/* * Copyright (c) 1998, 2025, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "classfile/vmSymbols.hpp" #include "gc/shared/collectedHeap.hpp" #include "jfr/jfrEvents.hpp" #include "logging/log.hpp" #include "logging/logStream.hpp" #include "memory/allocation.inline.hpp" #include "memory/padded.hpp" #include "memory/resourceArea.hpp" #include "memory/universe.hpp" #include "oops/markWord.hpp" #include "oops/oop.inline.hpp" #include "runtime/atomic.hpp" #include "runtime/basicLock.inline.hpp" #include "runtime/frame.inline.hpp" #include "runtime/globals.hpp" #include "runtime/handles.inline.hpp" #include "runtime/handshake.hpp" #include "runtime/interfaceSupport.inline.hpp" #include "runtime/javaThread.hpp" #include "runtime/lightweightSynchronizer.hpp" #include "runtime/lockStack.inline.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/objectMonitor.hpp" #include "runtime/objectMonitor.inline.hpp" #include "runtime/os.inline.hpp" #include "runtime/osThread.hpp" #include "runtime/safepointMechanism.inline.hpp" #include "runtime/safepointVerifiers.hpp" #include "runtime/sharedRuntime.hpp" #include "runtime/stubRoutines.hpp" #include "runtime/synchronizer.inline.hpp" #include "runtime/threads.hpp" #include "runtime/timer.hpp" #include "runtime/trimNativeHeap.hpp" #include "runtime/vframe.hpp" #include "runtime/vmThread.hpp" #include "utilities/align.hpp" #include "utilities/dtrace.hpp" #include "utilities/events.hpp" #include "utilities/globalCounter.inline.hpp" #include "utilities/globalDefinitions.hpp" #include "utilities/linkedlist.hpp" #include "utilities/preserveException.hpp" class ObjectMonitorDeflationLogging; void MonitorList::add(ObjectMonitor* m) { ObjectMonitor* head; do { head = Atomic::load(&_head); m->set_next_om(head); } while (Atomic::cmpxchg(&_head, head, m) != head); size_t count = Atomic::add(&_count, 1u, memory_order_relaxed); size_t old_max; do { old_max = Atomic::load(&_max); if (count <= old_max) { break; } } while (Atomic::cmpxchg(&_max, old_max, count, memory_order_relaxed) != old_max); } size_t MonitorList::count() const { return Atomic::load(&_count); } size_t MonitorList::max() const { return Atomic::load(&_max); } class ObjectMonitorDeflationSafepointer : public StackObj { JavaThread* const _current; ObjectMonitorDeflationLogging* const _log; public: ObjectMonitorDeflationSafepointer(JavaThread* current, ObjectMonitorDeflationLogging* log) : _current(current), _log(log) {} void block_for_safepoint(const char* op_name, const char* count_name, size_t counter); }; // Walk the in-use list and unlink deflated ObjectMonitors. // Returns the number of unlinked ObjectMonitors. size_t MonitorList::unlink_deflated(size_t deflated_count, GrowableArray* unlinked_list, ObjectMonitorDeflationSafepointer* safepointer) { size_t unlinked_count = 0; ObjectMonitor* prev = nullptr; ObjectMonitor* m = Atomic::load_acquire(&_head); while (m != nullptr) { if (m->is_being_async_deflated()) { // Find next live ObjectMonitor. Batch up the unlinkable monitors, so we can // modify the list once per batch. The batch starts at "m". size_t unlinked_batch = 0; ObjectMonitor* next = m; // Look for at most MonitorUnlinkBatch monitors, or the number of // deflated and not unlinked monitors, whatever comes first. assert(deflated_count >= unlinked_count, "Sanity: underflow"); size_t unlinked_batch_limit = MIN2(deflated_count - unlinked_count, MonitorUnlinkBatch); do { ObjectMonitor* next_next = next->next_om(); unlinked_batch++; unlinked_list->append(next); next = next_next; if (unlinked_batch >= unlinked_batch_limit) { // Reached the max batch, so bail out of the gathering loop. break; } if (prev == nullptr && Atomic::load(&_head) != m) { // Current batch used to be at head, but it is not at head anymore. // Bail out and figure out where we currently are. This avoids long // walks searching for new prev during unlink under heavy list inserts. break; } } while (next != nullptr && next->is_being_async_deflated()); // Unlink the found batch. if (prev == nullptr) { // The current batch is the first batch, so there is a chance that it starts at head. // Optimistically assume no inserts happened, and try to unlink the entire batch from the head. ObjectMonitor* prev_head = Atomic::cmpxchg(&_head, m, next); if (prev_head != m) { // Something must have updated the head. Figure out the actual prev for this batch. for (ObjectMonitor* n = prev_head; n != m; n = n->next_om()) { prev = n; } assert(prev != nullptr, "Should have found the prev for the current batch"); prev->set_next_om(next); } } else { // The current batch is preceded by another batch. This guarantees the current batch // does not start at head. Unlink the entire current batch without updating the head. assert(Atomic::load(&_head) != m, "Sanity"); prev->set_next_om(next); } unlinked_count += unlinked_batch; if (unlinked_count >= deflated_count) { // Reached the max so bail out of the searching loop. // There should be no more deflated monitors left. break; } m = next; } else { prev = m; m = m->next_om(); } // Must check for a safepoint/handshake and honor it. safepointer->block_for_safepoint("unlinking", "unlinked_count", unlinked_count); } #ifdef ASSERT // Invariant: the code above should unlink all deflated monitors. // The code that runs after this unlinking does not expect deflated monitors. // Notably, attempting to deflate the already deflated monitor would break. { ObjectMonitor* m = Atomic::load_acquire(&_head); while (m != nullptr) { assert(!m->is_being_async_deflated(), "All deflated monitors should be unlinked"); m = m->next_om(); } } #endif Atomic::sub(&_count, unlinked_count); return unlinked_count; } MonitorList::Iterator MonitorList::iterator() const { return Iterator(Atomic::load_acquire(&_head)); } ObjectMonitor* MonitorList::Iterator::next() { ObjectMonitor* current = _current; _current = current->next_om(); return current; } // The "core" versions of monitor enter and exit reside in this file. // The interpreter and compilers contain specialized transliterated // variants of the enter-exit fast-path operations. See c2_MacroAssembler_x86.cpp // fast_lock(...) for instance. If you make changes here, make sure to modify the // interpreter, and both C1 and C2 fast-path inline locking code emission. // // ----------------------------------------------------------------------------- #ifdef DTRACE_ENABLED // Only bother with this argument setup if dtrace is available // TODO-FIXME: probes should not fire when caller is _blocked. assert() accordingly. #define DTRACE_MONITOR_PROBE_COMMON(obj, thread) \ char* bytes = nullptr; \ int len = 0; \ jlong jtid = SharedRuntime::get_java_tid(thread); \ Symbol* klassname = obj->klass()->name(); \ if (klassname != nullptr) { \ bytes = (char*)klassname->bytes(); \ len = klassname->utf8_length(); \ } #define DTRACE_MONITOR_WAIT_PROBE(monitor, obj, thread, millis) \ { \ if (DTraceMonitorProbes) { \ DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ HOTSPOT_MONITOR_WAIT(jtid, \ (uintptr_t)(monitor), bytes, len, (millis)); \ } \ } #define HOTSPOT_MONITOR_PROBE_notify HOTSPOT_MONITOR_NOTIFY #define HOTSPOT_MONITOR_PROBE_notifyAll HOTSPOT_MONITOR_NOTIFYALL #define HOTSPOT_MONITOR_PROBE_waited HOTSPOT_MONITOR_WAITED #define DTRACE_MONITOR_PROBE(probe, monitor, obj, thread) \ { \ if (DTraceMonitorProbes) { \ DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ HOTSPOT_MONITOR_PROBE_##probe(jtid, /* probe = waited */ \ (uintptr_t)(monitor), bytes, len); \ } \ } #else // ndef DTRACE_ENABLED #define DTRACE_MONITOR_WAIT_PROBE(obj, thread, millis, mon) {;} #define DTRACE_MONITOR_PROBE(probe, obj, thread, mon) {;} #endif // ndef DTRACE_ENABLED // This exists only as a workaround of dtrace bug 6254741 static int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, JavaThread* thr) { DTRACE_MONITOR_PROBE(waited, monitor, obj(), thr); return 0; } static constexpr size_t inflation_lock_count() { return 256; } // Static storage for an array of PlatformMutex. alignas(PlatformMutex) static uint8_t _inflation_locks[inflation_lock_count()][sizeof(PlatformMutex)]; static inline PlatformMutex* inflation_lock(size_t index) { return reinterpret_cast(_inflation_locks[index]); } void ObjectSynchronizer::initialize() { for (size_t i = 0; i < inflation_lock_count(); i++) { ::new(static_cast(inflation_lock(i))) PlatformMutex(); } // Start the ceiling with the estimate for one thread. set_in_use_list_ceiling(AvgMonitorsPerThreadEstimate); // Start the timer for deflations, so it does not trigger immediately. _last_async_deflation_time_ns = os::javaTimeNanos(); if (LockingMode == LM_LIGHTWEIGHT) { LightweightSynchronizer::initialize(); } } MonitorList ObjectSynchronizer::_in_use_list; // monitors_used_above_threshold() policy is as follows: // // The ratio of the current _in_use_list count to the ceiling is used // to determine if we are above MonitorUsedDeflationThreshold and need // to do an async monitor deflation cycle. The ceiling is increased by // AvgMonitorsPerThreadEstimate when a thread is added to the system // and is decreased by AvgMonitorsPerThreadEstimate when a thread is // removed from the system. // // Note: If the _in_use_list max exceeds the ceiling, then // monitors_used_above_threshold() will use the in_use_list max instead // of the thread count derived ceiling because we have used more // ObjectMonitors than the estimated average. // // Note: If deflate_idle_monitors() has NoAsyncDeflationProgressMax // no-progress async monitor deflation cycles in a row, then the ceiling // is adjusted upwards by monitors_used_above_threshold(). // // Start the ceiling with the estimate for one thread in initialize() // which is called after cmd line options are processed. static size_t _in_use_list_ceiling = 0; bool volatile ObjectSynchronizer::_is_async_deflation_requested = false; bool volatile ObjectSynchronizer::_is_final_audit = false; jlong ObjectSynchronizer::_last_async_deflation_time_ns = 0; static uintx _no_progress_cnt = 0; static bool _no_progress_skip_increment = false; // =====================> Quick functions // The quick_* forms are special fast-path variants used to improve // performance. In the simplest case, a "quick_*" implementation could // simply return false, in which case the caller will perform the necessary // state transitions and call the slow-path form. // The fast-path is designed to handle frequently arising cases in an efficient // manner and is just a degenerate "optimistic" variant of the slow-path. // returns true -- to indicate the call was satisfied. // returns false -- to indicate the call needs the services of the slow-path. // A no-loitering ordinance is in effect for code in the quick_* family // operators: safepoints or indefinite blocking (blocking that might span a // safepoint) are forbidden. Generally the thread_state() is _in_Java upon // entry. // // Consider: An interesting optimization is to have the JIT recognize the // following common idiom: // synchronized (someobj) { .... ; notify(); } // That is, we find a notify() or notifyAll() call that immediately precedes // the monitorexit operation. In that case the JIT could fuse the operations // into a single notifyAndExit() runtime primitive. bool ObjectSynchronizer::quick_notify(oopDesc* obj, JavaThread* current, bool all) { assert(current->thread_state() == _thread_in_Java, "invariant"); NoSafepointVerifier nsv; if (obj == nullptr) return false; // slow-path for invalid obj const markWord mark = obj->mark(); if (LockingMode == LM_LIGHTWEIGHT) { if (mark.is_fast_locked() && current->lock_stack().contains(cast_to_oop(obj))) { // Degenerate notify // fast-locked by caller so by definition the implied waitset is empty. return true; } } else if (LockingMode == LM_LEGACY) { if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { // Degenerate notify // stack-locked by caller so by definition the implied waitset is empty. return true; } } if (mark.has_monitor()) { ObjectMonitor* const mon = read_monitor(current, obj, mark); if (LockingMode == LM_LIGHTWEIGHT && mon == nullptr) { // Racing with inflation/deflation go slow path return false; } assert(mon->object() == oop(obj), "invariant"); if (!mon->has_owner(current)) return false; // slow-path for IMS exception if (mon->first_waiter() != nullptr) { // We have one or more waiters. Since this is an inflated monitor // that we own, we quickly notify them here and now, avoiding the slow-path. if (all) { mon->quick_notifyAll(current); } else { mon->quick_notify(current); } } return true; } // other IMS exception states take the slow-path return false; } static bool useHeavyMonitors() { #if defined(X86) || defined(AARCH64) || defined(PPC64) || defined(RISCV64) || defined(S390) return LockingMode == LM_MONITOR; #else return false; #endif } // The LockNode emitted directly at the synchronization site would have // been too big if it were to have included support for the cases of inflated // recursive enter and exit, so they go here instead. // Note that we can't safely call AsyncPrintJavaStack() from within // quick_enter() as our thread state remains _in_Java. bool ObjectSynchronizer::quick_enter_legacy(oop obj, BasicLock* lock, JavaThread* current) { assert(current->thread_state() == _thread_in_Java, "invariant"); if (useHeavyMonitors()) { return false; // Slow path } assert(LockingMode == LM_LEGACY, "legacy mode below"); const markWord mark = obj->mark(); if (mark.has_monitor()) { ObjectMonitor* const m = read_monitor(mark); // An async deflation or GC can race us before we manage to make // the ObjectMonitor busy by setting the owner below. If we detect // that race we just bail out to the slow-path here. if (m->object_peek() == nullptr) { return false; } // Lock contention and Transactional Lock Elision (TLE) diagnostics // and observability // Case: light contention possibly amenable to TLE // Case: TLE inimical operations such as nested/recursive synchronization if (m->has_owner(current)) { m->increment_recursions(current); current->inc_held_monitor_count(); return true; } // This Java Monitor is inflated so obj's header will never be // displaced to this thread's BasicLock. Make the displaced header // non-null so this BasicLock is not seen as recursive nor as // being locked. We do this unconditionally so that this thread's // BasicLock cannot be mis-interpreted by any stack walkers. For // performance reasons, stack walkers generally first check for // stack-locking in the object's header, the second check is for // recursive stack-locking in the displaced header in the BasicLock, // and last are the inflated Java Monitor (ObjectMonitor) checks. lock->set_displaced_header(markWord::unused_mark()); if (!m->has_owner() && m->try_set_owner(current)) { assert(m->recursions() == 0, "invariant"); current->inc_held_monitor_count(); return true; } } // Note that we could inflate in quick_enter. // This is likely a useful optimization // Critically, in quick_enter() we must not: // -- block indefinitely, or // -- reach a safepoint return false; // revert to slow-path } // Handle notifications when synchronizing on value based classes void ObjectSynchronizer::handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread) { assert(locking_thread == Thread::current() || locking_thread->is_obj_deopt_suspend(), "must be"); frame last_frame = locking_thread->last_frame(); bool bcp_was_adjusted = false; // Don't decrement bcp if it points to the frame's first instruction. This happens when // handle_sync_on_value_based_class() is called because of a synchronized method. There // is no actual monitorenter instruction in the byte code in this case. if (last_frame.is_interpreted_frame() && (last_frame.interpreter_frame_method()->code_base() < last_frame.interpreter_frame_bcp())) { // adjust bcp to point back to monitorenter so that we print the correct line numbers last_frame.interpreter_frame_set_bcp(last_frame.interpreter_frame_bcp() - 1); bcp_was_adjusted = true; } if (DiagnoseSyncOnValueBasedClasses == FATAL_EXIT) { ResourceMark rm; stringStream ss; locking_thread->print_active_stack_on(&ss); char* base = (char*)strstr(ss.base(), "at"); char* newline = (char*)strchr(ss.base(), '\n'); if (newline != nullptr) { *newline = '\0'; } fatal("Synchronizing on object " INTPTR_FORMAT " of klass %s %s", p2i(obj()), obj->klass()->external_name(), base); } else { assert(DiagnoseSyncOnValueBasedClasses == LOG_WARNING, "invalid value for DiagnoseSyncOnValueBasedClasses"); ResourceMark rm; Log(valuebasedclasses) vblog; vblog.info("Synchronizing on object " INTPTR_FORMAT " of klass %s", p2i(obj()), obj->klass()->external_name()); if (locking_thread->has_last_Java_frame()) { LogStream info_stream(vblog.info()); locking_thread->print_active_stack_on(&info_stream); } else { vblog.info("Cannot find the last Java frame"); } EventSyncOnValueBasedClass event; if (event.should_commit()) { event.set_valueBasedClass(obj->klass()); event.commit(); } } if (bcp_was_adjusted) { last_frame.interpreter_frame_set_bcp(last_frame.interpreter_frame_bcp() + 1); } } // ----------------------------------------------------------------------------- // Monitor Enter/Exit void ObjectSynchronizer::enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread) { // When called with locking_thread != Thread::current() some mechanism must synchronize // the locking_thread with respect to the current thread. Currently only used when // deoptimizing and re-locking locks. See Deoptimization::relock_objects assert(locking_thread == Thread::current() || locking_thread->is_obj_deopt_suspend(), "must be"); if (LockingMode == LM_LIGHTWEIGHT) { return LightweightSynchronizer::enter_for(obj, lock, locking_thread); } if (!enter_fast_impl(obj, lock, locking_thread)) { // Inflated ObjectMonitor::enter_for is required // An async deflation can race after the inflate_for() call and before // enter_for() can make the ObjectMonitor busy. enter_for() returns false // if we have lost the race to async deflation and we simply try again. while (true) { ObjectMonitor* monitor = inflate_for(locking_thread, obj(), inflate_cause_monitor_enter); if (monitor->enter_for(locking_thread)) { return; } assert(monitor->is_being_async_deflated(), "must be"); } } } void ObjectSynchronizer::enter_legacy(Handle obj, BasicLock* lock, JavaThread* current) { if (!enter_fast_impl(obj, lock, current)) { // Inflated ObjectMonitor::enter is required // An async deflation can race after the inflate() call and before // enter() can make the ObjectMonitor busy. enter() returns false if // we have lost the race to async deflation and we simply try again. while (true) { ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_monitor_enter); if (monitor->enter(current)) { return; } } } } // The interpreter and compiler assembly code tries to lock using the fast path // of this algorithm. Make sure to update that code if the following function is // changed. The implementation is extremely sensitive to race condition. Be careful. bool ObjectSynchronizer::enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread) { assert(LockingMode != LM_LIGHTWEIGHT, "Use LightweightSynchronizer"); if (obj->klass()->is_value_based()) { handle_sync_on_value_based_class(obj, locking_thread); } locking_thread->inc_held_monitor_count(); if (!useHeavyMonitors()) { if (LockingMode == LM_LEGACY) { markWord mark = obj->mark(); if (mark.is_unlocked()) { // Anticipate successful CAS -- the ST of the displaced mark must // be visible <= the ST performed by the CAS. lock->set_displaced_header(mark); if (mark == obj()->cas_set_mark(markWord::from_pointer(lock), mark)) { return true; } } else if (mark.has_locker() && locking_thread->is_lock_owned((address) mark.locker())) { assert(lock != mark.locker(), "must not re-lock the same lock"); assert(lock != (BasicLock*) obj->mark().value(), "don't relock with same BasicLock"); lock->set_displaced_header(markWord::from_pointer(nullptr)); return true; } // The object header will never be displaced to this lock, // so it does not matter what the value is, except that it // must be non-zero to avoid looking like a re-entrant lock, // and must not look locked either. lock->set_displaced_header(markWord::unused_mark()); // Failed to fast lock. return false; } } else if (VerifyHeavyMonitors) { guarantee((obj->mark().value() & markWord::lock_mask_in_place) != markWord::locked_value, "must not be lightweight/stack-locked"); } return false; } void ObjectSynchronizer::exit_legacy(oop object, BasicLock* lock, JavaThread* current) { assert(LockingMode != LM_LIGHTWEIGHT, "Use LightweightSynchronizer"); if (!useHeavyMonitors()) { markWord mark = object->mark(); if (LockingMode == LM_LEGACY) { markWord dhw = lock->displaced_header(); if (dhw.value() == 0) { // If the displaced header is null, then this exit matches up with // a recursive enter. No real work to do here except for diagnostics. #ifndef PRODUCT if (mark != markWord::INFLATING()) { // Only do diagnostics if we are not racing an inflation. Simply // exiting a recursive enter of a Java Monitor that is being // inflated is safe; see the has_monitor() comment below. assert(!mark.is_unlocked(), "invariant"); assert(!mark.has_locker() || current->is_lock_owned((address)mark.locker()), "invariant"); if (mark.has_monitor()) { // The BasicLock's displaced_header is marked as a recursive // enter and we have an inflated Java Monitor (ObjectMonitor). // This is a special case where the Java Monitor was inflated // after this thread entered the stack-lock recursively. When a // Java Monitor is inflated, we cannot safely walk the Java // Monitor owner's stack and update the BasicLocks because a // Java Monitor can be asynchronously inflated by a thread that // does not own the Java Monitor. ObjectMonitor* m = read_monitor(mark); assert(m->object()->mark() == mark, "invariant"); assert(m->is_entered(current), "invariant"); } } #endif return; } if (mark == markWord::from_pointer(lock)) { // If the object is stack-locked by the current thread, try to // swing the displaced header from the BasicLock back to the mark. assert(dhw.is_neutral(), "invariant"); if (object->cas_set_mark(dhw, mark) == mark) { return; } } } } else if (VerifyHeavyMonitors) { guarantee((object->mark().value() & markWord::lock_mask_in_place) != markWord::locked_value, "must not be lightweight/stack-locked"); } // We have to take the slow-path of possible inflation and then exit. // The ObjectMonitor* can't be async deflated until ownership is // dropped inside exit() and the ObjectMonitor* must be !is_busy(). ObjectMonitor* monitor = inflate(current, object, inflate_cause_vm_internal); assert(!monitor->has_anonymous_owner(), "must not be"); monitor->exit(current); } // ----------------------------------------------------------------------------- // JNI locks on java objects // NOTE: must use heavy weight monitor to handle jni monitor enter void ObjectSynchronizer::jni_enter(Handle obj, JavaThread* current) { // Top native frames in the stack will not be seen if we attempt // preemption, since we start walking from the last Java anchor. NoPreemptMark npm(current); if (obj->klass()->is_value_based()) { handle_sync_on_value_based_class(obj, current); } // the current locking is from JNI instead of Java code current->set_current_pending_monitor_is_from_java(false); // An async deflation can race after the inflate() call and before // enter() can make the ObjectMonitor busy. enter() returns false if // we have lost the race to async deflation and we simply try again. while (true) { ObjectMonitor* monitor; bool entered; if (LockingMode == LM_LIGHTWEIGHT) { BasicLock lock; entered = LightweightSynchronizer::inflate_and_enter(obj(), &lock, inflate_cause_jni_enter, current, current) != nullptr; } else { monitor = inflate(current, obj(), inflate_cause_jni_enter); entered = monitor->enter(current); } if (entered) { current->inc_held_monitor_count(1, true); break; } } current->set_current_pending_monitor_is_from_java(true); } // NOTE: must use heavy weight monitor to handle jni monitor exit void ObjectSynchronizer::jni_exit(oop obj, TRAPS) { JavaThread* current = THREAD; ObjectMonitor* monitor; if (LockingMode == LM_LIGHTWEIGHT) { monitor = LightweightSynchronizer::inflate_locked_or_imse(obj, inflate_cause_jni_exit, CHECK); } else { // The ObjectMonitor* can't be async deflated until ownership is // dropped inside exit() and the ObjectMonitor* must be !is_busy(). monitor = inflate(current, obj, inflate_cause_jni_exit); } // If this thread has locked the object, exit the monitor. We // intentionally do not use CHECK on check_owner because we must exit the // monitor even if an exception was already pending. if (monitor->check_owner(THREAD)) { monitor->exit(current); current->dec_held_monitor_count(1, true); } } // ----------------------------------------------------------------------------- // Internal VM locks on java objects // standard constructor, allows locking failures ObjectLocker::ObjectLocker(Handle obj, JavaThread* thread) : _npm(thread) { _thread = thread; _thread->check_for_valid_safepoint_state(); _obj = obj; if (_obj() != nullptr) { ObjectSynchronizer::enter(_obj, &_lock, _thread); } } ObjectLocker::~ObjectLocker() { if (_obj() != nullptr) { ObjectSynchronizer::exit(_obj(), &_lock, _thread); } } // ----------------------------------------------------------------------------- // Wait/Notify/NotifyAll // NOTE: must use heavy weight monitor to handle wait() int ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) { JavaThread* current = THREAD; if (millis < 0) { THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); } ObjectMonitor* monitor; if (LockingMode == LM_LIGHTWEIGHT) { monitor = LightweightSynchronizer::inflate_locked_or_imse(obj(), inflate_cause_wait, CHECK_0); } else { // The ObjectMonitor* can't be async deflated because the _waiters // field is incremented before ownership is dropped and decremented // after ownership is regained. monitor = inflate(current, obj(), inflate_cause_wait); } DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), current, millis); monitor->wait(millis, true, THREAD); // Not CHECK as we need following code // This dummy call is in place to get around dtrace bug 6254741. Once // that's fixed we can uncomment the following line, remove the call // and change this function back into a "void" func. // DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD); int ret_code = dtrace_waited_probe(monitor, obj, THREAD); return ret_code; } void ObjectSynchronizer::waitUninterruptibly(Handle obj, jlong millis, TRAPS) { if (millis < 0) { THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); } ObjectMonitor* monitor; if (LockingMode == LM_LIGHTWEIGHT) { monitor = LightweightSynchronizer::inflate_locked_or_imse(obj(), inflate_cause_wait, CHECK); } else { monitor = inflate(THREAD, obj(), inflate_cause_wait); } monitor->wait(millis, false, THREAD); } void ObjectSynchronizer::notify(Handle obj, TRAPS) { JavaThread* current = THREAD; markWord mark = obj->mark(); if (LockingMode == LM_LIGHTWEIGHT) { if ((mark.is_fast_locked() && current->lock_stack().contains(obj()))) { // Not inflated so there can't be any waiters to notify. return; } } else if (LockingMode == LM_LEGACY) { if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { // Not inflated so there can't be any waiters to notify. return; } } ObjectMonitor* monitor; if (LockingMode == LM_LIGHTWEIGHT) { monitor = LightweightSynchronizer::inflate_locked_or_imse(obj(), inflate_cause_notify, CHECK); } else { // The ObjectMonitor* can't be async deflated until ownership is // dropped by the calling thread. monitor = inflate(current, obj(), inflate_cause_notify); } monitor->notify(CHECK); } // NOTE: see comment of notify() void ObjectSynchronizer::notifyall(Handle obj, TRAPS) { JavaThread* current = THREAD; markWord mark = obj->mark(); if (LockingMode == LM_LIGHTWEIGHT) { if ((mark.is_fast_locked() && current->lock_stack().contains(obj()))) { // Not inflated so there can't be any waiters to notify. return; } } else if (LockingMode == LM_LEGACY) { if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { // Not inflated so there can't be any waiters to notify. return; } } ObjectMonitor* monitor; if (LockingMode == LM_LIGHTWEIGHT) { monitor = LightweightSynchronizer::inflate_locked_or_imse(obj(), inflate_cause_notify, CHECK); } else { // The ObjectMonitor* can't be async deflated until ownership is // dropped by the calling thread. monitor = inflate(current, obj(), inflate_cause_notify); } monitor->notifyAll(CHECK); } // ----------------------------------------------------------------------------- // Hash Code handling struct SharedGlobals { char _pad_prefix[OM_CACHE_LINE_SIZE]; // This is a highly shared mostly-read variable. // To avoid false-sharing it needs to be the sole occupant of a cache line. volatile int stw_random; DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(volatile int)); // Hot RW variable -- Sequester to avoid false-sharing volatile int hc_sequence; DEFINE_PAD_MINUS_SIZE(2, OM_CACHE_LINE_SIZE, sizeof(volatile int)); }; static SharedGlobals GVars; static markWord read_stable_mark(oop obj) { markWord mark = obj->mark_acquire(); if (!mark.is_being_inflated() || LockingMode == LM_LIGHTWEIGHT) { // New lightweight locking does not use the markWord::INFLATING() protocol. return mark; // normal fast-path return } int its = 0; for (;;) { markWord mark = obj->mark_acquire(); if (!mark.is_being_inflated()) { return mark; // normal fast-path return } // The object is being inflated by some other thread. // The caller of read_stable_mark() must wait for inflation to complete. // Avoid live-lock. ++its; if (its > 10000 || !os::is_MP()) { if (its & 1) { os::naked_yield(); } else { // Note that the following code attenuates the livelock problem but is not // a complete remedy. A more complete solution would require that the inflating // thread hold the associated inflation lock. The following code simply restricts // the number of spinners to at most one. We'll have N-2 threads blocked // on the inflationlock, 1 thread holding the inflation lock and using // a yield/park strategy, and 1 thread in the midst of inflation. // A more refined approach would be to change the encoding of INFLATING // to allow encapsulation of a native thread pointer. Threads waiting for // inflation to complete would use CAS to push themselves onto a singly linked // list rooted at the markword. Once enqueued, they'd loop, checking a per-thread flag // and calling park(). When inflation was complete the thread that accomplished inflation // would detach the list and set the markword to inflated with a single CAS and // then for each thread on the list, set the flag and unpark() the thread. // Index into the lock array based on the current object address. static_assert(is_power_of_2(inflation_lock_count()), "must be"); size_t ix = (cast_from_oop(obj) >> 5) & (inflation_lock_count() - 1); int YieldThenBlock = 0; assert(ix < inflation_lock_count(), "invariant"); inflation_lock(ix)->lock(); while (obj->mark_acquire() == markWord::INFLATING()) { // Beware: naked_yield() is advisory and has almost no effect on some platforms // so we periodically call current->_ParkEvent->park(1). // We use a mixed spin/yield/block mechanism. if ((YieldThenBlock++) >= 16) { Thread::current()->_ParkEvent->park(1); } else { os::naked_yield(); } } inflation_lock(ix)->unlock(); } } else { SpinPause(); // SMP-polite spinning } } } // hashCode() generation : // // Possibilities: // * MD5Digest of {obj,stw_random} // * CRC32 of {obj,stw_random} or any linear-feedback shift register function. // * A DES- or AES-style SBox[] mechanism // * One of the Phi-based schemes, such as: // 2654435761 = 2^32 * Phi (golden ratio) // HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stw_random ; // * A variation of Marsaglia's shift-xor RNG scheme. // * (obj ^ stw_random) is appealing, but can result // in undesirable regularity in the hashCode values of adjacent objects // (objects allocated back-to-back, in particular). This could potentially // result in hashtable collisions and reduced hashtable efficiency. // There are simple ways to "diffuse" the middle address bits over the // generated hashCode values: static intptr_t get_next_hash(Thread* current, oop obj) { intptr_t value = 0; if (hashCode == 0) { // This form uses global Park-Miller RNG. // On MP system we'll have lots of RW access to a global, so the // mechanism induces lots of coherency traffic. value = os::random(); } else if (hashCode == 1) { // This variation has the property of being stable (idempotent) // between STW operations. This can be useful in some of the 1-0 // synchronization schemes. intptr_t addr_bits = cast_from_oop(obj) >> 3; value = addr_bits ^ (addr_bits >> 5) ^ GVars.stw_random; } else if (hashCode == 2) { value = 1; // for sensitivity testing } else if (hashCode == 3) { value = ++GVars.hc_sequence; } else if (hashCode == 4) { value = cast_from_oop(obj); } else { // Marsaglia's xor-shift scheme with thread-specific state // This is probably the best overall implementation -- we'll // likely make this the default in future releases. unsigned t = current->_hashStateX; t ^= (t << 11); current->_hashStateX = current->_hashStateY; current->_hashStateY = current->_hashStateZ; current->_hashStateZ = current->_hashStateW; unsigned v = current->_hashStateW; v = (v ^ (v >> 19)) ^ (t ^ (t >> 8)); current->_hashStateW = v; value = v; } value &= markWord::hash_mask; if (value == 0) value = 0xBAD; assert(value != markWord::no_hash, "invariant"); return value; } static intptr_t install_hash_code(Thread* current, oop obj) { assert(UseObjectMonitorTable && LockingMode == LM_LIGHTWEIGHT, "must be"); markWord mark = obj->mark_acquire(); for (;;) { intptr_t hash = mark.hash(); if (hash != 0) { return hash; } hash = get_next_hash(current, obj); const markWord old_mark = mark; const markWord new_mark = old_mark.copy_set_hash(hash); mark = obj->cas_set_mark(new_mark, old_mark); if (old_mark == mark) { return hash; } } } intptr_t ObjectSynchronizer::FastHashCode(Thread* current, oop obj) { if (UseObjectMonitorTable) { // Since the monitor isn't in the object header, the hash can simply be // installed in the object header. return install_hash_code(current, obj); } while (true) { ObjectMonitor* monitor = nullptr; markWord temp, test; intptr_t hash; markWord mark = read_stable_mark(obj); if (VerifyHeavyMonitors) { assert(LockingMode == LM_MONITOR, "+VerifyHeavyMonitors requires LockingMode == 0 (LM_MONITOR)"); guarantee((obj->mark().value() & markWord::lock_mask_in_place) != markWord::locked_value, "must not be lightweight/stack-locked"); } if (mark.is_unlocked() || (LockingMode == LM_LIGHTWEIGHT && mark.is_fast_locked())) { hash = mark.hash(); if (hash != 0) { // if it has a hash, just return it return hash; } hash = get_next_hash(current, obj); // get a new hash temp = mark.copy_set_hash(hash); // merge the hash into header // try to install the hash test = obj->cas_set_mark(temp, mark); if (test == mark) { // if the hash was installed, return it return hash; } if (LockingMode == LM_LIGHTWEIGHT) { // CAS failed, retry continue; } // Failed to install the hash. It could be that another thread // installed the hash just before our attempt or inflation has // occurred or... so we fall thru to inflate the monitor for // stability and then install the hash. } else if (mark.has_monitor()) { monitor = mark.monitor(); temp = monitor->header(); assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value()); hash = temp.hash(); if (hash != 0) { // It has a hash. // Separate load of dmw/header above from the loads in // is_being_async_deflated(). // dmw/header and _contentions may get written by different threads. // Make sure to observe them in the same order when having several observers. OrderAccess::loadload_for_IRIW(); if (monitor->is_being_async_deflated()) { // But we can't safely use the hash if we detect that async // deflation has occurred. So we attempt to restore the // header/dmw to the object's header so that we only retry // once if the deflater thread happens to be slow. monitor->install_displaced_markword_in_object(obj); continue; } return hash; } // Fall thru so we only have one place that installs the hash in // the ObjectMonitor. } else if (LockingMode == LM_LEGACY && mark.has_locker() && current->is_Java_thread() && JavaThread::cast(current)->is_lock_owned((address)mark.locker())) { // This is a stack-lock owned by the calling thread so fetch the // displaced markWord from the BasicLock on the stack. temp = mark.displaced_mark_helper(); assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value()); hash = temp.hash(); if (hash != 0) { // if it has a hash, just return it return hash; } // WARNING: // The displaced header in the BasicLock on a thread's stack // is strictly immutable. It CANNOT be changed in ANY cases. // So we have to inflate the stack-lock into an ObjectMonitor // even if the current thread owns the lock. The BasicLock on // a thread's stack can be asynchronously read by other threads // during an inflate() call so any change to that stack memory // may not propagate to other threads correctly. } // Inflate the monitor to set the hash. // There's no need to inflate if the mark has already got a monitor. // NOTE: an async deflation can race after we get the monitor and // before we can update the ObjectMonitor's header with the hash // value below. monitor = mark.has_monitor() ? mark.monitor() : inflate(current, obj, inflate_cause_hash_code); // Load ObjectMonitor's header/dmw field and see if it has a hash. mark = monitor->header(); assert(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value()); hash = mark.hash(); if (hash == 0) { // if it does not have a hash hash = get_next_hash(current, obj); // get a new hash temp = mark.copy_set_hash(hash) ; // merge the hash into header assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value()); uintptr_t v = Atomic::cmpxchg(monitor->metadata_addr(), mark.value(), temp.value()); test = markWord(v); if (test != mark) { // The attempt to update the ObjectMonitor's header/dmw field // did not work. This can happen if another thread managed to // merge in the hash just before our cmpxchg(). // If we add any new usages of the header/dmw field, this code // will need to be updated. hash = test.hash(); assert(test.is_neutral(), "invariant: header=" INTPTR_FORMAT, test.value()); assert(hash != 0, "should only have lost the race to a thread that set a non-zero hash"); } if (monitor->is_being_async_deflated() && !UseObjectMonitorTable) { // If we detect that async deflation has occurred, then we // attempt to restore the header/dmw to the object's header // so that we only retry once if the deflater thread happens // to be slow. monitor->install_displaced_markword_in_object(obj); continue; } } // We finally get the hash. return hash; } } bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* current, Handle h_obj) { assert(current == JavaThread::current(), "Can only be called on current thread"); oop obj = h_obj(); markWord mark = read_stable_mark(obj); if (LockingMode == LM_LEGACY && mark.has_locker()) { // stack-locked case, header points into owner's stack return current->is_lock_owned((address)mark.locker()); } if (LockingMode == LM_LIGHTWEIGHT && mark.is_fast_locked()) { // fast-locking case, see if lock is in current's lock stack return current->lock_stack().contains(h_obj()); } while (LockingMode == LM_LIGHTWEIGHT && mark.has_monitor()) { ObjectMonitor* monitor = read_monitor(current, obj, mark); if (monitor != nullptr) { return monitor->is_entered(current) != 0; } // Racing with inflation/deflation, retry mark = obj->mark_acquire(); if (mark.is_fast_locked()) { // Some other thread fast_locked, current could not have held the lock return false; } } if (LockingMode != LM_LIGHTWEIGHT && mark.has_monitor()) { // Inflated monitor so header points to ObjectMonitor (tagged pointer). // The first stage of async deflation does not affect any field // used by this comparison so the ObjectMonitor* is usable here. ObjectMonitor* monitor = read_monitor(mark); return monitor->is_entered(current) != 0; } // Unlocked case, header in place assert(mark.is_unlocked(), "sanity check"); return false; } JavaThread* ObjectSynchronizer::get_lock_owner(ThreadsList * t_list, Handle h_obj) { oop obj = h_obj(); markWord mark = read_stable_mark(obj); if (LockingMode == LM_LEGACY && mark.has_locker()) { // stack-locked so header points into owner's stack. // owning_thread_from_monitor_owner() may also return null here: return Threads::owning_thread_from_stacklock(t_list, (address) mark.locker()); } if (LockingMode == LM_LIGHTWEIGHT && mark.is_fast_locked()) { // fast-locked so get owner from the object. // owning_thread_from_object() may also return null here: return Threads::owning_thread_from_object(t_list, h_obj()); } while (LockingMode == LM_LIGHTWEIGHT && mark.has_monitor()) { ObjectMonitor* monitor = read_monitor(Thread::current(), obj, mark); if (monitor != nullptr) { return Threads::owning_thread_from_monitor(t_list, monitor); } // Racing with inflation/deflation, retry mark = obj->mark_acquire(); if (mark.is_fast_locked()) { // Some other thread fast_locked return Threads::owning_thread_from_object(t_list, h_obj()); } } if (LockingMode != LM_LIGHTWEIGHT && mark.has_monitor()) { // Inflated monitor so header points to ObjectMonitor (tagged pointer). // The first stage of async deflation does not affect any field // used by this comparison so the ObjectMonitor* is usable here. ObjectMonitor* monitor = read_monitor(mark); assert(monitor != nullptr, "monitor should be non-null"); // owning_thread_from_monitor() may also return null here: return Threads::owning_thread_from_monitor(t_list, monitor); } // Unlocked case, header in place // Cannot have assertion since this object may have been // locked by another thread when reaching here. // assert(mark.is_unlocked(), "sanity check"); return nullptr; } // Visitors ... // Iterate over all ObjectMonitors. template void ObjectSynchronizer::monitors_iterate(Function function) { MonitorList::Iterator iter = _in_use_list.iterator(); while (iter.has_next()) { ObjectMonitor* monitor = iter.next(); function(monitor); } } // Iterate ObjectMonitors owned by any thread and where the owner `filter` // returns true. template void ObjectSynchronizer::owned_monitors_iterate_filtered(MonitorClosure* closure, OwnerFilter filter) { monitors_iterate([&](ObjectMonitor* monitor) { // This function is only called at a safepoint or when the // target thread is suspended or when the target thread is // operating on itself. The current closures in use today are // only interested in an owned ObjectMonitor and ownership // cannot be dropped under the calling contexts so the // ObjectMonitor cannot be async deflated. if (monitor->has_owner() && filter(monitor)) { assert(!monitor->is_being_async_deflated(), "Owned monitors should not be deflating"); closure->do_monitor(monitor); } }); } // Iterate ObjectMonitors where the owner == thread; this does NOT include // ObjectMonitors where owner is set to a stack-lock address in thread. void ObjectSynchronizer::owned_monitors_iterate(MonitorClosure* closure, JavaThread* thread) { int64_t key = ObjectMonitor::owner_id_from(thread); auto thread_filter = [&](ObjectMonitor* monitor) { return monitor->owner() == key; }; return owned_monitors_iterate_filtered(closure, thread_filter); } void ObjectSynchronizer::owned_monitors_iterate(MonitorClosure* closure, oop vthread) { int64_t key = ObjectMonitor::owner_id_from(vthread); auto thread_filter = [&](ObjectMonitor* monitor) { return monitor->owner() == key; }; return owned_monitors_iterate_filtered(closure, thread_filter); } // Iterate ObjectMonitors owned by any thread. void ObjectSynchronizer::owned_monitors_iterate(MonitorClosure* closure) { auto all_filter = [&](ObjectMonitor* monitor) { return true; }; return owned_monitors_iterate_filtered(closure, all_filter); } static bool monitors_used_above_threshold(MonitorList* list) { if (MonitorUsedDeflationThreshold == 0) { // disabled case is easy return false; } size_t monitors_used = list->count(); if (monitors_used == 0) { // empty list is easy return false; } size_t old_ceiling = ObjectSynchronizer::in_use_list_ceiling(); // Make sure that we use a ceiling value that is not lower than // previous, not lower than the recorded max used by the system, and // not lower than the current number of monitors in use (which can // race ahead of max). The result is guaranteed > 0. size_t ceiling = MAX3(old_ceiling, list->max(), monitors_used); // Check if our monitor usage is above the threshold: size_t monitor_usage = (monitors_used * 100LL) / ceiling; if (int(monitor_usage) > MonitorUsedDeflationThreshold) { // Deflate monitors if over the threshold percentage, unless no // progress on previous deflations. bool is_above_threshold = true; // Check if it's time to adjust the in_use_list_ceiling up, due // to too many async deflation attempts without any progress. if (NoAsyncDeflationProgressMax != 0 && _no_progress_cnt >= NoAsyncDeflationProgressMax) { double remainder = (100.0 - MonitorUsedDeflationThreshold) / 100.0; size_t delta = (size_t)(ceiling * remainder) + 1; size_t new_ceiling = (ceiling > SIZE_MAX - delta) ? SIZE_MAX // Overflow, let's clamp new_ceiling. : ceiling + delta; ObjectSynchronizer::set_in_use_list_ceiling(new_ceiling); log_info(monitorinflation)("Too many deflations without progress; " "bumping in_use_list_ceiling from %zu" " to %zu", old_ceiling, new_ceiling); _no_progress_cnt = 0; ceiling = new_ceiling; // Check if our monitor usage is still above the threshold: monitor_usage = (monitors_used * 100LL) / ceiling; is_above_threshold = int(monitor_usage) > MonitorUsedDeflationThreshold; } log_info(monitorinflation)("monitors_used=%zu, ceiling=%zu" ", monitor_usage=%zu, threshold=%d", monitors_used, ceiling, monitor_usage, MonitorUsedDeflationThreshold); return is_above_threshold; } return false; } size_t ObjectSynchronizer::in_use_list_count() { return _in_use_list.count(); } size_t ObjectSynchronizer::in_use_list_max() { return _in_use_list.max(); } size_t ObjectSynchronizer::in_use_list_ceiling() { return _in_use_list_ceiling; } void ObjectSynchronizer::dec_in_use_list_ceiling() { Atomic::sub(&_in_use_list_ceiling, AvgMonitorsPerThreadEstimate); } void ObjectSynchronizer::inc_in_use_list_ceiling() { Atomic::add(&_in_use_list_ceiling, AvgMonitorsPerThreadEstimate); } void ObjectSynchronizer::set_in_use_list_ceiling(size_t new_value) { _in_use_list_ceiling = new_value; } bool ObjectSynchronizer::is_async_deflation_needed() { if (is_async_deflation_requested()) { // Async deflation request. log_info(monitorinflation)("Async deflation needed: explicit request"); return true; } jlong time_since_last = time_since_last_async_deflation_ms(); if (AsyncDeflationInterval > 0 && time_since_last > AsyncDeflationInterval && monitors_used_above_threshold(&_in_use_list)) { // It's been longer than our specified deflate interval and there // are too many monitors in use. We don't deflate more frequently // than AsyncDeflationInterval (unless is_async_deflation_requested) // in order to not swamp the MonitorDeflationThread. log_info(monitorinflation)("Async deflation needed: monitors used are above the threshold"); return true; } if (GuaranteedAsyncDeflationInterval > 0 && time_since_last > GuaranteedAsyncDeflationInterval) { // It's been longer than our specified guaranteed deflate interval. // We need to clean up the used monitors even if the threshold is // not reached, to keep the memory utilization at bay when many threads // touched many monitors. log_info(monitorinflation)("Async deflation needed: guaranteed interval (%zd ms) " "is greater than time since last deflation (" JLONG_FORMAT " ms)", GuaranteedAsyncDeflationInterval, time_since_last); // If this deflation has no progress, then it should not affect the no-progress // tracking, otherwise threshold heuristics would think it was triggered, experienced // no progress, and needs to backoff more aggressively. In this "no progress" case, // the generic code would bump the no-progress counter, and we compensate for that // by telling it to skip the update. // // If this deflation has progress, then it should let non-progress tracking // know about this, otherwise the threshold heuristics would kick in, potentially // experience no-progress due to aggressive cleanup by this deflation, and think // it is still in no-progress stride. In this "progress" case, the generic code would // zero the counter, and we allow it to happen. _no_progress_skip_increment = true; return true; } return false; } void ObjectSynchronizer::request_deflate_idle_monitors() { MonitorLocker ml(MonitorDeflation_lock, Mutex::_no_safepoint_check_flag); set_is_async_deflation_requested(true); ml.notify_all(); } bool ObjectSynchronizer::request_deflate_idle_monitors_from_wb() { JavaThread* current = JavaThread::current(); bool ret_code = false; jlong last_time = last_async_deflation_time_ns(); request_deflate_idle_monitors(); const int N_CHECKS = 5; for (int i = 0; i < N_CHECKS; i++) { // sleep for at most 5 seconds if (last_async_deflation_time_ns() > last_time) { log_info(monitorinflation)("Async Deflation happened after %d check(s).", i); ret_code = true; break; } { // JavaThread has to honor the blocking protocol. ThreadBlockInVM tbivm(current); os::naked_short_sleep(999); // sleep for almost 1 second } } if (!ret_code) { log_info(monitorinflation)("Async Deflation DID NOT happen after %d checks.", N_CHECKS); } return ret_code; } jlong ObjectSynchronizer::time_since_last_async_deflation_ms() { return (os::javaTimeNanos() - last_async_deflation_time_ns()) / (NANOUNITS / MILLIUNITS); } static void post_monitor_inflate_event(EventJavaMonitorInflate* event, const oop obj, ObjectSynchronizer::InflateCause cause) { assert(event != nullptr, "invariant"); const Klass* monitor_klass = obj->klass(); if (ObjectMonitor::is_jfr_excluded(monitor_klass)) { return; } event->set_monitorClass(monitor_klass); event->set_address((uintptr_t)(void*)obj); event->set_cause((u1)cause); event->commit(); } // Fast path code shared by multiple functions void ObjectSynchronizer::inflate_helper(oop obj) { assert(LockingMode != LM_LIGHTWEIGHT, "only inflate through enter"); markWord mark = obj->mark_acquire(); if (mark.has_monitor()) { ObjectMonitor* monitor = read_monitor(mark); markWord dmw = monitor->header(); assert(dmw.is_neutral(), "sanity check: header=" INTPTR_FORMAT, dmw.value()); return; } (void)inflate(Thread::current(), obj, inflate_cause_vm_internal); } ObjectMonitor* ObjectSynchronizer::inflate(Thread* current, oop obj, const InflateCause cause) { assert(current == Thread::current(), "must be"); assert(LockingMode != LM_LIGHTWEIGHT, "only inflate through enter"); return inflate_impl(current->is_Java_thread() ? JavaThread::cast(current) : nullptr, obj, cause); } ObjectMonitor* ObjectSynchronizer::inflate_for(JavaThread* thread, oop obj, const InflateCause cause) { assert(thread == Thread::current() || thread->is_obj_deopt_suspend(), "must be"); assert(LockingMode != LM_LIGHTWEIGHT, "LM_LIGHTWEIGHT cannot use inflate_for"); return inflate_impl(thread, obj, cause); } ObjectMonitor* ObjectSynchronizer::inflate_impl(JavaThread* locking_thread, oop object, const InflateCause cause) { // The JavaThread* locking_thread requires that the locking_thread == Thread::current() or // is suspended throughout the call by some other mechanism. // The thread might be nullptr when called from a non JavaThread. (As may still be // the case from FastHashCode). However it is only important for correctness that the // thread is set when called from ObjectSynchronizer::enter from the owning thread, // ObjectSynchronizer::enter_for from any thread, or ObjectSynchronizer::exit. assert(LockingMode != LM_LIGHTWEIGHT, "LM_LIGHTWEIGHT cannot use inflate_impl"); EventJavaMonitorInflate event; for (;;) { const markWord mark = object->mark_acquire(); // The mark can be in one of the following states: // * inflated - If the ObjectMonitor owner is anonymous and the // locking_thread owns the object lock, then we // make the locking_thread the ObjectMonitor owner. // * stack-locked - Coerce it to inflated from stack-locked. // * INFLATING - Busy wait for conversion from stack-locked to // inflated. // * unlocked - Aggressively inflate the object. // CASE: inflated if (mark.has_monitor()) { ObjectMonitor* inf = mark.monitor(); markWord dmw = inf->header(); assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value()); if (inf->has_anonymous_owner() && locking_thread != nullptr) { assert(LockingMode == LM_LEGACY, "invariant"); if (locking_thread->is_lock_owned((address)inf->stack_locker())) { inf->set_stack_locker(nullptr); inf->set_owner_from_anonymous(locking_thread); } } return inf; } // CASE: inflation in progress - inflating over a stack-lock. // Some other thread is converting from stack-locked to inflated. // Only that thread can complete inflation -- other threads must wait. // The INFLATING value is transient. // Currently, we spin/yield/park and poll the markword, waiting for inflation to finish. // We could always eliminate polling by parking the thread on some auxiliary list. if (mark == markWord::INFLATING()) { read_stable_mark(object); continue; } // CASE: stack-locked // Could be stack-locked either by current or by some other thread. // // Note that we allocate the ObjectMonitor speculatively, _before_ attempting // to install INFLATING into the mark word. We originally installed INFLATING, // allocated the ObjectMonitor, and then finally STed the address of the // ObjectMonitor into the mark. This was correct, but artificially lengthened // the interval in which INFLATING appeared in the mark, thus increasing // the odds of inflation contention. If we lose the race to set INFLATING, // then we just delete the ObjectMonitor and loop around again. // LogStreamHandle(Trace, monitorinflation) lsh; if (LockingMode == LM_LEGACY && mark.has_locker()) { ObjectMonitor* m = new ObjectMonitor(object); // Optimistically prepare the ObjectMonitor - anticipate successful CAS // We do this before the CAS in order to minimize the length of time // in which INFLATING appears in the mark. markWord cmp = object->cas_set_mark(markWord::INFLATING(), mark); if (cmp != mark) { delete m; continue; // Interference -- just retry } // We've successfully installed INFLATING (0) into the mark-word. // This is the only case where 0 will appear in a mark-word. // Only the singular thread that successfully swings the mark-word // to 0 can perform (or more precisely, complete) inflation. // // Why do we CAS a 0 into the mark-word instead of just CASing the // mark-word from the stack-locked value directly to the new inflated state? // Consider what happens when a thread unlocks a stack-locked object. // It attempts to use CAS to swing the displaced header value from the // on-stack BasicLock back into the object header. Recall also that the // header value (hash code, etc) can reside in (a) the object header, or // (b) a displaced header associated with the stack-lock, or (c) a displaced // header in an ObjectMonitor. The inflate() routine must copy the header // value from the BasicLock on the owner's stack to the ObjectMonitor, all // the while preserving the hashCode stability invariants. If the owner // decides to release the lock while the value is 0, the unlock will fail // and control will eventually pass from slow_exit() to inflate. The owner // will then spin, waiting for the 0 value to disappear. Put another way, // the 0 causes the owner to stall if the owner happens to try to // drop the lock (restoring the header from the BasicLock to the object) // while inflation is in-progress. This protocol avoids races that might // would otherwise permit hashCode values to change or "flicker" for an object. // Critically, while object->mark is 0 mark.displaced_mark_helper() is stable. // 0 serves as a "BUSY" inflate-in-progress indicator. // fetch the displaced mark from the owner's stack. // The owner can't die or unwind past the lock while our INFLATING // object is in the mark. Furthermore the owner can't complete // an unlock on the object, either. markWord dmw = mark.displaced_mark_helper(); // Catch if the object's header is not neutral (not locked and // not marked is what we care about here). assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value()); // Setup monitor fields to proper values -- prepare the monitor m->set_header(dmw); // Note that a thread can inflate an object // that it has stack-locked -- as might happen in wait() -- directly // with CAS. That is, we can avoid the xchg-nullptr .... ST idiom. if (locking_thread != nullptr && locking_thread->is_lock_owned((address)mark.locker())) { m->set_owner(locking_thread); } else { // Use ANONYMOUS_OWNER to indicate that the owner is the BasicLock on the stack, // and set the stack locker field in the monitor. m->set_stack_locker(mark.locker()); m->set_anonymous_owner(); } // TODO-FIXME: assert BasicLock->dhw != 0. // Must preserve store ordering. The monitor state must // be stable at the time of publishing the monitor address. guarantee(object->mark() == markWord::INFLATING(), "invariant"); // Release semantics so that above set_object() is seen first. object->release_set_mark(markWord::encode(m)); // Once ObjectMonitor is configured and the object is associated // with the ObjectMonitor, it is safe to allow async deflation: _in_use_list.add(m); if (log_is_enabled(Trace, monitorinflation)) { ResourceMark rm; lsh.print_cr("inflate(has_locker): object=" INTPTR_FORMAT ", mark=" INTPTR_FORMAT ", type='%s'", p2i(object), object->mark().value(), object->klass()->external_name()); } if (event.should_commit()) { post_monitor_inflate_event(&event, object, cause); } return m; } // CASE: unlocked // TODO-FIXME: for entry we currently inflate and then try to CAS _owner. // If we know we're inflating for entry it's better to inflate by swinging a // pre-locked ObjectMonitor pointer into the object header. A successful // CAS inflates the object *and* confers ownership to the inflating thread. // In the current implementation we use a 2-step mechanism where we CAS() // to inflate and then CAS() again to try to swing _owner from null to current. // An inflateTry() method that we could call from enter() would be useful. assert(mark.is_unlocked(), "invariant: header=" INTPTR_FORMAT, mark.value()); ObjectMonitor* m = new ObjectMonitor(object); // prepare m for installation - set monitor to initial state m->set_header(mark); if (object->cas_set_mark(markWord::encode(m), mark) != mark) { delete m; m = nullptr; continue; // interference - the markword changed - just retry. // The state-transitions are one-way, so there's no chance of // live-lock -- "Inflated" is an absorbing state. } // Once the ObjectMonitor is configured and object is associated // with the ObjectMonitor, it is safe to allow async deflation: _in_use_list.add(m); if (log_is_enabled(Trace, monitorinflation)) { ResourceMark rm; lsh.print_cr("inflate(unlocked): object=" INTPTR_FORMAT ", mark=" INTPTR_FORMAT ", type='%s'", p2i(object), object->mark().value(), object->klass()->external_name()); } if (event.should_commit()) { post_monitor_inflate_event(&event, object, cause); } return m; } } // Walk the in-use list and deflate (at most MonitorDeflationMax) idle // ObjectMonitors. Returns the number of deflated ObjectMonitors. // size_t ObjectSynchronizer::deflate_monitor_list(ObjectMonitorDeflationSafepointer* safepointer) { MonitorList::Iterator iter = _in_use_list.iterator(); size_t deflated_count = 0; Thread* current = Thread::current(); while (iter.has_next()) { if (deflated_count >= (size_t)MonitorDeflationMax) { break; } ObjectMonitor* mid = iter.next(); if (mid->deflate_monitor(current)) { deflated_count++; } // Must check for a safepoint/handshake and honor it. safepointer->block_for_safepoint("deflation", "deflated_count", deflated_count); } return deflated_count; } class HandshakeForDeflation : public HandshakeClosure { public: HandshakeForDeflation() : HandshakeClosure("HandshakeForDeflation") {} void do_thread(Thread* thread) { log_trace(monitorinflation)("HandshakeForDeflation::do_thread: thread=" INTPTR_FORMAT, p2i(thread)); if (thread->is_Java_thread()) { // Clear OM cache JavaThread* jt = JavaThread::cast(thread); jt->om_clear_monitor_cache(); } } }; class VM_RendezvousGCThreads : public VM_Operation { public: bool evaluate_at_safepoint() const override { return false; } VMOp_Type type() const override { return VMOp_RendezvousGCThreads; } void doit() override { Universe::heap()->safepoint_synchronize_begin(); Universe::heap()->safepoint_synchronize_end(); }; }; static size_t delete_monitors(GrowableArray* delete_list, ObjectMonitorDeflationSafepointer* safepointer) { NativeHeapTrimmer::SuspendMark sm("monitor deletion"); size_t deleted_count = 0; for (ObjectMonitor* monitor: *delete_list) { delete monitor; deleted_count++; // A JavaThread must check for a safepoint/handshake and honor it. safepointer->block_for_safepoint("deletion", "deleted_count", deleted_count); } return deleted_count; } class ObjectMonitorDeflationLogging: public StackObj { LogStreamHandle(Debug, monitorinflation) _debug; LogStreamHandle(Info, monitorinflation) _info; LogStream* _stream; elapsedTimer _timer; size_t ceiling() const { return ObjectSynchronizer::in_use_list_ceiling(); } size_t count() const { return ObjectSynchronizer::in_use_list_count(); } size_t max() const { return ObjectSynchronizer::in_use_list_max(); } public: ObjectMonitorDeflationLogging() : _debug(), _info(), _stream(nullptr) { if (_debug.is_enabled()) { _stream = &_debug; } else if (_info.is_enabled()) { _stream = &_info; } } void begin() { if (_stream != nullptr) { _stream->print_cr("begin deflating: in_use_list stats: ceiling=%zu, count=%zu, max=%zu", ceiling(), count(), max()); _timer.start(); } } void before_handshake(size_t unlinked_count) { if (_stream != nullptr) { _timer.stop(); _stream->print_cr("before handshaking: unlinked_count=%zu" ", in_use_list stats: ceiling=%zu, count=" "%zu, max=%zu", unlinked_count, ceiling(), count(), max()); } } void after_handshake() { if (_stream != nullptr) { _stream->print_cr("after handshaking: in_use_list stats: ceiling=" "%zu, count=%zu, max=%zu", ceiling(), count(), max()); _timer.start(); } } void end(size_t deflated_count, size_t unlinked_count) { if (_stream != nullptr) { _timer.stop(); if (deflated_count != 0 || unlinked_count != 0 || _debug.is_enabled()) { _stream->print_cr("deflated_count=%zu, {unlinked,deleted}_count=%zu monitors in %3.7f secs", deflated_count, unlinked_count, _timer.seconds()); } _stream->print_cr("end deflating: in_use_list stats: ceiling=%zu, count=%zu, max=%zu", ceiling(), count(), max()); } } void before_block_for_safepoint(const char* op_name, const char* cnt_name, size_t cnt) { if (_stream != nullptr) { _timer.stop(); _stream->print_cr("pausing %s: %s=%zu, in_use_list stats: ceiling=" "%zu, count=%zu, max=%zu", op_name, cnt_name, cnt, ceiling(), count(), max()); } } void after_block_for_safepoint(const char* op_name) { if (_stream != nullptr) { _stream->print_cr("resuming %s: in_use_list stats: ceiling=%zu" ", count=%zu, max=%zu", op_name, ceiling(), count(), max()); _timer.start(); } } }; void ObjectMonitorDeflationSafepointer::block_for_safepoint(const char* op_name, const char* count_name, size_t counter) { if (!SafepointMechanism::should_process(_current)) { return; } // A safepoint/handshake has started. _log->before_block_for_safepoint(op_name, count_name, counter); { // Honor block request. ThreadBlockInVM tbivm(_current); } _log->after_block_for_safepoint(op_name); } // This function is called by the MonitorDeflationThread to deflate // ObjectMonitors. size_t ObjectSynchronizer::deflate_idle_monitors() { JavaThread* current = JavaThread::current(); assert(current->is_monitor_deflation_thread(), "The only monitor deflater"); // The async deflation request has been processed. _last_async_deflation_time_ns = os::javaTimeNanos(); set_is_async_deflation_requested(false); ObjectMonitorDeflationLogging log; ObjectMonitorDeflationSafepointer safepointer(current, &log); log.begin(); // Deflate some idle ObjectMonitors. size_t deflated_count = deflate_monitor_list(&safepointer); // Unlink the deflated ObjectMonitors from the in-use list. size_t unlinked_count = 0; size_t deleted_count = 0; if (deflated_count > 0) { ResourceMark rm(current); GrowableArray delete_list((int)deflated_count); unlinked_count = _in_use_list.unlink_deflated(deflated_count, &delete_list, &safepointer); #ifdef ASSERT if (UseObjectMonitorTable) { for (ObjectMonitor* monitor : delete_list) { assert(!LightweightSynchronizer::contains_monitor(current, monitor), "Should have been removed"); } } #endif log.before_handshake(unlinked_count); // A JavaThread needs to handshake in order to safely free the // ObjectMonitors that were deflated in this cycle. HandshakeForDeflation hfd_hc; Handshake::execute(&hfd_hc); // Also, we sync and desync GC threads around the handshake, so that they can // safely read the mark-word and look-through to the object-monitor, without // being afraid that the object-monitor is going away. VM_RendezvousGCThreads sync_gc; VMThread::execute(&sync_gc); log.after_handshake(); // After the handshake, safely free the ObjectMonitors that were // deflated and unlinked in this cycle. // Delete the unlinked ObjectMonitors. deleted_count = delete_monitors(&delete_list, &safepointer); assert(unlinked_count == deleted_count, "must be"); } log.end(deflated_count, unlinked_count); GVars.stw_random = os::random(); if (deflated_count != 0) { _no_progress_cnt = 0; } else if (_no_progress_skip_increment) { _no_progress_skip_increment = false; } else { _no_progress_cnt++; } return deflated_count; } // Monitor cleanup on JavaThread::exit // Iterate through monitor cache and attempt to release thread's monitors class ReleaseJavaMonitorsClosure: public MonitorClosure { private: JavaThread* _thread; public: ReleaseJavaMonitorsClosure(JavaThread* thread) : _thread(thread) {} void do_monitor(ObjectMonitor* mid) { intx rec = mid->complete_exit(_thread); _thread->dec_held_monitor_count(rec + 1); } }; // Release all inflated monitors owned by current thread. Lightweight monitors are // ignored. This is meant to be called during JNI thread detach which assumes // all remaining monitors are heavyweight. All exceptions are swallowed. // Scanning the extant monitor list can be time consuming. // A simple optimization is to add a per-thread flag that indicates a thread // called jni_monitorenter() during its lifetime. // // Instead of NoSafepointVerifier it might be cheaper to // use an idiom of the form: // auto int tmp = SafepointSynchronize::_safepoint_counter ; // // guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ; // Since the tests are extremely cheap we could leave them enabled // for normal product builds. void ObjectSynchronizer::release_monitors_owned_by_thread(JavaThread* current) { assert(current == JavaThread::current(), "must be current Java thread"); NoSafepointVerifier nsv; ReleaseJavaMonitorsClosure rjmc(current); ObjectSynchronizer::owned_monitors_iterate(&rjmc, current); assert(!current->has_pending_exception(), "Should not be possible"); current->clear_pending_exception(); assert(current->held_monitor_count() == 0, "Should not be possible"); // All monitors (including entered via JNI) have been unlocked above, so we need to clear jni count. current->clear_jni_monitor_count(); } const char* ObjectSynchronizer::inflate_cause_name(const InflateCause cause) { switch (cause) { case inflate_cause_vm_internal: return "VM Internal"; case inflate_cause_monitor_enter: return "Monitor Enter"; case inflate_cause_wait: return "Monitor Wait"; case inflate_cause_notify: return "Monitor Notify"; case inflate_cause_hash_code: return "Monitor Hash Code"; case inflate_cause_jni_enter: return "JNI Monitor Enter"; case inflate_cause_jni_exit: return "JNI Monitor Exit"; default: ShouldNotReachHere(); } return "Unknown"; } //------------------------------------------------------------------------------ // Debugging code u_char* ObjectSynchronizer::get_gvars_addr() { return (u_char*)&GVars; } u_char* ObjectSynchronizer::get_gvars_hc_sequence_addr() { return (u_char*)&GVars.hc_sequence; } size_t ObjectSynchronizer::get_gvars_size() { return sizeof(SharedGlobals); } u_char* ObjectSynchronizer::get_gvars_stw_random_addr() { return (u_char*)&GVars.stw_random; } // Do the final audit and print of ObjectMonitor stats; must be done // by the VMThread at VM exit time. void ObjectSynchronizer::do_final_audit_and_print_stats() { assert(Thread::current()->is_VM_thread(), "sanity check"); if (is_final_audit()) { // Only do the audit once. return; } set_is_final_audit(); log_info(monitorinflation)("Starting the final audit."); if (log_is_enabled(Info, monitorinflation)) { LogStreamHandle(Info, monitorinflation) ls; audit_and_print_stats(&ls, true /* on_exit */); } } // This function can be called by the MonitorDeflationThread or it can be called when // we are trying to exit the VM. The list walker functions can run in parallel with // the other list operations. // Calls to this function can be added in various places as a debugging // aid. // void ObjectSynchronizer::audit_and_print_stats(outputStream* ls, bool on_exit) { int error_cnt = 0; ls->print_cr("Checking in_use_list:"); chk_in_use_list(ls, &error_cnt); if (error_cnt == 0) { ls->print_cr("No errors found in in_use_list checks."); } else { log_error(monitorinflation)("found in_use_list errors: error_cnt=%d", error_cnt); } // When exiting, only log the interesting entries at the Info level. // When called at intervals by the MonitorDeflationThread, log output // at the Trace level since there can be a lot of it. if (!on_exit && log_is_enabled(Trace, monitorinflation)) { LogStreamHandle(Trace, monitorinflation) ls_tr; log_in_use_monitor_details(&ls_tr, true /* log_all */); } else if (on_exit) { log_in_use_monitor_details(ls, false /* log_all */); } ls->flush(); guarantee(error_cnt == 0, "ERROR: found monitor list errors: error_cnt=%d", error_cnt); } // Check the in_use_list; log the results of the checks. void ObjectSynchronizer::chk_in_use_list(outputStream* out, int *error_cnt_p) { size_t l_in_use_count = _in_use_list.count(); size_t l_in_use_max = _in_use_list.max(); out->print_cr("count=%zu, max=%zu", l_in_use_count, l_in_use_max); size_t ck_in_use_count = 0; MonitorList::Iterator iter = _in_use_list.iterator(); while (iter.has_next()) { ObjectMonitor* mid = iter.next(); chk_in_use_entry(mid, out, error_cnt_p); ck_in_use_count++; } if (l_in_use_count == ck_in_use_count) { out->print_cr("in_use_count=%zu equals ck_in_use_count=%zu", l_in_use_count, ck_in_use_count); } else { out->print_cr("WARNING: in_use_count=%zu is not equal to " "ck_in_use_count=%zu", l_in_use_count, ck_in_use_count); } size_t ck_in_use_max = _in_use_list.max(); if (l_in_use_max == ck_in_use_max) { out->print_cr("in_use_max=%zu equals ck_in_use_max=%zu", l_in_use_max, ck_in_use_max); } else { out->print_cr("WARNING: in_use_max=%zu is not equal to " "ck_in_use_max=%zu", l_in_use_max, ck_in_use_max); } } // Check an in-use monitor entry; log any errors. void ObjectSynchronizer::chk_in_use_entry(ObjectMonitor* n, outputStream* out, int* error_cnt_p) { if (n->owner_is_DEFLATER_MARKER()) { // This could happen when monitor deflation blocks for a safepoint. return; } if (n->metadata() == 0) { out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor must " "have non-null _metadata (header/hash) field.", p2i(n)); *error_cnt_p = *error_cnt_p + 1; } const oop obj = n->object_peek(); if (obj == nullptr) { return; } const markWord mark = obj->mark(); if (!mark.has_monitor()) { out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor's " "object does not think it has a monitor: obj=" INTPTR_FORMAT ", mark=" INTPTR_FORMAT, p2i(n), p2i(obj), mark.value()); *error_cnt_p = *error_cnt_p + 1; return; } ObjectMonitor* const obj_mon = read_monitor(Thread::current(), obj, mark); if (n != obj_mon) { out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor's " "object does not refer to the same monitor: obj=" INTPTR_FORMAT ", mark=" INTPTR_FORMAT ", obj_mon=" INTPTR_FORMAT, p2i(n), p2i(obj), mark.value(), p2i(obj_mon)); *error_cnt_p = *error_cnt_p + 1; } } // Log details about ObjectMonitors on the in_use_list. The 'BHL' // flags indicate why the entry is in-use, 'object' and 'object type' // indicate the associated object and its type. void ObjectSynchronizer::log_in_use_monitor_details(outputStream* out, bool log_all) { if (_in_use_list.count() > 0) { stringStream ss; out->print_cr("In-use monitor info%s:", log_all ? "" : " (eliding idle monitors)"); out->print_cr("(B -> is_busy, H -> has hash code, L -> lock status)"); out->print_cr("%18s %s %18s %18s", "monitor", "BHL", "object", "object type"); out->print_cr("================== === ================== =================="); auto is_interesting = [&](ObjectMonitor* monitor) { return log_all || monitor->has_owner() || monitor->is_busy(); }; monitors_iterate([&](ObjectMonitor* monitor) { if (is_interesting(monitor)) { const oop obj = monitor->object_peek(); const intptr_t hash = UseObjectMonitorTable ? monitor->hash() : monitor->header().hash(); ResourceMark rm; out->print(INTPTR_FORMAT " %d%d%d " INTPTR_FORMAT " %s", p2i(monitor), monitor->is_busy(), hash != 0, monitor->has_owner(), p2i(obj), obj == nullptr ? "" : obj->klass()->external_name()); if (monitor->is_busy()) { out->print(" (%s)", monitor->is_busy_to_string(&ss)); ss.reset(); } out->cr(); } }); } out->flush(); }