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.inline.hpp" 31 #include "runtime/orderAccess.hpp" 32 #include "runtime/osThread.hpp" 33 #include "runtime/semaphore.inline.hpp" 34 #include "runtime/task.hpp" 35 #include "runtime/timerTrace.hpp" 36 #include "runtime/thread.hpp" 37 #include "runtime/vmThread.hpp" 38 #include "utilities/formatBuffer.hpp" 39 #include "utilities/preserveException.hpp" 40 41 class HandshakeOperation: public StackObj { 42 public: 43 virtual void do_handshake(JavaThread* thread) = 0; 44 virtual void cancel_handshake(JavaThread* thread) = 0; 45 }; 46 47 class HandshakeThreadsOperation: public HandshakeOperation { 48 static Semaphore _done; 49 ThreadClosure* _thread_cl; 50 51 public: 52 HandshakeThreadsOperation(ThreadClosure* cl) : _thread_cl(cl) {} 53 void do_handshake(JavaThread* thread); 54 void cancel_handshake(JavaThread* thread) { _done.signal(); }; 55 56 bool thread_has_completed() { return _done.trywait(); } 57 58 #ifdef ASSERT 59 void check_state() { 60 assert(!_done.trywait(), "Must be zero"); 61 } 62 #endif 63 }; 64 65 Semaphore HandshakeThreadsOperation::_done(0); 66 67 class VM_Handshake: public VM_Operation { 68 const jlong _handshake_timeout; 69 public: 70 bool evaluate_at_safepoint() const { return false; } 71 72 bool evaluate_concurrently() const { return false; } 73 74 protected: 75 HandshakeThreadsOperation* const _op; 76 77 VM_Handshake(HandshakeThreadsOperation* op) : 78 _op(op), 79 _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)) {} 80 81 void set_handshake(JavaThread* target) { 82 target->set_handshake_operation(_op); 83 } 84 85 // This method returns true for threads completed their operation 86 // and true for threads canceled their operation. 87 // A cancellation can happen if the thread is exiting. 88 bool poll_for_completed_thread() { return _op->thread_has_completed(); } 89 90 bool handshake_has_timed_out(jlong start_time); 91 static void handle_timeout(); 92 }; 93 94 bool VM_Handshake::handshake_has_timed_out(jlong start_time) { 95 // Check if handshake operation has timed out 96 if (_handshake_timeout > 0) { 97 return os::elapsed_counter() >= (start_time + _handshake_timeout); 98 } 99 return false; 100 } 101 102 void VM_Handshake::handle_timeout() { 103 LogStreamHandle(Warning, handshake) log_stream; 104 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) { 105 if (thr->has_handshake()) { 106 log_stream.print("Thread " PTR_FORMAT " has not cleared its handshake op", p2i(thr)); 107 thr->print_thread_state_on(&log_stream); 108 } 109 } 110 log_stream.flush(); 111 fatal("Handshake operation timed out"); 112 } 113 114 class VM_HandshakeOneThread: public VM_Handshake { 115 JavaThread* _target; 116 bool _thread_alive; 117 public: 118 VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) : 119 VM_Handshake(op), _target(target), _thread_alive(false) {} 120 121 void doit() { 122 DEBUG_ONLY(_op->check_state();) 123 TraceTime timer("Performing single-target operation (vmoperation doit)", TRACETIME_LOG(Info, handshake)); 124 125 { 126 ThreadsListHandle tlh; 127 if (tlh.includes(_target)) { 128 set_handshake(_target); 129 _thread_alive = true; 130 } 131 } 132 133 if (!_thread_alive) { 134 return; 135 } 136 137 if (!UseMembar) { 138 os::serialize_thread_states(); 139 } 140 141 log_trace(handshake)("Thread signaled, begin processing by VMThtread"); 142 jlong start_time = os::elapsed_counter(); 143 do { 144 if (handshake_has_timed_out(start_time)) { 145 handle_timeout(); 146 } 147 148 // We need to re-think this with SMR ThreadsList. 149 // There is an assumption in the code that the Threads_lock should be 150 // locked during certain phases. 151 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 152 ThreadsListHandle tlh; 153 if (tlh.includes(_target)) { 154 // Warning _target's address might be re-used. 155 // handshake_process_by_vmthread will check the semaphore for us again. 156 // Since we can't have more then one handshake in flight a reuse of 157 // _target's address should be okay since the new thread will not have 158 // an operation. 159 _target->handshake_process_by_vmthread(); 160 } else { 161 // We can't warn here since the thread does cancel_handshake after 162 // it has been removed from the ThreadsList. So we should just keep 163 // looping here until while below returns false. If we have a bug, 164 // then we hang here, which is good for debugging. 165 } 166 } while (!poll_for_completed_thread()); 167 DEBUG_ONLY(_op->check_state();) 168 } 169 170 VMOp_Type type() const { return VMOp_HandshakeOneThread; } 171 172 bool thread_alive() const { return _thread_alive; } 173 }; 174 175 class VM_HandshakeAllThreads: public VM_Handshake { 176 public: 177 VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {} 178 179 void doit() { 180 DEBUG_ONLY(_op->check_state();) 181 TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake)); 182 183 int number_of_threads_issued = 0; 184 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) { 185 set_handshake(thr); 186 number_of_threads_issued++; 187 } 188 189 if (number_of_threads_issued < 1) { 190 log_debug(handshake)("No threads to handshake."); 191 return; 192 } 193 194 if (!UseMembar) { 195 os::serialize_thread_states(); 196 } 197 198 log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread"); 199 const jlong start_time = os::elapsed_counter(); 200 int number_of_threads_completed = 0; 201 do { 202 // Check if handshake operation has timed out 203 if (handshake_has_timed_out(start_time)) { 204 handle_timeout(); 205 } 206 207 // Have VM thread perform the handshake operation for blocked threads. 208 // Observing a blocked state may of course be transient but the processing is guarded 209 // by semaphores and we optimistically begin by working on the blocked threads 210 { 211 // We need to re-think this with SMR ThreadsList. 212 // There is an assumption in the code that the Threads_lock should 213 // be locked during certain phases. 214 MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag); 215 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) { 216 // A new thread on the ThreadsList will not have an operation, 217 // hence it is skipped in handshake_process_by_vmthread. 218 thr->handshake_process_by_vmthread(); 219 } 220 } 221 222 while (poll_for_completed_thread()) { 223 // Includes canceled operations by exiting threads. 224 number_of_threads_completed++; 225 } 226 227 } while (number_of_threads_issued > number_of_threads_completed); 228 assert(number_of_threads_issued == number_of_threads_completed, "Must be the same"); 229 DEBUG_ONLY(_op->check_state();) 230 } 231 232 VMOp_Type type() const { return VMOp_HandshakeAllThreads; } 233 }; 234 235 class VM_HandshakeFallbackOperation : public VM_Operation { 236 ThreadClosure* _thread_cl; 237 Thread* _target_thread; 238 bool _all_threads; 239 bool _thread_alive; 240 public: 241 VM_HandshakeFallbackOperation(ThreadClosure* cl) : 242 _thread_cl(cl), _target_thread(NULL), _all_threads(true), _thread_alive(true) {} 243 VM_HandshakeFallbackOperation(ThreadClosure* cl, Thread* target) : 244 _thread_cl(cl), _target_thread(target), _all_threads(false), _thread_alive(false) {} 245 246 void doit() { 247 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 248 if (_all_threads || t == _target_thread) { 249 if (t == _target_thread) { 250 _thread_alive = true; 251 } 252 _thread_cl->do_thread(t); 253 } 254 } 255 } 256 257 VMOp_Type type() const { return VMOp_HandshakeFallback; } 258 bool thread_alive() const { return _thread_alive; } 259 }; 260 261 void HandshakeThreadsOperation::do_handshake(JavaThread* thread) { 262 ResourceMark rm; 263 FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s", 264 p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread())); 265 TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task)); 266 _thread_cl->do_thread(thread); 267 268 // Use the semaphore to inform the VM thread that we have completed the operation 269 _done.signal(); 270 } 271 272 void Handshake::execute(ThreadClosure* thread_cl) { 273 if (ThreadLocalHandshakes) { 274 HandshakeThreadsOperation cto(thread_cl); 275 VM_HandshakeAllThreads handshake(&cto); 276 VMThread::execute(&handshake); 277 } else { 278 VM_HandshakeFallbackOperation op(thread_cl); 279 VMThread::execute(&op); 280 } 281 } 282 283 bool Handshake::execute(ThreadClosure* thread_cl, JavaThread* target) { 284 if (ThreadLocalHandshakes) { 285 HandshakeThreadsOperation cto(thread_cl); 286 VM_HandshakeOneThread handshake(&cto, target); 287 VMThread::execute(&handshake); 288 return handshake.thread_alive(); 289 } else { 290 VM_HandshakeFallbackOperation op(thread_cl, target); 291 VMThread::execute(&op); 292 return op.thread_alive(); 293 } 294 } 295 296 HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _thread_in_process_handshake(false) {} 297 298 void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) { 299 _operation = op; 300 SafepointMechanism::arm_local_poll(target); 301 } 302 303 void HandshakeState::clear_handshake(JavaThread* target) { 304 _operation = NULL; 305 SafepointMechanism::disarm_local_poll(target); 306 } 307 308 void HandshakeState::process_self_inner(JavaThread* thread) { 309 assert(Thread::current() == thread, "should call from thread"); 310 311 // If thread is not on threads list but armed, we cancel. 312 if (thread->is_terminated() && thread->has_handshake()) { 313 assert(false, "Should not happen"); 314 thread->cancel_handshake(); 315 return; 316 } 317 318 CautiouslyPreserveExceptionMark pem(thread); 319 ThreadInVMForHandshake tivm(thread); 320 if (!_semaphore.trywait()) { 321 _semaphore.wait_with_safepoint_check(thread); 322 } 323 HandshakeOperation* op = OrderAccess::load_acquire(&_operation); 324 if (op != NULL) { 325 // Disarm before execute the operation 326 clear_handshake(thread); 327 op->do_handshake(thread); 328 } 329 _semaphore.signal(); 330 } 331 332 void HandshakeState::cancel_inner(JavaThread* thread) { 333 assert(Thread::current() == thread, "should call from thread"); 334 assert(thread->thread_state() == _thread_in_vm, "must be in vm state"); 335 HandshakeOperation* op = _operation; 336 clear_handshake(thread); 337 if (op != NULL) { 338 op->cancel_handshake(thread); 339 } 340 } 341 342 bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) { 343 return SafepointSynchronize::safepoint_safe(target, target->thread_state()); 344 } 345 346 bool HandshakeState::claim_handshake_for_vmthread() { 347 if (!_semaphore.trywait()) { 348 return false; 349 } 350 if (has_operation()) { 351 return true; 352 } 353 _semaphore.signal(); 354 return false; 355 } 356 357 void HandshakeState::process_by_vmthread(JavaThread* target) { 358 assert(Thread::current()->is_VM_thread(), "should call from vm thread"); 359 360 if (!has_operation()) { 361 // JT has already cleared its handshake 362 return; 363 } 364 365 if (!vmthread_can_process_handshake(target)) { 366 // JT is observed in an unsafe state, it must notice the handshake itself 367 return; 368 } 369 370 // If we own the semaphore at this point and while owning the semaphore 371 // can observe a safe state the thread cannot possibly continue without 372 // getting caught by the semaphore. 373 if (claim_handshake_for_vmthread()) { 374 if(!vmthread_can_process_handshake(target)) { 375 _semaphore.signal(); 376 return; 377 } 378 guarantee(!_semaphore.trywait(), "we should already own the semaphore"); 379 380 _operation->do_handshake(target); 381 // Disarm after VM thread have executed the operation. 382 clear_handshake(target); 383 // Release the thread 384 _semaphore.signal(); 385 } 386 }