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 /*

  * Copyright (c) 1997, 2012, 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_VM_RUNTIME_THREAD_HPP

 #define SHARE_VM_RUNTIME_THREAD_HPP

 #include "memory/allocation.hpp"

 #include "memory/threadLocalAllocBuffer.hpp"

 #include "oops/oop.hpp"

 #include "prims/jni.h"

 #include "prims/jvmtiExport.hpp"

 #include "runtime/frame.hpp"

 #include "runtime/javaFrameAnchor.hpp"

 #include "runtime/jniHandles.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "runtime/os.hpp"

 #include "runtime/osThread.hpp"

 #include "runtime/park.hpp"

 #include "runtime/safepoint.hpp"

 #include "runtime/stubRoutines.hpp"

 #include "runtime/threadLocalStorage.hpp"

 #include "runtime/unhandledOops.hpp"

 #include "services/memRecorder.hpp"

 #include "trace/tracing.hpp"

 #include "utilities/exceptions.hpp"

 #include "utilities/top.hpp"

 #ifndef SERIALGC

 #include "gc_implementation/g1/dirtyCardQueue.hpp"

 #include "gc_implementation/g1/satbQueue.hpp"

 #endif

 #ifdef ZERO

 #ifdef TARGET_ARCH_zero

 # include "stack_zero.hpp"

 #endif

 #endif

 class ThreadSafepointState;

 class ThreadProfiler;

 class JvmtiThreadState;

 class JvmtiGetLoadedClassesClosure;

 class ThreadStatistics;

 class ConcurrentLocksDump;

 class ParkEvent;

 class Parker;

 class ciEnv;

 class CompileThread;

 class CompileLog;

 class CompileTask;

 class CompileQueue;

 class CompilerCounters;

 class vframeArray;

 class DeoptResourceMark;

 class jvmtiDeferredLocalVariableSet;

 class GCTaskQueue;

 class ThreadClosure;

 class IdealGraphPrinter;

 class WorkerThread;

 // Class hierarchy

 // - Thread

 //   - NamedThread

 //     - VMThread

 //     - ConcurrentGCThread

 //     - WorkerThread

 //       - GangWorker

 //       - GCTaskThread

 //   - JavaThread

 //   - WatcherThread

 class Thread: public ThreadShadow {

   friend class VMStructs;

  private:

   // Exception handling

   // (Note: _pending_exception and friends are in ThreadShadow)

   //oop       _pending_exception;                // pending exception for current thread

   // const char* _exception_file;                   // file information for exception (debugging only)

   // int         _exception_line;                   // line information for exception (debugging only)

  protected:

   // Support for forcing alignment of thread objects for biased locking

   void*       _real_malloc_address;

  public:

   void* operator new(size_t size) { return allocate(size, true); }

   void* operator new(size_t size, std::nothrow_t& nothrow_constant) { return allocate(size, false); }

   void  operator delete(void* p);

  protected:

    static void* allocate(size_t size, bool throw_excpt, MEMFLAGS flags = mtThread);

  private:

   // ***************************************************************

   // Suspend and resume support

   // ***************************************************************

   //

   // VM suspend/resume no longer exists - it was once used for various

   // things including safepoints but was deprecated and finally removed

   // in Java 7. Because VM suspension was considered "internal" Java-level

   // suspension was considered "external", and this legacy naming scheme

   // remains.

   //

   // External suspend/resume requests come from JVM_SuspendThread,

   // JVM_ResumeThread, JVMTI SuspendThread, and finally JVMTI

   // ResumeThread. External

   // suspend requests cause _external_suspend to be set and external

   // resume requests cause _external_suspend to be cleared.

   // External suspend requests do not nest on top of other external

   // suspend requests. The higher level APIs reject suspend requests

   // for already suspended threads.

   //

   // The external_suspend

   // flag is checked by has_special_runtime_exit_condition() and java thread

   // will self-suspend when handle_special_runtime_exit_condition() is

   // called. Most uses of the _thread_blocked state in JavaThreads are

   // considered the same as being externally suspended; if the blocking

   // condition lifts, the JavaThread will self-suspend. Other places

   // where VM checks for external_suspend include:

   //   + mutex granting (do not enter monitors when thread is suspended)

   //   + state transitions from _thread_in_native

   //

   // In general, java_suspend() does not wait for an external suspend

   // request to complete. When it returns, the only guarantee is that

   // the _external_suspend field is true.

   //

   // wait_for_ext_suspend_completion() is used to wait for an external

   // suspend request to complete. External suspend requests are usually

   // followed by some other interface call that requires the thread to

   // be quiescent, e.g., GetCallTrace(). By moving the "wait time" into

   // the interface that requires quiescence, we give the JavaThread a

   // chance to self-suspend before we need it to be quiescent. This

   // improves overall suspend/query performance.

   //

   // _suspend_flags controls the behavior of java_ suspend/resume.

   // It must be set under the protection of SR_lock. Read from the flag is

   // OK without SR_lock as long as the value is only used as a hint.

   // (e.g., check _external_suspend first without lock and then recheck

   // inside SR_lock and finish the suspension)

   //

   // _suspend_flags is also overloaded for other "special conditions" so

   // that a single check indicates whether any special action is needed

   // eg. for async exceptions.

   // -------------------------------------------------------------------

   // Notes:

   // 1. The suspend/resume logic no longer uses ThreadState in OSThread

   // but we still update its value to keep other part of the system (mainly

   // JVMTI) happy. ThreadState is legacy code (see notes in

   // osThread.hpp).

   //

   // 2. It would be more natural if set_external_suspend() is private and

   // part of java_suspend(), but that probably would affect the suspend/query

   // performance. Need more investigation on this.

   //

   // suspend/resume lock: used for self-suspend

   Monitor* _SR_lock;

  protected:

   enum SuspendFlags {

     // NOTE: avoid using the sign-bit as cc generates different test code

     //       when the sign-bit is used, and sometimes incorrectly - see CR 6398077

     _external_suspend       = 0x20000000U, // thread is asked to self suspend

     _ext_suspended          = 0x40000000U, // thread has self-suspended

     _deopt_suspend          = 0x10000000U, // thread needs to self suspend for deopt

     _has_async_exception    = 0x00000001U, // there is a pending async exception

     _critical_native_unlock = 0x00000002U  // Must call back to unlock JNI critical lock

   };

   // various suspension related flags - atomically updated

   // overloaded for async exception checking in check_special_condition_for_native_trans.

   volatile uint32_t _suspend_flags;

  private:

   int _num_nested_signal;

  public:

   void enter_signal_handler() { _num_nested_signal++; }

   void leave_signal_handler() { _num_nested_signal--; }

   bool is_inside_signal_handler() const { return _num_nested_signal > 0; }

  private:

   // Debug tracing

   static void trace(const char* msg, const Thread* const thread) PRODUCT_RETURN;

   // Active_handles points to a block of handles

   JNIHandleBlock* _active_handles;

   // One-element thread local free list

   JNIHandleBlock* _free_handle_block;

   // Point to the last handle mark

   HandleMark* _last_handle_mark;

   // The parity of the last strong_roots iteration in which this thread was

   // claimed as a task.

   jint _oops_do_parity;

   public:

    void set_last_handle_mark(HandleMark* mark)   { _last_handle_mark = mark; }

    HandleMark* last_handle_mark() const          { return _last_handle_mark; }

   private:

   // debug support for checking if code does allow safepoints or not

   // GC points in the VM can happen because of allocation, invoking a VM operation, or blocking on

   // mutex, or blocking on an object synchronizer (Java locking).

   // If !allow_safepoint(), then an assertion failure will happen in any of the above cases

   // If !allow_allocation(), then an assertion failure will happen during allocation

   // (Hence, !allow_safepoint() => !allow_allocation()).

   //

   // The two classes No_Safepoint_Verifier and No_Allocation_Verifier are used to set these counters.

   //

   NOT_PRODUCT(int _allow_safepoint_count;)      // If 0, thread allow a safepoint to happen

   debug_only (int _allow_allocation_count;)     // If 0, the thread is allowed to allocate oops.

   // Used by SkipGCALot class.

   NOT_PRODUCT(bool _skip_gcalot;)               // Should we elide gc-a-lot?

   // Record when GC is locked out via the GC_locker mechanism

   CHECK_UNHANDLED_OOPS_ONLY(int _gc_locked_out_count;)

   friend class No_Alloc_Verifier;

   friend class No_Safepoint_Verifier;

   friend class Pause_No_Safepoint_Verifier;

   friend class ThreadLocalStorage;

   friend class GC_locker;

   ThreadLocalAllocBuffer _tlab;                 // Thread-local eden

   jlong _allocated_bytes;                       // Cumulative number of bytes allocated on

                                                 // the Java heap

   TRACE_BUFFER _trace_buffer;                   // Thread-local buffer for tracing

   int   _vm_operation_started_count;            // VM_Operation support

   int   _vm_operation_completed_count;          // VM_Operation support

   ObjectMonitor* _current_pending_monitor;      // ObjectMonitor this thread

                                                 // is waiting to lock

   bool _current_pending_monitor_is_from_java;   // locking is from Java code

   // ObjectMonitor on which this thread called Object.wait()

   ObjectMonitor* _current_waiting_monitor;

   // Private thread-local objectmonitor list - a simple cache organized as a SLL.

  public:

   ObjectMonitor* omFreeList;

   int omFreeCount;                              // length of omFreeList

   int omFreeProvision;                          // reload chunk size

   ObjectMonitor* omInUseList;                   // SLL to track monitors in circulation

   int omInUseCount;                             // length of omInUseList

 #ifdef ASSERT

  private:

   bool _visited_for_critical_count;

  public:

   void set_visited_for_critical_count(bool z) { _visited_for_critical_count = z; }

   bool was_visited_for_critical_count() const   { return _visited_for_critical_count; }

 #endif

  public:

   enum {

     is_definitely_current_thread = true

   };

   // Constructor

   Thread();

   virtual ~Thread();

   // initializtion

   void initialize_thread_local_storage();

   // thread entry point

   virtual void run();

   // Testers

   virtual bool is_VM_thread()       const            { return false; }

   virtual bool is_Java_thread()     const            { return false; }

   virtual bool is_Compiler_thread() const            { return false; }

   virtual bool is_hidden_from_external_view() const  { return false; }

   virtual bool is_jvmti_agent_thread() const         { return false; }

   // True iff the thread can perform GC operations at a safepoint.

   // Generally will be true only of VM thread and parallel GC WorkGang

   // threads.

   virtual bool is_GC_task_thread() const             { return false; }

   virtual bool is_Watcher_thread() const             { return false; }

   virtual bool is_ConcurrentGC_thread() const        { return false; }

   virtual bool is_Named_thread() const               { return false; }

   virtual bool is_Worker_thread() const              { return false; }

   // Casts

   virtual WorkerThread* as_Worker_thread() const     { return NULL; }

   virtual char* name() const { return (char*)"Unknown thread"; }

   // Returns the current thread

   static inline Thread* current();

   // Common thread operations

   static void set_priority(Thread* thread, ThreadPriority priority);

   static ThreadPriority get_priority(const Thread* const thread);

   static void start(Thread* thread);

   static void interrupt(Thread* thr);

   static bool is_interrupted(Thread* thr, bool clear_interrupted);

   void set_native_thread_name(const char *name) {

     assert(Thread::current() == this, "set_native_thread_name can only be called on the current thread");

     os::set_native_thread_name(name);

   }

   ObjectMonitor** omInUseList_addr()             { return (ObjectMonitor **)&omInUseList; }

   Monitor* SR_lock() const                       { return _SR_lock; }

   bool has_async_exception() const { return (_suspend_flags & _has_async_exception) != 0; }

   void set_suspend_flag(SuspendFlags f) {

     assert(sizeof(jint) == sizeof(_suspend_flags), "size mismatch");

     uint32_t flags;

     do {

       flags = _suspend_flags;

     }

     while (Atomic::cmpxchg((jint)(flags | f),

                            (volatile jint*)&_suspend_flags,

                            (jint)flags) != (jint)flags);

   }

   void clear_suspend_flag(SuspendFlags f) {

     assert(sizeof(jint) == sizeof(_suspend_flags), "size mismatch");

     uint32_t flags;

     do {

       flags = _suspend_flags;

     }

     while (Atomic::cmpxchg((jint)(flags & ~f),

                            (volatile jint*)&_suspend_flags,

                            (jint)flags) != (jint)flags);

   }

   void set_has_async_exception() {

     set_suspend_flag(_has_async_exception);

   }

   void clear_has_async_exception() {

     clear_suspend_flag(_has_async_exception);

   }

   bool do_critical_native_unlock() const { return (_suspend_flags & _critical_native_unlock) != 0; }

   void set_critical_native_unlock() {

     set_suspend_flag(_critical_native_unlock);

   }

   void clear_critical_native_unlock() {

     clear_suspend_flag(_critical_native_unlock);

   }

   // Support for Unhandled Oop detection

 #ifdef CHECK_UNHANDLED_OOPS

  private:

   UnhandledOops* _unhandled_oops;

  public:

   UnhandledOops* unhandled_oops() { return _unhandled_oops; }

   // Mark oop safe for gc.  It may be stack allocated but won't move.

   void allow_unhandled_oop(oop *op) {

     if (CheckUnhandledOops) unhandled_oops()->allow_unhandled_oop(op);

   }

   // Clear oops at safepoint so crashes point to unhandled oop violator

   void clear_unhandled_oops() {

     if (CheckUnhandledOops) unhandled_oops()->clear_unhandled_oops();

   }

   bool is_gc_locked_out() { return _gc_locked_out_count > 0; }

 #endif // CHECK_UNHANDLED_OOPS

 #ifndef PRODUCT

   bool skip_gcalot()           { return _skip_gcalot; }

   void set_skip_gcalot(bool v) { _skip_gcalot = v;    }

 #endif

  public:

   // Installs a pending exception to be inserted later

   static void send_async_exception(oop thread_oop, oop java_throwable);

   // Resource area

   ResourceArea* resource_area() const            { return _resource_area; }

   void set_resource_area(ResourceArea* area)     { _resource_area = area; }

   OSThread* osthread() const                     { return _osthread;   }

   void set_osthread(OSThread* thread)            { _osthread = thread; }

   // JNI handle support

   JNIHandleBlock* active_handles() const         { return _active_handles; }

   void set_active_handles(JNIHandleBlock* block) { _active_handles = block; }

   JNIHandleBlock* free_handle_block() const      { return _free_handle_block; }

   void set_free_handle_block(JNIHandleBlock* block) { _free_handle_block = block; }

   // Internal handle support

   HandleArea* handle_area() const                { return _handle_area; }

   void set_handle_area(HandleArea* area)         { _handle_area = area; }

   // Thread-Local Allocation Buffer (TLAB) support

   ThreadLocalAllocBuffer& tlab()                 { return _tlab; }

   void initialize_tlab() {

     if (UseTLAB) {

       tlab().initialize();

     }

   }

   jlong allocated_bytes()               { return _allocated_bytes; }

   void set_allocated_bytes(jlong value) { _allocated_bytes = value; }

   void incr_allocated_bytes(jlong size) { _allocated_bytes += size; }

   jlong cooked_allocated_bytes() {

     jlong allocated_bytes = OrderAccess::load_acquire(&_allocated_bytes);

     if (UseTLAB) {

       size_t used_bytes = tlab().used_bytes();

       if ((ssize_t)used_bytes > 0) {

         // More-or-less valid tlab.  The load_acquire above should ensure

         // that the result of the add is <= the instantaneous value

         return allocated_bytes + used_bytes;

       }

     }

     return allocated_bytes;

   }

   TRACE_BUFFER trace_buffer()              { return _trace_buffer; }

   void set_trace_buffer(TRACE_BUFFER buf)  { _trace_buffer = buf; }

   // VM operation support

   int vm_operation_ticket()                      { return ++_vm_operation_started_count; }

   int vm_operation_completed_count()             { return _vm_operation_completed_count; }

   void increment_vm_operation_completed_count()  { _vm_operation_completed_count++; }

   // For tracking the heavyweight monitor the thread is pending on.

   ObjectMonitor* current_pending_monitor() {

     return _current_pending_monitor;

   }

   void set_current_pending_monitor(ObjectMonitor* monitor) {

     _current_pending_monitor = monitor;

   }

   void set_current_pending_monitor_is_from_java(bool from_java) {

     _current_pending_monitor_is_from_java = from_java;

   }

   bool current_pending_monitor_is_from_java() {

     return _current_pending_monitor_is_from_java;

   }

   // For tracking the ObjectMonitor on which this thread called Object.wait()

   ObjectMonitor* current_waiting_monitor() {

     return _current_waiting_monitor;

   }

   void set_current_waiting_monitor(ObjectMonitor* monitor) {

     _current_waiting_monitor = monitor;

   }

   // GC support

   // Apply "f->do_oop" to all root oops in "this".

   // Apply "cf->do_code_blob" (if !NULL) to all code blobs active in frames

   virtual void oops_do(OopClosure* f, CodeBlobClosure* cf);

   // Handles the parallel case for the method below.

 private:

   bool claim_oops_do_par_case(int collection_parity);

 public:

   // Requires that "collection_parity" is that of the current strong roots

   // iteration.  If "is_par" is false, sets the parity of "this" to

   // "collection_parity", and returns "true".  If "is_par" is true,

   // uses an atomic instruction to set the current threads parity to

   // "collection_parity", if it is not already.  Returns "true" iff the

   // calling thread does the update, this indicates that the calling thread

   // has claimed the thread's stack as a root groop in the current

   // collection.

   bool claim_oops_do(bool is_par, int collection_parity) {

     if (!is_par) {

       _oops_do_parity = collection_parity;

       return true;

     } else {

       return claim_oops_do_par_case(collection_parity);

     }

   }

   // Sweeper support

   void nmethods_do(CodeBlobClosure* cf);

   // Used by fast lock support

   virtual bool is_lock_owned(address adr) const;

   // Check if address is in the stack of the thread (not just for locks).

   // Warning: the method can only be used on the running thread

   bool is_in_stack(address adr) const;

   // Sets this thread as starting thread. Returns failure if thread

   // creation fails due to lack of memory, too many threads etc.

   bool set_as_starting_thread();

  protected:

   // OS data associated with the thread

   OSThread* _osthread;  // Platform-specific thread information

   // Thread local resource area for temporary allocation within the VM

   ResourceArea* _resource_area;

   // Thread local handle area for allocation of handles within the VM

   HandleArea* _handle_area;

   // Support for stack overflow handling, get_thread, etc.

   address          _stack_base;

   size_t           _stack_size;

   uintptr_t        _self_raw_id;      // used by get_thread (mutable)

   int              _lgrp_id;

  public:

   // Stack overflow support

   address stack_base() const           { assert(_stack_base != NULL,"Sanity check"); return _stack_base; }

   void    set_stack_base(address base) { _stack_base = base; }

   size_t  stack_size() const           { return _stack_size; }

   void    set_stack_size(size_t size)  { _stack_size = size; }

   void    record_stack_base_and_size();

   bool    on_local_stack(address adr) const {

     /* QQQ this has knowledge of direction, ought to be a stack method */

     return (_stack_base >= adr && adr >= (_stack_base - _stack_size));

   }

   uintptr_t self_raw_id()                    { return _self_raw_id; }

   void      set_self_raw_id(uintptr_t value) { _self_raw_id = value; }

   int     lgrp_id() const        { return _lgrp_id; }

   void    set_lgrp_id(int value) { _lgrp_id = value; }

   // Printing

   void print_on(outputStream* st) const;

   void print() const { print_on(tty); }

   virtual void print_on_error(outputStream* st, char* buf, int buflen) const;

   // Debug-only code

 #ifdef ASSERT

  private:

   // Deadlock detection support for Mutex locks. List of locks own by thread.

   Monitor* _owned_locks;

   // Mutex::set_owner_implementation is the only place where _owned_locks is modified,

   // thus the friendship

   friend class Mutex;

   friend class Monitor;

  public:

   void print_owned_locks_on(outputStream* st) const;

   void print_owned_locks() const                 { print_owned_locks_on(tty);    }

   Monitor* owned_locks() const                   { return _owned_locks;          }

   bool owns_locks() const                        { return owned_locks() != NULL; }

   bool owns_locks_but_compiled_lock() const;

   // Deadlock detection

   bool allow_allocation()                        { return _allow_allocation_count == 0; }

 #endif

   void check_for_valid_safepoint_state(bool potential_vm_operation) PRODUCT_RETURN;

  private:

   volatile int _jvmti_env_iteration_count;

  public:

   void entering_jvmti_env_iteration()            { ++_jvmti_env_iteration_count; }

   void leaving_jvmti_env_iteration()             { --_jvmti_env_iteration_count; }

   bool is_inside_jvmti_env_iteration()           { return _jvmti_env_iteration_count > 0; }

   // Code generation

   static ByteSize exception_file_offset()        { return byte_offset_of(Thread, _exception_file   ); }

   static ByteSize exception_line_offset()        { return byte_offset_of(Thread, _exception_line   ); }

   static ByteSize active_handles_offset()        { return byte_offset_of(Thread, _active_handles   ); }

   static ByteSize stack_base_offset()            { return byte_offset_of(Thread, _stack_base ); }

   static ByteSize stack_size_offset()            { return byte_offset_of(Thread, _stack_size ); }

 #define TLAB_FIELD_OFFSET(name) \

   static ByteSize tlab_##name##_offset()         { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::name##_offset(); }

   TLAB_FIELD_OFFSET(start)

   TLAB_FIELD_OFFSET(end)

   TLAB_FIELD_OFFSET(top)

   TLAB_FIELD_OFFSET(pf_top)

   TLAB_FIELD_OFFSET(size)                   // desired_size

   TLAB_FIELD_OFFSET(refill_waste_limit)

   TLAB_FIELD_OFFSET(number_of_refills)

   TLAB_FIELD_OFFSET(fast_refill_waste)

   TLAB_FIELD_OFFSET(slow_allocations)

 #undef TLAB_FIELD_OFFSET

   static ByteSize allocated_bytes_offset()       { return byte_offset_of(Thread, _allocated_bytes ); }

  public:

   volatile intptr_t _Stalled ;

   volatile int _TypeTag ;

   ParkEvent * _ParkEvent ;                     // for synchronized()

   ParkEvent * _SleepEvent ;                    // for Thread.sleep

   ParkEvent * _MutexEvent ;                    // for native internal Mutex/Monitor

   ParkEvent * _MuxEvent ;                      // for low-level muxAcquire-muxRelease

   int NativeSyncRecursion ;                    // diagnostic

   volatile int _OnTrap ;                       // Resume-at IP delta

   jint _hashStateW ;                           // Marsaglia Shift-XOR thread-local RNG

   jint _hashStateX ;                           // thread-specific hashCode generator state

   jint _hashStateY ;

   jint _hashStateZ ;

   void * _schedctl ;

   intptr_t _ScratchA, _ScratchB ;              // Scratch locations for fast-path sync code

   static ByteSize ScratchA_offset()            { return byte_offset_of(Thread, _ScratchA ); }

   static ByteSize ScratchB_offset()            { return byte_offset_of(Thread, _ScratchB ); }

   volatile jint rng [4] ;                      // RNG for spin loop

   // Low-level leaf-lock primitives used to implement synchronization

   // and native monitor-mutex infrastructure.

   // Not for general synchronization use.

   static void SpinAcquire (volatile int * Lock, const char * Name) ;

   static void SpinRelease (volatile int * Lock) ;

   static void muxAcquire  (volatile intptr_t * Lock, const char * Name) ;

   static void muxAcquireW (volatile intptr_t * Lock, ParkEvent * ev) ;

   static void muxRelease  (volatile intptr_t * Lock) ;

 };

 // Inline implementation of Thread::current()

 // Thread::current is "hot" it's called > 128K times in the 1st 500 msecs of

 // startup.

 // ThreadLocalStorage::thread is warm -- it's called > 16K times in the same

 // period.   This is inlined in thread_<os_family>.inline.hpp.

 inline Thread* Thread::current() {

 #ifdef ASSERT

 // This function is very high traffic. Define PARANOID to enable expensive

 // asserts.

 #ifdef PARANOID

   // Signal handler should call ThreadLocalStorage::get_thread_slow()

   Thread* t = ThreadLocalStorage::get_thread_slow();

   assert(t != NULL && !t->is_inside_signal_handler(),

          "Don't use Thread::current() inside signal handler");

 #endif

 #endif

   Thread* thread = ThreadLocalStorage::thread();

   assert(thread != NULL, "just checking");

   return thread;

 }

 // Name support for threads.  non-JavaThread subclasses with multiple

 // uniquely named instances should derive from this.

 class NamedThread: public Thread {

   friend class VMStructs;

   enum {

     max_name_len = 64

   };

  private:

   char* _name;

   // log JavaThread being processed by oops_do

   JavaThread* _processed_thread;

  public:

   NamedThread();

   ~NamedThread();

   // May only be called once per thread.

   void set_name(const char* format, ...);

   virtual bool is_Named_thread() const { return true; }

   virtual char* name() const { return _name == NULL ? (char*)"Unknown Thread" : _name; }

   JavaThread *processed_thread() { return _processed_thread; }

   void set_processed_thread(JavaThread *thread) { _processed_thread = thread; }

 };

 // Worker threads are named and have an id of an assigned work.

 class WorkerThread: public NamedThread {

 private:

   uint _id;

 public:

   WorkerThread() : _id(0)               { }

   virtual bool is_Worker_thread() const { return true; }

   virtual WorkerThread* as_Worker_thread() const {

     assert(is_Worker_thread(), "Dubious cast to WorkerThread*?");

     return (WorkerThread*) this;

   }

   void set_id(uint work_id)             { _id = work_id; }

   uint id() const                       { return _id; }

 };

 // A single WatcherThread is used for simulating timer interrupts.

 class WatcherThread: public Thread {

   friend class VMStructs;

  public:

   virtual void run();

  private:

   static WatcherThread* _watcher_thread;

   volatile static bool _should_terminate; // updated without holding lock

  public:

   enum SomeConstants {

     delay_interval = 10                          // interrupt delay in milliseconds

   };

   // Constructor

   WatcherThread();

   // Tester

   bool is_Watcher_thread() const                 { return true; }

   // Printing

   char* name() const { return (char*)"VM Periodic Task Thread"; }

   void print_on(outputStream* st) const;

   void print() const { print_on(tty); }

   // Returns the single instance of WatcherThread

   static WatcherThread* watcher_thread()         { return _watcher_thread; }

   // Create and start the single instance of WatcherThread, or stop it on shutdown

   static void start();

   static void stop();

 };

 class CompilerThread;

 typedef void (*ThreadFunction)(JavaThread*, TRAPS);

 class JavaThread: public Thread {

   friend class VMStructs;

  private:

   JavaThread*    _next;                          // The next thread in the Threads list

   oop            _threadObj;                     // The Java level thread object

 #ifdef ASSERT

  private:

   int _java_call_counter;

  public:

   int  java_call_counter()                       { return _java_call_counter; }

   void inc_java_call_counter()                   { _java_call_counter++; }

   void dec_java_call_counter() {

     assert(_java_call_counter > 0, "Invalid nesting of JavaCallWrapper");

     _java_call_counter--;

   }

  private:  // restore original namespace restriction

 #endif  // ifdef ASSERT

 #ifndef PRODUCT

  public:

   enum {

     jump_ring_buffer_size = 16

   };

  private:  // restore original namespace restriction

 #endif

   JavaFrameAnchor _anchor;                       // Encapsulation of current java frame and it state

   ThreadFunction _entry_point;

   JNIEnv        _jni_environment;

   // Deopt support

   DeoptResourceMark*  _deopt_mark;               // Holds special ResourceMark for deoptimization

   intptr_t*      _must_deopt_id;                 // id of frame that needs to be deopted once we

                                                  // transition out of native

   nmethod*       _deopt_nmethod;                 // nmethod that is currently being deoptimized

   vframeArray*  _vframe_array_head;              // Holds the heap of the active vframeArrays

   vframeArray*  _vframe_array_last;              // Holds last vFrameArray we popped

   // Because deoptimization is lazy we must save jvmti requests to set locals

   // in compiled frames until we deoptimize and we have an interpreter frame.

   // This holds the pointer to array (yeah like there might be more than one) of

   // description of compiled vframes that have locals that need to be updated.

   GrowableArray<jvmtiDeferredLocalVariableSet*>* _deferred_locals_updates;

   // Handshake value for fixing 6243940. We need a place for the i2c

   // adapter to store the callee methodOop. This value is NEVER live

   // across a gc point so it does NOT have to be gc'd

   // The handshake is open ended since we can't be certain that it will

   // be NULLed. This is because we rarely ever see the race and end up

   // in handle_wrong_method which is the backend of the handshake. See

   // code in i2c adapters and handle_wrong_method.

   methodOop     _callee_target;

   // Oop results of VM runtime calls

   oop           _vm_result;    // Used to pass back an oop result into Java code, GC-preserved

   oop           _vm_result_2;  // Used to pass back an oop result into Java code, GC-preserved

   // See ReduceInitialCardMarks: this holds the precise space interval of

   // the most recent slow path allocation for which compiled code has

   // elided card-marks for performance along the fast-path.

   MemRegion     _deferred_card_mark;

   MonitorChunk* _monitor_chunks;                 // Contains the off stack monitors

                                                  // allocated during deoptimization

                                                  // and by JNI_MonitorEnter/Exit

   // Async. requests support

   enum AsyncRequests {

     _no_async_condition = 0,

     _async_exception,

     _async_unsafe_access_error

   };

   AsyncRequests _special_runtime_exit_condition; // Enum indicating pending async. request

   oop           _pending_async_exception;

   // Safepoint support

  public:                                         // Expose _thread_state for SafeFetchInt()

   volatile JavaThreadState _thread_state;

  private:

   ThreadSafepointState *_safepoint_state;        // Holds information about a thread during a safepoint

   address               _saved_exception_pc;     // Saved pc of instruction where last implicit exception happened

   // JavaThread termination support

   enum TerminatedTypes {

     _not_terminated = 0xDEAD - 2,

     _thread_exiting,                             // JavaThread::exit() has been called for this thread

     _thread_terminated,                          // JavaThread is removed from thread list

     _vm_exited                                   // JavaThread is still executing native code, but VM is terminated

                                                  // only VM_Exit can set _vm_exited

   };

   // In general a JavaThread's _terminated field transitions as follows:

   //

   //   _not_terminated => _thread_exiting => _thread_terminated

   //

   // _vm_exited is a special value to cover the case of a JavaThread

   // executing native code after the VM itself is terminated.

   volatile TerminatedTypes _terminated;

   // suspend/resume support

   volatile bool         _suspend_equivalent;     // Suspend equivalent condition

   jint                  _in_deopt_handler;       // count of deoptimization

                                                  // handlers thread is in

   volatile bool         _doing_unsafe_access;    // Thread may fault due to unsafe access

   bool                  _do_not_unlock_if_synchronized; // Do not unlock the receiver of a synchronized method (since it was

                                                  // never locked) when throwing an exception. Used by interpreter only.

   // JNI attach states:

   enum JNIAttachStates {

     _not_attaching_via_jni = 1,  // thread is not attaching via JNI

     _attaching_via_jni,          // thread is attaching via JNI

     _attached_via_jni            // thread has attached via JNI

   };

   // A regular JavaThread's _jni_attach_state is _not_attaching_via_jni.

   // A native thread that is attaching via JNI starts with a value

   // of _attaching_via_jni and transitions to _attached_via_jni.

   volatile JNIAttachStates _jni_attach_state;

  public:

   // State of the stack guard pages for this thread.

   enum StackGuardState {

     stack_guard_unused,         // not needed

     stack_guard_yellow_disabled,// disabled (temporarily) after stack overflow

     stack_guard_enabled         // enabled

   };

  private:

   StackGuardState        _stack_guard_state;

   // Compiler exception handling (NOTE: The _exception_oop is *NOT* the same as _pending_exception. It is

   // used to temp. parsing values into and out of the runtime system during exception handling for compiled

   // code)

   volatile oop     _exception_oop;               // Exception thrown in compiled code

   volatile address _exception_pc;                // PC where exception happened

   volatile address _exception_handler_pc;        // PC for handler of exception

   volatile int     _is_method_handle_return;     // true (== 1) if the current exception PC is a MethodHandle call site.

   // support for compilation

   bool    _is_compiling;                         // is true if a compilation is active inthis thread (one compilation per thread possible)

   // support for JNI critical regions

   jint    _jni_active_critical;                  // count of entries into JNI critical region

   // For deadlock detection.

   int _depth_first_number;

   // JVMTI PopFrame support

   // This is set to popframe_pending to signal that top Java frame should be popped immediately

   int _popframe_condition;

 #ifndef PRODUCT

   int _jmp_ring_index;

   struct {

       // We use intptr_t instead of address so debugger doesn't try and display strings

       intptr_t _target;

       intptr_t _instruction;

       const char*  _file;

       int _line;

   }   _jmp_ring[ jump_ring_buffer_size ];

 #endif /* PRODUCT */

 #ifndef SERIALGC

   // Support for G1 barriers

   ObjPtrQueue _satb_mark_queue;          // Thread-local log for SATB barrier.

   // Set of all such queues.

   static SATBMarkQueueSet _satb_mark_queue_set;

   DirtyCardQueue _dirty_card_queue;      // Thread-local log for dirty cards.

   // Set of all such queues.

   static DirtyCardQueueSet _dirty_card_queue_set;

   void flush_barrier_queues();

 #endif // !SERIALGC

   friend class VMThread;

   friend class ThreadWaitTransition;

   friend class VM_Exit;

   void initialize();                             // Initialized the instance variables

  public:

   // Constructor

   JavaThread(bool is_attaching_via_jni = false); // for main thread and JNI attached threads

   JavaThread(ThreadFunction entry_point, size_t stack_size = 0);

   ~JavaThread();

 #ifdef ASSERT

   // verify this JavaThread hasn't be published in the Threads::list yet

   void verify_not_published();

 #endif

   //JNI functiontable getter/setter for JVMTI jni function table interception API.

   void set_jni_functions(struct JNINativeInterface_* functionTable) {

     _jni_environment.functions = functionTable;

   }

   struct JNINativeInterface_* get_jni_functions() {

     return (struct JNINativeInterface_ *)_jni_environment.functions;

   }

   // This function is called at thread creation to allow

   // platform specific thread variables to be initialized.

   void cache_global_variables();

   // Executes Shutdown.shutdown()

   void invoke_shutdown_hooks();

   // Cleanup on thread exit

   enum ExitType {

     normal_exit,

     jni_detach

   };

   void exit(bool destroy_vm, ExitType exit_type = normal_exit);

   void cleanup_failed_attach_current_thread();

   // Testers

   virtual bool is_Java_thread() const            { return true;  }

   // compilation

   void set_is_compiling(bool f)                  { _is_compiling = f; }

   bool is_compiling() const                      { return _is_compiling; }

   // Thread chain operations

   JavaThread* next() const                       { return _next; }

   void set_next(JavaThread* p)                   { _next = p; }

   // Thread oop. threadObj() can be NULL for initial JavaThread

   // (or for threads attached via JNI)

   oop threadObj() const                          { return _threadObj; }

   void set_threadObj(oop p)                      { _threadObj = p; }

   ThreadPriority java_priority() const;          // Read from threadObj()

   // Prepare thread and add to priority queue.  If a priority is

   // not specified, use the priority of the thread object. Threads_lock

   // must be held while this function is called.

   void prepare(jobject jni_thread, ThreadPriority prio=NoPriority);

   void set_saved_exception_pc(address pc)        { _saved_exception_pc = pc; }

   address saved_exception_pc()                   { return _saved_exception_pc; }

   ThreadFunction entry_point() const             { return _entry_point; }

   // Allocates a new Java level thread object for this thread. thread_name may be NULL.

   void allocate_threadObj(Handle thread_group, char* thread_name, bool daemon, TRAPS);

   // Last frame anchor routines

   JavaFrameAnchor* frame_anchor(void)                { return &_anchor; }

   // last_Java_sp

   bool has_last_Java_frame() const                   { return _anchor.has_last_Java_frame(); }

   intptr_t* last_Java_sp() const                     { return _anchor.last_Java_sp(); }

   // last_Java_pc

   address last_Java_pc(void)                         { return _anchor.last_Java_pc(); }

   // Safepoint support

   JavaThreadState thread_state() const           { return _thread_state; }

   void set_thread_state(JavaThreadState s)       { _thread_state=s;      }

   ThreadSafepointState *safepoint_state() const  { return _safepoint_state;  }

   void set_safepoint_state(ThreadSafepointState *state) { _safepoint_state = state; }

   bool is_at_poll_safepoint()                    { return _safepoint_state->is_at_poll_safepoint(); }

   // thread has called JavaThread::exit() or is terminated

   bool is_exiting()                              { return _terminated == _thread_exiting || is_terminated(); }

   // thread is terminated (no longer on the threads list); we compare

   // against the two non-terminated values so that a freed JavaThread

   // will also be considered terminated.

   bool is_terminated()                           { return _terminated != _not_terminated && _terminated != _thread_exiting; }

   void set_terminated(TerminatedTypes t)         { _terminated = t; }

   // special for Threads::remove() which is static:

   void set_terminated_value()                    { _terminated = _thread_terminated; }

   void block_if_vm_exited();

   bool doing_unsafe_access()                     { return _doing_unsafe_access; }

   void set_doing_unsafe_access(bool val)         { _doing_unsafe_access = val; }

   bool do_not_unlock_if_synchronized()             { return _do_not_unlock_if_synchronized; }

   void set_do_not_unlock_if_synchronized(bool val) { _do_not_unlock_if_synchronized = val; }

   // native memory tracking

   inline MemRecorder* get_recorder() const          { return (MemRecorder*)_recorder; }

   inline void         set_recorder(MemRecorder* rc) { _recorder = (volatile MemRecorder*)rc; }

  private:

   // per-thread memory recorder

   volatile MemRecorder* _recorder;

   // Suspend/resume support for JavaThread

  private:

   void set_ext_suspended()       { set_suspend_flag (_ext_suspended);  }

   void clear_ext_suspended()     { clear_suspend_flag(_ext_suspended); }

  public:

   void java_suspend();

   void java_resume();

   int  java_suspend_self();

   void check_and_wait_while_suspended() {

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

     bool do_self_suspend;

     do {

       // were we externally suspended while we were waiting?

       do_self_suspend = handle_special_suspend_equivalent_condition();

       if (do_self_suspend) {

         // don't surprise the thread that suspended us by returning

         java_suspend_self();

         set_suspend_equivalent();

       }

     } while (do_self_suspend);

   }

   static void check_safepoint_and_suspend_for_native_trans(JavaThread *thread);

   // Check for async exception in addition to safepoint and suspend request.

   static void check_special_condition_for_native_trans(JavaThread *thread);

   // Same as check_special_condition_for_native_trans but finishes the

   // transition into thread_in_Java mode so that it can potentially

   // block.

   static void check_special_condition_for_native_trans_and_transition(JavaThread *thread);

   bool is_ext_suspend_completed(bool called_by_wait, int delay, uint32_t *bits);

   bool is_ext_suspend_completed_with_lock(uint32_t *bits) {

     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);

     // Warning: is_ext_suspend_completed() may temporarily drop the

     // SR_lock to allow the thread to reach a stable thread state if

     // it is currently in a transient thread state.

     return is_ext_suspend_completed(false /*!called_by_wait */,

                                     SuspendRetryDelay, bits);

   }

   // We cannot allow wait_for_ext_suspend_completion() to run forever or

   // we could hang. SuspendRetryCount and SuspendRetryDelay are normally

   // passed as the count and delay parameters. Experiments with specific

   // calls to wait_for_ext_suspend_completion() can be done by passing

   // other values in the code. Experiments with all calls can be done

   // via the appropriate -XX options.

   bool wait_for_ext_suspend_completion(int count, int delay, uint32_t *bits);

   void set_external_suspend()     { set_suspend_flag  (_external_suspend); }

   void clear_external_suspend()   { clear_suspend_flag(_external_suspend); }

   void set_deopt_suspend()        { set_suspend_flag  (_deopt_suspend); }

   void clear_deopt_suspend()      { clear_suspend_flag(_deopt_suspend); }

   bool is_deopt_suspend()         { return (_suspend_flags & _deopt_suspend) != 0; }

   bool is_external_suspend() const {

     return (_suspend_flags & _external_suspend) != 0;

   }

   // Whenever a thread transitions from native to vm/java it must suspend

   // if external|deopt suspend is present.

   bool is_suspend_after_native() const {

     return (_suspend_flags & (_external_suspend | _deopt_suspend) ) != 0;

   }

   // external suspend request is completed

   bool is_ext_suspended() const {

     return (_suspend_flags & _ext_suspended) != 0;

   }

   bool is_external_suspend_with_lock() const {

     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);

     return is_external_suspend();

   }

   // Special method to handle a pending external suspend request

   // when a suspend equivalent condition lifts.

   bool handle_special_suspend_equivalent_condition() {

     assert(is_suspend_equivalent(),

       "should only be called in a suspend equivalence condition");

     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);

     bool ret = is_external_suspend();

     if (!ret) {

       // not about to self-suspend so clear suspend equivalence

       clear_suspend_equivalent();

     }

     // implied else:

     // We have a pending external suspend request so we leave the

     // suspend_equivalent flag set until java_suspend_self() sets

     // the ext_suspended flag and clears the suspend_equivalent

     // flag. This insures that wait_for_ext_suspend_completion()

     // will return consistent values.

     return ret;

   }

   // utility methods to see if we are doing some kind of suspension

   bool is_being_ext_suspended() const            {

     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);

     return is_ext_suspended() || is_external_suspend();

   }

   bool is_suspend_equivalent() const             { return _suspend_equivalent; }

   void set_suspend_equivalent()                  { _suspend_equivalent = true; };

   void clear_suspend_equivalent()                { _suspend_equivalent = false; };

   // Thread.stop support

   void send_thread_stop(oop throwable);

   AsyncRequests clear_special_runtime_exit_condition() {

     AsyncRequests x = _special_runtime_exit_condition;

     _special_runtime_exit_condition = _no_async_condition;

     return x;

   }

   // Are any async conditions present?

   bool has_async_condition() { return (_special_runtime_exit_condition != _no_async_condition); }

   void check_and_handle_async_exceptions(bool check_unsafe_error = true);

   // these next two are also used for self-suspension and async exception support

   void handle_special_runtime_exit_condition(bool check_asyncs = true);

   // Return true if JavaThread has an asynchronous condition or

   // if external suspension is requested.

   bool has_special_runtime_exit_condition() {

     // We call is_external_suspend() last since external suspend should

     // be less common. Because we don't use is_external_suspend_with_lock

     // it is possible that we won't see an asynchronous external suspend

     // request that has just gotten started, i.e., SR_lock grabbed but

     // _external_suspend field change either not made yet or not visible

     // yet. However, this is okay because the request is asynchronous and

     // we will see the new flag value the next time through. It's also

     // possible that the external suspend request is dropped after

     // we have checked is_external_suspend(), we will recheck its value

     // under SR_lock in java_suspend_self().

     return (_special_runtime_exit_condition != _no_async_condition) ||

             is_external_suspend() || is_deopt_suspend();

   }

   void set_pending_unsafe_access_error()          { _special_runtime_exit_condition = _async_unsafe_access_error; }

   void set_pending_async_exception(oop e) {

     _pending_async_exception = e;

     _special_runtime_exit_condition = _async_exception;

     set_has_async_exception();

   }

   // Fast-locking support

   bool is_lock_owned(address adr) const;

   // Accessors for vframe array top

   // The linked list of vframe arrays are sorted on sp. This means when we

   // unpack the head must contain the vframe array to unpack.

   void set_vframe_array_head(vframeArray* value) { _vframe_array_head = value; }

   vframeArray* vframe_array_head() const         { return _vframe_array_head;  }

   // Side structure for defering update of java frame locals until deopt occurs

   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred_locals() const { return _deferred_locals_updates; }

   void set_deferred_locals(GrowableArray<jvmtiDeferredLocalVariableSet *>* vf) { _deferred_locals_updates = vf; }

   // These only really exist to make debugging deopt problems simpler

   void set_vframe_array_last(vframeArray* value) { _vframe_array_last = value; }

   vframeArray* vframe_array_last() const         { return _vframe_array_last;  }

   // The special resourceMark used during deoptimization

   void set_deopt_mark(DeoptResourceMark* value)  { _deopt_mark = value; }

   DeoptResourceMark* deopt_mark(void)            { return _deopt_mark; }

   intptr_t* must_deopt_id()                      { return _must_deopt_id; }

   void     set_must_deopt_id(intptr_t* id)       { _must_deopt_id = id; }

   void     clear_must_deopt_id()                 { _must_deopt_id = NULL; }

   void set_deopt_nmethod(nmethod* nm)            { _deopt_nmethod = nm;   }

   nmethod* deopt_nmethod()                       { return _deopt_nmethod; }

   methodOop  callee_target() const               { return _callee_target; }

   void set_callee_target  (methodOop x)          { _callee_target   = x; }

   // Oop results of vm runtime calls

   oop  vm_result() const                         { return _vm_result; }

   void set_vm_result  (oop x)                    { _vm_result   = x; }

   oop  vm_result_2() const                       { return _vm_result_2; }

   void set_vm_result_2  (oop x)                  { _vm_result_2   = x; }

   MemRegion deferred_card_mark() const           { return _deferred_card_mark; }

   void set_deferred_card_mark(MemRegion mr)      { _deferred_card_mark = mr;   }

   // Exception handling for compiled methods

   oop      exception_oop() const                 { return _exception_oop; }

   address  exception_pc() const                  { return _exception_pc; }

   address  exception_handler_pc() const          { return _exception_handler_pc; }

   bool     is_method_handle_return() const       { return _is_method_handle_return == 1; }

   void set_exception_oop(oop o)                  { _exception_oop = o; }

   void set_exception_pc(address a)               { _exception_pc = a; }

   void set_exception_handler_pc(address a)       { _exception_handler_pc = a; }

   void set_is_method_handle_return(bool value)   { _is_method_handle_return = value ? 1 : 0; }

   // Stack overflow support

   inline size_t stack_available(address cur_sp);

   address stack_yellow_zone_base()

     { return (address)(stack_base() - (stack_size() - (stack_red_zone_size() + stack_yellow_zone_size()))); }

   size_t  stack_yellow_zone_size()

     { return StackYellowPages * os::vm_page_size(); }

   address stack_red_zone_base()

     { return (address)(stack_base() - (stack_size() - stack_red_zone_size())); }

   size_t stack_red_zone_size()

     { return StackRedPages * os::vm_page_size(); }

   bool in_stack_yellow_zone(address a)

     { return (a <= stack_yellow_zone_base()) && (a >= stack_red_zone_base()); }

   bool in_stack_red_zone(address a)

     { return (a <= stack_red_zone_base()) && (a >= (address)((intptr_t)stack_base() - stack_size())); }

   void create_stack_guard_pages();

   void remove_stack_guard_pages();

   void enable_stack_yellow_zone();

   void disable_stack_yellow_zone();

   void enable_stack_red_zone();

   void disable_stack_red_zone();

   inline bool stack_yellow_zone_disabled();

   inline bool stack_yellow_zone_enabled();

   // Attempt to reguard the stack after a stack overflow may have occurred.

   // Returns true if (a) guard pages are not needed on this thread, (b) the

   // pages are already guarded, or (c) the pages were successfully reguarded.

   // Returns false if there is not enough stack space to reguard the pages, in

   // which case the caller should unwind a frame and try again.  The argument

   // should be the caller's (approximate) sp.

   bool reguard_stack(address cur_sp);

   // Similar to above but see if current stackpoint is out of the guard area

   // and reguard if possible.

   bool reguard_stack(void);

   // Misc. accessors/mutators

   void set_do_not_unlock(void)                   { _do_not_unlock_if_synchronized = true; }

   void clr_do_not_unlock(void)                   { _do_not_unlock_if_synchronized = false; }

   bool do_not_unlock(void)                       { return _do_not_unlock_if_synchronized; }

 #ifndef PRODUCT

   void record_jump(address target, address instr, const char* file, int line);

 #endif /* PRODUCT */

   // For assembly stub generation

   static ByteSize threadObj_offset()             { return byte_offset_of(JavaThread, _threadObj           ); }

 #ifndef PRODUCT

   static ByteSize jmp_ring_index_offset()        { return byte_offset_of(JavaThread, _jmp_ring_index      ); }

   static ByteSize jmp_ring_offset()              { return byte_offset_of(JavaThread, _jmp_ring            ); }

 #endif /* PRODUCT */

   static ByteSize jni_environment_offset()       { return byte_offset_of(JavaThread, _jni_environment     ); }

   static ByteSize last_Java_sp_offset()          {

     return byte_offset_of(JavaThread, _anchor) + JavaFrameAnchor::last_Java_sp_offset();

   }

   static ByteSize last_Java_pc_offset()          {

     return byte_offset_of(JavaThread, _anchor) + JavaFrameAnchor::last_Java_pc_offset();

   }

   static ByteSize frame_anchor_offset()          {

     return byte_offset_of(JavaThread, _anchor);

   }

   static ByteSize callee_target_offset()         { return byte_offset_of(JavaThread, _callee_target       ); }

   static ByteSize vm_result_offset()             { return byte_offset_of(JavaThread, _vm_result           ); }

   static ByteSize vm_result_2_offset()           { return byte_offset_of(JavaThread, _vm_result_2         ); }

   static ByteSize thread_state_offset()          { return byte_offset_of(JavaThread, _thread_state        ); }

   static ByteSize saved_exception_pc_offset()    { return byte_offset_of(JavaThread, _saved_exception_pc  ); }

   static ByteSize osthread_offset()              { return byte_offset_of(JavaThread, _osthread            ); }

   static ByteSize exception_oop_offset()         { return byte_offset_of(JavaThread, _exception_oop       ); }

   static ByteSize exception_pc_offset()          { return byte_offset_of(JavaThread, _exception_pc        ); }

   static ByteSize exception_handler_pc_offset()  { return byte_offset_of(JavaThread, _exception_handler_pc); }

   static ByteSize is_method_handle_return_offset() { return byte_offset_of(JavaThread, _is_method_handle_return); }

   static ByteSize stack_guard_state_offset()     { return byte_offset_of(JavaThread, _stack_guard_state   ); }

   static ByteSize suspend_flags_offset()         { return byte_offset_of(JavaThread, _suspend_flags       ); }

   static ByteSize do_not_unlock_if_synchronized_offset() { return byte_offset_of(JavaThread, _do_not_unlock_if_synchronized); }

   static ByteSize should_post_on_exceptions_flag_offset() {

     return byte_offset_of(JavaThread, _should_post_on_exceptions_flag);

   }

 #ifndef SERIALGC

   static ByteSize satb_mark_queue_offset()       { return byte_offset_of(JavaThread, _satb_mark_queue); }

   static ByteSize dirty_card_queue_offset()      { return byte_offset_of(JavaThread, _dirty_card_queue); }

 #endif // !SERIALGC

   // Returns the jni environment for this thread

   JNIEnv* jni_environment()                      { return &_jni_environment; }

   static JavaThread* thread_from_jni_environment(JNIEnv* env) {

     JavaThread *thread_from_jni_env = (JavaThread*)((intptr_t)env - in_bytes(jni_environment_offset()));

     // Only return NULL if thread is off the thread list; starting to

     // exit should not return NULL.

     if (thread_from_jni_env->is_terminated()) {

        thread_from_jni_env->block_if_vm_exited();

        return NULL;

     } else {

        return thread_from_jni_env;

     }

   }

   // JNI critical regions. These can nest.

   bool in_critical()    { return _jni_active_critical > 0; }

   bool in_last_critical()  { return _jni_active_critical == 1; }

   void enter_critical() { assert(Thread::current() == this ||

                                  Thread::current()->is_VM_thread() && SafepointSynchronize::is_synchronizing(),

                                  "this must be current thread or synchronizing");

                           _jni_active_critical++; }

   void exit_critical()  { assert(Thread::current() == this,

                                  "this must be current thread");

                           _jni_active_critical--;

                           assert(_jni_active_critical >= 0,

                                  "JNI critical nesting problem?"); }

   // For deadlock detection

   int depth_first_number() { return _depth_first_number; }

   void set_depth_first_number(int dfn) { _depth_first_number = dfn; }

  private:

   void set_monitor_chunks(MonitorChunk* monitor_chunks) { _monitor_chunks = monitor_chunks; }

  public:

   MonitorChunk* monitor_chunks() const           { return _monitor_chunks; }

   void add_monitor_chunk(MonitorChunk* chunk);

   void remove_monitor_chunk(MonitorChunk* chunk);

   bool in_deopt_handler() const                  { return _in_deopt_handler > 0; }

   void inc_in_deopt_handler()                    { _in_deopt_handler++; }

   void dec_in_deopt_handler()                    {

     assert(_in_deopt_handler > 0, "mismatched deopt nesting");

     if (_in_deopt_handler > 0) { // robustness

       _in_deopt_handler--;

     }

   }

  private:

   void set_entry_point(ThreadFunction entry_point) { _entry_point = entry_point; }

  public:

   // Frame iteration; calls the function f for all frames on the stack

   void frames_do(void f(frame*, const RegisterMap*));

   // Memory operations

   void oops_do(OopClosure* f, CodeBlobClosure* cf);

   // Sweeper operations

   void nmethods_do(CodeBlobClosure* cf);

   // Memory management operations

   void gc_epilogue();

   void gc_prologue();

   // Misc. operations

   char* name() const { return (char*)get_thread_name(); }

   void print_on(outputStream* st) const;

   void print() const { print_on(tty); }

   void print_value();

   void print_thread_state_on(outputStream* ) const      PRODUCT_RETURN;

   void print_thread_state() const                       PRODUCT_RETURN;

   void print_on_error(outputStream* st, char* buf, int buflen) const;

   void verify();

   const char* get_thread_name() const;

 private:

   // factor out low-level mechanics for use in both normal and error cases

   const char* get_thread_name_string(char* buf = NULL, int buflen = 0) const;

 public:

   const char* get_threadgroup_name() const;

   const char* get_parent_name() const;

   // Accessing frames

   frame last_frame() {

     _anchor.make_walkable(this);

     return pd_last_frame();

   }

   javaVFrame* last_java_vframe(RegisterMap* reg_map);

   // Returns method at 'depth' java or native frames down the stack

   // Used for security checks

   klassOop security_get_caller_class(int depth);

   // Print stack trace in external format

   void print_stack_on(outputStream* st);

   void print_stack() { print_stack_on(tty); }

   // Print stack traces in various internal formats

   void trace_stack()                             PRODUCT_RETURN;

   void trace_stack_from(vframe* start_vf)        PRODUCT_RETURN;

   void trace_frames()                            PRODUCT_RETURN;

   void trace_oops()                              PRODUCT_RETURN;

   // Print an annotated view of the stack frames

   void print_frame_layout(int depth = 0, bool validate_only = false) NOT_DEBUG_RETURN;

   void validate_frame_layout() {

     print_frame_layout(0, true);

   }

   // Returns the number of stack frames on the stack

   int depth() const;

   // Function for testing deoptimization

   void deoptimize();

   void make_zombies();

   void deoptimized_wrt_marked_nmethods();

   // Profiling operation (see fprofile.cpp)

  public:

    bool profile_last_Java_frame(frame* fr);

  private:

    ThreadProfiler* _thread_profiler;

  private:

    friend class FlatProfiler;                    // uses both [gs]et_thread_profiler.

    friend class FlatProfilerTask;                // uses get_thread_profiler.

    friend class ThreadProfilerMark;              // uses get_thread_profiler.

    ThreadProfiler* get_thread_profiler()         { return _thread_profiler; }

    ThreadProfiler* set_thread_profiler(ThreadProfiler* tp) {

      ThreadProfiler* result = _thread_profiler;

      _thread_profiler = tp;

      return result;

    }

  // NMT (Native memory tracking) support.

  // This flag helps NMT to determine if this JavaThread will be blocked

  // at safepoint. If not, ThreadCritical is needed for writing memory records.

  // JavaThread is only safepoint visible when it is in Threads' thread list,

  // it is not visible until it is added to the list and becomes invisible

  // once it is removed from the list.

  public:

   bool is_safepoint_visible() const { return _safepoint_visible; }

   void set_safepoint_visible(bool visible) { _safepoint_visible = visible; }

  private:

   bool _safepoint_visible;

   // Static operations

  public:

   // Returns the running thread as a JavaThread

   static inline JavaThread* current();

   // Returns the active Java thread.  Do not use this if you know you are calling

   // from a JavaThread, as it's slower than JavaThread::current.  If called from

   // the VMThread, it also returns the JavaThread that instigated the VMThread's

   // operation.  You may not want that either.

   static JavaThread* active();

   inline CompilerThread* as_CompilerThread();

  public:

   virtual void run();

   void thread_main_inner();

  private:

   // PRIVILEGED STACK

   PrivilegedElement*  _privileged_stack_top;

   GrowableArray<oop>* _array_for_gc;

  public:

   // Returns the privileged_stack information.

   PrivilegedElement* privileged_stack_top() const       { return _privileged_stack_top; }

   void set_privileged_stack_top(PrivilegedElement *e)   { _privileged_stack_top = e; }

   void register_array_for_gc(GrowableArray<oop>* array) { _array_for_gc = array; }

  public:

   // Thread local information maintained by JVMTI.

   void set_jvmti_thread_state(JvmtiThreadState *value)                           { _jvmti_thread_state = value; }

   // A JvmtiThreadState is lazily allocated. This jvmti_thread_state()

   // getter is used to get this JavaThread's JvmtiThreadState if it has

   // one which means NULL can be returned. JvmtiThreadState::state_for()

   // is used to get the specified JavaThread's JvmtiThreadState if it has

   // one or it allocates a new JvmtiThreadState for the JavaThread and

   // returns it. JvmtiThreadState::state_for() will return NULL only if

   // the specified JavaThread is exiting.

   JvmtiThreadState *jvmti_thread_state() const                                   { return _jvmti_thread_state; }

   static ByteSize jvmti_thread_state_offset()                                    { return byte_offset_of(JavaThread, _jvmti_thread_state); }

   void set_jvmti_get_loaded_classes_closure(JvmtiGetLoadedClassesClosure* value) { _jvmti_get_loaded_classes_closure = value; }

   JvmtiGetLoadedClassesClosure* get_jvmti_get_loaded_classes_closure() const     { return _jvmti_get_loaded_classes_closure; }

   // JVMTI PopFrame support

   // Setting and clearing popframe_condition

   // All of these enumerated values are bits. popframe_pending

   // indicates that a PopFrame() has been requested and not yet been

   // completed. popframe_processing indicates that that PopFrame() is in

   // the process of being completed. popframe_force_deopt_reexecution_bit

   // indicates that special handling is required when returning to a

   // deoptimized caller.

   enum PopCondition {

     popframe_inactive                      = 0x00,

     popframe_pending_bit                   = 0x01,

     popframe_processing_bit                = 0x02,

     popframe_force_deopt_reexecution_bit   = 0x04

   };

   PopCondition popframe_condition()                   { return (PopCondition) _popframe_condition; }

   void set_popframe_condition(PopCondition c)         { _popframe_condition = c; }

   void set_popframe_condition_bit(PopCondition c)     { _popframe_condition |= c; }

   void clear_popframe_condition()                     { _popframe_condition = popframe_inactive; }

   static ByteSize popframe_condition_offset()         { return byte_offset_of(JavaThread, _popframe_condition); }

   bool has_pending_popframe()                         { return (popframe_condition() & popframe_pending_bit) != 0; }

   bool popframe_forcing_deopt_reexecution()           { return (popframe_condition() & popframe_force_deopt_reexecution_bit) != 0; }

   void clear_popframe_forcing_deopt_reexecution()     { _popframe_condition &= ~popframe_force_deopt_reexecution_bit; }

 #ifdef CC_INTERP

   bool pop_frame_pending(void)                        { return ((_popframe_condition & popframe_pending_bit) != 0); }

   void clr_pop_frame_pending(void)                    { _popframe_condition = popframe_inactive; }

   bool pop_frame_in_process(void)                     { return ((_popframe_condition & popframe_processing_bit) != 0); }

   void set_pop_frame_in_process(void)                 { _popframe_condition |= popframe_processing_bit; }

   void clr_pop_frame_in_process(void)                 { _popframe_condition &= ~popframe_processing_bit; }

 #endif

  private:

   // Saved incoming arguments to popped frame.

   // Used only when popped interpreted frame returns to deoptimized frame.

   void*    _popframe_preserved_args;

   int      _popframe_preserved_args_size;

  public:

   void  popframe_preserve_args(ByteSize size_in_bytes, void* start);

   void* popframe_preserved_args();

   ByteSize popframe_preserved_args_size();

   WordSize popframe_preserved_args_size_in_words();

   void  popframe_free_preserved_args();

  private:

   JvmtiThreadState *_jvmti_thread_state;

   JvmtiGetLoadedClassesClosure* _jvmti_get_loaded_classes_closure;

   // Used by the interpreter in fullspeed mode for frame pop, method

   // entry, method exit and single stepping support. This field is

   // only set to non-zero by the VM_EnterInterpOnlyMode VM operation.

   // It can be set to zero asynchronously (i.e., without a VM operation

   // or a lock) so we have to be very careful.

   int               _interp_only_mode;

  public:

   // used by the interpreter for fullspeed debugging support (see above)

   static ByteSize interp_only_mode_offset() { return byte_offset_of(JavaThread, _interp_only_mode); }

   bool is_interp_only_mode()                { return (_interp_only_mode != 0); }

   int get_interp_only_mode()                { return _interp_only_mode; }

   void increment_interp_only_mode()         { ++_interp_only_mode; }

   void decrement_interp_only_mode()         { --_interp_only_mode; }

   // support for cached flag that indicates whether exceptions need to be posted for this thread

   // if this is false, we can avoid deoptimizing when events are thrown

   // this gets set to reflect whether jvmtiExport::post_exception_throw would actually do anything

  private:

   int    _should_post_on_exceptions_flag;

  public:

   int   should_post_on_exceptions_flag()  { return _should_post_on_exceptions_flag; }

   void  set_should_post_on_exceptions_flag(int val)  { _should_post_on_exceptions_flag = val; }

  private:

   ThreadStatistics *_thread_stat;

  public:

   ThreadStatistics* get_thread_stat() const    { return _thread_stat; }

   // Return a blocker object for which this thread is blocked parking.

   oop current_park_blocker();

  private:

   static size_t _stack_size_at_create;

  public:

   static inline size_t stack_size_at_create(void) {

     return _stack_size_at_create;

   }

   static inline void set_stack_size_at_create(size_t value) {

     _stack_size_at_create = value;

   }

 #ifndef SERIALGC

   // SATB marking queue support

   ObjPtrQueue& satb_mark_queue() { return _satb_mark_queue; }

   static SATBMarkQueueSet& satb_mark_queue_set() {

     return _satb_mark_queue_set;

   }

   // Dirty card queue support

   DirtyCardQueue& dirty_card_queue() { return _dirty_card_queue; }

   static DirtyCardQueueSet& dirty_card_queue_set() {

     return _dirty_card_queue_set;

   }

 #endif // !SERIALGC

   // This method initializes the SATB and dirty card queues before a

   // JavaThread is added to the Java thread list. Right now, we don't

   // have to do anything to the dirty card queue (it should have been

   // activated when the thread was created), but we have to activate

   // the SATB queue if the thread is created while a marking cycle is

   // in progress. The activation / de-activation of the SATB queues at

   // the beginning / end of a marking cycle is done during safepoints

   // so we have to make sure this method is called outside one to be

   // able to safely read the active field of the SATB queue set. Right

   // now, it is called just before the thread is added to the Java

   // thread list in the Threads::add() method. That method is holding

   // the Threads_lock which ensures we are outside a safepoint. We

   // cannot do the obvious and set the active field of the SATB queue

   // when the thread is created given that, in some cases, safepoints

   // might happen between the JavaThread constructor being called and the

   // thread being added to the Java thread list (an example of this is

   // when the structure for the DestroyJavaVM thread is created).

 #ifndef SERIALGC

   void initialize_queues();

 #else // !SERIALGC

   void initialize_queues() { }

 #endif // !SERIALGC

   // Machine dependent stuff

 #ifdef TARGET_OS_ARCH_linux_x86

 # include "thread_linux_x86.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_linux_sparc

 # include "thread_linux_sparc.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_linux_zero

 # include "thread_linux_zero.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_solaris_x86

 # include "thread_solaris_x86.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_solaris_sparc

 # include "thread_solaris_sparc.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_windows_x86

 # include "thread_windows_x86.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_linux_arm

 # include "thread_linux_arm.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_linux_ppc

 # include "thread_linux_ppc.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_bsd_x86

 # include "thread_bsd_x86.hpp"

 #endif

 #ifdef TARGET_OS_ARCH_bsd_zero

 # include "thread_bsd_zero.hpp"

 #endif

  public:

   void set_blocked_on_compilation(bool value) {

     _blocked_on_compilation = value;

   }

   bool blocked_on_compilation() {

     return _blocked_on_compilation;

   }

  protected:

   bool         _blocked_on_compilation;

   // JSR166 per-thread parker

 private:

   Parker*    _parker;

 public:

   Parker*     parker() { return _parker; }

   // Biased locking support

 private:

   GrowableArray<MonitorInfo*>* _cached_monitor_info;

 public:

   GrowableArray<MonitorInfo*>* cached_monitor_info() { return _cached_monitor_info; }

   void set_cached_monitor_info(GrowableArray<MonitorInfo*>* info) { _cached_monitor_info = info; }

   // clearing/querying jni attach status

   bool is_attaching_via_jni() const { return _jni_attach_state == _attaching_via_jni; }

   bool has_attached_via_jni() const { return is_attaching_via_jni() || _jni_attach_state == _attached_via_jni; }

   void set_done_attaching_via_jni() { _jni_attach_state = _attached_via_jni; OrderAccess::fence(); }

 private:

   // This field is used to determine if a thread has claimed

   // a par_id: it is -1 if the thread has not claimed a par_id;

   // otherwise its value is the par_id that has been claimed.

   int _claimed_par_id;

 public:

   int get_claimed_par_id() { return _claimed_par_id; }

   void set_claimed_par_id(int id) { _claimed_par_id = id;}

 };

 // Inline implementation of JavaThread::current

 inline JavaThread* JavaThread::current() {

   Thread* thread = ThreadLocalStorage::thread();

   assert(thread != NULL && thread->is_Java_thread(), "just checking");

   return (JavaThread*)thread;

 }

 inline CompilerThread* JavaThread::as_CompilerThread() {

   assert(is_Compiler_thread(), "just checking");

   return (CompilerThread*)this;

 }

 inline bool JavaThread::stack_yellow_zone_disabled() {

   return _stack_guard_state == stack_guard_yellow_disabled;

 }

 inline bool JavaThread::stack_yellow_zone_enabled() {

 #ifdef ASSERT

   if (os::uses_stack_guard_pages()) {

     assert(_stack_guard_state != stack_guard_unused, "guard pages must be in use");

   }

 #endif

     return _stack_guard_state == stack_guard_enabled;

 }

 inline size_t JavaThread::stack_available(address cur_sp) {

   // This code assumes java stacks grow down

   address low_addr; // Limit on the address for deepest stack depth

   if ( _stack_guard_state == stack_guard_unused) {

     low_addr =  stack_base() - stack_size();

   } else {

     low_addr = stack_yellow_zone_base();

   }

   return cur_sp > low_addr ? cur_sp - low_addr : 0;

 }

 // A thread used for Compilation.

 class CompilerThread : public JavaThread {

   friend class VMStructs;

  private:

   CompilerCounters* _counters;

   ciEnv*        _env;

   CompileLog*   _log;

   CompileTask*  _task;

   CompileQueue* _queue;

   BufferBlob*   _buffer_blob;

   nmethod*      _scanned_nmethod;  // nmethod being scanned by the sweeper

  public:

   static CompilerThread* current();

   CompilerThread(CompileQueue* queue, CompilerCounters* counters);

   bool is_Compiler_thread() const                { return true; }

   // Hide this compiler thread from external view.

   bool is_hidden_from_external_view() const      { return true; }

   CompileQueue* queue()                          { return _queue; }

   CompilerCounters* counters()                   { return _counters; }

   // Get/set the thread's compilation environment.

   ciEnv*        env()                            { return _env; }

   void          set_env(ciEnv* env)              { _env = env; }

   BufferBlob*   get_buffer_blob()                { return _buffer_blob; }

   void          set_buffer_blob(BufferBlob* b)   { _buffer_blob = b; };

   // Get/set the thread's logging information

   CompileLog*   log()                            { return _log; }

   void          init_log(CompileLog* log) {

     // Set once, for good.

     assert(_log == NULL, "set only once");

     _log = log;

   }

   // GC support

   // Apply "f->do_oop" to all root oops in "this".

   // Apply "cf->do_code_blob" (if !NULL) to all code blobs active in frames

   void oops_do(OopClosure* f, CodeBlobClosure* cf);

 #ifndef PRODUCT

 private:

   IdealGraphPrinter *_ideal_graph_printer;

 public:

   IdealGraphPrinter *ideal_graph_printer()                       { return _ideal_graph_printer; }

   void set_ideal_graph_printer(IdealGraphPrinter *n)             { _ideal_graph_printer = n; }

 #endif

   // Get/set the thread's current task

   CompileTask*  task()                           { return _task; }

   void          set_task(CompileTask* task)      { _task = task; }

   // Track the nmethod currently being scanned by the sweeper

   void          set_scanned_nmethod(nmethod* nm) {

     assert(_scanned_nmethod == NULL || nm == NULL, "should reset to NULL before writing a new value");

     _scanned_nmethod = nm;

   }

 };

 inline CompilerThread* CompilerThread::current() {

   return JavaThread::current()->as_CompilerThread();

 }

 // The active thread queue. It also keeps track of the current used

 // thread priorities.

 class Threads: AllStatic {

   friend class VMStructs;

  private:

   static JavaThread* _thread_list;

   static int         _number_of_threads;

   static int         _number_of_non_daemon_threads;

   static int         _return_code;

  public:

   // Thread management

   // force_daemon is a concession to JNI, where we may need to add a

   // thread to the thread list before allocating its thread object

   static void add(JavaThread* p, bool force_daemon = false);

   static void remove(JavaThread* p);

   static bool includes(JavaThread* p);

   static JavaThread* first()                     { return _thread_list; }

   static void threads_do(ThreadClosure* tc);

   // Initializes the vm and creates the vm thread

   static jint create_vm(JavaVMInitArgs* args, bool* canTryAgain);

   static void convert_vm_init_libraries_to_agents();

   static void create_vm_init_libraries();

   static void create_vm_init_agents();

   static void shutdown_vm_agents();

   static bool destroy_vm();

   // Supported VM versions via JNI

   // Includes JNI_VERSION_1_1

   static jboolean is_supported_jni_version_including_1_1(jint version);

   // Does not include JNI_VERSION_1_1

   static jboolean is_supported_jni_version(jint version);

   // Garbage collection

   static void follow_other_roots(void f(oop*));

   // Apply "f->do_oop" to all root oops in all threads.

   // This version may only be called by sequential code.

   static void oops_do(OopClosure* f, CodeBlobClosure* cf);

   // This version may be called by sequential or parallel code.

   static void possibly_parallel_oops_do(OopClosure* f, CodeBlobClosure* cf);

   // This creates a list of GCTasks, one per thread.

   static void create_thread_roots_tasks(GCTaskQueue* q);

   // This creates a list of GCTasks, one per thread, for marking objects.

   static void create_thread_roots_marking_tasks(GCTaskQueue* q);

   // Apply "f->do_oop" to roots in all threads that

   // are part of compiled frames

   static void compiled_frame_oops_do(OopClosure* f, CodeBlobClosure* cf);

   static void convert_hcode_pointers();

   static void restore_hcode_pointers();

   // Sweeper

   static void nmethods_do(CodeBlobClosure* cf);

   static void gc_epilogue();

   static void gc_prologue();

   // Verification

   static void verify();

   static void print_on(outputStream* st, bool print_stacks, bool internal_format, bool print_concurrent_locks);

   static void print(bool print_stacks, bool internal_format) {

     // this function is only used by debug.cpp

     print_on(tty, print_stacks, internal_format, false /* no concurrent lock printed */);

   }

   static void print_on_error(outputStream* st, Thread* current, char* buf, int buflen);

   // Get Java threads that are waiting to enter a monitor. If doLock

   // is true, then Threads_lock is grabbed as needed. Otherwise, the

   // VM needs to be at a safepoint.

   static GrowableArray<JavaThread*>* get_pending_threads(int count,

     address monitor, bool doLock);

   // Get owning Java thread from the monitor's owner field. If doLock

   // is true, then Threads_lock is grabbed as needed. Otherwise, the

   // VM needs to be at a safepoint.

   static JavaThread *owning_thread_from_monitor_owner(address owner,

     bool doLock);

   // Number of threads on the active threads list

   static int number_of_threads()                 { return _number_of_threads; }

   // Number of non-daemon threads on the active threads list

   static int number_of_non_daemon_threads()      { return _number_of_non_daemon_threads; }

   // Deoptimizes all frames tied to marked nmethods

   static void deoptimized_wrt_marked_nmethods();

 };

 // Thread iterator

 class ThreadClosure: public StackObj {

  public:

   virtual void do_thread(Thread* thread) = 0;

 };

 class SignalHandlerMark: public StackObj {

 private:

   Thread* _thread;

 public:

   SignalHandlerMark(Thread* t) {

     _thread = t;

     if (_thread) _thread->enter_signal_handler();

   }

   ~SignalHandlerMark() {

     if (_thread) _thread->leave_signal_handler();

     _thread = NULL;

   }

 };

 #endif // SHARE_VM_RUNTIME_THREAD_HPP