| /* |
| * Copyright (c) 1998, 2018, 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. |
| * |
| */ |
| |
| #ifndef SHARE_VM_RUNTIME_OBJECTMONITOR_HPP |
| #define SHARE_VM_RUNTIME_OBJECTMONITOR_HPP |
| |
| #include "memory/allocation.hpp" |
| #include "memory/padded.hpp" |
| #include "oops/markOop.hpp" |
| #include "runtime/os.hpp" |
| #include "runtime/park.hpp" |
| #include "runtime/perfData.hpp" |
| |
| class ObjectMonitor; |
| |
| // ObjectWaiter serves as a "proxy" or surrogate thread. |
| // TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific |
| // ParkEvent instead. Beware, however, that the JVMTI code |
| // knows about ObjectWaiters, so we'll have to reconcile that code. |
| // See next_waiter(), first_waiter(), etc. |
| |
| class ObjectWaiter : public StackObj { |
| public: |
| enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ }; |
| enum Sorted { PREPEND, APPEND, SORTED }; |
| ObjectWaiter * volatile _next; |
| ObjectWaiter * volatile _prev; |
| Thread* _thread; |
| jlong _notifier_tid; |
| ParkEvent * _event; |
| volatile int _notified; |
| volatile TStates TState; |
| Sorted _Sorted; // List placement disposition |
| bool _active; // Contention monitoring is enabled |
| public: |
| ObjectWaiter(Thread* thread); |
| |
| void wait_reenter_begin(ObjectMonitor *mon); |
| void wait_reenter_end(ObjectMonitor *mon); |
| }; |
| |
| // The ObjectMonitor class implements the heavyweight version of a |
| // JavaMonitor. The lightweight BasicLock/stack lock version has been |
| // inflated into an ObjectMonitor. This inflation is typically due to |
| // contention or use of Object.wait(). |
| // |
| // WARNING: This is a very sensitive and fragile class. DO NOT make any |
| // changes unless you are fully aware of the underlying semantics. |
| // |
| // Class JvmtiRawMonitor currently inherits from ObjectMonitor so |
| // changes in this class must be careful to not break JvmtiRawMonitor. |
| // These two subsystems should be separated. |
| // |
| // ObjectMonitor Layout Overview/Highlights/Restrictions: |
| // |
| // - The _header field must be at offset 0 because the displaced header |
| // from markOop is stored there. We do not want markOop.hpp to include |
| // ObjectMonitor.hpp to avoid exposing ObjectMonitor everywhere. This |
| // means that ObjectMonitor cannot inherit from any other class nor can |
| // it use any virtual member functions. This restriction is critical to |
| // the proper functioning of the VM. |
| // - The _header and _owner fields should be separated by enough space |
| // to avoid false sharing due to parallel access by different threads. |
| // This is an advisory recommendation. |
| // - The general layout of the fields in ObjectMonitor is: |
| // _header |
| // <lightly_used_fields> |
| // <optional padding> |
| // _owner |
| // <remaining_fields> |
| // - The VM assumes write ordering and machine word alignment with |
| // respect to the _owner field and the <remaining_fields> that can |
| // be read in parallel by other threads. |
| // - Generally fields that are accessed closely together in time should |
| // be placed proximally in space to promote data cache locality. That |
| // is, temporal locality should condition spatial locality. |
| // - We have to balance avoiding false sharing with excessive invalidation |
| // from coherence traffic. As such, we try to cluster fields that tend |
| // to be _written_ at approximately the same time onto the same data |
| // cache line. |
| // - We also have to balance the natural tension between minimizing |
| // single threaded capacity misses with excessive multi-threaded |
| // coherency misses. There is no single optimal layout for both |
| // single-threaded and multi-threaded environments. |
| // |
| // - See ObjectMonitor::sanity_checks() for how critical restrictions are |
| // enforced and advisory recommendations are reported. |
| // - Adjacent ObjectMonitors should be separated by enough space to avoid |
| // false sharing. This is handled by the ObjectMonitor allocation code |
| // in synchronizer.cpp. Also see ObjectSynchronizer::sanity_checks(). |
| // |
| // Futures notes: |
| // - Separating _owner from the <remaining_fields> by enough space to |
| // avoid false sharing might be profitable. Given |
| // http://blogs.oracle.com/dave/entry/cas_and_cache_trivia_invalidate |
| // we know that the CAS in monitorenter will invalidate the line |
| // underlying _owner. We want to avoid an L1 data cache miss on that |
| // same line for monitorexit. Putting these <remaining_fields>: |
| // _recursions, _EntryList, _cxq, and _succ, all of which may be |
| // fetched in the inflated unlock path, on a different cache line |
| // would make them immune to CAS-based invalidation from the _owner |
| // field. |
| // |
| // - The _recursions field should be of type int, or int32_t but not |
| // intptr_t. There's no reason to use a 64-bit type for this field |
| // in a 64-bit JVM. |
| |
| class ObjectMonitor { |
| public: |
| enum { |
| OM_OK, // no error |
| OM_SYSTEM_ERROR, // operating system error |
| OM_ILLEGAL_MONITOR_STATE, // IllegalMonitorStateException |
| OM_INTERRUPTED, // Thread.interrupt() |
| OM_TIMED_OUT // Object.wait() timed out |
| }; |
| |
| private: |
| friend class ObjectSynchronizer; |
| friend class ObjectWaiter; |
| friend class VMStructs; |
| |
| volatile markOop _header; // displaced object header word - mark |
| void* volatile _object; // backward object pointer - strong root |
| public: |
| ObjectMonitor* FreeNext; // Free list linkage |
| private: |
| DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, |
| sizeof(volatile markOop) + sizeof(void * volatile) + |
| sizeof(ObjectMonitor *)); |
| protected: // protected for JvmtiRawMonitor |
| void * volatile _owner; // pointer to owning thread OR BasicLock |
| volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor |
| volatile intptr_t _recursions; // recursion count, 0 for first entry |
| ObjectWaiter * volatile _EntryList; // Threads blocked on entry or reentry. |
| // The list is actually composed of WaitNodes, |
| // acting as proxies for Threads. |
| private: |
| ObjectWaiter * volatile _cxq; // LL of recently-arrived threads blocked on entry. |
| Thread * volatile _succ; // Heir presumptive thread - used for futile wakeup throttling |
| Thread * volatile _Responsible; |
| |
| volatile int _Spinner; // for exit->spinner handoff optimization |
| volatile int _SpinDuration; |
| |
| volatile jint _count; // reference count to prevent reclamation/deflation |
| // at stop-the-world time. See deflate_idle_monitors(). |
| // _count is approximately |_WaitSet| + |_EntryList| |
| protected: |
| ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor |
| volatile jint _waiters; // number of waiting threads |
| private: |
| volatile int _WaitSetLock; // protects Wait Queue - simple spinlock |
| |
| public: |
| static void Initialize(); |
| |
| // Only perform a PerfData operation if the PerfData object has been |
| // allocated and if the PerfDataManager has not freed the PerfData |
| // objects which can happen at normal VM shutdown. |
| // |
| #define OM_PERFDATA_OP(f, op_str) \ |
| do { \ |
| if (ObjectMonitor::_sync_ ## f != NULL && \ |
| PerfDataManager::has_PerfData()) { \ |
| ObjectMonitor::_sync_ ## f->op_str; \ |
| } \ |
| } while (0) |
| |
| static PerfCounter * _sync_ContendedLockAttempts; |
| static PerfCounter * _sync_FutileWakeups; |
| static PerfCounter * _sync_Parks; |
| static PerfCounter * _sync_Notifications; |
| static PerfCounter * _sync_Inflations; |
| static PerfCounter * _sync_Deflations; |
| static PerfLongVariable * _sync_MonExtant; |
| |
| static int Knob_ExitRelease; |
| static int Knob_InlineNotify; |
| static int Knob_Verbose; |
| static int Knob_VerifyInUse; |
| static int Knob_VerifyMatch; |
| static int Knob_SpinLimit; |
| |
| void* operator new (size_t size) throw(); |
| void* operator new[] (size_t size) throw(); |
| void operator delete(void* p); |
| void operator delete[] (void *p); |
| |
| // TODO-FIXME: the "offset" routines should return a type of off_t instead of int ... |
| // ByteSize would also be an appropriate type. |
| static int header_offset_in_bytes() { return offset_of(ObjectMonitor, _header); } |
| static int object_offset_in_bytes() { return offset_of(ObjectMonitor, _object); } |
| static int owner_offset_in_bytes() { return offset_of(ObjectMonitor, _owner); } |
| static int count_offset_in_bytes() { return offset_of(ObjectMonitor, _count); } |
| static int recursions_offset_in_bytes() { return offset_of(ObjectMonitor, _recursions); } |
| static int cxq_offset_in_bytes() { return offset_of(ObjectMonitor, _cxq); } |
| static int succ_offset_in_bytes() { return offset_of(ObjectMonitor, _succ); } |
| static int EntryList_offset_in_bytes() { return offset_of(ObjectMonitor, _EntryList); } |
| |
| // ObjectMonitor references can be ORed with markOop::monitor_value |
| // as part of the ObjectMonitor tagging mechanism. When we combine an |
| // ObjectMonitor reference with an offset, we need to remove the tag |
| // value in order to generate the proper address. |
| // |
| // We can either adjust the ObjectMonitor reference and then add the |
| // offset or we can adjust the offset that is added to the ObjectMonitor |
| // reference. The latter avoids an AGI (Address Generation Interlock) |
| // stall so the helper macro adjusts the offset value that is returned |
| // to the ObjectMonitor reference manipulation code: |
| // |
| #define OM_OFFSET_NO_MONITOR_VALUE_TAG(f) \ |
| ((ObjectMonitor::f ## _offset_in_bytes()) - markOop::monitor_value) |
| |
| markOop header() const; |
| volatile markOop* header_addr(); |
| void set_header(markOop hdr); |
| |
| intptr_t is_busy() const { |
| // TODO-FIXME: merge _count and _waiters. |
| // TODO-FIXME: assert _owner == null implies _recursions = 0 |
| // TODO-FIXME: assert _WaitSet != null implies _count > 0 |
| return _count|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList); |
| } |
| |
| intptr_t is_entered(Thread* current) const; |
| |
| void* owner() const; |
| void set_owner(void* owner); |
| |
| jint waiters() const; |
| |
| jint count() const; |
| void set_count(jint count); |
| jint contentions() const; |
| intptr_t recursions() const { return _recursions; } |
| |
| // JVM/TI GetObjectMonitorUsage() needs this: |
| ObjectWaiter* first_waiter() { return _WaitSet; } |
| ObjectWaiter* next_waiter(ObjectWaiter* o) { return o->_next; } |
| Thread* thread_of_waiter(ObjectWaiter* o) { return o->_thread; } |
| |
| protected: |
| // We don't typically expect or want the ctors or dtors to run. |
| // normal ObjectMonitors are type-stable and immortal. |
| ObjectMonitor() { ::memset((void *)this, 0, sizeof(*this)); } |
| |
| ~ObjectMonitor() { |
| // TODO: Add asserts ... |
| // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0 |
| // _count == 0 _EntryList == NULL etc |
| } |
| |
| private: |
| void Recycle() { |
| // TODO: add stronger asserts ... |
| // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0 |
| // _count == 0 EntryList == NULL |
| // _recursions == 0 _WaitSet == NULL |
| assert(((is_busy()|_recursions) == 0), "freeing inuse monitor"); |
| _succ = NULL; |
| _EntryList = NULL; |
| _cxq = NULL; |
| _WaitSet = NULL; |
| _recursions = 0; |
| } |
| |
| public: |
| |
| void* object() const; |
| void* object_addr(); |
| void set_object(void* obj); |
| |
| bool check(TRAPS); // true if the thread owns the monitor. |
| void check_slow(TRAPS); |
| void clear(); |
| static void sanity_checks(); // public for -XX:+ExecuteInternalVMTests |
| // in PRODUCT for -XX:SyncKnobs=Verbose=1 |
| |
| void enter(TRAPS); |
| void exit(bool not_suspended, TRAPS); |
| void wait(jlong millis, bool interruptable, TRAPS); |
| void notify(TRAPS); |
| void notifyAll(TRAPS); |
| |
| // Use the following at your own risk |
| intptr_t complete_exit(TRAPS); |
| void reenter(intptr_t recursions, TRAPS); |
| |
| private: |
| void AddWaiter(ObjectWaiter * waiter); |
| static void DeferredInitialize(); |
| void INotify(Thread * Self); |
| ObjectWaiter * DequeueWaiter(); |
| void DequeueSpecificWaiter(ObjectWaiter * waiter); |
| void EnterI(TRAPS); |
| void ReenterI(Thread * Self, ObjectWaiter * SelfNode); |
| void UnlinkAfterAcquire(Thread * Self, ObjectWaiter * SelfNode); |
| int TryLock(Thread * Self); |
| int NotRunnable(Thread * Self, Thread * Owner); |
| int TrySpin(Thread * Self); |
| void ExitEpilog(Thread * Self, ObjectWaiter * Wakee); |
| bool ExitSuspendEquivalent(JavaThread * Self); |
| }; |
| |
| #undef TEVENT |
| #define TEVENT(nom) { if (SyncVerbose) FEVENT(nom); } |
| |
| #define FEVENT(nom) \ |
| { \ |
| static volatile int ctr = 0; \ |
| int v = ++ctr; \ |
| if ((v & (v - 1)) == 0) { \ |
| tty->print_cr("INFO: " #nom " : %d", v); \ |
| tty->flush(); \ |
| } \ |
| } |
| |
| #undef TEVENT |
| #define TEVENT(nom) {;} |
| |
| |
| #endif // SHARE_VM_RUNTIME_OBJECTMONITOR_HPP |
