#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
#if DEBUG_THREADS
static sigset_t suspend_handler_mask;
-word GC_stop_count; /* Incremented at the beginning of GC_stop_world. */
+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)
+extern void GC_with_callee_saves_pushed();
+
void GC_suspend_handler(int sig)
{
+ 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)
+{
+ 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;
/* this thread a SIG_THR_RESTART signal. */
/* SIG_THR_RESTART should be masked at this point. Thus there */
/* is no race. */
- do {
- me->stop_info.signal = 0;
- sigsuspend(&suspend_handler_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
/* 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_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? */
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