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 class HandshakeOperation: public StackObj { 41 public: 42 virtual void do_handshake(JavaThread* thread) = 0; 43 virtual void cancel_handshake(JavaThread* thread) = 0; 44 }; 45 46 class HandshakeThreadsOperation: public HandshakeOperation { 47 Semaphore _done; 48 ThreadClosure* _thread_cl; 49 50 public: 51 HandshakeThreadsOperation(ThreadClosure* cl) : _done(0), _thread_cl(cl) {} 52 void do_handshake(JavaThread* thread); 53 void cancel_handshake(JavaThread* thread) { _done.signal(); }; 54 55 bool thread_has_completed() { return _done.trywait(); } 56 }; 57 58 class VM_Handshake: public VM_Operation { 59 HandshakeThreadsOperation* const _op; 60 const jlong _handshake_timeout; 61 public: 62 bool evaluate_at_safepoint() const { return false; } 63 64 bool evaluate_concurrently() const { return false; } 65 66 protected: 67 68 VM_Handshake(HandshakeThreadsOperation* op) : 69 _op(op), 70 _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)) {} 71 72 void set_handshake(JavaThread* target) { 73 target->set_handshake_operation(_op); 74 } 75 76 // This method returns true for threads completed their operation 77 // and true for threads canceled their operation. 78 // A cancellation can happen if the thread is exiting. 79 bool poll_for_completed_thread() { return _op->thread_has_completed(); } 80 81 bool handshake_has_timed_out(jlong start_time); 82 static void handle_timeout(); 83 }; 84 85 bool VM_Handshake::handshake_has_timed_out(jlong start_time) { 86 // Check if handshake operation has timed out 87 if (_handshake_timeout > 0) { 88 return os::elapsed_counter() >= (start_time + _handshake_timeout); 89 } 90 return false; 91 } 92 93 void VM_Handshake::handle_timeout() { 94 LogStreamHandle(Warning, handshake) log_stream; 95 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) { 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 ThreadsListHandle tlh; 118 if (tlh.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 // We need to re-think this with SMR ThreadsList. 140 // There is an assumption in the code that the Threads_lock should be 141 // locked during certain phases. 142 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 143 ThreadsListHandle tlh; 144 if (tlh.includes(_target)) { 145 // Warning _target's address might be re-used. 146 // handshake_process_by_vmthread will check the semaphore for us again. 147 // Since we can't have more then one handshake in flight a reuse of 148 // _target's address should be okay since the new thread will not have 149 // an operation. 150 _target->handshake_process_by_vmthread(); 151 } else { 152 // We can't warn here since the thread does cancel_handshake after 153 // it has been removed from the ThreadsList. So we should just keep 154 // looping here until while below returns false. If we have a bug, 155 // then we hang here, which is good for debugging. 156 } 157 } while (!poll_for_completed_thread()); 158 } 159 160 VMOp_Type type() const { return VMOp_HandshakeOneThread; } 161 162 bool thread_alive() const { return _thread_alive; } 163 }; 164 165 class VM_HandshakeAllThreads: public VM_Handshake { 166 public: 167 VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {} 168 169 void doit() { 170 TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake)); 171 172 int number_of_threads_issued = 0; 173 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) { 174 set_handshake(thr); 175 number_of_threads_issued++; 176 } 177 178 if (number_of_threads_issued < 1) { 179 log_debug(handshake)("No threads to handshake."); 180 return; 181 } 182 183 if (!UseMembar) { 184 os::serialize_thread_states(); 185 } 186 187 log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread"); 188 const jlong start_time = os::elapsed_counter(); 189 int number_of_threads_completed = 0; 190 do { 191 // Check if handshake operation has timed out 192 if (handshake_has_timed_out(start_time)) { 193 handle_timeout(); 194 } 195 196 // Have VM thread perform the handshake operation for blocked threads. 197 // Observing a blocked state may of course be transient but the processing is guarded 198 // by semaphores and we optimistically begin by working on the blocked threads 199 { 200 // We need to re-think this with SMR ThreadsList. 201 // There is an assumption in the code that the Threads_lock should 202 // be locked during certain phases. 203 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 204 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) { 205 // A new thread on the ThreadsList will not have an operation, 206 // hence it is skipped in handshake_process_by_vmthread. 207 thr->handshake_process_by_vmthread(); 208 } 209 } 210 211 while (poll_for_completed_thread()) { 212 // Includes canceled operations by exiting threads. 213 number_of_threads_completed++; 214 } 215 216 } while (number_of_threads_issued != number_of_threads_completed); 217 } 218 219 VMOp_Type type() const { return VMOp_HandshakeAllThreads; } 220 }; 221 222 class VM_HandshakeFallbackOperation : public VM_Operation { 223 ThreadClosure* _thread_cl; 224 Thread* _target_thread; 225 bool _all_threads; 226 bool _thread_alive; 227 public: 228 VM_HandshakeFallbackOperation(ThreadClosure* cl) : 229 _thread_cl(cl), _target_thread(NULL), _all_threads(true), _thread_alive(true) {} 230 VM_HandshakeFallbackOperation(ThreadClosure* cl, Thread* target) : 231 _thread_cl(cl), _target_thread(target), _all_threads(false), _thread_alive(false) {} 232 233 void doit() { 234 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 235 if (_all_threads || t == _target_thread) { 236 if (t == _target_thread) { 237 _thread_alive = true; 238 } 239 _thread_cl->do_thread(t); 240 } 241 } 242 } 243 244 VMOp_Type type() const { return VMOp_HandshakeFallback; } 245 bool thread_alive() const { return _thread_alive; } 246 }; 247 248 #undef ALL_JAVA_THREADS 249 250 void HandshakeThreadsOperation::do_handshake(JavaThread* thread) { 251 ResourceMark rm; 252 FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s", 253 p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread())); 254 TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task)); 255 _thread_cl->do_thread(thread); 256 257 // Use the semaphore to inform the VM thread that we have completed the operation 258 _done.signal(); 259 } 260 261 void Handshake::execute(ThreadClosure* thread_cl) { 262 if (ThreadLocalHandshakes) { 263 HandshakeThreadsOperation cto(thread_cl); 264 VM_HandshakeAllThreads handshake(&cto); 265 VMThread::execute(&handshake); 266 } else { 267 VM_HandshakeFallbackOperation op(thread_cl); 268 VMThread::execute(&op); 269 } 270 } 271 272 bool Handshake::execute(ThreadClosure* thread_cl, JavaThread* target) { 273 if (ThreadLocalHandshakes) { 274 HandshakeThreadsOperation cto(thread_cl); 275 VM_HandshakeOneThread handshake(&cto, target); 276 VMThread::execute(&handshake); 277 return handshake.thread_alive(); 278 } else { 279 VM_HandshakeFallbackOperation op(thread_cl, target); 280 VMThread::execute(&op); 281 return op.thread_alive(); 282 } 283 } 284 285 HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _vmthread_holds_semaphore(false), _thread_in_process_handshake(false) {} 286 287 void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) { 288 _operation = op; 289 SafepointMechanism::arm_local_poll(target); 290 } 291 292 void HandshakeState::clear_handshake(JavaThread* target) { 293 _operation = NULL; 294 SafepointMechanism::disarm_local_poll(target); 295 } 296 297 void HandshakeState::process_self_inner(JavaThread* thread) { 298 assert(Thread::current() == thread, "should call from thread"); 299 CautiouslyPreserveExceptionMark pem(thread); 300 ThreadInVMForHandshake tivm(thread); 301 if (!_semaphore.trywait()) { 302 ThreadBlockInVM tbivm(thread); 303 _semaphore.wait(); 304 } 305 if (has_operation()) { 306 HandshakeOperation* op = _operation; 307 clear_handshake(thread); 308 if (op != NULL) { 309 op->do_handshake(thread); 310 } 311 } 312 _semaphore.signal(); 313 } 314 315 void HandshakeState::cancel_inner(JavaThread* thread) { 316 assert(Thread::current() == thread, "should call from thread"); 317 assert(thread->thread_state() == _thread_in_vm, "must be in vm state"); 318 #ifdef DEBUG 319 { 320 ThreadsListHandle tlh; 321 assert(!tlh.includes(_target), "java thread must not be on threads list"); 322 } 323 #endif 324 HandshakeOperation* op = _operation; 325 clear_handshake(thread); 326 if (op != NULL) { 327 op->cancel_handshake(thread); 328 } 329 } 330 331 bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) { 332 return SafepointSynchronize::safepoint_safe(target, target->thread_state()); 333 } 334 335 bool HandshakeState::claim_handshake_for_vmthread() { 336 if (_semaphore.trywait()) { 337 if (has_operation()) { 338 _vmthread_holds_semaphore = true; 339 } else { 340 _semaphore.signal(); 341 } 342 } 343 return _vmthread_holds_semaphore; 344 } 345 346 void HandshakeState::process_by_vmthread(JavaThread* target) { 347 assert(Thread::current()->is_VM_thread(), "should call from vm thread"); 348 349 if (!has_operation()) { 350 // JT has already cleared its handshake 351 return; 352 } 353 354 if (!vmthread_can_process_handshake(target)) { 355 // JT is observed in an unsafe state, it must notice the handshake itself 356 return; 357 } 358 359 // If we own the semaphore at this point and while owning the semaphore 360 // can observe a safe state the thread cannot possibly continue without 361 // getting caught by the semaphore. 362 if (claim_handshake_for_vmthread() && vmthread_can_process_handshake(target)) { 363 guarantee(!_semaphore.trywait(), "we should already own the semaphore"); 364 365 _operation->do_handshake(target); 366 clear_handshake(target); 367 _vmthread_holds_semaphore = false; 368 // Release the thread 369 _semaphore.signal(); 370 } 371 }