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 /*

  * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "interpreter/interpreter.hpp"

 #include "jvmtifiles/jvmtiEnv.hpp"

 #include "memory/resourceArea.hpp"

 #include "oops/instanceKlass.hpp"

 #include "prims/jvmtiAgentThread.hpp"

 #include "prims/jvmtiEventController.inline.hpp"

 #include "prims/jvmtiImpl.hpp"

 #include "prims/jvmtiRedefineClasses.hpp"

 #include "runtime/deoptimization.hpp"

 #include "runtime/handles.hpp"

 #include "runtime/handles.inline.hpp"

 #include "runtime/interfaceSupport.hpp"

 #include "runtime/javaCalls.hpp"

 #include "runtime/signature.hpp"

 #include "runtime/vframe.hpp"

 #include "runtime/vframe_hp.hpp"

 #include "runtime/vm_operations.hpp"

 #include "utilities/exceptions.hpp"

 #ifdef TARGET_OS_FAMILY_linux

 # include "thread_linux.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_solaris

 # include "thread_solaris.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_windows

 # include "thread_windows.inline.hpp"

 #endif

 //

 // class JvmtiAgentThread

 //

 // JavaThread used to wrap a thread started by an agent

 // using the JVMTI method RunAgentThread.

 //

 JvmtiAgentThread::JvmtiAgentThread(JvmtiEnv* env, jvmtiStartFunction start_fn, const void *start_arg)

     : JavaThread(start_function_wrapper) {

     _env = env;

     _start_fn = start_fn;

     _start_arg = start_arg;

 }

 void

 JvmtiAgentThread::start_function_wrapper(JavaThread *thread, TRAPS) {

     // It is expected that any Agent threads will be created as

     // Java Threads.  If this is the case, notification of the creation

     // of the thread is given in JavaThread::thread_main().

     assert(thread->is_Java_thread(), "debugger thread should be a Java Thread");

     assert(thread == JavaThread::current(), "sanity check");

     JvmtiAgentThread *dthread = (JvmtiAgentThread *)thread;

     dthread->call_start_function();

 }

 void

 JvmtiAgentThread::call_start_function() {

     ThreadToNativeFromVM transition(this);

     _start_fn(_env->jvmti_external(), jni_environment(), (void*)_start_arg);

 }

 //

 // class GrowableCache - private methods

 //

 void GrowableCache::recache() {

   int len = _elements->length();

   FREE_C_HEAP_ARRAY(address, _cache);

   _cache = NEW_C_HEAP_ARRAY(address,len+1);

   for (int i=0; i<len; i++) {

     _cache[i] = _elements->at(i)->getCacheValue();

     //

     // The cache entry has gone bad. Without a valid frame pointer

     // value, the entry is useless so we simply delete it in product

     // mode. The call to remove() will rebuild the cache again

     // without the bad entry.

     //

     if (_cache[i] == NULL) {

       assert(false, "cannot recache NULL elements");

       remove(i);

       return;

     }

   }

   _cache[len] = NULL;

   _listener_fun(_this_obj,_cache);

 }

 bool GrowableCache::equals(void* v, GrowableElement *e2) {

   GrowableElement *e1 = (GrowableElement *) v;

   assert(e1 != NULL, "e1 != NULL");

   assert(e2 != NULL, "e2 != NULL");

   return e1->equals(e2);

 }

 //

 // class GrowableCache - public methods

 //

 GrowableCache::GrowableCache() {

   _this_obj       = NULL;

   _listener_fun   = NULL;

   _elements       = NULL;

   _cache          = NULL;

 }

 GrowableCache::~GrowableCache() {

   clear();

   delete _elements;

   FREE_C_HEAP_ARRAY(address, _cache);

 }

 void GrowableCache::initialize(void *this_obj, void listener_fun(void *, address*) ) {

   _this_obj       = this_obj;

   _listener_fun   = listener_fun;

   _elements       = new (ResourceObj::C_HEAP) GrowableArray<GrowableElement*>(5,true);

   recache();

 }

 // number of elements in the collection

 int GrowableCache::length() {

   return _elements->length();

 }

 // get the value of the index element in the collection

 GrowableElement* GrowableCache::at(int index) {

   GrowableElement *e = (GrowableElement *) _elements->at(index);

   assert(e != NULL, "e != NULL");

   return e;

 }

 int GrowableCache::find(GrowableElement* e) {

   return _elements->find(e, GrowableCache::equals);

 }

 // append a copy of the element to the end of the collection

 void GrowableCache::append(GrowableElement* e) {

   GrowableElement *new_e = e->clone();

   _elements->append(new_e);

   recache();

 }

 // insert a copy of the element using lessthan()

 void GrowableCache::insert(GrowableElement* e) {

   GrowableElement *new_e = e->clone();

   _elements->append(new_e);

   int n = length()-2;

   for (int i=n; i>=0; i--) {

     GrowableElement *e1 = _elements->at(i);

     GrowableElement *e2 = _elements->at(i+1);

     if (e2->lessThan(e1)) {

       _elements->at_put(i+1, e1);

       _elements->at_put(i,   e2);

     }

   }

   recache();

 }

 // remove the element at index

 void GrowableCache::remove (int index) {

   GrowableElement *e = _elements->at(index);

   assert(e != NULL, "e != NULL");

   _elements->remove(e);

   delete e;

   recache();

 }

 // clear out all elements, release all heap space and

 // let our listener know that things have changed.

 void GrowableCache::clear() {

   int len = _elements->length();

   for (int i=0; i<len; i++) {

     delete _elements->at(i);

   }

   _elements->clear();

   recache();

 }

 void GrowableCache::oops_do(OopClosure* f) {

   int len = _elements->length();

   for (int i=0; i<len; i++) {

     GrowableElement *e = _elements->at(i);

     e->oops_do(f);

   }

 }

 void GrowableCache::gc_epilogue() {

   int len = _elements->length();

   // recompute the new cache value after GC

   for (int i=0; i<len; i++) {

     _cache[i] = _elements->at(i)->getCacheValue();

   }

 }

 //

 // class JvmtiBreakpoint

 //

 JvmtiBreakpoint::JvmtiBreakpoint() {

   _method = NULL;

   _bci    = 0;

 #ifdef CHECK_UNHANDLED_OOPS

   // This one is always allocated with new, but check it just in case.

   Thread *thread = Thread::current();

   if (thread->is_in_stack((address)&_method)) {

     thread->allow_unhandled_oop((oop*)&_method);

   }

 #endif // CHECK_UNHANDLED_OOPS

 }

 JvmtiBreakpoint::JvmtiBreakpoint(methodOop m_method, jlocation location) {

   _method        = m_method;

   assert(_method != NULL, "_method != NULL");

   _bci           = (int) location;

 #ifdef CHECK_UNHANDLED_OOPS

   // Could be allocated with new and wouldn't be on the unhandled oop list.

   Thread *thread = Thread::current();

   if (thread->is_in_stack((address)&_method)) {

     thread->allow_unhandled_oop(&_method);

   }

 #endif // CHECK_UNHANDLED_OOPS

   assert(_bci >= 0, "_bci >= 0");

 }

 void JvmtiBreakpoint::copy(JvmtiBreakpoint& bp) {

   _method   = bp._method;

   _bci      = bp._bci;

 }

 bool JvmtiBreakpoint::lessThan(JvmtiBreakpoint& bp) {

   Unimplemented();

   return false;

 }

 bool JvmtiBreakpoint::equals(JvmtiBreakpoint& bp) {

   return _method   == bp._method

     &&   _bci      == bp._bci;

 }

 bool JvmtiBreakpoint::is_valid() {

   return _method != NULL &&

          _bci >= 0;

 }

 address JvmtiBreakpoint::getBcp() {

   return _method->bcp_from(_bci);

 }

 void JvmtiBreakpoint::each_method_version_do(method_action meth_act) {

   ((methodOopDesc*)_method->*meth_act)(_bci);

   // add/remove breakpoint to/from versions of the method that

   // are EMCP. Directly or transitively obsolete methods are

   // not saved in the PreviousVersionInfo.

   Thread *thread = Thread::current();

   instanceKlassHandle ikh = instanceKlassHandle(thread, _method->method_holder());

   symbolOop m_name = _method->name();

   symbolOop m_signature = _method->signature();

   {

     ResourceMark rm(thread);

     // PreviousVersionInfo objects returned via PreviousVersionWalker

     // contain a GrowableArray of handles. We have to clean up the

     // GrowableArray _after_ the PreviousVersionWalker destructor

     // has destroyed the handles.

     {

       // search previous versions if they exist

       PreviousVersionWalker pvw((instanceKlass *)ikh()->klass_part());

       for (PreviousVersionInfo * pv_info = pvw.next_previous_version();

            pv_info != NULL; pv_info = pvw.next_previous_version()) {

         GrowableArray<methodHandle>* methods =

           pv_info->prev_EMCP_method_handles();

         if (methods == NULL) {

           // We have run into a PreviousVersion generation where

           // all methods were made obsolete during that generation's

           // RedefineClasses() operation. At the time of that

           // operation, all EMCP methods were flushed so we don't

           // have to go back any further.

           //

           // A NULL methods array is different than an empty methods

           // array. We cannot infer any optimizations about older

           // generations from an empty methods array for the current

           // generation.

           break;

         }

         for (int i = methods->length() - 1; i >= 0; i--) {

           methodHandle method = methods->at(i);

           if (method->name() == m_name && method->signature() == m_signature) {

             RC_TRACE(0x00000800, ("%sing breakpoint in %s(%s)",

               meth_act == &methodOopDesc::set_breakpoint ? "sett" : "clear",

               method->name()->as_C_string(),

               method->signature()->as_C_string()));

             assert(!method->is_obsolete(), "only EMCP methods here");

             ((methodOopDesc*)method()->*meth_act)(_bci);

             break;

           }

         }

       }

     } // pvw is cleaned up

   } // rm is cleaned up

 }

 void JvmtiBreakpoint::set() {

   each_method_version_do(&methodOopDesc::set_breakpoint);

 }

 void JvmtiBreakpoint::clear() {

   each_method_version_do(&methodOopDesc::clear_breakpoint);

 }

 void JvmtiBreakpoint::print() {

 #ifndef PRODUCT

   const char *class_name  = (_method == NULL) ? "NULL" : _method->klass_name()->as_C_string();

   const char *method_name = (_method == NULL) ? "NULL" : _method->name()->as_C_string();

   tty->print("Breakpoint(%s,%s,%d,%p)",class_name, method_name, _bci, getBcp());

 #endif

 }

 //

 // class VM_ChangeBreakpoints

 //

 // Modify the Breakpoints data structure at a safepoint

 //

 void VM_ChangeBreakpoints::doit() {

   switch (_operation) {

   case SET_BREAKPOINT:

     _breakpoints->set_at_safepoint(*_bp);

     break;

   case CLEAR_BREAKPOINT:

     _breakpoints->clear_at_safepoint(*_bp);

     break;

   case CLEAR_ALL_BREAKPOINT:

     _breakpoints->clearall_at_safepoint();

     break;

   default:

     assert(false, "Unknown operation");

   }

 }

 void VM_ChangeBreakpoints::oops_do(OopClosure* f) {

   // This operation keeps breakpoints alive

   if (_breakpoints != NULL) {

     _breakpoints->oops_do(f);

   }

   if (_bp != NULL) {

     _bp->oops_do(f);

   }

 }

 //

 // class JvmtiBreakpoints

 //

 // a JVMTI internal collection of JvmtiBreakpoint

 //

 JvmtiBreakpoints::JvmtiBreakpoints(void listener_fun(void *,address *)) {

   _bps.initialize(this,listener_fun);

 }

 JvmtiBreakpoints:: ~JvmtiBreakpoints() {}

 void  JvmtiBreakpoints::oops_do(OopClosure* f) {

   _bps.oops_do(f);

 }

 void  JvmtiBreakpoints::gc_epilogue() {

   _bps.gc_epilogue();

 }

 void  JvmtiBreakpoints::print() {

 #ifndef PRODUCT

   ResourceMark rm;

   int n = _bps.length();

   for (int i=0; i<n; i++) {

     JvmtiBreakpoint& bp = _bps.at(i);

     tty->print("%d: ", i);

     bp.print();

     tty->print_cr("");

   }

 #endif

 }

 void JvmtiBreakpoints::set_at_safepoint(JvmtiBreakpoint& bp) {

   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

   int i = _bps.find(bp);

   if (i == -1) {

     _bps.append(bp);

     bp.set();

   }

 }

 void JvmtiBreakpoints::clear_at_safepoint(JvmtiBreakpoint& bp) {

   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

   int i = _bps.find(bp);

   if (i != -1) {

     _bps.remove(i);

     bp.clear();

   }

 }

 void JvmtiBreakpoints::clearall_at_safepoint() {

   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

   int len = _bps.length();

   for (int i=0; i<len; i++) {

     _bps.at(i).clear();

   }

   _bps.clear();

 }

 int JvmtiBreakpoints::length() { return _bps.length(); }

 int JvmtiBreakpoints::set(JvmtiBreakpoint& bp) {

   if ( _bps.find(bp) != -1) {

      return JVMTI_ERROR_DUPLICATE;

   }

   VM_ChangeBreakpoints set_breakpoint(this,VM_ChangeBreakpoints::SET_BREAKPOINT, &bp);

   VMThread::execute(&set_breakpoint);

   return JVMTI_ERROR_NONE;

 }

 int JvmtiBreakpoints::clear(JvmtiBreakpoint& bp) {

   if ( _bps.find(bp) == -1) {

      return JVMTI_ERROR_NOT_FOUND;

   }

   VM_ChangeBreakpoints clear_breakpoint(this,VM_ChangeBreakpoints::CLEAR_BREAKPOINT, &bp);

   VMThread::execute(&clear_breakpoint);

   return JVMTI_ERROR_NONE;

 }

 void JvmtiBreakpoints::clearall_in_class_at_safepoint(klassOop klass) {

   bool changed = true;

   // We are going to run thru the list of bkpts

   // and delete some.  This deletion probably alters

   // the list in some implementation defined way such

   // that when we delete entry i, the next entry might

   // no longer be at i+1.  To be safe, each time we delete

   // an entry, we'll just start again from the beginning.

   // We'll stop when we make a pass thru the whole list without

   // deleting anything.

   while (changed) {

     int len = _bps.length();

     changed = false;

     for (int i = 0; i < len; i++) {

       JvmtiBreakpoint& bp = _bps.at(i);

       if (bp.method()->method_holder() == klass) {

         bp.clear();

         _bps.remove(i);

         // This changed 'i' so we have to start over.

         changed = true;

         break;

       }

     }

   }

 }

 void JvmtiBreakpoints::clearall() {

   VM_ChangeBreakpoints clearall_breakpoint(this,VM_ChangeBreakpoints::CLEAR_ALL_BREAKPOINT);

   VMThread::execute(&clearall_breakpoint);

 }

 //

 // class JvmtiCurrentBreakpoints

 //

 JvmtiBreakpoints *JvmtiCurrentBreakpoints::_jvmti_breakpoints  = NULL;

 address *         JvmtiCurrentBreakpoints::_breakpoint_list    = NULL;

 JvmtiBreakpoints& JvmtiCurrentBreakpoints::get_jvmti_breakpoints() {

   if (_jvmti_breakpoints != NULL) return (*_jvmti_breakpoints);

   _jvmti_breakpoints = new JvmtiBreakpoints(listener_fun);

   assert(_jvmti_breakpoints != NULL, "_jvmti_breakpoints != NULL");

   return (*_jvmti_breakpoints);

 }

 void  JvmtiCurrentBreakpoints::listener_fun(void *this_obj, address *cache) {

   JvmtiBreakpoints *this_jvmti = (JvmtiBreakpoints *) this_obj;

   assert(this_jvmti != NULL, "this_jvmti != NULL");

   debug_only(int n = this_jvmti->length(););

   assert(cache[n] == NULL, "cache must be NULL terminated");

   set_breakpoint_list(cache);

 }

 void JvmtiCurrentBreakpoints::oops_do(OopClosure* f) {

   if (_jvmti_breakpoints != NULL) {

     _jvmti_breakpoints->oops_do(f);

   }

 }

 void JvmtiCurrentBreakpoints::gc_epilogue() {

   if (_jvmti_breakpoints != NULL) {

     _jvmti_breakpoints->gc_epilogue();

   }

 }

 ///////////////////////////////////////////////////////////////

 //

 // class VM_GetOrSetLocal

 //

 // Constructor for non-object getter

 VM_GetOrSetLocal::VM_GetOrSetLocal(JavaThread* thread, jint depth, int index, BasicType type)

   : _thread(thread)

   , _calling_thread(NULL)

   , _depth(depth)

   , _index(index)

   , _type(type)

   , _set(false)

   , _jvf(NULL)

   , _result(JVMTI_ERROR_NONE)

 {

 }

 // Constructor for object or non-object setter

 VM_GetOrSetLocal::VM_GetOrSetLocal(JavaThread* thread, jint depth, int index, BasicType type, jvalue value)

   : _thread(thread)

   , _calling_thread(NULL)

   , _depth(depth)

   , _index(index)

   , _type(type)

   , _value(value)

   , _set(true)

   , _jvf(NULL)

   , _result(JVMTI_ERROR_NONE)

 {

 }

 // Constructor for object getter

 VM_GetOrSetLocal::VM_GetOrSetLocal(JavaThread* thread, JavaThread* calling_thread, jint depth, int index)

   : _thread(thread)

   , _calling_thread(calling_thread)

   , _depth(depth)

   , _index(index)

   , _type(T_OBJECT)

   , _set(false)

   , _jvf(NULL)

   , _result(JVMTI_ERROR_NONE)

 {

 }

 vframe *VM_GetOrSetLocal::get_vframe() {

   if (!_thread->has_last_Java_frame()) {

     return NULL;

   }

   RegisterMap reg_map(_thread);

   vframe *vf = _thread->last_java_vframe(&reg_map);

   int d = 0;

   while ((vf != NULL) && (d < _depth)) {

     vf = vf->java_sender();

     d++;

   }

   return vf;

 }

 javaVFrame *VM_GetOrSetLocal::get_java_vframe() {

   vframe* vf = get_vframe();

   if (vf == NULL) {

     _result = JVMTI_ERROR_NO_MORE_FRAMES;

     return NULL;

   }

   javaVFrame *jvf = (javaVFrame*)vf;

   if (!vf->is_java_frame() || jvf->method()->is_native()) {

     _result = JVMTI_ERROR_OPAQUE_FRAME;

     return NULL;

   }

   return jvf;

 }

 // Check that the klass is assignable to a type with the given signature.

 // Another solution could be to use the function Klass::is_subtype_of(type).

 // But the type class can be forced to load/initialize eagerly in such a case.

 // This may cause unexpected consequences like CFLH or class-init JVMTI events.

 // It is better to avoid such a behavior.

 bool VM_GetOrSetLocal::is_assignable(const char* ty_sign, Klass* klass, Thread* thread) {

   assert(ty_sign != NULL, "type signature must not be NULL");

   assert(thread != NULL, "thread must not be NULL");

   assert(klass != NULL, "klass must not be NULL");

   int len = (int) strlen(ty_sign);

   if (ty_sign[0] == 'L' && ty_sign[len-1] == ';') { // Need pure class/interface name

     ty_sign++;

     len -= 2;

   }

   symbolHandle ty_sym = oopFactory::new_symbol_handle(ty_sign, len, thread);

   if (klass->name() == ty_sym()) {

     return true;

   }

   // Compare primary supers

   int super_depth = klass->super_depth();

   int idx;

   for (idx = 0; idx < super_depth; idx++) {

     if (Klass::cast(klass->primary_super_of_depth(idx))->name() == ty_sym()) {

       return true;

     }

   }

   // Compare secondary supers

   objArrayOop sec_supers = klass->secondary_supers();

   for (idx = 0; idx < sec_supers->length(); idx++) {

     if (Klass::cast((klassOop) sec_supers->obj_at(idx))->name() == ty_sym()) {

       return true;

     }

   }

   return false;

 }

 // Checks error conditions:

 //   JVMTI_ERROR_INVALID_SLOT

 //   JVMTI_ERROR_TYPE_MISMATCH

 // Returns: 'true' - everything is Ok, 'false' - error code

 bool VM_GetOrSetLocal::check_slot_type(javaVFrame* jvf) {

   methodOop method_oop = jvf->method();

   if (!method_oop->has_localvariable_table()) {

     // Just to check index boundaries

     jint extra_slot = (_type == T_LONG || _type == T_DOUBLE) ? 1 : 0;

     if (_index < 0 || _index + extra_slot >= method_oop->max_locals()) {

       _result = JVMTI_ERROR_INVALID_SLOT;

       return false;

     }

     return true;

   }

   jint num_entries = method_oop->localvariable_table_length();

   if (num_entries == 0) {

     _result = JVMTI_ERROR_INVALID_SLOT;

     return false;       // There are no slots

   }

   int signature_idx = -1;

   int vf_bci = jvf->bci();

   LocalVariableTableElement* table = method_oop->localvariable_table_start();

   for (int i = 0; i < num_entries; i++) {

     int start_bci = table[i].start_bci;

     int end_bci = start_bci + table[i].length;

     // Here we assume that locations of LVT entries

     // with the same slot number cannot be overlapped

     if (_index == (jint) table[i].slot && start_bci <= vf_bci && vf_bci <= end_bci) {

       signature_idx = (int) table[i].descriptor_cp_index;

       break;

     }

   }

   if (signature_idx == -1) {

     _result = JVMTI_ERROR_INVALID_SLOT;

     return false;       // Incorrect slot index

   }

   symbolOop   sign_sym  = method_oop->constants()->symbol_at(signature_idx);

   const char* signature = (const char *) sign_sym->as_utf8();

   BasicType slot_type = char2type(signature[0]);

   switch (slot_type) {

   case T_BYTE:

   case T_SHORT:

   case T_CHAR:

   case T_BOOLEAN:

     slot_type = T_INT;

     break;

   case T_ARRAY:

     slot_type = T_OBJECT;

     break;

   };

   if (_type != slot_type) {

     _result = JVMTI_ERROR_TYPE_MISMATCH;

     return false;

   }

   jobject jobj = _value.l;

   if (_set && slot_type == T_OBJECT && jobj != NULL) { // NULL reference is allowed

     // Check that the jobject class matches the return type signature.

     JavaThread* cur_thread = JavaThread::current();

     HandleMark hm(cur_thread);

     Handle obj = Handle(cur_thread, JNIHandles::resolve_external_guard(jobj));

     NULL_CHECK(obj, (_result = JVMTI_ERROR_INVALID_OBJECT, false));

     KlassHandle ob_kh = KlassHandle(cur_thread, obj->klass());

     NULL_CHECK(ob_kh, (_result = JVMTI_ERROR_INVALID_OBJECT, false));

     if (!is_assignable(signature, Klass::cast(ob_kh()), cur_thread)) {

       _result = JVMTI_ERROR_TYPE_MISMATCH;

       return false;

     }

   }

   return true;

 }

 static bool can_be_deoptimized(vframe* vf) {

   return (vf->is_compiled_frame() && vf->fr().can_be_deoptimized());

 }

 bool VM_GetOrSetLocal::doit_prologue() {

   _jvf = get_java_vframe();

   NULL_CHECK(_jvf, false);

   if (!check_slot_type(_jvf)) {

     return false;

   }

   return true;

 }

 void VM_GetOrSetLocal::doit() {

   if (_set) {

     // Force deoptimization of frame if compiled because it's

     // possible the compiler emitted some locals as constant values,

     // meaning they are not mutable.

     if (can_be_deoptimized(_jvf)) {

       // Schedule deoptimization so that eventually the local

       // update will be written to an interpreter frame.

       Deoptimization::deoptimize_frame(_jvf->thread(), _jvf->fr().id());

       // Now store a new value for the local which will be applied

       // once deoptimization occurs. Note however that while this

       // write is deferred until deoptimization actually happens

       // can vframe created after this point will have its locals

       // reflecting this update so as far as anyone can see the

       // write has already taken place.

       // If we are updating an oop then get the oop from the handle

       // since the handle will be long gone by the time the deopt

       // happens. The oop stored in the deferred local will be

       // gc'd on its own.

       if (_type == T_OBJECT) {

         _value.l = (jobject) (JNIHandles::resolve_external_guard(_value.l));

       }

       // Re-read the vframe so we can see that it is deoptimized

       // [ Only need because of assert in update_local() ]

       _jvf = get_java_vframe();

       ((compiledVFrame*)_jvf)->update_local(_type, _index, _value);

       return;

     }

     StackValueCollection *locals = _jvf->locals();

     HandleMark hm;

     switch (_type) {

     case T_INT:    locals->set_int_at   (_index, _value.i); break;

     case T_LONG:   locals->set_long_at  (_index, _value.j); break;

     case T_FLOAT:  locals->set_float_at (_index, _value.f); break;

     case T_DOUBLE: locals->set_double_at(_index, _value.d); break;

     case T_OBJECT: {

       Handle ob_h(JNIHandles::resolve_external_guard(_value.l));

       locals->set_obj_at (_index, ob_h);

       break;

     }

     default: ShouldNotReachHere();

     }

     _jvf->set_locals(locals);

   } else {

     StackValueCollection *locals = _jvf->locals();

     if (locals->at(_index)->type() == T_CONFLICT) {

       memset(&_value, 0, sizeof(_value));

       _value.l = NULL;

       return;

     }

     switch (_type) {

     case T_INT:    _value.i = locals->int_at   (_index);   break;

     case T_LONG:   _value.j = locals->long_at  (_index);   break;

     case T_FLOAT:  _value.f = locals->float_at (_index);   break;

     case T_DOUBLE: _value.d = locals->double_at(_index);   break;

     case T_OBJECT: {

       // Wrap the oop to be returned in a local JNI handle since

       // oops_do() no longer applies after doit() is finished.

       oop obj = locals->obj_at(_index)();

       _value.l = JNIHandles::make_local(_calling_thread, obj);

       break;

     }

     default: ShouldNotReachHere();

     }

   }

 }

 bool VM_GetOrSetLocal::allow_nested_vm_operations() const {

   return true; // May need to deoptimize

 }

 /////////////////////////////////////////////////////////////////////////////////////////

 //

 // class JvmtiSuspendControl - see comments in jvmtiImpl.hpp

 //

 bool JvmtiSuspendControl::suspend(JavaThread *java_thread) {

   // external suspend should have caught suspending a thread twice

   // Immediate suspension required for JPDA back-end so JVMTI agent threads do

   // not deadlock due to later suspension on transitions while holding

   // raw monitors.  Passing true causes the immediate suspension.

   // java_suspend() will catch threads in the process of exiting

   // and will ignore them.

   java_thread->java_suspend();

   // It would be nice to have the following assertion in all the time,

   // but it is possible for a racing resume request to have resumed

   // this thread right after we suspended it. Temporarily enable this

   // assertion if you are chasing a different kind of bug.

   //

   // assert(java_lang_Thread::thread(java_thread->threadObj()) == NULL ||

   //   java_thread->is_being_ext_suspended(), "thread is not suspended");

   if (java_lang_Thread::thread(java_thread->threadObj()) == NULL) {

     // check again because we can get delayed in java_suspend():

     // the thread is in process of exiting.

     return false;

   }

   return true;

 }

 bool JvmtiSuspendControl::resume(JavaThread *java_thread) {

   // external suspend should have caught resuming a thread twice

   assert(java_thread->is_being_ext_suspended(), "thread should be suspended");

   // resume thread

   {

     // must always grab Threads_lock, see JVM_SuspendThread

     MutexLocker ml(Threads_lock);

     java_thread->java_resume();

   }

   return true;

 }

 void JvmtiSuspendControl::print() {

 #ifndef PRODUCT

   MutexLocker mu(Threads_lock);

   ResourceMark rm;

   tty->print("Suspended Threads: [");

   for (JavaThread *thread = Threads::first(); thread != NULL; thread = thread->next()) {

 #if JVMTI_TRACE

     const char *name   = JvmtiTrace::safe_get_thread_name(thread);

 #else

     const char *name   = "";

 #endif /*JVMTI_TRACE */

     tty->print("%s(%c ", name, thread->is_being_ext_suspended() ? 'S' : '_');

     if (!thread->has_last_Java_frame()) {

       tty->print("no stack");

     }

     tty->print(") ");

   }

   tty->print_cr("]");

 #endif

 }