1 /* 2 * Copyright (c) 2017, 2018, 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_RUNTIME_HANDSHAKE_HPP 26 #define SHARE_VM_RUNTIME_HANDSHAKE_HPP 27 28 #include "memory/allocation.hpp" 29 #include "runtime/flags/flagSetting.hpp" 30 #include "runtime/semaphore.hpp" 31 32 class ThreadClosure; 33 class JavaThread; 34 35 // A handshake operation is a callback that is executed for each JavaThread 36 // while that thread is in a safepoint safe state. The callback is executed 37 // either by the thread itself or by the VM thread while keeping the thread 38 // in a blocked state. A handshake can be performed with a single 39 // JavaThread as well. 40 class Handshake : public AllStatic { 41 public: 42 // Execution of handshake operation 43 static void execute(ThreadClosure* thread_cl); 44 static bool execute(ThreadClosure* thread_cl, JavaThread* target); 45 }; 46 47 class HandshakeOperation; 48 49 // The HandshakeState keep tracks of an ongoing handshake for one JavaThread. 50 // VM thread and JavaThread are serialized with the semaphore making sure 51 // the operation is only done by either VM thread on behalf of the JavaThread 52 // or the JavaThread itself. 53 class HandshakeState { 54 HandshakeOperation* volatile _operation; 55 56 Semaphore _semaphore; 57 bool _thread_in_process_handshake; 58 59 bool claim_handshake_for_vmthread(); 60 bool vmthread_can_process_handshake(JavaThread* target); 61 62 void clear_handshake(JavaThread* thread); 63 void cancel_inner(JavaThread* thread); 64 65 void process_self_inner(JavaThread* thread); 66 public: 67 HandshakeState(); 68 69 void set_operation(JavaThread* thread, HandshakeOperation* op); 70 71 bool has_operation() const { 72 return _operation != NULL; 73 } 74 75 void cancel(JavaThread* thread) { 76 if (!_thread_in_process_handshake) { 77 FlagSetting fs(_thread_in_process_handshake, true); 78 cancel_inner(thread); 79 } 80 } 81 82 void process_by_self(JavaThread* thread) { 83 if (!_thread_in_process_handshake) { 84 FlagSetting fs(_thread_in_process_handshake, true); 85 process_self_inner(thread); 86 } 87 } 88 void process_by_vmthread(JavaThread* target); 89 }; 90 91 #endif // SHARE_VM_RUNTIME_HANDSHAKE_HPP