Mercurial > hg > truffle
annotate src/share/vm/memory/gcLocker.hpp @ 9202:b6629b739a55
Merge.
author | Thomas Wuerthinger <thomas.wuerthinger@oracle.com> |
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date | Mon, 22 Apr 2013 09:54:57 +0200 |
parents | f34d701e952e |
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0 | 1 /* |
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2 * Copyright (c) 1997, 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_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" | |
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32 #include "runtime/thread.inline.hpp" |
1972 | 33 #ifdef TARGET_OS_FAMILY_linux |
34 # include "os_linux.inline.hpp" | |
35 #endif | |
36 #ifdef TARGET_OS_FAMILY_solaris | |
37 # include "os_solaris.inline.hpp" | |
38 #endif | |
39 #ifdef TARGET_OS_FAMILY_windows | |
40 # include "os_windows.inline.hpp" | |
41 #endif | |
3960 | 42 #ifdef TARGET_OS_FAMILY_bsd |
43 # include "os_bsd.inline.hpp" | |
44 #endif | |
1972 | 45 |
0 | 46 // The direct lock/unlock calls do not force a collection if an unlock |
47 // decrements the count to zero. Avoid calling these if at all possible. | |
48 | |
49 class GC_locker: public AllStatic { | |
50 private: | |
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51 // The _jni_lock_count keeps track of the number of threads that are |
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52 // currently in a critical region. It's only kept up to date when |
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53 // _needs_gc is true. The current value is computed during |
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54 // safepointing and decremented during the slow path of GC_locker |
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55 // unlocking. |
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56 static volatile jint _jni_lock_count; // number of jni active instances. |
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57 |
0 | 58 static volatile jint _lock_count; // number of other active instances |
59 static volatile bool _needs_gc; // heap is filling, we need a GC | |
60 // note: bool is typedef'd as jint | |
61 static volatile bool _doing_gc; // unlock_critical() is doing a GC | |
62 | |
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63 #ifdef ASSERT |
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64 // This lock count is updated for all operations and is used to |
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65 // validate the jni_lock_count that is computed during safepoints. |
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66 static volatile jint _debug_jni_lock_count; |
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67 #endif |
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68 |
0 | 69 // Accessors |
70 static bool is_jni_active() { | |
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71 assert(_needs_gc, "only valid when _needs_gc is set"); |
0 | 72 return _jni_lock_count > 0; |
73 } | |
74 | |
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75 // At a safepoint, visit all threads and count the number of active |
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76 // critical sections. This is used to ensure that all active |
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77 // critical sections are exited before a new one is started. |
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78 static void verify_critical_count() NOT_DEBUG_RETURN; |
0 | 79 |
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80 static void jni_lock(JavaThread* thread); |
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81 static void jni_unlock(JavaThread* thread); |
0 | 82 |
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83 static bool is_active_internal() { |
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84 verify_critical_count(); |
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85 return _lock_count > 0 || _jni_lock_count > 0; |
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86 } |
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87 |
0 | 88 public: |
89 // Accessors | |
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90 static bool is_active() { |
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91 assert(_needs_gc || SafepointSynchronize::is_at_safepoint(), "only read at safepoint"); |
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92 return is_active_internal(); |
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93 } |
0 | 94 static bool needs_gc() { return _needs_gc; } |
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95 |
0 | 96 // Shorthand |
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97 static bool is_active_and_needs_gc() { |
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98 // Use is_active_internal since _needs_gc can change from true to |
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99 // false outside of a safepoint, triggering the assert in |
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100 // is_active. |
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101 return needs_gc() && is_active_internal(); |
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102 } |
0 | 103 |
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104 // In debug mode track the locking state at all times |
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105 static void increment_debug_jni_lock_count() { |
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106 #ifdef ASSERT |
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107 assert(_debug_jni_lock_count >= 0, "bad value"); |
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108 Atomic::inc(&_debug_jni_lock_count); |
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109 #endif |
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110 } |
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111 static void decrement_debug_jni_lock_count() { |
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112 #ifdef ASSERT |
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113 assert(_debug_jni_lock_count > 0, "bad value"); |
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114 Atomic::dec(&_debug_jni_lock_count); |
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115 #endif |
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116 } |
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117 |
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118 // Set the current lock count |
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119 static void set_jni_lock_count(int count) { |
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120 _jni_lock_count = count; |
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121 verify_critical_count(); |
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122 } |
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123 |
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124 // Sets _needs_gc if is_active() is true. Returns is_active(). |
0 | 125 static bool check_active_before_gc(); |
126 | |
127 // Stalls the caller (who should not be in a jni critical section) | |
128 // until needs_gc() clears. Note however that needs_gc() may be | |
129 // set at a subsequent safepoint and/or cleared under the | |
130 // JNICritical_lock, so the caller may not safely assert upon | |
131 // return from this method that "!needs_gc()" since that is | |
132 // not a stable predicate. | |
133 static void stall_until_clear(); | |
134 | |
135 // Non-structured GC locking: currently needed for JNI. Use with care! | |
136 static void lock(); | |
137 static void unlock(); | |
138 | |
139 // The following two methods are used for JNI critical regions. | |
140 // If we find that we failed to perform a GC because the GC_locker | |
141 // was active, arrange for one as soon as possible by allowing | |
142 // all threads in critical regions to complete, but not allowing | |
143 // other critical regions to be entered. The reasons for that are: | |
144 // 1) a GC request won't be starved by overlapping JNI critical | |
145 // region activities, which can cause unnecessary OutOfMemory errors. | |
146 // 2) even if allocation requests can still be satisfied before GC locker | |
147 // becomes inactive, for example, in tenured generation possibly with | |
148 // heap expansion, those allocations can trigger lots of safepointing | |
149 // attempts (ineffective GC attempts) and require Heap_lock which | |
150 // slow down allocations tremendously. | |
151 // | |
152 // Note that critical regions can be nested in a single thread, so | |
153 // we must allow threads already in critical regions to continue. | |
154 // | |
155 // JNI critical regions are the only participants in this scheme | |
156 // because they are, by spec, well bounded while in a critical region. | |
157 // | |
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158 // Each of the following two method is split into a fast path and a |
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159 // slow path. JNICritical_lock is only grabbed in the slow path. |
0 | 160 // _needs_gc is initially false and every java thread will go |
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161 // through the fast path, which simply increments or decrements the |
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162 // current thread's critical count. When GC happens at a safepoint, |
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163 // GC_locker::is_active() is checked. Since there is no safepoint in |
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164 // the fast path of lock_critical() and unlock_critical(), there is |
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165 // no race condition between the fast path and GC. After _needs_gc |
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166 // is set at a safepoint, every thread will go through the slow path |
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167 // after the safepoint. Since after a safepoint, each of the |
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168 // following two methods is either entered from the method entry and |
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169 // falls into the slow path, or is resumed from the safepoints in |
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170 // the method, which only exist in the slow path. So when _needs_gc |
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171 // is set, the slow path is always taken, till _needs_gc is cleared. |
0 | 172 static void lock_critical(JavaThread* thread); |
173 static void unlock_critical(JavaThread* thread); | |
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174 |
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175 static address needs_gc_address() { return (address) &_needs_gc; } |
0 | 176 }; |
177 | |
178 | |
179 // A No_GC_Verifier object can be placed in methods where one assumes that | |
180 // no garbage collection will occur. The destructor will verify this property | |
181 // unless the constructor is called with argument false (not verifygc). | |
182 // | |
183 // The check will only be done in debug mode and if verifygc true. | |
184 | |
185 class No_GC_Verifier: public StackObj { | |
186 friend class Pause_No_GC_Verifier; | |
187 | |
188 protected: | |
189 bool _verifygc; | |
190 unsigned int _old_invocations; | |
191 | |
192 public: | |
193 #ifdef ASSERT | |
194 No_GC_Verifier(bool verifygc = true); | |
195 ~No_GC_Verifier(); | |
196 #else | |
197 No_GC_Verifier(bool verifygc = true) {} | |
198 ~No_GC_Verifier() {} | |
199 #endif | |
200 }; | |
201 | |
202 // A Pause_No_GC_Verifier is used to temporarily pause the behavior | |
203 // of a No_GC_Verifier object. If we are not in debug mode or if the | |
204 // No_GC_Verifier object has a _verifygc value of false, then there | |
205 // is nothing to do. | |
206 | |
207 class Pause_No_GC_Verifier: public StackObj { | |
208 private: | |
209 No_GC_Verifier * _ngcv; | |
210 | |
211 public: | |
212 #ifdef ASSERT | |
213 Pause_No_GC_Verifier(No_GC_Verifier * ngcv); | |
214 ~Pause_No_GC_Verifier(); | |
215 #else | |
216 Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {} | |
217 ~Pause_No_GC_Verifier() {} | |
218 #endif | |
219 }; | |
220 | |
221 | |
222 // A No_Safepoint_Verifier object will throw an assertion failure if | |
223 // the current thread passes a possible safepoint while this object is | |
224 // instantiated. A safepoint, will either be: an oop allocation, blocking | |
225 // on a Mutex or JavaLock, or executing a VM operation. | |
226 // | |
227 // If StrictSafepointChecks is turned off, it degrades into a No_GC_Verifier | |
228 // | |
229 class No_Safepoint_Verifier : public No_GC_Verifier { | |
230 friend class Pause_No_Safepoint_Verifier; | |
231 | |
232 private: | |
233 bool _activated; | |
234 Thread *_thread; | |
235 public: | |
236 #ifdef ASSERT | |
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237 No_Safepoint_Verifier(bool activated = true, bool verifygc = true ) : |
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238 No_GC_Verifier(verifygc), |
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239 _activated(activated) { |
0 | 240 _thread = Thread::current(); |
241 if (_activated) { | |
242 _thread->_allow_allocation_count++; | |
243 _thread->_allow_safepoint_count++; | |
244 } | |
245 } | |
246 | |
247 ~No_Safepoint_Verifier() { | |
248 if (_activated) { | |
249 _thread->_allow_allocation_count--; | |
250 _thread->_allow_safepoint_count--; | |
251 } | |
252 } | |
253 #else | |
254 No_Safepoint_Verifier(bool activated = true, bool verifygc = true) : No_GC_Verifier(verifygc){} | |
255 ~No_Safepoint_Verifier() {} | |
256 #endif | |
257 }; | |
258 | |
259 // A Pause_No_Safepoint_Verifier is used to temporarily pause the | |
260 // behavior of a No_Safepoint_Verifier object. If we are not in debug | |
261 // mode then there is nothing to do. If the No_Safepoint_Verifier | |
262 // object has an _activated value of false, then there is nothing to | |
263 // do for safepoint and allocation checking, but there may still be | |
264 // something to do for the underlying No_GC_Verifier object. | |
265 | |
266 class Pause_No_Safepoint_Verifier : public Pause_No_GC_Verifier { | |
267 private: | |
268 No_Safepoint_Verifier * _nsv; | |
269 | |
270 public: | |
271 #ifdef ASSERT | |
272 Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) | |
273 : Pause_No_GC_Verifier(nsv) { | |
274 | |
275 _nsv = nsv; | |
276 if (_nsv->_activated) { | |
277 _nsv->_thread->_allow_allocation_count--; | |
278 _nsv->_thread->_allow_safepoint_count--; | |
279 } | |
280 } | |
281 | |
282 ~Pause_No_Safepoint_Verifier() { | |
283 if (_nsv->_activated) { | |
284 _nsv->_thread->_allow_allocation_count++; | |
285 _nsv->_thread->_allow_safepoint_count++; | |
286 } | |
287 } | |
288 #else | |
289 Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) | |
290 : Pause_No_GC_Verifier(nsv) {} | |
291 ~Pause_No_Safepoint_Verifier() {} | |
292 #endif | |
293 }; | |
294 | |
806
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295 // A SkipGCALot object is used to elide the usual effect of gc-a-lot |
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296 // over a section of execution by a thread. Currently, it's used only to |
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297 // prevent re-entrant calls to GC. |
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298 class SkipGCALot : public StackObj { |
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299 private: |
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300 bool _saved; |
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301 Thread* _t; |
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302 |
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303 public: |
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304 #ifdef ASSERT |
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305 SkipGCALot(Thread* t) : _t(t) { |
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306 _saved = _t->skip_gcalot(); |
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307 _t->set_skip_gcalot(true); |
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308 } |
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309 |
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310 ~SkipGCALot() { |
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311 assert(_t->skip_gcalot(), "Save-restore protocol invariant"); |
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312 _t->set_skip_gcalot(_saved); |
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313 } |
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314 #else |
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315 SkipGCALot(Thread* t) { } |
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316 ~SkipGCALot() { } |
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317 #endif |
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318 }; |
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319 |
0 | 320 // JRT_LEAF currently can be called from either _thread_in_Java or |
321 // _thread_in_native mode. In _thread_in_native, it is ok | |
322 // for another thread to trigger GC. The rest of the JRT_LEAF | |
323 // rules apply. | |
324 class JRT_Leaf_Verifier : public No_Safepoint_Verifier { | |
325 static bool should_verify_GC(); | |
326 public: | |
327 #ifdef ASSERT | |
328 JRT_Leaf_Verifier(); | |
329 ~JRT_Leaf_Verifier(); | |
330 #else | |
331 JRT_Leaf_Verifier() {} | |
332 ~JRT_Leaf_Verifier() {} | |
333 #endif | |
334 }; | |
335 | |
336 // A No_Alloc_Verifier object can be placed in methods where one assumes that | |
337 // no allocation will occur. The destructor will verify this property | |
338 // unless the constructor is called with argument false (not activated). | |
339 // | |
340 // The check will only be done in debug mode and if activated. | |
341 // Note: this only makes sense at safepoints (otherwise, other threads may | |
342 // allocate concurrently.) | |
343 | |
344 class No_Alloc_Verifier : public StackObj { | |
345 private: | |
346 bool _activated; | |
347 | |
348 public: | |
349 #ifdef ASSERT | |
350 No_Alloc_Verifier(bool activated = true) { | |
351 _activated = activated; | |
352 if (_activated) Thread::current()->_allow_allocation_count++; | |
353 } | |
354 | |
355 ~No_Alloc_Verifier() { | |
356 if (_activated) Thread::current()->_allow_allocation_count--; | |
357 } | |
358 #else | |
359 No_Alloc_Verifier(bool activated = true) {} | |
360 ~No_Alloc_Verifier() {} | |
361 #endif | |
362 }; | |
1972 | 363 |
364 #endif // SHARE_VM_MEMORY_GCLOCKER_HPP |