1 /*
   2  * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "runtime/threadLocalStorage.hpp"
  26 #include <pthread.h>
  27 
  28 static pthread_key_t _thread_key;
  29 static bool _initialized = false;
  30 
  31 // Restore the thread pointer if the destructor is called. This is in case
  32 // someone from JNI code sets up a destructor with pthread_key_create to run
  33 // detachCurrentThread on thread death. Unless we restore the thread pointer we
  34 // will hang or crash. When detachCurrentThread is called the key will be set
  35 // to null and we will not be called again. If detachCurrentThread is never
  36 // called we could loop forever depending on the pthread implementation.
  37 extern "C" void restore_thread_pointer(void* p) {
  38     ThreadLocalStorage::set_thread((Thread*) p);
  39 }
  40 
  41 void ThreadLocalStorage::init() {
  42   assert(!_initialized, "initializing TLS more than once!");
  43   int rslt = pthread_key_create(&_thread_key, restore_thread_pointer);
  44   // If this assert fails we will get a recursive assertion failure
  45   // and not see the actual error message or get a hs_err file
  46   assert_status(rslt == 0, rslt, "pthread_key_create");
  47   _initialized = true;
  48 }
  49 
  50 bool ThreadLocalStorage::is_initialized() {
  51   return _initialized;
  52 }
  53 
  54 Thread* ThreadLocalStorage::thread() {
  55   // If this assert fails we will get a recursive assertion failure
  56   // and not see the actual error message or get a hs_err file.
  57   // Which most likely indicates we have taken an error path early in
  58   // the initialization process, which is using Thread::current without
  59   // checking TLS is initialized - see java.cpp vm_exit
  60   assert(_initialized, "TLS not initialized yet!");
  61   return (Thread*) pthread_getspecific(_thread_key); // may be NULL
  62 }
  63 
  64 void ThreadLocalStorage::set_thread(Thread* current) {
  65   assert(_initialized, "TLS not initialized yet!");
  66   int rslt = pthread_setspecific(_thread_key, current);
  67   assert_status(rslt == 0, rslt, "pthread_setspecific");
  68 }