Mercurial > hg > graal-jvmci-8
annotate src/share/vm/memory/gcLocker.hpp @ 1721:413ad0331a0c
6977924: Changes for 6975078 produce build error with certain gcc versions
Summary: The changes introduced for 6975078 assign badHeapOopVal to the _allocation field in the ResourceObj class. In 32 bit linux builds with certain versions of gcc this assignment will be flagged as an error while compiling allocation.cpp. In 32 bit builds the constant value badHeapOopVal (which is cast to an intptr_t) is negative. The _allocation field is typed as an unsigned intptr_t and gcc catches this as an error.
Reviewed-by: jcoomes, ysr, phh
| author | johnc |
|---|---|
| date | Wed, 18 Aug 2010 10:59:06 -0700 |
| parents | c18cbe5936b8 |
| children | f95d63e2154a |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 1997, 2009, 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 | |
| 25 // The direct lock/unlock calls do not force a collection if an unlock | |
| 26 // decrements the count to zero. Avoid calling these if at all possible. | |
| 27 | |
| 28 class GC_locker: public AllStatic { | |
| 29 private: | |
| 30 static volatile jint _jni_lock_count; // number of jni active instances | |
| 31 static volatile jint _lock_count; // number of other active instances | |
| 32 static volatile bool _needs_gc; // heap is filling, we need a GC | |
| 33 // note: bool is typedef'd as jint | |
| 34 static volatile bool _doing_gc; // unlock_critical() is doing a GC | |
| 35 | |
| 36 // Accessors | |
| 37 static bool is_jni_active() { | |
| 38 return _jni_lock_count > 0; | |
| 39 } | |
| 40 | |
| 41 static void set_needs_gc() { | |
| 42 assert(SafepointSynchronize::is_at_safepoint(), | |
| 43 "needs_gc is only set at a safepoint"); | |
| 44 _needs_gc = true; | |
| 45 } | |
| 46 | |
| 47 static void clear_needs_gc() { | |
| 48 assert_lock_strong(JNICritical_lock); | |
| 49 _needs_gc = false; | |
| 50 } | |
| 51 | |
| 52 static void jni_lock() { | |
| 53 Atomic::inc(&_jni_lock_count); | |
| 54 CHECK_UNHANDLED_OOPS_ONLY( | |
| 55 if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count++; }) | |
| 56 assert(Universe::heap() == NULL || !Universe::heap()->is_gc_active(), | |
| 57 "locking failed"); | |
| 58 } | |
| 59 | |
| 60 static void jni_unlock() { | |
| 61 Atomic::dec(&_jni_lock_count); | |
| 62 CHECK_UNHANDLED_OOPS_ONLY( | |
| 63 if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count--; }) | |
| 64 } | |
| 65 | |
| 66 static void jni_lock_slow(); | |
| 67 static void jni_unlock_slow(); | |
| 68 | |
| 69 public: | |
| 70 // Accessors | |
| 71 static bool is_active(); | |
| 72 static bool needs_gc() { return _needs_gc; } | |
| 73 // Shorthand | |
| 74 static bool is_active_and_needs_gc() { return is_active() && needs_gc();} | |
| 75 | |
| 76 // Calls set_needs_gc() if is_active() is true. Returns is_active(). | |
| 77 static bool check_active_before_gc(); | |
| 78 | |
| 79 // Stalls the caller (who should not be in a jni critical section) | |
| 80 // until needs_gc() clears. Note however that needs_gc() may be | |
| 81 // set at a subsequent safepoint and/or cleared under the | |
| 82 // JNICritical_lock, so the caller may not safely assert upon | |
| 83 // return from this method that "!needs_gc()" since that is | |
| 84 // not a stable predicate. | |
| 85 static void stall_until_clear(); | |
| 86 | |
| 87 // Non-structured GC locking: currently needed for JNI. Use with care! | |
| 88 static void lock(); | |
| 89 static void unlock(); | |
| 90 | |
| 91 // The following two methods are used for JNI critical regions. | |
| 92 // If we find that we failed to perform a GC because the GC_locker | |
| 93 // was active, arrange for one as soon as possible by allowing | |
| 94 // all threads in critical regions to complete, but not allowing | |
| 95 // other critical regions to be entered. The reasons for that are: | |
| 96 // 1) a GC request won't be starved by overlapping JNI critical | |
| 97 // region activities, which can cause unnecessary OutOfMemory errors. | |
| 98 // 2) even if allocation requests can still be satisfied before GC locker | |
| 99 // becomes inactive, for example, in tenured generation possibly with | |
| 100 // heap expansion, those allocations can trigger lots of safepointing | |
| 101 // attempts (ineffective GC attempts) and require Heap_lock which | |
| 102 // slow down allocations tremendously. | |
| 103 // | |
| 104 // Note that critical regions can be nested in a single thread, so | |
| 105 // we must allow threads already in critical regions to continue. | |
| 106 // | |
| 107 // JNI critical regions are the only participants in this scheme | |
| 108 // because they are, by spec, well bounded while in a critical region. | |
| 109 // | |
| 110 // Each of the following two method is split into a fast path and a slow | |
| 111 // path. JNICritical_lock is only grabbed in the slow path. | |
| 112 // _needs_gc is initially false and every java thread will go | |
| 113 // through the fast path (which does the same thing as the slow path | |
| 114 // when _needs_gc is false). When GC happens at a safepoint, | |
| 115 // GC_locker::is_active() is checked. Since there is no safepoint in the | |
| 116 // fast path of lock_critical() and unlock_critical(), there is no race | |
| 117 // condition between the fast path and GC. After _needs_gc is set at a | |
| 118 // safepoint, every thread will go through the slow path after the safepoint. | |
| 119 // Since after a safepoint, each of the following two methods is either | |
| 120 // entered from the method entry and falls into the slow path, or is | |
| 121 // resumed from the safepoints in the method, which only exist in the slow | |
| 122 // path. So when _needs_gc is set, the slow path is always taken, till | |
| 123 // _needs_gc is cleared. | |
| 124 static void lock_critical(JavaThread* thread); | |
| 125 static void unlock_critical(JavaThread* thread); | |
| 126 }; | |
| 127 | |
| 128 | |
| 129 // A No_GC_Verifier object can be placed in methods where one assumes that | |
| 130 // no garbage collection will occur. The destructor will verify this property | |
| 131 // unless the constructor is called with argument false (not verifygc). | |
| 132 // | |
| 133 // The check will only be done in debug mode and if verifygc true. | |
| 134 | |
| 135 class No_GC_Verifier: public StackObj { | |
| 136 friend class Pause_No_GC_Verifier; | |
| 137 | |
| 138 protected: | |
| 139 bool _verifygc; | |
| 140 unsigned int _old_invocations; | |
| 141 | |
| 142 public: | |
| 143 #ifdef ASSERT | |
| 144 No_GC_Verifier(bool verifygc = true); | |
| 145 ~No_GC_Verifier(); | |
| 146 #else | |
| 147 No_GC_Verifier(bool verifygc = true) {} | |
| 148 ~No_GC_Verifier() {} | |
| 149 #endif | |
| 150 }; | |
| 151 | |
| 152 // A Pause_No_GC_Verifier is used to temporarily pause the behavior | |
| 153 // of a No_GC_Verifier object. If we are not in debug mode or if the | |
| 154 // No_GC_Verifier object has a _verifygc value of false, then there | |
| 155 // is nothing to do. | |
| 156 | |
| 157 class Pause_No_GC_Verifier: public StackObj { | |
| 158 private: | |
| 159 No_GC_Verifier * _ngcv; | |
| 160 | |
| 161 public: | |
| 162 #ifdef ASSERT | |
| 163 Pause_No_GC_Verifier(No_GC_Verifier * ngcv); | |
| 164 ~Pause_No_GC_Verifier(); | |
| 165 #else | |
| 166 Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {} | |
| 167 ~Pause_No_GC_Verifier() {} | |
| 168 #endif | |
| 169 }; | |
| 170 | |
| 171 | |
| 172 // A No_Safepoint_Verifier object will throw an assertion failure if | |
| 173 // the current thread passes a possible safepoint while this object is | |
| 174 // instantiated. A safepoint, will either be: an oop allocation, blocking | |
| 175 // on a Mutex or JavaLock, or executing a VM operation. | |
| 176 // | |
| 177 // If StrictSafepointChecks is turned off, it degrades into a No_GC_Verifier | |
| 178 // | |
| 179 class No_Safepoint_Verifier : public No_GC_Verifier { | |
| 180 friend class Pause_No_Safepoint_Verifier; | |
| 181 | |
| 182 private: | |
| 183 bool _activated; | |
| 184 Thread *_thread; | |
| 185 public: | |
| 186 #ifdef ASSERT | |
|
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187 No_Safepoint_Verifier(bool activated = true, bool verifygc = true ) : |
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188 No_GC_Verifier(verifygc), |
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189 _activated(activated) { |
| 0 | 190 _thread = Thread::current(); |
| 191 if (_activated) { | |
| 192 _thread->_allow_allocation_count++; | |
| 193 _thread->_allow_safepoint_count++; | |
| 194 } | |
| 195 } | |
| 196 | |
| 197 ~No_Safepoint_Verifier() { | |
| 198 if (_activated) { | |
| 199 _thread->_allow_allocation_count--; | |
| 200 _thread->_allow_safepoint_count--; | |
| 201 } | |
| 202 } | |
| 203 #else | |
| 204 No_Safepoint_Verifier(bool activated = true, bool verifygc = true) : No_GC_Verifier(verifygc){} | |
| 205 ~No_Safepoint_Verifier() {} | |
| 206 #endif | |
| 207 }; | |
| 208 | |
| 209 // A Pause_No_Safepoint_Verifier is used to temporarily pause the | |
| 210 // behavior of a No_Safepoint_Verifier object. If we are not in debug | |
| 211 // mode then there is nothing to do. If the No_Safepoint_Verifier | |
| 212 // object has an _activated value of false, then there is nothing to | |
| 213 // do for safepoint and allocation checking, but there may still be | |
| 214 // something to do for the underlying No_GC_Verifier object. | |
| 215 | |
| 216 class Pause_No_Safepoint_Verifier : public Pause_No_GC_Verifier { | |
| 217 private: | |
| 218 No_Safepoint_Verifier * _nsv; | |
| 219 | |
| 220 public: | |
| 221 #ifdef ASSERT | |
| 222 Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) | |
| 223 : Pause_No_GC_Verifier(nsv) { | |
| 224 | |
| 225 _nsv = nsv; | |
| 226 if (_nsv->_activated) { | |
| 227 _nsv->_thread->_allow_allocation_count--; | |
| 228 _nsv->_thread->_allow_safepoint_count--; | |
| 229 } | |
| 230 } | |
| 231 | |
| 232 ~Pause_No_Safepoint_Verifier() { | |
| 233 if (_nsv->_activated) { | |
| 234 _nsv->_thread->_allow_allocation_count++; | |
| 235 _nsv->_thread->_allow_safepoint_count++; | |
| 236 } | |
| 237 } | |
| 238 #else | |
| 239 Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) | |
| 240 : Pause_No_GC_Verifier(nsv) {} | |
| 241 ~Pause_No_Safepoint_Verifier() {} | |
| 242 #endif | |
| 243 }; | |
| 244 | |
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245 // A SkipGCALot object is used to elide the usual effect of gc-a-lot |
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246 // over a section of execution by a thread. Currently, it's used only to |
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247 // prevent re-entrant calls to GC. |
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248 class SkipGCALot : public StackObj { |
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249 private: |
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250 bool _saved; |
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251 Thread* _t; |
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252 |
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253 public: |
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254 #ifdef ASSERT |
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255 SkipGCALot(Thread* t) : _t(t) { |
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256 _saved = _t->skip_gcalot(); |
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257 _t->set_skip_gcalot(true); |
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258 } |
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259 |
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260 ~SkipGCALot() { |
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261 assert(_t->skip_gcalot(), "Save-restore protocol invariant"); |
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262 _t->set_skip_gcalot(_saved); |
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263 } |
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264 #else |
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265 SkipGCALot(Thread* t) { } |
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266 ~SkipGCALot() { } |
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267 #endif |
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268 }; |
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269 |
| 0 | 270 // JRT_LEAF currently can be called from either _thread_in_Java or |
| 271 // _thread_in_native mode. In _thread_in_native, it is ok | |
| 272 // for another thread to trigger GC. The rest of the JRT_LEAF | |
| 273 // rules apply. | |
| 274 class JRT_Leaf_Verifier : public No_Safepoint_Verifier { | |
| 275 static bool should_verify_GC(); | |
| 276 public: | |
| 277 #ifdef ASSERT | |
| 278 JRT_Leaf_Verifier(); | |
| 279 ~JRT_Leaf_Verifier(); | |
| 280 #else | |
| 281 JRT_Leaf_Verifier() {} | |
| 282 ~JRT_Leaf_Verifier() {} | |
| 283 #endif | |
| 284 }; | |
| 285 | |
| 286 // A No_Alloc_Verifier object can be placed in methods where one assumes that | |
| 287 // no allocation will occur. The destructor will verify this property | |
| 288 // unless the constructor is called with argument false (not activated). | |
| 289 // | |
| 290 // The check will only be done in debug mode and if activated. | |
| 291 // Note: this only makes sense at safepoints (otherwise, other threads may | |
| 292 // allocate concurrently.) | |
| 293 | |
| 294 class No_Alloc_Verifier : public StackObj { | |
| 295 private: | |
| 296 bool _activated; | |
| 297 | |
| 298 public: | |
| 299 #ifdef ASSERT | |
| 300 No_Alloc_Verifier(bool activated = true) { | |
| 301 _activated = activated; | |
| 302 if (_activated) Thread::current()->_allow_allocation_count++; | |
| 303 } | |
| 304 | |
| 305 ~No_Alloc_Verifier() { | |
| 306 if (_activated) Thread::current()->_allow_allocation_count--; | |
| 307 } | |
| 308 #else | |
| 309 No_Alloc_Verifier(bool activated = true) {} | |
| 310 ~No_Alloc_Verifier() {} | |
| 311 #endif | |
| 312 }; |