Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * 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 "memory/allocation.hpp"

 #include "memory/heapInspection.hpp"

 #include "memory/oopFactory.hpp"

 #include "oops/instanceKlass.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/handles.inline.hpp"

 #include "runtime/init.hpp"

 #include "runtime/thread.hpp"

 #include "runtime/vframe.hpp"

 #include "runtime/vmThread.hpp"

 #include "runtime/vm_operations.hpp"

 #include "services/threadService.hpp"

 // TODO: we need to define a naming convention for perf counters

 // to distinguish counters for:

 //   - standard JSR174 use

 //   - Hotspot extension (public and committed)

 //   - Hotspot extension (private/internal and uncommitted)

 // Default is disabled.

 bool ThreadService::_thread_monitoring_contention_enabled = false;

 bool ThreadService::_thread_cpu_time_enabled = false;

 PerfCounter*  ThreadService::_total_threads_count = NULL;

 PerfVariable* ThreadService::_live_threads_count = NULL;

 PerfVariable* ThreadService::_peak_threads_count = NULL;

 PerfVariable* ThreadService::_daemon_threads_count = NULL;

 volatile int ThreadService::_exiting_threads_count = 0;

 volatile int ThreadService::_exiting_daemon_threads_count = 0;

 ThreadDumpResult* ThreadService::_threaddump_list = NULL;

 static const int INITIAL_ARRAY_SIZE = 10;

 void ThreadService::init() {

   EXCEPTION_MARK;

   // These counters are for java.lang.management API support.

   // They are created even if -XX:-UsePerfData is set and in

   // that case, they will be allocated on C heap.

   _total_threads_count =

                 PerfDataManager::create_counter(JAVA_THREADS, "started",

                                                 PerfData::U_Events, CHECK);

   _live_threads_count =

                 PerfDataManager::create_variable(JAVA_THREADS, "live",

                                                  PerfData::U_None, CHECK);

   _peak_threads_count =

                 PerfDataManager::create_variable(JAVA_THREADS, "livePeak",

                                                  PerfData::U_None, CHECK);

   _daemon_threads_count =

                 PerfDataManager::create_variable(JAVA_THREADS, "daemon",

                                                  PerfData::U_None, CHECK);

   if (os::is_thread_cpu_time_supported()) {

     _thread_cpu_time_enabled = true;

   }

 }

 void ThreadService::reset_peak_thread_count() {

   // Acquire the lock to update the peak thread count

   // to synchronize with thread addition and removal.

   MutexLockerEx mu(Threads_lock);

   _peak_threads_count->set_value(get_live_thread_count());

 }

 void ThreadService::add_thread(JavaThread* thread, bool daemon) {

   // Do not count VM internal or JVMTI agent threads

   if (thread->is_hidden_from_external_view() ||

       thread->is_jvmti_agent_thread()) {

     return;

   }

   _total_threads_count->inc();

   _live_threads_count->inc();

   if (_live_threads_count->get_value() > _peak_threads_count->get_value()) {

     _peak_threads_count->set_value(_live_threads_count->get_value());

   }

   if (daemon) {

     _daemon_threads_count->inc();

   }

 }

 void ThreadService::remove_thread(JavaThread* thread, bool daemon) {

   Atomic::dec((jint*) &_exiting_threads_count);

   if (thread->is_hidden_from_external_view() ||

       thread->is_jvmti_agent_thread()) {

     return;

   }

   _live_threads_count->set_value(_live_threads_count->get_value() - 1);

   if (daemon) {

     _daemon_threads_count->set_value(_daemon_threads_count->get_value() - 1);

     Atomic::dec((jint*) &_exiting_daemon_threads_count);

   }

 }

 void ThreadService::current_thread_exiting(JavaThread* jt) {

   assert(jt == JavaThread::current(), "Called by current thread");

   Atomic::inc((jint*) &_exiting_threads_count);

   oop threadObj = jt->threadObj();

   if (threadObj != NULL && java_lang_Thread::is_daemon(threadObj)) {

     Atomic::inc((jint*) &_exiting_daemon_threads_count);

   }

 }

 // FIXME: JVMTI should call this function

 Handle ThreadService::get_current_contended_monitor(JavaThread* thread) {

   assert(thread != NULL, "should be non-NULL");

   assert(Threads_lock->owned_by_self(), "must grab Threads_lock or be at safepoint");

   ObjectMonitor *wait_obj = thread->current_waiting_monitor();

   oop obj = NULL;

   if (wait_obj != NULL) {

     // thread is doing an Object.wait() call

     obj = (oop) wait_obj->object();

     assert(obj != NULL, "Object.wait() should have an object");

   } else {

     ObjectMonitor *enter_obj = thread->current_pending_monitor();

     if (enter_obj != NULL) {

       // thread is trying to enter() or raw_enter() an ObjectMonitor.

       obj = (oop) enter_obj->object();

     }

     // If obj == NULL, then ObjectMonitor is raw which doesn't count.

   }

   Handle h(obj);

   return h;

 }

 bool ThreadService::set_thread_monitoring_contention(bool flag) {

   MutexLocker m(Management_lock);

   bool prev = _thread_monitoring_contention_enabled;

   _thread_monitoring_contention_enabled = flag;

   return prev;

 }

 bool ThreadService::set_thread_cpu_time_enabled(bool flag) {

   MutexLocker m(Management_lock);

   bool prev = _thread_cpu_time_enabled;

   _thread_cpu_time_enabled = flag;

   return prev;

 }

 // GC support

 void ThreadService::oops_do(OopClosure* f) {

   for (ThreadDumpResult* dump = _threaddump_list; dump != NULL; dump = dump->next()) {

     dump->oops_do(f);

   }

 }

 void ThreadService::add_thread_dump(ThreadDumpResult* dump) {

   MutexLocker ml(Management_lock);

   if (_threaddump_list == NULL) {

     _threaddump_list = dump;

   } else {

     dump->set_next(_threaddump_list);

     _threaddump_list = dump;

   }

 }

 void ThreadService::remove_thread_dump(ThreadDumpResult* dump) {

   MutexLocker ml(Management_lock);

   ThreadDumpResult* prev = NULL;

   bool found = false;

   for (ThreadDumpResult* d = _threaddump_list; d != NULL; prev = d, d = d->next()) {

     if (d == dump) {

       if (prev == NULL) {

         _threaddump_list = dump->next();

       } else {

         prev->set_next(dump->next());

       }

       found = true;

       break;

     }

   }

   assert(found, "The threaddump result to be removed must exist.");

 }

 // Dump stack trace of threads specified in the given threads array.

 // Returns StackTraceElement[][] each element is the stack trace of a thread in

 // the corresponding entry in the given threads array

 Handle ThreadService::dump_stack_traces(GrowableArray<instanceHandle>* threads,

                                         int num_threads,

                                         TRAPS) {

   assert(num_threads > 0, "just checking");

   ThreadDumpResult dump_result;

   VM_ThreadDump op(&dump_result,

                    threads,

                    num_threads,

                    -1,    /* entire stack */

                    false, /* with locked monitors */

                    false  /* with locked synchronizers */);

   VMThread::execute(&op);

   // Allocate the resulting StackTraceElement[][] object

   ResourceMark rm(THREAD);

   klassOop k = SystemDictionary::resolve_or_fail(vmSymbolHandles::java_lang_StackTraceElement_array(), true, CHECK_NH);

   objArrayKlassHandle ik (THREAD, k);

   objArrayOop r = oopFactory::new_objArray(ik(), num_threads, CHECK_NH);

   objArrayHandle result_obj(THREAD, r);

   int num_snapshots = dump_result.num_snapshots();

   assert(num_snapshots == num_threads, "Must have num_threads thread snapshots");

   int i = 0;

   for (ThreadSnapshot* ts = dump_result.snapshots(); ts != NULL; i++, ts = ts->next()) {

     ThreadStackTrace* stacktrace = ts->get_stack_trace();

     if (stacktrace == NULL) {

       // No stack trace

       result_obj->obj_at_put(i, NULL);

     } else {

       // Construct an array of java/lang/StackTraceElement object

       Handle backtrace_h = stacktrace->allocate_fill_stack_trace_element_array(CHECK_NH);

       result_obj->obj_at_put(i, backtrace_h());

     }

   }

   return result_obj;

 }

 void ThreadService::reset_contention_count_stat(JavaThread* thread) {

   ThreadStatistics* stat = thread->get_thread_stat();

   if (stat != NULL) {

     stat->reset_count_stat();

   }

 }

 void ThreadService::reset_contention_time_stat(JavaThread* thread) {

   ThreadStatistics* stat = thread->get_thread_stat();

   if (stat != NULL) {

     stat->reset_time_stat();

   }

 }

 // Find deadlocks involving object monitors and concurrent locks if concurrent_locks is true

 DeadlockCycle* ThreadService::find_deadlocks_at_safepoint(bool concurrent_locks) {

   // This code was modified from the original Threads::find_deadlocks code.

   int globalDfn = 0, thisDfn;

   ObjectMonitor* waitingToLockMonitor = NULL;

   oop waitingToLockBlocker = NULL;

   bool blocked_on_monitor = false;

   JavaThread *currentThread, *previousThread;

   int num_deadlocks = 0;

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

     // Initialize the depth-first-number

     p->set_depth_first_number(-1);

   }

   DeadlockCycle* deadlocks = NULL;

   DeadlockCycle* last = NULL;

   DeadlockCycle* cycle = new DeadlockCycle();

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

     if (jt->depth_first_number() >= 0) {

       // this thread was already visited

       continue;

     }

     thisDfn = globalDfn;

     jt->set_depth_first_number(globalDfn++);

     previousThread = jt;

     currentThread = jt;

     cycle->reset();

     // When there is a deadlock, all the monitors involved in the dependency

     // cycle must be contended and heavyweight. So we only care about the

     // heavyweight monitor a thread is waiting to lock.

     waitingToLockMonitor = (ObjectMonitor*)jt->current_pending_monitor();

     if (concurrent_locks) {

       waitingToLockBlocker = jt->current_park_blocker();

     }

     while (waitingToLockMonitor != NULL || waitingToLockBlocker != NULL) {

       cycle->add_thread(currentThread);

       if (waitingToLockMonitor != NULL) {

         currentThread = Threads::owning_thread_from_monitor_owner((address)waitingToLockMonitor->owner(),

                                                                   false /* no locking needed */);

       } else {

         if (concurrent_locks) {

           if (waitingToLockBlocker->is_a(SystemDictionary::abstract_ownable_synchronizer_klass())) {

             oop threadObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);

             currentThread = threadObj != NULL ? java_lang_Thread::thread(threadObj) : NULL;

           } else {

             currentThread = NULL;

           }

         }

       }

       if (currentThread == NULL) {

         // No dependency on another thread

         break;

       }

       if (currentThread->depth_first_number() < 0) {

         // First visit to this thread

         currentThread->set_depth_first_number(globalDfn++);

       } else if (currentThread->depth_first_number() < thisDfn) {

         // Thread already visited, and not on a (new) cycle

         break;

       } else if (currentThread == previousThread) {

         // Self-loop, ignore

         break;

       } else {

         // We have a (new) cycle

         num_deadlocks++;

         cycle->set_deadlock(true);

         // add this cycle to the deadlocks list

         if (deadlocks == NULL) {

           deadlocks = cycle;

         } else {

           last->set_next(cycle);

         }

         last = cycle;

         cycle = new DeadlockCycle();

         break;

       }

       previousThread = currentThread;

       waitingToLockMonitor = (ObjectMonitor*)currentThread->current_pending_monitor();

       if (concurrent_locks) {

         waitingToLockBlocker = currentThread->current_park_blocker();

       }

     }

   }

   return deadlocks;

 }

 ThreadDumpResult::ThreadDumpResult() : _num_threads(0), _num_snapshots(0), _snapshots(NULL), _next(NULL), _last(NULL) {

   // Create a new ThreadDumpResult object and append to the list.

   // If GC happens before this function returns, methodOop

   // in the stack trace will be visited.

   ThreadService::add_thread_dump(this);

 }

 ThreadDumpResult::ThreadDumpResult(int num_threads) : _num_threads(num_threads), _num_snapshots(0), _snapshots(NULL), _next(NULL), _last(NULL) {

   // Create a new ThreadDumpResult object and append to the list.

   // If GC happens before this function returns, oops

   // will be visited.

   ThreadService::add_thread_dump(this);

 }

 ThreadDumpResult::~ThreadDumpResult() {

   ThreadService::remove_thread_dump(this);

   // free all the ThreadSnapshot objects created during

   // the VM_ThreadDump operation

   ThreadSnapshot* ts = _snapshots;

   while (ts != NULL) {

     ThreadSnapshot* p = ts;

     ts = ts->next();

     delete p;

   }

 }

 void ThreadDumpResult::add_thread_snapshot(ThreadSnapshot* ts) {

   assert(_num_threads == 0 || _num_snapshots < _num_threads,

          "_num_snapshots must be less than _num_threads");

   _num_snapshots++;

   if (_snapshots == NULL) {

     _snapshots = ts;

   } else {

     _last->set_next(ts);

   }

   _last = ts;

 }

 void ThreadDumpResult::oops_do(OopClosure* f) {

   for (ThreadSnapshot* ts = _snapshots; ts != NULL; ts = ts->next()) {

     ts->oops_do(f);

   }

 }

 StackFrameInfo::StackFrameInfo(javaVFrame* jvf, bool with_lock_info) {

   _method = jvf->method();

   _bci = jvf->bci();

   _locked_monitors = NULL;

   if (with_lock_info) {

     ResourceMark rm;

     GrowableArray<MonitorInfo*>* list = jvf->locked_monitors();

     int length = list->length();

     if (length > 0) {

       _locked_monitors = new (ResourceObj::C_HEAP) GrowableArray<oop>(length, true);

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

         MonitorInfo* monitor = list->at(i);

         assert(monitor->owner(), "This monitor must have an owning object");

         _locked_monitors->append(monitor->owner());

       }

     }

   }

 }

 void StackFrameInfo::oops_do(OopClosure* f) {

   f->do_oop((oop*) &_method);

   if (_locked_monitors != NULL) {

     int length = _locked_monitors->length();

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

       f->do_oop((oop*) _locked_monitors->adr_at(i));

     }

   }

 }

 void StackFrameInfo::print_on(outputStream* st) const {

   ResourceMark rm;

   java_lang_Throwable::print_stack_element(st, method(), bci());

   int len = (_locked_monitors != NULL ? _locked_monitors->length() : 0);

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

     oop o = _locked_monitors->at(i);

     instanceKlass* ik = instanceKlass::cast(o->klass());

     st->print_cr("\t- locked <" INTPTR_FORMAT "> (a %s)", (address)o, ik->external_name());

   }

 }

 // Iterate through monitor cache to find JNI locked monitors

 class InflatedMonitorsClosure: public MonitorClosure {

 private:

   ThreadStackTrace* _stack_trace;

   Thread* _thread;

 public:

   InflatedMonitorsClosure(Thread* t, ThreadStackTrace* st) {

     _thread = t;

     _stack_trace = st;

   }

   void do_monitor(ObjectMonitor* mid) {

     if (mid->owner() == _thread) {

       oop object = (oop) mid->object();

       if (!_stack_trace->is_owned_monitor_on_stack(object)) {

         _stack_trace->add_jni_locked_monitor(object);

       }

     }

   }

 };

 ThreadStackTrace::ThreadStackTrace(JavaThread* t, bool with_locked_monitors) {

   _thread = t;

   _frames = new (ResourceObj::C_HEAP) GrowableArray<StackFrameInfo*>(INITIAL_ARRAY_SIZE, true);

   _depth = 0;

   _with_locked_monitors = with_locked_monitors;

   if (_with_locked_monitors) {

     _jni_locked_monitors = new (ResourceObj::C_HEAP) GrowableArray<oop>(INITIAL_ARRAY_SIZE, true);

   } else {

     _jni_locked_monitors = NULL;

   }

 }

 ThreadStackTrace::~ThreadStackTrace() {

   for (int i = 0; i < _frames->length(); i++) {

     delete _frames->at(i);

   }

   delete _frames;

   if (_jni_locked_monitors != NULL) {

     delete _jni_locked_monitors;

   }

 }

 void ThreadStackTrace::dump_stack_at_safepoint(int maxDepth) {

   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");

   if (_thread->has_last_Java_frame()) {

     RegisterMap reg_map(_thread);

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

     int count = 0;

     for (vframe* f = start_vf; f; f = f->sender() ) {

       if (f->is_java_frame()) {

         javaVFrame* jvf = javaVFrame::cast(f);

         add_stack_frame(jvf);

         count++;

       } else {

         // Ignore non-Java frames

       }

       if (maxDepth > 0 && count == maxDepth) {

         // Skip frames if more than maxDepth

         break;

       }

     }

   }

   if (_with_locked_monitors) {

     // Iterate inflated monitors and find monitors locked by this thread

     // not found in the stack

     InflatedMonitorsClosure imc(_thread, this);

     ObjectSynchronizer::monitors_iterate(&imc);

   }

 }

 bool ThreadStackTrace::is_owned_monitor_on_stack(oop object) {

   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");

   bool found = false;

   int num_frames = get_stack_depth();

   for (int depth = 0; depth < num_frames; depth++) {

     StackFrameInfo* frame = stack_frame_at(depth);

     int len = frame->num_locked_monitors();

     GrowableArray<oop>* locked_monitors = frame->locked_monitors();

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

       oop monitor = locked_monitors->at(j);

       assert(monitor != NULL && monitor->is_instance(), "must be a Java object");

       if (monitor == object) {

         found = true;

         break;

       }

     }

   }

   return found;

 }

 Handle ThreadStackTrace::allocate_fill_stack_trace_element_array(TRAPS) {

   klassOop k = SystemDictionary::StackTraceElement_klass();

   assert(k != NULL, "must be loaded in 1.4+");

   instanceKlassHandle ik(THREAD, k);

   // Allocate an array of java/lang/StackTraceElement object

   objArrayOop ste = oopFactory::new_objArray(ik(), _depth, CHECK_NH);

   objArrayHandle backtrace(THREAD, ste);

   for (int j = 0; j < _depth; j++) {

     StackFrameInfo* frame = _frames->at(j);

     methodHandle mh(THREAD, frame->method());

     oop element = java_lang_StackTraceElement::create(mh, frame->bci(), CHECK_NH);

     backtrace->obj_at_put(j, element);

   }

   return backtrace;

 }

 void ThreadStackTrace::add_stack_frame(javaVFrame* jvf) {

   StackFrameInfo* frame = new StackFrameInfo(jvf, _with_locked_monitors);

   _frames->append(frame);

   _depth++;

 }

 void ThreadStackTrace::oops_do(OopClosure* f) {

   int length = _frames->length();

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

     _frames->at(i)->oops_do(f);

   }

   length = (_jni_locked_monitors != NULL ? _jni_locked_monitors->length() : 0);

   for (int j = 0; j < length; j++) {

     f->do_oop((oop*) _jni_locked_monitors->adr_at(j));

   }

 }

 ConcurrentLocksDump::~ConcurrentLocksDump() {

   if (_retain_map_on_free) {

     return;

   }

   for (ThreadConcurrentLocks* t = _map; t != NULL;)  {

     ThreadConcurrentLocks* tcl = t;

     t = t->next();

     delete tcl;

   }

 }

 void ConcurrentLocksDump::dump_at_safepoint() {

   // dump all locked concurrent locks

   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");

   if (JDK_Version::is_gte_jdk16x_version()) {

     ResourceMark rm;

     GrowableArray<oop>* aos_objects = new GrowableArray<oop>(INITIAL_ARRAY_SIZE);

     // Find all instances of AbstractOwnableSynchronizer

     HeapInspection::find_instances_at_safepoint(SystemDictionary::abstract_ownable_synchronizer_klass(),

                                                 aos_objects);

     // Build a map of thread to its owned AQS locks

     build_map(aos_objects);

   }

 }

 // build a map of JavaThread to all its owned AbstractOwnableSynchronizer

 void ConcurrentLocksDump::build_map(GrowableArray<oop>* aos_objects) {

   int length = aos_objects->length();

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

     oop o = aos_objects->at(i);

     oop owner_thread_obj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(o);

     if (owner_thread_obj != NULL) {

       JavaThread* thread = java_lang_Thread::thread(owner_thread_obj);

       assert(o->is_instance(), "Must be an instanceOop");

       add_lock(thread, (instanceOop) o);

     }

   }

 }

 void ConcurrentLocksDump::add_lock(JavaThread* thread, instanceOop o) {

   ThreadConcurrentLocks* tcl = thread_concurrent_locks(thread);

   if (tcl != NULL) {

     tcl->add_lock(o);

     return;

   }

   // First owned lock found for this thread

   tcl = new ThreadConcurrentLocks(thread);

   tcl->add_lock(o);

   if (_map == NULL) {

     _map = tcl;

   } else {

     _last->set_next(tcl);

   }

   _last = tcl;

 }

 ThreadConcurrentLocks* ConcurrentLocksDump::thread_concurrent_locks(JavaThread* thread) {

   for (ThreadConcurrentLocks* tcl = _map; tcl != NULL; tcl = tcl->next()) {

     if (tcl->java_thread() == thread) {

       return tcl;

     }

   }

   return NULL;

 }

 void ConcurrentLocksDump::print_locks_on(JavaThread* t, outputStream* st) {

   st->print_cr("   Locked ownable synchronizers:");

   ThreadConcurrentLocks* tcl = thread_concurrent_locks(t);

   GrowableArray<instanceOop>* locks = (tcl != NULL ? tcl->owned_locks() : NULL);

   if (locks == NULL || locks->is_empty()) {

     st->print_cr("\t- None");

     st->cr();

     return;

   }

   for (int i = 0; i < locks->length(); i++) {

     instanceOop obj = locks->at(i);

     instanceKlass* ik = instanceKlass::cast(obj->klass());

     st->print_cr("\t- <" INTPTR_FORMAT "> (a %s)", (address)obj, ik->external_name());

   }

   st->cr();

 }

 ThreadConcurrentLocks::ThreadConcurrentLocks(JavaThread* thread) {

   _thread = thread;

   _owned_locks = new (ResourceObj::C_HEAP) GrowableArray<instanceOop>(INITIAL_ARRAY_SIZE, true);

   _next = NULL;

 }

 ThreadConcurrentLocks::~ThreadConcurrentLocks() {

   delete _owned_locks;

 }

 void ThreadConcurrentLocks::add_lock(instanceOop o) {

   _owned_locks->append(o);

 }

 void ThreadConcurrentLocks::oops_do(OopClosure* f) {

   int length = _owned_locks->length();

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

     f->do_oop((oop*) _owned_locks->adr_at(i));

   }

 }

 ThreadStatistics::ThreadStatistics() {

   _contended_enter_count = 0;

   _monitor_wait_count = 0;

   _sleep_count = 0;

   _count_pending_reset = false;

   _timer_pending_reset = false;

   memset((void*) _perf_recursion_counts, 0, sizeof(_perf_recursion_counts));

 }

 ThreadSnapshot::ThreadSnapshot(JavaThread* thread) {

   _thread = thread;

   _threadObj = thread->threadObj();

   _stack_trace = NULL;

   _concurrent_locks = NULL;

   _next = NULL;

   ThreadStatistics* stat = thread->get_thread_stat();

   _contended_enter_ticks = stat->contended_enter_ticks();

   _contended_enter_count = stat->contended_enter_count();

   _monitor_wait_ticks = stat->monitor_wait_ticks();

   _monitor_wait_count = stat->monitor_wait_count();

   _sleep_ticks = stat->sleep_ticks();

   _sleep_count = stat->sleep_count();

   _blocker_object = NULL;

   _blocker_object_owner = NULL;

   _thread_status = java_lang_Thread::get_thread_status(_threadObj);

   _is_ext_suspended = thread->is_being_ext_suspended();

   _is_in_native = (thread->thread_state() == _thread_in_native);

   if (_thread_status == java_lang_Thread::BLOCKED_ON_MONITOR_ENTER ||

       _thread_status == java_lang_Thread::IN_OBJECT_WAIT ||

       _thread_status == java_lang_Thread::IN_OBJECT_WAIT_TIMED) {

     Handle obj = ThreadService::get_current_contended_monitor(thread);

     if (obj() == NULL) {

       // monitor no longer exists; thread is not blocked

       _thread_status = java_lang_Thread::RUNNABLE;

     } else {

       _blocker_object = obj();

       JavaThread* owner = ObjectSynchronizer::get_lock_owner(obj, false);

       if ((owner == NULL && _thread_status == java_lang_Thread::BLOCKED_ON_MONITOR_ENTER)

           || (owner != NULL && owner->is_attaching())) {

         // ownership information of the monitor is not available

         // (may no longer be owned or releasing to some other thread)

         // make this thread in RUNNABLE state.

         // And when the owner thread is in attaching state, the java thread

         // is not completely initialized. For example thread name and id

         // and may not be set, so hide the attaching thread.

         _thread_status = java_lang_Thread::RUNNABLE;

         _blocker_object = NULL;

       } else if (owner != NULL) {

         _blocker_object_owner = owner->threadObj();

       }

     }

   }

   // Support for JSR-166 locks

   if (JDK_Version::current().supports_thread_park_blocker() &&

         (_thread_status == java_lang_Thread::PARKED ||

          _thread_status == java_lang_Thread::PARKED_TIMED)) {

     _blocker_object = thread->current_park_blocker();

     if (_blocker_object != NULL && _blocker_object->is_a(SystemDictionary::abstract_ownable_synchronizer_klass())) {

       _blocker_object_owner = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(_blocker_object);

     }

   }

 }

 ThreadSnapshot::~ThreadSnapshot() {

   delete _stack_trace;

   delete _concurrent_locks;

 }

 void ThreadSnapshot::dump_stack_at_safepoint(int max_depth, bool with_locked_monitors) {

   _stack_trace = new ThreadStackTrace(_thread, with_locked_monitors);

   _stack_trace->dump_stack_at_safepoint(max_depth);

 }

 void ThreadSnapshot::oops_do(OopClosure* f) {

   f->do_oop(&_threadObj);

   f->do_oop(&_blocker_object);

   f->do_oop(&_blocker_object_owner);

   if (_stack_trace != NULL) {

     _stack_trace->oops_do(f);

   }

   if (_concurrent_locks != NULL) {

     _concurrent_locks->oops_do(f);

   }

 }

 DeadlockCycle::DeadlockCycle() {

   _is_deadlock = false;

   _threads = new (ResourceObj::C_HEAP) GrowableArray<JavaThread*>(INITIAL_ARRAY_SIZE, true);

   _next = NULL;

 }

 DeadlockCycle::~DeadlockCycle() {

   delete _threads;

 }

 void DeadlockCycle::print_on(outputStream* st) const {

   st->cr();

   st->print_cr("Found one Java-level deadlock:");

   st->print("=============================");

   JavaThread* currentThread;

   ObjectMonitor* waitingToLockMonitor;

   oop waitingToLockBlocker;

   int len = _threads->length();

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

     currentThread = _threads->at(i);

     waitingToLockMonitor = (ObjectMonitor*)currentThread->current_pending_monitor();

     waitingToLockBlocker = currentThread->current_park_blocker();

     st->cr();

     st->print_cr("\"%s\":", currentThread->get_thread_name());

     const char* owner_desc = ",\n  which is held by";

     if (waitingToLockMonitor != NULL) {

       st->print("  waiting to lock monitor " INTPTR_FORMAT, waitingToLockMonitor);

       oop obj = (oop)waitingToLockMonitor->object();

       if (obj != NULL) {

         st->print(" (object "INTPTR_FORMAT ", a %s)", (address)obj,

                    (instanceKlass::cast(obj->klass()))->external_name());

         if (!currentThread->current_pending_monitor_is_from_java()) {

           owner_desc = "\n  in JNI, which is held by";

         }

       } else {

         // No Java object associated - a JVMTI raw monitor

         owner_desc = " (JVMTI raw monitor),\n  which is held by";

       }

       currentThread = Threads::owning_thread_from_monitor_owner(

         (address)waitingToLockMonitor->owner(), false /* no locking needed */);

     } else {

       st->print("  waiting for ownable synchronizer " INTPTR_FORMAT ", (a %s)",

                 (address)waitingToLockBlocker,

                 (instanceKlass::cast(waitingToLockBlocker->klass()))->external_name());

       assert(waitingToLockBlocker->is_a(SystemDictionary::abstract_ownable_synchronizer_klass()),

              "Must be an AbstractOwnableSynchronizer");

       oop ownerObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);

       currentThread = java_lang_Thread::thread(ownerObj);

     }

     st->print("%s \"%s\"", owner_desc, currentThread->get_thread_name());

   }

   st->cr();

   st->cr();

   // Print stack traces

   bool oldJavaMonitorsInStackTrace = JavaMonitorsInStackTrace;

   JavaMonitorsInStackTrace = true;

   st->print_cr("Java stack information for the threads listed above:");

   st->print_cr("===================================================");

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

     currentThread = _threads->at(j);

     st->print_cr("\"%s\":", currentThread->get_thread_name());

     currentThread->print_stack_on(st);

   }

   JavaMonitorsInStackTrace = oldJavaMonitorsInStackTrace;

 }

 ThreadsListEnumerator::ThreadsListEnumerator(Thread* cur_thread,

                                              bool include_jvmti_agent_threads,

                                              bool include_jni_attaching_threads) {

   assert(cur_thread == Thread::current(), "Check current thread");

   int init_size = ThreadService::get_live_thread_count();

   _threads_array = new GrowableArray<instanceHandle>(init_size);

   MutexLockerEx ml(Threads_lock);

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

     // skips JavaThreads in the process of exiting

     // and also skips VM internal JavaThreads

     // Threads in _thread_new or _thread_new_trans state are included.

     // i.e. threads have been started but not yet running.

     if (jt->threadObj() == NULL   ||

         jt->is_exiting() ||

         !java_lang_Thread::is_alive(jt->threadObj())   ||

         jt->is_hidden_from_external_view()) {

       continue;

     }

     // skip agent threads

     if (!include_jvmti_agent_threads && jt->is_jvmti_agent_thread()) {

       continue;

     }

     // skip jni threads in the process of attaching

     if (!include_jni_attaching_threads && jt->is_attaching()) {

       continue;

     }

     instanceHandle h(cur_thread, (instanceOop) jt->threadObj());

     _threads_array->append(h);

   }

 }