1 /* 2 * Copyright (c) 2017, 2019, 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/atomic.hpp" 30 #include "runtime/handshake.hpp" 31 #include "runtime/interfaceSupport.inline.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 }; 45 46 class HandshakeThreadsOperation: public HandshakeOperation { 47 static Semaphore _done; 48 HandshakeClosure* _handshake_cl; 49 bool _executed; 50 public: 51 HandshakeThreadsOperation(HandshakeClosure* cl) : _handshake_cl(cl), _executed(false) {} 52 void do_handshake(JavaThread* thread); 53 bool thread_has_completed() { return _done.trywait(); } 54 bool executed() const { return _executed; } 55 56 #ifdef ASSERT 57 void check_state() { 58 assert(!_done.trywait(), "Must be zero"); 59 } 60 #endif 61 }; 62 63 Semaphore HandshakeThreadsOperation::_done(0); 64 65 class VM_Handshake: public VM_Operation { 66 const jlong _handshake_timeout; 67 public: 68 bool evaluate_at_safepoint() const { return false; } 69 70 bool evaluate_concurrently() const { return false; } 71 72 protected: 73 HandshakeThreadsOperation* const _op; 74 75 VM_Handshake(HandshakeThreadsOperation* op) : 76 _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)), _op(op) {} 77 78 void set_handshake(JavaThread* target) { 79 target->set_handshake_operation(_op); 80 } 81 82 // This method returns true for threads completed their operation 83 // and true for threads canceled their operation. 84 // A cancellation can happen if the thread is exiting. 85 bool poll_for_completed_thread() { return _op->thread_has_completed(); } 86 87 bool handshake_has_timed_out(jlong start_time); 88 static void handle_timeout(); 89 }; 90 91 bool VM_Handshake::handshake_has_timed_out(jlong start_time) { 92 // Check if handshake operation has timed out 93 if (_handshake_timeout > 0) { 94 return os::elapsed_counter() >= (start_time + _handshake_timeout); 95 } 96 return false; 97 } 98 99 void VM_Handshake::handle_timeout() { 100 LogStreamHandle(Warning, handshake) log_stream; 101 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) { 102 if (thr->has_handshake()) { 103 log_stream.print("Thread " PTR_FORMAT " has not cleared its handshake op", p2i(thr)); 104 thr->print_thread_state_on(&log_stream); 105 } 106 } 107 log_stream.flush(); 108 fatal("Handshake operation timed out"); 109 } 110 111 class VM_HandshakeOneThread: public VM_Handshake { 112 JavaThread* _target; 113 public: 114 VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) : 115 VM_Handshake(op), _target(target) {} 116 117 void doit() { 118 DEBUG_ONLY(_op->check_state();) 119 TraceTime timer("Finished executing single-target operation (VM_HandshakeOneThread::doit)", TRACETIME_LOG(Info, handshake)); 120 121 ThreadsListHandle tlh; 122 if (tlh.includes(_target)) { 123 set_handshake(_target); 124 } else { 125 log_trace(handshake)("JavaThread " INTPTR_FORMAT " is not alive", p2i(_target)); 126 return; 127 } 128 129 log_trace(handshake)("JavaThread " INTPTR_FORMAT " signaled, begin attempt to process by VMThtread", p2i(_target)); 130 jlong start_time = os::elapsed_counter(); 131 do { 132 if (handshake_has_timed_out(start_time)) { 133 handle_timeout(); 134 } 135 136 // We need to re-think this with SMR ThreadsList. 137 // There is an assumption in the code that the Threads_lock should be 138 // locked during certain phases. 139 { 140 MutexLocker ml(Threads_lock); 141 _target->handshake_process_by_vmthread(); 142 } 143 } while (!poll_for_completed_thread()); 144 DEBUG_ONLY(_op->check_state();) 145 } 146 147 VMOp_Type type() const { return VMOp_HandshakeOneThread; } 148 149 bool executed() const { return _op->executed(); } 150 }; 151 152 class VM_HandshakeAllThreads: public VM_Handshake { 153 public: 154 VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {} 155 156 void doit() { 157 DEBUG_ONLY(_op->check_state();) 158 TraceTime timer("Finished executing multi-target operation (VM_HandshakeAllThreads::doit)", TRACETIME_LOG(Info, handshake)); 159 160 JavaThreadIteratorWithHandle jtiwh; 161 int number_of_threads_issued = 0; 162 for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) { 163 set_handshake(thr); 164 number_of_threads_issued++; 165 } 166 167 if (number_of_threads_issued < 1) { 168 log_debug(handshake)("No threads to handshake."); 169 return; 170 } 171 172 log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread"); 173 const jlong start_time = os::elapsed_counter(); 174 int number_of_threads_completed = 0; 175 do { 176 // Check if handshake operation has timed out 177 if (handshake_has_timed_out(start_time)) { 178 handle_timeout(); 179 } 180 181 // Have VM thread perform the handshake operation for blocked threads. 182 // Observing a blocked state may of course be transient but the processing is guarded 183 // by semaphores and we optimistically begin by working on the blocked threads 184 { 185 // We need to re-think this with SMR ThreadsList. 186 // There is an assumption in the code that the Threads_lock should 187 // be locked during certain phases. 188 jtiwh.rewind(); 189 MutexLocker ml(Threads_lock); 190 for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) { 191 // A new thread on the ThreadsList will not have an operation, 192 // hence it is skipped in handshake_process_by_vmthread. 193 thr->handshake_process_by_vmthread(); 194 } 195 } 196 197 while (poll_for_completed_thread()) { 198 // Includes canceled operations by exiting threads. 199 number_of_threads_completed++; 200 } 201 202 } while (number_of_threads_issued > number_of_threads_completed); 203 assert(number_of_threads_issued == number_of_threads_completed, "Must be the same"); 204 DEBUG_ONLY(_op->check_state();) 205 } 206 207 VMOp_Type type() const { return VMOp_HandshakeAllThreads; } 208 }; 209 210 class VM_HandshakeFallbackOperation : public VM_Operation { 211 HandshakeClosure* _handshake_cl; 212 Thread* _target_thread; 213 bool _all_threads; 214 bool _executed; 215 public: 216 VM_HandshakeFallbackOperation(HandshakeClosure* cl) : 217 _handshake_cl(cl), _target_thread(NULL), _all_threads(true), _executed(false) {} 218 VM_HandshakeFallbackOperation(HandshakeClosure* cl, Thread* target) : 219 _handshake_cl(cl), _target_thread(target), _all_threads(false), _executed(false) {} 220 221 void doit() { 222 log_trace(handshake)("VMThread executing VM_HandshakeFallbackOperation"); 223 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 224 if (_all_threads || t == _target_thread) { 225 if (t == _target_thread) { 226 _executed = true; 227 } 228 _handshake_cl->do_thread(t); 229 } 230 } 231 } 232 233 VMOp_Type type() const { return VMOp_HandshakeFallback; } 234 bool executed() const { return _executed; } 235 }; 236 237 void HandshakeThreadsOperation::do_handshake(JavaThread* thread) { 238 ResourceMark rm; 239 FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s", 240 p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread())); 241 TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task)); 242 243 // Only actually execute the operation for non terminated threads. 244 if (!thread->is_terminated()) { 245 _handshake_cl->do_thread(thread); 246 _executed = true; 247 } 248 249 // Use the semaphore to inform the VM thread that we have completed the operation 250 _done.signal(); 251 } 252 253 void Handshake::execute(HandshakeClosure* thread_cl) { 254 if (ThreadLocalHandshakes) { 255 HandshakeThreadsOperation cto(thread_cl); 256 VM_HandshakeAllThreads handshake(&cto); 257 VMThread::execute(&handshake); 258 } else { 259 VM_HandshakeFallbackOperation op(thread_cl); 260 VMThread::execute(&op); 261 } 262 } 263 264 bool Handshake::execute(HandshakeClosure* thread_cl, JavaThread* target) { 265 if (ThreadLocalHandshakes) { 266 HandshakeThreadsOperation cto(thread_cl); 267 VM_HandshakeOneThread handshake(&cto, target); 268 VMThread::execute(&handshake); 269 return handshake.executed(); 270 } else { 271 VM_HandshakeFallbackOperation op(thread_cl, target); 272 VMThread::execute(&op); 273 return op.executed(); 274 } 275 } 276 277 HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _thread_in_process_handshake(false) {} 278 279 void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) { 280 _operation = op; 281 SafepointMechanism::arm_local_poll_release(target); 282 } 283 284 void HandshakeState::clear_handshake(JavaThread* target) { 285 _operation = NULL; 286 SafepointMechanism::disarm_if_needed(target, true /* release */); 287 } 288 289 void HandshakeState::process_self_inner(JavaThread* thread) { 290 assert(Thread::current() == thread, "should call from thread"); 291 assert(!thread->is_terminated(), "should not be a terminated thread"); 292 assert(thread->thread_state() != _thread_blocked, "should not be in a blocked state"); 293 assert(thread->thread_state() != _thread_in_native, "should not be in native"); 294 295 do { 296 ThreadInVMForHandshake tivm(thread); 297 if (!_semaphore.trywait()) { 298 _semaphore.wait_with_safepoint_check(thread); 299 } 300 HandshakeOperation* op = Atomic::load_acquire(&_operation); 301 if (op != NULL) { 302 HandleMark hm(thread); 303 CautiouslyPreserveExceptionMark pem(thread); 304 // Disarm before execute the operation 305 clear_handshake(thread); 306 op->do_handshake(thread); 307 } 308 _semaphore.signal(); 309 } while (has_operation()); 310 } 311 312 bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) { 313 // handshake_safe may only be called with polls armed. 314 // VM thread controls this by first claiming the handshake via claim_handshake_for_vmthread. 315 return SafepointSynchronize::handshake_safe(target); 316 } 317 318 static bool possibly_vmthread_can_process_handshake(JavaThread* target) { 319 // An externally suspended thread cannot be resumed while the 320 // Threads_lock is held so it is safe. 321 // Note that this method is allowed to produce false positives. 322 assert(Threads_lock->owned_by_self(), "Not holding Threads_lock."); 323 if (target->is_ext_suspended()) { 324 return true; 325 } 326 if (target->is_terminated()) { 327 return true; 328 } 329 switch (target->thread_state()) { 330 case _thread_in_native: 331 // native threads are safe if they have no java stack or have walkable stack 332 return !target->has_last_Java_frame() || target->frame_anchor()->walkable(); 333 334 case _thread_blocked: 335 return true; 336 337 default: 338 return false; 339 } 340 } 341 342 bool HandshakeState::claim_handshake_for_vmthread() { 343 if (!_semaphore.trywait()) { 344 return false; 345 } 346 if (has_operation()) { 347 return true; 348 } 349 _semaphore.signal(); 350 return false; 351 } 352 353 void HandshakeState::process_by_vmthread(JavaThread* target) { 354 assert(Thread::current()->is_VM_thread(), "should call from vm thread"); 355 // Threads_lock must be held here, but that is assert()ed in 356 // possibly_vmthread_can_process_handshake(). 357 358 if (!has_operation()) { 359 // JT has already cleared its handshake 360 return; 361 } 362 363 if (!possibly_vmthread_can_process_handshake(target)) { 364 // JT is observed in an unsafe state, it must notice the handshake itself 365 return; 366 } 367 368 // Claim the semaphore if there still an operation to be executed. 369 if (!claim_handshake_for_vmthread()) { 370 return; 371 } 372 373 // If we own the semaphore at this point and while owning the semaphore 374 // can observe a safe state the thread cannot possibly continue without 375 // getting caught by the semaphore. 376 if (vmthread_can_process_handshake(target)) { 377 guarantee(!_semaphore.trywait(), "we should already own the semaphore"); 378 log_trace(handshake)("Processing handshake by VMThtread"); 379 _operation->do_handshake(target); 380 // Disarm after VM thread have executed the operation. 381 clear_handshake(target); 382 // Release the thread 383 } 384 385 _semaphore.signal(); 386 }