1 /* 2 * Copyright (c) 2013, 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 #include "precompiled.hpp" 26 #include "jfr/recorder/service/jfrPostBox.hpp" 27 #include "jfr/utilities/jfrTryLock.hpp" 28 #include "runtime/atomic.hpp" 29 #include "runtime/orderAccess.inline.hpp" 30 #include "runtime/thread.inline.hpp" 31 32 #define MSG_IS_SYNCHRONOUS ( (MSGBIT(MSG_ROTATE)) | \ 33 (MSGBIT(MSG_STOP)) | \ 34 (MSGBIT(MSG_START)) | \ 35 (MSGBIT(MSG_CLONE_IN_MEMORY)) | \ 36 (MSGBIT(MSG_VM_ERROR)) \ 37 ) 38 39 static JfrPostBox* _instance = NULL; 40 41 JfrPostBox& JfrPostBox::instance() { 42 return *_instance; 43 } 44 45 JfrPostBox* JfrPostBox::create() { 46 assert(_instance == NULL, "invariant"); 47 _instance = new JfrPostBox(); 48 return _instance; 49 } 50 51 void JfrPostBox::destroy() { 52 assert(_instance != NULL, "invariant"); 53 delete _instance; 54 _instance = NULL; 55 } 56 57 JfrPostBox::JfrPostBox() : 58 _msg_read_serial(0), 59 _msg_handled_serial(0), 60 _messages(0), 61 _has_waiters(false) {} 62 63 static bool is_thread_lock_aversive() { 64 Thread* const thread = Thread::current(); 65 return (thread->is_Java_thread() && ((JavaThread*)thread)->thread_state() != _thread_in_vm) || thread->is_VM_thread(); 66 } 67 68 static bool is_synchronous(int messages) { 69 return ((messages & MSG_IS_SYNCHRONOUS) != 0); 70 } 71 72 void JfrPostBox::post(JFR_Msg msg) { 73 const int the_message = MSGBIT(msg); 74 if (is_thread_lock_aversive()) { 75 deposit(the_message); 76 return; 77 } 78 if (!is_synchronous(the_message)) { 79 asynchronous_post(the_message); 80 return; 81 } 82 synchronous_post(the_message); 83 } 84 85 void JfrPostBox::deposit(int new_messages) { 86 while (true) { 87 const int current_msgs = OrderAccess::load_acquire(&_messages); 88 // OR the new message 89 const int exchange_value = current_msgs | new_messages; 90 const int result = Atomic::cmpxchg(exchange_value, &_messages, current_msgs); 91 if (result == current_msgs) { 92 return; 93 } 94 /* Some other thread just set exactly what this thread wanted */ 95 if ((result & new_messages) == new_messages) { 96 return; 97 } 98 } 99 } 100 101 void JfrPostBox::asynchronous_post(int msg) { 102 assert(!is_synchronous(msg), "invariant"); 103 deposit(msg); 104 JfrMonitorTryLock try_msg_lock(JfrMsg_lock); 105 if (try_msg_lock.acquired()) { 106 JfrMsg_lock->notify_all(); 107 } 108 } 109 110 void JfrPostBox::synchronous_post(int msg) { 111 assert(is_synchronous(msg), "invariant"); 112 assert(!JfrMsg_lock->owned_by_self(), "should not hold JfrMsg_lock here!"); 113 MutexLockerEx msg_lock(JfrMsg_lock); 114 deposit(msg); 115 // serial_id is used to check when what we send in has been processed. 116 // _msg_read_serial is read under JfrMsg_lock protection. 117 const uintptr_t serial_id = OrderAccess::load_ptr_acquire(&_msg_read_serial) + 1; 118 JfrMsg_lock->notify_all(); 119 while (!is_message_processed(serial_id)) { 120 JfrMsg_lock->wait(); 121 } 122 } 123 124 /* 125 * Check if a synchronous message has been processed. 126 * We avoid racing on _msg_handled_serial by ensuring 127 * that we are holding the JfrMsg_lock when checking 128 * completion status. 129 */ 130 bool JfrPostBox::is_message_processed(uintptr_t serial_id) const { 131 assert(JfrMsg_lock->owned_by_self(), "_msg_handled_serial must be read under JfrMsg_lock protection"); 132 return serial_id <= OrderAccess::load_ptr_acquire(&_msg_handled_serial); 133 } 134 135 bool JfrPostBox::is_empty() const { 136 assert(JfrMsg_lock->owned_by_self(), "not holding JfrMsg_lock!"); 137 return OrderAccess::load_acquire((jint*)&_messages) == 0; 138 } 139 140 int JfrPostBox::collect() { 141 // get pending and reset to 0 142 const int messages = Atomic::xchg(0, &_messages); 143 if (check_waiters(messages)) { 144 _has_waiters = true; 145 assert(JfrMsg_lock->owned_by_self(), "incrementing _msg_read_serial is protected by JfrMsg_lock"); 146 // Update made visible on release of JfrMsg_lock via fence instruction in Monitor::IUnlock. 147 ++_msg_read_serial; 148 } 149 return messages; 150 } 151 152 bool JfrPostBox::check_waiters(int messages) const { 153 assert(JfrMsg_lock->owned_by_self(), "not holding JfrMsg_lock!"); 154 assert(!_has_waiters, "invariant"); 155 return is_synchronous(messages); 156 } 157 158 void JfrPostBox::notify_waiters() { 159 if (!_has_waiters) { 160 return; 161 } 162 _has_waiters = false; 163 assert(JfrMsg_lock->owned_by_self(), "incrementing _msg_handled_serial is protected by JfrMsg_lock."); 164 // Update made visible on release of JfrMsg_lock via fence instruction in Monitor::IUnlock. 165 ++_msg_handled_serial; 166 JfrMsg_lock->notify(); 167 } 168 169 // safeguard to ensure no threads are left waiting 170 void JfrPostBox::notify_collection_stop() { 171 MutexLockerEx msg_lock(JfrMsg_lock); 172 JfrMsg_lock->notify_all(); 173 }