1 /*
   2  * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
   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  *
  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 #include "precompiled.hpp"
  26 #include "memory/universe.hpp"
  27 #include "runtime/mutexLocker.hpp"
  28 #include "runtime/os.inline.hpp"
  29 #include "runtime/safepoint.hpp"
  30 #include "runtime/thread.inline.hpp"
  31 #include "runtime/vmThread.hpp"
  32 
  33 // Mutexes used in the VM (see comment in mutexLocker.hpp):
  34 //
  35 // Note that the following pointers are effectively final -- after having been
  36 // set at JVM startup-time, they should never be subsequently mutated.
  37 // Instead of using pointers to malloc()ed monitors and mutexes we should consider
  38 // eliminating the indirection and using instances instead.
  39 // Consider using GCC's __read_mostly.
  40 
  41 Mutex*   Patching_lock                = NULL;
  42 Monitor* SystemDictionary_lock        = NULL;
  43 Mutex*   ProtectionDomainSet_lock     = NULL;
  44 Mutex*   SharedDictionary_lock        = NULL;
  45 Mutex*   Module_lock                  = NULL;
  46 Mutex*   CompiledIC_lock              = NULL;
  47 Mutex*   InlineCacheBuffer_lock       = NULL;
  48 Mutex*   VMStatistic_lock             = NULL;
  49 Mutex*   JNIGlobalAlloc_lock          = NULL;
  50 Mutex*   JNIGlobalActive_lock         = NULL;
  51 Mutex*   JNIWeakAlloc_lock            = NULL;
  52 Mutex*   JNIWeakActive_lock           = NULL;
  53 Mutex*   StringTableWeakAlloc_lock    = NULL;
  54 Mutex*   StringTableWeakActive_lock   = NULL;
  55 Mutex*   JNIHandleBlockFreeList_lock  = NULL;
  56 Mutex*   VMGlobalAlloc_lock           = NULL;
  57 Mutex*   VMGlobalActive_lock          = NULL;
  58 Mutex*   VMWeakAlloc_lock             = NULL;
  59 Mutex*   VMWeakActive_lock            = NULL;
  60 Mutex*   ResolvedMethodTableWeakAlloc_lock  = NULL;
  61 Mutex*   ResolvedMethodTableWeakActive_lock = NULL;
  62 Mutex*   NMethodKeepaliveAlloc_lock   = NULL;
  63 Mutex*   NMethodKeepaliveActive_lock  = NULL;
  64 Mutex*   JmethodIdCreation_lock       = NULL;
  65 Mutex*   JfieldIdCreation_lock        = NULL;
  66 Monitor* JNICritical_lock             = NULL;
  67 Mutex*   JvmtiThreadState_lock        = NULL;
  68 Monitor* Heap_lock                    = NULL;
  69 Mutex*   ExpandHeap_lock              = NULL;
  70 Mutex*   AdapterHandlerLibrary_lock   = NULL;
  71 Mutex*   SignatureHandlerLibrary_lock = NULL;
  72 Mutex*   VtableStubs_lock             = NULL;
  73 Mutex*   SymbolArena_lock             = NULL;
  74 Monitor* StringDedupQueue_lock        = NULL;
  75 Mutex*   StringDedupTable_lock        = NULL;
  76 Monitor* CodeCache_lock               = NULL;
  77 Mutex*   MethodData_lock              = NULL;
  78 Mutex*   TouchedMethodLog_lock        = NULL;
  79 Mutex*   RetData_lock                 = NULL;
  80 Monitor* VMOperationQueue_lock        = NULL;
  81 Monitor* VMOperationRequest_lock      = NULL;
  82 Monitor* SerializePage_lock           = NULL;
  83 Monitor* Threads_lock                 = NULL;
  84 Mutex*   NonJavaThreadsList_lock      = NULL;
  85 Mutex*   NonJavaThreadsListSync_lock  = NULL;
  86 Monitor* CGC_lock                     = NULL;
  87 Monitor* STS_lock                     = NULL;
  88 Monitor* FullGCCount_lock             = NULL;
  89 Monitor* DirtyCardQ_CBL_mon           = NULL;
  90 Mutex*   Shared_DirtyCardQ_lock       = NULL;
  91 Mutex*   MarkStackFreeList_lock       = NULL;
  92 Mutex*   MarkStackChunkList_lock      = NULL;
  93 Mutex*   MonitoringSupport_lock       = NULL;
  94 Mutex*   ParGCRareEvent_lock          = NULL;
  95 Monitor* CGCPhaseManager_lock         = NULL;
  96 Mutex*   Compile_lock                 = NULL;
  97 Monitor* MethodCompileQueue_lock      = NULL;
  98 Monitor* CompileThread_lock           = NULL;
  99 Monitor* Compilation_lock             = NULL;
 100 Mutex*   CompileTaskAlloc_lock        = NULL;
 101 Mutex*   CompileStatistics_lock       = NULL;
 102 Mutex*   DirectivesStack_lock         = NULL;
 103 Mutex*   MultiArray_lock              = NULL;
 104 Monitor* Terminator_lock              = NULL;
 105 Monitor* InitCompleted_lock           = NULL;
 106 Monitor* BeforeExit_lock              = NULL;
 107 Monitor* Notify_lock                  = NULL;
 108 Mutex*   ProfilePrint_lock            = NULL;
 109 Mutex*   ExceptionCache_lock          = NULL;
 110 Mutex*   OsrList_lock                 = NULL;
 111 Mutex*   NMethodSweeperStats_lock     = NULL;
 112 #ifndef PRODUCT
 113 Mutex*   FullGCALot_lock              = NULL;
 114 #endif
 115 
 116 Mutex*   Debug1_lock                  = NULL;
 117 Mutex*   Debug2_lock                  = NULL;
 118 Mutex*   Debug3_lock                  = NULL;
 119 
 120 Mutex*   tty_lock                     = NULL;
 121 
 122 Mutex*   RawMonitor_lock              = NULL;
 123 Mutex*   PerfDataMemAlloc_lock        = NULL;
 124 Mutex*   PerfDataManager_lock         = NULL;
 125 Mutex*   OopMapCacheAlloc_lock        = NULL;
 126 
 127 Mutex*   FreeList_lock                = NULL;
 128 Mutex*   OldSets_lock                 = NULL;
 129 Monitor* RootRegionScan_lock          = NULL;
 130 
 131 Monitor* GCTaskManager_lock           = NULL;
 132 
 133 Mutex*   Management_lock              = NULL;
 134 Monitor* Service_lock                 = NULL;
 135 Monitor* PeriodicTask_lock            = NULL;
 136 Monitor* RedefineClasses_lock         = NULL;
 137 
 138 #if INCLUDE_JFR
 139 Mutex*   JfrStacktrace_lock           = NULL;
 140 Monitor* JfrMsg_lock                  = NULL;
 141 Mutex*   JfrBuffer_lock               = NULL;
 142 Mutex*   JfrStream_lock               = NULL;
 143 Monitor* JfrThreadSampler_lock        = NULL;
 144 #endif
 145 
 146 #ifndef SUPPORTS_NATIVE_CX8
 147 Mutex*   UnsafeJlong_lock             = NULL;
 148 #endif
 149 Monitor* CodeHeapStateAnalytics_lock  = NULL;
 150 
 151 Mutex*   MetaspaceExpand_lock         = NULL;
 152 Mutex*   ClassLoaderDataGraph_lock    = NULL;
 153 Monitor* ThreadsSMRDelete_lock        = NULL;
 154 Mutex*   SharedDecoder_lock           = NULL;
 155 Mutex*   DCmdFactory_lock             = NULL;
 156 #if INCLUDE_NMT
 157 Mutex*   NMTQuery_lock                = NULL;
 158 #endif
 159 #if INCLUDE_CDS
 160 #if INCLUDE_JVMTI
 161 Mutex*   CDSClassFileStream_lock      = NULL;
 162 #endif
 163 Mutex*   DumpTimeTable_lock           = NULL;
 164 #endif // INCLUDE_CDS
 165 
 166 #if INCLUDE_JVMCI
 167 Monitor* JVMCI_lock                   = NULL;
 168 #endif
 169 
 170 
 171 #define MAX_NUM_MUTEX 128
 172 static Monitor * _mutex_array[MAX_NUM_MUTEX];
 173 static int _num_mutex;
 174 
 175 #ifdef ASSERT
 176 void assert_locked_or_safepoint(const Monitor * lock) {
 177   // check if this thread owns the lock (common case)
 178   if (IgnoreLockingAssertions) return;
 179   assert(lock != NULL, "Need non-NULL lock");
 180   if (lock->owned_by_self()) return;
 181   if (SafepointSynchronize::is_at_safepoint()) return;
 182   if (!Universe::is_fully_initialized()) return;
 183   // see if invoker of VM operation owns it
 184   VM_Operation* op = VMThread::vm_operation();
 185   if (op != NULL && op->calling_thread() == lock->owner()) return;
 186   fatal("must own lock %s", lock->name());
 187 }
 188 
 189 // a weaker assertion than the above
 190 void assert_locked_or_safepoint_weak(const Monitor * lock) {
 191   if (IgnoreLockingAssertions) return;
 192   assert(lock != NULL, "Need non-NULL lock");
 193   if (lock->is_locked()) return;
 194   if (SafepointSynchronize::is_at_safepoint()) return;
 195   if (!Universe::is_fully_initialized()) return;
 196   fatal("must own lock %s", lock->name());
 197 }
 198 
 199 // a stronger assertion than the above
 200 void assert_lock_strong(const Monitor * lock) {
 201   if (IgnoreLockingAssertions) return;
 202   assert(lock != NULL, "Need non-NULL lock");
 203   if (lock->owned_by_self()) return;
 204   fatal("must own lock %s", lock->name());
 205 }
 206 #endif
 207 
 208 #define def(var, type, pri, vm_block, safepoint_check_allowed ) {      \
 209   var = new type(Mutex::pri, #var, vm_block, safepoint_check_allowed); \
 210   assert(_num_mutex < MAX_NUM_MUTEX, "increase MAX_NUM_MUTEX");        \
 211   _mutex_array[_num_mutex++] = var;                                      \
 212 }
 213 
 214 // Using Padded subclasses to prevent false sharing of these global monitors and mutexes.
 215 void mutex_init() {
 216   def(tty_lock                     , PaddedMutex  , tty,         true,  Monitor::_safepoint_check_never);      // allow to lock in VM
 217 
 218   def(CGC_lock                     , PaddedMonitor, special,     true,  Monitor::_safepoint_check_never);      // coordinate between fore- and background GC
 219   def(STS_lock                     , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_never);
 220 
 221   def(VMGlobalAlloc_lock           , PaddedMutex  , oopstorage,  true,  Monitor::_safepoint_check_never);
 222   def(VMGlobalActive_lock          , PaddedMutex  , oopstorage-1,true,  Monitor::_safepoint_check_never);
 223 
 224   def(VMWeakAlloc_lock             , PaddedMutex  , oopstorage,  true,  Monitor::_safepoint_check_never);
 225   def(VMWeakActive_lock            , PaddedMutex  , oopstorage-1,true,  Monitor::_safepoint_check_never);
 226 
 227   def(StringTableWeakAlloc_lock    , PaddedMutex  , oopstorage,  true,  Monitor::_safepoint_check_never);
 228   def(StringTableWeakActive_lock   , PaddedMutex  , oopstorage-1,true,  Monitor::_safepoint_check_never);
 229 
 230   def(ResolvedMethodTableWeakAlloc_lock    , PaddedMutex  , oopstorage,   true,  Monitor::_safepoint_check_never);
 231   def(ResolvedMethodTableWeakActive_lock   , PaddedMutex  , oopstorage-1, true,  Monitor::_safepoint_check_never);
 232 
 233   def(NMethodKeepaliveAlloc_lock   , PaddedMutex  , oopstorage,   true,  Monitor::_safepoint_check_never);
 234   def(NMethodKeepaliveActive_lock  , PaddedMutex  , oopstorage-1, true,  Monitor::_safepoint_check_never);
 235 
 236   def(FullGCCount_lock             , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_never);      // in support of ExplicitGCInvokesConcurrent
 237   if (UseG1GC) {
 238     def(DirtyCardQ_CBL_mon         , PaddedMonitor, access,      true,  Monitor::_safepoint_check_never);
 239     def(Shared_DirtyCardQ_lock     , PaddedMutex  , access + 1,  true,  Monitor::_safepoint_check_never);
 240 
 241     def(FreeList_lock              , PaddedMutex  , leaf     ,   true,  Monitor::_safepoint_check_never);
 242     def(OldSets_lock               , PaddedMutex  , leaf     ,   true,  Monitor::_safepoint_check_never);
 243     def(RootRegionScan_lock        , PaddedMonitor, leaf     ,   true,  Monitor::_safepoint_check_never);
 244 
 245     def(StringDedupQueue_lock      , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_never);
 246     def(StringDedupTable_lock      , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 247 
 248     def(MarkStackFreeList_lock     , PaddedMutex  , leaf     ,   true,  Monitor::_safepoint_check_never);
 249     def(MarkStackChunkList_lock    , PaddedMutex  , leaf     ,   true,  Monitor::_safepoint_check_never);
 250 
 251     def(MonitoringSupport_lock     , PaddedMutex  , native   ,   true,  Monitor::_safepoint_check_never);      // used for serviceability monitoring support
 252   }
 253   if (UseShenandoahGC) {
 254     def(StringDedupQueue_lock      , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_never);
 255     def(StringDedupTable_lock      , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 256   }
 257   def(ParGCRareEvent_lock          , PaddedMutex  , leaf     ,   true,  Monitor::_safepoint_check_always);
 258   def(CGCPhaseManager_lock         , PaddedMonitor, leaf,        false, Monitor::_safepoint_check_always);
 259   def(CodeCache_lock               , PaddedMutex  , special,     true,  Monitor::_safepoint_check_never);
 260   def(RawMonitor_lock              , PaddedMutex  , special,     true,  Monitor::_safepoint_check_never);
 261   def(OopMapCacheAlloc_lock        , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_always); // used for oop_map_cache allocation.
 262 
 263   def(MetaspaceExpand_lock         , PaddedMutex  , leaf-1,      true,  Monitor::_safepoint_check_never);
 264   def(ClassLoaderDataGraph_lock    , PaddedMutex  , nonleaf,     true,  Monitor::_safepoint_check_always);
 265 
 266   def(Patching_lock                , PaddedMutex  , special,     true,  Monitor::_safepoint_check_never);      // used for safepointing and code patching.
 267   def(Service_lock                 , PaddedMonitor, special,     true,  Monitor::_safepoint_check_never);      // used for service thread operations
 268   def(JmethodIdCreation_lock       , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_always); // used for creating jmethodIDs.
 269 
 270   def(SystemDictionary_lock        , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_always);
 271   def(ProtectionDomainSet_lock     , PaddedMutex  , leaf-1,      true,  Monitor::_safepoint_check_never);
 272   def(SharedDictionary_lock        , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_always);
 273   def(Module_lock                  , PaddedMutex  , leaf+2,      true,  Monitor::_safepoint_check_always);
 274   def(InlineCacheBuffer_lock       , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 275   def(VMStatistic_lock             , PaddedMutex  , leaf,        false, Monitor::_safepoint_check_always);
 276   def(ExpandHeap_lock              , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_always); // Used during compilation by VM thread
 277   def(JNIHandleBlockFreeList_lock  , PaddedMutex  , leaf-1,      true,  Monitor::_safepoint_check_never);      // handles are used by VM thread
 278   def(SignatureHandlerLibrary_lock , PaddedMutex  , leaf,        false, Monitor::_safepoint_check_always);
 279   def(SymbolArena_lock             , PaddedMutex  , leaf+2,      true,  Monitor::_safepoint_check_never);
 280   def(ProfilePrint_lock            , PaddedMutex  , leaf,        false, Monitor::_safepoint_check_always); // serial profile printing
 281   def(ExceptionCache_lock          , PaddedMutex  , leaf,        false, Monitor::_safepoint_check_always); // serial profile printing
 282   def(OsrList_lock                 , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 283   def(Debug1_lock                  , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 284 #ifndef PRODUCT
 285   def(FullGCALot_lock              , PaddedMutex  , leaf,        false, Monitor::_safepoint_check_always); // a lock to make FullGCALot MT safe
 286 #endif
 287   def(BeforeExit_lock              , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_always);
 288   def(PerfDataMemAlloc_lock        , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_always); // used for allocating PerfData memory for performance data
 289   def(PerfDataManager_lock         , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_always); // used for synchronized access to PerfDataManager resources
 290 
 291   // CMS_modUnionTable_lock                   leaf
 292   // CMS_bitMap_lock                          leaf 1
 293   // CMS_freeList_lock                        leaf 2
 294 
 295   def(Threads_lock                 , PaddedMonitor, barrier,     true,  Monitor::_safepoint_check_always);  // Used for safepoint protocol.
 296   def(NonJavaThreadsList_lock      , PaddedMutex,   leaf,        true,  Monitor::_safepoint_check_never);
 297   def(NonJavaThreadsListSync_lock  , PaddedMutex,   leaf,        true,  Monitor::_safepoint_check_never);
 298 
 299   def(VMOperationQueue_lock        , PaddedMonitor, nonleaf,     true,  Monitor::_safepoint_check_never);  // VM_thread allowed to block on these
 300   def(VMOperationRequest_lock      , PaddedMonitor, nonleaf,     true,  Monitor::_safepoint_check_always);
 301   def(RetData_lock                 , PaddedMutex  , nonleaf,     false, Monitor::_safepoint_check_always);
 302   def(Terminator_lock              , PaddedMonitor, nonleaf,     true,  Monitor::_safepoint_check_always);
 303   def(InitCompleted_lock           , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_never);
 304   def(VtableStubs_lock             , PaddedMutex  , nonleaf,     true,  Monitor::_safepoint_check_never);
 305   def(Notify_lock                  , PaddedMonitor, nonleaf,     true,  Monitor::_safepoint_check_always);
 306   def(JNIGlobalAlloc_lock          , PaddedMutex  , nonleaf,     true,  Monitor::_safepoint_check_never);
 307   def(JNIGlobalActive_lock         , PaddedMutex  , nonleaf-1,   true,  Monitor::_safepoint_check_never);
 308   def(JNIWeakAlloc_lock            , PaddedMutex  , nonleaf,     true,  Monitor::_safepoint_check_never);
 309   def(JNIWeakActive_lock           , PaddedMutex  , nonleaf-1,   true,  Monitor::_safepoint_check_never);
 310   def(JNICritical_lock             , PaddedMonitor, nonleaf,     true,  Monitor::_safepoint_check_always); // used for JNI critical regions
 311   def(AdapterHandlerLibrary_lock   , PaddedMutex  , nonleaf,     true,  Monitor::_safepoint_check_always);
 312 
 313   def(Heap_lock                    , PaddedMonitor, nonleaf+1,   false, Monitor::_safepoint_check_sometimes);  // Doesn't safepoint check during termination.
 314   def(JfieldIdCreation_lock        , PaddedMutex  , nonleaf+1,   true,  Monitor::_safepoint_check_always); // jfieldID, Used in VM_Operation
 315 
 316   def(CompiledIC_lock              , PaddedMutex  , nonleaf+2,   false, Monitor::_safepoint_check_never);      // locks VtableStubs_lock, InlineCacheBuffer_lock
 317   def(CompileTaskAlloc_lock        , PaddedMutex  , nonleaf+2,   true,  Monitor::_safepoint_check_always);
 318   def(CompileStatistics_lock       , PaddedMutex  , nonleaf+2,   false, Monitor::_safepoint_check_always);
 319   def(DirectivesStack_lock         , PaddedMutex  , special,     true,  Monitor::_safepoint_check_never);
 320   def(MultiArray_lock              , PaddedMutex  , nonleaf+2,   false, Monitor::_safepoint_check_always);
 321 
 322   def(JvmtiThreadState_lock        , PaddedMutex  , nonleaf+2,   false, Monitor::_safepoint_check_always); // Used by JvmtiThreadState/JvmtiEventController
 323   def(Management_lock              , PaddedMutex  , nonleaf+2,   false, Monitor::_safepoint_check_always); // used for JVM management
 324 
 325   def(Compile_lock                 , PaddedMutex  , nonleaf+3,   true,  Monitor::_safepoint_check_always);
 326   def(MethodData_lock              , PaddedMutex  , nonleaf+3,   false, Monitor::_safepoint_check_always);
 327   def(TouchedMethodLog_lock        , PaddedMutex  , nonleaf+3,   false, Monitor::_safepoint_check_always);
 328 
 329   def(MethodCompileQueue_lock      , PaddedMonitor, nonleaf+4,   true,  Monitor::_safepoint_check_always);
 330   def(Debug2_lock                  , PaddedMutex  , nonleaf+4,   true,  Monitor::_safepoint_check_never);
 331   def(Debug3_lock                  , PaddedMutex  , nonleaf+4,   true,  Monitor::_safepoint_check_never);
 332   def(CompileThread_lock           , PaddedMonitor, nonleaf+5,   false, Monitor::_safepoint_check_always);
 333   def(PeriodicTask_lock            , PaddedMonitor, nonleaf+5,   true,  Monitor::_safepoint_check_always);
 334   def(RedefineClasses_lock         , PaddedMonitor, nonleaf+5,   true,  Monitor::_safepoint_check_always);
 335 
 336   if (WhiteBoxAPI) {
 337     def(Compilation_lock           , PaddedMonitor, leaf,        false, Monitor::_safepoint_check_never);
 338   }
 339 
 340 #if INCLUDE_JFR
 341   def(JfrMsg_lock                  , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_always);
 342   def(JfrBuffer_lock               , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 343   def(JfrStream_lock               , PaddedMutex  , leaf+1,      true,  Monitor::_safepoint_check_never);      // ensure to rank lower than 'safepoint'
 344   def(JfrStacktrace_lock           , PaddedMutex  , special,     true,  Monitor::_safepoint_check_never);
 345   def(JfrThreadSampler_lock        , PaddedMonitor, leaf,        true,  Monitor::_safepoint_check_never);
 346 #endif
 347 
 348 #ifndef SUPPORTS_NATIVE_CX8
 349   def(UnsafeJlong_lock             , PaddedMutex  , special,     false, Monitor::_safepoint_check_never);
 350 #endif
 351 
 352   def(CodeHeapStateAnalytics_lock  , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 353   def(NMethodSweeperStats_lock     , PaddedMutex  , special,     true,  Monitor::_safepoint_check_never);
 354   def(ThreadsSMRDelete_lock        , PaddedMonitor, special,     false, Monitor::_safepoint_check_never);
 355   def(SharedDecoder_lock           , PaddedMutex  , native,      false, Monitor::_safepoint_check_never);
 356   def(DCmdFactory_lock             , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 357 #if INCLUDE_NMT
 358   def(NMTQuery_lock                , PaddedMutex  , max_nonleaf, false, Monitor::_safepoint_check_always);
 359 #endif
 360 #if INCLUDE_CDS
 361 #if INCLUDE_JVMTI
 362   def(CDSClassFileStream_lock      , PaddedMutex  , max_nonleaf, false, Monitor::_safepoint_check_always);
 363 #endif
 364 
 365 #if INCLUDE_JVMCI
 366   def(JVMCI_lock                   , PaddedMonitor, nonleaf+2,   true,  Monitor::_safepoint_check_always);
 367 #endif
 368   def(DumpTimeTable_lock           , PaddedMutex  , leaf,        true,  Monitor::_safepoint_check_never);
 369 #endif // INCLUDE_CDS
 370 }
 371 
 372 GCMutexLocker::GCMutexLocker(Monitor * mutex) {
 373   if (SafepointSynchronize::is_at_safepoint()) {
 374     _locked = false;
 375   } else {
 376     _mutex = mutex;
 377     _locked = true;
 378     _mutex->lock();
 379   }
 380 }
 381 
 382 // Print all mutexes/monitors that are currently owned by a thread; called
 383 // by fatal error handler.
 384 void print_owned_locks_on_error(outputStream* st) {
 385   st->print("VM Mutex/Monitor currently owned by a thread: ");
 386   bool none = true;
 387   for (int i = 0; i < _num_mutex; i++) {
 388      // see if it has an owner
 389      if (_mutex_array[i]->owner() != NULL) {
 390        if (none) {
 391           // print format used by Mutex::print_on_error()
 392           st->print_cr(" ([mutex/lock_event])");
 393           none = false;
 394        }
 395        _mutex_array[i]->print_on_error(st);
 396        st->cr();
 397      }
 398   }
 399   if (none) st->print_cr("None");
 400 }