Mercurial > hg > graal-compiler
annotate src/share/vm/memory/gcLocker.hpp @ 4712:e7dead7e90af
7117303: VM uses non-monotonic time source and complains that it is non-monotonic
Summary: Replaces calls to os::javaTimeMillis(), which does not (and cannot) guarantee monotonicity, in GC code to an equivalent expression that uses os::javaTimeNanos(). os::javaTimeNanos is guaranteed monotonically non-decreasing if the underlying platform provides a monotonic time source. Changes in OS files are to make use of the newly defined constants in globalDefinitions.hpp.
Reviewed-by: dholmes, ysr
author | johnc |
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date | Mon, 19 Dec 2011 10:02:05 -0800 |
parents | f08d439fab8c |
children | 1a2723f7ad8e |
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 | |
3960 | 44 #ifdef TARGET_OS_FAMILY_bsd |
45 # include "os_bsd.inline.hpp" | |
46 # include "thread_bsd.inline.hpp" | |
47 #endif | |
1972 | 48 |
0 | 49 // The direct lock/unlock calls do not force a collection if an unlock |
50 // decrements the count to zero. Avoid calling these if at all possible. | |
51 | |
52 class GC_locker: public AllStatic { | |
53 private: | |
54 static volatile jint _jni_lock_count; // number of jni active instances | |
55 static volatile jint _lock_count; // number of other active instances | |
56 static volatile bool _needs_gc; // heap is filling, we need a GC | |
57 // note: bool is typedef'd as jint | |
58 static volatile bool _doing_gc; // unlock_critical() is doing a GC | |
59 | |
60 // Accessors | |
61 static bool is_jni_active() { | |
62 return _jni_lock_count > 0; | |
63 } | |
64 | |
65 static void set_needs_gc() { | |
66 assert(SafepointSynchronize::is_at_safepoint(), | |
67 "needs_gc is only set at a safepoint"); | |
68 _needs_gc = true; | |
69 } | |
70 | |
71 static void clear_needs_gc() { | |
72 assert_lock_strong(JNICritical_lock); | |
73 _needs_gc = false; | |
74 } | |
75 | |
76 static void jni_lock() { | |
77 Atomic::inc(&_jni_lock_count); | |
78 CHECK_UNHANDLED_OOPS_ONLY( | |
79 if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count++; }) | |
80 assert(Universe::heap() == NULL || !Universe::heap()->is_gc_active(), | |
81 "locking failed"); | |
82 } | |
83 | |
84 static void jni_unlock() { | |
85 Atomic::dec(&_jni_lock_count); | |
86 CHECK_UNHANDLED_OOPS_ONLY( | |
87 if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count--; }) | |
88 } | |
89 | |
90 static void jni_lock_slow(); | |
91 static void jni_unlock_slow(); | |
92 | |
93 public: | |
94 // Accessors | |
95 static bool is_active(); | |
96 static bool needs_gc() { return _needs_gc; } | |
97 // Shorthand | |
98 static bool is_active_and_needs_gc() { return is_active() && needs_gc();} | |
99 | |
100 // Calls set_needs_gc() if is_active() is true. Returns is_active(). | |
101 static bool check_active_before_gc(); | |
102 | |
103 // Stalls the caller (who should not be in a jni critical section) | |
104 // until needs_gc() clears. Note however that needs_gc() may be | |
105 // set at a subsequent safepoint and/or cleared under the | |
106 // JNICritical_lock, so the caller may not safely assert upon | |
107 // return from this method that "!needs_gc()" since that is | |
108 // not a stable predicate. | |
109 static void stall_until_clear(); | |
110 | |
111 // Non-structured GC locking: currently needed for JNI. Use with care! | |
112 static void lock(); | |
113 static void unlock(); | |
114 | |
115 // The following two methods are used for JNI critical regions. | |
116 // If we find that we failed to perform a GC because the GC_locker | |
117 // was active, arrange for one as soon as possible by allowing | |
118 // all threads in critical regions to complete, but not allowing | |
119 // other critical regions to be entered. The reasons for that are: | |
120 // 1) a GC request won't be starved by overlapping JNI critical | |
121 // region activities, which can cause unnecessary OutOfMemory errors. | |
122 // 2) even if allocation requests can still be satisfied before GC locker | |
123 // becomes inactive, for example, in tenured generation possibly with | |
124 // heap expansion, those allocations can trigger lots of safepointing | |
125 // attempts (ineffective GC attempts) and require Heap_lock which | |
126 // slow down allocations tremendously. | |
127 // | |
128 // Note that critical regions can be nested in a single thread, so | |
129 // we must allow threads already in critical regions to continue. | |
130 // | |
131 // JNI critical regions are the only participants in this scheme | |
132 // because they are, by spec, well bounded while in a critical region. | |
133 // | |
134 // Each of the following two method is split into a fast path and a slow | |
135 // path. JNICritical_lock is only grabbed in the slow path. | |
136 // _needs_gc is initially false and every java thread will go | |
137 // through the fast path (which does the same thing as the slow path | |
138 // when _needs_gc is false). When GC happens at a safepoint, | |
139 // GC_locker::is_active() is checked. Since there is no safepoint in the | |
140 // fast path of lock_critical() and unlock_critical(), there is no race | |
141 // condition between the fast path and GC. After _needs_gc is set at a | |
142 // safepoint, every thread will go through the slow path after the safepoint. | |
143 // Since after a safepoint, each of the following two methods is either | |
144 // entered from the method entry and falls into the slow path, or is | |
145 // resumed from the safepoints in the method, which only exist in the slow | |
146 // path. So when _needs_gc is set, the slow path is always taken, till | |
147 // _needs_gc is cleared. | |
148 static void lock_critical(JavaThread* thread); | |
149 static void unlock_critical(JavaThread* thread); | |
150 }; | |
151 | |
152 | |
153 // A No_GC_Verifier object can be placed in methods where one assumes that | |
154 // no garbage collection will occur. The destructor will verify this property | |
155 // unless the constructor is called with argument false (not verifygc). | |
156 // | |
157 // The check will only be done in debug mode and if verifygc true. | |
158 | |
159 class No_GC_Verifier: public StackObj { | |
160 friend class Pause_No_GC_Verifier; | |
161 | |
162 protected: | |
163 bool _verifygc; | |
164 unsigned int _old_invocations; | |
165 | |
166 public: | |
167 #ifdef ASSERT | |
168 No_GC_Verifier(bool verifygc = true); | |
169 ~No_GC_Verifier(); | |
170 #else | |
171 No_GC_Verifier(bool verifygc = true) {} | |
172 ~No_GC_Verifier() {} | |
173 #endif | |
174 }; | |
175 | |
176 // A Pause_No_GC_Verifier is used to temporarily pause the behavior | |
177 // of a No_GC_Verifier object. If we are not in debug mode or if the | |
178 // No_GC_Verifier object has a _verifygc value of false, then there | |
179 // is nothing to do. | |
180 | |
181 class Pause_No_GC_Verifier: public StackObj { | |
182 private: | |
183 No_GC_Verifier * _ngcv; | |
184 | |
185 public: | |
186 #ifdef ASSERT | |
187 Pause_No_GC_Verifier(No_GC_Verifier * ngcv); | |
188 ~Pause_No_GC_Verifier(); | |
189 #else | |
190 Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {} | |
191 ~Pause_No_GC_Verifier() {} | |
192 #endif | |
193 }; | |
194 | |
195 | |
196 // A No_Safepoint_Verifier object will throw an assertion failure if | |
197 // the current thread passes a possible safepoint while this object is | |
198 // instantiated. A safepoint, will either be: an oop allocation, blocking | |
199 // on a Mutex or JavaLock, or executing a VM operation. | |
200 // | |
201 // If StrictSafepointChecks is turned off, it degrades into a No_GC_Verifier | |
202 // | |
203 class No_Safepoint_Verifier : public No_GC_Verifier { | |
204 friend class Pause_No_Safepoint_Verifier; | |
205 | |
206 private: | |
207 bool _activated; | |
208 Thread *_thread; | |
209 public: | |
210 #ifdef ASSERT | |
98
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211 No_Safepoint_Verifier(bool activated = true, bool verifygc = true ) : |
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212 No_GC_Verifier(verifygc), |
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213 _activated(activated) { |
0 | 214 _thread = Thread::current(); |
215 if (_activated) { | |
216 _thread->_allow_allocation_count++; | |
217 _thread->_allow_safepoint_count++; | |
218 } | |
219 } | |
220 | |
221 ~No_Safepoint_Verifier() { | |
222 if (_activated) { | |
223 _thread->_allow_allocation_count--; | |
224 _thread->_allow_safepoint_count--; | |
225 } | |
226 } | |
227 #else | |
228 No_Safepoint_Verifier(bool activated = true, bool verifygc = true) : No_GC_Verifier(verifygc){} | |
229 ~No_Safepoint_Verifier() {} | |
230 #endif | |
231 }; | |
232 | |
233 // A Pause_No_Safepoint_Verifier is used to temporarily pause the | |
234 // behavior of a No_Safepoint_Verifier object. If we are not in debug | |
235 // mode then there is nothing to do. If the No_Safepoint_Verifier | |
236 // object has an _activated value of false, then there is nothing to | |
237 // do for safepoint and allocation checking, but there may still be | |
238 // something to do for the underlying No_GC_Verifier object. | |
239 | |
240 class Pause_No_Safepoint_Verifier : public Pause_No_GC_Verifier { | |
241 private: | |
242 No_Safepoint_Verifier * _nsv; | |
243 | |
244 public: | |
245 #ifdef ASSERT | |
246 Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) | |
247 : Pause_No_GC_Verifier(nsv) { | |
248 | |
249 _nsv = nsv; | |
250 if (_nsv->_activated) { | |
251 _nsv->_thread->_allow_allocation_count--; | |
252 _nsv->_thread->_allow_safepoint_count--; | |
253 } | |
254 } | |
255 | |
256 ~Pause_No_Safepoint_Verifier() { | |
257 if (_nsv->_activated) { | |
258 _nsv->_thread->_allow_allocation_count++; | |
259 _nsv->_thread->_allow_safepoint_count++; | |
260 } | |
261 } | |
262 #else | |
263 Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) | |
264 : Pause_No_GC_Verifier(nsv) {} | |
265 ~Pause_No_Safepoint_Verifier() {} | |
266 #endif | |
267 }; | |
268 | |
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269 // A SkipGCALot object is used to elide the usual effect of gc-a-lot |
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270 // over a section of execution by a thread. Currently, it's used only to |
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271 // prevent re-entrant calls to GC. |
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272 class SkipGCALot : public StackObj { |
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273 private: |
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274 bool _saved; |
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275 Thread* _t; |
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276 |
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277 public: |
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278 #ifdef ASSERT |
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279 SkipGCALot(Thread* t) : _t(t) { |
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280 _saved = _t->skip_gcalot(); |
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281 _t->set_skip_gcalot(true); |
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282 } |
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283 |
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284 ~SkipGCALot() { |
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285 assert(_t->skip_gcalot(), "Save-restore protocol invariant"); |
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286 _t->set_skip_gcalot(_saved); |
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287 } |
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288 #else |
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289 SkipGCALot(Thread* t) { } |
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290 ~SkipGCALot() { } |
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291 #endif |
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292 }; |
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293 |
0 | 294 // JRT_LEAF currently can be called from either _thread_in_Java or |
295 // _thread_in_native mode. In _thread_in_native, it is ok | |
296 // for another thread to trigger GC. The rest of the JRT_LEAF | |
297 // rules apply. | |
298 class JRT_Leaf_Verifier : public No_Safepoint_Verifier { | |
299 static bool should_verify_GC(); | |
300 public: | |
301 #ifdef ASSERT | |
302 JRT_Leaf_Verifier(); | |
303 ~JRT_Leaf_Verifier(); | |
304 #else | |
305 JRT_Leaf_Verifier() {} | |
306 ~JRT_Leaf_Verifier() {} | |
307 #endif | |
308 }; | |
309 | |
310 // A No_Alloc_Verifier object can be placed in methods where one assumes that | |
311 // no allocation will occur. The destructor will verify this property | |
312 // unless the constructor is called with argument false (not activated). | |
313 // | |
314 // The check will only be done in debug mode and if activated. | |
315 // Note: this only makes sense at safepoints (otherwise, other threads may | |
316 // allocate concurrently.) | |
317 | |
318 class No_Alloc_Verifier : public StackObj { | |
319 private: | |
320 bool _activated; | |
321 | |
322 public: | |
323 #ifdef ASSERT | |
324 No_Alloc_Verifier(bool activated = true) { | |
325 _activated = activated; | |
326 if (_activated) Thread::current()->_allow_allocation_count++; | |
327 } | |
328 | |
329 ~No_Alloc_Verifier() { | |
330 if (_activated) Thread::current()->_allow_allocation_count--; | |
331 } | |
332 #else | |
333 No_Alloc_Verifier(bool activated = true) {} | |
334 ~No_Alloc_Verifier() {} | |
335 #endif | |
336 }; | |
1972 | 337 |
338 #endif // SHARE_VM_MEMORY_GCLOCKER_HPP |