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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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
49class ThreadSafepointState;
50
51class SafepointStateTracker {
52 uint64_t _safepoint_id;
53 bool _at_safepoint;
54public:
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//
62class 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_DEFLATE_MONITORS,
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_CLD_PURGE,
79 SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE,
80 SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP,
81 // Leave this one last.
82 SAFEPOINT_CLEANUP_NUM_TASKS
83 };
84
85 private:
86 friend class SafepointMechanism;
87 friend class ThreadSafepointState;
88 friend class HandshakeState;
89 friend class SafepointStateTracker;
90
91 // Threads might read this flag directly, without acquiring the Threads_lock:
92 static volatile SynchronizeState _state;
93 // Number of threads we are waiting for to block:
94 static int _waiting_to_block;
95 // Counts the number of active critical natives during the safepoint:
96 static int _current_jni_active_count;
97
98 // This counter is used for fast versions of jni_Get<Primitive>Field.
99 // An even value means there are no ongoing safepoint operations.
100 // The counter is incremented ONLY at the beginning and end of each
101 // safepoint.
102 static volatile uint64_t _safepoint_counter;
103
104 // A change in this counter or a change in the result of
105 // is_at_safepoint() are used by SafepointStateTracker::
106 // safepoint_state_changed() to determine its answer.
107 static uint64_t _safepoint_id;
108
109 // JavaThreads that need to block for the safepoint will stop on the
110 // _wait_barrier, where they can quickly be started again.
111 static WaitBarrier* _wait_barrier;
112 static long _end_of_last_safepoint; // Time of last safepoint in milliseconds
113 static julong _coalesced_vmop_count; // coalesced vmop count
114
115 // Statistics
116 static void begin_statistics(int nof_threads, int nof_running);
117 static void update_statistics_on_spin_end();
118 static void update_statistics_on_sync_end(jlong end_time);
119 static void update_statistics_on_cleanup_end(jlong end_time);
120 static void end_statistics(jlong end_time);
121 static void print_statistics();
122
123 // For debug long safepoint
124 static void print_safepoint_timeout();
125
126 // Helper methods for safepoint procedure:
127 static void arm_safepoint();
128 static int synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running);
129 static void disarm_safepoint();
130 static void increment_jni_active_count();
131 static void decrement_waiting_to_block();
132 static bool thread_not_running(ThreadSafepointState *cur_state);
133
134 // Used in safepoint_safe to do a stable load of the thread state.
135 static bool try_stable_load_state(JavaThreadState *state,
136 JavaThread *thread,
137 uint64_t safepoint_count);
138
139 // Called when a thread voluntarily blocks
140 static void block(JavaThread *thread);
141
142 // Called from VMThread during handshakes.
143 // If true the VMThread may safely process the handshake operation for the JavaThread.
144 static bool handshake_safe(JavaThread *thread);
145
146 static uint64_t safepoint_counter() { return _safepoint_counter; }
147
148public:
149
150 static void init(Thread* vmthread);
151
152 // Roll all threads forward to safepoint. Must be called by the VMThread.
153 static void begin();
154 static void end(); // Start all suspended threads again...
155
156 // The value for a not set safepoint id.
157 static const uint64_t InactiveSafepointCounter;
158
159 // Query
160 static bool is_at_safepoint() { return _state == _synchronized; }
161 static bool is_synchronizing() { return _state == _synchronizing; }
162
163 static uint64_t safepoint_id() {
164 return _safepoint_id;
165 }
166
167 static SafepointStateTracker safepoint_state_tracker() {
168 return SafepointStateTracker(safepoint_id(), is_at_safepoint());
169 }
170
171 // Exception handling for page polling
172 static void handle_polling_page_exception(JavaThread *thread);
173
174 static bool is_cleanup_needed();
175 static void do_cleanup_tasks();
176
177 static void set_is_at_safepoint() { _state = _synchronized; }
178 static void set_is_not_at_safepoint() { _state = _not_synchronized; }
179
180 // Assembly support
181 static address address_of_state() { return (address)&_state; }
182
183 // Only used for making sure that no safepoint has happened in
184 // JNI_FastGetField. Therefore only the low 32-bits are needed
185 // even if this is a 64-bit counter.
186 static address safepoint_counter_addr() {
187#ifdef VM_LITTLE_ENDIAN
188 return (address)&_safepoint_counter;
189#else /* BIG */
190 // Return pointer to the 32 LSB:
191 return (address) (((uint32_t*)(&_safepoint_counter)) + 1);
192#endif
193 }
194};
195
196// Some helper assert macros for safepoint checks.
197
198#define assert_at_safepoint() \
199 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint")
200
201#define assert_at_safepoint_msg(...) \
202 assert(SafepointSynchronize::is_at_safepoint(), __VA_ARGS__)
203
204#define assert_not_at_safepoint() \
205 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint")
206
207#define assert_not_at_safepoint_msg(...) \
208 assert(!SafepointSynchronize::is_at_safepoint(), __VA_ARGS__)
209
210// State class for a thread suspended at a safepoint
211class ThreadSafepointState: public CHeapObj<mtThread> {
212 private:
213 // At polling page safepoint (NOT a poll return safepoint):
214 volatile bool _at_poll_safepoint;
215 JavaThread* _thread;
216 bool _safepoint_safe;
217 volatile uint64_t _safepoint_id;
218 JavaThreadState _orig_thread_state;
219
220 ThreadSafepointState* _next;
221
222 void account_safe_thread();
223
224 public:
225 ThreadSafepointState(JavaThread *thread);
226
227 // Linked list support:
228 ThreadSafepointState* get_next() const { return _next; }
229 void set_next(ThreadSafepointState* value) { _next = value; }
230 ThreadSafepointState** next_ptr() { return &_next; }
231
232 // examine/restart
233 void examine_state_of_thread(uint64_t safepoint_count);
234 void restart();
235
236 // Query
237 JavaThread* thread() const { return _thread; }
238 bool is_running() const { return !_safepoint_safe; }
239
240 uint64_t get_safepoint_id() const;
241 void reset_safepoint_id();
242 void set_safepoint_id(uint64_t sid);
243
244 JavaThreadState orig_thread_state() const { return _orig_thread_state; }
245
246 // Support for safepoint timeout (debugging)
247 bool is_at_poll_safepoint() { return _at_poll_safepoint; }
248 void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; }
249
250 void handle_polling_page_exception();
251
252 // debugging
253 void print_on(outputStream* st) const;
254 void print() const;
255
256 // Initialize
257 static void create(JavaThread *thread);
258 static void destroy(JavaThread *thread);
259};
260
261class SafepointTracing : public AllStatic {
262private:
263 // Absolute
264 static jlong _last_safepoint_begin_time_ns;
265 static jlong _last_safepoint_sync_time_ns;
266 static jlong _last_safepoint_cleanup_time_ns;
267 static jlong _last_safepoint_end_time_ns;
268 // amount of ms since epoch
269 static jlong _last_safepoint_end_time_epoch_ms;
270 // Relative
271 static jlong _last_app_time_ns;
272
273 static int _nof_threads;
274 static int _nof_running;
275 static int _page_trap;
276
277 static VM_Operation::VMOp_Type _current_type;
278 static jlong _max_sync_time;
279 static jlong _max_vmop_time;
280 static uint64_t _op_count[VM_Operation::VMOp_Terminating];
281
282 static void statistics_log();
283
284public:
285 static void init();
286
287 static void begin(VM_Operation::VMOp_Type type);
288 static void synchronized(int nof_threads, int nof_running, int traps);
289 static void cleanup();
290 static void end();
291
292 static void statistics_exit_log();
293
294 static jlong time_since_last_safepoint_ms() {
295 return (os::javaTimeNanos() - _last_safepoint_end_time_ns) / (NANOUNITS / MILLIUNITS);
296 }
297
298 static jlong end_of_last_safepoint_epoch_ms() {
299 return _last_safepoint_end_time_epoch_ms;
300 }
301
302 static jlong start_of_safepoint() {
303 return _last_safepoint_begin_time_ns;
304 }
305};
306
307#endif // SHARE_RUNTIME_SAFEPOINT_HPP
308