1 /*
   2  * Copyright 1997-2009 Sun Microsystems, Inc.  All Rights Reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  20  * CA 95054 USA or visit www.sun.com if you need additional information or
  21  * have any questions.
  22  *
  23  */
  24 
  25 class ThreadSafepointState;
  26 class ThreadProfiler;
  27 
  28 class JvmtiThreadState;
  29 class JvmtiGetLoadedClassesClosure;
  30 class ThreadStatistics;
  31 class ConcurrentLocksDump;
  32 class ParkEvent ;
  33 
  34 class ciEnv;
  35 class CompileThread;
  36 class CompileLog;
  37 class CompileTask;
  38 class CompileQueue;
  39 class CompilerCounters;
  40 class vframeArray;
  41 
  42 class DeoptResourceMark;
  43 class jvmtiDeferredLocalVariableSet;
  44 
  45 class GCTaskQueue;
  46 class ThreadClosure;
  47 class IdealGraphPrinter;
  48 
  49 // Class hierarchy
  50 // - Thread
  51 //   - VMThread
  52 //   - JavaThread
  53 //   - WatcherThread
  54 
  55 class Thread: public ThreadShadow {
  56   friend class VMStructs;
  57  private:
  58   // Exception handling
  59   // (Note: _pending_exception and friends are in ThreadShadow)
  60   //oop       _pending_exception;                // pending exception for current thread
  61   // const char* _exception_file;                   // file information for exception (debugging only)
  62   // int         _exception_line;                   // line information for exception (debugging only)
  63 
  64   // Support for forcing alignment of thread objects for biased locking
  65   void*       _real_malloc_address;
  66  public:
  67   void* operator new(size_t size);
  68   void  operator delete(void* p);
  69  private:
  70 
  71   // ***************************************************************
  72   // Suspend and resume support
  73   // ***************************************************************
  74   //
  75   // VM suspend/resume no longer exists - it was once used for various
  76   // things including safepoints but was deprecated and finally removed
  77   // in Java 7. Because VM suspension was considered "internal" Java-level
  78   // suspension was considered "external", and this legacy naming scheme
  79   // remains.
  80   //
  81   // External suspend/resume requests come from JVM_SuspendThread,
  82   // JVM_ResumeThread, JVMTI SuspendThread, and finally JVMTI
  83   // ResumeThread. External
  84   // suspend requests cause _external_suspend to be set and external
  85   // resume requests cause _external_suspend to be cleared.
  86   // External suspend requests do not nest on top of other external
  87   // suspend requests. The higher level APIs reject suspend requests
  88   // for already suspended threads.
  89   //
  90   // The external_suspend
  91   // flag is checked by has_special_runtime_exit_condition() and java thread
  92   // will self-suspend when handle_special_runtime_exit_condition() is
  93   // called. Most uses of the _thread_blocked state in JavaThreads are
  94   // considered the same as being externally suspended; if the blocking
  95   // condition lifts, the JavaThread will self-suspend. Other places
  96   // where VM checks for external_suspend include:
  97   //   + mutex granting (do not enter monitors when thread is suspended)
  98   //   + state transitions from _thread_in_native
  99   //
 100   // In general, java_suspend() does not wait for an external suspend
 101   // request to complete. When it returns, the only guarantee is that
 102   // the _external_suspend field is true.
 103   //
 104   // wait_for_ext_suspend_completion() is used to wait for an external
 105   // suspend request to complete. External suspend requests are usually
 106   // followed by some other interface call that requires the thread to
 107   // be quiescent, e.g., GetCallTrace(). By moving the "wait time" into
 108   // the interface that requires quiescence, we give the JavaThread a
 109   // chance to self-suspend before we need it to be quiescent. This
 110   // improves overall suspend/query performance.
 111   //
 112   // _suspend_flags controls the behavior of java_ suspend/resume.
 113   // It must be set under the protection of SR_lock. Read from the flag is
 114   // OK without SR_lock as long as the value is only used as a hint.
 115   // (e.g., check _external_suspend first without lock and then recheck
 116   // inside SR_lock and finish the suspension)
 117   //
 118   // _suspend_flags is also overloaded for other "special conditions" so
 119   // that a single check indicates whether any special action is needed
 120   // eg. for async exceptions.
 121   // -------------------------------------------------------------------
 122   // Notes:
 123   // 1. The suspend/resume logic no longer uses ThreadState in OSThread
 124   // but we still update its value to keep other part of the system (mainly
 125   // JVMTI) happy. ThreadState is legacy code (see notes in
 126   // osThread.hpp).
 127   //
 128   // 2. It would be more natural if set_external_suspend() is private and
 129   // part of java_suspend(), but that probably would affect the suspend/query
 130   // performance. Need more investigation on this.
 131   //
 132 
 133   // suspend/resume lock: used for self-suspend
 134   Monitor*    _SR_lock;
 135 
 136  protected:
 137   enum SuspendFlags {
 138     // NOTE: avoid using the sign-bit as cc generates different test code
 139     //       when the sign-bit is used, and sometimes incorrectly - see CR 6398077
 140 
 141     _external_suspend       = 0x20000000U, // thread is asked to self suspend
 142     _ext_suspended          = 0x40000000U, // thread has self-suspended
 143     _deopt_suspend          = 0x10000000U, // thread needs to self suspend for deopt
 144 
 145     _has_async_exception    = 0x00000001U  // there is a pending async exception
 146   };
 147 
 148   // various suspension related flags - atomically updated
 149   // overloaded for async exception checking in check_special_condition_for_native_trans.
 150   volatile uint32_t _suspend_flags;
 151 
 152  private:
 153   int _num_nested_signal;
 154 
 155  public:
 156   void enter_signal_handler() { _num_nested_signal++; }
 157   void leave_signal_handler() { _num_nested_signal--; }
 158   bool is_inside_signal_handler() const  { return _num_nested_signal > 0; }
 159 
 160  private:
 161   // Debug tracing
 162   static void trace(const char* msg, const Thread* const thread) PRODUCT_RETURN;
 163 
 164   // Active_handles points to a block of handles
 165   JNIHandleBlock* _active_handles;
 166 
 167   // One-element thread local free list
 168   JNIHandleBlock* _free_handle_block;
 169 
 170   // Point to the last handle mark
 171   HandleMark* _last_handle_mark;
 172 
 173   // The parity of the last strong_roots iteration in which this thread was
 174   // claimed as a task.
 175   jint _oops_do_parity;
 176 
 177   public:
 178    void set_last_handle_mark(HandleMark* mark)   { _last_handle_mark = mark; }
 179     HandleMark* last_handle_mark() const          { return _last_handle_mark; }
 180   private:
 181 
 182   // debug support for checking if code does allow safepoints or not
 183   // GC points in the VM can happen because of allocation, invoking a VM operation, or blocking on
 184   // mutex, or blocking on an object synchronizer (Java locking).
 185   // If !allow_safepoint(), then an assertion failure will happen in any of the above cases
 186   // If !allow_allocation(), then an assertion failure will happen during allocation
 187   // (Hence, !allow_safepoint() => !allow_allocation()).
 188   //
 189   // The two classes No_Safepoint_Verifier and No_Allocation_Verifier are used to set these counters.
 190   //
 191   NOT_PRODUCT(int _allow_safepoint_count;)       // If 0, thread allow a safepoint to happen
 192   debug_only (int _allow_allocation_count;)      // If 0, the thread is allowed to allocate oops.
 193 
 194   // Used by SkipGCALot class.
 195   NOT_PRODUCT(bool _skip_gcalot;)                // Should we elide gc-a-lot?
 196 
 197   // Record when GC is locked out via the GC_locker mechanism
 198   CHECK_UNHANDLED_OOPS_ONLY(int _gc_locked_out_count;)
 199 
 200   friend class No_Alloc_Verifier;
 201   friend class No_Safepoint_Verifier;
 202   friend class Pause_No_Safepoint_Verifier;
 203   friend class ThreadLocalStorage;
 204   friend class GC_locker;
 205 
 206   ThreadLocalAllocBuffer _tlab;                  // Thread-local eden
 207 
 208   int   _vm_operation_started_count;             // VM_Operation support
 209   int   _vm_operation_completed_count;           // VM_Operation support
 210 
 211   ObjectMonitor* _current_pending_monitor;       // ObjectMonitor this thread
 212                                                  // is waiting to lock
 213   bool _current_pending_monitor_is_from_java;    // locking is from Java code
 214 
 215   // ObjectMonitor on which this thread called Object.wait()
 216   ObjectMonitor* _current_waiting_monitor;
 217 
 218   // Private thread-local objectmonitor list - a simple cache organized as a SLL.
 219  public:
 220   ObjectMonitor * omFreeList ;
 221   int omFreeCount ;                             // length of omFreeList
 222   int omFreeProvision ;                         // reload chunk size
 223 
 224  public:
 225   enum {
 226     is_definitely_current_thread = true
 227   };
 228 
 229   // Constructor
 230   Thread();
 231   virtual ~Thread();
 232 
 233   // initializtion
 234   void initialize_thread_local_storage();
 235 
 236   // thread entry point
 237   virtual void run();
 238 
 239   // Testers
 240   virtual bool is_VM_thread()       const            { return false; }
 241   virtual bool is_Java_thread()     const            { return false; }
 242   // Remove this ifdef when C1 is ported to the compiler interface.
 243   virtual bool is_Compiler_thread() const            { return false; }
 244   virtual bool is_hidden_from_external_view() const  { return false; }
 245   virtual bool is_jvmti_agent_thread() const         { return false; }
 246   // True iff the thread can perform GC operations at a safepoint.
 247   // Generally will be true only of VM thread and parallel GC WorkGang
 248   // threads.
 249   virtual bool is_GC_task_thread() const             { return false; }
 250   virtual bool is_Watcher_thread() const             { return false; }
 251   virtual bool is_ConcurrentGC_thread() const        { return false; }
 252 
 253   virtual char* name() const { return (char*)"Unknown thread"; }
 254 
 255   // Returns the current thread
 256   static inline Thread* current();
 257 
 258   // Common thread operations
 259   static void set_priority(Thread* thread, ThreadPriority priority);
 260   static ThreadPriority get_priority(const Thread* const thread);
 261   static void start(Thread* thread);
 262   static void interrupt(Thread* thr);
 263   static bool is_interrupted(Thread* thr, bool clear_interrupted);
 264 
 265   Monitor* SR_lock() const                       { return _SR_lock; }
 266 
 267   bool has_async_exception() const { return (_suspend_flags & _has_async_exception) != 0; }
 268 
 269   void set_suspend_flag(SuspendFlags f) {
 270     assert(sizeof(jint) == sizeof(_suspend_flags), "size mismatch");
 271     uint32_t flags;
 272     do {
 273       flags = _suspend_flags;
 274     }
 275     while (Atomic::cmpxchg((jint)(flags | f),
 276                            (volatile jint*)&_suspend_flags,
 277                            (jint)flags) != (jint)flags);
 278   }
 279   void clear_suspend_flag(SuspendFlags f) {
 280     assert(sizeof(jint) == sizeof(_suspend_flags), "size mismatch");
 281     uint32_t flags;
 282     do {
 283       flags = _suspend_flags;
 284     }
 285     while (Atomic::cmpxchg((jint)(flags & ~f),
 286                            (volatile jint*)&_suspend_flags,
 287                            (jint)flags) != (jint)flags);
 288   }
 289 
 290   void set_has_async_exception() {
 291     set_suspend_flag(_has_async_exception);
 292   }
 293   void clear_has_async_exception() {
 294     clear_suspend_flag(_has_async_exception);
 295   }
 296 
 297   // Support for Unhandled Oop detection
 298 #ifdef CHECK_UNHANDLED_OOPS
 299  private:
 300   UnhandledOops *_unhandled_oops;
 301  public:
 302   UnhandledOops* unhandled_oops()               { return _unhandled_oops; }
 303   // Mark oop safe for gc.  It may be stack allocated but won't move.
 304   void allow_unhandled_oop(oop *op)              {
 305     if (CheckUnhandledOops) unhandled_oops()->allow_unhandled_oop(op);
 306   }
 307   // Clear oops at safepoint so crashes point to unhandled oop violator
 308   void clear_unhandled_oops()                   {
 309     if (CheckUnhandledOops) unhandled_oops()->clear_unhandled_oops();
 310   }
 311   bool is_gc_locked_out() { return _gc_locked_out_count > 0; }
 312 #endif // CHECK_UNHANDLED_OOPS
 313 
 314 #ifndef PRODUCT
 315   bool skip_gcalot()           { return _skip_gcalot; }
 316   void set_skip_gcalot(bool v) { _skip_gcalot = v;    }
 317 #endif
 318 
 319  public:
 320   // Installs a pending exception to be inserted later
 321   static void send_async_exception(oop thread_oop, oop java_throwable);
 322 
 323   // Resource area
 324   ResourceArea* resource_area() const            { return _resource_area; }
 325   void set_resource_area(ResourceArea* area)     { _resource_area = area; }
 326 
 327   OSThread* osthread() const                     { return _osthread;   }
 328   void set_osthread(OSThread* thread)            { _osthread = thread; }
 329 
 330   // JNI handle support
 331   JNIHandleBlock* active_handles() const         { return _active_handles; }
 332   void set_active_handles(JNIHandleBlock* block) { _active_handles = block; }
 333   JNIHandleBlock* free_handle_block() const      { return _free_handle_block; }
 334   void set_free_handle_block(JNIHandleBlock* block) { _free_handle_block = block; }
 335 
 336   // Internal handle support
 337   HandleArea* handle_area() const                { return _handle_area; }
 338   void set_handle_area(HandleArea* area)         { _handle_area = area; }
 339 
 340   // Thread-Local Allocation Buffer (TLAB) support
 341   ThreadLocalAllocBuffer& tlab()                 { return _tlab; }
 342   void initialize_tlab() {
 343     if (UseTLAB) {
 344       tlab().initialize();
 345     }
 346   }
 347 
 348   // VM operation support
 349   int vm_operation_ticket()                      { return ++_vm_operation_started_count; }
 350   int vm_operation_completed_count()             { return _vm_operation_completed_count; }
 351   void increment_vm_operation_completed_count()  { _vm_operation_completed_count++; }
 352 
 353   // For tracking the heavyweight monitor the thread is pending on.
 354   ObjectMonitor* current_pending_monitor() {
 355     return _current_pending_monitor;
 356   }
 357   void set_current_pending_monitor(ObjectMonitor* monitor) {
 358     _current_pending_monitor = monitor;
 359   }
 360   void set_current_pending_monitor_is_from_java(bool from_java) {
 361     _current_pending_monitor_is_from_java = from_java;
 362   }
 363   bool current_pending_monitor_is_from_java() {
 364     return _current_pending_monitor_is_from_java;
 365   }
 366 
 367   // For tracking the ObjectMonitor on which this thread called Object.wait()
 368   ObjectMonitor* current_waiting_monitor() {
 369     return _current_waiting_monitor;
 370   }
 371   void set_current_waiting_monitor(ObjectMonitor* monitor) {
 372     _current_waiting_monitor = monitor;
 373   }
 374 
 375   // GC support
 376   // Apply "f->do_oop" to all root oops in "this".
 377   // Apply "cf->do_code_blob" (if !NULL) to all code blobs active in frames
 378   void oops_do(OopClosure* f, CodeBlobClosure* cf);
 379 
 380   // Handles the parallel case for the method below.
 381 private:
 382   bool claim_oops_do_par_case(int collection_parity);
 383 public:
 384   // Requires that "collection_parity" is that of the current strong roots
 385   // iteration.  If "is_par" is false, sets the parity of "this" to
 386   // "collection_parity", and returns "true".  If "is_par" is true,
 387   // uses an atomic instruction to set the current threads parity to
 388   // "collection_parity", if it is not already.  Returns "true" iff the
 389   // calling thread does the update, this indicates that the calling thread
 390   // has claimed the thread's stack as a root groop in the current
 391   // collection.
 392   bool claim_oops_do(bool is_par, int collection_parity) {
 393     if (!is_par) {
 394       _oops_do_parity = collection_parity;
 395       return true;
 396     } else {
 397       return claim_oops_do_par_case(collection_parity);
 398     }
 399   }
 400 
 401   // Sweeper support
 402   void nmethods_do(CodeBlobClosure* cf);
 403 
 404   // Tells if adr belong to this thread. This is used
 405   // for checking if a lock is owned by the running thread.
 406 
 407   // Used by fast lock support
 408   virtual bool is_lock_owned(address adr) const;
 409 
 410   // Check if address is in the stack of the thread (not just for locks).
 411   // Warning: the method can only be used on the running thread
 412   bool is_in_stack(address adr) const;
 413 
 414   // Sets this thread as starting thread. Returns failure if thread
 415   // creation fails due to lack of memory, too many threads etc.
 416   bool set_as_starting_thread();
 417 
 418  protected:
 419   // OS data associated with the thread
 420   OSThread* _osthread;  // Platform-specific thread information
 421 
 422   // Thread local resource area for temporary allocation within the VM
 423   ResourceArea* _resource_area;
 424 
 425   // Thread local handle area for allocation of handles within the VM
 426   HandleArea* _handle_area;
 427 
 428   // Support for stack overflow handling, get_thread, etc.
 429   address          _stack_base;
 430   size_t           _stack_size;
 431   uintptr_t        _self_raw_id;      // used by get_thread (mutable)
 432   int              _lgrp_id;
 433 
 434  public:
 435   // Stack overflow support
 436   address stack_base() const           { assert(_stack_base != NULL,"Sanity check"); return _stack_base; }
 437 
 438   void    set_stack_base(address base) { _stack_base = base; }
 439   size_t  stack_size() const           { return _stack_size; }
 440   void    set_stack_size(size_t size)  { _stack_size = size; }
 441   void    record_stack_base_and_size();
 442 
 443   int     lgrp_id() const                 { return _lgrp_id; }
 444   void    set_lgrp_id(int value)          { _lgrp_id = value; }
 445 
 446   // Printing
 447   void print_on(outputStream* st) const;
 448   void print() const { print_on(tty); }
 449   virtual void print_on_error(outputStream* st, char* buf, int buflen) const;
 450 
 451   // Debug-only code
 452 
 453 #ifdef ASSERT
 454  private:
 455   // Deadlock detection support for Mutex locks. List of locks own by thread.
 456   Monitor *_owned_locks;
 457   // Mutex::set_owner_implementation is the only place where _owned_locks is modified,
 458   // thus the friendship
 459   friend class Mutex;
 460   friend class Monitor;
 461 
 462  public:
 463   void print_owned_locks_on(outputStream* st) const;
 464   void print_owned_locks() const                 { print_owned_locks_on(tty);    }
 465   Monitor * owned_locks() const                  { return _owned_locks;          }
 466   bool owns_locks() const                        { return owned_locks() != NULL; }
 467   bool owns_locks_but_compiled_lock() const;
 468 
 469   // Deadlock detection
 470   bool allow_allocation()                        { return _allow_allocation_count == 0; }
 471 #endif
 472 
 473   void check_for_valid_safepoint_state(bool potential_vm_operation) PRODUCT_RETURN;
 474 
 475  private:
 476   volatile int _jvmti_env_iteration_count;
 477 
 478  public:
 479   void entering_jvmti_env_iteration()            { ++_jvmti_env_iteration_count; }
 480   void leaving_jvmti_env_iteration()             { --_jvmti_env_iteration_count; }
 481   bool is_inside_jvmti_env_iteration()           { return _jvmti_env_iteration_count > 0; }
 482 
 483   // Code generation
 484   static ByteSize exception_file_offset()        { return byte_offset_of(Thread, _exception_file   ); }
 485   static ByteSize exception_line_offset()        { return byte_offset_of(Thread, _exception_line   ); }
 486   static ByteSize active_handles_offset()        { return byte_offset_of(Thread, _active_handles   ); }
 487 
 488   static ByteSize stack_base_offset()            { return byte_offset_of(Thread, _stack_base ); }
 489   static ByteSize stack_size_offset()            { return byte_offset_of(Thread, _stack_size ); }
 490   static ByteSize omFreeList_offset()            { return byte_offset_of(Thread, omFreeList); }
 491 
 492 #define TLAB_FIELD_OFFSET(name) \
 493   static ByteSize tlab_##name##_offset()            { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::name##_offset(); }
 494 
 495   TLAB_FIELD_OFFSET(start)
 496   TLAB_FIELD_OFFSET(end)
 497   TLAB_FIELD_OFFSET(top)
 498   TLAB_FIELD_OFFSET(pf_top)
 499   TLAB_FIELD_OFFSET(size)                   // desired_size
 500   TLAB_FIELD_OFFSET(refill_waste_limit)
 501   TLAB_FIELD_OFFSET(number_of_refills)
 502   TLAB_FIELD_OFFSET(fast_refill_waste)
 503   TLAB_FIELD_OFFSET(slow_allocations)
 504 
 505 #undef TLAB_FIELD_OFFSET
 506 
 507  public:
 508   volatile intptr_t _Stalled ;
 509   volatile int _TypeTag ;
 510   ParkEvent * _ParkEvent ;                     // for synchronized()
 511   ParkEvent * _SleepEvent ;                    // for Thread.sleep
 512   ParkEvent * _MutexEvent ;                    // for native internal Mutex/Monitor
 513   ParkEvent * _MuxEvent ;                      // for low-level muxAcquire-muxRelease
 514   int NativeSyncRecursion ;                    // diagnostic
 515 
 516   volatile int _OnTrap ;                       // Resume-at IP delta
 517   jint _hashStateW ;                           // Marsaglia Shift-XOR thread-local RNG
 518   jint _hashStateX ;                           // thread-specific hashCode generator state
 519   jint _hashStateY ;
 520   jint _hashStateZ ;
 521   void * _schedctl ;
 522 
 523   intptr_t _ScratchA, _ScratchB ;              // Scratch locations for fast-path sync code
 524   static ByteSize ScratchA_offset()            { return byte_offset_of(Thread, _ScratchA ); }
 525   static ByteSize ScratchB_offset()            { return byte_offset_of(Thread, _ScratchB ); }
 526 
 527   volatile jint rng [4] ;                      // RNG for spin loop
 528 
 529   // Low-level leaf-lock primitives used to implement synchronization
 530   // and native monitor-mutex infrastructure.
 531   // Not for general synchronization use.
 532   static void SpinAcquire (volatile int * Lock, const char * Name) ;
 533   static void SpinRelease (volatile int * Lock) ;
 534   static void muxAcquire  (volatile intptr_t * Lock, const char * Name) ;
 535   static void muxAcquireW (volatile intptr_t * Lock, ParkEvent * ev) ;
 536   static void muxRelease  (volatile intptr_t * Lock) ;
 537 
 538 };
 539 
 540 // Inline implementation of Thread::current()
 541 // Thread::current is "hot" it's called > 128K times in the 1st 500 msecs of
 542 // startup.
 543 // ThreadLocalStorage::thread is warm -- it's called > 16K times in the same
 544 // period.   This is inlined in thread_<os_family>.inline.hpp.
 545 
 546 inline Thread* Thread::current() {
 547 #ifdef ASSERT
 548 // This function is very high traffic. Define PARANOID to enable expensive
 549 // asserts.
 550 #ifdef PARANOID
 551   // Signal handler should call ThreadLocalStorage::get_thread_slow()
 552   Thread* t = ThreadLocalStorage::get_thread_slow();
 553   assert(t != NULL && !t->is_inside_signal_handler(),
 554          "Don't use Thread::current() inside signal handler");
 555 #endif
 556 #endif
 557   Thread* thread = ThreadLocalStorage::thread();
 558   assert(thread != NULL, "just checking");
 559   return thread;
 560 }
 561 
 562 // Name support for threads.  non-JavaThread subclasses with multiple
 563 // uniquely named instances should derive from this.
 564 class NamedThread: public Thread {
 565   friend class VMStructs;
 566   enum {
 567     max_name_len = 64
 568   };
 569  private:
 570   char* _name;
 571  public:
 572   NamedThread();
 573   ~NamedThread();
 574   // May only be called once per thread.
 575   void set_name(const char* format, ...);
 576   virtual char* name() const { return _name == NULL ? (char*)"Unknown Thread" : _name; }
 577 };
 578 
 579 // Worker threads are named and have an id of an assigned work.
 580 class WorkerThread: public NamedThread {
 581 private:
 582   uint _id;
 583 public:
 584   WorkerThread() : _id(0) { }
 585   void set_id(uint work_id) { _id = work_id; }
 586   uint id() const { return _id; }
 587 };
 588 
 589 // A single WatcherThread is used for simulating timer interrupts.
 590 class WatcherThread: public Thread {
 591   friend class VMStructs;
 592  public:
 593   virtual void run();
 594 
 595  private:
 596   static WatcherThread* _watcher_thread;
 597 
 598   static bool _should_terminate;
 599  public:
 600   enum SomeConstants {
 601     delay_interval = 10                          // interrupt delay in milliseconds
 602   };
 603 
 604   // Constructor
 605   WatcherThread();
 606 
 607   // Tester
 608   bool is_Watcher_thread() const                 { return true; }
 609 
 610   // Printing
 611   char* name() const { return (char*)"VM Periodic Task Thread"; }
 612   void print_on(outputStream* st) const;
 613   void print() const { print_on(tty); }
 614 
 615   // Returns the single instance of WatcherThread
 616   static WatcherThread* watcher_thread()         { return _watcher_thread; }
 617 
 618   // Create and start the single instance of WatcherThread, or stop it on shutdown
 619   static void start();
 620   static void stop();
 621 };
 622 
 623 
 624 class CompilerThread;
 625 
 626 typedef void (*ThreadFunction)(JavaThread*, TRAPS);
 627 
 628 class JavaThread: public Thread {
 629   friend class VMStructs;
 630  private:
 631   JavaThread*    _next;                          // The next thread in the Threads list
 632   oop            _threadObj;                     // The Java level thread object
 633 
 634 #ifdef ASSERT
 635  private:
 636   int _java_call_counter;
 637 
 638  public:
 639   int  java_call_counter()                       { return _java_call_counter; }
 640   void inc_java_call_counter()                   { _java_call_counter++; }
 641   void dec_java_call_counter() {
 642     assert(_java_call_counter > 0, "Invalid nesting of JavaCallWrapper");
 643     _java_call_counter--;
 644   }
 645  private:  // restore original namespace restriction
 646 #endif  // ifdef ASSERT
 647 
 648 #ifndef PRODUCT
 649  public:
 650   enum {
 651     jump_ring_buffer_size = 16
 652   };
 653  private:  // restore original namespace restriction
 654 #endif
 655 
 656   JavaFrameAnchor _anchor;                       // Encapsulation of current java frame and it state
 657 
 658   ThreadFunction _entry_point;
 659 
 660   JNIEnv        _jni_environment;
 661 
 662   // Deopt support
 663   DeoptResourceMark*  _deopt_mark;               // Holds special ResourceMark for deoptimization
 664 
 665   intptr_t*      _must_deopt_id;                 // id of frame that needs to be deopted once we
 666                                                  // transition out of native
 667 
 668   vframeArray*  _vframe_array_head;              // Holds the heap of the active vframeArrays
 669   vframeArray*  _vframe_array_last;              // Holds last vFrameArray we popped
 670   // Because deoptimization is lazy we must save jvmti requests to set locals
 671   // in compiled frames until we deoptimize and we have an interpreter frame.
 672   // This holds the pointer to array (yeah like there might be more than one) of
 673   // description of compiled vframes that have locals that need to be updated.
 674   GrowableArray<jvmtiDeferredLocalVariableSet*>* _deferred_locals_updates;
 675 
 676   // Handshake value for fixing 6243940. We need a place for the i2c
 677   // adapter to store the callee methodOop. This value is NEVER live
 678   // across a gc point so it does NOT have to be gc'd
 679   // The handshake is open ended since we can't be certain that it will
 680   // be NULLed. This is because we rarely ever see the race and end up
 681   // in handle_wrong_method which is the backend of the handshake. See
 682   // code in i2c adapters and handle_wrong_method.
 683 
 684   methodOop     _callee_target;
 685 
 686   // Oop results of VM runtime calls
 687   oop           _vm_result;                      // Used to pass back an oop result into Java code, GC-preserved
 688   oop           _vm_result_2;                    // Used to pass back an oop result into Java code, GC-preserved
 689 
 690   MonitorChunk* _monitor_chunks;                 // Contains the off stack monitors
 691                                                  // allocated during deoptimization
 692                                                  // and by JNI_MonitorEnter/Exit
 693 
 694   // Async. requests support
 695   enum AsyncRequests {
 696     _no_async_condition = 0,
 697     _async_exception,
 698     _async_unsafe_access_error
 699   };
 700   AsyncRequests _special_runtime_exit_condition; // Enum indicating pending async. request
 701   oop           _pending_async_exception;
 702 
 703   // Safepoint support
 704  public:                                         // Expose _thread_state for SafeFetchInt()
 705   volatile JavaThreadState _thread_state;
 706  private:
 707   ThreadSafepointState *_safepoint_state;        // Holds information about a thread during a safepoint
 708   address               _saved_exception_pc;     // Saved pc of instruction where last implicit exception happened
 709 
 710   // JavaThread termination support
 711   enum TerminatedTypes {
 712     _not_terminated = 0xDEAD - 2,
 713     _thread_exiting,                             // JavaThread::exit() has been called for this thread
 714     _thread_terminated,                          // JavaThread is removed from thread list
 715     _vm_exited                                   // JavaThread is still executing native code, but VM is terminated
 716                                                  // only VM_Exit can set _vm_exited
 717   };
 718 
 719   // In general a JavaThread's _terminated field transitions as follows:
 720   //
 721   //   _not_terminated => _thread_exiting => _thread_terminated
 722   //
 723   // _vm_exited is a special value to cover the case of a JavaThread
 724   // executing native code after the VM itself is terminated.
 725   TerminatedTypes       _terminated;
 726   // suspend/resume support
 727   volatile bool         _suspend_equivalent;     // Suspend equivalent condition
 728   jint                  _in_deopt_handler;       // count of deoptimization
 729                                                  // handlers thread is in
 730   volatile bool         _doing_unsafe_access;    // Thread may fault due to unsafe access
 731   bool                  _do_not_unlock_if_synchronized; // Do not unlock the receiver of a synchronized method (since it was
 732                                                  // never locked) when throwing an exception. Used by interpreter only.
 733 
 734   //  Flag to mark a JNI thread in the process of attaching - See CR 6404306
 735   //  This flag is never set true other than at construction, and in that case
 736   //  is shortly thereafter set false
 737   volatile bool _is_attaching;
 738 
 739  public:
 740   // State of the stack guard pages for this thread.
 741   enum StackGuardState {
 742     stack_guard_unused,         // not needed
 743     stack_guard_yellow_disabled,// disabled (temporarily) after stack overflow
 744     stack_guard_enabled         // enabled
 745   };
 746 
 747  private:
 748 
 749   StackGuardState        _stack_guard_state;
 750 
 751   // Compiler exception handling (NOTE: The _exception_oop is *NOT* the same as _pending_exception. It is
 752   // used to temp. parsing values into and out of the runtime system during exception handling for compiled
 753   // code)
 754   volatile oop     _exception_oop;               // Exception thrown in compiled code
 755   volatile address _exception_pc;                // PC where exception happened
 756   volatile address _exception_handler_pc;        // PC for handler of exception
 757   volatile int     _exception_stack_size;        // Size of frame where exception happened
 758 
 759   // support for compilation
 760   bool    _is_compiling;                         // is true if a compilation is active inthis thread (one compilation per thread possible)
 761 
 762   // support for JNI critical regions
 763   jint    _jni_active_critical;                  // count of entries into JNI critical region
 764 
 765   // For deadlock detection.
 766   int _depth_first_number;
 767 
 768   // JVMTI PopFrame support
 769   // This is set to popframe_pending to signal that top Java frame should be popped immediately
 770   int _popframe_condition;
 771 
 772 #ifndef PRODUCT
 773   int _jmp_ring_index;
 774   struct {
 775       // We use intptr_t instead of address so debugger doesn't try and display strings
 776       intptr_t _target;
 777       intptr_t _instruction;
 778       const char*  _file;
 779       int _line;
 780   }   _jmp_ring[ jump_ring_buffer_size ];
 781 #endif /* PRODUCT */
 782 
 783 #ifndef SERIALGC
 784   // Support for G1 barriers
 785 
 786   ObjPtrQueue _satb_mark_queue;          // Thread-local log for SATB barrier.
 787   // Set of all such queues.
 788   static SATBMarkQueueSet _satb_mark_queue_set;
 789 
 790   DirtyCardQueue _dirty_card_queue;      // Thread-local log for dirty cards.
 791   // Set of all such queues.
 792   static DirtyCardQueueSet _dirty_card_queue_set;
 793 
 794   void flush_barrier_queues();
 795 #endif // !SERIALGC
 796 
 797   friend class VMThread;
 798   friend class ThreadWaitTransition;
 799   friend class VM_Exit;
 800 
 801   void initialize();                             // Initialized the instance variables
 802 
 803  public:
 804   // Constructor
 805   JavaThread(bool is_attaching = false); // for main thread and JNI attached threads
 806   JavaThread(ThreadFunction entry_point, size_t stack_size = 0);
 807   ~JavaThread();
 808 
 809 #ifdef ASSERT
 810   // verify this JavaThread hasn't be published in the Threads::list yet
 811   void verify_not_published();
 812 #endif
 813 
 814   //JNI functiontable getter/setter for JVMTI jni function table interception API.
 815   void set_jni_functions(struct JNINativeInterface_* functionTable) {
 816     _jni_environment.functions = functionTable;
 817   }
 818   struct JNINativeInterface_* get_jni_functions() {
 819     return (struct JNINativeInterface_ *)_jni_environment.functions;
 820   }
 821 
 822   // Executes Shutdown.shutdown()
 823   void invoke_shutdown_hooks();
 824 
 825   // Cleanup on thread exit
 826   enum ExitType {
 827     normal_exit,
 828     jni_detach
 829   };
 830   void exit(bool destroy_vm, ExitType exit_type = normal_exit);
 831 
 832   void cleanup_failed_attach_current_thread();
 833 
 834   // Testers
 835   virtual bool is_Java_thread() const            { return true;  }
 836 
 837   // compilation
 838   void set_is_compiling(bool f)                  { _is_compiling = f; }
 839   bool is_compiling() const                      { return _is_compiling; }
 840 
 841   // Thread chain operations
 842   JavaThread* next() const                       { return _next; }
 843   void set_next(JavaThread* p)                   { _next = p; }
 844 
 845   // Thread oop. threadObj() can be NULL for initial JavaThread
 846   // (or for threads attached via JNI)
 847   oop threadObj() const                          { return _threadObj; }
 848   void set_threadObj(oop p)                      { _threadObj = p; }
 849 
 850   ThreadPriority java_priority() const;          // Read from threadObj()
 851 
 852   // Prepare thread and add to priority queue.  If a priority is
 853   // not specified, use the priority of the thread object. Threads_lock
 854   // must be held while this function is called.
 855   void prepare(jobject jni_thread, ThreadPriority prio=NoPriority);
 856 
 857   void set_saved_exception_pc(address pc)        { _saved_exception_pc = pc; }
 858   address saved_exception_pc()                   { return _saved_exception_pc; }
 859 
 860 
 861   ThreadFunction entry_point() const             { return _entry_point; }
 862 
 863   // Allocates a new Java level thread object for this thread. thread_name may be NULL.
 864   void allocate_threadObj(Handle thread_group, char* thread_name, bool daemon, TRAPS);
 865 
 866   // Last frame anchor routines
 867 
 868   JavaFrameAnchor* frame_anchor(void)                { return &_anchor; }
 869 
 870   // last_Java_sp
 871   bool has_last_Java_frame() const                   { return _anchor.has_last_Java_frame(); }
 872   intptr_t* last_Java_sp() const                     { return _anchor.last_Java_sp(); }
 873 
 874   // last_Java_pc
 875 
 876   address last_Java_pc(void)                         { return _anchor.last_Java_pc(); }
 877 
 878   // Safepoint support
 879   JavaThreadState thread_state() const           { return _thread_state; }
 880   void set_thread_state(JavaThreadState s)       { _thread_state=s;      }
 881   ThreadSafepointState *safepoint_state() const  { return _safepoint_state;  }
 882   void set_safepoint_state(ThreadSafepointState *state) { _safepoint_state = state; }
 883   bool is_at_poll_safepoint()                    { return _safepoint_state->is_at_poll_safepoint(); }
 884 
 885   // thread has called JavaThread::exit() or is terminated
 886   bool is_exiting()                              { return _terminated == _thread_exiting || is_terminated(); }
 887   // thread is terminated (no longer on the threads list); we compare
 888   // against the two non-terminated values so that a freed JavaThread
 889   // will also be considered terminated.
 890   bool is_terminated()                           { return _terminated != _not_terminated && _terminated != _thread_exiting; }
 891   void set_terminated(TerminatedTypes t)         { _terminated = t; }
 892   // special for Threads::remove() which is static:
 893   void set_terminated_value()                    { _terminated = _thread_terminated; }
 894   void block_if_vm_exited();
 895 
 896   bool doing_unsafe_access()                     { return _doing_unsafe_access; }
 897   void set_doing_unsafe_access(bool val)         { _doing_unsafe_access = val; }
 898 
 899   bool do_not_unlock_if_synchronized()             { return _do_not_unlock_if_synchronized; }
 900   void set_do_not_unlock_if_synchronized(bool val) { _do_not_unlock_if_synchronized = val; }
 901 
 902 
 903   // Suspend/resume support for JavaThread
 904 
 905  private:
 906   void set_ext_suspended()       { set_suspend_flag (_ext_suspended);  }
 907   void clear_ext_suspended()     { clear_suspend_flag(_ext_suspended); }
 908 
 909  public:
 910   void java_suspend();
 911   void java_resume();
 912   int  java_suspend_self();
 913 
 914   void check_and_wait_while_suspended() {
 915     assert(JavaThread::current() == this, "sanity check");
 916 
 917     bool do_self_suspend;
 918     do {
 919       // were we externally suspended while we were waiting?
 920       do_self_suspend = handle_special_suspend_equivalent_condition();
 921       if (do_self_suspend) {
 922         // don't surprise the thread that suspended us by returning
 923         java_suspend_self();
 924         set_suspend_equivalent();
 925       }
 926     } while (do_self_suspend);
 927   }
 928   static void check_safepoint_and_suspend_for_native_trans(JavaThread *thread);
 929   // Check for async exception in addition to safepoint and suspend request.
 930   static void check_special_condition_for_native_trans(JavaThread *thread);
 931 
 932   bool is_ext_suspend_completed(bool called_by_wait, int delay, uint32_t *bits);
 933   bool is_ext_suspend_completed_with_lock(uint32_t *bits) {
 934     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 935     // Warning: is_ext_suspend_completed() may temporarily drop the
 936     // SR_lock to allow the thread to reach a stable thread state if
 937     // it is currently in a transient thread state.
 938     return is_ext_suspend_completed(false /*!called_by_wait */,
 939                                     SuspendRetryDelay, bits);
 940   }
 941 
 942   // We cannot allow wait_for_ext_suspend_completion() to run forever or
 943   // we could hang. SuspendRetryCount and SuspendRetryDelay are normally
 944   // passed as the count and delay parameters. Experiments with specific
 945   // calls to wait_for_ext_suspend_completion() can be done by passing
 946   // other values in the code. Experiments with all calls can be done
 947   // via the appropriate -XX options.
 948   bool wait_for_ext_suspend_completion(int count, int delay, uint32_t *bits);
 949 
 950   void set_external_suspend()     { set_suspend_flag  (_external_suspend); }
 951   void clear_external_suspend()   { clear_suspend_flag(_external_suspend); }
 952 
 953   void set_deopt_suspend()        { set_suspend_flag  (_deopt_suspend); }
 954   void clear_deopt_suspend()      { clear_suspend_flag(_deopt_suspend); }
 955   bool is_deopt_suspend()         { return (_suspend_flags & _deopt_suspend) != 0; }
 956 
 957   bool is_external_suspend() const {
 958     return (_suspend_flags & _external_suspend) != 0;
 959   }
 960   // Whenever a thread transitions from native to vm/java it must suspend
 961   // if external|deopt suspend is present.
 962   bool is_suspend_after_native() const {
 963     return (_suspend_flags & (_external_suspend | _deopt_suspend) ) != 0;
 964   }
 965 
 966   // external suspend request is completed
 967   bool is_ext_suspended() const {
 968     return (_suspend_flags & _ext_suspended) != 0;
 969   }
 970 
 971   bool is_external_suspend_with_lock() const {
 972     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 973     return is_external_suspend();
 974   }
 975 
 976   // Special method to handle a pending external suspend request
 977   // when a suspend equivalent condition lifts.
 978   bool handle_special_suspend_equivalent_condition() {
 979     assert(is_suspend_equivalent(),
 980       "should only be called in a suspend equivalence condition");
 981     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 982     bool ret = is_external_suspend();
 983     if (!ret) {
 984       // not about to self-suspend so clear suspend equivalence
 985       clear_suspend_equivalent();
 986     }
 987     // implied else:
 988     // We have a pending external suspend request so we leave the
 989     // suspend_equivalent flag set until java_suspend_self() sets
 990     // the ext_suspended flag and clears the suspend_equivalent
 991     // flag. This insures that wait_for_ext_suspend_completion()
 992     // will return consistent values.
 993     return ret;
 994   }
 995 
 996   // utility methods to see if we are doing some kind of suspension
 997   bool is_being_ext_suspended() const            {
 998     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 999     return is_ext_suspended() || is_external_suspend();
1000   }
1001 
1002   bool is_suspend_equivalent() const             { return _suspend_equivalent; }
1003 
1004   void set_suspend_equivalent()                  { _suspend_equivalent = true; };
1005   void clear_suspend_equivalent()                { _suspend_equivalent = false; };
1006 
1007   // Thread.stop support
1008   void send_thread_stop(oop throwable);
1009   AsyncRequests clear_special_runtime_exit_condition() {
1010     AsyncRequests x = _special_runtime_exit_condition;
1011     _special_runtime_exit_condition = _no_async_condition;
1012     return x;
1013   }
1014 
1015   // Are any async conditions present?
1016   bool has_async_condition() { return (_special_runtime_exit_condition != _no_async_condition); }
1017 
1018   void check_and_handle_async_exceptions(bool check_unsafe_error = true);
1019 
1020   // these next two are also used for self-suspension and async exception support
1021   void handle_special_runtime_exit_condition(bool check_asyncs = true);
1022 
1023   // Return true if JavaThread has an asynchronous condition or
1024   // if external suspension is requested.
1025   bool has_special_runtime_exit_condition() {
1026     // We call is_external_suspend() last since external suspend should
1027     // be less common. Because we don't use is_external_suspend_with_lock
1028     // it is possible that we won't see an asynchronous external suspend
1029     // request that has just gotten started, i.e., SR_lock grabbed but
1030     // _external_suspend field change either not made yet or not visible
1031     // yet. However, this is okay because the request is asynchronous and
1032     // we will see the new flag value the next time through. It's also
1033     // possible that the external suspend request is dropped after
1034     // we have checked is_external_suspend(), we will recheck its value
1035     // under SR_lock in java_suspend_self().
1036     return (_special_runtime_exit_condition != _no_async_condition) ||
1037             is_external_suspend() || is_deopt_suspend();
1038   }
1039 
1040   void set_pending_unsafe_access_error()          { _special_runtime_exit_condition = _async_unsafe_access_error; }
1041 
1042   void set_pending_async_exception(oop e) {
1043     _pending_async_exception = e;
1044     _special_runtime_exit_condition = _async_exception;
1045     set_has_async_exception();
1046   }
1047 
1048   // Fast-locking support
1049   bool is_lock_owned(address adr) const;
1050 
1051   // Accessors for vframe array top
1052   // The linked list of vframe arrays are sorted on sp. This means when we
1053   // unpack the head must contain the vframe array to unpack.
1054   void set_vframe_array_head(vframeArray* value) { _vframe_array_head = value; }
1055   vframeArray* vframe_array_head() const         { return _vframe_array_head;  }
1056 
1057   // Side structure for defering update of java frame locals until deopt occurs
1058   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred_locals() const { return _deferred_locals_updates; }
1059   void set_deferred_locals(GrowableArray<jvmtiDeferredLocalVariableSet *>* vf) { _deferred_locals_updates = vf; }
1060 
1061   // These only really exist to make debugging deopt problems simpler
1062 
1063   void set_vframe_array_last(vframeArray* value) { _vframe_array_last = value; }
1064   vframeArray* vframe_array_last() const         { return _vframe_array_last;  }
1065 
1066   // The special resourceMark used during deoptimization
1067 
1068   void set_deopt_mark(DeoptResourceMark* value)  { _deopt_mark = value; }
1069   DeoptResourceMark* deopt_mark(void)            { return _deopt_mark; }
1070 
1071   intptr_t* must_deopt_id()                      { return _must_deopt_id; }
1072   void     set_must_deopt_id(intptr_t* id)       { _must_deopt_id = id; }
1073   void     clear_must_deopt_id()                 { _must_deopt_id = NULL; }
1074 
1075   methodOop  callee_target() const               { return _callee_target; }
1076   void set_callee_target  (methodOop x)          { _callee_target   = x; }
1077 
1078   // Oop results of vm runtime calls
1079   oop  vm_result() const                         { return _vm_result; }
1080   void set_vm_result  (oop x)                    { _vm_result   = x; }
1081 
1082   oop  vm_result_2() const                       { return _vm_result_2; }
1083   void set_vm_result_2  (oop x)                  { _vm_result_2   = x; }
1084 
1085   // Exception handling for compiled methods
1086   oop      exception_oop() const                 { return _exception_oop; }
1087   int      exception_stack_size() const          { return _exception_stack_size; }
1088   address  exception_pc() const                  { return _exception_pc; }
1089   address  exception_handler_pc() const          { return _exception_handler_pc; }
1090 
1091   void set_exception_oop(oop o)                  { _exception_oop = o; }
1092   void set_exception_pc(address a)               { _exception_pc = a; }
1093   void set_exception_handler_pc(address a)       { _exception_handler_pc = a; }
1094   void set_exception_stack_size(int size)        { _exception_stack_size = size; }
1095 
1096   // Stack overflow support
1097   inline size_t stack_available(address cur_sp);
1098   address stack_yellow_zone_base()
1099     { return (address)(stack_base() - (stack_size() - (stack_red_zone_size() + stack_yellow_zone_size()))); }
1100   size_t  stack_yellow_zone_size()
1101     { return StackYellowPages * os::vm_page_size(); }
1102   address stack_red_zone_base()
1103     { return (address)(stack_base() - (stack_size() - stack_red_zone_size())); }
1104   size_t stack_red_zone_size()
1105     { return StackRedPages * os::vm_page_size(); }
1106   bool in_stack_yellow_zone(address a)
1107     { return (a <= stack_yellow_zone_base()) && (a >= stack_red_zone_base()); }
1108   bool in_stack_red_zone(address a)
1109     { return (a <= stack_red_zone_base()) && (a >= (address)((intptr_t)stack_base() - stack_size())); }
1110 
1111   void create_stack_guard_pages();
1112   void remove_stack_guard_pages();
1113 
1114   void enable_stack_yellow_zone();
1115   void disable_stack_yellow_zone();
1116   void enable_stack_red_zone();
1117   void disable_stack_red_zone();
1118 
1119   inline bool stack_yellow_zone_disabled();
1120   inline bool stack_yellow_zone_enabled();
1121 
1122   // Attempt to reguard the stack after a stack overflow may have occurred.
1123   // Returns true if (a) guard pages are not needed on this thread, (b) the
1124   // pages are already guarded, or (c) the pages were successfully reguarded.
1125   // Returns false if there is not enough stack space to reguard the pages, in
1126   // which case the caller should unwind a frame and try again.  The argument
1127   // should be the caller's (approximate) sp.
1128   bool reguard_stack(address cur_sp);
1129   // Similar to above but see if current stackpoint is out of the guard area
1130   // and reguard if possible.
1131   bool reguard_stack(void);
1132 
1133   // Misc. accessors/mutators
1134   void set_do_not_unlock(void)                   { _do_not_unlock_if_synchronized = true; }
1135   void clr_do_not_unlock(void)                   { _do_not_unlock_if_synchronized = false; }
1136   bool do_not_unlock(void)                       { return _do_not_unlock_if_synchronized; }
1137 
1138 #ifndef PRODUCT
1139   void record_jump(address target, address instr, const char* file, int line);
1140 #endif /* PRODUCT */
1141 
1142   // For assembly stub generation
1143   static ByteSize threadObj_offset()             { return byte_offset_of(JavaThread, _threadObj           ); }
1144 #ifndef PRODUCT
1145   static ByteSize jmp_ring_index_offset()        { return byte_offset_of(JavaThread, _jmp_ring_index      ); }
1146   static ByteSize jmp_ring_offset()              { return byte_offset_of(JavaThread, _jmp_ring            ); }
1147 #endif /* PRODUCT */
1148   static ByteSize jni_environment_offset()       { return byte_offset_of(JavaThread, _jni_environment     ); }
1149   static ByteSize last_Java_sp_offset()          {
1150     return byte_offset_of(JavaThread, _anchor) + JavaFrameAnchor::last_Java_sp_offset();
1151   }
1152   static ByteSize last_Java_pc_offset()          {
1153     return byte_offset_of(JavaThread, _anchor) + JavaFrameAnchor::last_Java_pc_offset();
1154   }
1155   static ByteSize frame_anchor_offset()          {
1156     return byte_offset_of(JavaThread, _anchor);
1157   }
1158   static ByteSize callee_target_offset()         { return byte_offset_of(JavaThread, _callee_target       ); }
1159   static ByteSize vm_result_offset()             { return byte_offset_of(JavaThread, _vm_result           ); }
1160   static ByteSize vm_result_2_offset()           { return byte_offset_of(JavaThread, _vm_result_2         ); }
1161   static ByteSize thread_state_offset()          { return byte_offset_of(JavaThread, _thread_state        ); }
1162   static ByteSize saved_exception_pc_offset()    { return byte_offset_of(JavaThread, _saved_exception_pc  ); }
1163   static ByteSize osthread_offset()              { return byte_offset_of(JavaThread, _osthread            ); }
1164   static ByteSize exception_oop_offset()         { return byte_offset_of(JavaThread, _exception_oop       ); }
1165   static ByteSize exception_pc_offset()          { return byte_offset_of(JavaThread, _exception_pc        ); }
1166   static ByteSize exception_handler_pc_offset()  { return byte_offset_of(JavaThread, _exception_handler_pc); }
1167   static ByteSize exception_stack_size_offset()  { return byte_offset_of(JavaThread, _exception_stack_size); }
1168   static ByteSize stack_guard_state_offset()     { return byte_offset_of(JavaThread, _stack_guard_state   ); }
1169   static ByteSize suspend_flags_offset()         { return byte_offset_of(JavaThread, _suspend_flags       ); }
1170 
1171   static ByteSize do_not_unlock_if_synchronized_offset() { return byte_offset_of(JavaThread, _do_not_unlock_if_synchronized); }
1172 
1173 #ifndef SERIALGC
1174   static ByteSize satb_mark_queue_offset()       { return byte_offset_of(JavaThread, _satb_mark_queue); }
1175   static ByteSize dirty_card_queue_offset()      { return byte_offset_of(JavaThread, _dirty_card_queue); }
1176 #endif // !SERIALGC
1177 
1178   // Returns the jni environment for this thread
1179   JNIEnv* jni_environment()                      { return &_jni_environment; }
1180 
1181   static JavaThread* thread_from_jni_environment(JNIEnv* env) {
1182     JavaThread *thread_from_jni_env = (JavaThread*)((intptr_t)env - in_bytes(jni_environment_offset()));
1183     // Only return NULL if thread is off the thread list; starting to
1184     // exit should not return NULL.
1185     if (thread_from_jni_env->is_terminated()) {
1186        thread_from_jni_env->block_if_vm_exited();
1187        return NULL;
1188     } else {
1189        return thread_from_jni_env;
1190     }
1191   }
1192 
1193   // JNI critical regions. These can nest.
1194   bool in_critical()    { return _jni_active_critical > 0; }
1195   void enter_critical() { assert(Thread::current() == this,
1196                                  "this must be current thread");
1197                           _jni_active_critical++; }
1198   void exit_critical()  { assert(Thread::current() == this,
1199                                  "this must be current thread");
1200                           _jni_active_critical--;
1201                           assert(_jni_active_critical >= 0,
1202                                  "JNI critical nesting problem?"); }
1203 
1204   // For deadlock detection
1205   int depth_first_number() { return _depth_first_number; }
1206   void set_depth_first_number(int dfn) { _depth_first_number = dfn; }
1207 
1208  private:
1209   void set_monitor_chunks(MonitorChunk* monitor_chunks) { _monitor_chunks = monitor_chunks; }
1210 
1211  public:
1212   MonitorChunk* monitor_chunks() const           { return _monitor_chunks; }
1213   void add_monitor_chunk(MonitorChunk* chunk);
1214   void remove_monitor_chunk(MonitorChunk* chunk);
1215   bool in_deopt_handler() const                  { return _in_deopt_handler > 0; }
1216   void inc_in_deopt_handler()                    { _in_deopt_handler++; }
1217   void dec_in_deopt_handler()                    {
1218     assert(_in_deopt_handler > 0, "mismatched deopt nesting");
1219     if (_in_deopt_handler > 0) { // robustness
1220       _in_deopt_handler--;
1221     }
1222   }
1223 
1224  private:
1225   void set_entry_point(ThreadFunction entry_point) { _entry_point = entry_point; }
1226 
1227  public:
1228 
1229   // Frame iteration; calls the function f for all frames on the stack
1230   void frames_do(void f(frame*, const RegisterMap*));
1231 
1232   // Memory operations
1233   void oops_do(OopClosure* f, CodeBlobClosure* cf);
1234 
1235   // Sweeper operations
1236   void nmethods_do(CodeBlobClosure* cf);
1237 
1238   // Memory management operations
1239   void gc_epilogue();
1240   void gc_prologue();
1241 
1242   // Misc. operations
1243   char* name() const { return (char*)get_thread_name(); }
1244   void print_on(outputStream* st) const;
1245   void print() const { print_on(tty); }
1246   void print_value();
1247   void print_thread_state_on(outputStream* ) const      PRODUCT_RETURN;
1248   void print_thread_state() const                       PRODUCT_RETURN;
1249   void print_on_error(outputStream* st, char* buf, int buflen) const;
1250   void verify();
1251   const char* get_thread_name() const;
1252 private:
1253   // factor out low-level mechanics for use in both normal and error cases
1254   const char* get_thread_name_string(char* buf = NULL, int buflen = 0) const;
1255 public:
1256   const char* get_threadgroup_name() const;
1257   const char* get_parent_name() const;
1258 
1259   // Accessing frames
1260   frame last_frame() {
1261     _anchor.make_walkable(this);
1262     return pd_last_frame();
1263   }
1264   javaVFrame* last_java_vframe(RegisterMap* reg_map);
1265 
1266   // Returns method at 'depth' java or native frames down the stack
1267   // Used for security checks
1268   klassOop security_get_caller_class(int depth);
1269 
1270   // Print stack trace in external format
1271   void print_stack_on(outputStream* st);
1272   void print_stack() { print_stack_on(tty); }
1273 
1274   // Print stack traces in various internal formats
1275   void trace_stack()                             PRODUCT_RETURN;
1276   void trace_stack_from(vframe* start_vf)        PRODUCT_RETURN;
1277   void trace_frames()                            PRODUCT_RETURN;
1278 
1279   // Returns the number of stack frames on the stack
1280   int depth() const;
1281 
1282   // Function for testing deoptimization
1283   void deoptimize();
1284   void make_zombies();
1285 
1286   void deoptimized_wrt_marked_nmethods();
1287 
1288   // Profiling operation (see fprofile.cpp)
1289  public:
1290    bool profile_last_Java_frame(frame* fr);
1291 
1292  private:
1293    ThreadProfiler* _thread_profiler;
1294  private:
1295    friend class FlatProfiler;                    // uses both [gs]et_thread_profiler.
1296    friend class FlatProfilerTask;                // uses get_thread_profiler.
1297    friend class ThreadProfilerMark;              // uses get_thread_profiler.
1298    ThreadProfiler* get_thread_profiler()         { return _thread_profiler; }
1299    ThreadProfiler* set_thread_profiler(ThreadProfiler* tp) {
1300      ThreadProfiler* result = _thread_profiler;
1301      _thread_profiler = tp;
1302      return result;
1303    }
1304 
1305   // Static operations
1306  public:
1307   // Returns the running thread as a JavaThread
1308   static inline JavaThread* current();
1309 
1310   // Returns the active Java thread.  Do not use this if you know you are calling
1311   // from a JavaThread, as it's slower than JavaThread::current.  If called from
1312   // the VMThread, it also returns the JavaThread that instigated the VMThread's
1313   // operation.  You may not want that either.
1314   static JavaThread* active();
1315 
1316   inline CompilerThread* as_CompilerThread();
1317 
1318  public:
1319   virtual void run();
1320   void thread_main_inner();
1321 
1322  private:
1323   // PRIVILEGED STACK
1324   PrivilegedElement*  _privileged_stack_top;
1325   GrowableArray<oop>* _array_for_gc;
1326  public:
1327 
1328   // Returns the privileged_stack information.
1329   PrivilegedElement* privileged_stack_top() const       { return _privileged_stack_top; }
1330   void set_privileged_stack_top(PrivilegedElement *e)   { _privileged_stack_top = e; }
1331   void register_array_for_gc(GrowableArray<oop>* array) { _array_for_gc = array; }
1332 
1333  public:
1334   // Thread local information maintained by JVMTI.
1335   void set_jvmti_thread_state(JvmtiThreadState *value)                           { _jvmti_thread_state = value; }
1336   // A JvmtiThreadState is lazily allocated. This jvmti_thread_state()
1337   // getter is used to get this JavaThread's JvmtiThreadState if it has
1338   // one which means NULL can be returned. JvmtiThreadState::state_for()
1339   // is used to get the specified JavaThread's JvmtiThreadState if it has
1340   // one or it allocates a new JvmtiThreadState for the JavaThread and
1341   // returns it. JvmtiThreadState::state_for() will return NULL only if
1342   // the specified JavaThread is exiting.
1343   JvmtiThreadState *jvmti_thread_state() const                                   { return _jvmti_thread_state; }
1344   static ByteSize jvmti_thread_state_offset()                                    { return byte_offset_of(JavaThread, _jvmti_thread_state); }
1345   void set_jvmti_get_loaded_classes_closure(JvmtiGetLoadedClassesClosure* value) { _jvmti_get_loaded_classes_closure = value; }
1346   JvmtiGetLoadedClassesClosure* get_jvmti_get_loaded_classes_closure() const     { return _jvmti_get_loaded_classes_closure; }
1347 
1348   // JVMTI PopFrame support
1349   // Setting and clearing popframe_condition
1350   // All of these enumerated values are bits. popframe_pending
1351   // indicates that a PopFrame() has been requested and not yet been
1352   // completed. popframe_processing indicates that that PopFrame() is in
1353   // the process of being completed. popframe_force_deopt_reexecution_bit
1354   // indicates that special handling is required when returning to a
1355   // deoptimized caller.
1356   enum PopCondition {
1357     popframe_inactive                      = 0x00,
1358     popframe_pending_bit                   = 0x01,
1359     popframe_processing_bit                = 0x02,
1360     popframe_force_deopt_reexecution_bit   = 0x04
1361   };
1362   PopCondition popframe_condition()                   { return (PopCondition) _popframe_condition; }
1363   void set_popframe_condition(PopCondition c)         { _popframe_condition = c; }
1364   void set_popframe_condition_bit(PopCondition c)     { _popframe_condition |= c; }
1365   void clear_popframe_condition()                     { _popframe_condition = popframe_inactive; }
1366   static ByteSize popframe_condition_offset()         { return byte_offset_of(JavaThread, _popframe_condition); }
1367   bool has_pending_popframe()                         { return (popframe_condition() & popframe_pending_bit) != 0; }
1368   bool popframe_forcing_deopt_reexecution()           { return (popframe_condition() & popframe_force_deopt_reexecution_bit) != 0; }
1369   void clear_popframe_forcing_deopt_reexecution()     { _popframe_condition &= ~popframe_force_deopt_reexecution_bit; }
1370 #ifdef CC_INTERP
1371   bool pop_frame_pending(void)                        { return ((_popframe_condition & popframe_pending_bit) != 0); }
1372   void clr_pop_frame_pending(void)                    { _popframe_condition = popframe_inactive; }
1373   bool pop_frame_in_process(void)                     { return ((_popframe_condition & popframe_processing_bit) != 0); }
1374   void set_pop_frame_in_process(void)                 { _popframe_condition |= popframe_processing_bit; }
1375   void clr_pop_frame_in_process(void)                 { _popframe_condition &= ~popframe_processing_bit; }
1376 #endif
1377 
1378  private:
1379   // Saved incoming arguments to popped frame.
1380   // Used only when popped interpreted frame returns to deoptimized frame.
1381   void*    _popframe_preserved_args;
1382   int      _popframe_preserved_args_size;
1383 
1384  public:
1385   void  popframe_preserve_args(ByteSize size_in_bytes, void* start);
1386   void* popframe_preserved_args();
1387   ByteSize popframe_preserved_args_size();
1388   WordSize popframe_preserved_args_size_in_words();
1389   void  popframe_free_preserved_args();
1390 
1391 
1392  private:
1393   JvmtiThreadState *_jvmti_thread_state;
1394   JvmtiGetLoadedClassesClosure* _jvmti_get_loaded_classes_closure;
1395 
1396   // Used by the interpreter in fullspeed mode for frame pop, method
1397   // entry, method exit and single stepping support. This field is
1398   // only set to non-zero by the VM_EnterInterpOnlyMode VM operation.
1399   // It can be set to zero asynchronously (i.e., without a VM operation
1400   // or a lock) so we have to be very careful.
1401   int               _interp_only_mode;
1402 
1403  public:
1404   // used by the interpreter for fullspeed debugging support (see above)
1405   static ByteSize interp_only_mode_offset() { return byte_offset_of(JavaThread, _interp_only_mode); }
1406   bool is_interp_only_mode()                { return (_interp_only_mode != 0); }
1407   int get_interp_only_mode()                { return _interp_only_mode; }
1408   void increment_interp_only_mode()         { ++_interp_only_mode; }
1409   void decrement_interp_only_mode()         { --_interp_only_mode; }
1410 
1411  private:
1412   ThreadStatistics *_thread_stat;
1413 
1414  public:
1415   ThreadStatistics* get_thread_stat() const    { return _thread_stat; }
1416 
1417   // Return a blocker object for which this thread is blocked parking.
1418   oop current_park_blocker();
1419 
1420  private:
1421   static size_t _stack_size_at_create;
1422 
1423  public:
1424   static inline size_t stack_size_at_create(void) {
1425     return _stack_size_at_create;
1426   }
1427   static inline void set_stack_size_at_create(size_t value) {
1428     _stack_size_at_create = value;
1429   }
1430 
1431 #ifndef SERIALGC
1432   // SATB marking queue support
1433   ObjPtrQueue& satb_mark_queue() { return _satb_mark_queue; }
1434   static SATBMarkQueueSet& satb_mark_queue_set() {
1435     return _satb_mark_queue_set;
1436   }
1437 
1438   // Dirty card queue support
1439   DirtyCardQueue& dirty_card_queue() { return _dirty_card_queue; }
1440   static DirtyCardQueueSet& dirty_card_queue_set() {
1441     return _dirty_card_queue_set;
1442   }
1443 #endif // !SERIALGC
1444 
1445   // Machine dependent stuff
1446   #include "incls/_thread_pd.hpp.incl"
1447 
1448  public:
1449   void set_blocked_on_compilation(bool value) {
1450     _blocked_on_compilation = value;
1451   }
1452 
1453   bool blocked_on_compilation() {
1454     return _blocked_on_compilation;
1455   }
1456  protected:
1457   bool         _blocked_on_compilation;
1458 
1459 
1460   // JSR166 per-thread parker
1461 private:
1462   Parker*    _parker;
1463 public:
1464   Parker*     parker() { return _parker; }
1465 
1466   // Biased locking support
1467 private:
1468   GrowableArray<MonitorInfo*>* _cached_monitor_info;
1469 public:
1470   GrowableArray<MonitorInfo*>* cached_monitor_info() { return _cached_monitor_info; }
1471   void set_cached_monitor_info(GrowableArray<MonitorInfo*>* info) { _cached_monitor_info = info; }
1472 
1473   // clearing/querying jni attach status
1474   bool is_attaching() const { return _is_attaching; }
1475   void set_attached() { _is_attaching = false; OrderAccess::fence(); }
1476 private:
1477   // This field is used to determine if a thread has claimed
1478   // a par_id: it is -1 if the thread has not claimed a par_id;
1479   // otherwise its value is the par_id that has been claimed.
1480   int _claimed_par_id;
1481 public:
1482   int get_claimed_par_id() { return _claimed_par_id; }
1483   void set_claimed_par_id(int id) { _claimed_par_id = id;}
1484 };
1485 
1486 // Inline implementation of JavaThread::current
1487 inline JavaThread* JavaThread::current() {
1488   Thread* thread = ThreadLocalStorage::thread();
1489   assert(thread != NULL && thread->is_Java_thread(), "just checking");
1490   return (JavaThread*)thread;
1491 }
1492 
1493 inline CompilerThread* JavaThread::as_CompilerThread() {
1494   assert(is_Compiler_thread(), "just checking");
1495   return (CompilerThread*)this;
1496 }
1497 
1498 inline bool JavaThread::stack_yellow_zone_disabled() {
1499   return _stack_guard_state == stack_guard_yellow_disabled;
1500 }
1501 
1502 inline bool JavaThread::stack_yellow_zone_enabled() {
1503 #ifdef ASSERT
1504   if (os::uses_stack_guard_pages()) {
1505     assert(_stack_guard_state != stack_guard_unused, "guard pages must be in use");
1506   }
1507 #endif
1508     return _stack_guard_state == stack_guard_enabled;
1509 }
1510 
1511 inline size_t JavaThread::stack_available(address cur_sp) {
1512   // This code assumes java stacks grow down
1513   address low_addr; // Limit on the address for deepest stack depth
1514   if ( _stack_guard_state == stack_guard_unused) {
1515     low_addr =  stack_base() - stack_size();
1516   } else {
1517     low_addr = stack_yellow_zone_base();
1518   }
1519   return cur_sp > low_addr ? cur_sp - low_addr : 0;
1520 }
1521 
1522 // A JavaThread for low memory detection support
1523 class LowMemoryDetectorThread : public JavaThread {
1524   friend class VMStructs;
1525 public:
1526   LowMemoryDetectorThread(ThreadFunction entry_point) : JavaThread(entry_point) {};
1527 
1528   // Hide this thread from external view.
1529   bool is_hidden_from_external_view() const      { return true; }
1530 };
1531 
1532 // A thread used for Compilation.
1533 class CompilerThread : public JavaThread {
1534   friend class VMStructs;
1535  private:
1536   CompilerCounters* _counters;
1537 
1538   ciEnv*        _env;
1539   CompileLog*   _log;
1540   CompileTask*  _task;
1541   CompileQueue* _queue;
1542 
1543  public:
1544 
1545   static CompilerThread* current();
1546 
1547   CompilerThread(CompileQueue* queue, CompilerCounters* counters);
1548 
1549   bool is_Compiler_thread() const                { return true; }
1550   // Hide this compiler thread from external view.
1551   bool is_hidden_from_external_view() const      { return true; }
1552 
1553   CompileQueue* queue()                          { return _queue; }
1554   CompilerCounters* counters()                   { return _counters; }
1555 
1556   // Get/set the thread's compilation environment.
1557   ciEnv*        env()                            { return _env; }
1558   void          set_env(ciEnv* env)              { _env = env; }
1559 
1560   // Get/set the thread's logging information
1561   CompileLog*   log()                            { return _log; }
1562   void          init_log(CompileLog* log) {
1563     // Set once, for good.
1564     assert(_log == NULL, "set only once");
1565     _log = log;
1566   }
1567 
1568 #ifndef PRODUCT
1569 private:
1570   IdealGraphPrinter *_ideal_graph_printer;
1571 public:
1572   IdealGraphPrinter *ideal_graph_printer()                       { return _ideal_graph_printer; }
1573   void set_ideal_graph_printer(IdealGraphPrinter *n)             { _ideal_graph_printer = n; }
1574 #endif
1575 
1576   // Get/set the thread's current task
1577   CompileTask*  task()                           { return _task; }
1578   void          set_task(CompileTask* task)      { _task = task; }
1579 };
1580 
1581 inline CompilerThread* CompilerThread::current() {
1582   return JavaThread::current()->as_CompilerThread();
1583 }
1584 
1585 
1586 // The active thread queue. It also keeps track of the current used
1587 // thread priorities.
1588 class Threads: AllStatic {
1589   friend class VMStructs;
1590  private:
1591   static JavaThread* _thread_list;
1592   static int         _number_of_threads;
1593   static int         _number_of_non_daemon_threads;
1594   static int         _return_code;
1595 
1596  public:
1597   // Thread management
1598   // force_daemon is a concession to JNI, where we may need to add a
1599   // thread to the thread list before allocating its thread object
1600   static void add(JavaThread* p, bool force_daemon = false);
1601   static void remove(JavaThread* p);
1602   static bool includes(JavaThread* p);
1603   static JavaThread* first()                     { return _thread_list; }
1604   static void threads_do(ThreadClosure* tc);
1605 
1606   // Initializes the vm and creates the vm thread
1607   static jint create_vm(JavaVMInitArgs* args, bool* canTryAgain);
1608   static void convert_vm_init_libraries_to_agents();
1609   static void create_vm_init_libraries();
1610   static void create_vm_init_agents();
1611   static void shutdown_vm_agents();
1612   static bool destroy_vm();
1613   // Supported VM versions via JNI
1614   // Includes JNI_VERSION_1_1
1615   static jboolean is_supported_jni_version_including_1_1(jint version);
1616   // Does not include JNI_VERSION_1_1
1617   static jboolean is_supported_jni_version(jint version);
1618 
1619   // Garbage collection
1620   static void follow_other_roots(void f(oop*));
1621 
1622   // Apply "f->do_oop" to all root oops in all threads.
1623   // This version may only be called by sequential code.
1624   static void oops_do(OopClosure* f, CodeBlobClosure* cf);
1625   // This version may be called by sequential or parallel code.
1626   static void possibly_parallel_oops_do(OopClosure* f, CodeBlobClosure* cf);
1627   // This creates a list of GCTasks, one per thread.
1628   static void create_thread_roots_tasks(GCTaskQueue* q);
1629   // This creates a list of GCTasks, one per thread, for marking objects.
1630   static void create_thread_roots_marking_tasks(GCTaskQueue* q);
1631 
1632   // Apply "f->do_oop" to roots in all threads that
1633   // are part of compiled frames
1634   static void compiled_frame_oops_do(OopClosure* f, CodeBlobClosure* cf);
1635 
1636   static void convert_hcode_pointers();
1637   static void restore_hcode_pointers();
1638 
1639   // Sweeper
1640   static void nmethods_do(CodeBlobClosure* cf);
1641 
1642   static void gc_epilogue();
1643   static void gc_prologue();
1644 
1645   // Verification
1646   static void verify();
1647   static void print_on(outputStream* st, bool print_stacks, bool internal_format, bool print_concurrent_locks);
1648   static void print(bool print_stacks, bool internal_format) {
1649     // this function is only used by debug.cpp
1650     print_on(tty, print_stacks, internal_format, false /* no concurrent lock printed */);
1651   }
1652   static void print_on_error(outputStream* st, Thread* current, char* buf, int buflen);
1653 
1654   // Get Java threads that are waiting to enter a monitor. If doLock
1655   // is true, then Threads_lock is grabbed as needed. Otherwise, the
1656   // VM needs to be at a safepoint.
1657   static GrowableArray<JavaThread*>* get_pending_threads(int count,
1658     address monitor, bool doLock);
1659 
1660   // Get owning Java thread from the monitor's owner field. If doLock
1661   // is true, then Threads_lock is grabbed as needed. Otherwise, the
1662   // VM needs to be at a safepoint.
1663   static JavaThread *owning_thread_from_monitor_owner(address owner,
1664     bool doLock);
1665 
1666   // Number of threads on the active threads list
1667   static int number_of_threads()                 { return _number_of_threads; }
1668   // Number of non-daemon threads on the active threads list
1669   static int number_of_non_daemon_threads()      { return _number_of_non_daemon_threads; }
1670 
1671   // Deoptimizes all frames tied to marked nmethods
1672   static void deoptimized_wrt_marked_nmethods();
1673 
1674 };
1675 
1676 
1677 // Thread iterator
1678 class ThreadClosure: public StackObj {
1679  public:
1680   virtual void do_thread(Thread* thread) = 0;
1681 };
1682 
1683 class SignalHandlerMark: public StackObj {
1684 private:
1685   Thread* _thread;
1686 public:
1687   SignalHandlerMark(Thread* t) {
1688     _thread = t;
1689     if (_thread) _thread->enter_signal_handler();
1690   }
1691   ~SignalHandlerMark() {
1692     if (_thread) _thread->leave_signal_handler();
1693     _thread = NULL;
1694   }
1695 };
1696 
1697 // ParkEvents are type-stable and immortal.
1698 //
1699 // Lifecycle: Once a ParkEvent is associated with a thread that ParkEvent remains
1700 // associated with the thread for the thread's entire lifetime - the relationship is
1701 // stable. A thread will be associated at most one ParkEvent.  When the thread
1702 // expires, the ParkEvent moves to the EventFreeList.  New threads attempt to allocate from
1703 // the EventFreeList before creating a new Event.  Type-stability frees us from
1704 // worrying about stale Event or Thread references in the objectMonitor subsystem.
1705 // (A reference to ParkEvent is always valid, even though the event may no longer be associated
1706 // with the desired or expected thread.  A key aspect of this design is that the callers of
1707 // park, unpark, etc must tolerate stale references and spurious wakeups).
1708 //
1709 // Only the "associated" thread can block (park) on the ParkEvent, although
1710 // any other thread can unpark a reachable parkevent.  Park() is allowed to
1711 // return spuriously.  In fact park-unpark a really just an optimization to
1712 // avoid unbounded spinning and surrender the CPU to be a polite system citizen.
1713 // A degenerate albeit "impolite" park-unpark implementation could simply return.
1714 // See http://blogs.sun.com/dave for more details.
1715 //
1716 // Eventually I'd like to eliminate Events and ObjectWaiters, both of which serve as
1717 // thread proxies, and simply make the THREAD structure type-stable and persistent.
1718 // Currently, we unpark events associated with threads, but ideally we'd just
1719 // unpark threads.
1720 //
1721 // The base-class, PlatformEvent, is platform-specific while the ParkEvent is
1722 // platform-independent.  PlatformEvent provides park(), unpark(), etc., and
1723 // is abstract -- that is, a PlatformEvent should never be instantiated except
1724 // as part of a ParkEvent.
1725 // Equivalently we could have defined a platform-independent base-class that
1726 // exported Allocate(), Release(), etc.  The platform-specific class would extend
1727 // that base-class, adding park(), unpark(), etc.
1728 //
1729 // A word of caution: The JVM uses 2 very similar constructs:
1730 // 1. ParkEvent are used for Java-level "monitor" synchronization.
1731 // 2. Parkers are used by JSR166-JUC park-unpark.
1732 //
1733 // We'll want to eventually merge these redundant facilities and use ParkEvent.
1734 
1735 
1736 class ParkEvent : public os::PlatformEvent {
1737   private:
1738     ParkEvent * FreeNext ;
1739 
1740     // Current association
1741     Thread * AssociatedWith ;
1742     intptr_t RawThreadIdentity ;        // LWPID etc
1743     volatile int Incarnation ;
1744 
1745     // diagnostic : keep track of last thread to wake this thread.
1746     // this is useful for construction of dependency graphs.
1747     void * LastWaker ;
1748 
1749   public:
1750     // MCS-CLH list linkage and Native Mutex/Monitor
1751     ParkEvent * volatile ListNext ;
1752     ParkEvent * volatile ListPrev ;
1753     volatile intptr_t OnList ;
1754     volatile int TState ;
1755     volatile int Notified ;             // for native monitor construct
1756     volatile int IsWaiting ;            // Enqueued on WaitSet
1757 
1758 
1759   private:
1760     static ParkEvent * volatile FreeList ;
1761     static volatile int ListLock ;
1762 
1763     // It's prudent to mark the dtor as "private"
1764     // ensuring that it's not visible outside the package.
1765     // Unfortunately gcc warns about such usage, so
1766     // we revert to the less desirable "protected" visibility.
1767     // The other compilers accept private dtors.
1768 
1769   protected:        // Ensure dtor is never invoked
1770     ~ParkEvent() { guarantee (0, "invariant") ; }
1771 
1772     ParkEvent() : PlatformEvent() {
1773        AssociatedWith = NULL ;
1774        FreeNext       = NULL ;
1775        ListNext       = NULL ;
1776        ListPrev       = NULL ;
1777        OnList         = 0 ;
1778        TState         = 0 ;
1779        Notified       = 0 ;
1780        IsWaiting      = 0 ;
1781     }
1782 
1783     // We use placement-new to force ParkEvent instances to be
1784     // aligned on 256-byte address boundaries.  This ensures that the least
1785     // significant byte of a ParkEvent address is always 0.
1786 
1787     void * operator new (size_t sz) ;
1788     void operator delete (void * a) ;
1789 
1790   public:
1791     static ParkEvent * Allocate (Thread * t) ;
1792     static void Release (ParkEvent * e) ;
1793 } ;