1 /*
2 * Copyright (c) 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.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "logging/log.hpp"
27 #include "logging/logStream.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "runtime/handshake.hpp"
30 #include "runtime/interfaceSupport.hpp"
31 #include "runtime/osThread.hpp"
32 #include "runtime/semaphore.hpp"
33 #include "runtime/task.hpp"
34 #include "runtime/timerTrace.hpp"
35 #include "runtime/thread.hpp"
36 #include "runtime/vmThread.hpp"
37 #include "utilities/formatBuffer.hpp"
38 #include "utilities/preserveException.hpp"
39
40 #define ALL_JAVA_THREADS(X) for (JavaThread* X = Threads::first(); X; X = X->next())
41
42 class HandshakeOperation: public StackObj {
43 public:
44 virtual void do_handshake(JavaThread* thread) = 0;
45 virtual void cancel_handshake(JavaThread* thread) = 0;
46 };
47
48 class HandshakeThreadsOperation: public HandshakeOperation {
49 Semaphore _done;
50 ThreadClosure* _thread_cl;
51
52 public:
53 HandshakeThreadsOperation(ThreadClosure* cl) : _done(0), _thread_cl(cl) {}
54 void do_handshake(JavaThread* thread);
55 void cancel_handshake(JavaThread* thread) { _done.signal(); };
56
57 bool thread_has_completed() { return _done.trywait(); }
58 };
59
60 class VM_Handshake: public VM_Operation {
61 HandshakeThreadsOperation* const _op;
62 const jlong _handshake_timeout;
63 public:
64 bool evaluate_at_safepoint() const { return false; }
65
66 bool evaluate_concurrently() const { return false; }
67
68 protected:
69
70 VM_Handshake(HandshakeThreadsOperation* op) :
71 _op(op),
72 _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)) {}
73
74 void set_handshake(JavaThread* target) {
75 target->set_handshake_operation(_op);
76 }
77
78 // This method returns true for threads completed their operation
79 // and true for threads canceled their operation.
80 // A cancellation can happen if the thread is exiting.
81 bool poll_for_completed_thread() { return _op->thread_has_completed(); }
82
83 bool handshake_has_timed_out(jlong start_time);
84 static void handle_timeout();
85 };
86
87 bool VM_Handshake::handshake_has_timed_out(jlong start_time) {
88 // Check if handshake operation has timed out
89 if (_handshake_timeout > 0) {
90 return os::elapsed_counter() >= (start_time + _handshake_timeout);
91 }
92 return false;
93 }
94
95 void VM_Handshake::handle_timeout() {
96 LogStreamHandle(Warning, handshake) log_stream;
97 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
98 ALL_JAVA_THREADS(thr) {
99 if (thr->has_handshake()) {
100 log_stream.print("Thread " PTR_FORMAT " has not cleared its handshake op", p2i(thr));
101 thr->print_thread_state_on(&log_stream);
102 }
103 }
104 log_stream.flush();
105 fatal("Handshake operation timed out");
106 }
107
108
109 class VM_HandshakeOneThread: public VM_Handshake {
110 JavaThread* _target;
111 bool _thread_alive;
112 public:
113 VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) :
114 VM_Handshake(op), _target(target), _thread_alive(false) {}
115
116 void doit() {
117 TraceTime timer("Performing single-target operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
118
119 {
120 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
121 if (Threads::includes(_target)) {
122 set_handshake(_target);
123 _thread_alive = true;
124 }
125 }
126
127 if (!_thread_alive) {
128 return;
129 }
130
131 if (!UseMembar) {
132 os::serialize_thread_states();
133 }
134
135 log_trace(handshake)("Thread signaled, begin processing by VMThtread");
136 jlong start_time = os::elapsed_counter();
137 do {
138 if (handshake_has_timed_out(start_time)) {
139 handle_timeout();
140 }
141
142 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
143 _target->handshake_process_by_vmthread();
144
145 } while (!poll_for_completed_thread());
146 }
147
148 VMOp_Type type() const { return VMOp_HandshakeOneThread; }
149
150 bool thread_alive() const { return _thread_alive; }
151 };
152
153 class VM_HandshakeAllThreads: public VM_Handshake {
154 public:
155 VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {}
156
157 void doit() {
158 TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
159
160 int number_of_threads_issued = -1;
161 int number_of_threads_completed = 0;
162 {
163 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
164 number_of_threads_issued = Threads::number_of_threads();
165
166 ALL_JAVA_THREADS(thr) {
167 set_handshake(thr);
168 }
169 }
170
171 if (!UseMembar) {
172 os::serialize_thread_states();
173 }
174
175 log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread");
176 const jlong start_time = os::elapsed_counter();
177 do {
178 // Check if handshake operation has timed out
179 if (handshake_has_timed_out(start_time)) {
180 handle_timeout();
181 }
182
183 // Have VM thread perform the handshake operation for blocked threads.
184 // Observing a blocked state may of course be transient but the processing is guarded
185 // by semaphores and we optimistically begin by working on the blocked threads
186 {
187 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
188 ALL_JAVA_THREADS(thr) {
189 thr->handshake_process_by_vmthread();
190 }
191 }
192
193 while (poll_for_completed_thread()) {
194 number_of_threads_completed++;
195 }
196
197 } while (number_of_threads_issued != number_of_threads_completed);
198 }
199
200 VMOp_Type type() const { return VMOp_HandshakeAllThreads; }
201 };
202
203 class VM_HandshakeFallbackOperation : public VM_Operation {
204 ThreadClosure* _thread_cl;
205 Thread* _target_thread;
206 bool _all_threads;
207 bool _thread_alive;
208 public:
209 VM_HandshakeFallbackOperation(ThreadClosure* cl) :
210 _thread_cl(cl), _target_thread(NULL), _all_threads(true), _thread_alive(true) {}
211 VM_HandshakeFallbackOperation(ThreadClosure* cl, Thread* target) :
212 _thread_cl(cl), _target_thread(target), _all_threads(false), _thread_alive(false) {}
213
214 void doit() {
215 ALL_JAVA_THREADS(t) {
216 if (_all_threads || t == _target_thread) {
217 if (t == _target_thread) {
218 _thread_alive = true;
219 }
220 _thread_cl->do_thread(t);
221 }
222 }
223 }
224
225 VMOp_Type type() const { return VMOp_HandshakeFallback; }
226 bool thread_alive() const { return _thread_alive; }
227 };
228
229 #undef ALL_JAVA_THREADS
230
231 void HandshakeThreadsOperation::do_handshake(JavaThread* thread) {
232 ResourceMark rm;
233 FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s",
234 p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread()));
235 TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task));
236 _thread_cl->do_thread(thread);
237
238 // Use the semaphore to inform the VM thread that we have completed the operation
239 _done.signal();
240 }
241
242 void Handshake::execute(ThreadClosure* thread_cl) {
243 if (ThreadLocalHandshakes) {
244 HandshakeThreadsOperation cto(thread_cl);
245 VM_HandshakeAllThreads handshake(&cto);
246 VMThread::execute(&handshake);
247 } else {
248 VM_HandshakeFallbackOperation op(thread_cl);
249 VMThread::execute(&op);
250 }
251 }
252
253 bool Handshake::execute(ThreadClosure* thread_cl, JavaThread* target) {
254 if (ThreadLocalHandshakes) {
255 HandshakeThreadsOperation cto(thread_cl);
256 VM_HandshakeOneThread handshake(&cto, target);
257 VMThread::execute(&handshake);
258 return handshake.thread_alive();
259 } else {
260 VM_HandshakeFallbackOperation op(thread_cl, target);
261 VMThread::execute(&op);
262 return op.thread_alive();
263 }
264 }
265
266 HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _vmthread_holds_semaphore(false), _thread_in_process_handshake(false) {}
267
268 void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) {
269 _operation = op;
270 SafepointMechanism::arm_local_poll(target);
271 }
272
273 void HandshakeState::clear_handshake(JavaThread* target) {
274 _operation = NULL;
275 SafepointMechanism::disarm_local_poll(target);
276 }
277
278 void HandshakeState::process_self_inner(JavaThread* thread) {
279 assert(Thread::current() == thread, "should call from thread");
280 CautiouslyPreserveExceptionMark pem(thread);
281 ThreadInVMForHandshake tivm(thread);
282 if (!_semaphore.trywait()) {
283 ThreadBlockInVM tbivm(thread);
284 _semaphore.wait();
285 }
286 if (has_operation()) {
287 HandshakeOperation* op = _operation;
288 clear_handshake(thread);
289 if (op != NULL) {
290 op->do_handshake(thread);
291 }
292 }
293 _semaphore.signal();
294 }
295
296 void HandshakeState::cancel_inner(JavaThread* thread) {
297 assert(Thread::current() == thread, "should call from thread");
298 assert(thread->thread_state() == _thread_in_vm, "must be in vm state");
299 #ifdef DEBUG
300 {
301 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
302 assert(!Threads::includes(thread), "java thread must not be on threads list");
303 }
304 #endif
305 HandshakeOperation* op = _operation;
306 clear_handshake(thread);
307 if (op != NULL) {
308 op->cancel_handshake(thread);
309 }
310 }
311
312 bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) {
313 return SafepointSynchronize::safepoint_safe(target, target->thread_state());
314 }
315
316 bool HandshakeState::claim_handshake_for_vmthread() {
317 if (_semaphore.trywait()) {
318 if (has_operation()) {
319 _vmthread_holds_semaphore = true;
320 } else {
321 _semaphore.signal();
322 }
323 }
324 return _vmthread_holds_semaphore;
325 }
326
327 void HandshakeState::process_by_vmthread(JavaThread* target) {
328 assert(Thread::current()->is_VM_thread(), "should call from vm thread");
329
330 if (!has_operation()) {
331 // JT has already cleared its handshake
332 return;
333 }
334
335 if (!vmthread_can_process_handshake(target)) {
336 // JT is observed in an unsafe state, it must notice the handshake itself
337 return;
338 }
339
340 // If we own the semaphore at this point and while owning the semaphore
341 // can observe a safe state the thread cannot possibly continue without
342 // getting caught by the semaphore.
343 if (claim_handshake_for_vmthread() && vmthread_can_process_handshake(target)) {
344 guarantee(!_semaphore.trywait(), "we should already own the semaphore");
345
346 _operation->do_handshake(target);
347 clear_handshake(target);
348 _vmthread_holds_semaphore = false;
349 // Release the thread
350 _semaphore.signal();
351 }
352 }