340 if (p -> thread_blocked) /* Will wait */ continue;
343 GC_printf1("Sending suspend signal to 0x%lx\n", p -> id);
346 result = pthread_kill(p -> id, SIG_SUSPEND);
349 /* Not really there anymore. Possible? */
355 ABORT("pthread_kill failed");
360 return n_live_threads;
363 /* Caller holds allocation lock. */
371 GC_printf1("Stopping the world from 0x%lx\n", pthread_self());
374 /* Make sure all free list construction has stopped before we start. */
375 /* No new construction can start, since free list construction is */
376 /* required to acquire and release the GC lock before it starts, */
377 /* and we have the lock. */
378 # ifdef PARALLEL_MARK
379 GC_acquire_mark_lock();
380 GC_ASSERT(GC_fl_builder_count == 0);
381 /* We should have previously waited for it to become zero. */
382 # endif /* PARALLEL_MARK */
384 GC_world_is_stopped = TRUE;
385 n_live_threads = GC_suspend_all();
387 if (GC_retry_signals) {
388 unsigned long wait_usecs = 0; /* Total wait since retry. */
389 # define WAIT_UNIT 3000
390 # define RETRY_INTERVAL 100000
394 sem_getvalue(&GC_suspend_ack_sem, &ack_count);
395 if (ack_count == n_live_threads) break;
396 if (wait_usecs > RETRY_INTERVAL) {
397 int newly_sent = GC_suspend_all();
400 if (GC_print_stats) {
401 GC_printf1("Resent %ld signals after timeout\n",
405 sem_getvalue(&GC_suspend_ack_sem, &ack_count);
406 if (newly_sent < n_live_threads - ack_count) {
407 WARN("Lost some threads during GC_stop_world?!\n",0);
408 n_live_threads = ack_count + newly_sent;
413 wait_usecs += WAIT_UNIT;
416 for (i = 0; i < n_live_threads; i++) {
417 while (0 != (code = sem_wait(&GC_suspend_ack_sem))) {
418 if (errno != EINTR) {
419 GC_err_printf1("Sem_wait returned %ld\n", (unsigned long)code);
420 ABORT("sem_wait for handler failed");
424 # ifdef PARALLEL_MARK
425 GC_release_mark_lock();
428 GC_printf1("World stopped from 0x%lx\n", pthread_self());
430 GC_stopping_thread = 0; /* debugging only */
433 /* Caller holds allocation lock, and has held it continuously since */
434 /* the world stopped. */
435 void GC_start_world()
437 pthread_t my_thread = pthread_self();
439 register GC_thread p;
440 register int n_live_threads = 0;
444 GC_printf0("World starting\n");
447 GC_world_is_stopped = FALSE;
448 for (i = 0; i < THREAD_TABLE_SZ; i++) {
449 for (p = GC_threads[i]; p != 0; p = p -> next) {
450 if (p -> id != my_thread) {
451 if (p -> flags & FINISHED) continue;
452 if (p -> thread_blocked) continue;
455 GC_printf1("Sending restart signal to 0x%lx\n", p -> id);
457 result = pthread_kill(p -> id, SIG_THR_RESTART);
460 /* Not really there anymore. Possible? */
466 ABORT("pthread_kill failed");
472 GC_printf0("World started\n");
476 void GC_stop_init() {
477 struct sigaction act;
479 if (sem_init(&GC_suspend_ack_sem, 0, 0) != 0)
480 ABORT("sem_init failed");
482 act.sa_flags = SA_RESTART;
483 if (sigfillset(&act.sa_mask) != 0) {
484 ABORT("sigfillset() failed");
486 GC_remove_allowed_signals(&act.sa_mask);
487 /* SIG_THR_RESTART is set in the resulting mask. */
488 /* It is unmasked by the handler when necessary. */
489 act.sa_handler = GC_suspend_handler;
490 if (sigaction(SIG_SUSPEND, &act, NULL) != 0) {
491 ABORT("Cannot set SIG_SUSPEND handler");
494 act.sa_handler = GC_restart_handler;
495 if (sigaction(SIG_THR_RESTART, &act, NULL) != 0) {
496 ABORT("Cannot set SIG_THR_RESTART handler");
499 /* Inititialize suspend_handler_mask. It excludes SIG_THR_RESTART. */
500 if (sigfillset(&suspend_handler_mask) != 0) ABORT("sigfillset() failed");
501 GC_remove_allowed_signals(&suspend_handler_mask);
502 if (sigdelset(&suspend_handler_mask, SIG_THR_RESTART) != 0)
503 ABORT("sigdelset() failed");
505 /* Check for GC_RETRY_SIGNALS. */
506 if (0 != GETENV("GC_RETRY_SIGNALS")) {
507 GC_retry_signals = TRUE;
509 if (0 != GETENV("GC_NO_RETRY_SIGNALS")) {
510 GC_retry_signals = FALSE;
513 if (GC_print_stats && GC_retry_signals) {
514 GC_printf0("Will retry suspend signal if necessary.\n");