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.
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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/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 // Statistics
110 static jlong _safepoint_begin_time; // time when safepoint begins
111 static julong _safepoint_reasons[]; // safepoint count for each VM op
112 static julong _coalesced_vmop_count; // coalesced vmop count
113 static jlong _max_sync_time; // maximum sync time in nanos
114 static jlong _max_vmop_time; // maximum vm operation time in nanos
115 static float _ts_of_current_safepoint; // time stamp of current safepoint in seconds
116 static volatile int _nof_threads_hit_polling_page; // threads hitting the polling page
117
118 static void begin_statistics(int nof_threads, int nof_running);
119 static void update_statistics_on_spin_end();
120 static void update_statistics_on_sync_end(jlong end_time);
121 static void update_statistics_on_cleanup_end(jlong end_time);
122 static void end_statistics(jlong end_time);
123 static void print_statistics();
124
125 // For debug long safepoint
126 static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason);
127
128 public:
129
130 // Main entry points
131
132 // Roll all threads forward to safepoint. Must be called by the
133 // VMThread or CMS_thread.
134 static void begin();
135 static void end(); // Start all suspended threads again...
136
137 static bool safepoint_safe(JavaThread *thread, JavaThreadState state);
138
139 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state);
140
141 // Query
142 inline static bool is_at_safepoint() { return _state == _synchronized; }
143 inline static bool is_synchronizing() { return _state == _synchronizing; }
144 inline static int safepoint_counter() { return _safepoint_counter; }
145
146 inline static void increment_jni_active_count() {
147 assert_locked_or_safepoint(Safepoint_lock);
148 _current_jni_active_count++;
149 }
150
151 private:
152 inline static bool do_call_back() {
153 return (_state != _not_synchronized);
154 }
155
156 // Called when a thread voluntarily blocks
157 static void block(JavaThread *thread);
158
159 friend class SafepointMechanism;
160
161 public:
162 static void signal_thread_at_safepoint() { _waiting_to_block--; }
163
164 // Exception handling for page polling
165 static void handle_polling_page_exception(JavaThread *thread);
166
167 // VM Thread interface for determining safepoint rate
168 static long last_non_safepoint_interval() {
169 return os::javaTimeMillis() - _end_of_last_safepoint;
170 }
171 static long end_of_last_safepoint() {
172 return _end_of_last_safepoint;
173 }
174 static bool is_cleanup_needed();
175 static void do_cleanup_tasks();
176
177 static void print_stat_on_exit();
178 inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; }
179
180 static void set_is_at_safepoint() { _state = _synchronized; }
181 static void set_is_not_at_safepoint() { _state = _not_synchronized; }
182
183 // Assembly support
184 static address address_of_state() { return (address)&_state; }
185
186 static address safepoint_counter_addr() { return (address)&_safepoint_counter; }
187
188 // This method is only used for -Xconcurrentio support.
189 static void set_defer_thr_suspend_loop_count() {
190 _defer_thr_suspend_loop_count = 1;
191 }
192 };
193
194 // Some helper assert macros for safepoint checks.
195
196 #define assert_at_safepoint() \
197 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint")
198
199 #define assert_at_safepoint_msg(...) \
200 assert(SafepointSynchronize::is_at_safepoint(), __VA_ARGS__)
201
202 #define assert_not_at_safepoint() \
203 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint")
204
205 #define assert_not_at_safepoint_msg(...) \
206 assert(!SafepointSynchronize::is_at_safepoint(), __VA_ARGS__)
207
208 // State class for a thread suspended at a safepoint
209 class ThreadSafepointState: public CHeapObj<mtInternal> {
210 public:
211 // These states are maintained by VM thread while threads are being brought
212 // to a safepoint. After SafepointSynchronize::end(), they are reset to
213 // _running.
214 enum suspend_type {
215 _running = 0, // Thread state not yet determined (i.e., not at a safepoint yet)
216 _at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock)
217 _call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm)
218 };
219 private:
220 volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint)
221 // Thread has called back the safepoint code (for debugging)
222 bool _has_called_back;
223
224 JavaThread * _thread;
225 volatile suspend_type _type;
226 JavaThreadState _orig_thread_state;
227
228
229 public:
230 ThreadSafepointState(JavaThread *thread);
231
232 // examine/roll-forward/restart
233 void examine_state_of_thread();
234 void roll_forward(suspend_type type);
235 void restart();
236
237 // Query
238 JavaThread* thread() const { return _thread; }
239 suspend_type type() const { return _type; }
240 bool is_running() const { return (_type==_running); }
241 JavaThreadState orig_thread_state() const { return _orig_thread_state; }
242
243 // Support for safepoint timeout (debugging)
244 bool has_called_back() const { return _has_called_back; }
245 void set_has_called_back(bool val) { _has_called_back = val; }
246 bool is_at_poll_safepoint() { return _at_poll_safepoint; }
247 void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; }
248
249 void handle_polling_page_exception();
250
251 // debugging
252 void print_on(outputStream* st) const;
253 void print() const { print_on(tty); }
254
255 // Initialize
256 static void create(JavaThread *thread);
257 static void destroy(JavaThread *thread);
258 };
259
260
261
262 #endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP