src/share/vm/prims/jvmtiExport.hpp

Wed, 27 Aug 2014 08:19:12 -0400

author
zgu
date
Wed, 27 Aug 2014 08:19:12 -0400
changeset 7074
833b0f92429a
parent 6198
55fb97c4c58d
child 6876
710a3c8b516e
child 7812
3c8b53552a43
permissions
-rw-r--r--

8046598: Scalable Native memory tracking development
Summary: Enhance scalability of native memory tracking
Reviewed-by: coleenp, ctornqvi, gtriantafill

     1 /*
     2  * Copyright (c) 1998, 2013, 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  */
    25 #ifndef SHARE_VM_PRIMS_JVMTIEXPORT_HPP
    26 #define SHARE_VM_PRIMS_JVMTIEXPORT_HPP
    28 #include "jvmtifiles/jvmti.h"
    29 #include "memory/allocation.hpp"
    30 #include "memory/iterator.hpp"
    31 #include "oops/oop.hpp"
    32 #include "oops/oopsHierarchy.hpp"
    33 #include "runtime/frame.hpp"
    34 #include "runtime/handles.hpp"
    35 #include "utilities/globalDefinitions.hpp"
    36 #include "utilities/growableArray.hpp"
    37 #include "utilities/macros.hpp"
    39 // Must be included after jvmti.h.
    40 #include "code/jvmticmlr.h"
    42 // Forward declarations
    44 class JvmtiEventControllerPrivate;
    45 class JvmtiManageCapabilities;
    46 class JvmtiEnv;
    47 class JvmtiThreadState;
    48 class AttachOperation;
    50 #define JVMTI_SUPPORT_FLAG(key)                                           \
    51   private:                                                                \
    52   static bool  _##key;                                                    \
    53   public:                                                                 \
    54   inline static void set_##key(bool on) {                                 \
    55     JVMTI_ONLY(_##key = (on != 0));                                       \
    56     NOT_JVMTI(report_unsupported(on));                                    \
    57   }                                                                       \
    58   inline static bool key() {                                              \
    59     JVMTI_ONLY(return _##key);                                            \
    60     NOT_JVMTI(return false);                                              \
    61   }
    64 // This class contains the JVMTI interface for the rest of hotspot.
    65 //
    66 class JvmtiExport : public AllStatic {
    67   friend class VMStructs;
    68   friend class CompileReplay;
    70  private:
    72 #if INCLUDE_JVMTI
    73   static int         _field_access_count;
    74   static int         _field_modification_count;
    76   static bool        _can_access_local_variables;
    77   static bool        _can_hotswap_or_post_breakpoint;
    78   static bool        _can_modify_any_class;
    79   static bool        _can_walk_any_space;
    80 #endif // INCLUDE_JVMTI
    82   JVMTI_SUPPORT_FLAG(can_get_source_debug_extension)
    83   JVMTI_SUPPORT_FLAG(can_maintain_original_method_order)
    84   JVMTI_SUPPORT_FLAG(can_post_interpreter_events)
    85   JVMTI_SUPPORT_FLAG(can_post_on_exceptions)
    86   JVMTI_SUPPORT_FLAG(can_post_breakpoint)
    87   JVMTI_SUPPORT_FLAG(can_post_field_access)
    88   JVMTI_SUPPORT_FLAG(can_post_field_modification)
    89   JVMTI_SUPPORT_FLAG(can_post_method_entry)
    90   JVMTI_SUPPORT_FLAG(can_post_method_exit)
    91   JVMTI_SUPPORT_FLAG(can_pop_frame)
    92   JVMTI_SUPPORT_FLAG(can_force_early_return)
    94   friend class JvmtiEventControllerPrivate;  // should only modify these flags
    95   JVMTI_SUPPORT_FLAG(should_post_single_step)
    96   JVMTI_SUPPORT_FLAG(should_post_field_access)
    97   JVMTI_SUPPORT_FLAG(should_post_field_modification)
    98   JVMTI_SUPPORT_FLAG(should_post_class_load)
    99   JVMTI_SUPPORT_FLAG(should_post_class_prepare)
   100   JVMTI_SUPPORT_FLAG(should_post_class_unload)
   101   JVMTI_SUPPORT_FLAG(should_post_native_method_bind)
   102   JVMTI_SUPPORT_FLAG(should_post_compiled_method_load)
   103   JVMTI_SUPPORT_FLAG(should_post_compiled_method_unload)
   104   JVMTI_SUPPORT_FLAG(should_post_dynamic_code_generated)
   105   JVMTI_SUPPORT_FLAG(should_post_monitor_contended_enter)
   106   JVMTI_SUPPORT_FLAG(should_post_monitor_contended_entered)
   107   JVMTI_SUPPORT_FLAG(should_post_monitor_wait)
   108   JVMTI_SUPPORT_FLAG(should_post_monitor_waited)
   109   JVMTI_SUPPORT_FLAG(should_post_data_dump)
   110   JVMTI_SUPPORT_FLAG(should_post_garbage_collection_start)
   111   JVMTI_SUPPORT_FLAG(should_post_garbage_collection_finish)
   112   JVMTI_SUPPORT_FLAG(should_post_on_exceptions)
   114   // ------ the below maybe don't have to be (but are for now)
   115   // fixed conditions here ------------
   116   // any events can be enabled
   117   JVMTI_SUPPORT_FLAG(should_post_thread_life)
   118   JVMTI_SUPPORT_FLAG(should_post_object_free)
   119   JVMTI_SUPPORT_FLAG(should_post_resource_exhausted)
   121   // we are holding objects on the heap - need to talk to GC - e.g.
   122   // breakpoint info
   123   JVMTI_SUPPORT_FLAG(should_clean_up_heap_objects)
   124   JVMTI_SUPPORT_FLAG(should_post_vm_object_alloc)
   126   // If flag cannot be implemented, give an error if on=true
   127   static void report_unsupported(bool on);
   129   // these should only be called by the friend class
   130   friend class JvmtiManageCapabilities;
   131   inline static void set_can_modify_any_class(bool on) {
   132     JVMTI_ONLY(_can_modify_any_class = (on != 0);)
   133   }
   134   inline static void set_can_access_local_variables(bool on) {
   135     JVMTI_ONLY(_can_access_local_variables = (on != 0);)
   136   }
   137   inline static void set_can_hotswap_or_post_breakpoint(bool on) {
   138     JVMTI_ONLY(_can_hotswap_or_post_breakpoint = (on != 0);)
   139   }
   140   inline static void set_can_walk_any_space(bool on) {
   141     JVMTI_ONLY(_can_walk_any_space = (on != 0);)
   142   }
   144   enum {
   145     JVMTI_VERSION_MASK   = 0x70000000,
   146     JVMTI_VERSION_VALUE  = 0x30000000,
   147     JVMDI_VERSION_VALUE  = 0x20000000
   148   };
   150   static void post_field_modification(JavaThread *thread, Method* method, address location,
   151                                       KlassHandle field_klass, Handle object, jfieldID field,
   152                                       char sig_type, jvalue *value);
   155   // posts a DynamicCodeGenerated event (internal/private implementation).
   156   // The public post_dynamic_code_generated* functions make use of the
   157   // internal implementation.  Also called from JvmtiDeferredEvent::post()
   158   static void post_dynamic_code_generated_internal(const char *name, const void *code_begin, const void *code_end) NOT_JVMTI_RETURN;
   160  private:
   162   // GenerateEvents support to allow posting of CompiledMethodLoad and
   163   // DynamicCodeGenerated events for a given environment.
   164   friend class JvmtiCodeBlobEvents;
   166   static void post_compiled_method_load(JvmtiEnv* env, const jmethodID method, const jint length,
   167                                         const void *code_begin, const jint map_length,
   168                                         const jvmtiAddrLocationMap* map) NOT_JVMTI_RETURN;
   169   static void post_dynamic_code_generated(JvmtiEnv* env, const char *name, const void *code_begin,
   170                                           const void *code_end) NOT_JVMTI_RETURN;
   172   // The RedefineClasses() API breaks some invariants in the "regular"
   173   // system. For example, there are sanity checks when GC'ing nmethods
   174   // that require the containing class to be unloading. However, when a
   175   // method is redefined, the old method and nmethod can become GC'able
   176   // without the containing class unloading. The state of becoming
   177   // GC'able can be asynchronous to the RedefineClasses() call since
   178   // the old method may still be running and cannot be GC'ed until
   179   // after all old invocations have finished. Additionally, a method
   180   // that has not been redefined may have an nmethod that depends on
   181   // the redefined method. The dependent nmethod will get deopted in
   182   // this case and may also be GC'able without the containing class
   183   // being unloaded.
   184   //
   185   // This flag indicates whether RedefineClasses() has ever redefined
   186   // one or more classes during the lifetime of the VM. The flag should
   187   // only be set by the friend class and can be queried by other sub
   188   // systems as needed to relax invariant checks.
   189   static bool _has_redefined_a_class;
   190   friend class VM_RedefineClasses;
   191   inline static void set_has_redefined_a_class() {
   192     JVMTI_ONLY(_has_redefined_a_class = true;)
   193   }
   194   // Flag to indicate if the compiler has recorded all dependencies. When the
   195   // can_redefine_classes capability is enabled in the OnLoad phase then the compiler
   196   // records all dependencies from startup. However if the capability is first
   197   // enabled some time later then the dependencies recorded by the compiler
   198   // are incomplete. This flag is used by RedefineClasses to know if the
   199   // dependency information is complete or not.
   200   static bool _all_dependencies_are_recorded;
   202  public:
   203   inline static bool has_redefined_a_class() {
   204     JVMTI_ONLY(return _has_redefined_a_class);
   205     NOT_JVMTI(return false);
   206   }
   208   inline static bool all_dependencies_are_recorded() {
   209     return _all_dependencies_are_recorded;
   210   }
   212   inline static void set_all_dependencies_are_recorded(bool on) {
   213     _all_dependencies_are_recorded = (on != 0);
   214   }
   217   // let JVMTI know that the JVM_OnLoad code is running
   218   static void enter_onload_phase() NOT_JVMTI_RETURN;
   220   // let JVMTI know that the VM isn't up yet (and JVM_OnLoad code isn't running)
   221   static void enter_primordial_phase() NOT_JVMTI_RETURN;
   223   // let JVMTI know that the VM isn't up yet but JNI is live
   224   static void enter_start_phase() NOT_JVMTI_RETURN;
   226   // let JVMTI know that the VM is fully up and running now
   227   static void enter_live_phase() NOT_JVMTI_RETURN;
   229   // ------ can_* conditions (below) are set at OnLoad and never changed ------------
   230   inline static bool can_modify_any_class()                       {
   231     JVMTI_ONLY(return _can_modify_any_class);
   232     NOT_JVMTI(return false);
   233   }
   234   inline static bool can_access_local_variables()                 {
   235     JVMTI_ONLY(return _can_access_local_variables);
   236     NOT_JVMTI(return false);
   237   }
   238   inline static bool can_hotswap_or_post_breakpoint()             {
   239     JVMTI_ONLY(return _can_hotswap_or_post_breakpoint);
   240     NOT_JVMTI(return false);
   241   }
   242   inline static bool can_walk_any_space()                         {
   243     JVMTI_ONLY(return _can_walk_any_space);
   244     NOT_JVMTI(return false);
   245   }
   247   // field access management
   248   static address  get_field_access_count_addr() NOT_JVMTI_RETURN_(0);
   250   // field modification management
   251   static address  get_field_modification_count_addr() NOT_JVMTI_RETURN_(0);
   253   // -----------------
   255   static bool is_jvmti_version(jint version)                      {
   256     JVMTI_ONLY(return (version & JVMTI_VERSION_MASK) == JVMTI_VERSION_VALUE);
   257     NOT_JVMTI(return false);
   258   }
   259   static bool is_jvmdi_version(jint version)                      {
   260     JVMTI_ONLY(return (version & JVMTI_VERSION_MASK) == JVMDI_VERSION_VALUE);
   261     NOT_JVMTI(return false);
   262   }
   263   static jint get_jvmti_interface(JavaVM *jvm, void **penv, jint version) NOT_JVMTI_RETURN_(0);
   264   static void decode_version_values(jint version, int * major, int * minor,
   265                                     int * micro) NOT_JVMTI_RETURN;
   267   // single stepping management methods
   268   static void at_single_stepping_point(JavaThread *thread, Method* method, address location) NOT_JVMTI_RETURN;
   269   static void expose_single_stepping(JavaThread *thread) NOT_JVMTI_RETURN;
   270   static bool hide_single_stepping(JavaThread *thread) NOT_JVMTI_RETURN_(false);
   272   // Methods that notify the debugger that something interesting has happened in the VM.
   273   static void post_vm_start              () NOT_JVMTI_RETURN;
   274   static void post_vm_initialized        () NOT_JVMTI_RETURN;
   275   static void post_vm_death              () NOT_JVMTI_RETURN;
   277   static void post_single_step           (JavaThread *thread, Method* method, address location) NOT_JVMTI_RETURN;
   278   static void post_raw_breakpoint        (JavaThread *thread, Method* method, address location) NOT_JVMTI_RETURN;
   280   static void post_exception_throw       (JavaThread *thread, Method* method, address location, oop exception) NOT_JVMTI_RETURN;
   281   static void notice_unwind_due_to_exception (JavaThread *thread, Method* method, address location, oop exception, bool in_handler_frame) NOT_JVMTI_RETURN;
   283   static oop jni_GetField_probe          (JavaThread *thread, jobject jobj,
   284     oop obj, Klass* klass, jfieldID fieldID, bool is_static)
   285     NOT_JVMTI_RETURN_(NULL);
   286   static oop jni_GetField_probe_nh       (JavaThread *thread, jobject jobj,
   287     oop obj, Klass* klass, jfieldID fieldID, bool is_static)
   288     NOT_JVMTI_RETURN_(NULL);
   289   static void post_field_access_by_jni   (JavaThread *thread, oop obj,
   290     Klass* klass, jfieldID fieldID, bool is_static) NOT_JVMTI_RETURN;
   291   static void post_field_access          (JavaThread *thread, Method* method,
   292     address location, KlassHandle field_klass, Handle object, jfieldID field) NOT_JVMTI_RETURN;
   293   static oop jni_SetField_probe          (JavaThread *thread, jobject jobj,
   294     oop obj, Klass* klass, jfieldID fieldID, bool is_static, char sig_type,
   295     jvalue *value) NOT_JVMTI_RETURN_(NULL);
   296   static oop jni_SetField_probe_nh       (JavaThread *thread, jobject jobj,
   297     oop obj, Klass* klass, jfieldID fieldID, bool is_static, char sig_type,
   298     jvalue *value) NOT_JVMTI_RETURN_(NULL);
   299   static void post_field_modification_by_jni(JavaThread *thread, oop obj,
   300     Klass* klass, jfieldID fieldID, bool is_static, char sig_type,
   301     jvalue *value);
   302   static void post_raw_field_modification(JavaThread *thread, Method* method,
   303     address location, KlassHandle field_klass, Handle object, jfieldID field,
   304     char sig_type, jvalue *value) NOT_JVMTI_RETURN;
   306   static void post_method_entry          (JavaThread *thread, Method* method, frame current_frame) NOT_JVMTI_RETURN;
   307   static void post_method_exit           (JavaThread *thread, Method* method, frame current_frame) NOT_JVMTI_RETURN;
   309   static void post_class_load            (JavaThread *thread, Klass* klass) NOT_JVMTI_RETURN;
   310   static void post_class_unload          (Klass* klass) NOT_JVMTI_RETURN;
   311   static void post_class_prepare         (JavaThread *thread, Klass* klass) NOT_JVMTI_RETURN;
   313   static void post_thread_start          (JavaThread *thread) NOT_JVMTI_RETURN;
   314   static void post_thread_end            (JavaThread *thread) NOT_JVMTI_RETURN;
   316   // Support for java.lang.instrument agent loading.
   317   static bool _should_post_class_file_load_hook;
   318   inline static void set_should_post_class_file_load_hook(bool on)     { _should_post_class_file_load_hook = on;  }
   319   inline static bool should_post_class_file_load_hook()           {
   320     JVMTI_ONLY(return _should_post_class_file_load_hook);
   321     NOT_JVMTI(return false;)
   322   }
   323   static void post_class_file_load_hook(Symbol* h_name, Handle class_loader,
   324                                         Handle h_protection_domain,
   325                                         unsigned char **data_ptr, unsigned char **end_ptr,
   326                                         JvmtiCachedClassFileData **cache_ptr) NOT_JVMTI_RETURN;
   327   static void post_native_method_bind(Method* method, address* function_ptr) NOT_JVMTI_RETURN;
   328   static void post_compiled_method_load(nmethod *nm) NOT_JVMTI_RETURN;
   329   static void post_dynamic_code_generated(const char *name, const void *code_begin, const void *code_end) NOT_JVMTI_RETURN;
   331   // used to post a CompiledMethodUnload event
   332   static void post_compiled_method_unload(jmethodID mid, const void *code_begin) NOT_JVMTI_RETURN;
   334   // similiar to post_dynamic_code_generated except that it can be used to
   335   // post a DynamicCodeGenerated event while holding locks in the VM. Any event
   336   // posted using this function is recorded by the enclosing event collector
   337   // -- JvmtiDynamicCodeEventCollector.
   338   static void post_dynamic_code_generated_while_holding_locks(const char* name, address code_begin, address code_end) NOT_JVMTI_RETURN;
   340   static void post_garbage_collection_finish() NOT_JVMTI_RETURN;
   341   static void post_garbage_collection_start() NOT_JVMTI_RETURN;
   342   static void post_data_dump() NOT_JVMTI_RETURN;
   343   static void post_monitor_contended_enter(JavaThread *thread, ObjectMonitor *obj_mntr) NOT_JVMTI_RETURN;
   344   static void post_monitor_contended_entered(JavaThread *thread, ObjectMonitor *obj_mntr) NOT_JVMTI_RETURN;
   345   static void post_monitor_wait(JavaThread *thread, oop obj, jlong timeout) NOT_JVMTI_RETURN;
   346   static void post_monitor_waited(JavaThread *thread, ObjectMonitor *obj_mntr, jboolean timed_out) NOT_JVMTI_RETURN;
   347   static void post_object_free(JvmtiEnv* env, jlong tag) NOT_JVMTI_RETURN;
   348   static void post_resource_exhausted(jint resource_exhausted_flags, const char* detail) NOT_JVMTI_RETURN;
   349   static void record_vm_internal_object_allocation(oop object) NOT_JVMTI_RETURN;
   350   // Post objects collected by vm_object_alloc_event_collector.
   351   static void post_vm_object_alloc(JavaThread *thread, oop object) NOT_JVMTI_RETURN;
   352   // Collects vm internal objects for later event posting.
   353   inline static void vm_object_alloc_event_collector(oop object) {
   354     if (should_post_vm_object_alloc()) {
   355       record_vm_internal_object_allocation(object);
   356     }
   357   }
   358   inline static void post_array_size_exhausted() {
   359     if (should_post_resource_exhausted()) {
   360       post_resource_exhausted(JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR,
   361                               "Requested array size exceeds VM limit");
   362     }
   363   }
   365   static void cleanup_thread             (JavaThread* thread) NOT_JVMTI_RETURN;
   367   static void oops_do(OopClosure* f) NOT_JVMTI_RETURN;
   368   static void weak_oops_do(BoolObjectClosure* b, OopClosure* f) NOT_JVMTI_RETURN;
   369   static void gc_epilogue() NOT_JVMTI_RETURN;
   371   static void transition_pending_onload_raw_monitors() NOT_JVMTI_RETURN;
   373   // attach support
   374   static jint load_agent_library(AttachOperation* op, outputStream* out) NOT_JVMTI_RETURN_(JNI_ERR);
   376   // SetNativeMethodPrefix support
   377   static char** get_all_native_method_prefixes(int* count_ptr) NOT_JVMTI_RETURN_(NULL);
   378 };
   380 // Support class used by JvmtiDynamicCodeEventCollector and others. It
   381 // describes a single code blob by name and address range.
   382 class JvmtiCodeBlobDesc : public CHeapObj<mtInternal> {
   383  private:
   384   char _name[64];
   385   address _code_begin;
   386   address _code_end;
   388  public:
   389   JvmtiCodeBlobDesc(const char *name, address code_begin, address code_end) {
   390     assert(name != NULL, "all code blobs must be named");
   391     strncpy(_name, name, sizeof(_name));
   392     _name[sizeof(_name)-1] = '\0';
   393     _code_begin = code_begin;
   394     _code_end = code_end;
   395   }
   396   char* name()                  { return _name; }
   397   address code_begin()          { return _code_begin; }
   398   address code_end()            { return _code_end; }
   399 };
   401 // JvmtiEventCollector is a helper class to setup thread for
   402 // event collection.
   403 class JvmtiEventCollector : public StackObj {
   404  private:
   405   JvmtiEventCollector* _prev;  // Save previous one to support nested event collector.
   407  public:
   408   void setup_jvmti_thread_state(); // Set this collector in current thread.
   409   void unset_jvmti_thread_state(); // Reset previous collector in current thread.
   410   virtual bool is_dynamic_code_event()   { return false; }
   411   virtual bool is_vm_object_alloc_event(){ return false; }
   412   JvmtiEventCollector *get_prev()        { return _prev; }
   413 };
   415 // A JvmtiDynamicCodeEventCollector is a helper class for the JvmtiExport
   416 // interface. It collects "dynamic code generated" events that are posted
   417 // while holding locks. When the event collector goes out of scope the
   418 // events will be posted.
   419 //
   420 // Usage :-
   421 //
   422 // {
   423 //   JvmtiDynamicCodeEventCollector event_collector;
   424 //   :
   425 //   { MutexLocker ml(...)
   426 //     :
   427 //     JvmtiExport::post_dynamic_code_generated_while_holding_locks(...)
   428 //   }
   429 //   // event collector goes out of scope => post events to profiler.
   430 // }
   432 class JvmtiDynamicCodeEventCollector : public JvmtiEventCollector {
   433  private:
   434   GrowableArray<JvmtiCodeBlobDesc*>* _code_blobs;           // collected code blob events
   436   friend class JvmtiExport;
   437   void register_stub(const char* name, address start, address end);
   439  public:
   440   JvmtiDynamicCodeEventCollector()  NOT_JVMTI_RETURN;
   441   ~JvmtiDynamicCodeEventCollector() NOT_JVMTI_RETURN;
   442   bool is_dynamic_code_event()   { return true; }
   444 };
   446 // Used to record vm internally allocated object oops and post
   447 // vm object alloc event for objects visible to java world.
   448 // Constructor enables JvmtiThreadState flag and all vm allocated
   449 // objects are recorded in a growable array. When destructor is
   450 // called the vm object alloc event is posted for each objects
   451 // visible to java world.
   452 // See jvm.cpp file for its usage.
   453 //
   454 class JvmtiVMObjectAllocEventCollector : public JvmtiEventCollector {
   455  private:
   456   GrowableArray<oop>* _allocated; // field to record vm internally allocated object oop.
   457   bool _enable;                   // This flag is enabled in constructor and disabled
   458                                   // in destructor before posting event. To avoid
   459                                   // collection of objects allocated while running java code inside
   460                                   // agent post_vm_object_alloc() event handler.
   462   //GC support
   463   void oops_do(OopClosure* f);
   465   friend class JvmtiExport;
   466   // Record vm allocated object oop.
   467   inline void record_allocation(oop obj);
   469   //GC support
   470   static void oops_do_for_all_threads(OopClosure* f);
   472  public:
   473   JvmtiVMObjectAllocEventCollector()  NOT_JVMTI_RETURN;
   474   ~JvmtiVMObjectAllocEventCollector() NOT_JVMTI_RETURN;
   475   bool is_vm_object_alloc_event()   { return true; }
   477   bool is_enabled()                 { return _enable; }
   478   void set_enabled(bool on)         { _enable = on; }
   479 };
   483 // Marker class to disable the posting of VMObjectAlloc events
   484 // within its scope.
   485 //
   486 // Usage :-
   487 //
   488 // {
   489 //   NoJvmtiVMObjectAllocMark njm;
   490 //   :
   491 //   // VMObjAlloc event will not be posted
   492 //   JvmtiExport::vm_object_alloc_event_collector(obj);
   493 //   :
   494 // }
   496 class NoJvmtiVMObjectAllocMark : public StackObj {
   497  private:
   498   // enclosing collector if enabled, NULL otherwise
   499   JvmtiVMObjectAllocEventCollector *_collector;
   501   bool was_enabled()    { return _collector != NULL; }
   503  public:
   504   NoJvmtiVMObjectAllocMark() NOT_JVMTI_RETURN;
   505   ~NoJvmtiVMObjectAllocMark() NOT_JVMTI_RETURN;
   506 };
   509 // Base class for reporting GC events to JVMTI.
   510 class JvmtiGCMarker : public StackObj {
   511  public:
   512   JvmtiGCMarker() NOT_JVMTI_RETURN;
   513   ~JvmtiGCMarker() NOT_JVMTI_RETURN;
   514 };
   516 // JvmtiHideSingleStepping is a helper class for hiding
   517 // internal single step events.
   518 class JvmtiHideSingleStepping : public StackObj {
   519  private:
   520   bool         _single_step_hidden;
   521   JavaThread * _thread;
   523  public:
   524   JvmtiHideSingleStepping(JavaThread * thread) {
   525     assert(thread != NULL, "sanity check");
   527     _single_step_hidden = false;
   528     _thread = thread;
   529     if (JvmtiExport::should_post_single_step()) {
   530       _single_step_hidden = JvmtiExport::hide_single_stepping(_thread);
   531     }
   532   }
   534   ~JvmtiHideSingleStepping() {
   535     if (_single_step_hidden) {
   536       JvmtiExport::expose_single_stepping(_thread);
   537     }
   538   }
   539 };
   541 #endif // SHARE_VM_PRIMS_JVMTIEXPORT_HPP

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