Tue, 14 Jan 2014 12:44:12 +0100
8030662: "assert(counter_changed) failed: failed dependencies, but counter didn't change" still fails
Summary: Erroneously removed call to SystemDictionary::notice_modification() from jvmti with fix for 8029383
Reviewed-by: iveresov, twisti, kvn
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