1 /* 2 * Copyright (c) 2017, 2019, 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_RUNTIME_HANDSHAKE_HPP 26 #define SHARE_RUNTIME_HANDSHAKE_HPP 27 28 #include "memory/allocation.hpp" 29 #include "memory/iterator.hpp" 30 #include "runtime/flags/flagSetting.hpp" 31 #include "runtime/semaphore.hpp" 32 33 class JavaThread; 34 35 // A handshake closure 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 HandshakeClosure : public ThreadClosure { 41 const char* const _name; 42 public: 43 HandshakeClosure(const char* name) : _name(name) {} 44 const char* name() const { 45 return _name; 46 } 47 virtual void do_thread(Thread* thread) = 0; 48 }; 49 50 class Handshake : public AllStatic { 51 public: 52 // Execution of handshake operation 53 static void execute(HandshakeClosure* hs_cl); 54 static bool execute(HandshakeClosure* hs_cl, JavaThread* target); 55 }; 56 57 class HandshakeOperation; 58 59 // The HandshakeState keep tracks of an ongoing handshake for one JavaThread. 60 // VM thread and JavaThread are serialized with the semaphore making sure 61 // the operation is only done by either VM thread on behalf of the JavaThread 62 // or the JavaThread itself. 63 class HandshakeState { 64 HandshakeOperation* volatile _operation; 65 66 Semaphore _semaphore; 67 bool _thread_in_process_handshake; 68 69 bool claim_handshake_for_vmthread(); 70 bool vmthread_can_process_handshake(JavaThread* target); 71 72 void clear_handshake(JavaThread* thread); 73 74 void process_self_inner(JavaThread* thread); 75 public: 76 HandshakeState(); 77 78 void set_operation(JavaThread* thread, HandshakeOperation* op); 79 80 bool has_operation() const { 81 return _operation != NULL; 82 } 83 84 void process_by_self(JavaThread* thread) { 85 if (!_thread_in_process_handshake) { 86 FlagSetting fs(_thread_in_process_handshake, true); 87 process_self_inner(thread); 88 } 89 } 90 91 void process_by_vmthread(JavaThread* target); 92 }; 93 94 #endif // SHARE_RUNTIME_HANDSHAKE_HPP