Mercurial > hg > graal-jvmci-8
annotate src/share/vm/runtime/mutex.hpp @ 377:ddfad9496151
Merge
author | tonyp |
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date | Wed, 01 Oct 2008 15:05:06 -0400 |
parents | d1605aabd0a1 |
children | 98cb887364d3 |
rev | line source |
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0 | 1 /* |
196 | 2 * Copyright 1998-2008 Sun Microsystems, Inc. All Rights Reserved. |
0 | 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 * | |
5 * This code is free software; you can redistribute it and/or modify it | |
6 * under the terms of the GNU General Public License version 2 only, as | |
7 * published by the Free Software Foundation. | |
8 * | |
9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
12 * version 2 for more details (a copy is included in the LICENSE file that | |
13 * accompanied this code). | |
14 * | |
15 * You should have received a copy of the GNU General Public License version | |
16 * 2 along with this work; if not, write to the Free Software Foundation, | |
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
18 * | |
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
22 * | |
23 */ | |
24 | |
25 // The SplitWord construct allows us to colocate the contention queue | |
26 // (cxq) with the lock-byte. The queue elements are ParkEvents, which are | |
27 // always aligned on 256-byte addresses - the least significant byte of | |
28 // a ParkEvent is always 0. Colocating the lock-byte with the queue | |
29 // allows us to easily avoid what would otherwise be a race in lock() | |
30 // if we were to use two completely separate fields for the contention queue | |
31 // and the lock indicator. Specifically, colocation renders us immune | |
32 // from the race where a thread might enqueue itself in the lock() slow-path | |
33 // immediately after the lock holder drops the outer lock in the unlock() | |
34 // fast-path. | |
35 // | |
36 // Colocation allows us to use a fast-path unlock() form that uses | |
37 // A MEMBAR instead of a CAS. MEMBAR has lower local latency than CAS | |
38 // on many platforms. | |
39 // | |
40 // See: | |
41 // + http://blogs.sun.com/dave/entry/biased_locking_in_hotspot | |
42 // + http://blogs.sun.com/dave/resource/synchronization-public2.pdf | |
43 // | |
44 // Note that we're *not* using word-tearing the classic sense. | |
45 // The lock() fast-path will CAS the lockword and the unlock() | |
46 // fast-path will store into the lock-byte colocated within the lockword. | |
47 // We depend on the fact that all our reference platforms have | |
48 // coherent and atomic byte accesses. More precisely, byte stores | |
49 // interoperate in a safe, sane, and expected manner with respect to | |
50 // CAS, ST and LDs to the full-word containing the byte. | |
51 // If you're porting HotSpot to a platform where that isn't the case | |
52 // then you'll want change the unlock() fast path from: | |
53 // STB;MEMBAR #storeload; LDN | |
54 // to a full-word CAS of the lockword. | |
55 | |
56 | |
57 union SplitWord { // full-word with separately addressable LSB | |
58 volatile intptr_t FullWord ; | |
59 volatile void * Address ; | |
60 volatile jbyte Bytes [sizeof(intptr_t)] ; | |
61 } ; | |
62 | |
63 // Endian-ness ... index of least-significant byte in SplitWord.Bytes[] | |
64 #ifdef AMD64 // little | |
65 #define _LSBINDEX 0 | |
66 #else | |
67 #if IA32 // little | |
68 #define _LSBINDEX 0 | |
69 #else | |
70 #ifdef SPARC // big | |
71 #define _LSBINDEX (sizeof(intptr_t)-1) | |
72 #else | |
73 #error "unknown architecture" | |
74 #endif | |
75 #endif | |
76 #endif | |
77 | |
78 class ParkEvent ; | |
79 | |
80 // See orderAccess.hpp. We assume throughout the VM that mutex lock and | |
81 // try_lock do fence-lock-acquire, and that unlock does a release-unlock, | |
82 // *in that order*. If their implementations change such that these | |
83 // assumptions are violated, a whole lot of code will break. | |
84 | |
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85 // The default length of monitor name is choosen to be 64 to avoid false sharing. |
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86 static const int MONITOR_NAME_LEN = 64; |
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87 |
0 | 88 class Monitor : public CHeapObj { |
89 | |
90 public: | |
91 // A special lock: Is a lock where you are guaranteed not to block while you are | |
92 // holding it, i.e., no vm operation can happen, taking other locks, etc. | |
93 // NOTE: It is critical that the rank 'special' be the lowest (earliest) | |
94 // (except for "event"?) for the deadlock dection to work correctly. | |
95 // The rank native is only for use in Mutex's created by JVM_RawMonitorCreate, | |
96 // which being external to the VM are not subject to deadlock detection. | |
97 // The rank safepoint is used only for synchronization in reaching a | |
98 // safepoint and leaving a safepoint. It is only used for the Safepoint_lock | |
99 // currently. While at a safepoint no mutexes of rank safepoint are held | |
100 // by any thread. | |
101 // The rank named "leaf" is probably historical (and should | |
102 // be changed) -- mutexes of this rank aren't really leaf mutexes | |
103 // at all. | |
104 enum lock_types { | |
105 event, | |
106 special, | |
107 suspend_resume, | |
108 leaf = suspend_resume + 2, | |
109 safepoint = leaf + 10, | |
110 barrier = safepoint + 1, | |
111 nonleaf = barrier + 1, | |
112 max_nonleaf = nonleaf + 900, | |
113 native = max_nonleaf + 1 | |
114 }; | |
115 | |
116 // The WaitSet and EntryList linked lists are composed of ParkEvents. | |
117 // I use ParkEvent instead of threads as ParkEvents are immortal and | |
118 // type-stable, meaning we can safely unpark() a possibly stale | |
119 // list element in the unlock()-path. | |
120 | |
121 protected: // Monitor-Mutex metadata | |
122 SplitWord _LockWord ; // Contention queue (cxq) colocated with Lock-byte | |
123 enum LockWordBits { _LBIT=1 } ; | |
124 Thread * volatile _owner; // The owner of the lock | |
125 // Consider sequestering _owner on its own $line | |
126 // to aid future synchronization mechanisms. | |
127 ParkEvent * volatile _EntryList ; // List of threads waiting for entry | |
128 ParkEvent * volatile _OnDeck ; // heir-presumptive | |
129 volatile intptr_t _WaitLock [1] ; // Protects _WaitSet | |
130 ParkEvent * volatile _WaitSet ; // LL of ParkEvents | |
131 volatile bool _snuck; // Used for sneaky locking (evil). | |
132 int NotifyCount ; // diagnostic assist | |
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133 char _name[MONITOR_NAME_LEN]; // Name of mutex |
0 | 134 |
135 // Debugging fields for naming, deadlock detection, etc. (some only used in debug mode) | |
136 #ifndef PRODUCT | |
137 bool _allow_vm_block; | |
138 debug_only(int _rank;) // rank (to avoid/detect potential deadlocks) | |
139 debug_only(Monitor * _next;) // Used by a Thread to link up owned locks | |
140 debug_only(Thread* _last_owner;) // the last thread to own the lock | |
141 debug_only(static bool contains(Monitor * locks, Monitor * lock);) | |
142 debug_only(static Monitor * get_least_ranked_lock(Monitor * locks);) | |
143 debug_only(Monitor * get_least_ranked_lock_besides_this(Monitor * locks);) | |
144 #endif | |
145 | |
146 void set_owner_implementation(Thread* owner) PRODUCT_RETURN; | |
147 void check_prelock_state (Thread* thread) PRODUCT_RETURN; | |
148 void check_block_state (Thread* thread) PRODUCT_RETURN; | |
149 | |
150 // platform-dependent support code can go here (in os_<os_family>.cpp) | |
151 public: | |
152 enum { | |
153 _no_safepoint_check_flag = true, | |
154 _allow_vm_block_flag = true, | |
155 _as_suspend_equivalent_flag = true | |
156 }; | |
157 | |
158 enum WaitResults { | |
159 CONDVAR_EVENT, // Wait returned because of condition variable notification | |
160 INTERRUPT_EVENT, // Wait returned because waiting thread was interrupted | |
161 NUMBER_WAIT_RESULTS | |
162 }; | |
163 | |
164 private: | |
165 int TrySpin (Thread * Self) ; | |
166 int TryLock () ; | |
167 int TryFast () ; | |
168 int AcquireOrPush (ParkEvent * ev) ; | |
169 void IUnlock (bool RelaxAssert) ; | |
170 void ILock (Thread * Self) ; | |
171 int IWait (Thread * Self, jlong timo); | |
172 int ILocked () ; | |
173 | |
174 protected: | |
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175 static void ClearMonitor (Monitor * m, const char* name = NULL) ; |
0 | 176 Monitor() ; |
177 | |
178 public: | |
179 Monitor(int rank, const char *name, bool allow_vm_block=false); | |
180 ~Monitor(); | |
181 | |
182 // Wait until monitor is notified (or times out). | |
183 // Defaults are to make safepoint checks, wait time is forever (i.e., | |
184 // zero), and not a suspend-equivalent condition. Returns true if wait | |
185 // times out; otherwise returns false. | |
186 bool wait(bool no_safepoint_check = !_no_safepoint_check_flag, | |
187 long timeout = 0, | |
188 bool as_suspend_equivalent = !_as_suspend_equivalent_flag); | |
189 bool notify(); | |
190 bool notify_all(); | |
191 | |
192 | |
193 void lock(); // prints out warning if VM thread blocks | |
194 void lock(Thread *thread); // overloaded with current thread | |
195 void unlock(); | |
196 bool is_locked() const { return _owner != NULL; } | |
197 | |
198 bool try_lock(); // Like lock(), but unblocking. It returns false instead | |
199 | |
200 // Lock without safepoint check. Should ONLY be used by safepoint code and other code | |
201 // that is guaranteed not to block while running inside the VM. | |
202 void lock_without_safepoint_check(); | |
203 void lock_without_safepoint_check (Thread * Self) ; | |
204 | |
205 // Current owner - not not MT-safe. Can only be used to guarantee that | |
206 // the current running thread owns the lock | |
207 Thread* owner() const { return _owner; } | |
208 bool owned_by_self() const; | |
209 | |
210 // Support for JVM_RawMonitorEnter & JVM_RawMonitorExit. These can be called by | |
211 // non-Java thread. (We should really have a RawMonitor abstraction) | |
212 void jvm_raw_lock(); | |
213 void jvm_raw_unlock(); | |
214 const char *name() const { return _name; } | |
215 | |
216 void print_on_error(outputStream* st) const; | |
217 | |
218 #ifndef PRODUCT | |
219 void print_on(outputStream* st) const; | |
220 void print() const { print_on(tty); } | |
221 debug_only(int rank() const { return _rank; }) | |
222 bool allow_vm_block() { return _allow_vm_block; } | |
223 | |
224 debug_only(Monitor *next() const { return _next; }) | |
225 debug_only(void set_next(Monitor *next) { _next = next; }) | |
226 #endif | |
227 | |
228 void set_owner(Thread* owner) { | |
229 #ifndef PRODUCT | |
230 set_owner_implementation(owner); | |
231 debug_only(void verify_Monitor(Thread* thr)); | |
232 #else | |
233 _owner = owner; | |
234 #endif | |
235 } | |
236 | |
237 }; | |
238 | |
239 // Normally we'd expect Monitor to extend Mutex in the sense that a monitor | |
240 // constructed from pthreads primitives might extend a mutex by adding | |
241 // a condvar and some extra metadata. In fact this was the case until J2SE7. | |
242 // | |
243 // Currently, however, the base object is a monitor. Monitor contains all the | |
244 // logic for wait(), notify(), etc. Mutex extends monitor and restricts the | |
245 // visiblity of wait(), notify(), and notify_all(). | |
246 // | |
247 // Another viable alternative would have been to have Monitor extend Mutex and | |
248 // implement all the normal mutex and wait()-notify() logic in Mutex base class. | |
249 // The wait()-notify() facility would be exposed via special protected member functions | |
250 // (e.g., _Wait() and _Notify()) in Mutex. Monitor would extend Mutex and expose wait() | |
251 // as a call to _Wait(). That is, the public wait() would be a wrapper for the protected | |
252 // _Wait(). | |
253 // | |
254 // An even better alternative is to simply eliminate Mutex:: and use Monitor:: instead. | |
255 // After all, monitors are sufficient for Java-level synchronization. At one point in time | |
256 // there may have been some benefit to having distinct mutexes and monitors, but that time | |
257 // has past. | |
258 // | |
259 // The Mutex/Monitor design parallels that of Java-monitors, being based on | |
260 // thread-specific park-unpark platform-specific primitives. | |
261 | |
262 | |
263 class Mutex : public Monitor { // degenerate Monitor | |
264 public: | |
265 Mutex (int rank, const char *name, bool allow_vm_block=false); | |
266 ~Mutex () ; | |
267 private: | |
268 bool notify () { ShouldNotReachHere(); return false; } | |
269 bool notify_all() { ShouldNotReachHere(); return false; } | |
270 bool wait (bool no_safepoint_check, long timeout, bool as_suspend_equivalent) { | |
271 ShouldNotReachHere() ; | |
272 return false ; | |
273 } | |
274 }; | |
275 | |
276 /* | |
277 * Per-thread blocking support for JSR166. See the Java-level | |
278 * Documentation for rationale. Basically, park acts like wait, unpark | |
279 * like notify. | |
280 * | |
281 * 6271289 -- | |
282 * To avoid errors where an os thread expires but the JavaThread still | |
283 * exists, Parkers are immortal (type-stable) and are recycled across | |
284 * new threads. This parallels the ParkEvent implementation. | |
285 * Because park-unpark allow spurious wakeups it is harmless if an | |
286 * unpark call unparks a new thread using the old Parker reference. | |
287 * | |
288 * In the future we'll want to think about eliminating Parker and using | |
289 * ParkEvent instead. There's considerable duplication between the two | |
290 * services. | |
291 * | |
292 */ | |
293 | |
294 class Parker : public os::PlatformParker { | |
295 private: | |
296 volatile int _counter ; | |
297 Parker * FreeNext ; | |
298 JavaThread * AssociatedWith ; // Current association | |
299 | |
300 public: | |
301 Parker() : PlatformParker() { | |
302 _counter = 0 ; | |
303 FreeNext = NULL ; | |
304 AssociatedWith = NULL ; | |
305 } | |
306 protected: | |
307 ~Parker() { ShouldNotReachHere(); } | |
308 public: | |
309 // For simplicity of interface with Java, all forms of park (indefinite, | |
310 // relative, and absolute) are multiplexed into one call. | |
311 void park(bool isAbsolute, jlong time); | |
312 void unpark(); | |
313 | |
314 // Lifecycle operators | |
315 static Parker * Allocate (JavaThread * t) ; | |
316 static void Release (Parker * e) ; | |
317 private: | |
318 static Parker * volatile FreeList ; | |
319 static volatile int ListLock ; | |
320 }; |