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authorIvan Maidanski <ivmai@mail.ru>2011-07-26 15:28:12 +0200
committerIvan Maidanski <ivmai@mail.ru>2011-07-26 15:28:12 +0200
commit111a44f98adde07d205c92656ad9b935ca2a39a8 (patch)
tree8a0cb4e60f636fd09dd0d2e1a3a7f3a4ac0a1bb0 /pthread_stop_world.c
parentf3632431e72d48bc7772b0752e29bb1e2a0901c6 (diff)
gc6.2 tarball importgc6_2
Diffstat (limited to 'pthread_stop_world.c')
-rw-r--r--pthread_stop_world.c445
1 files changed, 445 insertions, 0 deletions
diff --git a/pthread_stop_world.c b/pthread_stop_world.c
new file mode 100644
index 0000000..5dfd26d
--- /dev/null
+++ b/pthread_stop_world.c
@@ -0,0 +1,445 @@
+#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)
+
+#include <signal.h>
+#include <semaphore.h>
+#include <errno.h>
+#include <unistd.h>
+
+#if 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
+ --> please fix it
+# endif
+#endif
+
+void GC_print_sig_mask()
+{
+ sigset_t blocked;
+ int i;
+
+ if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
+ ABORT("pthread_sigmask");
+ GC_printf0("Blocked: ");
+ for (i = 1; i < NSIG; i++) {
+ if (sigismember(&blocked, i)) { GC_printf1("%ld ",(long) i); }
+ }
+ GC_printf0("\n");
+}
+
+#endif
+
+word GC_stop_count; /* Incremented at the beginning of GC_stop_world. */
+
+#ifdef GC_OSF1_THREADS
+ GC_bool GC_retry_signals = TRUE;
+#else
+ 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)
+# ifdef _SIGRTMIN
+# define SIG_THR_RESTART _SIGRTMIN + 5
+# else
+# define SIG_THR_RESTART SIGRTMIN + 5
+# endif
+# else
+# define SIG_THR_RESTART SIGXCPU
+# endif
+#endif
+
+sem_t GC_suspend_ack_sem;
+
+void GC_suspend_handler(int sig)
+{
+ 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 */
+ /* guaranteed to be the mark_no correspending to our */
+ /* suspension, i.e. the marker can't have incremented it yet. */
+# endif
+ word my_stop_count = GC_stop_count;
+
+ if (sig != SIG_SUSPEND) ABORT("Bad signal in suspend_handler");
+
+#if DEBUG_THREADS
+ GC_printf1("Suspending 0x%lx\n", my_thread);
+#endif
+
+ me = GC_lookup_thread(my_thread);
+ /* 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. */
+ if (me -> stop_info.last_stop_count == my_stop_count) {
+ /* Duplicate signal. OK if we are retrying. */
+ if (!GC_retry_signals) {
+ WARN("Duplicate suspend signal in thread %lx\n",
+ pthread_self());
+ }
+ return;
+ }
+# ifdef SPARC
+ me -> stop_info.stack_ptr = (ptr_t)GC_save_regs_in_stack();
+# else
+ me -> stop_info.stack_ptr = (ptr_t)(&dummy);
+# endif
+# ifdef IA64
+ me -> backing_store_ptr = (ptr_t)GC_save_regs_in_stack();
+# 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);
+ me -> stop_info.last_stop_count = my_stop_count;
+
+ /* Wait until that thread tells us to restart by sending */
+ /* 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);
+ /* 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. */
+
+#if DEBUG_THREADS
+ GC_printf1("Continuing 0x%lx\n", my_thread);
+#endif
+}
+
+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,
+ ** 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.
+ */
+
+#if DEBUG_THREADS
+ GC_printf1("In GC_restart_handler for 0x%lx\n", pthread_self());
+#endif
+}
+
+# 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. */
+void GC_push_all_stacks()
+{
+ 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;)
+ pthread_t me = pthread_self();
+
+ if (!GC_thr_initialized) GC_thr_init();
+ #if DEBUG_THREADS
+ GC_printf1("Pushing stacks from thread 0x%lx\n", (unsigned long) me);
+ #endif
+ for (i = 0; i < THREAD_TABLE_SZ; i++) {
+ for (p = GC_threads[i]; p != 0; p = p -> next) {
+ if (p -> flags & FINISHED) continue;
+ if (pthread_equal(p -> id, me)) {
+# ifdef SPARC
+ lo = (ptr_t)GC_save_regs_in_stack();
+# else
+ lo = GC_approx_sp();
+# endif
+ IF_IA64(bs_hi = (ptr_t)GC_save_regs_in_stack();)
+ } else {
+ lo = p -> stop_info.stack_ptr;
+ IF_IA64(bs_hi = p -> backing_store_ptr;)
+ }
+ 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;)
+ }
+ #if DEBUG_THREADS
+ GC_printf3("Stack for thread 0x%lx = [%lx,%lx)\n",
+ (unsigned long) p -> id,
+ (unsigned long) lo, (unsigned long) hi);
+ #endif
+ if (0 == lo) ABORT("GC_push_all_stacks: sp not set!\n");
+# ifdef STACK_GROWS_UP
+ /* We got them backwards! */
+ GC_push_all_stack(hi, lo);
+# else
+ GC_push_all_stack(lo, hi);
+# endif
+# ifdef IA64
+ if (pthread_equal(p -> id, me)) {
+ GC_push_all_eager(bs_lo, bs_hi);
+ } else {
+ GC_push_all_stack(bs_lo, bs_hi);
+ }
+# endif
+ }
+ }
+}
+
+/* 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;
+
+/* We hold the allocation lock. Suspend all threads that might */
+/* still be running. Return the number of suspend signals that */
+/* were sent. */
+int GC_suspend_all()
+{
+ int n_live_threads = 0;
+ int i;
+ GC_thread p;
+ int result;
+ pthread_t my_thread = pthread_self();
+
+ GC_stopping_thread = my_thread; /* debugging only. */
+ GC_stopping_pid = getpid(); /* debugging only. */
+ for (i = 0; i < THREAD_TABLE_SZ; i++) {
+ for (p = GC_threads[i]; p != 0; p = p -> next) {
+ if (p -> id != my_thread) {
+ if (p -> flags & FINISHED) continue;
+ if (p -> stop_info.last_stop_count == GC_stop_count) continue;
+ if (p -> thread_blocked) /* Will wait */ continue;
+ n_live_threads++;
+ #if DEBUG_THREADS
+ GC_printf1("Sending suspend signal to 0x%lx\n", p -> id);
+ #endif
+
+ result = pthread_kill(p -> id, SIG_SUSPEND);
+ switch(result) {
+ case ESRCH:
+ /* Not really there anymore. Possible? */
+ n_live_threads--;
+ break;
+ case 0:
+ break;
+ default:
+ ABORT("pthread_kill failed");
+ }
+ }
+ }
+ }
+ return n_live_threads;
+}
+
+/* Caller holds allocation lock. */
+void GC_stop_world()
+{
+ int i;
+ int n_live_threads;
+ int code;
+
+ #if DEBUG_THREADS
+ GC_printf1("Stopping the world from 0x%lx\n", pthread_self());
+ #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
+ GC_acquire_mark_lock();
+ GC_ASSERT(GC_fl_builder_count == 0);
+ /* We should have previously waited for it to become zero. */
+# endif /* PARALLEL_MARK */
+ ++GC_stop_count;
+ n_live_threads = GC_suspend_all();
+
+ if (GC_retry_signals) {
+ unsigned long wait_usecs = 0; /* Total wait since retry. */
+# define WAIT_UNIT 3000
+# define RETRY_INTERVAL 100000
+ 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 = GC_suspend_all();
+
+# ifdef CONDPRINT
+ if (GC_print_stats) {
+ GC_printf1("Resent %ld signals after timeout\n",
+ newly_sent);
+ }
+# endif
+ sem_getvalue(&GC_suspend_ack_sem, &ack_count);
+ if (newly_sent < n_live_threads - ack_count) {
+ WARN("Lost some threads during GC_stop_world?!\n",0);
+ n_live_threads = ack_count + newly_sent;
+ }
+ wait_usecs = 0;
+ }
+ usleep(WAIT_UNIT);
+ wait_usecs += WAIT_UNIT;
+ }
+ }
+ 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");
+ }
+ }
+# ifdef PARALLEL_MARK
+ GC_release_mark_lock();
+# endif
+ #if DEBUG_THREADS
+ GC_printf1("World stopped from 0x%lx\n", pthread_self());
+ #endif
+ GC_stopping_thread = 0; /* debugging only */
+}
+
+/* Caller holds allocation lock, and has held it continuously since */
+/* the world stopped. */
+void GC_start_world()
+{
+ pthread_t my_thread = pthread_self();
+ register int i;
+ register GC_thread p;
+ register int n_live_threads = 0;
+ register int result;
+
+# if DEBUG_THREADS
+ GC_printf0("World starting\n");
+# endif
+
+ for (i = 0; i < THREAD_TABLE_SZ; i++) {
+ for (p = GC_threads[i]; p != 0; p = p -> next) {
+ if (p -> id != my_thread) {
+ if (p -> flags & FINISHED) continue;
+ if (p -> thread_blocked) continue;
+ n_live_threads++;
+ #if DEBUG_THREADS
+ GC_printf1("Sending restart signal to 0x%lx\n", p -> id);
+ #endif
+
+ result = pthread_kill(p -> id, SIG_THR_RESTART);
+ switch(result) {
+ case ESRCH:
+ /* Not really there anymore. Possible? */
+ n_live_threads--;
+ break;
+ case 0:
+ break;
+ default:
+ ABORT("pthread_kill failed");
+ }
+ }
+ }
+ }
+ #if DEBUG_THREADS
+ GC_printf0("World started\n");
+ #endif
+}
+
+void GC_stop_init() {
+ struct sigaction act;
+
+ if (sem_init(&GC_suspend_ack_sem, 0, 0) != 0)
+ ABORT("sem_init failed");
+
+ act.sa_flags = SA_RESTART;
+ 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. */
+ act.sa_handler = GC_suspend_handler;
+ if (sigaction(SIG_SUSPEND, &act, NULL) != 0) {
+ ABORT("Cannot set SIG_SUSPEND handler");
+ }
+
+ act.sa_handler = GC_restart_handler;
+ if (sigaction(SIG_THR_RESTART, &act, NULL) != 0) {
+ ABORT("Cannot set SIG_THR_RESTART handler");
+ }
+
+ /* Check for GC_RETRY_SIGNALS. */
+ if (0 != GETENV("GC_RETRY_SIGNALS")) {
+ GC_retry_signals = TRUE;
+ }
+ if (0 != GETENV("GC_NO_RETRY_SIGNALS")) {
+ GC_retry_signals = FALSE;
+ }
+# ifdef CONDPRINT
+ if (GC_print_stats && GC_retry_signals) {
+ GC_printf0("Will retry suspend signal if necessary.\n");
+ }
+# endif
+}
+
+#endif