520 lines
15 KiB
C
520 lines
15 KiB
C
#include "private/pthread_support.h"
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#if defined(GC_PTHREADS) && !defined(GC_SOLARIS_THREADS) \
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&& !defined(GC_WIN32_THREADS) && !defined(GC_DARWIN_THREADS)
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#include <signal.h>
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#include <semaphore.h>
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#include <errno.h>
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#include <unistd.h>
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#include <sys/time.h>
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#ifndef HPUX
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# include <sys/select.h>
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/* Doesn't exist on HP/UX 11.11. */
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#endif
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#if DEBUG_THREADS
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#ifndef NSIG
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# if defined(MAXSIG)
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# define NSIG (MAXSIG+1)
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# elif defined(_NSIG)
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# define NSIG _NSIG
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# elif defined(__SIGRTMAX)
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# define NSIG (__SIGRTMAX+1)
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# else
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--> please fix it
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# endif
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#endif
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void GC_print_sig_mask()
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{
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sigset_t blocked;
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int i;
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if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
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ABORT("pthread_sigmask");
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GC_printf0("Blocked: ");
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for (i = 1; i < NSIG; i++) {
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if (sigismember(&blocked, i)) { GC_printf1("%ld ",(long) i); }
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}
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GC_printf0("\n");
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}
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#endif
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/* Remove the signals that we want to allow in thread stopping */
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/* handler from a set. */
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void GC_remove_allowed_signals(sigset_t *set)
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{
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# ifdef NO_SIGNALS
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if (sigdelset(set, SIGINT) != 0
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|| sigdelset(set, SIGQUIT) != 0
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|| sigdelset(set, SIGABRT) != 0
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|| sigdelset(set, SIGTERM) != 0) {
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ABORT("sigdelset() failed");
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}
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# endif
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# ifdef MPROTECT_VDB
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/* Handlers write to the thread structure, which is in the heap, */
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/* and hence can trigger a protection fault. */
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if (sigdelset(set, SIGSEGV) != 0
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# ifdef SIGBUS
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|| sigdelset(set, SIGBUS) != 0
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# endif
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) {
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ABORT("sigdelset() failed");
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}
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# endif
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}
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static sigset_t suspend_handler_mask;
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volatile sig_atomic_t GC_stop_count;
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/* Incremented at the beginning of GC_stop_world. */
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volatile sig_atomic_t GC_world_is_stopped = FALSE;
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/* FALSE ==> it is safe for threads to restart, i.e. */
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/* they will see another suspend signal before they */
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/* are expected to stop (unless they have voluntarily */
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/* stopped). */
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void GC_brief_async_signal_safe_sleep()
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{
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struct timeval tv;
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tv.tv_sec = 0;
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tv.tv_usec = 1000 * TIME_LIMIT / 2;
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select(0, 0, 0, 0, &tv);
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}
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#ifdef GC_OSF1_THREADS
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GC_bool GC_retry_signals = TRUE;
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#else
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GC_bool GC_retry_signals = FALSE;
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#endif
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/*
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* We use signals to stop threads during GC.
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*
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* Suspended threads wait in signal handler for SIG_THR_RESTART.
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* That's more portable than semaphores or condition variables.
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* (We do use sem_post from a signal handler, but that should be portable.)
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*
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* The thread suspension signal SIG_SUSPEND is now defined in gc_priv.h.
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* Note that we can't just stop a thread; we need it to save its stack
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* pointer(s) and acknowledge.
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*/
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#ifndef SIG_THR_RESTART
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# if defined(GC_HPUX_THREADS) || defined(GC_OSF1_THREADS)
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# ifdef _SIGRTMIN
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# define SIG_THR_RESTART _SIGRTMIN + 5
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# else
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# define SIG_THR_RESTART SIGRTMIN + 5
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# endif
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# else
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# define SIG_THR_RESTART SIGXCPU
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# endif
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#endif
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sem_t GC_suspend_ack_sem;
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void GC_suspend_handler_inner(ptr_t sig_arg);
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#if defined(IA64) || defined(HP_PA)
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extern void GC_with_callee_saves_pushed();
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void GC_suspend_handler(int sig)
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{
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int old_errno = errno;
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GC_with_callee_saves_pushed(GC_suspend_handler_inner, (ptr_t)(word)sig);
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errno = old_errno;
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}
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#else
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/* We believe that in all other cases the full context is already */
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/* in the signal handler frame. */
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void GC_suspend_handler(int sig)
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{
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int old_errno = errno;
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GC_suspend_handler_inner((ptr_t)(word)sig);
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errno = old_errno;
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}
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#endif
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void GC_suspend_handler_inner(ptr_t sig_arg)
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{
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int sig = (int)(word)sig_arg;
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int dummy;
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pthread_t my_thread = pthread_self();
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GC_thread me;
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# ifdef PARALLEL_MARK
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word my_mark_no = GC_mark_no;
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/* Marker can't proceed until we acknowledge. Thus this is */
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/* guaranteed to be the mark_no correspending to our */
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/* suspension, i.e. the marker can't have incremented it yet. */
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# endif
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word my_stop_count = GC_stop_count;
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if (sig != SIG_SUSPEND) ABORT("Bad signal in suspend_handler");
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#if DEBUG_THREADS
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GC_printf1("Suspending 0x%lx\n", my_thread);
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#endif
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me = GC_lookup_thread(my_thread);
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/* The lookup here is safe, since I'm doing this on behalf */
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/* of a thread which holds the allocation lock in order */
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/* to stop the world. Thus concurrent modification of the */
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/* data structure is impossible. */
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if (me -> stop_info.last_stop_count == my_stop_count) {
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/* Duplicate signal. OK if we are retrying. */
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if (!GC_retry_signals) {
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WARN("Duplicate suspend signal in thread %lx\n",
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pthread_self());
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}
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return;
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}
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# ifdef SPARC
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me -> stop_info.stack_ptr = (ptr_t)GC_save_regs_in_stack();
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# else
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me -> stop_info.stack_ptr = (ptr_t)(&dummy);
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# endif
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# ifdef IA64
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me -> backing_store_ptr = (ptr_t)GC_save_regs_in_stack();
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# endif
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/* Tell the thread that wants to stop the world that this */
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/* thread has been stopped. Note that sem_post() is */
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/* the only async-signal-safe primitive in LinuxThreads. */
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sem_post(&GC_suspend_ack_sem);
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me -> stop_info.last_stop_count = my_stop_count;
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/* Wait until that thread tells us to restart by sending */
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/* this thread a SIG_THR_RESTART signal. */
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/* SIG_THR_RESTART should be masked at this point. Thus there */
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/* is no race. */
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/* We do not continue until we receive a SIG_THR_RESTART, */
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/* but we do not take that as authoritative. (We may be */
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/* accidentally restarted by one of the user signals we */
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/* don't block.) After we receive the signal, we use a */
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/* primitive and expensive mechanism to wait until it's */
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/* really safe to proceed. Under normal circumstances, */
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/* this code should not be executed. */
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sigsuspend(&suspend_handler_mask); /* Wait for signal */
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while (GC_world_is_stopped && GC_stop_count == my_stop_count) {
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GC_brief_async_signal_safe_sleep();
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# if DEBUG_THREADS
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GC_err_printf0("Sleeping in signal handler");
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# endif
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}
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/* If the RESTART signal gets lost, we can still lose. That should be */
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/* less likely than losing the SUSPEND signal, since we don't do much */
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/* between the sem_post and sigsuspend. */
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/* We'd need more handshaking to work around that. */
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/* Simply dropping the sigsuspend call should be safe, but is unlikely */
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/* to be efficient. */
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#if DEBUG_THREADS
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GC_printf1("Continuing 0x%lx\n", my_thread);
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#endif
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}
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void GC_restart_handler(int sig)
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{
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pthread_t my_thread = pthread_self();
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if (sig != SIG_THR_RESTART) ABORT("Bad signal in suspend_handler");
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/*
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** Note: even if we don't do anything useful here,
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** it would still be necessary to have a signal handler,
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** rather than ignoring the signals, otherwise
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** the signals will not be delivered at all, and
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** will thus not interrupt the sigsuspend() above.
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*/
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#if DEBUG_THREADS
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GC_printf1("In GC_restart_handler for 0x%lx\n", pthread_self());
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#endif
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}
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# ifdef IA64
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# define IF_IA64(x) x
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# else
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# define IF_IA64(x)
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# endif
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/* We hold allocation lock. Should do exactly the right thing if the */
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/* world is stopped. Should not fail if it isn't. */
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void GC_push_all_stacks()
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{
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GC_bool found_me = FALSE;
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int i;
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GC_thread p;
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ptr_t lo, hi;
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/* On IA64, we also need to scan the register backing store. */
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IF_IA64(ptr_t bs_lo; ptr_t bs_hi;)
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pthread_t me = pthread_self();
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if (!GC_thr_initialized) GC_thr_init();
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#if DEBUG_THREADS
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GC_printf1("Pushing stacks from thread 0x%lx\n", (unsigned long) me);
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#endif
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for (i = 0; i < THREAD_TABLE_SZ; i++) {
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for (p = GC_threads[i]; p != 0; p = p -> next) {
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if (p -> flags & FINISHED) continue;
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if (pthread_equal(p -> id, me)) {
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# ifdef SPARC
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lo = (ptr_t)GC_save_regs_in_stack();
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# else
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lo = GC_approx_sp();
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# endif
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found_me = TRUE;
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IF_IA64(bs_hi = (ptr_t)GC_save_regs_in_stack();)
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} else {
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lo = p -> stop_info.stack_ptr;
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IF_IA64(bs_hi = p -> backing_store_ptr;)
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}
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if ((p -> flags & MAIN_THREAD) == 0) {
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hi = p -> stack_end;
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IF_IA64(bs_lo = p -> backing_store_end);
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} else {
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/* The original stack. */
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hi = GC_stackbottom;
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IF_IA64(bs_lo = BACKING_STORE_BASE;)
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}
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#if DEBUG_THREADS
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GC_printf3("Stack for thread 0x%lx = [%lx,%lx)\n",
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(unsigned long) p -> id,
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(unsigned long) lo, (unsigned long) hi);
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#endif
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if (0 == lo) ABORT("GC_push_all_stacks: sp not set!\n");
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# ifdef STACK_GROWS_UP
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/* We got them backwards! */
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GC_push_all_stack(hi, lo);
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# else
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GC_push_all_stack(lo, hi);
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# endif
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# ifdef IA64
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# if DEBUG_THREADS
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GC_printf3("Reg stack for thread 0x%lx = [%lx,%lx)\n",
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(unsigned long) p -> id,
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(unsigned long) bs_lo, (unsigned long) bs_hi);
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# endif
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if (pthread_equal(p -> id, me)) {
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GC_push_all_eager(bs_lo, bs_hi);
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} else {
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GC_push_all_stack(bs_lo, bs_hi);
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}
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# endif
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}
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}
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if (!found_me && !GC_in_thread_creation)
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ABORT("Collecting from unknown thread.");
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}
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/* There seems to be a very rare thread stopping problem. To help us */
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/* debug that, we save the ids of the stopping thread. */
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pthread_t GC_stopping_thread;
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int GC_stopping_pid;
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/* We hold the allocation lock. Suspend all threads that might */
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/* still be running. Return the number of suspend signals that */
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/* were sent. */
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int GC_suspend_all()
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{
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int n_live_threads = 0;
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int i;
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GC_thread p;
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int result;
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pthread_t my_thread = pthread_self();
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GC_stopping_thread = my_thread; /* debugging only. */
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GC_stopping_pid = getpid(); /* debugging only. */
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for (i = 0; i < THREAD_TABLE_SZ; i++) {
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for (p = GC_threads[i]; p != 0; p = p -> next) {
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if (p -> id != my_thread) {
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if (p -> flags & FINISHED) continue;
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if (p -> stop_info.last_stop_count == GC_stop_count) continue;
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if (p -> thread_blocked) /* Will wait */ continue;
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n_live_threads++;
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#if DEBUG_THREADS
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GC_printf1("Sending suspend signal to 0x%lx\n", p -> id);
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#endif
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result = pthread_kill(p -> id, SIG_SUSPEND);
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switch(result) {
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case ESRCH:
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/* Not really there anymore. Possible? */
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n_live_threads--;
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break;
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case 0:
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break;
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default:
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ABORT("pthread_kill failed");
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}
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}
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}
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}
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return n_live_threads;
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}
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/* Caller holds allocation lock. */
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void GC_stop_world()
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{
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int i;
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int n_live_threads;
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int code;
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#if DEBUG_THREADS
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GC_printf1("Stopping the world from 0x%lx\n", pthread_self());
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#endif
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/* Make sure all free list construction has stopped before we start. */
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/* No new construction can start, since free list construction is */
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/* required to acquire and release the GC lock before it starts, */
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/* and we have the lock. */
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# ifdef PARALLEL_MARK
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GC_acquire_mark_lock();
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GC_ASSERT(GC_fl_builder_count == 0);
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/* We should have previously waited for it to become zero. */
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# endif /* PARALLEL_MARK */
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++GC_stop_count;
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GC_world_is_stopped = TRUE;
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n_live_threads = GC_suspend_all();
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if (GC_retry_signals) {
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unsigned long wait_usecs = 0; /* Total wait since retry. */
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# define WAIT_UNIT 3000
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# define RETRY_INTERVAL 100000
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for (;;) {
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int ack_count;
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sem_getvalue(&GC_suspend_ack_sem, &ack_count);
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if (ack_count == n_live_threads) break;
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if (wait_usecs > RETRY_INTERVAL) {
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int newly_sent = GC_suspend_all();
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# ifdef CONDPRINT
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if (GC_print_stats) {
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GC_printf1("Resent %ld signals after timeout\n",
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newly_sent);
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}
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# endif
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sem_getvalue(&GC_suspend_ack_sem, &ack_count);
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if (newly_sent < n_live_threads - ack_count) {
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WARN("Lost some threads during GC_stop_world?!\n",0);
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n_live_threads = ack_count + newly_sent;
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}
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wait_usecs = 0;
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}
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usleep(WAIT_UNIT);
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wait_usecs += WAIT_UNIT;
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}
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}
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for (i = 0; i < n_live_threads; i++) {
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while (0 != (code = sem_wait(&GC_suspend_ack_sem))) {
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if (errno != EINTR) {
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GC_err_printf1("Sem_wait returned %ld\n", (unsigned long)code);
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ABORT("sem_wait for handler failed");
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}
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}
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}
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# ifdef PARALLEL_MARK
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GC_release_mark_lock();
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# endif
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#if DEBUG_THREADS
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GC_printf1("World stopped from 0x%lx\n", pthread_self());
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#endif
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GC_stopping_thread = 0; /* debugging only */
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}
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/* Caller holds allocation lock, and has held it continuously since */
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/* the world stopped. */
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void GC_start_world()
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{
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pthread_t my_thread = pthread_self();
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register int i;
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register GC_thread p;
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register int n_live_threads = 0;
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register int result;
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# if DEBUG_THREADS
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GC_printf0("World starting\n");
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# endif
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GC_world_is_stopped = FALSE;
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for (i = 0; i < THREAD_TABLE_SZ; i++) {
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for (p = GC_threads[i]; p != 0; p = p -> next) {
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if (p -> id != my_thread) {
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if (p -> flags & FINISHED) continue;
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if (p -> thread_blocked) continue;
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n_live_threads++;
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#if DEBUG_THREADS
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GC_printf1("Sending restart signal to 0x%lx\n", p -> id);
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#endif
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result = pthread_kill(p -> id, SIG_THR_RESTART);
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switch(result) {
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case ESRCH:
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/* Not really there anymore. Possible? */
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n_live_threads--;
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break;
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case 0:
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break;
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default:
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ABORT("pthread_kill failed");
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}
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}
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}
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}
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#if DEBUG_THREADS
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GC_printf0("World started\n");
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#endif
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}
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void GC_stop_init() {
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struct sigaction act;
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if (sem_init(&GC_suspend_ack_sem, 0, 0) != 0)
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ABORT("sem_init failed");
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act.sa_flags = SA_RESTART;
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if (sigfillset(&act.sa_mask) != 0) {
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ABORT("sigfillset() failed");
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}
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GC_remove_allowed_signals(&act.sa_mask);
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/* SIG_THR_RESTART is set in the resulting mask. */
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/* It is unmasked by the handler when necessary. */
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act.sa_handler = GC_suspend_handler;
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if (sigaction(SIG_SUSPEND, &act, NULL) != 0) {
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ABORT("Cannot set SIG_SUSPEND handler");
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}
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act.sa_handler = GC_restart_handler;
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if (sigaction(SIG_THR_RESTART, &act, NULL) != 0) {
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ABORT("Cannot set SIG_THR_RESTART handler");
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}
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/* Inititialize suspend_handler_mask. It excludes SIG_THR_RESTART. */
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if (sigfillset(&suspend_handler_mask) != 0) ABORT("sigfillset() failed");
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GC_remove_allowed_signals(&suspend_handler_mask);
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if (sigdelset(&suspend_handler_mask, SIG_THR_RESTART) != 0)
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ABORT("sigdelset() failed");
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/* 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
|