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annotate src/share/vm/runtime/orderAccess.hpp @ 15046:5c71dcf0915d
use hotspot static stubs for call sites
author | Tom Rodriguez <tom.rodriguez@oracle.com> |
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date | Wed, 09 Apr 2014 16:33:37 -0700 |
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0 | 1 /* |
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2 * Copyright (c) 2003, 2010, 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_ORDERACCESS_HPP |
26 #define SHARE_VM_RUNTIME_ORDERACCESS_HPP | |
27 | |
28 #include "memory/allocation.hpp" | |
29 | |
0 | 30 // Memory Access Ordering Model |
31 // | |
32 // This interface is based on the JSR-133 Cookbook for Compiler Writers | |
33 // and on the IA64 memory model. It is the dynamic equivalent of the | |
34 // C/C++ volatile specifier. I.e., volatility restricts compile-time | |
35 // memory access reordering in a way similar to what we want to occur | |
36 // at runtime. | |
37 // | |
38 // In the following, the terms 'previous', 'subsequent', 'before', | |
605 | 39 // 'after', 'preceding' and 'succeeding' refer to program order. The |
0 | 40 // terms 'down' and 'below' refer to forward load or store motion |
41 // relative to program order, while 'up' and 'above' refer to backward | |
42 // motion. | |
43 // | |
44 // | |
45 // We define four primitive memory barrier operations. | |
46 // | |
47 // LoadLoad: Load1(s); LoadLoad; Load2 | |
48 // | |
49 // Ensures that Load1 completes (obtains the value it loads from memory) | |
50 // before Load2 and any subsequent load operations. Loads before Load1 | |
51 // may *not* float below Load2 and any subsequent load operations. | |
52 // | |
53 // StoreStore: Store1(s); StoreStore; Store2 | |
54 // | |
55 // Ensures that Store1 completes (the effect on memory of Store1 is made | |
56 // visible to other processors) before Store2 and any subsequent store | |
57 // operations. Stores before Store1 may *not* float below Store2 and any | |
58 // subsequent store operations. | |
59 // | |
60 // LoadStore: Load1(s); LoadStore; Store2 | |
61 // | |
62 // Ensures that Load1 completes before Store2 and any subsequent store | |
63 // operations. Loads before Load1 may *not* float below Store2 and any | |
14909 | 64 // subseqeuent store operations. |
0 | 65 // |
66 // StoreLoad: Store1(s); StoreLoad; Load2 | |
67 // | |
68 // Ensures that Store1 completes before Load2 and any subsequent load | |
69 // operations. Stores before Store1 may *not* float below Load2 and any | |
14909 | 70 // subseqeuent load operations. |
0 | 71 // |
72 // | |
73 // We define two further operations, 'release' and 'acquire'. They are | |
74 // mirror images of each other. | |
75 // | |
76 // Execution by a processor of release makes the effect of all memory | |
77 // accesses issued by it previous to the release visible to all | |
78 // processors *before* the release completes. The effect of subsequent | |
79 // memory accesses issued by it *may* be made visible *before* the | |
80 // release. I.e., subsequent memory accesses may float above the | |
81 // release, but prior ones may not float below it. | |
82 // | |
83 // Execution by a processor of acquire makes the effect of all memory | |
84 // accesses issued by it subsequent to the acquire visible to all | |
85 // processors *after* the acquire completes. The effect of prior memory | |
86 // accesses issued by it *may* be made visible *after* the acquire. | |
87 // I.e., prior memory accesses may float below the acquire, but | |
88 // subsequent ones may not float above it. | |
89 // | |
90 // Finally, we define a 'fence' operation, which conceptually is a | |
91 // release combined with an acquire. In the real world these operations | |
92 // require one or more machine instructions which can float above and | |
93 // below the release or acquire, so we usually can't just issue the | |
94 // release-acquire back-to-back. All machines we know of implement some | |
95 // sort of memory fence instruction. | |
96 // | |
97 // | |
98 // The standalone implementations of release and acquire need an associated | |
99 // dummy volatile store or load respectively. To avoid redundant operations, | |
100 // we can define the composite operators: 'release_store', 'store_fence' and | |
101 // 'load_acquire'. Here's a summary of the machine instructions corresponding | |
102 // to each operation. | |
103 // | |
104 // sparc RMO ia64 x86 | |
105 // --------------------------------------------------------------------- | |
106 // fence membar #LoadStore | mf lock addl 0,(sp) | |
107 // #StoreStore | | |
108 // #LoadLoad | | |
109 // #StoreLoad | |
110 // | |
111 // release membar #LoadStore | st.rel [sp]=r0 movl $0,<dummy> | |
112 // #StoreStore | |
113 // st %g0,[] | |
114 // | |
115 // acquire ld [%sp],%g0 ld.acq <r>=[sp] movl (sp),<r> | |
116 // membar #LoadLoad | | |
117 // #LoadStore | |
118 // | |
119 // release_store membar #LoadStore | st.rel <store> | |
120 // #StoreStore | |
121 // st | |
122 // | |
123 // store_fence st st lock xchg | |
124 // fence mf | |
125 // | |
126 // load_acquire ld ld.acq <load> | |
127 // membar #LoadLoad | | |
128 // #LoadStore | |
129 // | |
130 // Using only release_store and load_acquire, we can implement the | |
131 // following ordered sequences. | |
132 // | |
133 // 1. load, load == load_acquire, load | |
134 // or load_acquire, load_acquire | |
135 // 2. load, store == load, release_store | |
136 // or load_acquire, store | |
137 // or load_acquire, release_store | |
138 // 3. store, store == store, release_store | |
139 // or release_store, release_store | |
140 // | |
141 // These require no membar instructions for sparc-TSO and no extra | |
142 // instructions for ia64. | |
143 // | |
144 // Ordering a load relative to preceding stores requires a store_fence, | |
145 // which implies a membar #StoreLoad between the store and load under | |
146 // sparc-TSO. A fence is required by ia64. On x86, we use locked xchg. | |
147 // | |
148 // 4. store, load == store_fence, load | |
149 // | |
150 // Use store_fence to make sure all stores done in an 'interesting' | |
151 // region are made visible prior to both subsequent loads and stores. | |
152 // | |
153 // Conventional usage is to issue a load_acquire for ordered loads. Use | |
154 // release_store for ordered stores when you care only that prior stores | |
155 // are visible before the release_store, but don't care exactly when the | |
156 // store associated with the release_store becomes visible. Use | |
157 // release_store_fence to update values like the thread state, where we | |
158 // don't want the current thread to continue until all our prior memory | |
159 // accesses (including the new thread state) are visible to other threads. | |
160 // | |
161 // | |
162 // C++ Volatility | |
163 // | |
164 // C++ guarantees ordering at operations termed 'sequence points' (defined | |
165 // to be volatile accesses and calls to library I/O functions). 'Side | |
166 // effects' (defined as volatile accesses, calls to library I/O functions | |
167 // and object modification) previous to a sequence point must be visible | |
168 // at that sequence point. See the C++ standard, section 1.9, titled | |
169 // "Program Execution". This means that all barrier implementations, | |
170 // including standalone loadload, storestore, loadstore, storeload, acquire | |
171 // and release must include a sequence point, usually via a volatile memory | |
172 // access. Other ways to guarantee a sequence point are, e.g., use of | |
173 // indirect calls and linux's __asm__ volatile. | |
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174 // Note: as of 6973570, we have replaced the originally static "dummy" field |
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175 // (see above) by a volatile store to the stack. All of the versions of the |
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176 // compilers that we currently use (SunStudio, gcc and VC++) respect the |
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177 // semantics of volatile here. If you build HotSpot using other |
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178 // compilers, you may need to verify that no compiler reordering occurs |
14909 | 179 // across the sequence point respresented by the volatile access. |
0 | 180 // |
181 // | |
182 // os::is_MP Considered Redundant | |
183 // | |
184 // Callers of this interface do not need to test os::is_MP() before | |
185 // issuing an operation. The test is taken care of by the implementation | |
186 // of the interface (depending on the vm version and platform, the test | |
187 // may or may not be actually done by the implementation). | |
188 // | |
189 // | |
190 // A Note on Memory Ordering and Cache Coherency | |
191 // | |
192 // Cache coherency and memory ordering are orthogonal concepts, though they | |
193 // interact. E.g., all existing itanium machines are cache-coherent, but | |
194 // the hardware can freely reorder loads wrt other loads unless it sees a | |
195 // load-acquire instruction. All existing sparc machines are cache-coherent | |
196 // and, unlike itanium, TSO guarantees that the hardware orders loads wrt | |
197 // loads and stores, and stores wrt to each other. | |
198 // | |
199 // Consider the implementation of loadload. *If* your platform *isn't* | |
200 // cache-coherent, then loadload must not only prevent hardware load | |
201 // instruction reordering, but it must *also* ensure that subsequent | |
202 // loads from addresses that could be written by other processors (i.e., | |
203 // that are broadcast by other processors) go all the way to the first | |
204 // level of memory shared by those processors and the one issuing | |
205 // the loadload. | |
206 // | |
207 // So if we have a MP that has, say, a per-processor D$ that doesn't see | |
208 // writes by other processors, and has a shared E$ that does, the loadload | |
209 // barrier would have to make sure that either | |
210 // | |
211 // 1. cache lines in the issuing processor's D$ that contained data from | |
212 // addresses that could be written by other processors are invalidated, so | |
213 // subsequent loads from those addresses go to the E$, (it could do this | |
214 // by tagging such cache lines as 'shared', though how to tell the hardware | |
215 // to do the tagging is an interesting problem), or | |
216 // | |
217 // 2. there never are such cache lines in the issuing processor's D$, which | |
218 // means all references to shared data (however identified: see above) | |
219 // bypass the D$ (i.e., are satisfied from the E$). | |
220 // | |
221 // If your machine doesn't have an E$, substitute 'main memory' for 'E$'. | |
222 // | |
223 // Either of these alternatives is a pain, so no current machine we know of | |
224 // has incoherent caches. | |
225 // | |
226 // If loadload didn't have these properties, the store-release sequence for | |
227 // publishing a shared data structure wouldn't work, because a processor | |
228 // trying to read data newly published by another processor might go to | |
229 // its own incoherent caches to satisfy the read instead of to the newly | |
230 // written shared memory. | |
231 // | |
232 // | |
233 // NOTE WELL!! | |
234 // | |
235 // A Note on MutexLocker and Friends | |
236 // | |
237 // See mutexLocker.hpp. We assume throughout the VM that MutexLocker's | |
238 // and friends' constructors do a fence, a lock and an acquire *in that | |
239 // order*. And that their destructors do a release and unlock, in *that* | |
240 // order. If their implementations change such that these assumptions | |
241 // are violated, a whole lot of code will break. | |
242 | |
243 class OrderAccess : AllStatic { | |
244 public: | |
245 static void loadload(); | |
246 static void storestore(); | |
247 static void loadstore(); | |
248 static void storeload(); | |
249 | |
250 static void acquire(); | |
251 static void release(); | |
252 static void fence(); | |
253 | |
254 static jbyte load_acquire(volatile jbyte* p); | |
255 static jshort load_acquire(volatile jshort* p); | |
256 static jint load_acquire(volatile jint* p); | |
257 static jlong load_acquire(volatile jlong* p); | |
258 static jubyte load_acquire(volatile jubyte* p); | |
259 static jushort load_acquire(volatile jushort* p); | |
260 static juint load_acquire(volatile juint* p); | |
261 static julong load_acquire(volatile julong* p); | |
262 static jfloat load_acquire(volatile jfloat* p); | |
263 static jdouble load_acquire(volatile jdouble* p); | |
264 | |
265 static intptr_t load_ptr_acquire(volatile intptr_t* p); | |
266 static void* load_ptr_acquire(volatile void* p); | |
267 static void* load_ptr_acquire(const volatile void* p); | |
268 | |
269 static void release_store(volatile jbyte* p, jbyte v); | |
270 static void release_store(volatile jshort* p, jshort v); | |
271 static void release_store(volatile jint* p, jint v); | |
272 static void release_store(volatile jlong* p, jlong v); | |
273 static void release_store(volatile jubyte* p, jubyte v); | |
274 static void release_store(volatile jushort* p, jushort v); | |
275 static void release_store(volatile juint* p, juint v); | |
276 static void release_store(volatile julong* p, julong v); | |
277 static void release_store(volatile jfloat* p, jfloat v); | |
278 static void release_store(volatile jdouble* p, jdouble v); | |
279 | |
280 static void release_store_ptr(volatile intptr_t* p, intptr_t v); | |
281 static void release_store_ptr(volatile void* p, void* v); | |
282 | |
283 static void store_fence(jbyte* p, jbyte v); | |
284 static void store_fence(jshort* p, jshort v); | |
285 static void store_fence(jint* p, jint v); | |
286 static void store_fence(jlong* p, jlong v); | |
287 static void store_fence(jubyte* p, jubyte v); | |
288 static void store_fence(jushort* p, jushort v); | |
289 static void store_fence(juint* p, juint v); | |
290 static void store_fence(julong* p, julong v); | |
291 static void store_fence(jfloat* p, jfloat v); | |
292 static void store_fence(jdouble* p, jdouble v); | |
293 | |
294 static void store_ptr_fence(intptr_t* p, intptr_t v); | |
295 static void store_ptr_fence(void** p, void* v); | |
296 | |
297 static void release_store_fence(volatile jbyte* p, jbyte v); | |
298 static void release_store_fence(volatile jshort* p, jshort v); | |
299 static void release_store_fence(volatile jint* p, jint v); | |
300 static void release_store_fence(volatile jlong* p, jlong v); | |
301 static void release_store_fence(volatile jubyte* p, jubyte v); | |
302 static void release_store_fence(volatile jushort* p, jushort v); | |
303 static void release_store_fence(volatile juint* p, juint v); | |
304 static void release_store_fence(volatile julong* p, julong v); | |
305 static void release_store_fence(volatile jfloat* p, jfloat v); | |
306 static void release_store_fence(volatile jdouble* p, jdouble v); | |
307 | |
308 static void release_store_ptr_fence(volatile intptr_t* p, intptr_t v); | |
309 static void release_store_ptr_fence(volatile void* p, void* v); | |
310 | |
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311 private: |
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312 // This is a helper that invokes the StubRoutines::fence_entry() |
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313 // routine if it exists, It should only be used by platforms that |
14909 | 314 // don't another way to do the inline eassembly. |
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315 static void StubRoutines_fence(); |
0 | 316 }; |
1972 | 317 |
318 #endif // SHARE_VM_RUNTIME_ORDERACCESS_HPP |