1 /* 2 * Copyright (c) 1998, 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_RUNTIME_VMTHREAD_HPP 26 #define SHARE_VM_RUNTIME_VMTHREAD_HPP 27 28 #include "runtime/perfData.hpp" 29 #include "runtime/thread.hpp" 30 #include "runtime/task.hpp" 31 #include "runtime/vmOperations.hpp" 32 33 // 34 // Prioritized queue of VM operations. 35 // 36 // Encapsulates both queue management and 37 // and priority policy 38 // 39 class VMOperationQueue : public CHeapObj<mtInternal> { 40 private: 41 enum Priorities { 42 SafepointPriority, // Highest priority (operation executed at a safepoint) 43 MediumPriority, // Medium priority 44 nof_priorities 45 }; 46 47 // We maintain a doubled linked list, with explicit count. 48 int _queue_length[nof_priorities]; 49 int _queue_counter; 50 VM_Operation* _queue [nof_priorities]; 51 // we also allow the vmThread to register the ops it has drained so we 52 // can scan them from oops_do 53 VM_Operation* _drain_list; 54 55 // Double-linked non-empty list insert. 56 void insert(VM_Operation* q,VM_Operation* n); 57 void unlink(VM_Operation* q); 58 59 // Basic queue manipulation 60 bool queue_empty (int prio); 61 void queue_add_front (int prio, VM_Operation *op); 62 void queue_add_back (int prio, VM_Operation *op); 63 VM_Operation* queue_remove_front(int prio); 64 void queue_oops_do(int queue, OopClosure* f); 65 void drain_list_oops_do(OopClosure* f); 66 VM_Operation* queue_drain(int prio); 67 // lock-free query: may return the wrong answer but must not break 68 bool queue_peek(int prio) { return _queue_length[prio] > 0; } 69 70 public: 71 VMOperationQueue(); 72 73 // Highlevel operations. Encapsulates policy 74 bool add(VM_Operation *op); 75 VM_Operation* remove_next(); // Returns next or null 76 VM_Operation* remove_next_at_safepoint_priority() { return queue_remove_front(SafepointPriority); } 77 VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); } 78 void set_drain_list(VM_Operation* list) { _drain_list = list; } 79 bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); } 80 81 // GC support 82 void oops_do(OopClosure* f); 83 84 void verify_queue(int prio) PRODUCT_RETURN; 85 }; 86 87 88 // VM operation timeout handling: warn or abort the VM when VM operation takes 89 // too long. Periodic tasks do not participate in safepoint protocol, and therefore 90 // can fire when application threads are stopped. 91 92 class VMOperationTimeoutTask : public PeriodicTask { 93 private: 94 volatile int _armed; 95 jlong _arm_time; 96 97 public: 98 VMOperationTimeoutTask(size_t interval_time) : 99 PeriodicTask(interval_time), _armed(0), _arm_time(0) {} 100 101 virtual void task(); 102 103 bool is_armed(); 104 void arm(); 105 void disarm(); 106 }; 107 108 // 109 // A single VMThread (the primordial thread) spawns all other threads 110 // and is itself used by other threads to offload heavy vm operations 111 // like scavenge, garbage_collect etc. 112 // 113 114 class VMThread: public NamedThread { 115 private: 116 static ThreadPriority _current_priority; 117 118 static bool _should_terminate; 119 static bool _terminated; 120 static Monitor * _terminate_lock; 121 static PerfCounter* _perf_accumulated_vm_operation_time; 122 123 static const char* _no_op_reason; 124 125 static VMOperationTimeoutTask* _timeout_task; 126 127 static bool no_op_safepoint_needed(bool check_time); 128 129 void evaluate_operation(VM_Operation* op); 130 131 public: 132 // Constructor 133 VMThread(); 134 135 // No destruction allowed 136 ~VMThread() { 137 guarantee(false, "VMThread deletion must fix the race with VM termination"); 138 } 139 140 141 // Tester 142 bool is_VM_thread() const { return true; } 143 bool is_GC_thread() const { return true; } 144 145 // The ever running loop for the VMThread 146 void loop(); 147 148 // Called to stop the VM thread 149 static void wait_for_vm_thread_exit(); 150 static bool should_terminate() { return _should_terminate; } 151 static bool is_terminated() { return _terminated == true; } 152 153 // Execution of vm operation 154 static void execute(VM_Operation* op); 155 156 // Returns the current vm operation if any. 157 static VM_Operation* vm_operation() { return _cur_vm_operation; } 158 159 // Returns the current vm operation name or set reason 160 static const char* vm_safepoint_description() { return _cur_vm_operation != NULL ? _cur_vm_operation->name() : _no_op_reason; }; 161 162 // Returns the single instance of VMThread. 163 static VMThread* vm_thread() { return _vm_thread; } 164 165 // GC support 166 void oops_do(OopClosure* f, CodeBlobClosure* cf); 167 168 void verify(); 169 170 // Performance measurement 171 static PerfCounter* perf_accumulated_vm_operation_time() { return _perf_accumulated_vm_operation_time; } 172 173 // Entry for starting vm thread 174 virtual void run(); 175 176 // Creations/Destructions 177 static void create(); 178 static void destroy(); 179 180 private: 181 // VM_Operation support 182 static VM_Operation* _cur_vm_operation; // Current VM operation 183 static VMOperationQueue* _vm_queue; // Queue (w/ policy) of VM operations 184 185 // Pointer to single-instance of VM thread 186 static VMThread* _vm_thread; 187 }; 188 189 #endif // SHARE_VM_RUNTIME_VMTHREAD_HPP