Mercurial > hg > truffle
annotate src/share/vm/memory/gcLocker.hpp @ 2645:b2c1e959be46
Clean up around BlockBegin / StdEntry.
author | Thomas Wuerthinger <thomas@wuerthinger.net> |
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date | Wed, 11 May 2011 14:34:29 +0200 |
parents | f95d63e2154a |
children | f08d439fab8c |
rev | line source |
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0 | 1 /* |
1972 | 2 * Copyright (c) 1997, 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 * | |
1552
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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_MEMORY_GCLOCKER_HPP |
26 #define SHARE_VM_MEMORY_GCLOCKER_HPP | |
27 | |
28 #include "gc_interface/collectedHeap.hpp" | |
29 #include "memory/genCollectedHeap.hpp" | |
30 #include "memory/universe.hpp" | |
31 #include "oops/oop.hpp" | |
32 #ifdef TARGET_OS_FAMILY_linux | |
33 # include "os_linux.inline.hpp" | |
34 # include "thread_linux.inline.hpp" | |
35 #endif | |
36 #ifdef TARGET_OS_FAMILY_solaris | |
37 # include "os_solaris.inline.hpp" | |
38 # include "thread_solaris.inline.hpp" | |
39 #endif | |
40 #ifdef TARGET_OS_FAMILY_windows | |
41 # include "os_windows.inline.hpp" | |
42 # include "thread_windows.inline.hpp" | |
43 #endif | |
44 | |
0 | 45 // The direct lock/unlock calls do not force a collection if an unlock |
46 // decrements the count to zero. Avoid calling these if at all possible. | |
47 | |
48 class GC_locker: public AllStatic { | |
49 private: | |
50 static volatile jint _jni_lock_count; // number of jni active instances | |
51 static volatile jint _lock_count; // number of other active instances | |
52 static volatile bool _needs_gc; // heap is filling, we need a GC | |
53 // note: bool is typedef'd as jint | |
54 static volatile bool _doing_gc; // unlock_critical() is doing a GC | |
55 | |
56 // Accessors | |
57 static bool is_jni_active() { | |
58 return _jni_lock_count > 0; | |
59 } | |
60 | |
61 static void set_needs_gc() { | |
62 assert(SafepointSynchronize::is_at_safepoint(), | |
63 "needs_gc is only set at a safepoint"); | |
64 _needs_gc = true; | |
65 } | |
66 | |
67 static void clear_needs_gc() { | |
68 assert_lock_strong(JNICritical_lock); | |
69 _needs_gc = false; | |
70 } | |
71 | |
72 static void jni_lock() { | |
73 Atomic::inc(&_jni_lock_count); | |
74 CHECK_UNHANDLED_OOPS_ONLY( | |
75 if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count++; }) | |
76 assert(Universe::heap() == NULL || !Universe::heap()->is_gc_active(), | |
77 "locking failed"); | |
78 } | |
79 | |
80 static void jni_unlock() { | |
81 Atomic::dec(&_jni_lock_count); | |
82 CHECK_UNHANDLED_OOPS_ONLY( | |
83 if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count--; }) | |
84 } | |
85 | |
86 static void jni_lock_slow(); | |
87 static void jni_unlock_slow(); | |
88 | |
89 public: | |
90 // Accessors | |
91 static bool is_active(); | |
92 static bool needs_gc() { return _needs_gc; } | |
93 // Shorthand | |
94 static bool is_active_and_needs_gc() { return is_active() && needs_gc();} | |
95 | |
96 // Calls set_needs_gc() if is_active() is true. Returns is_active(). | |
97 static bool check_active_before_gc(); | |
98 | |
99 // Stalls the caller (who should not be in a jni critical section) | |
100 // until needs_gc() clears. Note however that needs_gc() may be | |
101 // set at a subsequent safepoint and/or cleared under the | |
102 // JNICritical_lock, so the caller may not safely assert upon | |
103 // return from this method that "!needs_gc()" since that is | |
104 // not a stable predicate. | |
105 static void stall_until_clear(); | |
106 | |
107 // Non-structured GC locking: currently needed for JNI. Use with care! | |
108 static void lock(); | |
109 static void unlock(); | |
110 | |
111 // The following two methods are used for JNI critical regions. | |
112 // If we find that we failed to perform a GC because the GC_locker | |
113 // was active, arrange for one as soon as possible by allowing | |
114 // all threads in critical regions to complete, but not allowing | |
115 // other critical regions to be entered. The reasons for that are: | |
116 // 1) a GC request won't be starved by overlapping JNI critical | |
117 // region activities, which can cause unnecessary OutOfMemory errors. | |
118 // 2) even if allocation requests can still be satisfied before GC locker | |
119 // becomes inactive, for example, in tenured generation possibly with | |
120 // heap expansion, those allocations can trigger lots of safepointing | |
121 // attempts (ineffective GC attempts) and require Heap_lock which | |
122 // slow down allocations tremendously. | |
123 // | |
124 // Note that critical regions can be nested in a single thread, so | |
125 // we must allow threads already in critical regions to continue. | |
126 // | |
127 // JNI critical regions are the only participants in this scheme | |
128 // because they are, by spec, well bounded while in a critical region. | |
129 // | |
130 // Each of the following two method is split into a fast path and a slow | |
131 // path. JNICritical_lock is only grabbed in the slow path. | |
132 // _needs_gc is initially false and every java thread will go | |
133 // through the fast path (which does the same thing as the slow path | |
134 // when _needs_gc is false). When GC happens at a safepoint, | |
135 // GC_locker::is_active() is checked. Since there is no safepoint in the | |
136 // fast path of lock_critical() and unlock_critical(), there is no race | |
137 // condition between the fast path and GC. After _needs_gc is set at a | |
138 // safepoint, every thread will go through the slow path after the safepoint. | |
139 // Since after a safepoint, each of the following two methods is either | |
140 // entered from the method entry and falls into the slow path, or is | |
141 // resumed from the safepoints in the method, which only exist in the slow | |
142 // path. So when _needs_gc is set, the slow path is always taken, till | |
143 // _needs_gc is cleared. | |
144 static void lock_critical(JavaThread* thread); | |
145 static void unlock_critical(JavaThread* thread); | |
146 }; | |
147 | |
148 | |
149 // A No_GC_Verifier object can be placed in methods where one assumes that | |
150 // no garbage collection will occur. The destructor will verify this property | |
151 // unless the constructor is called with argument false (not verifygc). | |
152 // | |
153 // The check will only be done in debug mode and if verifygc true. | |
154 | |
155 class No_GC_Verifier: public StackObj { | |
156 friend class Pause_No_GC_Verifier; | |
157 | |
158 protected: | |
159 bool _verifygc; | |
160 unsigned int _old_invocations; | |
161 | |
162 public: | |
163 #ifdef ASSERT | |
164 No_GC_Verifier(bool verifygc = true); | |
165 ~No_GC_Verifier(); | |
166 #else | |
167 No_GC_Verifier(bool verifygc = true) {} | |
168 ~No_GC_Verifier() {} | |
169 #endif | |
170 }; | |
171 | |
172 // A Pause_No_GC_Verifier is used to temporarily pause the behavior | |
173 // of a No_GC_Verifier object. If we are not in debug mode or if the | |
174 // No_GC_Verifier object has a _verifygc value of false, then there | |
175 // is nothing to do. | |
176 | |
177 class Pause_No_GC_Verifier: public StackObj { | |
178 private: | |
179 No_GC_Verifier * _ngcv; | |
180 | |
181 public: | |
182 #ifdef ASSERT | |
183 Pause_No_GC_Verifier(No_GC_Verifier * ngcv); | |
184 ~Pause_No_GC_Verifier(); | |
185 #else | |
186 Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {} | |
187 ~Pause_No_GC_Verifier() {} | |
188 #endif | |
189 }; | |
190 | |
191 | |
192 // A No_Safepoint_Verifier object will throw an assertion failure if | |
193 // the current thread passes a possible safepoint while this object is | |
194 // instantiated. A safepoint, will either be: an oop allocation, blocking | |
195 // on a Mutex or JavaLock, or executing a VM operation. | |
196 // | |
197 // If StrictSafepointChecks is turned off, it degrades into a No_GC_Verifier | |
198 // | |
199 class No_Safepoint_Verifier : public No_GC_Verifier { | |
200 friend class Pause_No_Safepoint_Verifier; | |
201 | |
202 private: | |
203 bool _activated; | |
204 Thread *_thread; | |
205 public: | |
206 #ifdef ASSERT | |
98
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207 No_Safepoint_Verifier(bool activated = true, bool verifygc = true ) : |
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208 No_GC_Verifier(verifygc), |
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209 _activated(activated) { |
0 | 210 _thread = Thread::current(); |
211 if (_activated) { | |
212 _thread->_allow_allocation_count++; | |
213 _thread->_allow_safepoint_count++; | |
214 } | |
215 } | |
216 | |
217 ~No_Safepoint_Verifier() { | |
218 if (_activated) { | |
219 _thread->_allow_allocation_count--; | |
220 _thread->_allow_safepoint_count--; | |
221 } | |
222 } | |
223 #else | |
224 No_Safepoint_Verifier(bool activated = true, bool verifygc = true) : No_GC_Verifier(verifygc){} | |
225 ~No_Safepoint_Verifier() {} | |
226 #endif | |
227 }; | |
228 | |
229 // A Pause_No_Safepoint_Verifier is used to temporarily pause the | |
230 // behavior of a No_Safepoint_Verifier object. If we are not in debug | |
231 // mode then there is nothing to do. If the No_Safepoint_Verifier | |
232 // object has an _activated value of false, then there is nothing to | |
233 // do for safepoint and allocation checking, but there may still be | |
234 // something to do for the underlying No_GC_Verifier object. | |
235 | |
236 class Pause_No_Safepoint_Verifier : public Pause_No_GC_Verifier { | |
237 private: | |
238 No_Safepoint_Verifier * _nsv; | |
239 | |
240 public: | |
241 #ifdef ASSERT | |
242 Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) | |
243 : Pause_No_GC_Verifier(nsv) { | |
244 | |
245 _nsv = nsv; | |
246 if (_nsv->_activated) { | |
247 _nsv->_thread->_allow_allocation_count--; | |
248 _nsv->_thread->_allow_safepoint_count--; | |
249 } | |
250 } | |
251 | |
252 ~Pause_No_Safepoint_Verifier() { | |
253 if (_nsv->_activated) { | |
254 _nsv->_thread->_allow_allocation_count++; | |
255 _nsv->_thread->_allow_safepoint_count++; | |
256 } | |
257 } | |
258 #else | |
259 Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) | |
260 : Pause_No_GC_Verifier(nsv) {} | |
261 ~Pause_No_Safepoint_Verifier() {} | |
262 #endif | |
263 }; | |
264 | |
806
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265 // A SkipGCALot object is used to elide the usual effect of gc-a-lot |
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266 // over a section of execution by a thread. Currently, it's used only to |
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267 // prevent re-entrant calls to GC. |
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268 class SkipGCALot : public StackObj { |
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269 private: |
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270 bool _saved; |
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271 Thread* _t; |
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272 |
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273 public: |
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274 #ifdef ASSERT |
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275 SkipGCALot(Thread* t) : _t(t) { |
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276 _saved = _t->skip_gcalot(); |
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277 _t->set_skip_gcalot(true); |
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278 } |
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279 |
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280 ~SkipGCALot() { |
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281 assert(_t->skip_gcalot(), "Save-restore protocol invariant"); |
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282 _t->set_skip_gcalot(_saved); |
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283 } |
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284 #else |
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285 SkipGCALot(Thread* t) { } |
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286 ~SkipGCALot() { } |
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287 #endif |
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288 }; |
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289 |
0 | 290 // JRT_LEAF currently can be called from either _thread_in_Java or |
291 // _thread_in_native mode. In _thread_in_native, it is ok | |
292 // for another thread to trigger GC. The rest of the JRT_LEAF | |
293 // rules apply. | |
294 class JRT_Leaf_Verifier : public No_Safepoint_Verifier { | |
295 static bool should_verify_GC(); | |
296 public: | |
297 #ifdef ASSERT | |
298 JRT_Leaf_Verifier(); | |
299 ~JRT_Leaf_Verifier(); | |
300 #else | |
301 JRT_Leaf_Verifier() {} | |
302 ~JRT_Leaf_Verifier() {} | |
303 #endif | |
304 }; | |
305 | |
306 // A No_Alloc_Verifier object can be placed in methods where one assumes that | |
307 // no allocation will occur. The destructor will verify this property | |
308 // unless the constructor is called with argument false (not activated). | |
309 // | |
310 // The check will only be done in debug mode and if activated. | |
311 // Note: this only makes sense at safepoints (otherwise, other threads may | |
312 // allocate concurrently.) | |
313 | |
314 class No_Alloc_Verifier : public StackObj { | |
315 private: | |
316 bool _activated; | |
317 | |
318 public: | |
319 #ifdef ASSERT | |
320 No_Alloc_Verifier(bool activated = true) { | |
321 _activated = activated; | |
322 if (_activated) Thread::current()->_allow_allocation_count++; | |
323 } | |
324 | |
325 ~No_Alloc_Verifier() { | |
326 if (_activated) Thread::current()->_allow_allocation_count--; | |
327 } | |
328 #else | |
329 No_Alloc_Verifier(bool activated = true) {} | |
330 ~No_Alloc_Verifier() {} | |
331 #endif | |
332 }; | |
1972 | 333 |
334 #endif // SHARE_VM_MEMORY_GCLOCKER_HPP |