1 /*
  2  * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
  3  * Copyright (c) 2021, Azul Systems, Inc. All rights reserved.
  4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  5  *
  6  * This code is free software; you can redistribute it and/or modify it
  7  * under the terms of the GNU General Public License version 2 only, as
  8  * published by the Free Software Foundation.
  9  *
 10  * This code is distributed in the hope that it will be useful, but WITHOUT
 11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 13  * version 2 for more details (a copy is included in the LICENSE file that
 14  * accompanied this code).
 15  *
 16  * You should have received a copy of the GNU General Public License version
 17  * 2 along with this work; if not, write to the Free Software Foundation,
 18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 19  *
 20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 21  * or visit www.oracle.com if you need additional information or have any
 22  * questions.
 23  *
 24  */
 25 
 26 #ifndef SHARE_RUNTIME_THREAD_HPP
 27 #define SHARE_RUNTIME_THREAD_HPP
 28 
 29 #include "gc/shared/gcThreadLocalData.hpp"
 30 #include "gc/shared/threadLocalAllocBuffer.hpp"
 31 #include "jni.h"
 32 #include "memory/allocation.hpp"
 33 #include "runtime/atomic.hpp"
 34 #include "runtime/globals.hpp"
 35 #include "runtime/os.hpp"
 36 #include "runtime/safepointMechanism.hpp"
 37 #include "runtime/threadHeapSampler.hpp"
 38 #include "runtime/threadLocalStorage.hpp"
 39 #include "runtime/threadStatisticalInfo.hpp"
 40 #include "runtime/unhandledOops.hpp"
 41 #include "utilities/globalDefinitions.hpp"
 42 #include "utilities/macros.hpp"
 43 #if INCLUDE_JFR
 44 #include "jfr/support/jfrThreadExtension.hpp"
 45 #endif
 46 
 47 class CompilerThread;
 48 class HandleArea;
 49 class HandleMark;
 50 class JvmtiRawMonitor;
 51 class NMethodClosure;
 52 class Metadata;
 53 class OopClosure;
 54 class OSThread;
 55 class ParkEvent;
 56 class ResourceArea;
 57 class SafeThreadsListPtr;
 58 class ThreadClosure;
 59 class ThreadsList;
 60 class ThreadsSMRSupport;
 61 class VMErrorCallback;
 62 
 63 
 64 DEBUG_ONLY(class ResourceMark;)
 65 
 66 class WorkerThread;
 67 
 68 class JavaThread;
 69 
 70 // Class hierarchy
 71 // - Thread
 72 //   - JavaThread
 73 //     - various subclasses eg CompilerThread, ServiceThread
 74 //   - NonJavaThread
 75 //     - NamedThread
 76 //       - VMThread
 77 //       - ConcurrentGCThread
 78 //       - WorkerThread
 79 //     - WatcherThread
 80 //     - JfrThreadSampler
 81 //     - JfrCPUSamplerThread
 82 //     - LogAsyncWriter
 83 //
 84 // All Thread subclasses must be either JavaThread or NonJavaThread.
 85 // This means !t->is_Java_thread() iff t is a NonJavaThread, or t is
 86 // a partially constructed/destroyed Thread.
 87 
 88 // Thread execution sequence and actions:
 89 // All threads:
 90 //  - thread_native_entry  // per-OS native entry point
 91 //    - stack initialization
 92 //    - other OS-level initialization (signal masks etc)
 93 //    - handshake with creating thread (if not started suspended)
 94 //    - this->call_run()  // common shared entry point
 95 //      - shared common initialization
 96 //      - this->pre_run()  // virtual per-thread-type initialization
 97 //      - this->run()      // virtual per-thread-type "main" logic
 98 //      - shared common tear-down
 99 //      - this->post_run()  // virtual per-thread-type tear-down
100 //      - // 'this' no longer referenceable
101 //    - OS-level tear-down (minimal)
102 //    - final logging
103 //
104 // For JavaThread:
105 //   - this->run()  // virtual but not normally overridden
106 //     - this->thread_main_inner()  // extra call level to ensure correct stack calculations
107 //       - this->entry_point()  // set differently for each kind of JavaThread
108 
109 class Thread: public ThreadShadow {
110   friend class VMError;
111   friend class VMErrorCallbackMark;
112   friend class VMStructs;
113   friend class JVMCIVMStructs;
114   friend class JavaThread;
115  private:
116 
117   // Current thread is maintained as a thread-local variable
118   static THREAD_LOCAL Thread* _thr_current;
119 
120   // On AArch64, the high order 32 bits are used by a "patching epoch" number
121   // which reflects if this thread has executed the required fences, after
122   // an nmethod gets disarmed. The low order 32 bits denote the disarmed value.
123   uint64_t _nmethod_disarmed_guard_value;
124 
125  public:
126   void set_nmethod_disarmed_guard_value(int value) {
127     _nmethod_disarmed_guard_value = (uint64_t)(uint32_t)value;
128   }
129 
130   static ByteSize nmethod_disarmed_guard_value_offset() {
131     ByteSize offset = byte_offset_of(Thread, _nmethod_disarmed_guard_value);
132     // At least on x86_64, nmethod entry barrier encodes disarmed value offset
133     // in instruction as disp8 immed
134     assert(in_bytes(offset) < 128, "Offset >= 128");
135     return offset;
136   }
137 
138  private:
139   // Poll data is used in generated code for safepoint polls.
140   // It is important for performance to put this at lower offset
141   // in Thread. The accessors are in JavaThread.
142   SafepointMechanism::ThreadData _poll_data;
143 
144   // Thread local data area available to the GC. The internal
145   // structure and contents of this data area is GC-specific.
146   // Only GC and GC barrier code should access this data area.
147   GCThreadLocalData _gc_data;
148 
149  public:
150   static ByteSize gc_data_offset() {
151     return byte_offset_of(Thread, _gc_data);
152   }
153 
154   template <typename T> T* gc_data() {
155     STATIC_ASSERT(sizeof(T) <= sizeof(_gc_data));
156     return reinterpret_cast<T*>(&_gc_data);
157   }
158 
159   // Exception handling
160   // (Note: _pending_exception and friends are in ThreadShadow)
161   //oop       _pending_exception;                // pending exception for current thread
162   // const char* _exception_file;                   // file information for exception (debugging only)
163   // int         _exception_line;                   // line information for exception (debugging only)
164  protected:
165   // JavaThread lifecycle support:
166   friend class SafeThreadsListPtr;  // for _threads_list_ptr, cmpxchg_threads_hazard_ptr(), {dec_,inc_,}nested_threads_hazard_ptr_cnt(), {g,s}et_threads_hazard_ptr(), inc_nested_handle_cnt(), tag_hazard_ptr() access
167   friend class ScanHazardPtrGatherProtectedThreadsClosure;  // for cmpxchg_threads_hazard_ptr(), get_threads_hazard_ptr(), is_hazard_ptr_tagged() access
168   friend class ScanHazardPtrGatherThreadsListClosure;  // for get_threads_hazard_ptr(), untag_hazard_ptr() access
169   friend class ScanHazardPtrPrintMatchingThreadsClosure;  // for get_threads_hazard_ptr(), is_hazard_ptr_tagged() access
170   friend class ThreadsSMRSupport;  // for _nested_threads_hazard_ptr_cnt, _threads_hazard_ptr, _threads_list_ptr access
171   friend class ThreadsListHandleTest;  // for _nested_threads_hazard_ptr_cnt, _threads_hazard_ptr, _threads_list_ptr access
172   friend class ValidateHazardPtrsClosure;  // for get_threads_hazard_ptr(), untag_hazard_ptr() access
173 
174   ThreadsList* volatile _threads_hazard_ptr;
175   SafeThreadsListPtr*   _threads_list_ptr;
176   ThreadsList*          cmpxchg_threads_hazard_ptr(ThreadsList* exchange_value, ThreadsList* compare_value);
177   ThreadsList*          get_threads_hazard_ptr() const;
178   void                  set_threads_hazard_ptr(ThreadsList* new_list);
179   static bool           is_hazard_ptr_tagged(ThreadsList* list) {
180     return (intptr_t(list) & intptr_t(1)) == intptr_t(1);
181   }
182   static ThreadsList*   tag_hazard_ptr(ThreadsList* list) {
183     return (ThreadsList*)(intptr_t(list) | intptr_t(1));
184   }
185   static ThreadsList*   untag_hazard_ptr(ThreadsList* list) {
186     return (ThreadsList*)(intptr_t(list) & ~intptr_t(1));
187   }
188   // This field is enabled via -XX:+EnableThreadSMRStatistics:
189   uint _nested_threads_hazard_ptr_cnt;
190   void dec_nested_threads_hazard_ptr_cnt() {
191     assert(_nested_threads_hazard_ptr_cnt != 0, "mismatched {dec,inc}_nested_threads_hazard_ptr_cnt()");
192     _nested_threads_hazard_ptr_cnt--;
193   }
194   void inc_nested_threads_hazard_ptr_cnt() {
195     _nested_threads_hazard_ptr_cnt++;
196   }
197   uint nested_threads_hazard_ptr_cnt() {
198     return _nested_threads_hazard_ptr_cnt;
199   }
200 
201  public:
202   // Is the target JavaThread protected by the calling Thread or by some other
203   // mechanism?
204   static bool is_JavaThread_protected(const JavaThread* target);
205   // Is the target JavaThread protected by a ThreadsListHandle (TLH) associated
206   // with the calling Thread?
207   static bool is_JavaThread_protected_by_TLH(const JavaThread* target);
208 
209  private:
210   DEBUG_ONLY(static Thread* _starting_thread;)
211   DEBUG_ONLY(bool _suspendible_thread;)
212   DEBUG_ONLY(bool _indirectly_suspendible_thread;)
213   DEBUG_ONLY(bool _indirectly_safepoint_thread;)
214 
215  public:
216 #ifdef ASSERT
217   static bool is_starting_thread(const Thread* t);
218 
219   void set_suspendible_thread()   { _suspendible_thread = true; }
220   void clear_suspendible_thread() { _suspendible_thread = false; }
221   bool is_suspendible_thread()    { return _suspendible_thread; }
222 
223   void set_indirectly_suspendible_thread()   { _indirectly_suspendible_thread = true; }
224   void clear_indirectly_suspendible_thread() { _indirectly_suspendible_thread = false; }
225   bool is_indirectly_suspendible_thread()    { return _indirectly_suspendible_thread; }
226 
227   void set_indirectly_safepoint_thread()   { _indirectly_safepoint_thread = true; }
228   void clear_indirectly_safepoint_thread() { _indirectly_safepoint_thread = false; }
229   bool is_indirectly_safepoint_thread()    { return _indirectly_safepoint_thread; }
230 #endif
231 
232  private:
233   // Point to the last handle mark
234   HandleMark* _last_handle_mark;
235 
236   // Claim value for parallel iteration over threads.
237   uintx _threads_do_token;
238 
239   // Support for GlobalCounter
240  private:
241   volatile uintx _rcu_counter;
242  public:
243   volatile uintx* get_rcu_counter() {
244     return &_rcu_counter;
245   }
246 
247  public:
248   void set_last_handle_mark(HandleMark* mark)   { _last_handle_mark = mark; }
249   HandleMark* last_handle_mark() const          { return _last_handle_mark; }
250 
251  private:
252   // Used by SkipGCALot class.
253   NOT_PRODUCT(bool _skip_gcalot;)               // Should we elide gc-a-lot?
254 
255   friend class GCLocker;
256 
257  private:
258   ThreadLocalAllocBuffer _tlab;                 // Thread-local eden
259   jlong _allocated_bytes;                       // Cumulative number of bytes allocated on
260                                                 // the Java heap
261   ThreadHeapSampler _heap_sampler;              // For use when sampling the memory.
262 
263   ThreadStatisticalInfo _statistical_info;      // Statistics about the thread
264 
265   JFR_ONLY(DEFINE_THREAD_LOCAL_FIELD_JFR;)      // Thread-local data for jfr
266 
267   JvmtiRawMonitor* _current_pending_raw_monitor; // JvmtiRawMonitor this thread
268                                                  // is waiting to lock
269  public:
270   // Constructor
271   Thread(MemTag mem_tag = mtThread);
272   virtual ~Thread() = 0;        // Thread is abstract.
273 
274   // Manage Thread::current()
275   void initialize_thread_current();
276   static void clear_thread_current(); // TLS cleanup needed before threads terminate
277 
278  protected:
279   // To be implemented by children.
280   virtual void run() = 0;
281   virtual void pre_run() = 0;
282   virtual void post_run() = 0;  // Note: Thread must not be deleted prior to calling this!
283 
284 #ifdef ASSERT
285   enum RunState {
286     PRE_CALL_RUN,
287     CALL_RUN,
288     PRE_RUN,
289     RUN,
290     POST_RUN
291     // POST_CALL_RUN - can't define this one as 'this' may be deleted when we want to set it
292   };
293   RunState _run_state;  // for lifecycle checks
294 #endif
295 
296 
297  public:
298   // invokes <ChildThreadClass>::run(), with common preparations and cleanups.
299   void call_run();
300 
301   // Testers
302   virtual bool is_VM_thread()       const            { return false; }
303   virtual bool is_Java_thread()     const            { return false; }
304   virtual bool is_Compiler_thread() const            { return false; }
305   virtual bool is_service_thread() const             { return false; }
306   virtual bool is_hidden_from_external_view() const  { return false; }
307   virtual bool is_jvmti_agent_thread() const         { return false; }
308   virtual bool is_Watcher_thread() const             { return false; }
309   virtual bool is_ConcurrentGC_thread() const        { return false; }
310   virtual bool is_Named_thread() const               { return false; }
311   virtual bool is_Worker_thread() const              { return false; }
312   virtual bool is_JfrSampler_thread() const          { return false; }
313   virtual bool is_JfrRecorder_thread() const         { return false; }
314   virtual bool is_AttachListener_thread() const      { return false; }
315   virtual bool is_monitor_deflation_thread() const   { return false; }
316 
317   // Convenience cast functions
318   CompilerThread* as_Compiler_thread() const {
319     assert(is_Compiler_thread(), "Must be compiler thread");
320     return (CompilerThread*)this;
321   }
322 
323   // Can this thread make Java upcalls
324   virtual bool can_call_java() const                 { return false; }
325 
326   // Is this a JavaThread that is on the VM's current ThreadsList?
327   // If so it must participate in the safepoint protocol.
328   virtual bool is_active_Java_thread() const         { return false; }
329 
330   // All threads are given names. For singleton subclasses we can
331   // just hard-wire the known name of the instance. JavaThreads and
332   // NamedThreads support multiple named instances, and dynamic
333   // changing of the name of an instance.
334   virtual const char* name() const { return "Unknown thread"; }
335 
336   // A thread's type name is also made available for debugging
337   // and logging.
338   virtual const char* type_name() const { return "Thread"; }
339 
340   // Returns the current thread (ASSERTS if null)
341   static inline Thread* current();
342   // Returns the current thread, or null if not attached
343   static inline Thread* current_or_null();
344   // Returns the current thread, or null if not attached, and is
345   // safe for use from signal-handlers
346   static inline Thread* current_or_null_safe();
347 
348   // Common thread operations
349 #ifdef ASSERT
350   static void check_for_dangling_thread_pointer(Thread *thread);
351 #endif
352   static void set_priority(Thread* thread, ThreadPriority priority);
353   static void start(Thread* thread);
354 
355   void set_native_thread_name(const char *name) {
356     assert(Thread::current() == this, "set_native_thread_name can only be called on the current thread");
357     os::set_native_thread_name(name);
358   }
359 
360   // Support for Unhandled Oop detection
361   // Add the field for both, fastdebug and debug, builds to keep
362   // Thread's fields layout the same.
363   // Note: CHECK_UNHANDLED_OOPS is defined only for fastdebug build.
364 #ifdef CHECK_UNHANDLED_OOPS
365  private:
366   UnhandledOops* _unhandled_oops;
367 #elif defined(ASSERT)
368  private:
369   void* _unhandled_oops;
370 #endif
371 #ifdef CHECK_UNHANDLED_OOPS
372  public:
373   UnhandledOops* unhandled_oops() { return _unhandled_oops; }
374   // Mark oop safe for gc.  It may be stack allocated but won't move.
375   void allow_unhandled_oop(oop *op) {
376     if (CheckUnhandledOops) unhandled_oops()->allow_unhandled_oop(op);
377   }
378   // Clear oops at safepoint so crashes point to unhandled oop violator
379   void clear_unhandled_oops() {
380     if (CheckUnhandledOops) unhandled_oops()->clear_unhandled_oops();
381   }
382 #endif // CHECK_UNHANDLED_OOPS
383 
384  public:
385 #ifndef PRODUCT
386   bool skip_gcalot()           { return _skip_gcalot; }
387   void set_skip_gcalot(bool v) { _skip_gcalot = v;    }
388 #endif
389 
390   // Resource area
391   ResourceArea* resource_area() const            { return _resource_area; }
392   void set_resource_area(ResourceArea* area)     { _resource_area = area; }
393 
394   OSThread* osthread() const                     { return _osthread;   }
395   void set_osthread(OSThread* thread)            { _osthread = thread; }
396 
397   // Internal handle support
398   HandleArea* handle_area() const                { return _handle_area; }
399   void set_handle_area(HandleArea* area)         { _handle_area = area; }
400 
401   GrowableArray<Metadata*>* metadata_handles() const          { return _metadata_handles; }
402   void set_metadata_handles(GrowableArray<Metadata*>* handles){ _metadata_handles = handles; }
403 
404   // Thread-Local Allocation Buffer (TLAB) support
405   ThreadLocalAllocBuffer& tlab()                 { return _tlab; }
406   void initialize_tlab();
407   void retire_tlab(ThreadLocalAllocStats* stats = nullptr);
408   void fill_tlab(HeapWord* start, size_t pre_reserved, size_t new_size);
409 
410   jlong allocated_bytes()               { return _allocated_bytes; }
411   void set_allocated_bytes(jlong value) { _allocated_bytes = value; }
412   void incr_allocated_bytes(jlong size) { _allocated_bytes += size; }
413   inline jlong cooked_allocated_bytes();
414 
415   ThreadHeapSampler& heap_sampler()     { return _heap_sampler; }
416 
417   ThreadStatisticalInfo& statistical_info() { return _statistical_info; }
418 
419   JFR_ONLY(DEFINE_THREAD_LOCAL_ACCESSOR_JFR;)
420 
421   // For tracking the Jvmti raw monitor the thread is pending on.
422   JvmtiRawMonitor* current_pending_raw_monitor() {
423     return _current_pending_raw_monitor;
424   }
425   void set_current_pending_raw_monitor(JvmtiRawMonitor* monitor) {
426     _current_pending_raw_monitor = monitor;
427   }
428 
429   // GC support
430   // Apply "f->do_oop" to all root oops in "this".
431   //   Used by JavaThread::oops_do.
432   // Apply "cf->do_nmethod" (if !nullptr) to all nmethods active in frames
433   virtual void oops_do_no_frames(OopClosure* f, NMethodClosure* cf);
434   virtual void oops_do_frames(OopClosure* f, NMethodClosure* cf) {}
435   void oops_do(OopClosure* f, NMethodClosure* cf);
436 
437   // Handles the parallel case for claim_threads_do.
438  private:
439   bool claim_par_threads_do(uintx claim_token);
440  public:
441   // Requires that "claim_token" is that of the current iteration.
442   // If "is_par" is false, sets the token of "this" to
443   // "claim_token", and returns "true".  If "is_par" is true,
444   // uses an atomic instruction to set the current thread's token to
445   // "claim_token", if it is not already.  Returns "true" iff the
446   // calling thread does the update, this indicates that the calling thread
447   // has claimed the thread in the current iteration.
448   bool claim_threads_do(bool is_par, uintx claim_token) {
449     if (!is_par) {
450       _threads_do_token = claim_token;
451       return true;
452     } else {
453       return claim_par_threads_do(claim_token);
454     }
455   }
456 
457   uintx threads_do_token() const { return _threads_do_token; }
458 
459   // jvmtiRedefineClasses support
460   void metadata_handles_do(void f(Metadata*));
461 
462  private:
463   // Check if address is within the given range of this thread's
464   // stack:  stack_base() > adr >/>= limit
465   // The check is inclusive of limit if passed true, else exclusive.
466   bool is_in_stack_range(address adr, address limit, bool inclusive) const {
467     assert(stack_base() > limit && limit >= stack_end(), "limit is outside of stack");
468     return stack_base() > adr && (inclusive ? adr >= limit : adr > limit);
469   }
470 
471  public:
472   // Check if address is within the given range of this thread's
473   // stack:  stack_base() > adr >= limit
474   bool is_in_stack_range_incl(address adr, address limit) const {
475     return is_in_stack_range(adr, limit, true);
476   }
477 
478   // Check if address is within the given range of this thread's
479   // stack:  stack_base() > adr > limit
480   bool is_in_stack_range_excl(address adr, address limit) const {
481     return is_in_stack_range(adr, limit, false);
482   }
483 
484   // Check if address is in the stack mapped to this thread. Used mainly in
485   // error reporting (so has to include guard zone) and frame printing.
486   // Expects _stack_base to be initialized - checked with assert.
487   bool is_in_full_stack_checked(address adr) const {
488     return is_in_stack_range_incl(adr, stack_end());
489   }
490 
491   // Like is_in_full_stack_checked but without the assertions as this
492   // may be called in a thread before _stack_base is initialized.
493   bool is_in_full_stack(address adr) const {
494     address stack_end = _stack_base - _stack_size;
495     return _stack_base > adr && adr >= stack_end;
496   }
497 
498   // Check if address is in the live stack of this thread (not just for locks).
499   // Warning: can only be called by the current thread on itself.
500   bool is_in_live_stack(address adr) const {
501     assert(Thread::current() == this, "is_in_live_stack can only be called from current thread");
502     return is_in_stack_range_incl(adr, os::current_stack_pointer());
503   }
504 
505   // Sets the argument thread as starting thread. Returns failure if thread
506   // creation fails due to lack of memory, too many threads etc.
507   static bool set_as_starting_thread(JavaThread* jt);
508 
509 protected:
510   // OS data associated with the thread
511   OSThread* _osthread;  // Platform-specific thread information
512 
513   // Thread local resource area for temporary allocation within the VM
514   ResourceArea* _resource_area;
515 
516   DEBUG_ONLY(ResourceMark* _current_resource_mark;)
517 
518   // Thread local handle area for allocation of handles within the VM
519   HandleArea* _handle_area;
520   GrowableArray<Metadata*>* _metadata_handles;
521 
522   // Support for stack overflow handling, get_thread, etc.
523   address          _stack_base;
524   size_t           _stack_size;
525   int              _lgrp_id;
526 
527  public:
528   // Stack overflow support
529   address stack_base() const DEBUG_ONLY(;) NOT_DEBUG({ return _stack_base; })
530   // Needed for code that can query a new thread before the stack has been set.
531   address stack_base_or_null() const   { return _stack_base; }
532   void    set_stack_base(address base) { _stack_base = base; }
533   size_t  stack_size() const           { return _stack_size; }
534   void    set_stack_size(size_t size)  { _stack_size = size; }
535   address stack_end()  const           { return stack_base() - stack_size(); }
536   void    record_stack_base_and_size();
537   void    register_thread_stack_with_NMT();
538   void    unregister_thread_stack_with_NMT();
539 
540   int     lgrp_id() const        { return _lgrp_id; }
541   void    set_lgrp_id(int value) { _lgrp_id = value; }
542 
543   // Printing
544   void print_on(outputStream* st, bool print_extended_info) const;
545   virtual void print_on(outputStream* st) const { print_on(st, false); }
546   void print() const;
547   virtual void print_on_error(outputStream* st, char* buf, int buflen) const;
548   // Basic, non-virtual, printing support that is simple and always safe.
549   void print_value_on(outputStream* st) const;
550 
551   // Debug-only code
552 #ifdef ASSERT
553  private:
554   // Deadlock detection support for Mutex locks. List of locks own by thread.
555   Mutex* _owned_locks;
556   // Mutex::set_owner_implementation is the only place where _owned_locks is modified,
557   // thus the friendship
558   friend class Mutex;
559   friend class Monitor;
560 
561  public:
562   void print_owned_locks_on(outputStream* st) const;
563   void print_owned_locks() const                 { print_owned_locks_on(tty);    }
564   Mutex* owned_locks() const                     { return _owned_locks;          }
565   bool owns_locks() const                        { return owned_locks() != nullptr; }
566 
567   // Deadlock detection
568   ResourceMark* current_resource_mark()          { return _current_resource_mark; }
569   void set_current_resource_mark(ResourceMark* rm) { _current_resource_mark = rm; }
570 #endif // ASSERT
571 
572  private:
573   volatile int _jvmti_env_iteration_count;
574 
575  public:
576   void entering_jvmti_env_iteration()            { ++_jvmti_env_iteration_count; }
577   void leaving_jvmti_env_iteration()             { --_jvmti_env_iteration_count; }
578   bool is_inside_jvmti_env_iteration()           { return _jvmti_env_iteration_count > 0; }
579 
580   // Code generation
581   static ByteSize exception_file_offset()        { return byte_offset_of(Thread, _exception_file); }
582   static ByteSize exception_line_offset()        { return byte_offset_of(Thread, _exception_line); }
583 
584   static ByteSize stack_base_offset()            { return byte_offset_of(Thread, _stack_base); }
585   static ByteSize stack_size_offset()            { return byte_offset_of(Thread, _stack_size); }
586 
587   static ByteSize tlab_start_offset()            { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::start_offset(); }
588   static ByteSize tlab_end_offset()              { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::end_offset(); }
589   static ByteSize tlab_top_offset()              { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::top_offset(); }
590   static ByteSize tlab_pf_top_offset()           { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::pf_top_offset(); }
591 
592   JFR_ONLY(DEFINE_THREAD_LOCAL_OFFSET_JFR;)
593 
594  public:
595   ParkEvent * volatile _ParkEvent;            // for Object monitors, JVMTI raw monitors,
596                                               // and ObjectSynchronizer::read_stable_mark
597 
598   // Termination indicator used by the signal handler.
599   // _ParkEvent is just a convenient field we can null out after setting the JavaThread termination state
600   // (which can't itself be read from the signal handler if a signal hits during the Thread destructor).
601   bool has_terminated()                       { return Atomic::load(&_ParkEvent) == nullptr; };
602 
603   jint _hashStateW;                           // Marsaglia Shift-XOR thread-local RNG
604   jint _hashStateX;                           // thread-specific hashCode generator state
605   jint _hashStateY;
606   jint _hashStateZ;
607 
608   // Low-level leaf-lock primitives used to implement synchronization.
609   // Not for general synchronization use.
610   static void SpinAcquire(volatile int * Lock);
611   static void SpinRelease(volatile int * Lock);
612 
613 #if defined(__APPLE__) && defined(AARCH64)
614  private:
615   DEBUG_ONLY(bool _wx_init);
616   WXMode _wx_state;
617  public:
618   void init_wx();
619   WXMode enable_wx(WXMode new_state);
620 
621   void assert_wx_state(WXMode expected) {
622     assert(_wx_state == expected, "wrong state");
623   }
624 #endif // __APPLE__ && AARCH64
625 
626  private:
627   bool _in_asgct = false;
628  public:
629   bool in_asgct() const { return _in_asgct; }
630   void set_in_asgct(bool value) { _in_asgct = value; }
631   static bool current_in_asgct() {
632     Thread *cur = Thread::current_or_null_safe();
633     return cur != nullptr && cur->in_asgct();
634   }
635 
636  private:
637   VMErrorCallback* _vm_error_callbacks;
638 };
639 
640 class ThreadInAsgct {
641  private:
642   Thread* _thread;
643   bool _saved_in_asgct;
644  public:
645   ThreadInAsgct(Thread* thread) : _thread(thread) {
646     assert(thread != nullptr, "invariant");
647     // Allow AsyncGetCallTrace to be reentrant - save the previous state.
648     _saved_in_asgct = thread->in_asgct();
649     thread->set_in_asgct(true);
650   }
651   ~ThreadInAsgct() {
652     assert(_thread->in_asgct(), "invariant");
653     _thread->set_in_asgct(_saved_in_asgct);
654   }
655 };
656 
657 // Inline implementation of Thread::current()
658 inline Thread* Thread::current() {
659   Thread* current = current_or_null();
660   assert(current != nullptr, "Thread::current() called on detached thread");
661   return current;
662 }
663 
664 inline Thread* Thread::current_or_null() {
665   return _thr_current;
666 }
667 
668 inline Thread* Thread::current_or_null_safe() {
669   if (ThreadLocalStorage::is_initialized()) {
670     return ThreadLocalStorage::thread();
671   }
672   return nullptr;
673 }
674 
675 #endif // SHARE_RUNTIME_THREAD_HPP