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src/hotspot/share/runtime/mutexLocker.hpp

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  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  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #ifndef SHARE_RUNTIME_MUTEXLOCKER_HPP
 26 #define SHARE_RUNTIME_MUTEXLOCKER_HPP
 27 

 28 #include "memory/allocation.hpp"
 29 #include "runtime/flags/flagSetting.hpp"
 30 #include "runtime/mutex.hpp"


 31 
 32 class Thread;
 33 
 34 // Mutexes used in the VM.
 35 
 36 extern Mutex*   NMethodState_lock;               // a lock used to guard a compiled method state
 37 extern Monitor* SystemDictionary_lock;           // a lock on the system dictionary
 38 extern Mutex*   InvokeMethodTypeTable_lock;
 39 extern Monitor* InvokeMethodIntrinsicTable_lock;
 40 extern Mutex*   SharedDictionary_lock;           // a lock on the CDS shared dictionary
 41 extern Monitor* ClassInitError_lock;             // a lock on the class initialization error table
 42 extern Mutex*   Module_lock;                     // a lock on module and package related data structures
 43 extern Mutex*   CompiledIC_lock;                 // a lock used to guard compiled IC patching and access
 44 extern Mutex*   VMStatistic_lock;                // a lock used to guard statistics count increment
 45 extern Mutex*   JmethodIdCreation_lock;          // a lock on creating JNI method identifiers
 46 extern Mutex*   JfieldIdCreation_lock;           // a lock on creating JNI static field identifiers
 47 extern Monitor* JNICritical_lock;                // a lock used while synchronizing with threads entering/leaving JNI critical regions
 48 extern Mutex*   JvmtiThreadState_lock;           // a lock on modification of JVMTI thread data
 49 extern Monitor* EscapeBarrier_lock;              // a lock to sync reallocating and relocking objects because of JVMTI access
 50 extern Monitor* JvmtiVTMSTransition_lock;        // a lock for Virtual Thread Mount State transition (VTMS transition) management

 63 extern Mutex*   RetData_lock;                    // a lock on installation of RetData inside method data
 64 extern Monitor* VMOperation_lock;                // a lock on queue of vm_operations waiting to execute
 65 extern Monitor* ThreadsLockThrottle_lock;        // used by Thread start/exit to reduce competition for Threads_lock,
 66                                                  // so a VM thread calling a safepoint is prioritized
 67 extern Monitor* Threads_lock;                    // a lock on the Threads table of active Java threads
 68                                                  // (also used by Safepoints too to block threads creation/destruction)
 69 extern Mutex*   NonJavaThreadsList_lock;         // a lock on the NonJavaThreads list
 70 extern Mutex*   NonJavaThreadsListSync_lock;     // a lock for NonJavaThreads list synchronization
 71 extern Monitor* CGC_lock;                        // used for coordination between
 72                                                  // fore- & background GC threads.
 73 extern Monitor* STS_lock;                        // used for joining/leaving SuspendibleThreadSet.
 74 extern Monitor* G1OldGCCount_lock;               // in support of "concurrent" full gc
 75 extern Mutex*   G1RareEvent_lock;                // Synchronizes (rare) parallel GC operations.
 76 extern Mutex*   G1DetachedRefinementStats_lock;  // Lock protecting detached refinement stats
 77 extern Mutex*   MarkStackFreeList_lock;          // Protects access to the global mark stack free list.
 78 extern Mutex*   MarkStackChunkList_lock;         // Protects access to the global mark stack chunk list.
 79 extern Mutex*   MonitoringSupport_lock;          // Protects updates to the serviceability memory pools and allocated memory high water mark.
 80 extern Monitor* ConcurrentGCBreakpoints_lock;    // Protects concurrent GC breakpoint management
 81 extern Mutex*   Compile_lock;                    // a lock held when Compilation is updating code (used to block CodeCache traversal, CHA updates, etc)
 82 extern Monitor* MethodCompileQueue_lock;         // a lock held when method compilations are enqueued, dequeued





 83 extern Monitor* CompileThread_lock;              // a lock held by compile threads during compilation system initialization
 84 extern Monitor* Compilation_lock;                // a lock used to pause compilation
 85 extern Mutex*   CompileTaskAlloc_lock;           // a lock held when CompileTasks are allocated


 86 extern Mutex*   CompileStatistics_lock;          // a lock held when updating compilation statistics
 87 extern Mutex*   DirectivesStack_lock;            // a lock held when mutating the dirstack and ref counting directives
 88 extern Monitor* Terminator_lock;                 // a lock used to guard termination of the vm
 89 extern Monitor* InitCompleted_lock;              // a lock used to signal threads waiting on init completed
 90 extern Monitor* BeforeExit_lock;                 // a lock used to guard cleanups and shutdown hooks
 91 extern Monitor* Notify_lock;                     // a lock used to synchronize the start-up of the vm
 92 extern Mutex*   ExceptionCache_lock;             // a lock used to synchronize exception cache updates
 93 
 94 #ifndef PRODUCT
 95 extern Mutex*   FullGCALot_lock;                 // a lock to make FullGCALot MT safe
 96 #endif // PRODUCT
 97 
 98 extern Mutex*   RawMonitor_lock;
 99 extern Mutex*   PerfDataMemAlloc_lock;           // a lock on the allocator for PerfData memory for performance data
100 extern Mutex*   PerfDataManager_lock;            // a long on access to PerfDataManager resources
101 
102 extern Mutex*   FreeList_lock;                   // protects the free region list during safepoints
103 extern Mutex*   OldSets_lock;                    // protects the old region sets
104 extern Mutex*   Uncommit_lock;                   // protects the uncommit list when not at safepoints
105 extern Monitor* RootRegionScan_lock;             // used to notify that the CM threads have finished scanning the IM snapshot regions

112 extern Monitor* RedefineClasses_lock;            // locks classes from parallel redefinition
113 extern Mutex*   Verify_lock;                     // synchronize initialization of verify library
114 extern Monitor* ThreadsSMRDelete_lock;           // Used by ThreadsSMRSupport to take pressure off the Threads_lock
115 extern Mutex*   ThreadIdTableCreate_lock;        // Used by ThreadIdTable to lazily create the thread id table
116 extern Mutex*   SharedDecoder_lock;              // serializes access to the decoder during normal (not error reporting) use
117 extern Mutex*   DCmdFactory_lock;                // serialize access to DCmdFactory information
118 extern Mutex*   NMTQuery_lock;                   // serialize NMT Dcmd queries
119 extern Mutex*   NMTCompilationCostHistory_lock;  // guards NMT compilation cost history
120 extern Mutex*   NmtVirtualMemory_lock;           // guards NMT virtual memory updates
121 #if INCLUDE_CDS
122 #if INCLUDE_JVMTI
123 extern Mutex*   CDSClassFileStream_lock;         // FileMapInfo::open_stream_for_jvmti
124 #endif
125 extern Mutex*   DumpTimeTable_lock;              // SystemDictionaryShared::_dumptime_table
126 extern Mutex*   CDSLambda_lock;                  // LambdaProxyClassDictionary::find_lambda_proxy_class
127 extern Mutex*   DumpRegion_lock;                 // Symbol::operator new(size_t sz, int len)
128 extern Mutex*   ClassListFile_lock;              // ClassListWriter()
129 extern Mutex*   UnregisteredClassesTable_lock;   // UnregisteredClassesTableTable
130 extern Mutex*   LambdaFormInvokers_lock;         // Protecting LambdaFormInvokers::_lambdaform_lines
131 extern Mutex*   ScratchObjects_lock;             // Protecting _scratch_xxx_table in heapShared.cpp


132 #endif // INCLUDE_CDS
133 #if INCLUDE_JFR
134 extern Mutex*   JfrStacktrace_lock;              // used to guard access to the JFR stacktrace table
135 extern Monitor* JfrMsg_lock;                     // protects JFR messaging
136 extern Mutex*   JfrBuffer_lock;                  // protects JFR buffer operations
137 extern Monitor* JfrThreadSampler_lock;           // used to suspend/resume JFR thread sampler
138 #endif
139 
140 extern Mutex*   Metaspace_lock;                  // protects Metaspace virtualspace and chunk expansions
141 extern Monitor* MetaspaceCritical_lock;          // synchronizes failed metaspace allocations that risk throwing metaspace OOM
142 extern Mutex*   ClassLoaderDataGraph_lock;       // protects CLDG list, needed for concurrent unloading
143 
144 
145 extern Mutex*   CodeHeapStateAnalytics_lock;     // lock print functions against concurrent analyze functions.
146                                                  // Only used locally in PrintCodeCacheLayout processing.
147 
148 extern Mutex*   ExternalsRecorder_lock;          // used to guard access to the external addresses table
149 
150 extern Monitor* ContinuationRelativize_lock;
151 

169 // See orderAccess.hpp.  We assume throughout the VM that MutexLocker's
170 // and friends constructors do a fence, a lock and an acquire *in that
171 // order*.  And that their destructors do a release and unlock, in *that*
172 // order.  If their implementations change such that these assumptions
173 // are violated, a whole lot of code will break.
174 
175 // for debugging: check that we're already owning this lock (or are at a safepoint / handshake)
176 #ifdef ASSERT
177 void assert_locked_or_safepoint(const Mutex* lock);
178 void assert_lock_strong(const Mutex* lock);
179 #else
180 #define assert_locked_or_safepoint(lock)
181 #define assert_lock_strong(lock)
182 #endif
183 
184 // Internal implementation. Skips on null Mutex.
185 // Subclasses enforce stronger invariants.
186 class MutexLockerImpl: public StackObj {
187  protected:
188   Mutex* _mutex;










189 
190   MutexLockerImpl(Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
191     _mutex(mutex) {

192     bool no_safepoint_check = flag == Mutex::_no_safepoint_check_flag;
193     if (_mutex != nullptr) {


194       if (no_safepoint_check) {
195         _mutex->lock_without_safepoint_check();
196       } else {
197         _mutex->lock();
198       }


199     }
200   }
201 
202   MutexLockerImpl(Thread* thread, Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
203     _mutex(mutex) {



204     bool no_safepoint_check = flag == Mutex::_no_safepoint_check_flag;
205     if (_mutex != nullptr) {
206       if (no_safepoint_check) {
207         _mutex->lock_without_safepoint_check(thread);
208       } else {
209         _mutex->lock(thread);
210       }
211     }


212   }
213 
214   ~MutexLockerImpl() {
215     if (_mutex != nullptr) {
216       assert_lock_strong(_mutex);
217       _mutex->unlock();












218     }
219   }
220 



221  public:


222   static void post_initialize();


223 };
224 
225 // Simplest mutex locker.
226 // Does not allow null mutexes.
227 class MutexLocker: public MutexLockerImpl {
228  public:
229    MutexLocker(Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
230      MutexLockerImpl(mutex, flag) {
231      assert(mutex != nullptr, "null mutex not allowed");
232    }
233 
234    MutexLocker(Thread* thread, Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
235      MutexLockerImpl(thread, mutex, flag) {
236      assert(mutex != nullptr, "null mutex not allowed");
237    }
238 };
239 
240 // Conditional mutex locker.
241 // Like MutexLocker above, but only locks when condition is true.
242 class ConditionalMutexLocker: public MutexLockerImpl {

  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  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #ifndef SHARE_RUNTIME_MUTEXLOCKER_HPP
 26 #define SHARE_RUNTIME_MUTEXLOCKER_HPP
 27 
 28 #include "logging/log.hpp"
 29 #include "memory/allocation.hpp"
 30 #include "runtime/flags/flagSetting.hpp"
 31 #include "runtime/mutex.hpp"
 32 #include "runtime/perfData.hpp"
 33 #include "runtime/thread.hpp"
 34 
 35 class Thread;
 36 
 37 // Mutexes used in the VM.
 38 
 39 extern Mutex*   NMethodState_lock;               // a lock used to guard a compiled method state
 40 extern Monitor* SystemDictionary_lock;           // a lock on the system dictionary
 41 extern Mutex*   InvokeMethodTypeTable_lock;
 42 extern Monitor* InvokeMethodIntrinsicTable_lock;
 43 extern Mutex*   SharedDictionary_lock;           // a lock on the CDS shared dictionary
 44 extern Monitor* ClassInitError_lock;             // a lock on the class initialization error table
 45 extern Mutex*   Module_lock;                     // a lock on module and package related data structures
 46 extern Mutex*   CompiledIC_lock;                 // a lock used to guard compiled IC patching and access
 47 extern Mutex*   VMStatistic_lock;                // a lock used to guard statistics count increment
 48 extern Mutex*   JmethodIdCreation_lock;          // a lock on creating JNI method identifiers
 49 extern Mutex*   JfieldIdCreation_lock;           // a lock on creating JNI static field identifiers
 50 extern Monitor* JNICritical_lock;                // a lock used while synchronizing with threads entering/leaving JNI critical regions
 51 extern Mutex*   JvmtiThreadState_lock;           // a lock on modification of JVMTI thread data
 52 extern Monitor* EscapeBarrier_lock;              // a lock to sync reallocating and relocking objects because of JVMTI access
 53 extern Monitor* JvmtiVTMSTransition_lock;        // a lock for Virtual Thread Mount State transition (VTMS transition) management

 66 extern Mutex*   RetData_lock;                    // a lock on installation of RetData inside method data
 67 extern Monitor* VMOperation_lock;                // a lock on queue of vm_operations waiting to execute
 68 extern Monitor* ThreadsLockThrottle_lock;        // used by Thread start/exit to reduce competition for Threads_lock,
 69                                                  // so a VM thread calling a safepoint is prioritized
 70 extern Monitor* Threads_lock;                    // a lock on the Threads table of active Java threads
 71                                                  // (also used by Safepoints too to block threads creation/destruction)
 72 extern Mutex*   NonJavaThreadsList_lock;         // a lock on the NonJavaThreads list
 73 extern Mutex*   NonJavaThreadsListSync_lock;     // a lock for NonJavaThreads list synchronization
 74 extern Monitor* CGC_lock;                        // used for coordination between
 75                                                  // fore- & background GC threads.
 76 extern Monitor* STS_lock;                        // used for joining/leaving SuspendibleThreadSet.
 77 extern Monitor* G1OldGCCount_lock;               // in support of "concurrent" full gc
 78 extern Mutex*   G1RareEvent_lock;                // Synchronizes (rare) parallel GC operations.
 79 extern Mutex*   G1DetachedRefinementStats_lock;  // Lock protecting detached refinement stats
 80 extern Mutex*   MarkStackFreeList_lock;          // Protects access to the global mark stack free list.
 81 extern Mutex*   MarkStackChunkList_lock;         // Protects access to the global mark stack chunk list.
 82 extern Mutex*   MonitoringSupport_lock;          // Protects updates to the serviceability memory pools and allocated memory high water mark.
 83 extern Monitor* ConcurrentGCBreakpoints_lock;    // Protects concurrent GC breakpoint management
 84 extern Mutex*   Compile_lock;                    // a lock held when Compilation is updating code (used to block CodeCache traversal, CHA updates, etc)
 85 extern Monitor* MethodCompileQueue_lock;         // a lock held when method compilations are enqueued, dequeued
 86 extern Monitor* MethodCompileQueueC1_lock;       // a lock held when method compilations are enqueued, dequeued
 87 extern Monitor* MethodCompileQueueC2_lock;       // a lock held when method compilations are enqueued, dequeued
 88 extern Monitor* MethodCompileQueueC3_lock;       // a lock held when method compilations are enqueued, dequeued
 89 extern Monitor* MethodCompileQueueSC1_lock;      // a lock held when method compilations are enqueued, dequeued
 90 extern Monitor* MethodCompileQueueSC2_lock;      // a lock held when method compilations are enqueued, dequeued
 91 extern Monitor* CompileThread_lock;              // a lock held by compile threads during compilation system initialization
 92 extern Monitor* Compilation_lock;                // a lock used to pause compilation
 93 extern Mutex*   TrainingData_lock;               // a lock used when accessing training records
 94 extern Monitor* TrainingReplayQueue_lock;        // a lock held when class are added/removed to the training replay queue
 95 extern Monitor* CompileTaskAlloc_lock;           // a lock held when CompileTasks are allocated
 96 extern Mutex*   CompileStatistics_lock;          // a lock held when updating compilation statistics
 97 extern Mutex*   DirectivesStack_lock;            // a lock held when mutating the dirstack and ref counting directives
 98 extern Monitor* Terminator_lock;                 // a lock used to guard termination of the vm
 99 extern Monitor* InitCompleted_lock;              // a lock used to signal threads waiting on init completed
100 extern Monitor* BeforeExit_lock;                 // a lock used to guard cleanups and shutdown hooks
101 extern Monitor* Notify_lock;                     // a lock used to synchronize the start-up of the vm
102 extern Mutex*   ExceptionCache_lock;             // a lock used to synchronize exception cache updates
103 
104 #ifndef PRODUCT
105 extern Mutex*   FullGCALot_lock;                 // a lock to make FullGCALot MT safe
106 #endif // PRODUCT
107 
108 extern Mutex*   RawMonitor_lock;
109 extern Mutex*   PerfDataMemAlloc_lock;           // a lock on the allocator for PerfData memory for performance data
110 extern Mutex*   PerfDataManager_lock;            // a long on access to PerfDataManager resources
111 
112 extern Mutex*   FreeList_lock;                   // protects the free region list during safepoints
113 extern Mutex*   OldSets_lock;                    // protects the old region sets
114 extern Mutex*   Uncommit_lock;                   // protects the uncommit list when not at safepoints
115 extern Monitor* RootRegionScan_lock;             // used to notify that the CM threads have finished scanning the IM snapshot regions

122 extern Monitor* RedefineClasses_lock;            // locks classes from parallel redefinition
123 extern Mutex*   Verify_lock;                     // synchronize initialization of verify library
124 extern Monitor* ThreadsSMRDelete_lock;           // Used by ThreadsSMRSupport to take pressure off the Threads_lock
125 extern Mutex*   ThreadIdTableCreate_lock;        // Used by ThreadIdTable to lazily create the thread id table
126 extern Mutex*   SharedDecoder_lock;              // serializes access to the decoder during normal (not error reporting) use
127 extern Mutex*   DCmdFactory_lock;                // serialize access to DCmdFactory information
128 extern Mutex*   NMTQuery_lock;                   // serialize NMT Dcmd queries
129 extern Mutex*   NMTCompilationCostHistory_lock;  // guards NMT compilation cost history
130 extern Mutex*   NmtVirtualMemory_lock;           // guards NMT virtual memory updates
131 #if INCLUDE_CDS
132 #if INCLUDE_JVMTI
133 extern Mutex*   CDSClassFileStream_lock;         // FileMapInfo::open_stream_for_jvmti
134 #endif
135 extern Mutex*   DumpTimeTable_lock;              // SystemDictionaryShared::_dumptime_table
136 extern Mutex*   CDSLambda_lock;                  // LambdaProxyClassDictionary::find_lambda_proxy_class
137 extern Mutex*   DumpRegion_lock;                 // Symbol::operator new(size_t sz, int len)
138 extern Mutex*   ClassListFile_lock;              // ClassListWriter()
139 extern Mutex*   UnregisteredClassesTable_lock;   // UnregisteredClassesTableTable
140 extern Mutex*   LambdaFormInvokers_lock;         // Protecting LambdaFormInvokers::_lambdaform_lines
141 extern Mutex*   ScratchObjects_lock;             // Protecting _scratch_xxx_table in heapShared.cpp
142 extern Mutex*   ArchivedObjectTables_lock;       // Protecting the table used by HeapShared::get_archived_object_permanent_index()
143 extern Mutex*   FinalImageRecipes_lock;          // Protecting the tables used by FinalImageRecipes.
144 #endif // INCLUDE_CDS
145 #if INCLUDE_JFR
146 extern Mutex*   JfrStacktrace_lock;              // used to guard access to the JFR stacktrace table
147 extern Monitor* JfrMsg_lock;                     // protects JFR messaging
148 extern Mutex*   JfrBuffer_lock;                  // protects JFR buffer operations
149 extern Monitor* JfrThreadSampler_lock;           // used to suspend/resume JFR thread sampler
150 #endif
151 
152 extern Mutex*   Metaspace_lock;                  // protects Metaspace virtualspace and chunk expansions
153 extern Monitor* MetaspaceCritical_lock;          // synchronizes failed metaspace allocations that risk throwing metaspace OOM
154 extern Mutex*   ClassLoaderDataGraph_lock;       // protects CLDG list, needed for concurrent unloading
155 
156 
157 extern Mutex*   CodeHeapStateAnalytics_lock;     // lock print functions against concurrent analyze functions.
158                                                  // Only used locally in PrintCodeCacheLayout processing.
159 
160 extern Mutex*   ExternalsRecorder_lock;          // used to guard access to the external addresses table
161 
162 extern Monitor* ContinuationRelativize_lock;
163 

181 // See orderAccess.hpp.  We assume throughout the VM that MutexLocker's
182 // and friends constructors do a fence, a lock and an acquire *in that
183 // order*.  And that their destructors do a release and unlock, in *that*
184 // order.  If their implementations change such that these assumptions
185 // are violated, a whole lot of code will break.
186 
187 // for debugging: check that we're already owning this lock (or are at a safepoint / handshake)
188 #ifdef ASSERT
189 void assert_locked_or_safepoint(const Mutex* lock);
190 void assert_lock_strong(const Mutex* lock);
191 #else
192 #define assert_locked_or_safepoint(lock)
193 #define assert_lock_strong(lock)
194 #endif
195 
196 // Internal implementation. Skips on null Mutex.
197 // Subclasses enforce stronger invariants.
198 class MutexLockerImpl: public StackObj {
199  protected:
200   Mutex* _mutex;
201   bool _prof;
202   elapsedTimer _before;
203   elapsedTimer _after;
204 
205 private:
206   static PerfCounter** _perf_lock_count;
207   static PerfCounter** _perf_lock_wait_time;
208   static PerfCounter** _perf_lock_hold_time;
209 
210 public:
211 
212   MutexLockerImpl(Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
213     _mutex(mutex), _prof(ProfileVMLocks && Thread::current_or_null() != nullptr && Thread::current()->profile_vm_locks()) {
214 
215     bool no_safepoint_check = flag == Mutex::_no_safepoint_check_flag;
216     if (_mutex != nullptr) {
217       if (_prof) { _before.start(); } // before
218 
219       if (no_safepoint_check) {
220         _mutex->lock_without_safepoint_check();
221       } else {
222         _mutex->lock();
223       }
224 
225       if (_prof) { _before.stop(); _after.start(); } // after
226     }
227   }
228 
229   MutexLockerImpl(Thread* thread, Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
230     _mutex(mutex), _prof(thread->profile_vm_locks()) {
231 
232     if (_prof) { _before.start(); } // before
233 
234     bool no_safepoint_check = flag == Mutex::_no_safepoint_check_flag;
235     if (_mutex != nullptr) {
236       if (no_safepoint_check) {
237         _mutex->lock_without_safepoint_check(thread);
238       } else {
239         _mutex->lock(thread);
240       }
241     }
242 
243     if (_prof) { _before.stop(); _after.start(); } // after
244   }
245 
246   ~MutexLockerImpl() {
247     if (_mutex != nullptr) {
248       assert_lock_strong(_mutex);
249       _mutex->unlock();
250 
251       if (_mutex->id() == -1) {
252         log_trace(init)("Unnamed unclassified lock: %s", _mutex->name());
253       }
254 
255       if (_prof) {
256         assert(UsePerfData, "required");
257         _after.stop();
258         _perf_lock_count    [_mutex->id() + 1]->inc();
259         _perf_lock_wait_time[_mutex->id() + 1]->inc(_before.ticks());
260         _perf_lock_hold_time[_mutex->id() + 1]->inc(_after.ticks());
261       }
262     }
263   }
264 
265  private:
266   static void print_counter_on(outputStream* st, const char* name, bool is_unique, int idx);
267 
268  public:
269   static int name2id(const char* name);
270 
271   static void post_initialize();
272   static void init_counters();
273   static void print_counters_on(outputStream* st);
274 };
275 
276 // Simplest mutex locker.
277 // Does not allow null mutexes.
278 class MutexLocker: public MutexLockerImpl {
279  public:
280    MutexLocker(Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
281      MutexLockerImpl(mutex, flag) {
282      assert(mutex != nullptr, "null mutex not allowed");
283    }
284 
285    MutexLocker(Thread* thread, Mutex* mutex, Mutex::SafepointCheckFlag flag = Mutex::_safepoint_check_flag) :
286      MutexLockerImpl(thread, mutex, flag) {
287      assert(mutex != nullptr, "null mutex not allowed");
288    }
289 };
290 
291 // Conditional mutex locker.
292 // Like MutexLocker above, but only locks when condition is true.
293 class ConditionalMutexLocker: public MutexLockerImpl {
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