1 /* 2 * Copyright (c) 1997, 2020, 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_SAFEPOINT_HPP 26 #define SHARE_RUNTIME_SAFEPOINT_HPP 27 28 #include "memory/allocation.hpp" 29 #include "runtime/os.hpp" 30 #include "runtime/thread.hpp" 31 #include "runtime/vmOperations.hpp" 32 #include "utilities/ostream.hpp" 33 #include "utilities/waitBarrier.hpp" 34 35 // 36 // Safepoint synchronization 37 //// 38 // The VMThread uses the SafepointSynchronize::begin/end 39 // methods to enter/exit a safepoint region. The begin method will roll 40 // all JavaThreads forward to a safepoint. 41 // 42 // JavaThreads must use the ThreadSafepointState abstraction (defined in 43 // thread.hpp) to indicate that that they are at a safepoint. 44 // 45 // The Mutex/Condition variable and ObjectLocker classes calls the enter/ 46 // exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/ 47 // exit points *must* be at a safepoint. 48 49 class ThreadSafepointState; 50 51 class SafepointStateTracker { 52 uint64_t _safepoint_id; 53 bool _at_safepoint; 54 public: 55 SafepointStateTracker(uint64_t safepoint_id, bool at_safepoint); 56 bool safepoint_state_changed(); 57 }; 58 59 // 60 // Implements roll-forward to safepoint (safepoint synchronization) 61 // 62 class SafepointSynchronize : AllStatic { 63 public: 64 enum SynchronizeState { 65 _not_synchronized = 0, // Threads not synchronized at a safepoint. Keep this value 0. 66 _synchronizing = 1, // Synchronizing in progress 67 _synchronized = 2 // All Java threads are running in native, blocked in OS or stopped at safepoint. 68 // VM thread and any NonJavaThread may be running. 69 }; 70 71 // The enums are listed in the order of the tasks when done serially. 72 enum SafepointCleanupTasks { 73 SAFEPOINT_CLEANUP_LAZY_ROOT_PROCESSING, 74 SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES, 75 SAFEPOINT_CLEANUP_COMPILATION_POLICY, 76 SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH, 77 SAFEPOINT_CLEANUP_STRING_TABLE_REHASH, 78 SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE, 79 SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP, 80 // Leave this one last. 81 SAFEPOINT_CLEANUP_NUM_TASKS 82 }; 83 84 private: 85 friend class SafepointMechanism; 86 friend class ThreadSafepointState; 87 friend class HandshakeState; 88 friend class SafepointStateTracker; 89 90 // Threads might read this flag directly, without acquiring the Threads_lock: 91 static volatile SynchronizeState _state; 92 // Number of threads we are waiting for to block: 93 static int _waiting_to_block; 94 // Counts the number of active critical natives during the safepoint: 95 static int _current_jni_active_count; 96 97 // This counter is used for fast versions of jni_Get<Primitive>Field. 98 // An even value means there are no ongoing safepoint operations. 99 // The counter is incremented ONLY at the beginning and end of each 100 // safepoint. 101 static volatile uint64_t _safepoint_counter; 102 103 // A change in this counter or a change in the result of 104 // is_at_safepoint() are used by SafepointStateTracker:: 105 // safepoint_state_changed() to determine its answer. 106 static uint64_t _safepoint_id; 107 108 // JavaThreads that need to block for the safepoint will stop on the 109 // _wait_barrier, where they can quickly be started again. 110 static WaitBarrier* _wait_barrier; 111 static julong _coalesced_vmop_count; // coalesced vmop count 112 113 // For debug long safepoint 114 static void print_safepoint_timeout(); 115 116 // Helper methods for safepoint procedure: 117 static void arm_safepoint(); 118 static int synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running); 119 static void disarm_safepoint(); 120 static void increment_jni_active_count(); 121 static void decrement_waiting_to_block(); 122 static bool thread_not_running(ThreadSafepointState *cur_state); 123 124 // Used in safepoint_safe to do a stable load of the thread state. 125 static bool try_stable_load_state(JavaThreadState *state, 126 JavaThread *thread, 127 uint64_t safepoint_count); 128 129 // Called when a thread voluntarily blocks 130 static void block(JavaThread *thread); 131 132 // Called from VMThread during handshakes. 133 // If true the VMThread may safely process the handshake operation for the JavaThread. 134 static bool handshake_safe(JavaThread *thread); 135 safepoint_counter()136 static uint64_t safepoint_counter() { return _safepoint_counter; } 137 138 public: 139 140 static void init(Thread* vmthread); 141 142 // Roll all threads forward to safepoint. Must be called by the VMThread. 143 static void begin(); 144 static void end(); // Start all suspended threads again... 145 146 // The value for a not set safepoint id. 147 static const uint64_t InactiveSafepointCounter; 148 149 // Query is_at_safepoint()150 static bool is_at_safepoint() { return _state == _synchronized; } is_synchronizing()151 static bool is_synchronizing() { return _state == _synchronizing; } 152 safepoint_id()153 static uint64_t safepoint_id() { 154 return _safepoint_id; 155 } 156 safepoint_state_tracker()157 static SafepointStateTracker safepoint_state_tracker() { 158 return SafepointStateTracker(safepoint_id(), is_at_safepoint()); 159 } 160 161 // Exception handling for page polling 162 static void handle_polling_page_exception(JavaThread *thread); 163 164 static bool is_cleanup_needed(); 165 static void do_cleanup_tasks(); 166 set_is_at_safepoint()167 static void set_is_at_safepoint() { _state = _synchronized; } set_is_not_at_safepoint()168 static void set_is_not_at_safepoint() { _state = _not_synchronized; } 169 170 // Assembly support address_of_state()171 static address address_of_state() { return (address)&_state; } 172 173 // Only used for making sure that no safepoint has happened in 174 // JNI_FastGetField. Therefore only the low 32-bits are needed 175 // even if this is a 64-bit counter. safepoint_counter_addr()176 static address safepoint_counter_addr() { 177 #ifdef VM_LITTLE_ENDIAN 178 return (address)&_safepoint_counter; 179 #else /* BIG */ 180 // Return pointer to the 32 LSB: 181 return (address) (((uint32_t*)(&_safepoint_counter)) + 1); 182 #endif 183 } 184 }; 185 186 // Some helper assert macros for safepoint checks. 187 188 #define assert_at_safepoint() \ 189 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint") 190 191 #define assert_at_safepoint_msg(...) \ 192 assert(SafepointSynchronize::is_at_safepoint(), __VA_ARGS__) 193 194 #define assert_not_at_safepoint() \ 195 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint") 196 197 #define assert_not_at_safepoint_msg(...) \ 198 assert(!SafepointSynchronize::is_at_safepoint(), __VA_ARGS__) 199 200 // State class for a thread suspended at a safepoint 201 class ThreadSafepointState: public CHeapObj<mtThread> { 202 private: 203 // At polling page safepoint (NOT a poll return safepoint): 204 volatile bool _at_poll_safepoint; 205 JavaThread* _thread; 206 bool _safepoint_safe; 207 volatile uint64_t _safepoint_id; 208 209 ThreadSafepointState* _next; 210 211 void account_safe_thread(); 212 213 public: 214 ThreadSafepointState(JavaThread *thread); 215 216 // Linked list support: get_next() const217 ThreadSafepointState* get_next() const { return _next; } set_next(ThreadSafepointState * value)218 void set_next(ThreadSafepointState* value) { _next = value; } next_ptr()219 ThreadSafepointState** next_ptr() { return &_next; } 220 221 // examine/restart 222 void examine_state_of_thread(uint64_t safepoint_count); 223 void restart(); 224 225 // Query thread() const226 JavaThread* thread() const { return _thread; } is_running() const227 bool is_running() const { return !_safepoint_safe; } 228 229 uint64_t get_safepoint_id() const; 230 void reset_safepoint_id(); 231 void set_safepoint_id(uint64_t sid); 232 233 // Support for safepoint timeout (debugging) is_at_poll_safepoint()234 bool is_at_poll_safepoint() { return _at_poll_safepoint; } set_at_poll_safepoint(bool val)235 void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; } 236 237 void handle_polling_page_exception(); 238 239 // debugging 240 void print_on(outputStream* st) const; 241 242 // Initialize 243 static void create(JavaThread *thread); 244 static void destroy(JavaThread *thread); 245 }; 246 247 class SafepointTracing : public AllStatic { 248 private: 249 // Absolute 250 static jlong _last_safepoint_begin_time_ns; 251 static jlong _last_safepoint_sync_time_ns; 252 static jlong _last_safepoint_cleanup_time_ns; 253 static jlong _last_safepoint_end_time_ns; 254 255 // Relative 256 static jlong _last_app_time_ns; 257 258 static int _nof_threads; 259 static int _nof_running; 260 static int _page_trap; 261 262 static VM_Operation::VMOp_Type _current_type; 263 static jlong _max_sync_time; 264 static jlong _max_vmop_time; 265 static uint64_t _op_count[VM_Operation::VMOp_Terminating]; 266 267 static void statistics_log(); 268 269 public: 270 static void init(); 271 272 static void begin(VM_Operation::VMOp_Type type); 273 static void synchronized(int nof_threads, int nof_running, int traps); 274 static void cleanup(); 275 static void end(); 276 277 static void statistics_exit_log(); 278 time_since_last_safepoint_ms()279 static jlong time_since_last_safepoint_ms() { 280 return nanos_to_millis(os::javaTimeNanos() - _last_safepoint_end_time_ns); 281 } 282 end_of_last_safepoint_ms()283 static jlong end_of_last_safepoint_ms() { 284 return nanos_to_millis(_last_safepoint_end_time_ns); 285 } 286 start_of_safepoint()287 static jlong start_of_safepoint() { 288 return _last_safepoint_begin_time_ns; 289 } 290 }; 291 292 #endif // SHARE_RUNTIME_SAFEPOINT_HPP 293