1 | // posix-threads.cc - interface between libjava and POSIX threads. |
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2 | |
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3 | /* Copyright (C) 1998, 1999, 2000 Free Software Foundation |
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4 | |
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5 | This file is part of libgcj. |
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6 | |
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7 | This software is copyrighted work licensed under the terms of the |
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8 | Libgcj License. Please consult the file "LIBGCJ_LICENSE" for |
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9 | details. */ |
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10 | |
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11 | // TO DO: |
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12 | // * Document signal handling limitations |
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13 | |
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14 | #include <config.h> |
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15 | |
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16 | // If we're using the Boehm GC, then we need to override some of the |
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17 | // thread primitives. This is fairly gross. |
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18 | #ifdef HAVE_BOEHM_GC |
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19 | extern "C" |
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20 | { |
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21 | #include <gcconfig.h> |
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22 | #include <gc.h> |
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23 | }; |
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24 | #endif /* HAVE_BOEHM_GC */ |
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25 | |
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26 | #include <stdlib.h> |
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27 | #include <time.h> |
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28 | #include <signal.h> |
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29 | #include <errno.h> |
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30 | #include <limits.h> |
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31 | |
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32 | #include <gcj/cni.h> |
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33 | #include <jvm.h> |
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34 | #include <java/lang/Thread.h> |
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35 | #include <java/lang/System.h> |
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36 | #include <java/lang/Long.h> |
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37 | #include <java/lang/OutOfMemoryError.h> |
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38 | |
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39 | // This is used to implement thread startup. |
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40 | struct starter |
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41 | { |
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42 | _Jv_ThreadStartFunc *method; |
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43 | _Jv_Thread_t *data; |
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44 | }; |
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45 | |
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46 | // This is the key used to map from the POSIX thread value back to the |
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47 | // Java object representing the thread. The key is global to all |
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48 | // threads, so it is ok to make it a global here. |
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49 | pthread_key_t _Jv_ThreadKey; |
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50 | |
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51 | // This is the key used to map from the POSIX thread value back to the |
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52 | // _Jv_Thread_t* representing the thread. |
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53 | pthread_key_t _Jv_ThreadDataKey; |
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54 | |
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55 | // We keep a count of all non-daemon threads which are running. When |
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56 | // this reaches zero, _Jv_ThreadWait returns. |
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57 | static pthread_mutex_t daemon_mutex; |
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58 | static pthread_cond_t daemon_cond; |
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59 | static int non_daemon_count; |
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60 | |
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61 | // The signal to use when interrupting a thread. |
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62 | #ifdef LINUX_THREADS |
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63 | // LinuxThreads (prior to glibc 2.1) usurps both SIGUSR1 and SIGUSR2. |
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64 | # define INTR SIGHUP |
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65 | #else /* LINUX_THREADS */ |
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66 | # define INTR SIGUSR2 |
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67 | #endif /* LINUX_THREADS */ |
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68 | |
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69 | // |
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70 | // These are the flags that can appear in _Jv_Thread_t. |
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71 | // |
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72 | |
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73 | // Thread started. |
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74 | #define FLAG_START 0x01 |
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75 | // Thread is daemon. |
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76 | #define FLAG_DAEMON 0x02 |
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77 | |
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78 | |
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79 | |
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80 | // Wait for the condition variable "CV" to be notified. |
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81 | // Return values: |
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82 | // 0: the condition was notified, or the timeout expired. |
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83 | // _JV_NOT_OWNER: the thread does not own the mutex "MU". |
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84 | // _JV_INTERRUPTED: the thread was interrupted. Its interrupted flag is set. |
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85 | int |
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86 | _Jv_CondWait (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu, |
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87 | jlong millis, jint nanos) |
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88 | { |
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89 | pthread_t self = pthread_self(); |
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90 | if (mu->owner != self) |
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91 | return _JV_NOT_OWNER; |
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92 | |
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93 | struct timespec ts; |
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94 | jlong m, startTime; |
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95 | |
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96 | if (millis > 0 || nanos > 0) |
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97 | { |
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98 | startTime = java::lang::System::currentTimeMillis(); |
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99 | m = millis + startTime; |
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100 | ts.tv_sec = m / 1000; |
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101 | ts.tv_nsec = ((m % 1000) * 1000000) + nanos; |
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102 | } |
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103 | |
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104 | _Jv_Thread_t *current = _Jv_ThreadCurrentData (); |
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105 | java::lang::Thread *current_obj = _Jv_ThreadCurrent (); |
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106 | |
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107 | pthread_mutex_lock (¤t->wait_mutex); |
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108 | |
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109 | // Now that we hold the wait mutex, check if this thread has been |
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110 | // interrupted already. |
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111 | if (current_obj->interrupt_flag) |
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112 | { |
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113 | pthread_mutex_unlock (¤t->wait_mutex); |
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114 | return _JV_INTERRUPTED; |
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115 | } |
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116 | |
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117 | // Add this thread to the cv's wait set. |
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118 | current->next = NULL; |
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119 | |
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120 | if (cv->first == NULL) |
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121 | cv->first = current; |
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122 | else |
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123 | for (_Jv_Thread_t *t = cv->first;; t = t->next) |
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124 | { |
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125 | if (t->next == NULL) |
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126 | { |
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127 | t->next = current; |
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128 | break; |
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129 | } |
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130 | } |
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131 | |
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132 | // Record the current lock depth, so it can be restored when we re-aquire it. |
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133 | int count = mu->count; |
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134 | |
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135 | // Release the monitor mutex. |
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136 | mu->count = 0; |
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137 | mu->owner = 0; |
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138 | pthread_mutex_unlock (&mu->mutex); |
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139 | |
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140 | int r = 0; |
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141 | bool done_sleeping = false; |
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142 | |
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143 | while (! done_sleeping) |
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144 | { |
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145 | if (millis == 0 && nanos == 0) |
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146 | r = pthread_cond_wait (¤t->wait_cond, ¤t->wait_mutex); |
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147 | else |
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148 | r = pthread_cond_timedwait (¤t->wait_cond, ¤t->wait_mutex, |
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149 | &ts); |
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150 | |
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151 | // In older glibc's (prior to 2.1.3), the cond_wait functions may |
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152 | // spuriously wake up on a signal. Catch that here. |
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153 | if (r != EINTR) |
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154 | done_sleeping = true; |
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155 | } |
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156 | |
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157 | // Check for an interrupt *before* releasing the wait mutex. |
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158 | jboolean interrupted = current_obj->interrupt_flag; |
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159 | |
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160 | pthread_mutex_unlock (¤t->wait_mutex); |
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161 | |
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162 | // Reaquire the monitor mutex, and restore the lock count. |
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163 | pthread_mutex_lock (&mu->mutex); |
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164 | mu->owner = self; |
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165 | mu->count = count; |
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166 | |
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167 | // If we were interrupted, or if a timeout occured, remove ourself from |
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168 | // the cv wait list now. (If we were notified normally, notify() will have |
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169 | // already taken care of this) |
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170 | if (r == ETIMEDOUT || interrupted) |
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171 | { |
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172 | _Jv_Thread_t *prev = NULL; |
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173 | for (_Jv_Thread_t *t = cv->first; t != NULL; t = t->next) |
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174 | { |
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175 | if (t == current) |
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176 | { |
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177 | if (prev != NULL) |
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178 | prev->next = t->next; |
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179 | else |
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180 | cv->first = t->next; |
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181 | t->next = NULL; |
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182 | break; |
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183 | } |
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184 | prev = t; |
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185 | } |
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186 | if (interrupted) |
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187 | return _JV_INTERRUPTED; |
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188 | } |
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189 | |
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190 | return 0; |
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191 | } |
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192 | |
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193 | int |
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194 | _Jv_CondNotify (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu) |
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195 | { |
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196 | if (_Jv_PthreadCheckMonitor (mu)) |
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197 | return _JV_NOT_OWNER; |
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198 | |
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199 | _Jv_Thread_t *target; |
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200 | _Jv_Thread_t *prev = NULL; |
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201 | |
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202 | for (target = cv->first; target != NULL; target = target->next) |
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203 | { |
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204 | pthread_mutex_lock (&target->wait_mutex); |
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205 | |
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206 | if (target->thread_obj->interrupt_flag) |
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207 | { |
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208 | // Don't notify a thread that has already been interrupted. |
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209 | pthread_mutex_unlock (&target->wait_mutex); |
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210 | prev = target; |
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211 | continue; |
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212 | } |
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213 | |
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214 | pthread_cond_signal (&target->wait_cond); |
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215 | pthread_mutex_unlock (&target->wait_mutex); |
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216 | |
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217 | // Two concurrent notify() calls must not be delivered to the same |
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218 | // thread, so remove the target thread from the cv wait list now. |
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219 | if (prev == NULL) |
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220 | cv->first = target->next; |
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221 | else |
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222 | prev->next = target->next; |
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223 | |
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224 | target->next = NULL; |
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225 | |
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226 | break; |
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227 | } |
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228 | |
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229 | return 0; |
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230 | } |
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231 | |
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232 | int |
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233 | _Jv_CondNotifyAll (_Jv_ConditionVariable_t *cv, _Jv_Mutex_t *mu) |
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234 | { |
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235 | if (_Jv_PthreadCheckMonitor (mu)) |
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236 | return _JV_NOT_OWNER; |
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237 | |
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238 | _Jv_Thread_t *target; |
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239 | _Jv_Thread_t *prev = NULL; |
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240 | |
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241 | for (target = cv->first; target != NULL; target = target->next) |
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242 | { |
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243 | pthread_mutex_lock (&target->wait_mutex); |
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244 | pthread_cond_signal (&target->wait_cond); |
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245 | pthread_mutex_unlock (&target->wait_mutex); |
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246 | |
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247 | if (prev != NULL) |
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248 | prev->next = NULL; |
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249 | prev = target; |
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250 | } |
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251 | if (prev != NULL) |
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252 | prev->next = NULL; |
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253 | |
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254 | cv->first = NULL; |
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255 | |
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256 | return 0; |
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257 | } |
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258 | |
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259 | void |
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260 | _Jv_ThreadInterrupt (_Jv_Thread_t *data) |
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261 | { |
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262 | pthread_mutex_lock (&data->wait_mutex); |
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263 | |
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264 | // Set the thread's interrupted flag *after* aquiring its wait_mutex. This |
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265 | // ensures that there are no races with the interrupt flag being set after |
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266 | // the waiting thread checks it and before pthread_cond_wait is entered. |
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267 | data->thread_obj->interrupt_flag = true; |
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268 | |
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269 | // Interrupt blocking system calls using a signal. |
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270 | // pthread_kill (data->thread, INTR); |
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271 | |
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272 | pthread_cond_signal (&data->wait_cond); |
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273 | |
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274 | pthread_mutex_unlock (&data->wait_mutex); |
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275 | } |
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276 | |
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277 | static void |
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278 | handle_intr (int) |
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279 | { |
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280 | // Do nothing. |
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281 | } |
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282 | |
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283 | void |
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284 | _Jv_InitThreads (void) |
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285 | { |
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286 | pthread_key_create (&_Jv_ThreadKey, NULL); |
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287 | pthread_key_create (&_Jv_ThreadDataKey, NULL); |
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288 | pthread_mutex_init (&daemon_mutex, NULL); |
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289 | pthread_cond_init (&daemon_cond, 0); |
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290 | non_daemon_count = 0; |
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291 | |
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292 | // Arrange for the interrupt signal to interrupt system calls. |
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293 | struct sigaction act; |
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294 | act.sa_handler = handle_intr; |
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295 | sigemptyset (&act.sa_mask); |
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296 | act.sa_flags = 0; |
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297 | sigaction (INTR, &act, NULL); |
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298 | } |
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299 | |
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300 | _Jv_Thread_t * |
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301 | _Jv_ThreadInitData (java::lang::Thread *obj) |
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302 | { |
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303 | _Jv_Thread_t *data = (_Jv_Thread_t *) _Jv_Malloc (sizeof (_Jv_Thread_t)); |
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304 | data->flags = 0; |
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305 | data->thread_obj = obj; |
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306 | |
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307 | pthread_mutex_init (&data->wait_mutex, NULL); |
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308 | pthread_cond_init (&data->wait_cond, NULL); |
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309 | |
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310 | return data; |
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311 | } |
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312 | |
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313 | void |
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314 | _Jv_ThreadDestroyData (_Jv_Thread_t *data) |
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315 | { |
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316 | pthread_mutex_destroy (&data->wait_mutex); |
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317 | pthread_cond_destroy (&data->wait_cond); |
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318 | _Jv_Free ((void *)data); |
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319 | } |
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320 | |
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321 | void |
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322 | _Jv_ThreadSetPriority (_Jv_Thread_t *data, jint prio) |
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323 | { |
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324 | if (data->flags & FLAG_START) |
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325 | { |
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326 | struct sched_param param; |
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327 | |
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328 | param.sched_priority = prio; |
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329 | pthread_setschedparam (data->thread, SCHED_RR, ¶m); |
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330 | } |
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331 | } |
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332 | |
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333 | // This function is called when a thread is started. We don't arrange |
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334 | // to call the `run' method directly, because this function must |
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335 | // return a value. |
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336 | static void * |
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337 | really_start (void *x) |
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338 | { |
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339 | struct starter *info = (struct starter *) x; |
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340 | |
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341 | pthread_setspecific (_Jv_ThreadKey, info->data->thread_obj); |
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342 | pthread_setspecific (_Jv_ThreadDataKey, info->data); |
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343 | |
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344 | // glibc 2.1.3 doesn't set the value of `thread' until after start_routine |
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345 | // is called. Since it may need to be accessed from the new thread, work |
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346 | // around the potential race here by explicitly setting it again. |
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347 | info->data->thread = pthread_self (); |
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348 | |
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349 | info->method (info->data->thread_obj); |
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350 | |
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351 | if (! (info->data->flags & FLAG_DAEMON)) |
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352 | { |
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353 | pthread_mutex_lock (&daemon_mutex); |
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354 | --non_daemon_count; |
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355 | if (! non_daemon_count) |
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356 | pthread_cond_signal (&daemon_cond); |
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357 | pthread_mutex_unlock (&daemon_mutex); |
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358 | } |
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359 | |
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360 | return NULL; |
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361 | } |
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362 | |
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363 | void |
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364 | _Jv_ThreadStart (java::lang::Thread *thread, _Jv_Thread_t *data, |
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365 | _Jv_ThreadStartFunc *meth) |
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366 | { |
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367 | struct sched_param param; |
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368 | pthread_attr_t attr; |
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369 | struct starter *info; |
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370 | |
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371 | if (data->flags & FLAG_START) |
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372 | return; |
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373 | data->flags |= FLAG_START; |
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374 | |
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375 | param.sched_priority = thread->getPriority(); |
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376 | |
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377 | pthread_attr_init (&attr); |
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378 | pthread_attr_setschedparam (&attr, ¶m); |
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379 | pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED); |
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380 | |
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381 | // FIXME: handle marking the info object for GC. |
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382 | info = (struct starter *) _Jv_AllocBytes (sizeof (struct starter)); |
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383 | info->method = meth; |
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384 | info->data = data; |
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385 | |
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386 | if (! thread->isDaemon()) |
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387 | { |
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388 | pthread_mutex_lock (&daemon_mutex); |
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389 | ++non_daemon_count; |
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390 | pthread_mutex_unlock (&daemon_mutex); |
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391 | } |
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392 | else |
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393 | data->flags |= FLAG_DAEMON; |
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394 | int r = pthread_create (&data->thread, &attr, really_start, (void *) info); |
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395 | |
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396 | pthread_attr_destroy (&attr); |
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397 | |
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398 | if (r) |
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399 | { |
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400 | const char* msg = "Cannot create additional threads"; |
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401 | JvThrow (new java::lang::OutOfMemoryError (JvNewStringUTF (msg))); |
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402 | } |
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403 | } |
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404 | |
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405 | void |
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406 | _Jv_ThreadWait (void) |
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407 | { |
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408 | pthread_mutex_lock (&daemon_mutex); |
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409 | if (non_daemon_count) |
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410 | pthread_cond_wait (&daemon_cond, &daemon_mutex); |
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411 | pthread_mutex_unlock (&daemon_mutex); |
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412 | } |
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