1 /*
2 * Copyright (c) 2018, 2022, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package java.lang;
26
27 import java.lang.ref.Reference;
28 import java.security.AccessController;
29 import java.security.PrivilegedAction;
30 import java.util.Locale;
31 import java.util.Objects;
32 import java.util.concurrent.CountDownLatch;
33 import java.util.concurrent.Executor;
34 import java.util.concurrent.Executors;
35 import java.util.concurrent.ForkJoinPool;
36 import java.util.concurrent.ForkJoinPool.ForkJoinWorkerThreadFactory;
37 import java.util.concurrent.ForkJoinTask;
38 import java.util.concurrent.ForkJoinWorkerThread;
39 import java.util.concurrent.Future;
40 import java.util.concurrent.RejectedExecutionException;
41 import java.util.concurrent.ScheduledExecutorService;
42 import java.util.concurrent.ScheduledThreadPoolExecutor;
43 import jdk.internal.event.ThreadSleepEvent;
44 import jdk.internal.event.VirtualThreadEndEvent;
45 import jdk.internal.event.VirtualThreadPinnedEvent;
46 import jdk.internal.event.VirtualThreadStartEvent;
47 import jdk.internal.event.VirtualThreadSubmitFailedEvent;
48 import jdk.internal.misc.CarrierThread;
49 import jdk.internal.misc.InnocuousThread;
50 import jdk.internal.misc.Unsafe;
51 import jdk.internal.vm.Continuation;
52 import jdk.internal.vm.ContinuationScope;
53 import jdk.internal.vm.StackableScope;
54 import jdk.internal.vm.ThreadContainer;
55 import jdk.internal.vm.ThreadContainers;
56 import jdk.internal.vm.annotation.ChangesCurrentThread;
57 import jdk.internal.vm.annotation.ForceInline;
58 import jdk.internal.vm.annotation.Hidden;
59 import jdk.internal.vm.annotation.JvmtiMountTransition;
60 import sun.nio.ch.Interruptible;
61 import sun.security.action.GetPropertyAction;
62 import static java.util.concurrent.TimeUnit.*;
63
64 /**
65 * A thread that is scheduled by the Java virtual machine rather than the operating
66 * system.
67 */
68 final class VirtualThread extends BaseVirtualThread {
69 private static final Unsafe U = Unsafe.getUnsafe();
70 private static final ContinuationScope VTHREAD_SCOPE = new ContinuationScope("VirtualThreads");
71 private static final ForkJoinPool DEFAULT_SCHEDULER = createDefaultScheduler();
72 private static final ScheduledExecutorService UNPARKER = createDelayedTaskScheduler();
73 private static final int TRACE_PINNING_MODE = tracePinningMode();
74
75 private static final long STATE = U.objectFieldOffset(VirtualThread.class, "state");
76 private static final long PARK_PERMIT = U.objectFieldOffset(VirtualThread.class, "parkPermit");
77 private static final long CARRIER_THREAD = U.objectFieldOffset(VirtualThread.class, "carrierThread");
78 private static final long TERMINATION = U.objectFieldOffset(VirtualThread.class, "termination");
79
80 // scheduler and continuation
81 private final Executor scheduler;
82 private final Continuation cont;
83 private final Runnable runContinuation;
84
85 // virtual thread state, accessed by VM
86 private volatile int state;
87
88 /*
89 * Virtual thread state and transitions:
90 *
91 * NEW -> STARTED // Thread.start
92 * STARTED -> TERMINATED // failed to start
93 * STARTED -> RUNNING // first run
94 *
95 * RUNNING -> PARKING // Thread attempts to park
96 * PARKING -> PARKED // cont.yield successful, thread is parked
97 * PARKING -> PINNED // cont.yield failed, thread is pinned
98 *
99 * PARKED -> RUNNABLE // unpark or interrupted
100 * PINNED -> RUNNABLE // unpark or interrupted
101 *
102 * RUNNABLE -> RUNNING // continue execution
103 *
104 * RUNNING -> YIELDING // Thread.yield
105 * YIELDING -> RUNNABLE // yield successful
106 * YIELDING -> RUNNING // yield failed
107 *
108 * RUNNING -> TERMINATED // done
109 */
110 private static final int NEW = 0;
111 private static final int STARTED = 1;
112 private static final int RUNNABLE = 2; // runnable-unmounted
113 private static final int RUNNING = 3; // runnable-mounted
114 private static final int PARKING = 4;
115 private static final int PARKED = 5; // unmounted
116 private static final int PINNED = 6; // mounted
117 private static final int YIELDING = 7; // Thread.yield
118 private static final int TERMINATED = 99; // final state
119
120 // can be suspended from scheduling when unmounted
121 private static final int SUSPENDED = 1 << 8;
122 private static final int RUNNABLE_SUSPENDED = (RUNNABLE | SUSPENDED);
123 private static final int PARKED_SUSPENDED = (PARKED | SUSPENDED);
124
125 // parking permit
126 private volatile boolean parkPermit;
127
128 // carrier thread when mounted, accessed by VM
129 private volatile Thread carrierThread;
130
131 // termination object when joining, created lazily if needed
132 private volatile CountDownLatch termination;
133
134 /**
135 * Returns the continuation scope used for virtual threads.
136 */
137 static ContinuationScope continuationScope() {
138 return VTHREAD_SCOPE;
139 }
140
141 /**
142 * Creates a new {@code VirtualThread} to run the given task with the given
143 * scheduler. If the given scheduler is {@code null} and the current thread
144 * is a platform thread then the newly created virtual thread will use the
145 * default scheduler. If given scheduler is {@code null} and the current
146 * thread is a virtual thread then the current thread's scheduler is used.
147 *
148 * @param scheduler the scheduler or null
149 * @param name thread name
150 * @param characteristics characteristics
151 * @param task the task to execute
152 */
153 VirtualThread(Executor scheduler, String name, int characteristics, Runnable task) {
154 super(name, characteristics, /*bound*/ false);
155 Objects.requireNonNull(task);
156
157 // choose scheduler if not specified
158 if (scheduler == null) {
159 Thread parent = Thread.currentThread();
160 if (parent instanceof VirtualThread vparent) {
161 scheduler = vparent.scheduler;
162 } else {
163 scheduler = DEFAULT_SCHEDULER;
164 }
165 }
166
167 this.scheduler = scheduler;
168 this.cont = new VThreadContinuation(this, task);
169 this.runContinuation = this::runContinuation;
170 }
171
172 /**
173 * The continuation that a virtual thread executes.
174 */
175 private static class VThreadContinuation extends Continuation {
176 VThreadContinuation(VirtualThread vthread, Runnable task) {
177 super(VTHREAD_SCOPE, () -> vthread.run(task));
178 }
179 @Override
180 protected void onPinned(Continuation.Pinned reason) {
181 if (TRACE_PINNING_MODE > 0) {
182 boolean printAll = (TRACE_PINNING_MODE == 1);
183 PinnedThreadPrinter.printStackTrace(System.out, printAll);
184 }
185 }
186 }
187
188 /**
189 * Runs or continues execution of the continuation on the current thread.
190 */
191 private void runContinuation() {
192 // the carrier must be a platform thread
193 if (Thread.currentThread().isVirtual()) {
194 throw new WrongThreadException();
195 }
196
197 // set state to RUNNING
198 boolean firstRun;
199 int initialState = state();
200 if (initialState == STARTED && compareAndSetState(STARTED, RUNNING)) {
201 // first run
202 firstRun = true;
203 } else if (initialState == RUNNABLE && compareAndSetState(RUNNABLE, RUNNING)) {
204 // consume parking permit
205 setParkPermit(false);
206 firstRun = false;
207 } else {
208 // not runnable
209 return;
210 }
211
212 // notify JVMTI before mount
213 if (notifyJvmtiEvents) notifyJvmtiMountBegin(firstRun);
214
215 try {
216 cont.run();
217 } finally {
218 if (cont.isDone()) {
219 afterTerminate(/*executed*/ true);
220 } else {
221 afterYield();
222 }
223 }
224 }
225
226 /**
227 * Submits the runContinuation task to the scheduler. For the default scheduler,
228 * and calling it on a worker thread, the task will be pushed to the local queue,
229 * otherwise it will be pushed to a submission queue.
230 *
231 * @throws RejectedExecutionException
232 */
233 private void submitRunContinuation() {
234 try {
235 scheduler.execute(runContinuation);
236 } catch (RejectedExecutionException ree) {
237 submitFailed(ree);
238 throw ree;
239 }
240 }
241
242 /**
243 * Submits the runContinuation task to the scheduler with a lazy submit.
244 * @throws RejectedExecutionException
245 * @see ForkJoinPool#lazySubmit(ForkJoinTask)
246 */
247 private void lazySubmitRunContinuation(ForkJoinPool pool) {
248 try {
249 pool.lazySubmit(ForkJoinTask.adapt(runContinuation));
250 } catch (RejectedExecutionException ree) {
251 submitFailed(ree);
252 throw ree;
253 }
254 }
255
256 /**
257 * Submits the runContinuation task to the scheduler as an external submit.
258 * @throws RejectedExecutionException
259 * @see ForkJoinPool#externalSubmit(ForkJoinTask)
260 */
261 private void externalSubmitRunContinuation(ForkJoinPool pool) {
262 try {
263 pool.externalSubmit(ForkJoinTask.adapt(runContinuation));
264 } catch (RejectedExecutionException ree) {
265 submitFailed(ree);
266 throw ree;
267 }
268 }
269
270 /**
271 * If enabled, emits a JFR VirtualThreadSubmitFailedEvent.
272 */
273 private void submitFailed(RejectedExecutionException ree) {
274 var event = new VirtualThreadSubmitFailedEvent();
275 if (event.isEnabled()) {
276 event.javaThreadId = threadId();
277 event.exceptionMessage = ree.getMessage();
278 event.commit();
279 }
280 }
281
282 /**
283 * Runs a task in the context of this virtual thread. The virtual thread is
284 * mounted on the current (carrier) thread before the task runs. It unmounts
285 * from its carrier thread when the task completes.
286 */
287 @ChangesCurrentThread
288 private void run(Runnable task) {
289 assert state == RUNNING;
290 boolean notifyJvmti = notifyJvmtiEvents;
291
292 // first mount
293 mount();
294 if (notifyJvmti) notifyJvmtiMountEnd(true);
295
296 // emit JFR event if enabled
297 if (VirtualThreadStartEvent.isTurnedOn()) {
298 var event = new VirtualThreadStartEvent();
299 event.javaThreadId = threadId();
300 event.commit();
301 }
302
303 Object bindings = scopedValueBindings();
304 try {
305 runWith(bindings, task);
306 } catch (Throwable exc) {
307 dispatchUncaughtException(exc);
308 } finally {
309 try {
310 // pop any remaining scopes from the stack, this may block
311 StackableScope.popAll();
312
313 // emit JFR event if enabled
314 if (VirtualThreadEndEvent.isTurnedOn()) {
315 var event = new VirtualThreadEndEvent();
316 event.javaThreadId = threadId();
317 event.commit();
318 }
319
320 } finally {
321 // last unmount
322 if (notifyJvmti) notifyJvmtiUnmountBegin(true);
323 unmount();
324
325 // final state
326 setState(TERMINATED);
327 }
328 }
329 }
330
331 @Hidden
332 @ForceInline
333 private void runWith(Object bindings, Runnable op) {
334 ensureMaterializedForStackWalk(bindings);
335 op.run();
336 Reference.reachabilityFence(bindings);
337 }
338
339 /**
340 * Mounts this virtual thread onto the current platform thread. On
341 * return, the current thread is the virtual thread.
342 */
343 @ChangesCurrentThread
344 private void mount() {
345 // sets the carrier thread
346 Thread carrier = Thread.currentCarrierThread();
347 setCarrierThread(carrier);
348
349 // sync up carrier thread interrupt status if needed
350 if (interrupted) {
351 carrier.setInterrupt();
352 } else if (carrier.isInterrupted()) {
353 synchronized (interruptLock) {
354 // need to recheck interrupt status
355 if (!interrupted) {
356 carrier.clearInterrupt();
357 }
358 }
359 }
360
361 // set Thread.currentThread() to return this virtual thread
362 carrier.setCurrentThread(this);
363 }
364
365 /**
366 * Unmounts this virtual thread from the carrier. On return, the
367 * current thread is the current platform thread.
368 */
369 @ChangesCurrentThread
370 private void unmount() {
371 // set Thread.currentThread() to return the platform thread
372 Thread carrier = this.carrierThread;
373 carrier.setCurrentThread(carrier);
374
375 // break connection to carrier thread, synchronized with interrupt
376 synchronized (interruptLock) {
377 setCarrierThread(null);
378 }
379 carrier.clearInterrupt();
380 }
381
382 /**
383 * Sets the current thread to the current carrier thread.
384 * @return true if JVMTI was notified
385 */
386 @ChangesCurrentThread
387 @JvmtiMountTransition
388 private boolean switchToCarrierThread() {
389 boolean notifyJvmti = notifyJvmtiEvents;
390 if (notifyJvmti) {
391 notifyJvmtiHideFrames(true);
392 }
393 Thread carrier = this.carrierThread;
394 assert Thread.currentThread() == this
395 && carrier == Thread.currentCarrierThread();
396 carrier.setCurrentThread(carrier);
397 return notifyJvmti;
398 }
399
400 /**
401 * Sets the current thread to the given virtual thread.
402 * If {@code notifyJvmti} is true then JVMTI is notified.
403 */
404 @ChangesCurrentThread
405 @JvmtiMountTransition
406 private void switchToVirtualThread(VirtualThread vthread, boolean notifyJvmti) {
407 Thread carrier = vthread.carrierThread;
408 assert carrier == Thread.currentCarrierThread();
409 carrier.setCurrentThread(vthread);
410 if (notifyJvmti) {
411 notifyJvmtiHideFrames(false);
412 }
413 }
414
415 /**
416 * Unmounts this virtual thread, invokes Continuation.yield, and re-mounts the
417 * thread when continued. When enabled, JVMTI must be notified from this method.
418 * @return true if the yield was successful
419 */
420 @ChangesCurrentThread
421 private boolean yieldContinuation() {
422 boolean notifyJvmti = notifyJvmtiEvents;
423
424 // unmount
425 if (notifyJvmti) notifyJvmtiUnmountBegin(false);
426 unmount();
427 try {
428 return Continuation.yield(VTHREAD_SCOPE);
429 } finally {
430 // re-mount
431 mount();
432 if (notifyJvmti) notifyJvmtiMountEnd(false);
433 }
434 }
435
436 /**
437 * Invoked after the continuation yields. If parking then it sets the state
438 * and also re-submits the task to continue if unparked while parking.
439 * If yielding due to Thread.yield then it just submits the task to continue.
440 */
441 private void afterYield() {
442 int s = state();
443 assert (s == PARKING || s == YIELDING) && (carrierThread == null);
444
445 if (s == PARKING) {
446 setState(PARKED);
447
448 // notify JVMTI that unmount has completed, thread is parked
449 if (notifyJvmtiEvents) notifyJvmtiUnmountEnd(false);
450
451 // may have been unparked while parking
452 if (parkPermit && compareAndSetState(PARKED, RUNNABLE)) {
453 // lazy submit to continue on the current thread as carrier if possible
454 if (currentThread() instanceof CarrierThread ct) {
455 lazySubmitRunContinuation(ct.getPool());
456 } else {
457 submitRunContinuation();
458 }
459
460 }
461 } else if (s == YIELDING) { // Thread.yield
462 setState(RUNNABLE);
463
464 // notify JVMTI that unmount has completed, thread is runnable
465 if (notifyJvmtiEvents) notifyJvmtiUnmountEnd(false);
466
467 // external submit if there are no tasks in the local task queue
468 if (currentThread() instanceof CarrierThread ct && ct.getQueuedTaskCount() == 0) {
469 externalSubmitRunContinuation(ct.getPool());
470 } else {
471 submitRunContinuation();
472 }
473 }
474 }
475
476 /**
477 * Invoked after the thread terminates (or start failed). This method
478 * notifies anyone waiting for the thread to terminate.
479 *
480 * @param executed true if the thread executed, false if it failed to start
481 */
482 private void afterTerminate(boolean executed) {
483 assert (state() == TERMINATED) && (carrierThread == null);
484
485 if (executed) {
486 if (notifyJvmtiEvents) notifyJvmtiUnmountEnd(true);
487 }
488
489 // notify anyone waiting for this virtual thread to terminate
490 CountDownLatch termination = this.termination;
491 if (termination != null) {
492 assert termination.getCount() == 1;
493 termination.countDown();
494 }
495
496 if (executed) {
497 // notify container if thread executed
498 threadContainer().onExit(this);
499
500 // clear references to thread locals
501 clearReferences();
502 }
503 }
504
505 /**
506 * Schedules this {@code VirtualThread} to execute.
507 *
508 * @throws IllegalStateException if the container is shutdown or closed
509 * @throws IllegalThreadStateException if the thread has already been started
510 * @throws RejectedExecutionException if the scheduler cannot accept a task
511 */
512 @Override
513 void start(ThreadContainer container) {
514 if (!compareAndSetState(NEW, STARTED)) {
515 throw new IllegalThreadStateException("Already started");
516 }
517
518 // bind thread to container
519 setThreadContainer(container);
520
521 // start thread
522 boolean started = false;
523 container.onStart(this); // may throw
524 try {
525 // scoped values may be inherited
526 inheritScopedValueBindings(container);
527
528 // submit task to run thread
529 submitRunContinuation();
530 started = true;
531 } finally {
532 if (!started) {
533 setState(TERMINATED);
534 container.onExit(this);
535 afterTerminate(/*executed*/ false);
536 }
537 }
538 }
539
540 @Override
541 public void start() {
542 start(ThreadContainers.root());
543 }
544
545 @Override
546 public void run() {
547 // do nothing
548 }
549
550 /**
551 * Parks until unparked or interrupted. If already unparked then the parking
552 * permit is consumed and this method completes immediately (meaning it doesn't
553 * yield). It also completes immediately if the interrupt status is set.
554 */
555 @Override
556 void park() {
557 assert Thread.currentThread() == this;
558
559 // complete immediately if parking permit available or interrupted
560 if (getAndSetParkPermit(false) || interrupted)
561 return;
562
563 // park the thread
564 setState(PARKING);
565 try {
566 if (!yieldContinuation()) {
567 // park on the carrier thread when pinned
568 parkOnCarrierThread(false, 0);
569 }
570 } finally {
571 assert (Thread.currentThread() == this) && (state() == RUNNING);
572 }
573 }
574
575 /**
576 * Parks up to the given waiting time or until unparked or interrupted.
577 * If already unparked then the parking permit is consumed and this method
578 * completes immediately (meaning it doesn't yield). It also completes immediately
579 * if the interrupt status is set or the waiting time is {@code <= 0}.
580 *
581 * @param nanos the maximum number of nanoseconds to wait.
582 */
583 @Override
584 void parkNanos(long nanos) {
585 assert Thread.currentThread() == this;
586
587 // complete immediately if parking permit available or interrupted
588 if (getAndSetParkPermit(false) || interrupted)
589 return;
590
591 // park the thread for the waiting time
592 if (nanos > 0) {
593 long startTime = System.nanoTime();
594
595 boolean yielded;
596 Future<?> unparker = scheduleUnpark(this::unpark, nanos);
597 setState(PARKING);
598 try {
599 yielded = yieldContinuation();
600 } finally {
601 assert (Thread.currentThread() == this)
602 && (state() == RUNNING || state() == PARKING);
603 cancel(unparker);
604 }
605
606 // park on carrier thread for remaining time when pinned
607 if (!yielded) {
608 long deadline = startTime + nanos;
609 if (deadline < 0L)
610 deadline = Long.MAX_VALUE;
611 parkOnCarrierThread(true, deadline - System.nanoTime());
612 }
613 }
614 }
615
616 /**
617 * Parks the current carrier thread up to the given waiting time or until
618 * unparked or interrupted. If the virtual thread is interrupted then the
619 * interrupt status will be propagated to the carrier thread.
620 * @param timed true for a timed park, false for untimed
621 * @param nanos the waiting time in nanoseconds
622 */
623 private void parkOnCarrierThread(boolean timed, long nanos) {
624 assert state() == PARKING;
625
626 var pinnedEvent = new VirtualThreadPinnedEvent();
627 pinnedEvent.begin();
628
629 setState(PINNED);
630 try {
631 if (!parkPermit) {
632 if (!timed) {
633 U.park(false, 0);
634 } else if (nanos > 0) {
635 U.park(false, nanos);
636 }
637 }
638 } finally {
639 setState(RUNNING);
640 }
641
642 // consume parking permit
643 setParkPermit(false);
644
645 pinnedEvent.commit();
646 }
647
648 /**
649 * Schedule an unpark task to run after a given delay.
650 */
651 @ChangesCurrentThread
652 private Future<?> scheduleUnpark(Runnable unparker, long nanos) {
653 // need to switch to current carrier thread to avoid nested parking
654 boolean notifyJvmti = switchToCarrierThread();
655 try {
656 return UNPARKER.schedule(unparker, nanos, NANOSECONDS);
657 } finally {
658 switchToVirtualThread(this, notifyJvmti);
659 }
660 }
661
662 /**
663 * Cancels a task if it has not completed.
664 */
665 @ChangesCurrentThread
666 private void cancel(Future<?> future) {
667 if (!future.isDone()) {
668 // need to switch to current carrier thread to avoid nested parking
669 boolean notifyJvmti = switchToCarrierThread();
670 try {
671 future.cancel(false);
672 } finally {
673 switchToVirtualThread(this, notifyJvmti);
674 }
675 }
676 }
677
678 /**
679 * Re-enables this virtual thread for scheduling. If the virtual thread was
680 * {@link #park() parked} then it will be unblocked, otherwise its next call
681 * to {@code park} or {@linkplain #parkNanos(long) parkNanos} is guaranteed
682 * not to block.
683 * @throws RejectedExecutionException if the scheduler cannot accept a task
684 */
685 @Override
686 @ChangesCurrentThread
687 void unpark() {
688 Thread currentThread = Thread.currentThread();
689 if (!getAndSetParkPermit(true) && currentThread != this) {
690 int s = state();
691 if (s == PARKED && compareAndSetState(PARKED, RUNNABLE)) {
692 if (currentThread instanceof VirtualThread vthread) {
693 boolean notifyJvmti = vthread.switchToCarrierThread();
694 try {
695 submitRunContinuation();
696 } finally {
697 switchToVirtualThread(vthread, notifyJvmti);
698 }
699 } else {
700 submitRunContinuation();
701 }
702 } else if (s == PINNED) {
703 // unpark carrier thread when pinned.
704 synchronized (carrierThreadAccessLock()) {
705 Thread carrier = carrierThread;
706 if (carrier != null && state() == PINNED) {
707 U.unpark(carrier);
708 }
709 }
710 }
711 }
712 }
713
714 /**
715 * Attempts to yield the current virtual thread (Thread.yield).
716 */
717 void tryYield() {
718 assert Thread.currentThread() == this;
719 setState(YIELDING);
720 try {
721 yieldContinuation();
722 } finally {
723 assert Thread.currentThread() == this;
724 if (state() != RUNNING) {
725 assert state() == YIELDING;
726 setState(RUNNING);
727 }
728 }
729 }
730
731 /**
732 * Sleep the current virtual thread for the given sleep time.
733 *
734 * @param nanos the maximum number of nanoseconds to sleep
735 * @throws InterruptedException if interrupted while sleeping
736 */
737 void sleepNanos(long nanos) throws InterruptedException {
738 assert Thread.currentThread() == this;
739 if (nanos >= 0) {
740 if (ThreadSleepEvent.isTurnedOn()) {
741 ThreadSleepEvent event = new ThreadSleepEvent();
742 try {
743 event.time = nanos;
744 event.begin();
745 doSleepNanos(nanos);
746 } finally {
747 event.commit();
748 }
749 } else {
750 doSleepNanos(nanos);
751 }
752 }
753 }
754
755 /**
756 * Sleep the current thread for the given sleep time (in nanoseconds). If
757 * nanos is 0 then the thread will attempt to yield.
758 *
759 * @implNote This implementation parks the thread for the given sleeping time
760 * and will therefore be observed in PARKED state during the sleep. Parking
761 * will consume the parking permit so this method makes available the parking
762 * permit after the sleep. This may be observed as a spurious, but benign,
763 * wakeup when the thread subsequently attempts to park.
764 */
765 private void doSleepNanos(long nanos) throws InterruptedException {
766 assert nanos >= 0;
767 if (getAndClearInterrupt())
768 throw new InterruptedException();
769 if (nanos == 0) {
770 tryYield();
771 } else {
772 // park for the sleep time
773 try {
774 long remainingNanos = nanos;
775 long startNanos = System.nanoTime();
776 while (remainingNanos > 0) {
777 parkNanos(remainingNanos);
778 if (getAndClearInterrupt()) {
779 throw new InterruptedException();
780 }
781 remainingNanos = nanos - (System.nanoTime() - startNanos);
782 }
783 } finally {
784 // may have been unparked while sleeping
785 setParkPermit(true);
786 }
787 }
788 }
789
790 /**
791 * Waits up to {@code nanos} nanoseconds for this virtual thread to terminate.
792 * A timeout of {@code 0} means to wait forever.
793 *
794 * @throws InterruptedException if interrupted while waiting
795 * @return true if the thread has terminated
796 */
797 boolean joinNanos(long nanos) throws InterruptedException {
798 if (state() == TERMINATED)
799 return true;
800
801 // ensure termination object exists, then re-check state
802 CountDownLatch termination = getTermination();
803 if (state() == TERMINATED)
804 return true;
805
806 // wait for virtual thread to terminate
807 if (nanos == 0) {
808 termination.await();
809 } else {
810 boolean terminated = termination.await(nanos, NANOSECONDS);
811 if (!terminated) {
812 // waiting time elapsed
813 return false;
814 }
815 }
816 assert state() == TERMINATED;
817 return true;
818 }
819
820 @Override
821 @SuppressWarnings("removal")
822 public void interrupt() {
823 if (Thread.currentThread() != this) {
824 checkAccess();
825 synchronized (interruptLock) {
826 interrupted = true;
827 Interruptible b = nioBlocker;
828 if (b != null) {
829 b.interrupt(this);
830 }
831
832 // interrupt carrier thread if mounted
833 Thread carrier = carrierThread;
834 if (carrier != null) carrier.setInterrupt();
835 }
836 } else {
837 interrupted = true;
838 carrierThread.setInterrupt();
839 }
840 unpark();
841 }
842
843 @Override
844 public boolean isInterrupted() {
845 return interrupted;
846 }
847
848 @Override
849 boolean getAndClearInterrupt() {
850 assert Thread.currentThread() == this;
851 synchronized (interruptLock) {
852 boolean oldValue = interrupted;
853 if (oldValue)
854 interrupted = false;
855 carrierThread.clearInterrupt();
856 return oldValue;
857 }
858 }
859
860 @Override
861 Thread.State threadState() {
862 switch (state()) {
863 case NEW:
864 return Thread.State.NEW;
865 case STARTED:
866 // return NEW if thread container not yet set
867 if (threadContainer() == null) {
868 return Thread.State.NEW;
869 } else {
870 return Thread.State.RUNNABLE;
871 }
872 case RUNNABLE:
873 case RUNNABLE_SUSPENDED:
874 // runnable, not mounted
875 return Thread.State.RUNNABLE;
876 case RUNNING:
877 // if mounted then return state of carrier thread
878 synchronized (carrierThreadAccessLock()) {
879 Thread carrierThread = this.carrierThread;
880 if (carrierThread != null) {
881 return carrierThread.threadState();
882 }
883 }
884 // runnable, mounted
885 return Thread.State.RUNNABLE;
886 case PARKING:
887 case YIELDING:
888 // runnable, mounted, not yet waiting
889 return Thread.State.RUNNABLE;
890 case PARKED:
891 case PARKED_SUSPENDED:
892 case PINNED:
893 return Thread.State.WAITING;
894 case TERMINATED:
895 return Thread.State.TERMINATED;
896 default:
897 throw new InternalError();
898 }
899 }
900
901 @Override
902 boolean alive() {
903 int s = state;
904 return (s != NEW && s != TERMINATED);
905 }
906
907 @Override
908 boolean isTerminated() {
909 return (state == TERMINATED);
910 }
911
912 @Override
913 StackTraceElement[] asyncGetStackTrace() {
914 StackTraceElement[] stackTrace;
915 do {
916 stackTrace = (carrierThread != null)
917 ? super.asyncGetStackTrace() // mounted
918 : tryGetStackTrace(); // unmounted
919 if (stackTrace == null) {
920 Thread.yield();
921 }
922 } while (stackTrace == null);
923 return stackTrace;
924 }
925
926 /**
927 * Returns the stack trace for this virtual thread if it is unmounted.
928 * Returns null if the thread is in another state.
929 */
930 private StackTraceElement[] tryGetStackTrace() {
931 int initialState = state();
932 return switch (initialState) {
933 case RUNNABLE, PARKED -> {
934 int suspendedState = initialState | SUSPENDED;
935 if (compareAndSetState(initialState, suspendedState)) {
936 try {
937 yield cont.getStackTrace();
938 } finally {
939 assert state == suspendedState;
940 setState(initialState);
941
942 // re-submit if runnable
943 // re-submit if unparked while suspended
944 if (initialState == RUNNABLE
945 || (parkPermit && compareAndSetState(PARKED, RUNNABLE))) {
946 try {
947 submitRunContinuation();
948 } catch (RejectedExecutionException ignore) { }
949 }
950 }
951 }
952 yield null;
953 }
954 case NEW, STARTED, TERMINATED -> new StackTraceElement[0]; // empty stack
955 default -> null;
956 };
957 }
958
959 @Override
960 public String toString() {
961 StringBuilder sb = new StringBuilder("VirtualThread[#");
962 sb.append(threadId());
963 String name = getName();
964 if (!name.isEmpty()) {
965 sb.append(",");
966 sb.append(name);
967 }
968 sb.append("]/");
969 Thread carrier = carrierThread;
970 if (carrier != null) {
971 // include the carrier thread state and name when mounted
972 synchronized (carrierThreadAccessLock()) {
973 carrier = carrierThread;
974 if (carrier != null) {
975 String stateAsString = carrier.threadState().toString();
976 sb.append(stateAsString.toLowerCase(Locale.ROOT));
977 sb.append('@');
978 sb.append(carrier.getName());
979 }
980 }
981 }
982 // include virtual thread state when not mounted
983 if (carrier == null) {
984 String stateAsString = threadState().toString();
985 sb.append(stateAsString.toLowerCase(Locale.ROOT));
986 }
987 return sb.toString();
988 }
989
990 @Override
991 public int hashCode() {
992 return (int) threadId();
993 }
994
995 @Override
996 public boolean equals(Object obj) {
997 return obj == this;
998 }
999
1000 /**
1001 * Returns the termination object, creating it if needed.
1002 */
1003 private CountDownLatch getTermination() {
1004 CountDownLatch termination = this.termination;
1005 if (termination == null) {
1006 termination = new CountDownLatch(1);
1007 if (!U.compareAndSetReference(this, TERMINATION, null, termination)) {
1008 termination = this.termination;
1009 }
1010 }
1011 return termination;
1012 }
1013
1014 /**
1015 * Returns the lock object to synchronize on when accessing carrierThread.
1016 * The lock prevents carrierThread from being reset to null during unmount.
1017 */
1018 private Object carrierThreadAccessLock() {
1019 // return interruptLock as unmount has to coordinate with interrupt
1020 return interruptLock;
1021 }
1022
1023 // -- wrappers for get/set of state, parking permit, and carrier thread --
1024
1025 private int state() {
1026 return state; // volatile read
1027 }
1028
1029 private void setState(int newValue) {
1030 state = newValue; // volatile write
1031 }
1032
1033 private boolean compareAndSetState(int expectedValue, int newValue) {
1034 return U.compareAndSetInt(this, STATE, expectedValue, newValue);
1035 }
1036
1037 private void setParkPermit(boolean newValue) {
1038 if (parkPermit != newValue) {
1039 parkPermit = newValue;
1040 }
1041 }
1042
1043 private boolean getAndSetParkPermit(boolean newValue) {
1044 if (parkPermit != newValue) {
1045 return U.getAndSetBoolean(this, PARK_PERMIT, newValue);
1046 } else {
1047 return newValue;
1048 }
1049 }
1050
1051 private void setCarrierThread(Thread carrier) {
1052 // U.putReferenceRelease(this, CARRIER_THREAD, carrier);
1053 this.carrierThread = carrier;
1054 }
1055
1056 // -- JVM TI support --
1057
1058 private static volatile boolean notifyJvmtiEvents; // set by VM
1059
1060 @JvmtiMountTransition
1061 private native void notifyJvmtiMountBegin(boolean firstMount);
1062
1063 @JvmtiMountTransition
1064 private native void notifyJvmtiMountEnd(boolean firstMount);
1065
1066 @JvmtiMountTransition
1067 private native void notifyJvmtiUnmountBegin(boolean lastUnmount);
1068
1069 @JvmtiMountTransition
1070 private native void notifyJvmtiUnmountEnd(boolean lastUnmount);
1071
1072 @JvmtiMountTransition
1073 private native void notifyJvmtiHideFrames(boolean hide);
1074
1075 private static native void registerNatives();
1076 static {
1077 registerNatives();
1078 }
1079
1080 /**
1081 * Creates the default scheduler.
1082 */
1083 @SuppressWarnings("removal")
1084 private static ForkJoinPool createDefaultScheduler() {
1085 ForkJoinWorkerThreadFactory factory = pool -> {
1086 PrivilegedAction<ForkJoinWorkerThread> pa = () -> new CarrierThread(pool);
1087 return AccessController.doPrivileged(pa);
1088 };
1089 PrivilegedAction<ForkJoinPool> pa = () -> {
1090 int parallelism, maxPoolSize, minRunnable;
1091 String parallelismValue = System.getProperty("jdk.virtualThreadScheduler.parallelism");
1092 String maxPoolSizeValue = System.getProperty("jdk.virtualThreadScheduler.maxPoolSize");
1093 String minRunnableValue = System.getProperty("jdk.virtualThreadScheduler.minRunnable");
1094 if (parallelismValue != null) {
1095 parallelism = Integer.parseInt(parallelismValue);
1096 } else {
1097 parallelism = Runtime.getRuntime().availableProcessors();
1098 }
1099 if (maxPoolSizeValue != null) {
1100 maxPoolSize = Integer.parseInt(maxPoolSizeValue);
1101 parallelism = Integer.min(parallelism, maxPoolSize);
1102 } else {
1103 maxPoolSize = Integer.max(parallelism, 256);
1104 }
1105 if (minRunnableValue != null) {
1106 minRunnable = Integer.parseInt(minRunnableValue);
1107 } else {
1108 minRunnable = Integer.max(parallelism / 2, 1);
1109 }
1110 Thread.UncaughtExceptionHandler handler = (t, e) -> { };
1111 boolean asyncMode = true; // FIFO
1112 return new ForkJoinPool(parallelism, factory, handler, asyncMode,
1113 0, maxPoolSize, minRunnable, pool -> true, 30, SECONDS);
1114 };
1115 return AccessController.doPrivileged(pa);
1116 }
1117
1118 /**
1119 * Creates the ScheduledThreadPoolExecutor used for timed unpark.
1120 */
1121 private static ScheduledExecutorService createDelayedTaskScheduler() {
1122 String propValue = GetPropertyAction.privilegedGetProperty("jdk.unparker.maxPoolSize");
1123 int poolSize;
1124 if (propValue != null) {
1125 poolSize = Integer.parseInt(propValue);
1126 } else {
1127 poolSize = 1;
1128 }
1129 ScheduledThreadPoolExecutor stpe = (ScheduledThreadPoolExecutor)
1130 Executors.newScheduledThreadPool(poolSize, task -> {
1131 return InnocuousThread.newThread("VirtualThread-unparker", task);
1132 });
1133 stpe.setRemoveOnCancelPolicy(true);
1134 return stpe;
1135 }
1136
1137 /**
1138 * Reads the value of the jdk.tracePinnedThreads property to determine if stack
1139 * traces should be printed when a carrier thread is pinned when a virtual thread
1140 * attempts to park.
1141 */
1142 private static int tracePinningMode() {
1143 String propValue = GetPropertyAction.privilegedGetProperty("jdk.tracePinnedThreads");
1144 if (propValue != null) {
1145 if (propValue.length() == 0 || "full".equalsIgnoreCase(propValue))
1146 return 1;
1147 if ("short".equalsIgnoreCase(propValue))
1148 return 2;
1149 }
1150 return 0;
1151 }
1152 }
--- EOF ---