Mon, 21 Nov 2011 09:24:56 -0800
7110173: GCNotifier::pushNotification publishes stale data.
Summary: GCNotifier::pushNotification() references GCMemoryManager::_last_gc_stat but is called from GCMemoryManager::gc_end() before GCMemoryManager::_last_gc_stat is set up using the values in GCMemoryManager::_current_gc_stat. As a result the GC notification code accesses unitialized or stale data. Move the notification call after GCMemoryManager::_las_gc_stat is set, but inside the same if-block.
Reviewed-by: poonam, dholmes, fparain, mchung
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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23 */
25 #include "precompiled.hpp"
26 #include "classfile/systemDictionary.hpp"
27 #include "classfile/vmSymbols.hpp"
28 #include "oops/oop.inline.hpp"
29 #include "runtime/handles.inline.hpp"
30 #include "runtime/javaCalls.hpp"
31 #include "services/lowMemoryDetector.hpp"
32 #include "services/management.hpp"
33 #include "services/memoryManager.hpp"
34 #include "services/memoryPool.hpp"
35 #include "services/memoryService.hpp"
36 #include "services/gcNotifier.hpp"
37 #include "utilities/dtrace.hpp"
39 #ifndef USDT2
40 HS_DTRACE_PROBE_DECL8(hotspot, mem__pool__gc__begin, char*, int, char*, int,
41 size_t, size_t, size_t, size_t);
42 HS_DTRACE_PROBE_DECL8(hotspot, mem__pool__gc__end, char*, int, char*, int,
43 size_t, size_t, size_t, size_t);
44 #endif /* !USDT2 */
46 MemoryManager::MemoryManager() {
47 _num_pools = 0;
48 _memory_mgr_obj = NULL;
49 }
51 void MemoryManager::add_pool(MemoryPool* pool) {
52 assert(_num_pools < MemoryManager::max_num_pools, "_num_pools exceeds the max");
53 if (_num_pools < MemoryManager::max_num_pools) {
54 _pools[_num_pools] = pool;
55 _num_pools++;
56 }
57 pool->add_manager(this);
58 }
60 MemoryManager* MemoryManager::get_code_cache_memory_manager() {
61 return (MemoryManager*) new CodeCacheMemoryManager();
62 }
64 GCMemoryManager* MemoryManager::get_copy_memory_manager() {
65 return (GCMemoryManager*) new CopyMemoryManager();
66 }
68 GCMemoryManager* MemoryManager::get_msc_memory_manager() {
69 return (GCMemoryManager*) new MSCMemoryManager();
70 }
72 GCMemoryManager* MemoryManager::get_parnew_memory_manager() {
73 return (GCMemoryManager*) new ParNewMemoryManager();
74 }
76 GCMemoryManager* MemoryManager::get_cms_memory_manager() {
77 return (GCMemoryManager*) new CMSMemoryManager();
78 }
80 GCMemoryManager* MemoryManager::get_psScavenge_memory_manager() {
81 return (GCMemoryManager*) new PSScavengeMemoryManager();
82 }
84 GCMemoryManager* MemoryManager::get_psMarkSweep_memory_manager() {
85 return (GCMemoryManager*) new PSMarkSweepMemoryManager();
86 }
88 GCMemoryManager* MemoryManager::get_g1YoungGen_memory_manager() {
89 return (GCMemoryManager*) new G1YoungGenMemoryManager();
90 }
92 GCMemoryManager* MemoryManager::get_g1OldGen_memory_manager() {
93 return (GCMemoryManager*) new G1OldGenMemoryManager();
94 }
96 instanceOop MemoryManager::get_memory_manager_instance(TRAPS) {
97 // Must do an acquire so as to force ordering of subsequent
98 // loads from anything _memory_mgr_obj points to or implies.
99 instanceOop mgr_obj = (instanceOop)OrderAccess::load_ptr_acquire(&_memory_mgr_obj);
100 if (mgr_obj == NULL) {
101 // It's ok for more than one thread to execute the code up to the locked region.
102 // Extra manager instances will just be gc'ed.
103 klassOop k = Management::sun_management_ManagementFactory_klass(CHECK_0);
104 instanceKlassHandle ik(THREAD, k);
106 Handle mgr_name = java_lang_String::create_from_str(name(), CHECK_0);
108 JavaValue result(T_OBJECT);
109 JavaCallArguments args;
110 args.push_oop(mgr_name); // Argument 1
112 Symbol* method_name = NULL;
113 Symbol* signature = NULL;
114 if (is_gc_memory_manager()) {
115 method_name = vmSymbols::createGarbageCollector_name();
116 signature = vmSymbols::createGarbageCollector_signature();
117 args.push_oop(Handle()); // Argument 2 (for future extension)
118 } else {
119 method_name = vmSymbols::createMemoryManager_name();
120 signature = vmSymbols::createMemoryManager_signature();
121 }
123 JavaCalls::call_static(&result,
124 ik,
125 method_name,
126 signature,
127 &args,
128 CHECK_0);
130 instanceOop m = (instanceOop) result.get_jobject();
131 instanceHandle mgr(THREAD, m);
133 {
134 // Get lock before setting _memory_mgr_obj
135 // since another thread may have created the instance
136 MutexLocker ml(Management_lock);
138 // Check if another thread has created the management object. We reload
139 // _memory_mgr_obj here because some other thread may have initialized
140 // it while we were executing the code before the lock.
141 //
142 // The lock has done an acquire, so the load can't float above it, but
143 // we need to do a load_acquire as above.
144 mgr_obj = (instanceOop)OrderAccess::load_ptr_acquire(&_memory_mgr_obj);
145 if (mgr_obj != NULL) {
146 return mgr_obj;
147 }
149 // Get the address of the object we created via call_special.
150 mgr_obj = mgr();
152 // Use store barrier to make sure the memory accesses associated
153 // with creating the management object are visible before publishing
154 // its address. The unlock will publish the store to _memory_mgr_obj
155 // because it does a release first.
156 OrderAccess::release_store_ptr(&_memory_mgr_obj, mgr_obj);
157 }
158 }
160 return mgr_obj;
161 }
163 void MemoryManager::oops_do(OopClosure* f) {
164 f->do_oop((oop*) &_memory_mgr_obj);
165 }
167 GCStatInfo::GCStatInfo(int num_pools) {
168 // initialize the arrays for memory usage
169 _before_gc_usage_array = (MemoryUsage*) NEW_C_HEAP_ARRAY(MemoryUsage, num_pools);
170 _after_gc_usage_array = (MemoryUsage*) NEW_C_HEAP_ARRAY(MemoryUsage, num_pools);
171 _usage_array_size = num_pools;
172 clear();
173 }
175 GCStatInfo::~GCStatInfo() {
176 FREE_C_HEAP_ARRAY(MemoryUsage*, _before_gc_usage_array);
177 FREE_C_HEAP_ARRAY(MemoryUsage*, _after_gc_usage_array);
178 }
180 void GCStatInfo::set_gc_usage(int pool_index, MemoryUsage usage, bool before_gc) {
181 MemoryUsage* gc_usage_array;
182 if (before_gc) {
183 gc_usage_array = _before_gc_usage_array;
184 } else {
185 gc_usage_array = _after_gc_usage_array;
186 }
187 gc_usage_array[pool_index] = usage;
188 }
190 void GCStatInfo::clear() {
191 _index = 0;
192 _start_time = 0L;
193 _end_time = 0L;
194 size_t len = _usage_array_size * sizeof(MemoryUsage);
195 memset(_before_gc_usage_array, 0, len);
196 memset(_after_gc_usage_array, 0, len);
197 }
200 GCMemoryManager::GCMemoryManager() : MemoryManager() {
201 _num_collections = 0;
202 _last_gc_stat = NULL;
203 _last_gc_lock = new Mutex(Mutex::leaf, "_last_gc_lock", true);
204 _current_gc_stat = NULL;
205 _num_gc_threads = 1;
206 _notification_enabled = false;
207 }
209 GCMemoryManager::~GCMemoryManager() {
210 delete _last_gc_stat;
211 delete _last_gc_lock;
212 delete _current_gc_stat;
213 }
215 void GCMemoryManager::initialize_gc_stat_info() {
216 assert(MemoryService::num_memory_pools() > 0, "should have one or more memory pools");
217 _last_gc_stat = new GCStatInfo(MemoryService::num_memory_pools());
218 _current_gc_stat = new GCStatInfo(MemoryService::num_memory_pools());
219 // tracking concurrent collections we need two objects: one to update, and one to
220 // hold the publicly available "last (completed) gc" information.
221 }
223 void GCMemoryManager::gc_begin(bool recordGCBeginTime, bool recordPreGCUsage,
224 bool recordAccumulatedGCTime) {
225 assert(_last_gc_stat != NULL && _current_gc_stat != NULL, "Just checking");
226 if (recordAccumulatedGCTime) {
227 _accumulated_timer.start();
228 }
229 // _num_collections now increases in gc_end, to count completed collections
230 if (recordGCBeginTime) {
231 _current_gc_stat->set_index(_num_collections+1);
232 _current_gc_stat->set_start_time(Management::timestamp());
233 }
235 if (recordPreGCUsage) {
236 // Keep memory usage of all memory pools
237 for (int i = 0; i < MemoryService::num_memory_pools(); i++) {
238 MemoryPool* pool = MemoryService::get_memory_pool(i);
239 MemoryUsage usage = pool->get_memory_usage();
240 _current_gc_stat->set_before_gc_usage(i, usage);
241 #ifndef USDT2
242 HS_DTRACE_PROBE8(hotspot, mem__pool__gc__begin,
243 name(), strlen(name()),
244 pool->name(), strlen(pool->name()),
245 usage.init_size(), usage.used(),
246 usage.committed(), usage.max_size());
247 #else /* USDT2 */
248 HOTSPOT_MEM_POOL_GC_BEGIN(
249 (char *) name(), strlen(name()),
250 (char *) pool->name(), strlen(pool->name()),
251 usage.init_size(), usage.used(),
252 usage.committed(), usage.max_size());
253 #endif /* USDT2 */
254 }
255 }
256 }
258 // A collector MUST, even if it does not complete for some reason,
259 // make a TraceMemoryManagerStats object where countCollection is true,
260 // to ensure the current gc stat is placed in _last_gc_stat.
261 void GCMemoryManager::gc_end(bool recordPostGCUsage,
262 bool recordAccumulatedGCTime,
263 bool recordGCEndTime, bool countCollection,
264 GCCause::Cause cause) {
265 if (recordAccumulatedGCTime) {
266 _accumulated_timer.stop();
267 }
268 if (recordGCEndTime) {
269 _current_gc_stat->set_end_time(Management::timestamp());
270 }
272 if (recordPostGCUsage) {
273 int i;
274 // keep the last gc statistics for all memory pools
275 for (i = 0; i < MemoryService::num_memory_pools(); i++) {
276 MemoryPool* pool = MemoryService::get_memory_pool(i);
277 MemoryUsage usage = pool->get_memory_usage();
279 #ifndef USDT2
280 HS_DTRACE_PROBE8(hotspot, mem__pool__gc__end,
281 name(), strlen(name()),
282 pool->name(), strlen(pool->name()),
283 usage.init_size(), usage.used(),
284 usage.committed(), usage.max_size());
285 #else /* USDT2 */
286 HOTSPOT_MEM_POOL_GC_END(
287 (char *) name(), strlen(name()),
288 (char *) pool->name(), strlen(pool->name()),
289 usage.init_size(), usage.used(),
290 usage.committed(), usage.max_size());
291 #endif /* USDT2 */
293 _current_gc_stat->set_after_gc_usage(i, usage);
294 }
296 // Set last collection usage of the memory pools managed by this collector
297 for (i = 0; i < num_memory_pools(); i++) {
298 MemoryPool* pool = get_memory_pool(i);
299 MemoryUsage usage = pool->get_memory_usage();
301 // Compare with GC usage threshold
302 pool->set_last_collection_usage(usage);
303 LowMemoryDetector::detect_after_gc_memory(pool);
304 }
305 }
307 if (countCollection) {
308 _num_collections++;
309 // alternately update two objects making one public when complete
310 {
311 MutexLockerEx ml(_last_gc_lock, Mutex::_no_safepoint_check_flag);
312 GCStatInfo *tmp = _last_gc_stat;
313 _last_gc_stat = _current_gc_stat;
314 _current_gc_stat = tmp;
315 // reset the current stat for diagnosability purposes
316 _current_gc_stat->clear();
317 }
319 if (is_notification_enabled()) {
320 bool isMajorGC = this == MemoryService::get_major_gc_manager();
321 GCNotifier::pushNotification(this, isMajorGC ? "end of major GC" : "end of minor GC",
322 GCCause::to_string(cause));
323 }
324 }
325 }
327 size_t GCMemoryManager::get_last_gc_stat(GCStatInfo* dest) {
328 MutexLockerEx ml(_last_gc_lock, Mutex::_no_safepoint_check_flag);
329 if (_last_gc_stat->gc_index() != 0) {
330 dest->set_index(_last_gc_stat->gc_index());
331 dest->set_start_time(_last_gc_stat->start_time());
332 dest->set_end_time(_last_gc_stat->end_time());
333 assert(dest->usage_array_size() == _last_gc_stat->usage_array_size(),
334 "Must have same array size");
335 size_t len = dest->usage_array_size() * sizeof(MemoryUsage);
336 memcpy(dest->before_gc_usage_array(), _last_gc_stat->before_gc_usage_array(), len);
337 memcpy(dest->after_gc_usage_array(), _last_gc_stat->after_gc_usage_array(), len);
338 }
339 return _last_gc_stat->gc_index();
340 }