1 /*
2 * Copyright (c) 1997, 2017, 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.
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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 comment 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 // The enums are listed in the order of the tasks when done serially.
79 enum SafepointCleanupTasks {
80 SAFEPOINT_CLEANUP_DEFLATE_MONITORS,
81 SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES,
82 SAFEPOINT_CLEANUP_COMPILATION_POLICY,
83 SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH,
84 SAFEPOINT_CLEANUP_STRING_TABLE_REHASH,
85 SAFEPOINT_CLEANUP_CLD_PURGE,
86 // Leave this one last.
87 SAFEPOINT_CLEANUP_NUM_TASKS
88 };
89
90 typedef struct {
91 float _time_stamp; // record when the current safepoint occurs in seconds
92 int _vmop_type; // type of VM operation triggers the safepoint
93 int _nof_total_threads; // total number of Java threads
94 int _nof_initial_running_threads; // total number of initially seen running threads
95 int _nof_threads_wait_to_block; // total number of threads waiting for to block
96 bool _page_armed; // true if polling page is armed, false otherwise
97 int _nof_threads_hit_page_trap; // total number of threads hitting the page trap
98 jlong _time_to_spin; // total time in millis spent in spinning
99 jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block
100 jlong _time_to_do_cleanups; // total time in millis spent in performing cleanups
101 jlong _time_to_sync; // total time in millis spent in getting to _synchronized
102 jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself
103 } SafepointStats;
104
105 private:
106 static volatile SynchronizeState _state; // Threads might read this flag directly, without acquiring the Threads_lock
107 static volatile int _waiting_to_block; // number of threads we are waiting for to block
108 static int _current_jni_active_count; // Counts the number of active critical natives during the safepoint
109
110 // This counter is used for fast versions of jni_Get<Primitive>Field.
111 // An even value means there is no ongoing safepoint operations.
112 // The counter is incremented ONLY at the beginning and end of each
113 // safepoint. The fact that Threads_lock is held throughout each pair of
114 // increments (at the beginning and end of each safepoint) guarantees
115 // race freedom.
116 public:
117 static volatile int _safepoint_counter;
118 private:
119 static long _end_of_last_safepoint; // Time of last safepoint in milliseconds
120
121 // Statistics
122 static jlong _safepoint_begin_time; // time when safepoint begins
123 static SafepointStats* _safepoint_stats; // array of SafepointStats struct
124 static int _cur_stat_index; // current index to the above array
125 static julong _safepoint_reasons[]; // safepoint count for each VM op
126 static julong _coalesced_vmop_count; // coalesced vmop count
127 static jlong _max_sync_time; // maximum sync time in nanos
128 static jlong _max_vmop_time; // maximum vm operation time in nanos
129 static float _ts_of_current_safepoint; // time stamp of current safepoint in seconds
130
131 static void begin_statistics(int nof_threads, int nof_running);
132 static void update_statistics_on_spin_end();
133 static void update_statistics_on_sync_end(jlong end_time);
134 static void update_statistics_on_cleanup_end(jlong end_time);
135 static void end_statistics(jlong end_time);
136 static void print_statistics();
137 inline static void inc_page_trap_count() {
138 Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap);
139 }
140
141 // For debug long safepoint
142 static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason);
143
144 public:
145
146 // Main entry points
147
148 // Roll all threads forward to safepoint. Must be called by the
149 // VMThread or CMS_thread.
150 static void begin();
151 static void end(); // Start all suspended threads again...
152
153 static bool safepoint_safe(JavaThread *thread, JavaThreadState state);
154
155 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state);
156
157 // Query
158 inline static bool is_at_safepoint() { return _state == _synchronized; }
159 inline static bool is_synchronizing() { return _state == _synchronizing; }
160 inline static int safepoint_counter() { return _safepoint_counter; }
161
162 inline static bool do_call_back() {
163 return (_state != _not_synchronized);
164 }
165
166 inline static void increment_jni_active_count() {
167 assert_locked_or_safepoint(Safepoint_lock);
168 _current_jni_active_count++;
169 }
170
171 // Called when a thread voluntarily blocks
172 static void block(JavaThread *thread);
173 static void signal_thread_at_safepoint() { _waiting_to_block--; }
174
175 // Exception handling for page polling
176 static void handle_polling_page_exception(JavaThread *thread);
177
178 // VM Thread interface for determining safepoint rate
179 static long last_non_safepoint_interval() {
180 return os::javaTimeMillis() - _end_of_last_safepoint;
181 }
182 static long end_of_last_safepoint() {
183 return _end_of_last_safepoint;
184 }
185 static bool is_cleanup_needed();
186 static void do_cleanup_tasks();
187
188 // Debugging
189 static void print_state() PRODUCT_RETURN;
190 static void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(1, 2) PRODUCT_RETURN;
191
192 static void deferred_initialize_stat();
193 static void print_stat_on_exit();
194 inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; }
195
196 static void set_is_at_safepoint() { _state = _synchronized; }
197 static void set_is_not_at_safepoint() { _state = _not_synchronized; }
198
199 // Assembly support
200 static address address_of_state() { return (address)&_state; }
201
202 static address safepoint_counter_addr() { return (address)&_safepoint_counter; }
203 };
204
205 // State class for a thread suspended at a safepoint
206 class ThreadSafepointState: public CHeapObj<mtInternal> {
207 public:
208 // These states are maintained by VM thread while threads are being brought
209 // to a safepoint. After SafepointSynchronize::end(), they are reset to
210 // _running.
211 enum suspend_type {
212 _running = 0, // Thread state not yet determined (i.e., not at a safepoint yet)
213 _at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock)
214 _call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm)
215 };
216 private:
217 volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint)
218 // Thread has called back the safepoint code (for debugging)
219 bool _has_called_back;
220
221 JavaThread * _thread;
222 volatile suspend_type _type;
223 JavaThreadState _orig_thread_state;
224
225
226 public:
227 ThreadSafepointState(JavaThread *thread);
228
229 // examine/roll-forward/restart
230 void examine_state_of_thread();
231 void roll_forward(suspend_type type);
232 void restart();
233
234 // Query
235 JavaThread* thread() const { return _thread; }
236 suspend_type type() const { return _type; }
237 bool is_running() const { return (_type==_running); }
238 JavaThreadState orig_thread_state() const { return _orig_thread_state; }
239
240 // Support for safepoint timeout (debugging)
241 bool has_called_back() const { return _has_called_back; }
242 void set_has_called_back(bool val) { _has_called_back = val; }
243 bool is_at_poll_safepoint() { return _at_poll_safepoint; }
244 void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; }
245
246 void handle_polling_page_exception();
247
248 // debugging
249 void print_on(outputStream* st) const;
250 void print() const { print_on(tty); }
251
252 // Initialize
253 static void create(JavaThread *thread);
254 static void destroy(JavaThread *thread);
255
256 void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(2, 3) {
257 if (ShowSafepointMsgs) {
258 va_list ap;
259 va_start(ap, format);
260 tty->vprint_cr(format, ap);
261 va_end(ap);
262 }
263 }
264 };
265
266
267
268 #endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP