src/share/vm/prims/jvmtiExport.hpp

Mon, 26 Apr 2010 23:59:45 -0700

author
never
date
Mon, 26 Apr 2010 23:59:45 -0700
changeset 1832
b4776199210f
parent 1648
6deeaebad47a
child 1907
c18cbe5936b8
child 1932
852d0157c696
permissions
-rw-r--r--

6943485: JVMTI always on capabilities change code generation too much
Reviewed-by: twisti, dcubed

     1 /*
     2  * Copyright 1998-2010 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
    20  * CA 95054 USA or visit www.sun.com if you need additional information or
    21  * have any questions.
    22  *
    23  */
    25 #ifndef _JAVA_JVMTIEXPORT_H_
    26 #define _JAVA_JVMTIEXPORT_H_
    28 // Forward declarations
    30 class JvmtiEventControllerPrivate;
    31 class JvmtiManageCapabilities;
    32 class JvmtiEnv;
    33 class JvmtiThreadState;
    34 class AttachOperation;
    36 #ifndef JVMTI_KERNEL
    37 #define JVMTI_SUPPORT_FLAG(key)                                         \
    38   private:                                                              \
    39   static bool  _##key;                                                  \
    40   public:                                                               \
    41   inline static void set_##key(bool on)       { _##key = (on != 0); }   \
    42   inline static bool key()                    { return _##key; }
    43 #else  // JVMTI_KERNEL
    44 #define JVMTI_SUPPORT_FLAG(key)                                           \
    45   private:                                                                \
    46   const static bool _##key = false;                                       \
    47   public:                                                                 \
    48   inline static void set_##key(bool on)       { report_unsupported(on); } \
    49   inline static bool key()                    { return _##key; }
    50 #endif // JVMTI_KERNEL
    53 // This class contains the JVMTI interface for the rest of hotspot.
    54 //
    55 class JvmtiExport : public AllStatic {
    56  private:
    57   static int         _field_access_count;
    58   static int         _field_modification_count;
    60   static bool        _can_access_local_variables;
    61   static bool        _can_hotswap_or_post_breakpoint;
    62   static bool        _can_modify_any_class;
    63   static bool        _can_walk_any_space;
    65   JVMTI_SUPPORT_FLAG(can_get_source_debug_extension)
    66   JVMTI_SUPPORT_FLAG(can_maintain_original_method_order)
    67   JVMTI_SUPPORT_FLAG(can_post_interpreter_events)
    68   JVMTI_SUPPORT_FLAG(can_post_on_exceptions)
    69   JVMTI_SUPPORT_FLAG(can_post_breakpoint)
    70   JVMTI_SUPPORT_FLAG(can_post_field_access)
    71   JVMTI_SUPPORT_FLAG(can_post_field_modification)
    72   JVMTI_SUPPORT_FLAG(can_post_method_entry)
    73   JVMTI_SUPPORT_FLAG(can_post_method_exit)
    74   JVMTI_SUPPORT_FLAG(can_pop_frame)
    75   JVMTI_SUPPORT_FLAG(can_force_early_return)
    77   friend class JvmtiEventControllerPrivate;  // should only modify these flags
    78   JVMTI_SUPPORT_FLAG(should_post_single_step)
    79   JVMTI_SUPPORT_FLAG(should_post_field_access)
    80   JVMTI_SUPPORT_FLAG(should_post_field_modification)
    81   JVMTI_SUPPORT_FLAG(should_post_class_load)
    82   JVMTI_SUPPORT_FLAG(should_post_class_prepare)
    83   JVMTI_SUPPORT_FLAG(should_post_class_unload)
    84   JVMTI_SUPPORT_FLAG(should_post_native_method_bind)
    85   JVMTI_SUPPORT_FLAG(should_post_compiled_method_load)
    86   JVMTI_SUPPORT_FLAG(should_post_compiled_method_unload)
    87   JVMTI_SUPPORT_FLAG(should_post_dynamic_code_generated)
    88   JVMTI_SUPPORT_FLAG(should_post_monitor_contended_enter)
    89   JVMTI_SUPPORT_FLAG(should_post_monitor_contended_entered)
    90   JVMTI_SUPPORT_FLAG(should_post_monitor_wait)
    91   JVMTI_SUPPORT_FLAG(should_post_monitor_waited)
    92   JVMTI_SUPPORT_FLAG(should_post_data_dump)
    93   JVMTI_SUPPORT_FLAG(should_post_garbage_collection_start)
    94   JVMTI_SUPPORT_FLAG(should_post_garbage_collection_finish)
    95   JVMTI_SUPPORT_FLAG(should_post_on_exceptions)
    97   // ------ the below maybe don't have to be (but are for now)
    98   // fixed conditions here ------------
    99   // any events can be enabled
   100   JVMTI_SUPPORT_FLAG(should_post_thread_life)
   101   JVMTI_SUPPORT_FLAG(should_post_object_free)
   102   JVMTI_SUPPORT_FLAG(should_post_resource_exhausted)
   104   // we are holding objects on the heap - need to talk to GC - e.g.
   105   // breakpoint info
   106   JVMTI_SUPPORT_FLAG(should_clean_up_heap_objects)
   107   JVMTI_SUPPORT_FLAG(should_post_vm_object_alloc)
   109   // If flag cannot be implemented, give an error if on=true
   110   static void report_unsupported(bool on);
   112   // these should only be called by the friend class
   113   friend class JvmtiManageCapabilities;
   114   inline static void set_can_modify_any_class(bool on)                 { _can_modify_any_class = (on != 0); }
   115   inline static void set_can_access_local_variables(bool on)           { _can_access_local_variables = (on != 0); }
   116   inline static void set_can_hotswap_or_post_breakpoint(bool on)       { _can_hotswap_or_post_breakpoint = (on != 0); }
   117   inline static void set_can_walk_any_space(bool on)                   { _can_walk_any_space = (on != 0); }
   119   enum {
   120     JVMTI_VERSION_MASK   = 0x70000000,
   121     JVMTI_VERSION_VALUE  = 0x30000000,
   122     JVMDI_VERSION_VALUE  = 0x20000000
   123   };
   125   static void post_field_modification(JavaThread *thread, methodOop method, address location,
   126                                       KlassHandle field_klass, Handle object, jfieldID field,
   127                                       char sig_type, jvalue *value);
   130  private:
   131   // CompiledMethodUnload events are reported from the VM thread so they
   132   // are collected in lists (of jmethodID/addresses) and the events are posted later
   133   // from threads posting CompieldMethodLoad or DynamicCodeGenerated events.
   134   static bool _have_pending_compiled_method_unload_events;
   135   static GrowableArray<jmethodID>* _pending_compiled_method_unload_method_ids;
   136   static GrowableArray<const void *>* _pending_compiled_method_unload_code_begins;
   137   static JavaThread* _current_poster;
   139   // tests if there are CompiledMethodUnload events pending
   140   inline static bool have_pending_compiled_method_unload_events() {
   141     return _have_pending_compiled_method_unload_events;
   142   }
   144   // posts any pending CompiledMethodUnload events.
   145   static void post_pending_compiled_method_unload_events();
   147   // posts a DynamicCodeGenerated event (internal/private implementation).
   148   // The public post_dynamic_code_generated* functions make use of the
   149   // internal implementation.
   150   static void post_dynamic_code_generated_internal(const char *name, const void *code_begin, const void *code_end) KERNEL_RETURN;
   153   // GenerateEvents support to allow posting of CompiledMethodLoad and
   154   // DynamicCodeGenerated events for a given environment.
   155   friend class JvmtiCodeBlobEvents;
   157   static void post_compiled_method_load(JvmtiEnv* env, const jmethodID method, const jint length,
   158                                         const void *code_begin, const jint map_length,
   159                                         const jvmtiAddrLocationMap* map) KERNEL_RETURN;
   160   static void post_dynamic_code_generated(JvmtiEnv* env, const char *name, const void *code_begin,
   161                                           const void *code_end) KERNEL_RETURN;
   163   // The RedefineClasses() API breaks some invariants in the "regular"
   164   // system. For example, there are sanity checks when GC'ing nmethods
   165   // that require the containing class to be unloading. However, when a
   166   // method is redefined, the old method and nmethod can become GC'able
   167   // without the containing class unloading. The state of becoming
   168   // GC'able can be asynchronous to the RedefineClasses() call since
   169   // the old method may still be running and cannot be GC'ed until
   170   // after all old invocations have finished. Additionally, a method
   171   // that has not been redefined may have an nmethod that depends on
   172   // the redefined method. The dependent nmethod will get deopted in
   173   // this case and may also be GC'able without the containing class
   174   // being unloaded.
   175   //
   176   // This flag indicates whether RedefineClasses() has ever redefined
   177   // one or more classes during the lifetime of the VM. The flag should
   178   // only be set by the friend class and can be queried by other sub
   179   // systems as needed to relax invariant checks.
   180   static bool _has_redefined_a_class;
   181   friend class VM_RedefineClasses;
   182   inline static void set_has_redefined_a_class() {
   183     _has_redefined_a_class = true;
   184   }
   186   // Flag to indicate if the compiler has recorded all dependencies. When the
   187   // can_redefine_classes capability is enabled in the OnLoad phase then the compiler
   188   // records all dependencies from startup. However if the capability is first
   189   // enabled some time later then the dependencies recorded by the compiler
   190   // are incomplete. This flag is used by RedefineClasses to know if the
   191   // dependency information is complete or not.
   192   static bool _all_dependencies_are_recorded;
   194  public:
   195   inline static bool has_redefined_a_class() {
   196     return _has_redefined_a_class;
   197   }
   199   inline static bool all_dependencies_are_recorded() {
   200     return _all_dependencies_are_recorded;
   201   }
   203   inline static void set_all_dependencies_are_recorded(bool on) {
   204     _all_dependencies_are_recorded = (on != 0);
   205   }
   208   // let JVMTI know that the JVM_OnLoad code is running
   209   static void enter_onload_phase();
   211   // let JVMTI know that the VM isn't up yet (and JVM_OnLoad code isn't running)
   212   static void enter_primordial_phase();
   214   // let JVMTI know that the VM isn't up yet but JNI is live
   215   static void enter_start_phase();
   217   // let JVMTI know that the VM is fully up and running now
   218   static void enter_live_phase();
   220   // ------ can_* conditions (below) are set at OnLoad and never changed ------------
   221   inline static bool can_modify_any_class()                       { return _can_modify_any_class; }
   222   inline static bool can_access_local_variables()                 { return _can_access_local_variables; }
   223   inline static bool can_hotswap_or_post_breakpoint()             { return _can_hotswap_or_post_breakpoint; }
   224   inline static bool can_walk_any_space()                         { return _can_walk_any_space; }
   226   // field access management
   227   static address  get_field_access_count_addr();
   229   // field modification management
   230   static address  get_field_modification_count_addr();
   232   // -----------------
   234   static bool is_jvmti_version(jint version)                      { return (version & JVMTI_VERSION_MASK) == JVMTI_VERSION_VALUE; }
   235   static bool is_jvmdi_version(jint version)                      { return (version & JVMTI_VERSION_MASK) == JVMDI_VERSION_VALUE; }
   236   static jint get_jvmti_interface(JavaVM *jvm, void **penv, jint version);
   237   static void decode_version_values(jint version, int * major, int * minor,
   238                                     int * micro);
   240   // single stepping management methods
   241   static void at_single_stepping_point(JavaThread *thread, methodOop method, address location) KERNEL_RETURN;
   242   static void expose_single_stepping(JavaThread *thread) KERNEL_RETURN;
   243   static bool hide_single_stepping(JavaThread *thread) KERNEL_RETURN_(return false;);
   245   // Methods that notify the debugger that something interesting has happened in the VM.
   246   static void post_vm_start              ();
   247   static void post_vm_initialized        ();
   248   static void post_vm_death              ();
   250   static void post_single_step           (JavaThread *thread, methodOop method, address location) KERNEL_RETURN;
   251   static void post_raw_breakpoint        (JavaThread *thread, methodOop method, address location) KERNEL_RETURN;
   253   static void post_exception_throw       (JavaThread *thread, methodOop method, address location, oop exception) KERNEL_RETURN;
   254   static void notice_unwind_due_to_exception (JavaThread *thread, methodOop method, address location, oop exception, bool in_handler_frame) KERNEL_RETURN;
   256   static oop jni_GetField_probe          (JavaThread *thread, jobject jobj,
   257     oop obj, klassOop klass, jfieldID fieldID, bool is_static)
   258     KERNEL_RETURN_(return NULL;);
   259   static oop jni_GetField_probe_nh       (JavaThread *thread, jobject jobj,
   260     oop obj, klassOop klass, jfieldID fieldID, bool is_static)
   261     KERNEL_RETURN_(return NULL;);
   262   static void post_field_access_by_jni   (JavaThread *thread, oop obj,
   263     klassOop klass, jfieldID fieldID, bool is_static) KERNEL_RETURN;
   264   static void post_field_access          (JavaThread *thread, methodOop method,
   265     address location, KlassHandle field_klass, Handle object, jfieldID field) KERNEL_RETURN;
   266   static oop jni_SetField_probe          (JavaThread *thread, jobject jobj,
   267     oop obj, klassOop klass, jfieldID fieldID, bool is_static, char sig_type,
   268     jvalue *value) KERNEL_RETURN_(return NULL;);
   269   static oop jni_SetField_probe_nh       (JavaThread *thread, jobject jobj,
   270     oop obj, klassOop klass, jfieldID fieldID, bool is_static, char sig_type,
   271     jvalue *value) KERNEL_RETURN_(return NULL;);
   272   static void post_field_modification_by_jni(JavaThread *thread, oop obj,
   273     klassOop klass, jfieldID fieldID, bool is_static, char sig_type,
   274     jvalue *value);
   275   static void post_raw_field_modification(JavaThread *thread, methodOop method,
   276     address location, KlassHandle field_klass, Handle object, jfieldID field,
   277     char sig_type, jvalue *value) KERNEL_RETURN;
   279   static void post_method_entry          (JavaThread *thread, methodOop method, frame current_frame) KERNEL_RETURN;
   280   static void post_method_exit           (JavaThread *thread, methodOop method, frame current_frame) KERNEL_RETURN;
   282   static void post_class_load            (JavaThread *thread, klassOop klass) KERNEL_RETURN;
   283   static void post_class_unload          (klassOop klass) KERNEL_RETURN;
   284   static void post_class_prepare         (JavaThread *thread, klassOop klass) KERNEL_RETURN;
   286   static void post_thread_start          (JavaThread *thread) KERNEL_RETURN;
   287   static void post_thread_end            (JavaThread *thread) KERNEL_RETURN;
   289   // Support for java.lang.instrument agent loading.
   290   static bool _should_post_class_file_load_hook;
   291   inline static void set_should_post_class_file_load_hook(bool on)     { _should_post_class_file_load_hook = on;  }
   292   inline static bool should_post_class_file_load_hook()           { return _should_post_class_file_load_hook; }
   293   static void post_class_file_load_hook(symbolHandle h_name, Handle class_loader,
   294                                         Handle h_protection_domain,
   295                                         unsigned char **data_ptr, unsigned char **end_ptr,
   296                                         unsigned char **cached_data_ptr,
   297                                         jint *cached_length_ptr);
   298   static void post_native_method_bind(methodOop method, address* function_ptr) KERNEL_RETURN;
   299   static void post_compiled_method_load(nmethod *nm) KERNEL_RETURN;
   300   static void post_dynamic_code_generated(const char *name, const void *code_begin, const void *code_end) KERNEL_RETURN;
   302   // used at a safepoint to post a CompiledMethodUnload event
   303   static void post_compiled_method_unload_at_safepoint(jmethodID mid, const void *code_begin) KERNEL_RETURN;
   305   // similiar to post_dynamic_code_generated except that it can be used to
   306   // post a DynamicCodeGenerated event while holding locks in the VM. Any event
   307   // posted using this function is recorded by the enclosing event collector
   308   // -- JvmtiDynamicCodeEventCollector.
   309   static void post_dynamic_code_generated_while_holding_locks(const char* name, address code_begin, address code_end) KERNEL_RETURN;
   311   static void post_garbage_collection_finish() KERNEL_RETURN;
   312   static void post_garbage_collection_start() KERNEL_RETURN;
   313   static void post_data_dump() KERNEL_RETURN;
   314   static void post_monitor_contended_enter(JavaThread *thread, ObjectMonitor *obj_mntr) KERNEL_RETURN;
   315   static void post_monitor_contended_entered(JavaThread *thread, ObjectMonitor *obj_mntr) KERNEL_RETURN;
   316   static void post_monitor_wait(JavaThread *thread, oop obj, jlong timeout) KERNEL_RETURN;
   317   static void post_monitor_waited(JavaThread *thread, ObjectMonitor *obj_mntr, jboolean timed_out) KERNEL_RETURN;
   318   static void post_object_free(JvmtiEnv* env, jlong tag) KERNEL_RETURN;
   319   static void post_resource_exhausted(jint resource_exhausted_flags, const char* detail) KERNEL_RETURN;
   320   static void record_vm_internal_object_allocation(oop object) KERNEL_RETURN;
   321   // Post objects collected by vm_object_alloc_event_collector.
   322   static void post_vm_object_alloc(JavaThread *thread, oop object) KERNEL_RETURN;
   323   // Collects vm internal objects for later event posting.
   324   inline static void vm_object_alloc_event_collector(oop object) {
   325     if (should_post_vm_object_alloc()) {
   326       record_vm_internal_object_allocation(object);
   327     }
   328   }
   330   static void cleanup_thread             (JavaThread* thread) KERNEL_RETURN;
   332   static void oops_do(OopClosure* f) KERNEL_RETURN;
   334   static void transition_pending_onload_raw_monitors() KERNEL_RETURN;
   336 #ifndef SERVICES_KERNEL
   337   // attach support
   338   static jint load_agent_library(AttachOperation* op, outputStream* out);
   339 #endif // SERVICES_KERNEL
   341   // SetNativeMethodPrefix support
   342   static char** get_all_native_method_prefixes(int* count_ptr);
   344   // call after CMS has completed referencing processing
   345   static void cms_ref_processing_epilogue() KERNEL_RETURN;
   346 };
   348 // Support class used by JvmtiDynamicCodeEventCollector and others. It
   349 // describes a single code blob by name and address range.
   350 class JvmtiCodeBlobDesc : public CHeapObj {
   351  private:
   352   char _name[64];
   353   address _code_begin;
   354   address _code_end;
   356  public:
   357   JvmtiCodeBlobDesc(const char *name, address code_begin, address code_end) {
   358     assert(name != NULL, "all code blobs must be named");
   359     strncpy(_name, name, sizeof(_name));
   360     _name[sizeof(_name)-1] = '\0';
   361     _code_begin = code_begin;
   362     _code_end = code_end;
   363   }
   364   char* name()                  { return _name; }
   365   address code_begin()          { return _code_begin; }
   366   address code_end()            { return _code_end; }
   367 };
   369 // JvmtiEventCollector is a helper class to setup thread for
   370 // event collection.
   371 class JvmtiEventCollector : public StackObj {
   372  private:
   373   JvmtiEventCollector* _prev;  // Save previous one to support nested event collector.
   375  public:
   376   void setup_jvmti_thread_state(); // Set this collector in current thread.
   377   void unset_jvmti_thread_state(); // Reset previous collector in current thread.
   378   virtual bool is_dynamic_code_event()   { return false; }
   379   virtual bool is_vm_object_alloc_event(){ return false; }
   380   JvmtiEventCollector *get_prev()        { return _prev; }
   381 };
   383 // A JvmtiDynamicCodeEventCollector is a helper class for the JvmtiExport
   384 // interface. It collects "dynamic code generated" events that are posted
   385 // while holding locks. When the event collector goes out of scope the
   386 // events will be posted.
   387 //
   388 // Usage :-
   389 //
   390 // {
   391 //   JvmtiDynamicCodeEventCollector event_collector;
   392 //   :
   393 //   { MutexLocker ml(...)
   394 //     :
   395 //     JvmtiExport::post_dynamic_code_generated_while_holding_locks(...)
   396 //   }
   397 //   // event collector goes out of scope => post events to profiler.
   398 // }
   400 class JvmtiDynamicCodeEventCollector : public JvmtiEventCollector {
   401  private:
   402   GrowableArray<JvmtiCodeBlobDesc*>* _code_blobs;           // collected code blob events
   404   friend class JvmtiExport;
   405   void register_stub(const char* name, address start, address end);
   407  public:
   408   JvmtiDynamicCodeEventCollector()  KERNEL_RETURN;
   409   ~JvmtiDynamicCodeEventCollector() KERNEL_RETURN;
   410   bool is_dynamic_code_event()   { return true; }
   412 };
   414 // Used to record vm internally allocated object oops and post
   415 // vm object alloc event for objects visible to java world.
   416 // Constructor enables JvmtiThreadState flag and all vm allocated
   417 // objects are recorded in a growable array. When destructor is
   418 // called the vm object alloc event is posted for each objects
   419 // visible to java world.
   420 // See jvm.cpp file for its usage.
   421 //
   422 class JvmtiVMObjectAllocEventCollector : public JvmtiEventCollector {
   423  private:
   424   GrowableArray<oop>* _allocated; // field to record vm internally allocated object oop.
   425   bool _enable;                   // This flag is enabled in constructor and disabled
   426                                   // in destructor before posting event. To avoid
   427                                   // collection of objects allocated while running java code inside
   428                                   // agent post_vm_object_alloc() event handler.
   430   //GC support
   431   void oops_do(OopClosure* f);
   433   friend class JvmtiExport;
   434   // Record vm allocated object oop.
   435   inline void record_allocation(oop obj);
   437   //GC support
   438   static void oops_do_for_all_threads(OopClosure* f);
   440  public:
   441   JvmtiVMObjectAllocEventCollector()  KERNEL_RETURN;
   442   ~JvmtiVMObjectAllocEventCollector() KERNEL_RETURN;
   443   bool is_vm_object_alloc_event()   { return true; }
   445   bool is_enabled()                 { return _enable; }
   446   void set_enabled(bool on)         { _enable = on; }
   447 };
   451 // Marker class to disable the posting of VMObjectAlloc events
   452 // within its scope.
   453 //
   454 // Usage :-
   455 //
   456 // {
   457 //   NoJvmtiVMObjectAllocMark njm;
   458 //   :
   459 //   // VMObjAlloc event will not be posted
   460 //   JvmtiExport::vm_object_alloc_event_collector(obj);
   461 //   :
   462 // }
   464 class NoJvmtiVMObjectAllocMark : public StackObj {
   465  private:
   466   // enclosing collector if enabled, NULL otherwise
   467   JvmtiVMObjectAllocEventCollector *_collector;
   469   bool was_enabled()    { return _collector != NULL; }
   471  public:
   472   NoJvmtiVMObjectAllocMark() KERNEL_RETURN;
   473   ~NoJvmtiVMObjectAllocMark() KERNEL_RETURN;
   474 };
   477 // Base class for reporting GC events to JVMTI.
   478 class JvmtiGCMarker : public StackObj {
   479  private:
   480   bool _full;                           // marks a "full" GC
   481   unsigned int _invocation_count;       // GC invocation count
   482  protected:
   483   JvmtiGCMarker(bool full) KERNEL_RETURN;       // protected
   484   ~JvmtiGCMarker() KERNEL_RETURN;               // protected
   485 };
   488 // Support class used to report GC events to JVMTI. The class is stack
   489 // allocated and should be placed in the doit() implementation of all
   490 // vm operations that do a stop-the-world GC for failed allocation.
   491 //
   492 // Usage :-
   493 //
   494 // void VM_GenCollectForAllocation::doit() {
   495 //   JvmtiGCForAllocationMarker jgcm;
   496 //   :
   497 // }
   498 //
   499 // If jvmti is not enabled the constructor and destructor is essentially
   500 // a no-op (no overhead).
   501 //
   502 class JvmtiGCForAllocationMarker : public JvmtiGCMarker {
   503  public:
   504   JvmtiGCForAllocationMarker() : JvmtiGCMarker(false) {
   505   }
   506 };
   508 // Support class used to report GC events to JVMTI. The class is stack
   509 // allocated and should be placed in the doit() implementation of all
   510 // vm operations that do a "full" stop-the-world GC. This class differs
   511 // from JvmtiGCForAllocationMarker in that this class assumes that a
   512 // "full" GC will happen.
   513 //
   514 // Usage :-
   515 //
   516 // void VM_GenCollectFull::doit() {
   517 //   JvmtiGCFullMarker jgcm;
   518 //   :
   519 // }
   520 //
   521 class JvmtiGCFullMarker : public JvmtiGCMarker {
   522  public:
   523   JvmtiGCFullMarker() : JvmtiGCMarker(true) {
   524   }
   525 };
   528 // JvmtiHideSingleStepping is a helper class for hiding
   529 // internal single step events.
   530 class JvmtiHideSingleStepping : public StackObj {
   531  private:
   532   bool         _single_step_hidden;
   533   JavaThread * _thread;
   535  public:
   536   JvmtiHideSingleStepping(JavaThread * thread) {
   537     assert(thread != NULL, "sanity check");
   539     _single_step_hidden = false;
   540     _thread = thread;
   541     if (JvmtiExport::should_post_single_step()) {
   542       _single_step_hidden = JvmtiExport::hide_single_stepping(_thread);
   543     }
   544   }
   546   ~JvmtiHideSingleStepping() {
   547     if (_single_step_hidden) {
   548       JvmtiExport::expose_single_stepping(_thread);
   549     }
   550   }
   551 };
   553 #endif   /* _JAVA_JVMTIEXPORT_H_ */

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