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
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;
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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 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 acquiring 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
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 voluntarily 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;
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