text: /*
   * Copyright (c) 2003, 2021, 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.
   *
   */
  
  #ifndef SHARE_SERVICES_THREADSERVICE_HPP
  #define SHARE_SERVICES_THREADSERVICE_HPP
  
  #include "classfile/classLoader.hpp"
  #include "classfile/javaClasses.hpp"
  #include "classfile/javaThreadStatus.hpp"
  #include "runtime/handles.hpp"
  #include "runtime/init.hpp"
  #include "runtime/objectMonitor.hpp"
  #include "runtime/perfData.hpp"
  #include "runtime/safepoint.hpp"
  #include "runtime/thread.hpp"
  #include "runtime/threadSMR.hpp"
  #include "services/management.hpp"
  
  class OopClosure;
  class ThreadDumpResult;
  class ThreadStackTrace;
  class ThreadSnapshot;
  class StackFrameInfo;
  class ThreadConcurrentLocks;
  class DeadlockCycle;
  
  // VM monitoring and management support for the thread and
  // synchronization subsystem
  //
  // Thread contention monitoring is disabled by default.
  // When enabled, the VM will begin measuring the accumulated
  // elapsed time a thread blocked on synchronization.
  //
  class ThreadService : public AllStatic {
  private:
    // These counters could be moved to Threads class
    static PerfCounter*  _total_threads_count;
    static PerfVariable* _live_threads_count;
    static PerfVariable* _peak_threads_count;
    static PerfVariable* _daemon_threads_count;
  
    // These 2 counters are like the above thread counts, but are
    // atomically decremented in ThreadService::current_thread_exiting instead of
    // ThreadService::remove_thread, so that the thread count is updated before
    // Thread.join() returns.
    static volatile int  _atomic_threads_count;
    static volatile int  _atomic_daemon_threads_count;
  
    static bool          _thread_monitoring_contention_enabled;
    static bool          _thread_cpu_time_enabled;
    static bool          _thread_allocated_memory_enabled;
  
    // Need to keep the list of thread dump result that
    // keep references to Method* since thread dump can be
    // requested by multiple threads concurrently.
    static ThreadDumpResult* _threaddump_list;
  
    static void decrement_thread_counts(JavaThread* jt, bool daemon);
  
  public:
    static void init();
    static void add_thread(JavaThread* thread, bool daemon);
    static void remove_thread(JavaThread* thread, bool daemon);
    static void current_thread_exiting(JavaThread* jt, bool daemon);
  
    static bool set_thread_monitoring_contention(bool flag);
    static bool is_thread_monitoring_contention() { return _thread_monitoring_contention_enabled; }
  
    static bool set_thread_cpu_time_enabled(bool flag);
    static bool is_thread_cpu_time_enabled()    { return _thread_cpu_time_enabled; }
  
    static bool set_thread_allocated_memory_enabled(bool flag);
    static bool is_thread_allocated_memory_enabled() { return _thread_allocated_memory_enabled; }
  
    static jlong get_total_thread_count()       { return _total_threads_count->get_value(); }
    static jlong get_peak_thread_count()        { return _peak_threads_count->get_value(); }
    static jlong get_live_thread_count()        { return _atomic_threads_count; }
    static jlong get_daemon_thread_count()      { return _atomic_daemon_threads_count; }
  
    // Support for thread dump
    static void   add_thread_dump(ThreadDumpResult* dump);
    static void   remove_thread_dump(ThreadDumpResult* dump);
  
    static Handle get_current_contended_monitor(JavaThread* thread);
  
    // This function is called by JVM_DumpThreads.
    static Handle dump_stack_traces(GrowableArray<instanceHandle>* threads,
                                    int num_threads, TRAPS);
  
    static void   reset_peak_thread_count();
    static void   reset_contention_count_stat(JavaThread* thread);
    static void   reset_contention_time_stat(JavaThread* thread);
  
    static DeadlockCycle*       find_deadlocks_at_safepoint(ThreadsList * t_list, bool object_monitors_only);
  
    static void   metadata_do(void f(Metadata*));
  };
  
  // Per-thread Statistics for synchronization
  class ThreadStatistics : public CHeapObj<mtInternal> {
  private:
    // The following contention statistics are only updated by
    // the thread owning these statistics when contention occurs.
  
    jlong        _contended_enter_count;
    elapsedTimer _contended_enter_timer;
    jlong        _monitor_wait_count;
    elapsedTimer _monitor_wait_timer;
    jlong        _sleep_count;
    elapsedTimer _sleep_timer;
  
  
    // These two reset flags are set to true when another thread
    // requests to reset the statistics.  The actual statistics
    // are reset when the thread contention occurs and attempts
    // to update the statistics.
    bool         _count_pending_reset;
    bool         _timer_pending_reset;
  
    // Keep accurate times for potentially recursive class operations
    int           _perf_recursion_counts[PerfClassTraceTime::EVENT_TYPE_COUNT];
    elapsedTimer  _perf_timers[PerfClassTraceTime::EVENT_TYPE_COUNT];
  
    // utility functions
    void  check_and_reset_count()            {
                                               if (!_count_pending_reset) return;
                                               _contended_enter_count = 0;
                                               _monitor_wait_count = 0;
                                               _sleep_count = 0;
                                               _count_pending_reset = 0;
                                             }
    void  check_and_reset_timer()            {
                                               if (!_timer_pending_reset) return;
                                               _contended_enter_timer.reset();
                                               _monitor_wait_timer.reset();
                                               _sleep_timer.reset();
                                               _timer_pending_reset = 0;
                                             }
  
  public:
    ThreadStatistics();
  
    jlong contended_enter_count()            { return (_count_pending_reset ? 0 : _contended_enter_count); }
    jlong contended_enter_ticks()            { return (_timer_pending_reset ? 0 : _contended_enter_timer.active_ticks()); }
    jlong monitor_wait_count()               { return (_count_pending_reset ? 0 : _monitor_wait_count); }
    jlong monitor_wait_ticks()               { return (_timer_pending_reset ? 0 : _monitor_wait_timer.active_ticks()); }
    jlong sleep_count()                      { return (_count_pending_reset ? 0 : _sleep_count); }
    jlong sleep_ticks()                      { return (_timer_pending_reset ? 0 : _sleep_timer.active_ticks()); }
  
    void monitor_wait()                      { check_and_reset_count(); _monitor_wait_count++; }
    void monitor_wait_begin()                { check_and_reset_timer(); _monitor_wait_timer.start(); }
    void monitor_wait_end()                  { _monitor_wait_timer.stop(); check_and_reset_timer(); }
  
    void thread_sleep()                      { check_and_reset_count(); _sleep_count++; }
    void thread_sleep_begin()                { check_and_reset_timer(); _sleep_timer.start(); }
    void thread_sleep_end()                  { _sleep_timer.stop(); check_and_reset_timer(); }
  
    void contended_enter()                   { check_and_reset_count(); _contended_enter_count++; }
    void contended_enter_begin()             { check_and_reset_timer(); _contended_enter_timer.start(); }
    void contended_enter_end()               { _contended_enter_timer.stop(); check_and_reset_timer(); }
  
    void reset_count_stat()                  { _count_pending_reset = true; }
    void reset_time_stat()                   { _timer_pending_reset = true; }
  
    int* perf_recursion_counts_addr()        { return _perf_recursion_counts; }
    elapsedTimer* perf_timers_addr()         { return _perf_timers; }
  };
  
  // Thread snapshot to represent the thread state and statistics
  class ThreadSnapshot : public CHeapObj<mtInternal> {
  private:
    // This JavaThread* is protected by being stored in objects that are
    // protected by a ThreadsListSetter (ThreadDumpResult).
    JavaThread* _thread;
    OopHandle   _threadObj;
    JavaThreadStatus _thread_status;
  
    bool    _is_suspended;
    bool    _is_in_native;
  
    jlong   _contended_enter_ticks;
    jlong   _contended_enter_count;
    jlong   _monitor_wait_ticks;
    jlong   _monitor_wait_count;
    jlong   _sleep_ticks;
    jlong   _sleep_count;
  
    OopHandle     _blocker_object;
    OopHandle     _blocker_object_owner;
  
    ThreadStackTrace*      _stack_trace;
    ThreadConcurrentLocks* _concurrent_locks;
    ThreadSnapshot*        _next;
  
    // ThreadSnapshot instances should only be created via
    // ThreadDumpResult::add_thread_snapshot.
    friend class ThreadDumpResult;
    ThreadSnapshot() : _thread(NULL),
                       _stack_trace(NULL), _concurrent_locks(NULL), _next(NULL) {};
    void        initialize(ThreadsList * t_list, JavaThread* thread);
  
  public:
    ~ThreadSnapshot();
  
    JavaThreadStatus thread_status() { return _thread_status; }
  
    oop         threadObj() const;
  
    void        set_next(ThreadSnapshot* n) { _next = n; }
  
    bool        is_suspended()              { return _is_suspended; }
    bool        is_in_native()              { return _is_in_native; }
  
    jlong       contended_enter_count()     { return _contended_enter_count; }
    jlong       contended_enter_ticks()     { return _contended_enter_ticks; }
    jlong       monitor_wait_count()        { return _monitor_wait_count; }
    jlong       monitor_wait_ticks()        { return _monitor_wait_ticks; }
    jlong       sleep_count()               { return _sleep_count; }
    jlong       sleep_ticks()               { return _sleep_ticks; }
  
  
    oop         blocker_object() const;
    oop         blocker_object_owner() const;
  
    ThreadSnapshot*   next() const          { return _next; }
    ThreadStackTrace* get_stack_trace()     { return _stack_trace; }
    ThreadConcurrentLocks* get_concurrent_locks()     { return _concurrent_locks; }
  
    void        dump_stack_at_safepoint(int max_depth, bool with_locked_monitors);
    void        set_concurrent_locks(ThreadConcurrentLocks* l) { _concurrent_locks = l; }
    void        metadata_do(void f(Metadata*));
  };
  
  class ThreadStackTrace : public CHeapObj<mtInternal> {
   private:
    JavaThread*                     _thread;
    int                             _depth;  // number of stack frames added
    bool                            _with_locked_monitors;
    GrowableArray<StackFrameInfo*>* _frames;
    GrowableArray<OopHandle>*       _jni_locked_monitors;
  
   public:
  
    ThreadStackTrace(JavaThread* thread, bool with_locked_monitors);
    ~ThreadStackTrace();
  
    JavaThread*     thread()              { return _thread; }
    StackFrameInfo* stack_frame_at(int i) { return _frames->at(i); }
    int             get_stack_depth()     { return _depth; }
  
    void            add_stack_frame(javaVFrame* jvf);
    void            dump_stack_at_safepoint(int max_depth);
    Handle          allocate_fill_stack_trace_element_array(TRAPS);
    void            metadata_do(void f(Metadata*));
    GrowableArray<OopHandle>* jni_locked_monitors() { return _jni_locked_monitors; }
    int             num_jni_locked_monitors() { return (_jni_locked_monitors != NULL ? _jni_locked_monitors->length() : 0); }
  
    bool            is_owned_monitor_on_stack(oop object);
    void            add_jni_locked_monitor(oop object);
  };
  
  // StackFrameInfo for keeping Method* and bci during
  // stack walking for later construction of StackTraceElement[]
  // Java instances
  class StackFrameInfo : public CHeapObj<mtInternal> {
   private:
    Method*             _method;
    int                 _bci;
    GrowableArray<OopHandle>* _locked_monitors; // list of object monitors locked by this frame
    // We need to save the mirrors in the backtrace to keep the class
    // from being unloaded while we still have this stack trace.
    OopHandle           _class_holder;
  
   public:
  
    StackFrameInfo(javaVFrame* jvf, bool with_locked_monitors);
    ~StackFrameInfo();
    Method*   method() const       { return _method; }
    int       bci()    const       { return _bci; }
    void      metadata_do(void f(Metadata*));
  
    int       num_locked_monitors()       { return (_locked_monitors != NULL ? _locked_monitors->length() : 0); }
    GrowableArray<OopHandle>* locked_monitors() { return _locked_monitors; }
  
    void      print_on(outputStream* st) const;
  };
  
  class ThreadConcurrentLocks : public CHeapObj<mtInternal> {
  private:
    GrowableArray<OopHandle>*   _owned_locks;
    ThreadConcurrentLocks*      _next;
    // This JavaThread* is protected in one of two different ways
    // depending on the usage of the ThreadConcurrentLocks object:
    // 1) by being stored in objects that are only allocated and used at a
    // safepoint (ConcurrentLocksDump), or 2) by being stored in objects
    // that are protected by a ThreadsListSetter (ThreadSnapshot inside
    // ThreadDumpResult).
    JavaThread*                 _thread;
   public:
    ThreadConcurrentLocks(JavaThread* thread);
    ~ThreadConcurrentLocks();
  
    void                        add_lock(instanceOop o);
    void                        set_next(ThreadConcurrentLocks* n) { _next = n; }
    ThreadConcurrentLocks*      next() { return _next; }
    JavaThread*                 java_thread()                      { return _thread; }
    GrowableArray<OopHandle>*   owned_locks()                      { return _owned_locks; }
  };
  
  class ConcurrentLocksDump : public StackObj {
   private:
    ThreadConcurrentLocks* _map;
    ThreadConcurrentLocks* _last;   // Last ThreadConcurrentLocks in the map
    bool                   _retain_map_on_free;
  
    void build_map(GrowableArray<oop>* aos_objects);
    void add_lock(JavaThread* thread, instanceOop o);
  
   public:
    ConcurrentLocksDump(bool retain_map_on_free) : _map(NULL), _last(NULL), _retain_map_on_free(retain_map_on_free) {
      assert(SafepointSynchronize::is_at_safepoint(), "Must be constructed at a safepoint.");
    };
    ConcurrentLocksDump() : _map(NULL), _last(NULL), _retain_map_on_free(false) {
      assert(SafepointSynchronize::is_at_safepoint(), "Must be constructed at a safepoint.");
    };
    ~ConcurrentLocksDump();
  
    void                        dump_at_safepoint();
    ThreadConcurrentLocks*      thread_concurrent_locks(JavaThread* thread);
    void                        print_locks_on(JavaThread* t, outputStream* st);
  };
  
  class ThreadDumpResult : public StackObj {
   private:
    int                  _num_threads;
    int                  _num_snapshots;
    ThreadSnapshot*      _snapshots;
    ThreadSnapshot*      _last;
    ThreadDumpResult*    _next;
    ThreadsListSetter    _setter;  // Helper to set hazard ptr in the originating thread
                                   // which protects the JavaThreads in _snapshots.
  
    void                 link_thread_snapshot(ThreadSnapshot* ts);
  
   public:
    ThreadDumpResult();
    ThreadDumpResult(int num_threads);
    ~ThreadDumpResult();
  
    ThreadSnapshot*      add_thread_snapshot();
    ThreadSnapshot*      add_thread_snapshot(JavaThread* thread);
  
    void                 set_next(ThreadDumpResult* next) { _next = next; }
    ThreadDumpResult*    next()                           { return _next; }
    int                  num_threads()                    { return _num_threads; }
    int                  num_snapshots()                  { return _num_snapshots; }
    ThreadSnapshot*      snapshots()                      { return _snapshots; }
    void                 set_t_list()                     { _setter.set(); }
    ThreadsList*         t_list();
    bool                 t_list_has_been_set()            { return _setter.is_set(); }
    void                 metadata_do(void f(Metadata*));
  };
  
  class DeadlockCycle : public CHeapObj<mtInternal> {
   private:
    bool _is_deadlock;
    GrowableArray<JavaThread*>* _threads;
    DeadlockCycle*              _next;
   public:
    DeadlockCycle();
    ~DeadlockCycle();
  
    DeadlockCycle* next()                     { return _next; }
    void           set_next(DeadlockCycle* d) { _next = d; }
    void           add_thread(JavaThread* t)  { _threads->append(t); }
    void           reset()                    { _is_deadlock = false; _threads->clear(); }
    void           set_deadlock(bool value)   { _is_deadlock = value; }
    bool           is_deadlock()              { return _is_deadlock; }
    int            num_threads()              { return _threads->length(); }
    GrowableArray<JavaThread*>* threads()     { return _threads; }
    void           print_on_with(ThreadsList * t_list, outputStream* st) const;
  };
  
  // Utility class to get list of java threads.
  class ThreadsListEnumerator : public StackObj {
  private:
    GrowableArray<instanceHandle>* _threads_array;
  public:
    ThreadsListEnumerator(Thread* cur_thread,
                          bool include_jvmti_agent_threads = false,
                          bool include_jni_attaching_threads = true);
    int            num_threads()            { return _threads_array->length(); }
    instanceHandle get_threadObj(int index) { return _threads_array->at(index); }
  };
  
  
  // abstract utility class to set new thread states, and restore previous after the block exits
  class JavaThreadStatusChanger : public StackObj {
   private:
    JavaThreadStatus _old_state;
    JavaThread*  _java_thread;
    bool _is_alive;
  
    void save_old_state(JavaThread* java_thread) {
      _java_thread  = java_thread;
      _is_alive = is_alive(java_thread);
      if (is_alive()) {
        _old_state = java_lang_Thread::get_thread_status(_java_thread->threadObj());
      }
    }
  
   public:
    static void set_thread_status(JavaThread* java_thread,
                                  JavaThreadStatus state) {
      java_lang_Thread::set_thread_status(java_thread->threadObj(), state);
    }
  
    void set_thread_status(JavaThreadStatus state) {
      if (is_alive()) {
        set_thread_status(_java_thread, state);
      }
    }
  
    JavaThreadStatusChanger(JavaThread* java_thread,
                            JavaThreadStatus state) : _old_state(JavaThreadStatus::NEW) {
      save_old_state(java_thread);
      set_thread_status(state);
    }
  
    JavaThreadStatusChanger(JavaThread* java_thread) : _old_state(JavaThreadStatus::NEW) {
      save_old_state(java_thread);
    }
  
    ~JavaThreadStatusChanger() {
      set_thread_status(_old_state);
    }
  
    static bool is_alive(JavaThread* java_thread) {
      return java_thread != NULL && java_thread->threadObj() != NULL;
    }
  
    bool is_alive() {
      return _is_alive;
    }
  };
  
  // Change status to waiting on an object  (timed or indefinite)
  class JavaThreadInObjectWaitState : public JavaThreadStatusChanger {
   private:
    ThreadStatistics* _stat;
    bool _active;
  
   public:
    JavaThreadInObjectWaitState(JavaThread *java_thread, bool timed) :
      JavaThreadStatusChanger(java_thread,
                              timed ? JavaThreadStatus::IN_OBJECT_WAIT_TIMED : JavaThreadStatus::IN_OBJECT_WAIT) {
      if (is_alive()) {
        _stat = java_thread->get_thread_stat();
        _active = ThreadService::is_thread_monitoring_contention();
        _stat->monitor_wait();
        if (_active) {
          _stat->monitor_wait_begin();
        }
      } else {
        _active = false;
      }
    }
  
    ~JavaThreadInObjectWaitState() {
      if (_active) {
        _stat->monitor_wait_end();
      }
    }
  };
  
  // Change status to parked (timed or indefinite)
  class JavaThreadParkedState : public JavaThreadStatusChanger {
   private:
    ThreadStatistics* _stat;
    bool _active;
  
   public:
    JavaThreadParkedState(JavaThread *java_thread, bool timed) :
      JavaThreadStatusChanger(java_thread,
                              timed ? JavaThreadStatus::PARKED_TIMED : JavaThreadStatus::PARKED) {
      if (is_alive()) {
        _stat = java_thread->get_thread_stat();
        _active = ThreadService::is_thread_monitoring_contention();
        _stat->monitor_wait();
        if (_active) {
          _stat->monitor_wait_begin();
        }
      } else {
        _active = false;
      }
    }
  
    ~JavaThreadParkedState() {
      if (_active) {
        _stat->monitor_wait_end();
      }
    }
  };
  
  // Change status to blocked on (re-)entering a synchronization block
  class JavaThreadBlockedOnMonitorEnterState : public JavaThreadStatusChanger {
   private:
    ThreadStatistics* _stat;
    bool _active;
  
    static bool contended_enter_begin(JavaThread *java_thread) {
      set_thread_status(java_thread, JavaThreadStatus::BLOCKED_ON_MONITOR_ENTER);
      ThreadStatistics* stat = java_thread->get_thread_stat();
      stat->contended_enter();
      bool active = ThreadService::is_thread_monitoring_contention();
      if (active) {
        stat->contended_enter_begin();
      }
      return active;
    }
  
   public:
    // java_thread is waiting thread being blocked on monitor reenter.
    // Current thread is the notifying thread which holds the monitor.
    static bool wait_reenter_begin(JavaThread *java_thread, ObjectMonitor *obj_m) {
      assert((java_thread != NULL), "Java thread should not be null here");
      bool active = false;
      if (is_alive(java_thread)) {
        active = contended_enter_begin(java_thread);
      }
      return active;
    }
  
    static void wait_reenter_end(JavaThread *java_thread, bool active) {
      if (active) {
        java_thread->get_thread_stat()->contended_enter_end();
      }
      set_thread_status(java_thread, JavaThreadStatus::RUNNABLE);
    }
  
    JavaThreadBlockedOnMonitorEnterState(JavaThread *java_thread, ObjectMonitor *obj_m) :
      JavaThreadStatusChanger(java_thread), _stat(NULL), _active(false) {
      assert((java_thread != NULL), "Java thread should not be null here");
      // Change thread status and collect contended enter stats for monitor contended
      // enter done for external java world objects and it is contended. All other cases
      // like for vm internal objects and for external objects which are not contended
      // thread status is not changed and contended enter stat is not collected.
      _active = false;
      if (is_alive() && obj_m->contentions() > 0) {
        _stat = java_thread->get_thread_stat();
        _active = contended_enter_begin(java_thread);
      }
    }
  
    ~JavaThreadBlockedOnMonitorEnterState() {
      if (_active) {
        _stat->contended_enter_end();
      }
    }
  };
  
  // Change status to sleeping
  class JavaThreadSleepState : public JavaThreadStatusChanger {
   private:
    ThreadStatistics* _stat;
    bool _active;
   public:
    JavaThreadSleepState(JavaThread *java_thread) :
      JavaThreadStatusChanger(java_thread, JavaThreadStatus::SLEEPING) {
      if (is_alive()) {
        _stat = java_thread->get_thread_stat();
        _active = ThreadService::is_thread_monitoring_contention();
        _stat->thread_sleep();
        if (_active) {
          _stat->thread_sleep_begin();
        }
      } else {
        _active = false;
      }
    }
  
    ~JavaThreadSleepState() {
      if (_active) {
        _stat->thread_sleep_end();
      }
    }
  };
  
  #endif // SHARE_SERVICES_THREADSERVICE_HPP
  