/*+
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 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.+
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.+
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 *+
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 * This code is free software; you can redistribute it and/or modify it+
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 * under the terms of the GNU General Public License version 2 only, as+
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 * published by the Free Software Foundation.+
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 *+
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 * This code is distributed in the hope that it will be useful, but WITHOUT+
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or+
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License+
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 * version 2 for more details (a copy is included in the LICENSE file that+
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 * accompanied this code).+
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 *+
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 * You should have received a copy of the GNU General Public License version+
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 * 2 along with this work; if not, write to the Free Software Foundation,+
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.+
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 *+
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA+
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 * or visit www.oracle.com if you need additional information or have any+
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 * questions.+
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 *+
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 */+
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+
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/* CopyrightVersion 1.2 */+
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+
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/* This is a special library that should be loaded before libc &+
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 * libthread to interpose the signal handler installation functions:+
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 * sigaction(), signal(), sigset().+
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 * Used for signal-chaining. See RFE 4381843.+
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 */+
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+
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#include <signal.h>+
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#include <dlfcn.h>+
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#include <pthread.h>+
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#include <stdio.h>+
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#include <stdlib.h>+
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+
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#define bool int+
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#define true 1+
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#define false 0+
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+
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#define MAXSIGNUM 32+
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#define MASK(sig) ((unsigned int)1 << sig)+
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+
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static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */+
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static unsigned int jvmsigs = 0; /* signals used by jvm */+
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+
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/* used to synchronize the installation of signal handlers */+
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static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;+
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static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;+
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static pthread_t tid = 0;+
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+
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typedef void (*sa_handler_t)(int);+
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typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);+
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typedef sa_handler_t (*signal_t)(int, sa_handler_t);+
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typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);+
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+
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static signal_t os_signal = 0; /* os's version of signal()/sigset() */+
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static sigaction_t os_sigaction = 0; /* os's version of sigaction() */+
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+
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static bool jvm_signal_installing = false;+
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static bool jvm_signal_installed = false;+
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+
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static void signal_lock() {+
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  pthread_mutex_lock(&mutex);+
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  /* When the jvm is installing its set of signal handlers, threads+
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   * other than the jvm thread should wait */+
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  if (jvm_signal_installing) {+
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    if (tid != pthread_self()) {+
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      pthread_cond_wait(&cond, &mutex);+
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    }+
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  }+
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}+
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+
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static void signal_unlock() {+
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  pthread_mutex_unlock(&mutex);+
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}+
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+
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static sa_handler_t call_os_signal(int sig, sa_handler_t disp,+
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                                   bool is_sigset) {+
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  if (os_signal == NULL) {+
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    if (!is_sigset) {+
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      os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");+
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    } else {+
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      os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");+
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    }+
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    if (os_signal == NULL) {+
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      printf("%s\n", dlerror());+
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      exit(0);+
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    }+
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  }+
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  return (*os_signal)(sig, disp);+
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}+
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+
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static void save_signal_handler(int sig, sa_handler_t disp) {+
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  sigset_t set;+
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  sact[sig].sa_handler = disp;+
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  sigemptyset(&set);+
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  sact[sig].sa_mask = set;+
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  sact[sig].sa_flags = 0;+
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}+
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+
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static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {+
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  sa_handler_t oldhandler;+
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  bool sigused;+
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+
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  signal_lock();+
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+
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  sigused = (sig < MAXSIGNUM) && ((MASK(sig) & jvmsigs) != 0);+
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  if (jvm_signal_installed && sigused) {+
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    /* jvm has installed its signal handler for this signal. */+
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    /* Save the handler. Don't really install it. */+
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    oldhandler = sact[sig].sa_handler;+
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    save_signal_handler(sig, disp);+
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+
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    signal_unlock();+
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    return oldhandler;+
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  } else if (sig < MAXSIGNUM && jvm_signal_installing) {+
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    /* jvm is installing its signal handlers. Install the new+
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     * handlers and save the old ones. jvm uses sigaction().+
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     * Leave the piece here just in case. */+
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    oldhandler = call_os_signal(sig, disp, is_sigset);+
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    save_signal_handler(sig, oldhandler);+
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+
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    /* Record the signals used by jvm */+
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    jvmsigs |= MASK(sig);+
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+
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    signal_unlock();+
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    return oldhandler;+
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  } else {+
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    /* jvm has no relation with this signal (yet). Install the+
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     * the handler. */+
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    oldhandler = call_os_signal(sig, disp, is_sigset);+
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+
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    signal_unlock();+
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    return oldhandler;+
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  }+
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}+
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+
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sa_handler_t signal(int sig, sa_handler_t disp) {+
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  return set_signal(sig, disp, false);+
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}+
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+
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sa_handler_t sigset(int sig, sa_handler_t disp) {+
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  return set_signal(sig, disp, true);+
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 }+
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+
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static int call_os_sigaction(int sig, const struct sigaction  *act,+
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                             struct sigaction *oact) {+
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  if (os_sigaction == NULL) {+
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    os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");+
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    if (os_sigaction == NULL) {+
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      printf("%s\n", dlerror());+
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      exit(0);+
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    }+
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  }+
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  return (*os_sigaction)(sig, act, oact);+
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}+
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+
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int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {+
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  int res;+
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  bool sigused;+
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  struct sigaction oldAct;+
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+
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  signal_lock();+
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+
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  sigused = (sig < MAXSIGNUM) && ((MASK(sig) & jvmsigs) != 0);+
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  if (jvm_signal_installed && sigused) {+
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    /* jvm has installed its signal handler for this signal. */+
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    /* Save the handler. Don't really install it. */+
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    if (oact != NULL) {+
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      *oact = sact[sig];+
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    }+
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    if (act != NULL) {+
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      sact[sig] = *act;+
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    }+
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+
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    signal_unlock();+
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    return 0;+
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  } else if (sig < MAXSIGNUM && jvm_signal_installing) {+
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    /* jvm is installing its signal handlers. Install the new+
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     * handlers and save the old ones. */+
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    res = call_os_sigaction(sig, act, &oldAct);+
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    sact[sig] = oldAct;+
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    if (oact != NULL) {+
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      *oact = oldAct;+
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    }+
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+
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    /* Record the signals used by jvm */+
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    jvmsigs |= MASK(sig);+
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+
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    signal_unlock();+
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    return res;+
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  } else {+
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    /* jvm has no relation with this signal (yet). Install the+
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     * the handler. */+
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    res = call_os_sigaction(sig, act, oact);+
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+
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    signal_unlock();+
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    return res;+
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  }+
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}+
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+
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/* The three functions for the jvm to call into */+
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void JVM_begin_signal_setting() {+
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  signal_lock();+
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  jvm_signal_installing = true;+
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  tid = pthread_self();+
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  signal_unlock();+
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}+
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+
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void JVM_end_signal_setting() {+
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  signal_lock();+
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  jvm_signal_installed = true;+
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  jvm_signal_installing = false;+
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  pthread_cond_broadcast(&cond);+
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  signal_unlock();+
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}+
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+
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struct sigaction *JVM_get_signal_action(int sig) {+
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  /* Does race condition make sense here? */+
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  if ((MASK(sig) & jvmsigs) != 0) {+
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    return &sact[sig];+
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  }+
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  return NULL;+
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}+
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