1 /* 2 * Copyright (c) 1997, 2012, 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/extendedPC.hpp" 32 #include "runtime/mutexLocker.hpp" 33 #include "runtime/os.hpp" 34 #include "utilities/ostream.hpp" 35 36 // 37 // Safepoint synchronization 38 //// 39 // The VMThread or CMS_thread uses the SafepointSynchronize::begin/end 40 // methods to enter/exit a safepoint region. The begin method will roll 41 // all JavaThreads forward to a safepoint. 42 // 43 // JavaThreads must use the ThreadSafepointState abstraction (defined in 44 // thread.hpp) to indicate that that they are at a safepoint. 45 // 46 // The Mutex/Condition variable and ObjectLocker classes calls the enter/ 47 // exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/ 48 // exit points *must* be at a safepoint. 49 50 51 class ThreadSafepointState; 52 class SnippetCache; 53 class nmethod; 54 55 // 56 // Implements roll-forward to safepoint (safepoint synchronization) 57 // 58 class SafepointSynchronize : AllStatic { 59 public: 60 enum SynchronizeState { 61 _not_synchronized = 0, // Threads not synchronized at a safepoint 62 // Keep this value 0. See the coment in do_call_back() 63 _synchronizing = 1, // Synchronizing in progress 64 _synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running 65 }; 66 67 enum SafepointingThread { 68 _null_thread = 0, 69 _vm_thread = 1, 70 _other_thread = 2 71 }; 72 73 enum SafepointTimeoutReason { 74 _spinning_timeout = 0, 75 _blocking_timeout = 1 76 }; 77 78 typedef struct { 79 float _time_stamp; // record when the current safepoint occurs in seconds 80 int _vmop_type; // type of VM operation triggers the safepoint 81 int _nof_total_threads; // total number of Java threads 82 int _nof_initial_running_threads; // total number of initially seen running threads 83 int _nof_threads_wait_to_block; // total number of threads waiting for to block 84 bool _page_armed; // true if polling page is armed, false otherwise 85 int _nof_threads_hit_page_trap; // total number of threads hitting the page trap 86 jlong _time_to_spin; // total time in millis spent in spinning 87 jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block 88 jlong _time_to_do_cleanups; // total time in millis spent in performing cleanups 89 jlong _time_to_sync; // total time in millis spent in getting to _synchronized 90 jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself 91 } SafepointStats; 92 93 private: 94 static volatile SynchronizeState _state; // Threads might read this flag directly, without acquireing the Threads_lock 95 static volatile int _waiting_to_block; // number of threads we are waiting for to block 96 static int _current_jni_active_count; // Counts the number of active critical natives during the safepoint 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 // statistics 110 static jlong _safepoint_begin_time; // time when safepoint begins 111 static SafepointStats* _safepoint_stats; // array of SafepointStats struct 112 static int _cur_stat_index; // current index to the above array 113 static julong _safepoint_reasons[]; // safepoint count for each VM op 114 static julong _coalesced_vmop_count; // coalesced vmop count 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 118 119 static void begin_statistics(int nof_threads, int nof_running); 120 static void update_statistics_on_spin_end(); 121 static void update_statistics_on_sync_end(jlong end_time); 122 static void update_statistics_on_cleanup_end(jlong end_time); 123 static void end_statistics(jlong end_time); 124 static void print_statistics(); 125 inline static void inc_page_trap_count() { 126 Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap); 127 } 128 129 // For debug long safepoint 130 static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason); 131 132 public: 133 134 // Main entry points 135 136 // Roll all threads forward to safepoint. Must be called by the 137 // VMThread or CMS_thread. 138 static void begin(); 139 static void end(); // Start all suspended threads again... 140 141 static bool safepoint_safe(JavaThread *thread, JavaThreadState state); 142 143 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state); 144 145 // Query 146 inline static bool is_at_safepoint() { return _state == _synchronized; } 147 inline static bool is_synchronizing() { return _state == _synchronizing; } 148 149 inline static bool do_call_back() { 150 return (_state != _not_synchronized); 151 } 152 153 inline static void increment_jni_active_count() { 154 assert_locked_or_safepoint(Safepoint_lock); 155 _current_jni_active_count++; 156 } 157 158 // Called when a thread volantary blocks 159 static void block(JavaThread *thread); 160 static void signal_thread_at_safepoint() { _waiting_to_block--; } 161 162 // Exception handling for page polling 163 static void handle_polling_page_exception(JavaThread *thread); 164 165 // VM Thread interface for determining safepoint rate 166 static long last_non_safepoint_interval() { 167 return os::javaTimeMillis() - _end_of_last_safepoint; 168 } 169 static long end_of_last_safepoint() { 170 return _end_of_last_safepoint; 171 } 172 static bool is_cleanup_needed(); 173 static void do_cleanup_tasks(); 174 175 // debugging 176 static void print_state() PRODUCT_RETURN; 177 static void safepoint_msg(const char* format, ...) PRODUCT_RETURN; 178 179 static void deferred_initialize_stat(); 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 }; 191 192 // State class for a thread suspended at a safepoint 193 class ThreadSafepointState: public CHeapObj<mtInternal> { 194 public: 195 // These states are maintained by VM thread while threads are being brought 196 // to a safepoint. After SafepointSynchronize::end(), they are reset to 197 // _running. 198 enum suspend_type { 199 _running = 0, // Thread state not yet determined (i.e., not at a safepoint yet) 200 _at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock) 201 _call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm) 202 }; 203 private: 204 volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint) 205 // Thread has called back the safepoint code (for debugging) 206 bool _has_called_back; 207 208 JavaThread * _thread; 209 volatile suspend_type _type; 210 JavaThreadState _orig_thread_state; 211 212 213 public: 214 ThreadSafepointState(JavaThread *thread); 215 216 // examine/roll-forward/restart 217 void examine_state_of_thread(); 218 void roll_forward(suspend_type type); 219 void restart(); 220 221 // Query 222 JavaThread* thread() const { return _thread; } 223 suspend_type type() const { return _type; } 224 bool is_running() const { return (_type==_running); } 225 JavaThreadState orig_thread_state() const { return _orig_thread_state; } 226 227 // Support for safepoint timeout (debugging) 228 bool has_called_back() const { return _has_called_back; } 229 void set_has_called_back(bool val) { _has_called_back = val; } 230 bool is_at_poll_safepoint() { return _at_poll_safepoint; } 231 void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; } 232 233 void handle_polling_page_exception(); 234 235 // debugging 236 void print_on(outputStream* st) const; 237 void print() const { print_on(tty); } 238 239 // Initialize 240 static void create(JavaThread *thread); 241 static void destroy(JavaThread *thread); 242 243 void safepoint_msg(const char* format, ...) { 244 if (ShowSafepointMsgs) { 245 va_list ap; 246 va_start(ap, format); 247 tty->vprint_cr(format, ap); 248 va_end(ap); 249 } 250 } 251 }; 252 253 254 255 #endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP