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1 /*
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2 * Copyright 2001-2006 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 /* CopyrightVersion 1.2 */
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26
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27 /* This is a special library that should be loaded before libc &
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28 * libthread to interpose the signal handler installation functions:
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29 * sigaction(), signal(), sigset().
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30 * Used for signal-chaining. See RFE 4381843.
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31 */
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32
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33 #include <signal.h>
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34 #include <dlfcn.h>
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35 #include <pthread.h>
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36 #include <stdio.h>
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37 #include <stdlib.h>
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38
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39 #define bool int
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40 #define true 1
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41 #define false 0
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42
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43 #define MAXSIGNUM 32
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44 #define MASK(sig) ((unsigned int)1 << sig)
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45
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46 static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */
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47 static unsigned int jvmsigs = 0; /* signals used by jvm */
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48
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49 /* used to synchronize the installation of signal handlers */
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50 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
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51 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
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52 static pthread_t tid = 0;
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53
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54 typedef void (*sa_handler_t)(int);
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55 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
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56 typedef sa_handler_t (*signal_t)(int, sa_handler_t);
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57 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
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58
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59 static signal_t os_signal = 0; /* os's version of signal()/sigset() */
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60 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
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61
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62 static bool jvm_signal_installing = false;
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63 static bool jvm_signal_installed = false;
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64
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65 static void signal_lock() {
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66 pthread_mutex_lock(&mutex);
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67 /* When the jvm is installing its set of signal handlers, threads
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68 * other than the jvm thread should wait */
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69 if (jvm_signal_installing) {
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70 if (tid != pthread_self()) {
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71 pthread_cond_wait(&cond, &mutex);
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72 }
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73 }
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74 }
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75
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76 static void signal_unlock() {
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77 pthread_mutex_unlock(&mutex);
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78 }
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79
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80 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
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81 bool is_sigset) {
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82 if (os_signal == NULL) {
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83 if (!is_sigset) {
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84 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
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85 } else {
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86 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
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87 }
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88 if (os_signal == NULL) {
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89 printf("%s\n", dlerror());
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90 exit(0);
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91 }
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92 }
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93 return (*os_signal)(sig, disp);
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94 }
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95
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96 static void save_signal_handler(int sig, sa_handler_t disp) {
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97 sigset_t set;
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98 sact[sig].sa_handler = disp;
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99 sigemptyset(&set);
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100 sact[sig].sa_mask = set;
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101 sact[sig].sa_flags = 0;
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102 }
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103
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104 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
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105 sa_handler_t oldhandler;
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106 bool sigused;
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107
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108 signal_lock();
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109
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110 sigused = (MASK(sig) & jvmsigs) != 0;
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111 if (jvm_signal_installed && sigused) {
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112 /* jvm has installed its signal handler for this signal. */
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113 /* Save the handler. Don't really install it. */
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114 oldhandler = sact[sig].sa_handler;
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115 save_signal_handler(sig, disp);
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116
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117 signal_unlock();
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118 return oldhandler;
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119 } else if (jvm_signal_installing) {
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120 /* jvm is installing its signal handlers. Install the new
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121 * handlers and save the old ones. jvm uses sigaction().
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122 * Leave the piece here just in case. */
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123 oldhandler = call_os_signal(sig, disp, is_sigset);
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124 save_signal_handler(sig, oldhandler);
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125
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126 /* Record the signals used by jvm */
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127 jvmsigs |= MASK(sig);
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128
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129 signal_unlock();
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130 return oldhandler;
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131 } else {
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132 /* jvm has no relation with this signal (yet). Install the
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133 * the handler. */
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134 oldhandler = call_os_signal(sig, disp, is_sigset);
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135
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136 signal_unlock();
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137 return oldhandler;
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138 }
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139 }
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140
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141 sa_handler_t signal(int sig, sa_handler_t disp) {
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142 return set_signal(sig, disp, false);
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143 }
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144
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145 sa_handler_t sigset(int sig, sa_handler_t disp) {
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146 return set_signal(sig, disp, true);
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147 }
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148
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149 static int call_os_sigaction(int sig, const struct sigaction *act,
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150 struct sigaction *oact) {
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151 if (os_sigaction == NULL) {
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152 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
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153 if (os_sigaction == NULL) {
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154 printf("%s\n", dlerror());
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155 exit(0);
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156 }
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157 }
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158 return (*os_sigaction)(sig, act, oact);
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159 }
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160
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161 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
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162 int res;
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163 bool sigused;
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164 struct sigaction oldAct;
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165
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166 signal_lock();
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167
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168 sigused = (MASK(sig) & jvmsigs) != 0;
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169 if (jvm_signal_installed && sigused) {
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170 /* jvm has installed its signal handler for this signal. */
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171 /* Save the handler. Don't really install it. */
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172 if (oact != NULL) {
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173 *oact = sact[sig];
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174 }
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175 if (act != NULL) {
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176 sact[sig] = *act;
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177 }
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178
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179 signal_unlock();
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180 return 0;
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181 } else if (jvm_signal_installing) {
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182 /* jvm is installing its signal handlers. Install the new
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183 * handlers and save the old ones. */
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184 res = call_os_sigaction(sig, act, &oldAct);
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185 sact[sig] = oldAct;
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186 if (oact != NULL) {
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187 *oact = oldAct;
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188 }
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189
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190 /* Record the signals used by jvm */
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191 jvmsigs |= MASK(sig);
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192
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193 signal_unlock();
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194 return res;
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195 } else {
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196 /* jvm has no relation with this signal (yet). Install the
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197 * the handler. */
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198 res = call_os_sigaction(sig, act, oact);
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199
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200 signal_unlock();
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201 return res;
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202 }
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203 }
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204
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205 /* The three functions for the jvm to call into */
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206 void JVM_begin_signal_setting() {
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207 signal_lock();
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208 jvm_signal_installing = true;
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209 tid = pthread_self();
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210 signal_unlock();
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211 }
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212
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213 void JVM_end_signal_setting() {
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214 signal_lock();
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215 jvm_signal_installed = true;
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216 jvm_signal_installing = false;
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217 pthread_cond_broadcast(&cond);
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218 signal_unlock();
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219 }
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220
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221 struct sigaction *JVM_get_signal_action(int sig) {
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222 /* Does race condition make sense here? */
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223 if ((MASK(sig) & jvmsigs) != 0) {
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224 return &sact[sig];
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225 }
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226 return NULL;
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227 }
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