1 /* 2 * Copyright (c) 2017, 2020, 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/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 }; 44 45 class HandshakeThreadsOperation: public HandshakeOperation { 46 static Semaphore _done; 47 HandshakeClosure* _handshake_cl; 48 bool _executed; 49 public: 50 HandshakeThreadsOperation(HandshakeClosure* cl) : _handshake_cl(cl), _executed(false) {} 51 void do_handshake(JavaThread* thread); 52 bool thread_has_completed() { return _done.trywait(); } 53 bool executed() const { return _executed; } 54 const char* name() { return _handshake_cl->name(); } 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 protected: 71 HandshakeThreadsOperation* const _op; 72 73 VM_Handshake(HandshakeThreadsOperation* op) : 74 _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)), _op(op) {} 75 76 void set_handshake(JavaThread* target) { 77 target->set_handshake_operation(_op); 78 } 79 80 // This method returns true for threads completed their operation 81 // and true for threads canceled their operation. 82 // A cancellation can happen if the thread is exiting. 83 bool poll_for_completed_thread() { return _op->thread_has_completed(); } 84 85 bool handshake_has_timed_out(jlong start_time); 86 static void handle_timeout(); 87 }; 88 89 bool VM_Handshake::handshake_has_timed_out(jlong start_time) { 90 // Check if handshake operation has timed out 91 if (_handshake_timeout > 0) { 92 return os::elapsed_counter() >= (start_time + _handshake_timeout); 93 } 94 return false; 95 } 96 97 void VM_Handshake::handle_timeout() { 98 LogStreamHandle(Warning, handshake) log_stream; 99 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thr = jtiwh.next(); ) { 100 if (thr->has_handshake()) { 101 log_stream.print("Thread " PTR_FORMAT " has not cleared its handshake op", p2i(thr)); 102 thr->print_thread_state_on(&log_stream); 103 } 104 } 105 log_stream.flush(); 106 fatal("Handshake operation timed out"); 107 } 108 109 static void log_handshake_info(jlong start_time_ns, const char* name, int targets, int vmt_executed, const char* extra = NULL) { 110 if (start_time_ns != 0) { 111 jlong completion_time = os::javaTimeNanos() - start_time_ns; 112 log_info(handshake)("Handshake \"%s\", Targeted threads: %d, Executed by targeted threads: %d, Total completion time: " JLONG_FORMAT " ns%s%s", 113 name, targets, 114 targets - vmt_executed, 115 completion_time, 116 extra != NULL ? ", " : "", 117 extra != NULL ? extra : ""); 118 } 119 } 120 121 class VM_HandshakeOneThread: public VM_Handshake { 122 JavaThread* _target; 123 public: 124 VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) : 125 VM_Handshake(op), _target(target) {} 126 127 void doit() { 128 DEBUG_ONLY(_op->check_state();) 129 130 jlong start_time_ns = 0; 131 if (log_is_enabled(Info, handshake)) { 132 start_time_ns = os::javaTimeNanos(); 133 } 134 135 ThreadsListHandle tlh; 136 if (tlh.includes(_target)) { 137 set_handshake(_target); 138 } else { 139 log_handshake_info(start_time_ns, _op->name(), 0, 0, "(thread dead)"); 140 return; 141 } 142 143 log_trace(handshake)("JavaThread " INTPTR_FORMAT " signaled, begin attempt to process by VMThtread", p2i(_target)); 144 jlong timeout_start_time = os::elapsed_counter(); 145 bool by_vm_thread = false; 146 do { 147 if (handshake_has_timed_out(timeout_start_time)) { 148 handle_timeout(); 149 } 150 by_vm_thread = _target->handshake_try_process_by_vmThread(); 151 } while (!poll_for_completed_thread()); 152 DEBUG_ONLY(_op->check_state();) 153 log_handshake_info(start_time_ns, _op->name(), 1, by_vm_thread ? 1 : 0); 154 } 155 156 VMOp_Type type() const { return VMOp_HandshakeOneThread; } 157 158 bool executed() const { return _op->executed(); } 159 }; 160 161 class VM_HandshakeAllThreads: public VM_Handshake { 162 public: 163 VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {} 164 165 void doit() { 166 DEBUG_ONLY(_op->check_state();) 167 168 jlong start_time_ns = 0; 169 if (log_is_enabled(Info, handshake)) { 170 start_time_ns = os::javaTimeNanos(); 171 } 172 int handshake_executed_by_vm_thread = 0; 173 174 JavaThreadIteratorWithHandle jtiwh; 175 int number_of_threads_issued = 0; 176 for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) { 177 set_handshake(thr); 178 number_of_threads_issued++; 179 } 180 181 if (number_of_threads_issued < 1) { 182 log_handshake_info(start_time_ns, _op->name(), 0, 0); 183 return; 184 } 185 186 log_trace(handshake)("Threads signaled, begin processing blocked threads by VMThread"); 187 const jlong start_time = os::elapsed_counter(); 188 int number_of_threads_completed = 0; 189 do { 190 // Check if handshake operation has timed out 191 if (handshake_has_timed_out(start_time)) { 192 handle_timeout(); 193 } 194 195 // Have VM thread perform the handshake operation for blocked threads. 196 // Observing a blocked state may of course be transient but the processing is guarded 197 // by semaphores and we optimistically begin by working on the blocked threads 198 jtiwh.rewind(); 199 for (JavaThread *thr = jtiwh.next(); thr != NULL; thr = jtiwh.next()) { 200 // A new thread on the ThreadsList will not have an operation, 201 // hence it is skipped in handshake_process_by_vmthread. 202 if (thr->handshake_try_process_by_vmThread()) { 203 handshake_executed_by_vm_thread++; 204 } 205 } 206 while (poll_for_completed_thread()) { 207 // Includes canceled operations by exiting threads. 208 number_of_threads_completed++; 209 } 210 211 } while (number_of_threads_issued > number_of_threads_completed); 212 assert(number_of_threads_issued == number_of_threads_completed, "Must be the same"); 213 DEBUG_ONLY(_op->check_state();) 214 215 log_handshake_info(start_time_ns, _op->name(), number_of_threads_issued, handshake_executed_by_vm_thread); 216 } 217 218 VMOp_Type type() const { return VMOp_HandshakeAllThreads; } 219 }; 220 221 void HandshakeThreadsOperation::do_handshake(JavaThread* thread) { 222 jlong start_time_ns = 0; 223 if (log_is_enabled(Debug, handshake, task)) { 224 start_time_ns = os::javaTimeNanos(); 225 } 226 227 // Only actually execute the operation for non terminated threads. 228 if (!thread->is_terminated()) { 229 _handshake_cl->do_thread(thread); 230 _executed = true; 231 } 232 233 if (start_time_ns != 0) { 234 jlong completion_time = os::javaTimeNanos() - start_time_ns; 235 log_debug(handshake, task)("Operation: %s for thread " PTR_FORMAT ", is_vm_thread: %s, completed in " JLONG_FORMAT " ns", 236 name(), p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread()), completion_time); 237 } 238 239 // Use the semaphore to inform the VM thread that we have completed the operation 240 _done.signal(); 241 242 // It is no longer safe to refer to 'this' as the VMThread may have destroyed this operation 243 } 244 245 void Handshake::execute(HandshakeClosure* thread_cl) { 246 HandshakeThreadsOperation cto(thread_cl); 247 VM_HandshakeAllThreads handshake(&cto); 248 VMThread::execute(&handshake); 249 } 250 251 bool Handshake::execute(HandshakeClosure* thread_cl, JavaThread* target) { 252 HandshakeThreadsOperation cto(thread_cl); 253 VM_HandshakeOneThread handshake(&cto, target); 254 VMThread::execute(&handshake); 255 return handshake.executed(); 256 } 257 258 HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _thread_in_process_handshake(false) { 259 DEBUG_ONLY(_vmthread_processing_handshake = false;) 260 } 261 262 void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) { 263 _operation = op; 264 SafepointMechanism::arm_local_poll_release(target); 265 } 266 267 void HandshakeState::clear_handshake(JavaThread* target) { 268 _operation = NULL; 269 SafepointMechanism::disarm_if_needed(target, true /* release */); 270 } 271 272 void HandshakeState::process_self_inner(JavaThread* thread) { 273 assert(Thread::current() == thread, "should call from thread"); 274 assert(!thread->is_terminated(), "should not be a terminated thread"); 275 assert(thread->thread_state() != _thread_blocked, "should not be in a blocked state"); 276 assert(thread->thread_state() != _thread_in_native, "should not be in native"); 277 278 do { 279 ThreadInVMForHandshake tivm(thread); 280 if (!_semaphore.trywait()) { 281 _semaphore.wait_with_safepoint_check(thread); 282 } 283 HandshakeOperation* op = Atomic::load_acquire(&_operation); 284 if (op != NULL) { 285 HandleMark hm(thread); 286 CautiouslyPreserveExceptionMark pem(thread); 287 // Disarm before execute the operation 288 clear_handshake(thread); 289 op->do_handshake(thread); 290 } 291 _semaphore.signal(); 292 } while (has_operation()); 293 } 294 295 bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) { 296 // handshake_safe may only be called with polls armed. 297 // VM thread controls this by first claiming the handshake via claim_handshake_for_vmthread. 298 return SafepointSynchronize::handshake_safe(target); 299 } 300 301 static bool possibly_vmthread_can_process_handshake(JavaThread* target) { 302 // Note that this method is allowed to produce false positives. 303 if (target->is_ext_suspended()) { 304 return true; 305 } 306 if (target->is_terminated()) { 307 return true; 308 } 309 switch (target->thread_state()) { 310 case _thread_in_native: 311 // native threads are safe if they have no java stack or have walkable stack 312 return !target->has_last_Java_frame() || target->frame_anchor()->walkable(); 313 314 case _thread_blocked: 315 return true; 316 317 default: 318 return false; 319 } 320 } 321 322 bool HandshakeState::claim_handshake_for_vmthread() { 323 if (!_semaphore.trywait()) { 324 return false; 325 } 326 if (has_operation()) { 327 return true; 328 } 329 _semaphore.signal(); 330 return false; 331 } 332 333 bool HandshakeState::try_process_by_vmThread(JavaThread* target) { 334 assert(Thread::current()->is_VM_thread(), "should call from vm thread"); 335 336 if (!has_operation()) { 337 // JT has already cleared its handshake 338 return false; 339 } 340 341 if (!possibly_vmthread_can_process_handshake(target)) { 342 // JT is observed in an unsafe state, it must notice the handshake itself 343 return false; 344 } 345 346 // Claim the semaphore if there still an operation to be executed. 347 if (!claim_handshake_for_vmthread()) { 348 return false; 349 } 350 351 // If we own the semaphore at this point and while owning the semaphore 352 // can observe a safe state the thread cannot possibly continue without 353 // getting caught by the semaphore. 354 bool executed = false; 355 if (vmthread_can_process_handshake(target)) { 356 guarantee(!_semaphore.trywait(), "we should already own the semaphore"); 357 log_trace(handshake)("Processing handshake by VMThtread"); 358 DEBUG_ONLY(_vmthread_processing_handshake = true;) 359 _operation->do_handshake(target); 360 DEBUG_ONLY(_vmthread_processing_handshake = false;) 361 // Disarm after VM thread have executed the operation. 362 clear_handshake(target); 363 executed = true; 364 } 365 366 // Release the thread 367 _semaphore.signal(); 368 369 return executed; 370 }