Mercurial > hg > truffle
annotate src/share/vm/runtime/mutex.hpp @ 7998:6a51fc70a15e
8006613: adding reason to made_not_compilable
Reviewed-by: kvn, vlivanov
Contributed-by: Igor Ignatyev <igor.ignatyev@oracle.com>
author | vlivanov |
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date | Tue, 05 Feb 2013 08:25:51 -0800 |
parents | b9a9ed0f8eeb |
children | 63a4eb8bcd23 |
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0 | 1 /* |
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2 * Copyright (c) 1998, 2012, 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 | |
1972 | 25 #ifndef SHARE_VM_RUNTIME_MUTEX_HPP |
26 #define SHARE_VM_RUNTIME_MUTEX_HPP | |
27 | |
28 #include "memory/allocation.hpp" | |
29 #include "runtime/os.hpp" | |
30 #include "utilities/histogram.hpp" | |
31 | |
0 | 32 // The SplitWord construct allows us to colocate the contention queue |
33 // (cxq) with the lock-byte. The queue elements are ParkEvents, which are | |
34 // always aligned on 256-byte addresses - the least significant byte of | |
35 // a ParkEvent is always 0. Colocating the lock-byte with the queue | |
36 // allows us to easily avoid what would otherwise be a race in lock() | |
37 // if we were to use two completely separate fields for the contention queue | |
38 // and the lock indicator. Specifically, colocation renders us immune | |
39 // from the race where a thread might enqueue itself in the lock() slow-path | |
40 // immediately after the lock holder drops the outer lock in the unlock() | |
41 // fast-path. | |
42 // | |
43 // Colocation allows us to use a fast-path unlock() form that uses | |
44 // A MEMBAR instead of a CAS. MEMBAR has lower local latency than CAS | |
45 // on many platforms. | |
46 // | |
47 // See: | |
48 // + http://blogs.sun.com/dave/entry/biased_locking_in_hotspot | |
49 // + http://blogs.sun.com/dave/resource/synchronization-public2.pdf | |
50 // | |
51 // Note that we're *not* using word-tearing the classic sense. | |
52 // The lock() fast-path will CAS the lockword and the unlock() | |
53 // fast-path will store into the lock-byte colocated within the lockword. | |
54 // We depend on the fact that all our reference platforms have | |
55 // coherent and atomic byte accesses. More precisely, byte stores | |
56 // interoperate in a safe, sane, and expected manner with respect to | |
57 // CAS, ST and LDs to the full-word containing the byte. | |
58 // If you're porting HotSpot to a platform where that isn't the case | |
59 // then you'll want change the unlock() fast path from: | |
60 // STB;MEMBAR #storeload; LDN | |
61 // to a full-word CAS of the lockword. | |
62 | |
63 | |
64 union SplitWord { // full-word with separately addressable LSB | |
65 volatile intptr_t FullWord ; | |
66 volatile void * Address ; | |
67 volatile jbyte Bytes [sizeof(intptr_t)] ; | |
68 } ; | |
69 | |
70 // Endian-ness ... index of least-significant byte in SplitWord.Bytes[] | |
1010 | 71 #ifdef VM_LITTLE_ENDIAN |
0 | 72 #define _LSBINDEX 0 |
73 #else | |
74 #define _LSBINDEX (sizeof(intptr_t)-1) | |
75 #endif | |
76 | |
77 class ParkEvent ; | |
78 | |
79 // See orderAccess.hpp. We assume throughout the VM that mutex lock and | |
80 // try_lock do fence-lock-acquire, and that unlock does a release-unlock, | |
81 // *in that order*. If their implementations change such that these | |
82 // assumptions are violated, a whole lot of code will break. | |
83 | |
605 | 84 // The default length of monitor name is chosen to be 64 to avoid false sharing. |
55
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85 static const int MONITOR_NAME_LEN = 64; |
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86 |
6197 | 87 class Monitor : public CHeapObj<mtInternal> { |
0 | 88 |
89 public: | |
90 // A special lock: Is a lock where you are guaranteed not to block while you are | |
91 // holding it, i.e., no vm operation can happen, taking other locks, etc. | |
92 // NOTE: It is critical that the rank 'special' be the lowest (earliest) | |
93 // (except for "event"?) for the deadlock dection to work correctly. | |
94 // The rank native is only for use in Mutex's created by JVM_RawMonitorCreate, | |
95 // which being external to the VM are not subject to deadlock detection. | |
96 // The rank safepoint is used only for synchronization in reaching a | |
97 // safepoint and leaving a safepoint. It is only used for the Safepoint_lock | |
98 // currently. While at a safepoint no mutexes of rank safepoint are held | |
99 // by any thread. | |
100 // The rank named "leaf" is probably historical (and should | |
101 // be changed) -- mutexes of this rank aren't really leaf mutexes | |
102 // at all. | |
103 enum lock_types { | |
104 event, | |
105 special, | |
106 suspend_resume, | |
107 leaf = suspend_resume + 2, | |
108 safepoint = leaf + 10, | |
109 barrier = safepoint + 1, | |
110 nonleaf = barrier + 1, | |
111 max_nonleaf = nonleaf + 900, | |
112 native = max_nonleaf + 1 | |
113 }; | |
114 | |
115 // The WaitSet and EntryList linked lists are composed of ParkEvents. | |
116 // I use ParkEvent instead of threads as ParkEvents are immortal and | |
117 // type-stable, meaning we can safely unpark() a possibly stale | |
118 // list element in the unlock()-path. | |
119 | |
120 protected: // Monitor-Mutex metadata | |
121 SplitWord _LockWord ; // Contention queue (cxq) colocated with Lock-byte | |
122 enum LockWordBits { _LBIT=1 } ; | |
123 Thread * volatile _owner; // The owner of the lock | |
124 // Consider sequestering _owner on its own $line | |
125 // to aid future synchronization mechanisms. | |
126 ParkEvent * volatile _EntryList ; // List of threads waiting for entry | |
127 ParkEvent * volatile _OnDeck ; // heir-presumptive | |
128 volatile intptr_t _WaitLock [1] ; // Protects _WaitSet | |
129 ParkEvent * volatile _WaitSet ; // LL of ParkEvents | |
130 volatile bool _snuck; // Used for sneaky locking (evil). | |
131 int NotifyCount ; // diagnostic assist | |
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132 char _name[MONITOR_NAME_LEN]; // Name of mutex |
0 | 133 |
134 // Debugging fields for naming, deadlock detection, etc. (some only used in debug mode) | |
135 #ifndef PRODUCT | |
136 bool _allow_vm_block; | |
137 debug_only(int _rank;) // rank (to avoid/detect potential deadlocks) | |
138 debug_only(Monitor * _next;) // Used by a Thread to link up owned locks | |
139 debug_only(Thread* _last_owner;) // the last thread to own the lock | |
140 debug_only(static bool contains(Monitor * locks, Monitor * lock);) | |
141 debug_only(static Monitor * get_least_ranked_lock(Monitor * locks);) | |
142 debug_only(Monitor * get_least_ranked_lock_besides_this(Monitor * locks);) | |
143 #endif | |
144 | |
145 void set_owner_implementation(Thread* owner) PRODUCT_RETURN; | |
146 void check_prelock_state (Thread* thread) PRODUCT_RETURN; | |
147 void check_block_state (Thread* thread) PRODUCT_RETURN; | |
148 | |
149 // platform-dependent support code can go here (in os_<os_family>.cpp) | |
150 public: | |
151 enum { | |
152 _no_safepoint_check_flag = true, | |
153 _allow_vm_block_flag = true, | |
154 _as_suspend_equivalent_flag = true | |
155 }; | |
156 | |
157 enum WaitResults { | |
158 CONDVAR_EVENT, // Wait returned because of condition variable notification | |
159 INTERRUPT_EVENT, // Wait returned because waiting thread was interrupted | |
160 NUMBER_WAIT_RESULTS | |
161 }; | |
162 | |
163 private: | |
164 int TrySpin (Thread * Self) ; | |
165 int TryLock () ; | |
166 int TryFast () ; | |
167 int AcquireOrPush (ParkEvent * ev) ; | |
168 void IUnlock (bool RelaxAssert) ; | |
169 void ILock (Thread * Self) ; | |
170 int IWait (Thread * Self, jlong timo); | |
171 int ILocked () ; | |
172 | |
173 protected: | |
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174 static void ClearMonitor (Monitor * m, const char* name = NULL) ; |
0 | 175 Monitor() ; |
176 | |
177 public: | |
178 Monitor(int rank, const char *name, bool allow_vm_block=false); | |
179 ~Monitor(); | |
180 | |
181 // Wait until monitor is notified (or times out). | |
182 // Defaults are to make safepoint checks, wait time is forever (i.e., | |
183 // zero), and not a suspend-equivalent condition. Returns true if wait | |
184 // times out; otherwise returns false. | |
185 bool wait(bool no_safepoint_check = !_no_safepoint_check_flag, | |
186 long timeout = 0, | |
187 bool as_suspend_equivalent = !_as_suspend_equivalent_flag); | |
188 bool notify(); | |
189 bool notify_all(); | |
190 | |
191 | |
192 void lock(); // prints out warning if VM thread blocks | |
193 void lock(Thread *thread); // overloaded with current thread | |
194 void unlock(); | |
195 bool is_locked() const { return _owner != NULL; } | |
196 | |
197 bool try_lock(); // Like lock(), but unblocking. It returns false instead | |
198 | |
199 // Lock without safepoint check. Should ONLY be used by safepoint code and other code | |
200 // that is guaranteed not to block while running inside the VM. | |
201 void lock_without_safepoint_check(); | |
202 void lock_without_safepoint_check (Thread * Self) ; | |
203 | |
204 // Current owner - not not MT-safe. Can only be used to guarantee that | |
205 // the current running thread owns the lock | |
206 Thread* owner() const { return _owner; } | |
207 bool owned_by_self() const; | |
208 | |
209 // Support for JVM_RawMonitorEnter & JVM_RawMonitorExit. These can be called by | |
210 // non-Java thread. (We should really have a RawMonitor abstraction) | |
211 void jvm_raw_lock(); | |
212 void jvm_raw_unlock(); | |
213 const char *name() const { return _name; } | |
214 | |
215 void print_on_error(outputStream* st) const; | |
216 | |
217 #ifndef PRODUCT | |
218 void print_on(outputStream* st) const; | |
219 void print() const { print_on(tty); } | |
220 debug_only(int rank() const { return _rank; }) | |
221 bool allow_vm_block() { return _allow_vm_block; } | |
222 | |
223 debug_only(Monitor *next() const { return _next; }) | |
224 debug_only(void set_next(Monitor *next) { _next = next; }) | |
225 #endif | |
226 | |
227 void set_owner(Thread* owner) { | |
228 #ifndef PRODUCT | |
229 set_owner_implementation(owner); | |
230 debug_only(void verify_Monitor(Thread* thr)); | |
231 #else | |
232 _owner = owner; | |
233 #endif | |
234 } | |
235 | |
236 }; | |
237 | |
238 // Normally we'd expect Monitor to extend Mutex in the sense that a monitor | |
239 // constructed from pthreads primitives might extend a mutex by adding | |
240 // a condvar and some extra metadata. In fact this was the case until J2SE7. | |
241 // | |
242 // Currently, however, the base object is a monitor. Monitor contains all the | |
243 // logic for wait(), notify(), etc. Mutex extends monitor and restricts the | |
244 // visiblity of wait(), notify(), and notify_all(). | |
245 // | |
246 // Another viable alternative would have been to have Monitor extend Mutex and | |
247 // implement all the normal mutex and wait()-notify() logic in Mutex base class. | |
248 // The wait()-notify() facility would be exposed via special protected member functions | |
249 // (e.g., _Wait() and _Notify()) in Mutex. Monitor would extend Mutex and expose wait() | |
250 // as a call to _Wait(). That is, the public wait() would be a wrapper for the protected | |
251 // _Wait(). | |
252 // | |
253 // An even better alternative is to simply eliminate Mutex:: and use Monitor:: instead. | |
254 // After all, monitors are sufficient for Java-level synchronization. At one point in time | |
255 // there may have been some benefit to having distinct mutexes and monitors, but that time | |
256 // has past. | |
257 // | |
258 // The Mutex/Monitor design parallels that of Java-monitors, being based on | |
259 // thread-specific park-unpark platform-specific primitives. | |
260 | |
261 | |
262 class Mutex : public Monitor { // degenerate Monitor | |
263 public: | |
264 Mutex (int rank, const char *name, bool allow_vm_block=false); | |
265 ~Mutex () ; | |
266 private: | |
267 bool notify () { ShouldNotReachHere(); return false; } | |
268 bool notify_all() { ShouldNotReachHere(); return false; } | |
269 bool wait (bool no_safepoint_check, long timeout, bool as_suspend_equivalent) { | |
270 ShouldNotReachHere() ; | |
271 return false ; | |
272 } | |
273 }; | |
274 | |
1972 | 275 |
276 #endif // SHARE_VM_RUNTIME_MUTEX_HPP |