Thu, 12 Jun 2008 13:50:55 -0700
Merge
duke@435 | 1 | /* |
duke@435 | 2 | * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved. |
duke@435 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
duke@435 | 4 | * |
duke@435 | 5 | * This code is free software; you can redistribute it and/or modify it |
duke@435 | 6 | * under the terms of the GNU General Public License version 2 only, as |
duke@435 | 7 | * published by the Free Software Foundation. |
duke@435 | 8 | * |
duke@435 | 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
duke@435 | 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
duke@435 | 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
duke@435 | 12 | * version 2 for more details (a copy is included in the LICENSE file that |
duke@435 | 13 | * accompanied this code). |
duke@435 | 14 | * |
duke@435 | 15 | * You should have received a copy of the GNU General Public License version |
duke@435 | 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
duke@435 | 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
duke@435 | 18 | * |
duke@435 | 19 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
duke@435 | 20 | * CA 95054 USA or visit www.sun.com if you need additional information or |
duke@435 | 21 | * have any questions. |
duke@435 | 22 | * |
duke@435 | 23 | */ |
duke@435 | 24 | |
duke@435 | 25 | // The direct lock/unlock calls do not force a collection if an unlock |
duke@435 | 26 | // decrements the count to zero. Avoid calling these if at all possible. |
duke@435 | 27 | |
duke@435 | 28 | class GC_locker: public AllStatic { |
duke@435 | 29 | private: |
duke@435 | 30 | static volatile jint _jni_lock_count; // number of jni active instances |
duke@435 | 31 | static volatile jint _lock_count; // number of other active instances |
duke@435 | 32 | static volatile bool _needs_gc; // heap is filling, we need a GC |
duke@435 | 33 | // note: bool is typedef'd as jint |
duke@435 | 34 | static volatile bool _doing_gc; // unlock_critical() is doing a GC |
duke@435 | 35 | |
duke@435 | 36 | // Accessors |
duke@435 | 37 | static bool is_jni_active() { |
duke@435 | 38 | return _jni_lock_count > 0; |
duke@435 | 39 | } |
duke@435 | 40 | |
duke@435 | 41 | static void set_needs_gc() { |
duke@435 | 42 | assert(SafepointSynchronize::is_at_safepoint(), |
duke@435 | 43 | "needs_gc is only set at a safepoint"); |
duke@435 | 44 | _needs_gc = true; |
duke@435 | 45 | } |
duke@435 | 46 | |
duke@435 | 47 | static void clear_needs_gc() { |
duke@435 | 48 | assert_lock_strong(JNICritical_lock); |
duke@435 | 49 | _needs_gc = false; |
duke@435 | 50 | } |
duke@435 | 51 | |
duke@435 | 52 | static void jni_lock() { |
duke@435 | 53 | Atomic::inc(&_jni_lock_count); |
duke@435 | 54 | CHECK_UNHANDLED_OOPS_ONLY( |
duke@435 | 55 | if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count++; }) |
duke@435 | 56 | assert(Universe::heap() == NULL || !Universe::heap()->is_gc_active(), |
duke@435 | 57 | "locking failed"); |
duke@435 | 58 | } |
duke@435 | 59 | |
duke@435 | 60 | static void jni_unlock() { |
duke@435 | 61 | Atomic::dec(&_jni_lock_count); |
duke@435 | 62 | CHECK_UNHANDLED_OOPS_ONLY( |
duke@435 | 63 | if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count--; }) |
duke@435 | 64 | } |
duke@435 | 65 | |
duke@435 | 66 | static void jni_lock_slow(); |
duke@435 | 67 | static void jni_unlock_slow(); |
duke@435 | 68 | |
duke@435 | 69 | public: |
duke@435 | 70 | // Accessors |
duke@435 | 71 | static bool is_active(); |
duke@435 | 72 | static bool needs_gc() { return _needs_gc; } |
duke@435 | 73 | // Shorthand |
duke@435 | 74 | static bool is_active_and_needs_gc() { return is_active() && needs_gc();} |
duke@435 | 75 | |
duke@435 | 76 | // Calls set_needs_gc() if is_active() is true. Returns is_active(). |
duke@435 | 77 | static bool check_active_before_gc(); |
duke@435 | 78 | |
duke@435 | 79 | // Stalls the caller (who should not be in a jni critical section) |
duke@435 | 80 | // until needs_gc() clears. Note however that needs_gc() may be |
duke@435 | 81 | // set at a subsequent safepoint and/or cleared under the |
duke@435 | 82 | // JNICritical_lock, so the caller may not safely assert upon |
duke@435 | 83 | // return from this method that "!needs_gc()" since that is |
duke@435 | 84 | // not a stable predicate. |
duke@435 | 85 | static void stall_until_clear(); |
duke@435 | 86 | |
duke@435 | 87 | // Non-structured GC locking: currently needed for JNI. Use with care! |
duke@435 | 88 | static void lock(); |
duke@435 | 89 | static void unlock(); |
duke@435 | 90 | |
duke@435 | 91 | // The following two methods are used for JNI critical regions. |
duke@435 | 92 | // If we find that we failed to perform a GC because the GC_locker |
duke@435 | 93 | // was active, arrange for one as soon as possible by allowing |
duke@435 | 94 | // all threads in critical regions to complete, but not allowing |
duke@435 | 95 | // other critical regions to be entered. The reasons for that are: |
duke@435 | 96 | // 1) a GC request won't be starved by overlapping JNI critical |
duke@435 | 97 | // region activities, which can cause unnecessary OutOfMemory errors. |
duke@435 | 98 | // 2) even if allocation requests can still be satisfied before GC locker |
duke@435 | 99 | // becomes inactive, for example, in tenured generation possibly with |
duke@435 | 100 | // heap expansion, those allocations can trigger lots of safepointing |
duke@435 | 101 | // attempts (ineffective GC attempts) and require Heap_lock which |
duke@435 | 102 | // slow down allocations tremendously. |
duke@435 | 103 | // |
duke@435 | 104 | // Note that critical regions can be nested in a single thread, so |
duke@435 | 105 | // we must allow threads already in critical regions to continue. |
duke@435 | 106 | // |
duke@435 | 107 | // JNI critical regions are the only participants in this scheme |
duke@435 | 108 | // because they are, by spec, well bounded while in a critical region. |
duke@435 | 109 | // |
duke@435 | 110 | // Each of the following two method is split into a fast path and a slow |
duke@435 | 111 | // path. JNICritical_lock is only grabbed in the slow path. |
duke@435 | 112 | // _needs_gc is initially false and every java thread will go |
duke@435 | 113 | // through the fast path (which does the same thing as the slow path |
duke@435 | 114 | // when _needs_gc is false). When GC happens at a safepoint, |
duke@435 | 115 | // GC_locker::is_active() is checked. Since there is no safepoint in the |
duke@435 | 116 | // fast path of lock_critical() and unlock_critical(), there is no race |
duke@435 | 117 | // condition between the fast path and GC. After _needs_gc is set at a |
duke@435 | 118 | // safepoint, every thread will go through the slow path after the safepoint. |
duke@435 | 119 | // Since after a safepoint, each of the following two methods is either |
duke@435 | 120 | // entered from the method entry and falls into the slow path, or is |
duke@435 | 121 | // resumed from the safepoints in the method, which only exist in the slow |
duke@435 | 122 | // path. So when _needs_gc is set, the slow path is always taken, till |
duke@435 | 123 | // _needs_gc is cleared. |
duke@435 | 124 | static void lock_critical(JavaThread* thread); |
duke@435 | 125 | static void unlock_critical(JavaThread* thread); |
duke@435 | 126 | }; |
duke@435 | 127 | |
duke@435 | 128 | |
duke@435 | 129 | // A No_GC_Verifier object can be placed in methods where one assumes that |
duke@435 | 130 | // no garbage collection will occur. The destructor will verify this property |
duke@435 | 131 | // unless the constructor is called with argument false (not verifygc). |
duke@435 | 132 | // |
duke@435 | 133 | // The check will only be done in debug mode and if verifygc true. |
duke@435 | 134 | |
duke@435 | 135 | class No_GC_Verifier: public StackObj { |
duke@435 | 136 | friend class Pause_No_GC_Verifier; |
duke@435 | 137 | |
duke@435 | 138 | protected: |
duke@435 | 139 | bool _verifygc; |
duke@435 | 140 | unsigned int _old_invocations; |
duke@435 | 141 | |
duke@435 | 142 | public: |
duke@435 | 143 | #ifdef ASSERT |
duke@435 | 144 | No_GC_Verifier(bool verifygc = true); |
duke@435 | 145 | ~No_GC_Verifier(); |
duke@435 | 146 | #else |
duke@435 | 147 | No_GC_Verifier(bool verifygc = true) {} |
duke@435 | 148 | ~No_GC_Verifier() {} |
duke@435 | 149 | #endif |
duke@435 | 150 | }; |
duke@435 | 151 | |
duke@435 | 152 | // A Pause_No_GC_Verifier is used to temporarily pause the behavior |
duke@435 | 153 | // of a No_GC_Verifier object. If we are not in debug mode or if the |
duke@435 | 154 | // No_GC_Verifier object has a _verifygc value of false, then there |
duke@435 | 155 | // is nothing to do. |
duke@435 | 156 | |
duke@435 | 157 | class Pause_No_GC_Verifier: public StackObj { |
duke@435 | 158 | private: |
duke@435 | 159 | No_GC_Verifier * _ngcv; |
duke@435 | 160 | |
duke@435 | 161 | public: |
duke@435 | 162 | #ifdef ASSERT |
duke@435 | 163 | Pause_No_GC_Verifier(No_GC_Verifier * ngcv); |
duke@435 | 164 | ~Pause_No_GC_Verifier(); |
duke@435 | 165 | #else |
duke@435 | 166 | Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {} |
duke@435 | 167 | ~Pause_No_GC_Verifier() {} |
duke@435 | 168 | #endif |
duke@435 | 169 | }; |
duke@435 | 170 | |
duke@435 | 171 | |
duke@435 | 172 | // A No_Safepoint_Verifier object will throw an assertion failure if |
duke@435 | 173 | // the current thread passes a possible safepoint while this object is |
duke@435 | 174 | // instantiated. A safepoint, will either be: an oop allocation, blocking |
duke@435 | 175 | // on a Mutex or JavaLock, or executing a VM operation. |
duke@435 | 176 | // |
duke@435 | 177 | // If StrictSafepointChecks is turned off, it degrades into a No_GC_Verifier |
duke@435 | 178 | // |
duke@435 | 179 | class No_Safepoint_Verifier : public No_GC_Verifier { |
duke@435 | 180 | friend class Pause_No_Safepoint_Verifier; |
duke@435 | 181 | |
duke@435 | 182 | private: |
duke@435 | 183 | bool _activated; |
duke@435 | 184 | Thread *_thread; |
duke@435 | 185 | public: |
duke@435 | 186 | #ifdef ASSERT |
never@533 | 187 | No_Safepoint_Verifier(bool activated = true, bool verifygc = true ) : |
never@533 | 188 | No_GC_Verifier(verifygc), |
never@533 | 189 | _activated(activated) { |
duke@435 | 190 | _thread = Thread::current(); |
duke@435 | 191 | if (_activated) { |
duke@435 | 192 | _thread->_allow_allocation_count++; |
duke@435 | 193 | _thread->_allow_safepoint_count++; |
duke@435 | 194 | } |
duke@435 | 195 | } |
duke@435 | 196 | |
duke@435 | 197 | ~No_Safepoint_Verifier() { |
duke@435 | 198 | if (_activated) { |
duke@435 | 199 | _thread->_allow_allocation_count--; |
duke@435 | 200 | _thread->_allow_safepoint_count--; |
duke@435 | 201 | } |
duke@435 | 202 | } |
duke@435 | 203 | #else |
duke@435 | 204 | No_Safepoint_Verifier(bool activated = true, bool verifygc = true) : No_GC_Verifier(verifygc){} |
duke@435 | 205 | ~No_Safepoint_Verifier() {} |
duke@435 | 206 | #endif |
duke@435 | 207 | }; |
duke@435 | 208 | |
duke@435 | 209 | // A Pause_No_Safepoint_Verifier is used to temporarily pause the |
duke@435 | 210 | // behavior of a No_Safepoint_Verifier object. If we are not in debug |
duke@435 | 211 | // mode then there is nothing to do. If the No_Safepoint_Verifier |
duke@435 | 212 | // object has an _activated value of false, then there is nothing to |
duke@435 | 213 | // do for safepoint and allocation checking, but there may still be |
duke@435 | 214 | // something to do for the underlying No_GC_Verifier object. |
duke@435 | 215 | |
duke@435 | 216 | class Pause_No_Safepoint_Verifier : public Pause_No_GC_Verifier { |
duke@435 | 217 | private: |
duke@435 | 218 | No_Safepoint_Verifier * _nsv; |
duke@435 | 219 | |
duke@435 | 220 | public: |
duke@435 | 221 | #ifdef ASSERT |
duke@435 | 222 | Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) |
duke@435 | 223 | : Pause_No_GC_Verifier(nsv) { |
duke@435 | 224 | |
duke@435 | 225 | _nsv = nsv; |
duke@435 | 226 | if (_nsv->_activated) { |
duke@435 | 227 | _nsv->_thread->_allow_allocation_count--; |
duke@435 | 228 | _nsv->_thread->_allow_safepoint_count--; |
duke@435 | 229 | } |
duke@435 | 230 | } |
duke@435 | 231 | |
duke@435 | 232 | ~Pause_No_Safepoint_Verifier() { |
duke@435 | 233 | if (_nsv->_activated) { |
duke@435 | 234 | _nsv->_thread->_allow_allocation_count++; |
duke@435 | 235 | _nsv->_thread->_allow_safepoint_count++; |
duke@435 | 236 | } |
duke@435 | 237 | } |
duke@435 | 238 | #else |
duke@435 | 239 | Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv) |
duke@435 | 240 | : Pause_No_GC_Verifier(nsv) {} |
duke@435 | 241 | ~Pause_No_Safepoint_Verifier() {} |
duke@435 | 242 | #endif |
duke@435 | 243 | }; |
duke@435 | 244 | |
duke@435 | 245 | // JRT_LEAF currently can be called from either _thread_in_Java or |
duke@435 | 246 | // _thread_in_native mode. In _thread_in_native, it is ok |
duke@435 | 247 | // for another thread to trigger GC. The rest of the JRT_LEAF |
duke@435 | 248 | // rules apply. |
duke@435 | 249 | class JRT_Leaf_Verifier : public No_Safepoint_Verifier { |
duke@435 | 250 | static bool should_verify_GC(); |
duke@435 | 251 | public: |
duke@435 | 252 | #ifdef ASSERT |
duke@435 | 253 | JRT_Leaf_Verifier(); |
duke@435 | 254 | ~JRT_Leaf_Verifier(); |
duke@435 | 255 | #else |
duke@435 | 256 | JRT_Leaf_Verifier() {} |
duke@435 | 257 | ~JRT_Leaf_Verifier() {} |
duke@435 | 258 | #endif |
duke@435 | 259 | }; |
duke@435 | 260 | |
duke@435 | 261 | // A No_Alloc_Verifier object can be placed in methods where one assumes that |
duke@435 | 262 | // no allocation will occur. The destructor will verify this property |
duke@435 | 263 | // unless the constructor is called with argument false (not activated). |
duke@435 | 264 | // |
duke@435 | 265 | // The check will only be done in debug mode and if activated. |
duke@435 | 266 | // Note: this only makes sense at safepoints (otherwise, other threads may |
duke@435 | 267 | // allocate concurrently.) |
duke@435 | 268 | |
duke@435 | 269 | class No_Alloc_Verifier : public StackObj { |
duke@435 | 270 | private: |
duke@435 | 271 | bool _activated; |
duke@435 | 272 | |
duke@435 | 273 | public: |
duke@435 | 274 | #ifdef ASSERT |
duke@435 | 275 | No_Alloc_Verifier(bool activated = true) { |
duke@435 | 276 | _activated = activated; |
duke@435 | 277 | if (_activated) Thread::current()->_allow_allocation_count++; |
duke@435 | 278 | } |
duke@435 | 279 | |
duke@435 | 280 | ~No_Alloc_Verifier() { |
duke@435 | 281 | if (_activated) Thread::current()->_allow_allocation_count--; |
duke@435 | 282 | } |
duke@435 | 283 | #else |
duke@435 | 284 | No_Alloc_Verifier(bool activated = true) {} |
duke@435 | 285 | ~No_Alloc_Verifier() {} |
duke@435 | 286 | #endif |
duke@435 | 287 | }; |