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#include "private/pthread_support.h"

#if defined(GC_PTHREADS) && !defined(GC_SOLARIS_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

#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

/* 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;

#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_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;

#   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.                                              */

    /* 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.                      */

    /* 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);

#endif

}

void GC_restart_handler(int sig)

{

    pthread_t my_thread = pthread_self();

    if (sig != SIG_THR_RESTART) ABORT("Bad signal in suspend_handler");

    /*

    ** 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

    ** 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()

{

    GC_bool found_me = FALSE;

    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

            found_me = TRUE;

            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 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 {

            GC_push_all_stack(bs_lo, bs_hi);

          }

#       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  */

/* 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;

    GC_world_is_stopped = TRUE;

    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++) {

          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_release_mark_lock();

#   endif

    #if DEBUG_THREADS

      GC_printf1("World stopped from 0x%lx\n", pthread_self());

    #endif

    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()

{

    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

    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 (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");

    }

    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");

    }

    act.sa_handler = GC_restart_handler;

    if (sigaction(SIG_THR_RESTART, &act, NULL) != 0) {

        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;

      }

      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