1 /* 2 * Copyright (c) 2016, 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 #ifndef SHARE_VM_GC_SHARED_REFERENCEPENDINGLISTLOCKER_HPP 26 #define SHARE_VM_GC_SHARED_REFERENCEPENDINGLISTLOCKER_HPP 27 28 #include "memory/allocation.hpp" 29 #include "runtime/basicLock.hpp" 30 #include "runtime/mutex.hpp" 31 #include "runtime/thread.hpp" 32 #include "utilities/exceptions.hpp" 33 34 // 35 // The ReferencePendingListLockerThread locks and unlocks the reference 36 // pending list lock on behalf a non-Java thread, typically a concurrent 37 // GC thread. This interface should not be directly accessed. All uses 38 // should instead go through the ReferencePendingListLocker, which calls 39 // this thread if needed. 40 // 41 class ReferencePendingListLockerThread : public JavaThread { 42 private: 43 enum Message { 44 NONE, 45 LOCK, 46 UNLOCK 47 }; 48 49 Monitor _monitor; 50 Message _message; 51 52 ReferencePendingListLockerThread(); 53 54 static void start(JavaThread* thread, TRAPS); 55 56 void send_message(Message message); 57 void receive_and_handle_messages(); 58 59 public: 60 static ReferencePendingListLockerThread* create(TRAPS); 61 62 virtual bool is_hidden_from_external_view() const; 63 64 void lock(); 65 void unlock(); 66 }; 67 68 // 69 // The ReferencePendingListLocker is the main interface for locking and 70 // unlocking the reference pending list lock, which needs to be held by 71 // the GC when adding references to the pending list. Since this is a 72 // Java-level monitor it can only be locked/unlocked by a Java thread. 73 // For this reason there is an option to spawn a helper thread, the 74 // ReferencePendingListLockerThread, during initialization. If a helper 75 // thread is spawned all lock operations from non-Java threads will be 76 // delegated to the helper thread. The helper thread is typically needed 77 // by concurrent GCs. 78 // 79 class ReferencePendingListLocker VALUE_OBJ_CLASS_SPEC { 80 private: 81 static bool _is_initialized; 82 static ReferencePendingListLockerThread* _locker_thread; 83 BasicLock _basic_lock; 84 85 public: 86 static void initialize(bool needs_locker_thread, TRAPS); 87 static bool is_initialized(); 88 89 static bool is_locked_by_self(); 90 91 void lock(); 92 void unlock(); 93 }; 94 95 #endif // SHARE_VM_GC_SHARED_REFERENCEPENDINGLISTLOCKER_HPP