1 /* 2 * Copyright (c) 1997, 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_SAFEPOINT_HPP 26 #define SHARE_VM_RUNTIME_SAFEPOINT_HPP 27 28 #include "asm/assembler.hpp" 29 #include "code/nmethod.hpp" 30 #include "memory/allocation.hpp" 31 #include "runtime/atomic.hpp" 32 #include "runtime/extendedPC.hpp" 33 #include "runtime/mutexLocker.hpp" 34 #include "runtime/os.hpp" 35 #include "utilities/ostream.hpp" 36 37 // 38 // Safepoint synchronization 39 //// 40 // The VMThread or CMS_thread uses the SafepointSynchronize::begin/end 41 // methods to enter/exit a safepoint region. The begin method will roll 42 // all JavaThreads forward to a safepoint. 43 // 44 // JavaThreads must use the ThreadSafepointState abstraction (defined in 45 // thread.hpp) to indicate that that they are at a safepoint. 46 // 47 // The Mutex/Condition variable and ObjectLocker classes calls the enter/ 48 // exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/ 49 // exit points *must* be at a safepoint. 50 51 52 class ThreadSafepointState; 53 class SnippetCache; 54 class nmethod; 55 56 // 57 // Implements roll-forward to safepoint (safepoint synchronization) 58 // 59 class SafepointSynchronize : AllStatic { 60 public: 61 enum SynchronizeState { 62 _not_synchronized = 0, // Threads not synchronized at a safepoint 63 // Keep this value 0. See the comment in do_call_back() 64 _synchronizing = 1, // Synchronizing in progress 65 _synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running 66 }; 67 68 enum SafepointingThread { 69 _null_thread = 0, 70 _vm_thread = 1, 71 _other_thread = 2 72 }; 73 74 enum SafepointTimeoutReason { 75 _spinning_timeout = 0, 76 _blocking_timeout = 1 77 }; 78 79 // The enums are listed in the order of the tasks when done serially. 80 enum SafepointCleanupTasks { 81 SAFEPOINT_CLEANUP_DEFLATE_MONITORS, 82 SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES, 83 SAFEPOINT_CLEANUP_COMPILATION_POLICY, 84 SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH, 85 SAFEPOINT_CLEANUP_STRING_TABLE_REHASH, 86 SAFEPOINT_CLEANUP_CLD_PURGE, 87 SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE, 88 // Leave this one last. 89 SAFEPOINT_CLEANUP_NUM_TASKS 90 }; 91 92 private: 93 static volatile SynchronizeState _state; // Threads might read this flag directly, without acquiring the Threads_lock 94 static volatile int _waiting_to_block; // number of threads we are waiting for to block 95 static int _current_jni_active_count; // Counts the number of active critical natives during the safepoint 96 static int _defer_thr_suspend_loop_count; // Iterations before blocking VM threads 97 98 // This counter is used for fast versions of jni_Get<Primitive>Field. 99 // An even value means there is no ongoing safepoint operations. 100 // The counter is incremented ONLY at the beginning and end of each 101 // safepoint. The fact that Threads_lock is held throughout each pair of 102 // increments (at the beginning and end of each safepoint) guarantees 103 // race freedom. 104 public: 105 static volatile int _safepoint_counter; 106 private: 107 static long _end_of_last_safepoint; // Time of last safepoint in milliseconds 108 109 static julong _coalesced_vmop_count; // coalesced vmop count 110 111 #if 0 112 // Statistics 113 static jlong _safepoint_begin_time; // time when safepoint begins 114 static julong _safepoint_reasons[]; // safepoint count for each VM op 115 static jlong _max_sync_time; // maximum sync time in nanos 116 static jlong _max_vmop_time; // maximum vm operation time in nanos 117 static float _ts_of_current_safepoint; // time stamp of current safepoint in seconds 118 static volatile int _nof_threads_hit_polling_page; // threads hitting the polling page 119 #endif 120 121 static void begin_statistics(int nof_threads, int nof_running); 122 static void update_statistics_on_spin_end(); 123 static void update_statistics_on_sync_end(jlong end_time); 124 static void update_statistics_on_cleanup_end(jlong end_time); 125 static void end_statistics(jlong end_time); 126 static void print_statistics(); 127 128 // For debug long safepoint 129 static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason); 130 131 public: 132 133 // Main entry points 134 135 // Roll all threads forward to safepoint. Must be called by the 136 // VMThread or CMS_thread. 137 static void begin(); 138 static void end(); // Start all suspended threads again... 139 140 static bool safepoint_safe(JavaThread *thread, JavaThreadState state); 141 142 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state); 143 144 // Query 145 inline static bool is_at_safepoint() { return _state == _synchronized; } 146 inline static bool is_synchronizing() { return _state == _synchronizing; } 147 inline static int safepoint_counter() { return _safepoint_counter; } 148 149 inline static void increment_jni_active_count() { 150 assert_locked_or_safepoint(Safepoint_lock); 151 _current_jni_active_count++; 152 } 153 154 private: 155 inline static bool do_call_back() { 156 return (_state != _not_synchronized); 157 } 158 159 // Called when a thread voluntarily blocks 160 static void block(JavaThread *thread); 161 162 friend class SafepointMechanism; 163 164 public: 165 static void signal_thread_at_safepoint() { _waiting_to_block--; } 166 167 // Exception handling for page polling 168 static void handle_polling_page_exception(JavaThread *thread); 169 170 // VM Thread interface for determining safepoint rate 171 static long last_non_safepoint_interval() { 172 return os::javaTimeMillis() - _end_of_last_safepoint; 173 } 174 static long end_of_last_safepoint() { 175 return _end_of_last_safepoint; 176 } 177 static bool is_cleanup_needed(); 178 static void do_cleanup_tasks(); 179 180 static void print_stat_on_exit(); 181 inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; } 182 183 static void set_is_at_safepoint() { _state = _synchronized; } 184 static void set_is_not_at_safepoint() { _state = _not_synchronized; } 185 186 // Assembly support 187 static address address_of_state() { return (address)&_state; } 188 189 static address safepoint_counter_addr() { return (address)&_safepoint_counter; } 190 191 // This method is only used for -Xconcurrentio support. 192 static void set_defer_thr_suspend_loop_count() { 193 _defer_thr_suspend_loop_count = 1; 194 } 195 }; 196 197 // Some helper assert macros for safepoint checks. 198 199 #define assert_at_safepoint() \ 200 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint") 201 202 #define assert_at_safepoint_msg(...) \ 203 assert(SafepointSynchronize::is_at_safepoint(), __VA_ARGS__) 204 205 #define assert_not_at_safepoint() \ 206 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint") 207 208 #define assert_not_at_safepoint_msg(...) \ 209 assert(!SafepointSynchronize::is_at_safepoint(), __VA_ARGS__) 210 211 // State class for a thread suspended at a safepoint 212 class ThreadSafepointState: public CHeapObj<mtInternal> { 213 public: 214 // These states are maintained by VM thread while threads are being brought 215 // to a safepoint. After SafepointSynchronize::end(), they are reset to 216 // _running. 217 enum suspend_type { 218 _running = 0, // Thread state not yet determined (i.e., not at a safepoint yet) 219 _at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock) 220 _call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm) 221 }; 222 private: 223 volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint) 224 // Thread has called back the safepoint code (for debugging) 225 bool _has_called_back; 226 227 JavaThread * _thread; 228 volatile suspend_type _type; 229 JavaThreadState _orig_thread_state; 230 231 232 public: 233 ThreadSafepointState(JavaThread *thread); 234 235 // examine/roll-forward/restart 236 void examine_state_of_thread(); 237 void roll_forward(suspend_type type); 238 void restart(); 239 240 // Query 241 JavaThread* thread() const { return _thread; } 242 suspend_type type() const { return _type; } 243 bool is_running() const { return (_type==_running); } 244 JavaThreadState orig_thread_state() const { return _orig_thread_state; } 245 246 // Support for safepoint timeout (debugging) 247 bool has_called_back() const { return _has_called_back; } 248 void set_has_called_back(bool val) { _has_called_back = val; } 249 bool is_at_poll_safepoint() { return _at_poll_safepoint; } 250 void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; } 251 252 void handle_polling_page_exception(); 253 254 // debugging 255 void print_on(outputStream* st) const; 256 void print() const { print_on(tty); } 257 258 // Initialize 259 static void create(JavaThread *thread); 260 static void destroy(JavaThread *thread); 261 }; 262 263 264 265 #endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP