#include "private/pthread_support.h"
#if defined(GC_PTHREADS) && !defined(GC_SOLARIS_THREADS) \
- && !defined(GC_IRIX_THREADS) && !defined(GC_WIN32_THREADS) \
- && !defined(GC_DARWIN_THREADS) && !defined(GC_AIX_THREADS)
+ && !defined(GC_WIN32_THREADS) && !defined(GC_DARWIN_THREADS)
#include <signal.h>
#include <semaphore.h>
#include <errno.h>
#include <unistd.h>
+#include <sys/time.h>
+#ifndef HPUX
+# include <sys/select.h>
+ /* Doesn't exist on HP/UX 11.11. */
+#endif
+
+void suspend_self();
#if DEBUG_THREADS
#endif
-word GC_stop_count; /* Incremented at the beginning of GC_stop_world. */
+/* Remove the signals that we want to allow in thread stopping */
+/* handler from a set. */
+void GC_remove_allowed_signals(sigset_t *set)
+{
+# ifdef NO_SIGNALS
+ if (sigdelset(set, SIGINT) != 0
+ || sigdelset(set, SIGQUIT) != 0
+ || sigdelset(set, SIGABRT) != 0
+ || sigdelset(set, SIGTERM) != 0) {
+ ABORT("sigdelset() failed");
+ }
+# endif
+
+# 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 SIGBUS
+ || sigdelset(set, SIGBUS) != 0
+# endif
+ ) {
+ ABORT("sigdelset() failed");
+ }
+# endif
+}
+
+static sigset_t suspend_handler_mask;
+
+volatile sig_atomic_t GC_stop_count;
+ /* Incremented at the beginning of GC_stop_world. */
+
+volatile sig_atomic_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 voluntarily */
+ /* stopped). */
+
+void GC_brief_async_signal_safe_sleep()
+{
+ struct timeval tv;
+ tv.tv_sec = 0;
+ tv.tv_usec = 1000 * TIME_LIMIT / 2;
+ select(0, 0, 0, 0, &tv);
+}
#ifdef GC_OSF1_THREADS
GC_bool GC_retry_signals = TRUE;
sem_t GC_suspend_ack_sem;
+void GC_suspend_handler_inner(ptr_t sig_arg);
+
+#if defined(IA64) || defined(HP_PA) || defined(M68K)
+extern void GC_with_callee_saves_pushed();
+
void GC_suspend_handler(int sig)
{
+ GC_thread me = GC_lookup_thread (pthread_self());
+ if (me -> flags & SUSPENDED)
+ suspend_self();
+ else {
+ int old_errno = errno;
+ GC_with_callee_saves_pushed(GC_suspend_handler_inner, (ptr_t)(word)sig);
+ errno = old_errno;
+ }
+}
+
+#else
+/* We believe that in all other cases the full context is already */
+/* in the signal handler frame. */
+void GC_suspend_handler(int sig)
+{
+ GC_thread me = GC_lookup_thread(pthread_self());
+ if (me -> flags & SUSPENDED)
+ suspend_self();
+ else {
+ int old_errno = errno;
+ GC_suspend_handler_inner((ptr_t)(word)sig);
+ errno = old_errno;
+ }
+}
+#endif
+
+void GC_suspend_handler_inner(ptr_t sig_arg)
+{
+ int sig = (int)(word)sig_arg;
int dummy;
pthread_t my_thread = pthread_self();
GC_thread me;
- sigset_t mask;
# ifdef PARALLEL_MARK
word my_mark_no = GC_mark_no;
/* Marker can't proceed until we acknowledge. Thus this is */
/* this thread a SIG_THR_RESTART signal. */
/* SIG_THR_RESTART should be masked at this point. Thus there */
/* is no race. */
- if (sigfillset(&mask) != 0) ABORT("sigfillset() failed");
- if (sigdelset(&mask, SIG_THR_RESTART) != 0) ABORT("sigdelset() failed");
-# ifdef NO_SIGNALS
- if (sigdelset(&mask, SIGINT) != 0) ABORT("sigdelset() failed");
- if (sigdelset(&mask, SIGQUIT) != 0) ABORT("sigdelset() failed");
- if (sigdelset(&mask, SIGTERM) != 0) ABORT("sigdelset() failed");
- if (sigdelset(&mask, SIGABRT) != 0) ABORT("sigdelset() failed");
-# endif
- do {
- me->stop_info.signal = 0;
- sigsuspend(&mask); /* Wait for signal */
- } while (me->stop_info.signal != SIG_THR_RESTART);
+ /* We do not continue until we receive a SIG_THR_RESTART, */
+ /* 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. */
+ sigsuspend(&suspend_handler_mask); /* Wait for signal */
+ while (GC_world_is_stopped && GC_stop_count == my_stop_count) {
+ GC_brief_async_signal_safe_sleep();
+# if DEBUG_THREADS
+ GC_err_printf0("Sleeping in signal handler");
+# endif
+ }
/* If the RESTART signal gets lost, we can still lose. That should be */
/* less likely than losing the SUSPEND signal, since we don't do much */
/* between the sem_post and sigsuspend. */
- /* We'd need more handshaking to work around that, since we don't want */
- /* to accidentally leave a RESTART signal pending, thus causing us to */
- /* continue prematurely in a future round. */
+ /* We'd need more handshaking to work around that. */
+ /* Simply dropping the sigsuspend call should be safe, but is unlikely */
+ /* to be efficient. */
#if DEBUG_THREADS
GC_printf1("Continuing 0x%lx\n", my_thread);
void GC_restart_handler(int sig)
{
pthread_t my_thread = pthread_self();
- GC_thread me;
if (sig != SIG_THR_RESTART) ABORT("Bad signal in suspend_handler");
- /* Let the GC_suspend_handler() know that we got a SIG_THR_RESTART. */
- /* The lookup here is safe, since I'm doing this 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. */
- me = GC_lookup_thread(my_thread);
- me->stop_info.signal = SIG_THR_RESTART;
-
/*
- ** Note: even if we didn't do anything useful here,
+ ** 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
/* world is stopped. Should not fail if it isn't. */
void GC_push_all_stacks()
{
+ GC_bool found_me = FALSE;
int i;
GC_thread p;
ptr_t lo, hi;
# else
lo = GC_approx_sp();
# endif
+ found_me = TRUE;
IF_IA64(bs_hi = (ptr_t)GC_save_regs_in_stack();)
} else {
lo = p -> stop_info.stack_ptr;
GC_push_all_stack(lo, hi);
# endif
# ifdef IA64
+# if DEBUG_THREADS
+ GC_printf3("Reg stack for thread 0x%lx = [%lx,%lx)\n",
+ (unsigned long) p -> id,
+ (unsigned long) bs_lo, (unsigned long) bs_hi);
+# endif
if (pthread_equal(p -> id, me)) {
GC_push_all_eager(bs_lo, bs_hi);
} else {
# endif
}
}
+ if (!found_me && !GC_in_thread_creation)
+ ABORT("Collecting from unknown thread.");
}
/* There seems to be a very rare thread stopping problem. To help us */
/* We should have previously waited for it to become zero. */
# endif /* PARALLEL_MARK */
++GC_stop_count;
+ GC_world_is_stopped = TRUE;
n_live_threads = GC_suspend_all();
if (GC_retry_signals) {
}
}
for (i = 0; i < n_live_threads; i++) {
- if (0 != (code = sem_wait(&GC_suspend_ack_sem))) {
- GC_err_printf1("Sem_wait returned %ld\n", (unsigned long)code);
- ABORT("sem_wait for handler failed");
+ while (0 != (code = sem_wait(&GC_suspend_ack_sem))) {
+ if (errno != EINTR) {
+ GC_err_printf1("Sem_wait returned %ld\n", (unsigned long)code);
+ ABORT("sem_wait for handler failed");
+ }
}
}
# ifdef PARALLEL_MARK
GC_stopping_thread = 0; /* debugging only */
}
+void suspend_self() {
+ GC_thread me = GC_lookup_thread(pthread_self());
+ if (me == NULL)
+ ABORT("attempting to suspend unknown thread");
+
+ me -> flags |= SUSPENDED;
+ GC_start_blocking();
+ while (me -> flags & SUSPENDED)
+ GC_brief_async_signal_safe_sleep();
+ GC_end_blocking();
+}
+
+void GC_suspend_thread(pthread_t thread) {
+ if (thread == pthread_self())
+ suspend_self();
+ else {
+ int result;
+ GC_thread t = GC_lookup_thread(thread);
+ if (t == NULL)
+ ABORT("attempting to suspend unknown thread");
+
+ t -> flags |= SUSPENDED;
+ result = pthread_kill (t -> id, SIG_SUSPEND);
+ switch (result) {
+ case ESRCH:
+ case 0:
+ break;
+ default:
+ ABORT("pthread_kill failed");
+ }
+ }
+}
+
+void GC_resume_thread(pthread_t thread) {
+ GC_thread t = GC_lookup_thread(thread);
+ if (t == NULL)
+ ABORT("attempting to resume unknown thread");
+
+ t -> flags &= ~SUSPENDED;
+}
+
+int GC_is_thread_suspended(pthread_t thread) {
+ GC_thread t = GC_lookup_thread(thread);
+ if (t == NULL)
+ ABORT("querying suspension state of unknown thread");
+
+ return (t -> flags & SUSPENDED);
+}
+
/* Caller holds allocation lock, and has held it continuously since */
/* the world stopped. */
void GC_start_world()
GC_printf0("World starting\n");
# endif
+ GC_world_is_stopped = FALSE;
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> id != my_thread) {
#if DEBUG_THREADS
GC_printf1("Sending restart signal to 0x%lx\n", p -> id);
#endif
-
- result = pthread_kill(p -> id, SIG_THR_RESTART);
+ result = pthread_kill(p -> id, SIG_THR_RESTART);
switch(result) {
case ESRCH:
/* Not really there anymore. Possible? */
if (sigfillset(&act.sa_mask) != 0) {
ABORT("sigfillset() failed");
}
-# ifdef NO_SIGNALS
- if (sigdelset(&act.sa_mask, SIGINT) != 0
- || sigdelset(&act.sa_mask, SIGQUIT != 0)
- || sigdelset(&act.sa_mask, SIGABRT != 0)
- || sigdelset(&act.sa_mask, SIGTERM != 0)) {
- ABORT("sigdelset() failed");
- }
-# endif
-
- /* SIG_THR_RESTART is unmasked by the handler when necessary. */
+ GC_remove_allowed_signals(&act.sa_mask);
+ /* SIG_THR_RESTART is set in the resulting mask. */
+ /* It is unmasked by the handler when necessary. */
act.sa_handler = GC_suspend_handler;
if (sigaction(SIG_SUSPEND, &act, NULL) != 0) {
ABORT("Cannot set SIG_SUSPEND handler");
ABORT("Cannot set SIG_THR_RESTART handler");
}
+ /* Inititialize suspend_handler_mask. It excludes SIG_THR_RESTART. */
+ if (sigfillset(&suspend_handler_mask) != 0) ABORT("sigfillset() failed");
+ GC_remove_allowed_signals(&suspend_handler_mask);
+ if (sigdelset(&suspend_handler_mask, SIG_THR_RESTART) != 0)
+ ABORT("sigdelset() failed");
+
/* Check for GC_RETRY_SIGNALS. */
if (0 != GETENV("GC_RETRY_SIGNALS")) {
GC_retry_signals = TRUE;
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