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src/share/vm/runtime/objectMonitor.hpp@fa83ab460c54 (annotated)

src/share/vm/runtime/objectMonitor.hpp

Fri, 22 Oct 2010 15:59:34 -0400

author

acorn

date

Fri, 22 Oct 2010 15:59:34 -0400

changeset 2233

fa83ab460c54

parent 1907

c18cbe5936b8

child 2314

f95d63e2154a

permissions

-rw-r--r--

6988353: refactor contended sync subsystem
Summary: reduce complexity by factoring synchronizer.cpp
Reviewed-by: dholmes, never, coleenp

duke@435	1	/*
trims@1907	2	* Copyright (c) 1998, 2007, Oracle and/or its affiliates. All rights reserved.
duke@435	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435	4	*
duke@435	5	* This code is free software; you can redistribute it and/or modify it
duke@435	6	* under the terms of the GNU General Public License version 2 only, as
duke@435	7	* published by the Free Software Foundation.
duke@435	8	*
duke@435	9	* This code is distributed in the hope that it will be useful, but WITHOUT
duke@435	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435	12	* version 2 for more details (a copy is included in the LICENSE file that
duke@435	13	* accompanied this code).
duke@435	14	*
duke@435	15	* You should have received a copy of the GNU General Public License version
duke@435	16	* 2 along with this work; if not, write to the Free Software Foundation,
duke@435	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435	18	*
trims@1907	19	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907	20	* or visit www.oracle.com if you need additional information or have any
trims@1907	21	* questions.
duke@435	22	*
duke@435	23	*/
duke@435	24
acorn@2233	25
acorn@2233	26	// ObjectWaiter serves as a "proxy" or surrogate thread.
acorn@2233	27	// TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific
acorn@2233	28	// ParkEvent instead. Beware, however, that the JVMTI code
acorn@2233	29	// knows about ObjectWaiters, so we'll have to reconcile that code.
acorn@2233	30	// See next_waiter(), first_waiter(), etc.
acorn@2233	31
acorn@2233	32	class ObjectWaiter : public StackObj {
acorn@2233	33	public:
acorn@2233	34	enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ } ;
acorn@2233	35	enum Sorted { PREPEND, APPEND, SORTED } ;
acorn@2233	36	ObjectWaiter * volatile _next;
acorn@2233	37	ObjectWaiter * volatile _prev;
acorn@2233	38	Thread* _thread;
acorn@2233	39	ParkEvent * _event;
acorn@2233	40	volatile int _notified ;
acorn@2233	41	volatile TStates TState ;
acorn@2233	42	Sorted _Sorted ; // List placement disposition
acorn@2233	43	bool _active ; // Contention monitoring is enabled
acorn@2233	44	public:
acorn@2233	45	ObjectWaiter(Thread* thread);
acorn@2233	46
acorn@2233	47	void wait_reenter_begin(ObjectMonitor *mon);
acorn@2233	48	void wait_reenter_end(ObjectMonitor *mon);
acorn@2233	49	};
acorn@2233	50
duke@435	51	// WARNING:
duke@435	52	// This is a very sensitive and fragile class. DO NOT make any
duke@435	53	// change unless you are fully aware of the underlying semantics.
duke@435	54
duke@435	55	// This class can not inherit from any other class, because I have
duke@435	56	// to let the displaced header be the very first word. Otherwise I
duke@435	57	// have to let markOop include this file, which would export the
duke@435	58	// monitor data structure to everywhere.
duke@435	59	//
duke@435	60	// The ObjectMonitor class is used to implement JavaMonitors which have
duke@435	61	// transformed from the lightweight structure of the thread stack to a
duke@435	62	// heavy weight lock due to contention
duke@435	63
duke@435	64	// It is also used as RawMonitor by the JVMTI
duke@435	65
duke@435	66
duke@435	67	class ObjectMonitor {
duke@435	68	public:
duke@435	69	enum {
duke@435	70	OM_OK, // no error
duke@435	71	OM_SYSTEM_ERROR, // operating system error
duke@435	72	OM_ILLEGAL_MONITOR_STATE, // IllegalMonitorStateException
duke@435	73	OM_INTERRUPTED, // Thread.interrupt()
duke@435	74	OM_TIMED_OUT // Object.wait() timed out
duke@435	75	};
duke@435	76
duke@435	77	public:
duke@435	78	// TODO-FIXME: the "offset" routines should return a type of off_t instead of int ...
duke@435	79	// ByteSize would also be an appropriate type.
duke@435	80	static int header_offset_in_bytes() { return offset_of(ObjectMonitor, _header); }
duke@435	81	static int object_offset_in_bytes() { return offset_of(ObjectMonitor, _object); }
duke@435	82	static int owner_offset_in_bytes() { return offset_of(ObjectMonitor, _owner); }
duke@435	83	static int count_offset_in_bytes() { return offset_of(ObjectMonitor, _count); }
duke@435	84	static int recursions_offset_in_bytes() { return offset_of(ObjectMonitor, _recursions); }
duke@435	85	static int cxq_offset_in_bytes() { return offset_of(ObjectMonitor, _cxq) ; }
duke@435	86	static int succ_offset_in_bytes() { return offset_of(ObjectMonitor, _succ) ; }
duke@435	87	static int EntryList_offset_in_bytes() { return offset_of(ObjectMonitor, _EntryList); }
duke@435	88	static int FreeNext_offset_in_bytes() { return offset_of(ObjectMonitor, FreeNext); }
duke@435	89	static int WaitSet_offset_in_bytes() { return offset_of(ObjectMonitor, _WaitSet) ; }
duke@435	90	static int Responsible_offset_in_bytes() { return offset_of(ObjectMonitor, _Responsible);}
duke@435	91	static int Spinner_offset_in_bytes() { return offset_of(ObjectMonitor, _Spinner); }
duke@435	92
duke@435	93	public:
duke@435	94	// Eventaully we'll make provisions for multiple callbacks, but
duke@435	95	// now one will suffice.
duke@435	96	static int (*SpinCallbackFunction)(intptr_t, int) ;
duke@435	97	static intptr_t SpinCallbackArgument ;
duke@435	98
duke@435	99
duke@435	100	public:
duke@435	101	markOop header() const;
duke@435	102	void set_header(markOop hdr);
duke@435	103
acorn@2233	104	intptr_t is_busy() const {
acorn@2233	105	// TODO-FIXME: merge _count and _waiters.
acorn@2233	106	// TODO-FIXME: assert _owner == null implies _recursions = 0
acorn@2233	107	// TODO-FIXME: assert _WaitSet != null implies _count > 0
acorn@2233	108	return _count|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList ) ;
acorn@2233	109	}
acorn@2233	110
duke@435	111	intptr_t is_entered(Thread* current) const;
duke@435	112
duke@435	113	void* owner() const;
duke@435	114	void set_owner(void* owner);
duke@435	115
duke@435	116	intptr_t waiters() const;
duke@435	117
duke@435	118	intptr_t count() const;
duke@435	119	void set_count(intptr_t count);
duke@435	120	intptr_t contentions() const ;
acorn@2233	121	intptr_t recursions() const { return _recursions; }
duke@435	122
duke@435	123	// JVM/DI GetMonitorInfo() needs this
acorn@2233	124	ObjectWaiter* first_waiter() { return _WaitSet; }
acorn@2233	125	ObjectWaiter* next_waiter(ObjectWaiter* o) { return o->_next; }
acorn@2233	126	Thread* thread_of_waiter(ObjectWaiter* o) { return o->_thread; }
duke@435	127
acorn@2233	128	// initialize the monitor, exception the semaphore, all other fields
acorn@2233	129	// are simple integers or pointers
acorn@2233	130	ObjectMonitor() {
acorn@2233	131	_header = NULL;
acorn@2233	132	_count = 0;
acorn@2233	133	_waiters = 0,
acorn@2233	134	_recursions = 0;
acorn@2233	135	_object = NULL;
acorn@2233	136	_owner = NULL;
acorn@2233	137	_WaitSet = NULL;
acorn@2233	138	_WaitSetLock = 0 ;
acorn@2233	139	_Responsible = NULL ;
acorn@2233	140	_succ = NULL ;
acorn@2233	141	_cxq = NULL ;
acorn@2233	142	FreeNext = NULL ;
acorn@2233	143	_EntryList = NULL ;
acorn@2233	144	_SpinFreq = 0 ;
acorn@2233	145	_SpinClock = 0 ;
acorn@2233	146	OwnerIsThread = 0 ;
acorn@2233	147	}
acorn@2233	148
acorn@2233	149	~ObjectMonitor() {
acorn@2233	150	// TODO: Add asserts ...
acorn@2233	151	// _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
acorn@2233	152	// _count == 0 _EntryList == NULL etc
acorn@2233	153	}
acorn@2233	154
acorn@2233	155	private:
acorn@2233	156	void Recycle () {
acorn@2233	157	// TODO: add stronger asserts ...
acorn@2233	158	// _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
acorn@2233	159	// _count == 0 EntryList == NULL
acorn@2233	160	// _recursions == 0 _WaitSet == NULL
acorn@2233	161	// TODO: assert (is_busy()|_recursions) == 0
acorn@2233	162	_succ = NULL ;
acorn@2233	163	_EntryList = NULL ;
acorn@2233	164	_cxq = NULL ;
acorn@2233	165	_WaitSet = NULL ;
acorn@2233	166	_recursions = 0 ;
acorn@2233	167	_SpinFreq = 0 ;
acorn@2233	168	_SpinClock = 0 ;
acorn@2233	169	OwnerIsThread = 0 ;
acorn@2233	170	}
acorn@2233	171
acorn@2233	172	public:
duke@435	173
duke@435	174	void* object() const;
duke@435	175	void* object_addr();
duke@435	176	void set_object(void* obj);
duke@435	177
duke@435	178	bool check(TRAPS); // true if the thread owns the monitor.
duke@435	179	void check_slow(TRAPS);
duke@435	180	void clear();
duke@435	181	#ifndef PRODUCT
duke@435	182	void verify();
duke@435	183	void print();
duke@435	184	#endif
duke@435	185
duke@435	186	bool try_enter (TRAPS) ;
duke@435	187	void enter(TRAPS);
duke@435	188	void exit(TRAPS);
duke@435	189	void wait(jlong millis, bool interruptable, TRAPS);
duke@435	190	void notify(TRAPS);
duke@435	191	void notifyAll(TRAPS);
duke@435	192
duke@435	193	// Use the following at your own risk
duke@435	194	intptr_t complete_exit(TRAPS);
duke@435	195	void reenter(intptr_t recursions, TRAPS);
duke@435	196
duke@435	197	private:
duke@435	198	void AddWaiter (ObjectWaiter * waiter) ;
acorn@2233	199	static void DeferredInitialize();
duke@435	200
duke@435	201	ObjectWaiter * DequeueWaiter () ;
duke@435	202	void DequeueSpecificWaiter (ObjectWaiter * waiter) ;
duke@435	203	void EnterI (TRAPS) ;
duke@435	204	void ReenterI (Thread * Self, ObjectWaiter * SelfNode) ;
duke@435	205	void UnlinkAfterAcquire (Thread * Self, ObjectWaiter * SelfNode) ;
duke@435	206	int TryLock (Thread * Self) ;
duke@435	207	int NotRunnable (Thread * Self, Thread * Owner) ;
duke@435	208	int TrySpin_Fixed (Thread * Self) ;
duke@435	209	int TrySpin_VaryFrequency (Thread * Self) ;
duke@435	210	int TrySpin_VaryDuration (Thread * Self) ;
duke@435	211	void ctAsserts () ;
duke@435	212	void ExitEpilog (Thread * Self, ObjectWaiter * Wakee) ;
duke@435	213	bool ExitSuspendEquivalent (JavaThread * Self) ;
duke@435	214
duke@435	215	private:
duke@435	216	friend class ObjectSynchronizer;
duke@435	217	friend class ObjectWaiter;
duke@435	218	friend class VMStructs;
duke@435	219
duke@435	220	// WARNING: this must be the very first word of ObjectMonitor
duke@435	221	// This means this class can't use any virtual member functions.
duke@435	222	// TODO-FIXME: assert that offsetof(_header) is 0 or get rid of the
duke@435	223	// implicit 0 offset in emitted code.
duke@435	224
duke@435	225	volatile markOop _header; // displaced object header word - mark
duke@435	226	void* volatile _object; // backward object pointer - strong root
duke@435	227
duke@435	228	double SharingPad [1] ; // temp to reduce false sharing
duke@435	229
duke@435	230	// All the following fields must be machine word aligned
duke@435	231	// The VM assumes write ordering wrt these fields, which can be
duke@435	232	// read from other threads.
duke@435	233
acorn@2233	234	protected: // protected for jvmtiRawMonitor
duke@435	235	void * volatile _owner; // pointer to owning thread OR BasicLock
duke@435	236	volatile intptr_t _recursions; // recursion count, 0 for first entry
acorn@2233	237	private:
duke@435	238	int OwnerIsThread ; // _owner is (Thread *) vs SP/BasicLock
duke@435	239	ObjectWaiter * volatile _cxq ; // LL of recently-arrived threads blocked on entry.
duke@435	240	// The list is actually composed of WaitNodes, acting
duke@435	241	// as proxies for Threads.
acorn@2233	242	protected:
duke@435	243	ObjectWaiter * volatile _EntryList ; // Threads blocked on entry or reentry.
acorn@2233	244	private:
duke@435	245	Thread * volatile _succ ; // Heir presumptive thread - used for futile wakeup throttling
duke@435	246	Thread * volatile _Responsible ;
duke@435	247	int _PromptDrain ; // rqst to drain cxq into EntryList ASAP
duke@435	248
duke@435	249	volatile int _Spinner ; // for exit->spinner handoff optimization
duke@435	250	volatile int _SpinFreq ; // Spin 1-out-of-N attempts: success rate
duke@435	251	volatile int _SpinClock ;
duke@435	252	volatile int _SpinDuration ;
duke@435	253	volatile intptr_t _SpinState ; // MCS/CLH list of spinners
duke@435	254
duke@435	255	// TODO-FIXME: _count, _waiters and _recursions should be of
duke@435	256	// type int, or int32_t but not intptr_t. There's no reason
duke@435	257	// to use 64-bit fields for these variables on a 64-bit JVM.
duke@435	258
duke@435	259	volatile intptr_t _count; // reference count to prevent reclaimation/deflation
duke@435	260	// at stop-the-world time. See deflate_idle_monitors().
duke@435	261	// _count is approximately |_WaitSet| + |_EntryList|
acorn@2233	262	protected:
duke@435	263	volatile intptr_t _waiters; // number of waiting threads
acorn@2233	264	private:
acorn@2233	265	protected:
duke@435	266	ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor
acorn@2233	267	private:
duke@435	268	volatile int _WaitSetLock; // protects Wait Queue - simple spinlock
duke@435	269
duke@435	270	public:
duke@435	271	int _QMix ; // Mixed prepend queue discipline
duke@435	272	ObjectMonitor * FreeNext ; // Free list linkage
duke@435	273	intptr_t StatA, StatsB ;
duke@435	274
acorn@2233	275	public:
acorn@2233	276	static void Initialize () ;
acorn@2233	277	static PerfCounter * _sync_ContendedLockAttempts ;
acorn@2233	278	static PerfCounter * _sync_FutileWakeups ;
acorn@2233	279	static PerfCounter * _sync_Parks ;
acorn@2233	280	static PerfCounter * _sync_EmptyNotifications ;
acorn@2233	281	static PerfCounter * _sync_Notifications ;
acorn@2233	282	static PerfCounter * _sync_SlowEnter ;
acorn@2233	283	static PerfCounter * _sync_SlowExit ;
acorn@2233	284	static PerfCounter * _sync_SlowNotify ;
acorn@2233	285	static PerfCounter * _sync_SlowNotifyAll ;
acorn@2233	286	static PerfCounter * _sync_FailedSpins ;
acorn@2233	287	static PerfCounter * _sync_SuccessfulSpins ;
acorn@2233	288	static PerfCounter * _sync_PrivateA ;
acorn@2233	289	static PerfCounter * _sync_PrivateB ;
acorn@2233	290	static PerfCounter * _sync_MonInCirculation ;
acorn@2233	291	static PerfCounter * _sync_MonScavenged ;
acorn@2233	292	static PerfCounter * _sync_Inflations ;
acorn@2233	293	static PerfCounter * _sync_Deflations ;
acorn@2233	294	static PerfLongVariable * _sync_MonExtant ;
acorn@2233	295
acorn@2233	296	public:
acorn@2233	297	static int Knob_Verbose;
acorn@2233	298	static int Knob_SpinLimit;
duke@435	299	};
acorn@2233	300
acorn@2233	301	#undef TEVENT
acorn@2233	302	#define TEVENT(nom) {if (SyncVerbose) FEVENT(nom); }
acorn@2233	303
acorn@2233	304	#define FEVENT(nom) { static volatile int ctr = 0 ; int v = ++ctr ; if ((v & (v-1)) == 0) { ::printf (#nom " : %d \n", v); ::fflush(stdout); }}
acorn@2233	305
acorn@2233	306	#undef TEVENT
acorn@2233	307	#define TEVENT(nom) {;}
acorn@2233	308