/* * Copyright (c) 1998, 2007, 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. * */ // 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; 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); }; // WARNING: // This is a very sensitive and fragile class. DO NOT make any // change unless you are fully aware of the underlying semantics. // This class can not inherit from any other class, because I have // to let the displaced header be the very first word. Otherwise I // have to let markOop include this file, which would export the // monitor data structure to everywhere. // // The ObjectMonitor class is used to implement JavaMonitors which have // transformed from the lightweight structure of the thread stack to a // heavy weight lock due to contention // It is also used as RawMonitor by the JVMTI 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 }; public: // 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); } static int FreeNext_offset_in_bytes() { return offset_of(ObjectMonitor, FreeNext); } static int WaitSet_offset_in_bytes() { return offset_of(ObjectMonitor, _WaitSet) ; } static int Responsible_offset_in_bytes() { return offset_of(ObjectMonitor, _Responsible);} static int Spinner_offset_in_bytes() { return offset_of(ObjectMonitor, _Spinner); } public: // Eventaully we'll make provisions for multiple callbacks, but // now one will suffice. static int (*SpinCallbackFunction)(intptr_t, int) ; static intptr_t SpinCallbackArgument ; public: markOop header() const; 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); intptr_t waiters() const; intptr_t count() const; void set_count(intptr_t count); intptr_t contentions() const ; intptr_t recursions() const { return _recursions; } // JVM/DI GetMonitorInfo() needs this ObjectWaiter* first_waiter() { return _WaitSet; } ObjectWaiter* next_waiter(ObjectWaiter* o) { return o->_next; } Thread* thread_of_waiter(ObjectWaiter* o) { return o->_thread; } // initialize the monitor, exception the semaphore, all other fields // are simple integers or pointers ObjectMonitor() { _header = NULL; _count = 0; _waiters = 0, _recursions = 0; _object = NULL; _owner = NULL; _WaitSet = NULL; _WaitSetLock = 0 ; _Responsible = NULL ; _succ = NULL ; _cxq = NULL ; FreeNext = NULL ; _EntryList = NULL ; _SpinFreq = 0 ; _SpinClock = 0 ; OwnerIsThread = 0 ; } ~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 // TODO: assert (is_busy()|_recursions) == 0 _succ = NULL ; _EntryList = NULL ; _cxq = NULL ; _WaitSet = NULL ; _recursions = 0 ; _SpinFreq = 0 ; _SpinClock = 0 ; OwnerIsThread = 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(); #ifndef PRODUCT void verify(); void print(); #endif bool try_enter (TRAPS) ; void enter(TRAPS); void exit(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(); 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_Fixed (Thread * Self) ; int TrySpin_VaryFrequency (Thread * Self) ; int TrySpin_VaryDuration (Thread * Self) ; void ctAsserts () ; void ExitEpilog (Thread * Self, ObjectWaiter * Wakee) ; bool ExitSuspendEquivalent (JavaThread * Self) ; private: friend class ObjectSynchronizer; friend class ObjectWaiter; friend class VMStructs; // WARNING: this must be the very first word of ObjectMonitor // This means this class can't use any virtual member functions. // TODO-FIXME: assert that offsetof(_header) is 0 or get rid of the // implicit 0 offset in emitted code. volatile markOop _header; // displaced object header word - mark void* volatile _object; // backward object pointer - strong root double SharingPad [1] ; // temp to reduce false sharing // All the following fields must be machine word aligned // The VM assumes write ordering wrt these fields, which can be // read from other threads. protected: // protected for jvmtiRawMonitor void * volatile _owner; // pointer to owning thread OR BasicLock volatile intptr_t _recursions; // recursion count, 0 for first entry private: int OwnerIsThread ; // _owner is (Thread *) vs SP/BasicLock ObjectWaiter * volatile _cxq ; // LL of recently-arrived threads blocked on entry. // The list is actually composed of WaitNodes, acting // as proxies for Threads. protected: ObjectWaiter * volatile _EntryList ; // Threads blocked on entry or reentry. private: Thread * volatile _succ ; // Heir presumptive thread - used for futile wakeup throttling Thread * volatile _Responsible ; int _PromptDrain ; // rqst to drain cxq into EntryList ASAP volatile int _Spinner ; // for exit->spinner handoff optimization volatile int _SpinFreq ; // Spin 1-out-of-N attempts: success rate volatile int _SpinClock ; volatile int _SpinDuration ; volatile intptr_t _SpinState ; // MCS/CLH list of spinners // TODO-FIXME: _count, _waiters and _recursions should be of // type int, or int32_t but not intptr_t. There's no reason // to use 64-bit fields for these variables on a 64-bit JVM. volatile intptr_t _count; // reference count to prevent reclaimation/deflation // at stop-the-world time. See deflate_idle_monitors(). // _count is approximately |_WaitSet| + |_EntryList| protected: volatile intptr_t _waiters; // number of waiting threads private: protected: ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor private: volatile int _WaitSetLock; // protects Wait Queue - simple spinlock public: int _QMix ; // Mixed prepend queue discipline ObjectMonitor * FreeNext ; // Free list linkage intptr_t StatA, StatsB ; public: static void Initialize () ; static PerfCounter * _sync_ContendedLockAttempts ; static PerfCounter * _sync_FutileWakeups ; static PerfCounter * _sync_Parks ; static PerfCounter * _sync_EmptyNotifications ; static PerfCounter * _sync_Notifications ; static PerfCounter * _sync_SlowEnter ; static PerfCounter * _sync_SlowExit ; static PerfCounter * _sync_SlowNotify ; static PerfCounter * _sync_SlowNotifyAll ; static PerfCounter * _sync_FailedSpins ; static PerfCounter * _sync_SuccessfulSpins ; static PerfCounter * _sync_PrivateA ; static PerfCounter * _sync_PrivateB ; static PerfCounter * _sync_MonInCirculation ; static PerfCounter * _sync_MonScavenged ; static PerfCounter * _sync_Inflations ; static PerfCounter * _sync_Deflations ; static PerfLongVariable * _sync_MonExtant ; public: static int Knob_Verbose; static int Knob_SpinLimit; }; #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) { ::printf (#nom " : %d \n", v); ::fflush(stdout); }} #undef TEVENT #define TEVENT(nom) {;}