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