Mercurial > hg > graal-compiler
annotate src/share/vm/runtime/mutex.hpp @ 1782:f353275af40e
6981773: incorrect fill value with OptimizeFill
Reviewed-by: kvn, twisti
author | never |
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date | Thu, 02 Sep 2010 11:40:02 -0700 |
parents | c18cbe5936b8 |
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0 | 1 /* |
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2 * Copyright (c) 1998, 2008, Oracle and/or its affiliates. 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 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[] | |
1010 | 64 #ifdef VM_LITTLE_ENDIAN |
0 | 65 #define _LSBINDEX 0 |
66 #else | |
67 #define _LSBINDEX (sizeof(intptr_t)-1) | |
68 #endif | |
69 | |
70 class ParkEvent ; | |
71 | |
72 // See orderAccess.hpp. We assume throughout the VM that mutex lock and | |
73 // try_lock do fence-lock-acquire, and that unlock does a release-unlock, | |
74 // *in that order*. If their implementations change such that these | |
75 // assumptions are violated, a whole lot of code will break. | |
76 | |
605 | 77 // The default length of monitor name is chosen to be 64 to avoid false sharing. |
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78 static const int MONITOR_NAME_LEN = 64; |
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79 |
0 | 80 class Monitor : public CHeapObj { |
81 | |
82 public: | |
83 // A special lock: Is a lock where you are guaranteed not to block while you are | |
84 // holding it, i.e., no vm operation can happen, taking other locks, etc. | |
85 // NOTE: It is critical that the rank 'special' be the lowest (earliest) | |
86 // (except for "event"?) for the deadlock dection to work correctly. | |
87 // The rank native is only for use in Mutex's created by JVM_RawMonitorCreate, | |
88 // which being external to the VM are not subject to deadlock detection. | |
89 // The rank safepoint is used only for synchronization in reaching a | |
90 // safepoint and leaving a safepoint. It is only used for the Safepoint_lock | |
91 // currently. While at a safepoint no mutexes of rank safepoint are held | |
92 // by any thread. | |
93 // The rank named "leaf" is probably historical (and should | |
94 // be changed) -- mutexes of this rank aren't really leaf mutexes | |
95 // at all. | |
96 enum lock_types { | |
97 event, | |
98 special, | |
99 suspend_resume, | |
100 leaf = suspend_resume + 2, | |
101 safepoint = leaf + 10, | |
102 barrier = safepoint + 1, | |
103 nonleaf = barrier + 1, | |
104 max_nonleaf = nonleaf + 900, | |
105 native = max_nonleaf + 1 | |
106 }; | |
107 | |
108 // The WaitSet and EntryList linked lists are composed of ParkEvents. | |
109 // I use ParkEvent instead of threads as ParkEvents are immortal and | |
110 // type-stable, meaning we can safely unpark() a possibly stale | |
111 // list element in the unlock()-path. | |
112 | |
113 protected: // Monitor-Mutex metadata | |
114 SplitWord _LockWord ; // Contention queue (cxq) colocated with Lock-byte | |
115 enum LockWordBits { _LBIT=1 } ; | |
116 Thread * volatile _owner; // The owner of the lock | |
117 // Consider sequestering _owner on its own $line | |
118 // to aid future synchronization mechanisms. | |
119 ParkEvent * volatile _EntryList ; // List of threads waiting for entry | |
120 ParkEvent * volatile _OnDeck ; // heir-presumptive | |
121 volatile intptr_t _WaitLock [1] ; // Protects _WaitSet | |
122 ParkEvent * volatile _WaitSet ; // LL of ParkEvents | |
123 volatile bool _snuck; // Used for sneaky locking (evil). | |
124 int NotifyCount ; // diagnostic assist | |
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125 char _name[MONITOR_NAME_LEN]; // Name of mutex |
0 | 126 |
127 // Debugging fields for naming, deadlock detection, etc. (some only used in debug mode) | |
128 #ifndef PRODUCT | |
129 bool _allow_vm_block; | |
130 debug_only(int _rank;) // rank (to avoid/detect potential deadlocks) | |
131 debug_only(Monitor * _next;) // Used by a Thread to link up owned locks | |
132 debug_only(Thread* _last_owner;) // the last thread to own the lock | |
133 debug_only(static bool contains(Monitor * locks, Monitor * lock);) | |
134 debug_only(static Monitor * get_least_ranked_lock(Monitor * locks);) | |
135 debug_only(Monitor * get_least_ranked_lock_besides_this(Monitor * locks);) | |
136 #endif | |
137 | |
138 void set_owner_implementation(Thread* owner) PRODUCT_RETURN; | |
139 void check_prelock_state (Thread* thread) PRODUCT_RETURN; | |
140 void check_block_state (Thread* thread) PRODUCT_RETURN; | |
141 | |
142 // platform-dependent support code can go here (in os_<os_family>.cpp) | |
143 public: | |
144 enum { | |
145 _no_safepoint_check_flag = true, | |
146 _allow_vm_block_flag = true, | |
147 _as_suspend_equivalent_flag = true | |
148 }; | |
149 | |
150 enum WaitResults { | |
151 CONDVAR_EVENT, // Wait returned because of condition variable notification | |
152 INTERRUPT_EVENT, // Wait returned because waiting thread was interrupted | |
153 NUMBER_WAIT_RESULTS | |
154 }; | |
155 | |
156 private: | |
157 int TrySpin (Thread * Self) ; | |
158 int TryLock () ; | |
159 int TryFast () ; | |
160 int AcquireOrPush (ParkEvent * ev) ; | |
161 void IUnlock (bool RelaxAssert) ; | |
162 void ILock (Thread * Self) ; | |
163 int IWait (Thread * Self, jlong timo); | |
164 int ILocked () ; | |
165 | |
166 protected: | |
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167 static void ClearMonitor (Monitor * m, const char* name = NULL) ; |
0 | 168 Monitor() ; |
169 | |
170 public: | |
171 Monitor(int rank, const char *name, bool allow_vm_block=false); | |
172 ~Monitor(); | |
173 | |
174 // Wait until monitor is notified (or times out). | |
175 // Defaults are to make safepoint checks, wait time is forever (i.e., | |
176 // zero), and not a suspend-equivalent condition. Returns true if wait | |
177 // times out; otherwise returns false. | |
178 bool wait(bool no_safepoint_check = !_no_safepoint_check_flag, | |
179 long timeout = 0, | |
180 bool as_suspend_equivalent = !_as_suspend_equivalent_flag); | |
181 bool notify(); | |
182 bool notify_all(); | |
183 | |
184 | |
185 void lock(); // prints out warning if VM thread blocks | |
186 void lock(Thread *thread); // overloaded with current thread | |
187 void unlock(); | |
188 bool is_locked() const { return _owner != NULL; } | |
189 | |
190 bool try_lock(); // Like lock(), but unblocking. It returns false instead | |
191 | |
192 // Lock without safepoint check. Should ONLY be used by safepoint code and other code | |
193 // that is guaranteed not to block while running inside the VM. | |
194 void lock_without_safepoint_check(); | |
195 void lock_without_safepoint_check (Thread * Self) ; | |
196 | |
197 // Current owner - not not MT-safe. Can only be used to guarantee that | |
198 // the current running thread owns the lock | |
199 Thread* owner() const { return _owner; } | |
200 bool owned_by_self() const; | |
201 | |
202 // Support for JVM_RawMonitorEnter & JVM_RawMonitorExit. These can be called by | |
203 // non-Java thread. (We should really have a RawMonitor abstraction) | |
204 void jvm_raw_lock(); | |
205 void jvm_raw_unlock(); | |
206 const char *name() const { return _name; } | |
207 | |
208 void print_on_error(outputStream* st) const; | |
209 | |
210 #ifndef PRODUCT | |
211 void print_on(outputStream* st) const; | |
212 void print() const { print_on(tty); } | |
213 debug_only(int rank() const { return _rank; }) | |
214 bool allow_vm_block() { return _allow_vm_block; } | |
215 | |
216 debug_only(Monitor *next() const { return _next; }) | |
217 debug_only(void set_next(Monitor *next) { _next = next; }) | |
218 #endif | |
219 | |
220 void set_owner(Thread* owner) { | |
221 #ifndef PRODUCT | |
222 set_owner_implementation(owner); | |
223 debug_only(void verify_Monitor(Thread* thr)); | |
224 #else | |
225 _owner = owner; | |
226 #endif | |
227 } | |
228 | |
229 }; | |
230 | |
231 // Normally we'd expect Monitor to extend Mutex in the sense that a monitor | |
232 // constructed from pthreads primitives might extend a mutex by adding | |
233 // a condvar and some extra metadata. In fact this was the case until J2SE7. | |
234 // | |
235 // Currently, however, the base object is a monitor. Monitor contains all the | |
236 // logic for wait(), notify(), etc. Mutex extends monitor and restricts the | |
237 // visiblity of wait(), notify(), and notify_all(). | |
238 // | |
239 // Another viable alternative would have been to have Monitor extend Mutex and | |
240 // implement all the normal mutex and wait()-notify() logic in Mutex base class. | |
241 // The wait()-notify() facility would be exposed via special protected member functions | |
242 // (e.g., _Wait() and _Notify()) in Mutex. Monitor would extend Mutex and expose wait() | |
243 // as a call to _Wait(). That is, the public wait() would be a wrapper for the protected | |
244 // _Wait(). | |
245 // | |
246 // An even better alternative is to simply eliminate Mutex:: and use Monitor:: instead. | |
247 // After all, monitors are sufficient for Java-level synchronization. At one point in time | |
248 // there may have been some benefit to having distinct mutexes and monitors, but that time | |
249 // has past. | |
250 // | |
251 // The Mutex/Monitor design parallels that of Java-monitors, being based on | |
252 // thread-specific park-unpark platform-specific primitives. | |
253 | |
254 | |
255 class Mutex : public Monitor { // degenerate Monitor | |
256 public: | |
257 Mutex (int rank, const char *name, bool allow_vm_block=false); | |
258 ~Mutex () ; | |
259 private: | |
260 bool notify () { ShouldNotReachHere(); return false; } | |
261 bool notify_all() { ShouldNotReachHere(); return false; } | |
262 bool wait (bool no_safepoint_check, long timeout, bool as_suspend_equivalent) { | |
263 ShouldNotReachHere() ; | |
264 return false ; | |
265 } | |
266 }; | |
267 | |
268 /* | |
269 * Per-thread blocking support for JSR166. See the Java-level | |
270 * Documentation for rationale. Basically, park acts like wait, unpark | |
271 * like notify. | |
272 * | |
273 * 6271289 -- | |
274 * To avoid errors where an os thread expires but the JavaThread still | |
275 * exists, Parkers are immortal (type-stable) and are recycled across | |
276 * new threads. This parallels the ParkEvent implementation. | |
277 * Because park-unpark allow spurious wakeups it is harmless if an | |
278 * unpark call unparks a new thread using the old Parker reference. | |
279 * | |
280 * In the future we'll want to think about eliminating Parker and using | |
281 * ParkEvent instead. There's considerable duplication between the two | |
282 * services. | |
283 * | |
284 */ | |
285 | |
286 class Parker : public os::PlatformParker { | |
287 private: | |
288 volatile int _counter ; | |
289 Parker * FreeNext ; | |
290 JavaThread * AssociatedWith ; // Current association | |
291 | |
292 public: | |
293 Parker() : PlatformParker() { | |
294 _counter = 0 ; | |
295 FreeNext = NULL ; | |
296 AssociatedWith = NULL ; | |
297 } | |
298 protected: | |
299 ~Parker() { ShouldNotReachHere(); } | |
300 public: | |
301 // For simplicity of interface with Java, all forms of park (indefinite, | |
302 // relative, and absolute) are multiplexed into one call. | |
303 void park(bool isAbsolute, jlong time); | |
304 void unpark(); | |
305 | |
306 // Lifecycle operators | |
307 static Parker * Allocate (JavaThread * t) ; | |
308 static void Release (Parker * e) ; | |
309 private: | |
310 static Parker * volatile FreeList ; | |
311 static volatile int ListLock ; | |
312 }; |