1 /*
  2  * Copyright (c) 1997, 2023, 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 "jni.h"
 30 #include "gc/shared/gcThreadLocalData.hpp"
 31 #include "gc/shared/threadLocalAllocBuffer.hpp"
 32 #include "memory/allocation.hpp"
 33 #include "runtime/atomic.hpp"
 34 #include "runtime/globals.hpp"
 35 #include "runtime/os.hpp"
 36 #include "runtime/threadHeapSampler.hpp"
 37 #include "runtime/threadLocalStorage.hpp"
 38 #include "runtime/threadStatisticalInfo.hpp"
 39 #include "runtime/unhandledOops.hpp"
 40 #include "utilities/globalDefinitions.hpp"
 41 #include "utilities/macros.hpp"
 42 #if INCLUDE_JFR
 43 #include "jfr/support/jfrThreadExtension.hpp"
 44 #endif
 45 
 46 class CompilerThread;
 47 class HandleArea;
 48 class HandleMark;
 49 class ICRefillVerifier;
 50 class JvmtiRawMonitor;
 51 class Metadata;
 52 class OSThread;
 53 class ParkEvent;
 54 class ResourceArea;
 55 class SafeThreadsListPtr;
 56 class ThreadClosure;
 57 class ThreadsList;
 58 class ThreadsSMRSupport;
 59 class VMErrorCallback;
 60 
 61 class OopClosure;
 62 class CodeBlobClosure;
 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 //     - LogAsyncWriter
 82 //
 83 // All Thread subclasses must be either JavaThread or NonJavaThread.
 84 // This means !t->is_Java_thread() iff t is a NonJavaThread, or t is
 85 // a partially constructed/destroyed Thread.
 86 
 87 // Thread execution sequence and actions:
 88 // All threads:
 89 //  - thread_native_entry  // per-OS native entry point
 90 //    - stack initialization
 91 //    - other OS-level initialization (signal masks etc)
 92 //    - handshake with creating thread (if not started suspended)
 93 //    - this->call_run()  // common shared entry point
 94 //      - shared common initialization
 95 //      - this->pre_run()  // virtual per-thread-type initialization
 96 //      - this->run()      // virtual per-thread-type "main" logic
 97 //      - shared common tear-down
 98 //      - this->post_run()  // virtual per-thread-type tear-down
 99 //      - // 'this' no longer referenceable
100 //    - OS-level tear-down (minimal)
101 //    - final logging
102 //
103 // For JavaThread:
104 //   - this->run()  // virtual but not normally overridden
105 //     - this->thread_main_inner()  // extra call level to ensure correct stack calculations
106 //       - this->entry_point()  // set differently for each kind of JavaThread
107 
108 class Thread: public ThreadShadow {
109   friend class VMError;
110   friend class VMErrorCallbackMark;
111   friend class VMStructs;
112   friend class JVMCIVMStructs;
113  private:
114 
115 #ifndef USE_LIBRARY_BASED_TLS_ONLY
116   // Current thread is maintained as a thread-local variable
117   static THREAD_LOCAL Thread* _thr_current;
118 #endif
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   // Thread local data area available to the GC. The internal
140   // structure and contents of this data area is GC-specific.
141   // Only GC and GC barrier code should access this data area.
142   GCThreadLocalData _gc_data;
143 
144  public:
145   static ByteSize gc_data_offset() {
146     return byte_offset_of(Thread, _gc_data);
147   }
148 
149   template <typename T> T* gc_data() {
150     STATIC_ASSERT(sizeof(T) <= sizeof(_gc_data));
151     return reinterpret_cast<T*>(&_gc_data);
152   }
153 
154   // Exception handling
155   // (Note: _pending_exception and friends are in ThreadShadow)
156   //oop       _pending_exception;                // pending exception for current thread
157   // const char* _exception_file;                   // file information for exception (debugging only)
158   // int         _exception_line;                   // line information for exception (debugging only)
159  protected:
160 
161   DEBUG_ONLY(static Thread* _starting_thread;)
162 
163   // JavaThread lifecycle support:
164   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
165   friend class ScanHazardPtrGatherProtectedThreadsClosure;  // for cmpxchg_threads_hazard_ptr(), get_threads_hazard_ptr(), is_hazard_ptr_tagged() access
166   friend class ScanHazardPtrGatherThreadsListClosure;  // for get_threads_hazard_ptr(), untag_hazard_ptr() access
167   friend class ScanHazardPtrPrintMatchingThreadsClosure;  // for get_threads_hazard_ptr(), is_hazard_ptr_tagged() access
168   friend class ThreadsSMRSupport;  // for _nested_threads_hazard_ptr_cnt, _threads_hazard_ptr, _threads_list_ptr access
169   friend class ThreadsListHandleTest;  // for _nested_threads_hazard_ptr_cnt, _threads_hazard_ptr, _threads_list_ptr access
170   friend class ValidateHazardPtrsClosure;  // for get_threads_hazard_ptr(), untag_hazard_ptr() access
171 
172   ThreadsList* volatile _threads_hazard_ptr;
173   SafeThreadsListPtr*   _threads_list_ptr;
174   ThreadsList*          cmpxchg_threads_hazard_ptr(ThreadsList* exchange_value, ThreadsList* compare_value);
175   ThreadsList*          get_threads_hazard_ptr() const;
176   void                  set_threads_hazard_ptr(ThreadsList* new_list);
177   static bool           is_hazard_ptr_tagged(ThreadsList* list) {
178     return (intptr_t(list) & intptr_t(1)) == intptr_t(1);
179   }
180   static ThreadsList*   tag_hazard_ptr(ThreadsList* list) {
181     return (ThreadsList*)(intptr_t(list) | intptr_t(1));
182   }
183   static ThreadsList*   untag_hazard_ptr(ThreadsList* list) {
184     return (ThreadsList*)(intptr_t(list) & ~intptr_t(1));
185   }
186   // This field is enabled via -XX:+EnableThreadSMRStatistics:
187   uint _nested_threads_hazard_ptr_cnt;
188   void dec_nested_threads_hazard_ptr_cnt() {
189     assert(_nested_threads_hazard_ptr_cnt != 0, "mismatched {dec,inc}_nested_threads_hazard_ptr_cnt()");
190     _nested_threads_hazard_ptr_cnt--;
191   }
192   void inc_nested_threads_hazard_ptr_cnt() {
193     _nested_threads_hazard_ptr_cnt++;
194   }
195   uint nested_threads_hazard_ptr_cnt() {
196     return _nested_threads_hazard_ptr_cnt;
197   }
198 
199  public:
200   // Is the target JavaThread protected by the calling Thread or by some other
201   // mechanism?
202   static bool is_JavaThread_protected(const JavaThread* target);
203   // Is the target JavaThread protected by a ThreadsListHandle (TLH) associated
204   // with the calling Thread?
205   static bool is_JavaThread_protected_by_TLH(const JavaThread* target);
206 
207  private:
208   DEBUG_ONLY(bool _suspendible_thread;)
209   DEBUG_ONLY(bool _indirectly_suspendible_thread;)
210   DEBUG_ONLY(bool _indirectly_safepoint_thread;)
211 
212  public:
213   // Determines if a heap allocation failure will be retried
214   // (e.g., by deoptimizing and re-executing in the interpreter).
215   // In this case, the failed allocation must raise
216   // Universe::out_of_memory_error_retry() and omit side effects
217   // such as JVMTI events and handling -XX:+HeapDumpOnOutOfMemoryError
218   // and -XX:OnOutOfMemoryError.
219   virtual bool in_retryable_allocation() const { return false; }
220 
221 #ifdef ASSERT
222   void set_suspendible_thread()   { _suspendible_thread = true; }
223   void clear_suspendible_thread() { _suspendible_thread = false; }
224   bool is_suspendible_thread()    { return _suspendible_thread; }
225 
226   void set_indirectly_suspendible_thread()   { _indirectly_suspendible_thread = true; }
227   void clear_indirectly_suspendible_thread() { _indirectly_suspendible_thread = false; }
228   bool is_indirectly_suspendible_thread()    { return _indirectly_suspendible_thread; }
229 
230   void set_indirectly_safepoint_thread()   { _indirectly_safepoint_thread = true; }
231   void clear_indirectly_safepoint_thread() { _indirectly_safepoint_thread = false; }
232   bool is_indirectly_safepoint_thread()    { return _indirectly_safepoint_thread; }
233 #endif
234 
235  private:
236   // Point to the last handle mark
237   HandleMark* _last_handle_mark;
238 
239   // Claim value for parallel iteration over threads.
240   uintx _threads_do_token;
241 
242   // Support for GlobalCounter
243  private:
244   volatile uintx _rcu_counter;
245  public:
246   volatile uintx* get_rcu_counter() {
247     return &_rcu_counter;
248   }
249 
250  public:
251   void set_last_handle_mark(HandleMark* mark)   { _last_handle_mark = mark; }
252   HandleMark* last_handle_mark() const          { return _last_handle_mark; }
253  private:
254 
255 #ifdef ASSERT
256   ICRefillVerifier* _missed_ic_stub_refill_verifier;
257 
258  public:
259   ICRefillVerifier* missed_ic_stub_refill_verifier() {
260     return _missed_ic_stub_refill_verifier;
261   }
262 
263   void set_missed_ic_stub_refill_verifier(ICRefillVerifier* verifier) {
264     _missed_ic_stub_refill_verifier = verifier;
265   }
266 #endif // ASSERT
267 
268  private:
269   // Used by SkipGCALot class.
270   NOT_PRODUCT(bool _skip_gcalot;)               // Should we elide gc-a-lot?
271 
272   friend class GCLocker;
273 
274  private:
275   ThreadLocalAllocBuffer _tlab;                 // Thread-local eden
276   jlong _allocated_bytes;                       // Cumulative number of bytes allocated on
277                                                 // the Java heap
278   ThreadHeapSampler _heap_sampler;              // For use when sampling the memory.
279 
280   ThreadStatisticalInfo _statistical_info;      // Statistics about the thread
281 
282   JFR_ONLY(DEFINE_THREAD_LOCAL_FIELD_JFR;)      // Thread-local data for jfr
283 
284   JvmtiRawMonitor* _current_pending_raw_monitor; // JvmtiRawMonitor this thread
285                                                  // is waiting to lock
286  public:
287   // Constructor
288   Thread();
289   virtual ~Thread() = 0;        // Thread is abstract.
290 
291   // Manage Thread::current()
292   void initialize_thread_current();
293   static void clear_thread_current(); // TLS cleanup needed before threads terminate
294 
295  protected:
296   // To be implemented by children.
297   virtual void run() = 0;
298   virtual void pre_run() = 0;
299   virtual void post_run() = 0;  // Note: Thread must not be deleted prior to calling this!
300 
301 #ifdef ASSERT
302   enum RunState {
303     PRE_CALL_RUN,
304     CALL_RUN,
305     PRE_RUN,
306     RUN,
307     POST_RUN
308     // POST_CALL_RUN - can't define this one as 'this' may be deleted when we want to set it
309   };
310   RunState _run_state;  // for lifecycle checks
311 #endif
312 
313 
314  public:
315   // invokes <ChildThreadClass>::run(), with common preparations and cleanups.
316   void call_run();
317 
318   // Testers
319   virtual bool is_VM_thread()       const            { return false; }
320   virtual bool is_Java_thread()     const            { return false; }
321   virtual bool is_Compiler_thread() const            { return false; }
322   virtual bool is_service_thread() const             { return false; }
323   virtual bool is_hidden_from_external_view() const  { return false; }
324   virtual bool is_jvmti_agent_thread() const         { return false; }
325   virtual bool is_Watcher_thread() const             { return false; }
326   virtual bool is_ConcurrentGC_thread() const        { return false; }
327   virtual bool is_Named_thread() const               { return false; }
328   virtual bool is_Worker_thread() const              { return false; }
329   virtual bool is_JfrSampler_thread() const          { return false; }
330   virtual bool is_AttachListener_thread() const      { return false; }
331   virtual bool is_monitor_deflation_thread() const   { return false; }
332 
333   // Convenience cast functions
334   CompilerThread* as_Compiler_thread() const {
335     assert(is_Compiler_thread(), "Must be compiler thread");
336     return (CompilerThread*)this;
337   }
338 
339   // Can this thread make Java upcalls
340   virtual bool can_call_java() const                 { return false; }
341 
342   // Is this a JavaThread that is on the VM's current ThreadsList?
343   // If so it must participate in the safepoint protocol.
344   virtual bool is_active_Java_thread() const         { return false; }
345 
346   // All threads are given names. For singleton subclasses we can
347   // just hard-wire the known name of the instance. JavaThreads and
348   // NamedThreads support multiple named instances, and dynamic
349   // changing of the name of an instance.
350   virtual const char* name() const { return "Unknown thread"; }
351 
352   // A thread's type name is also made available for debugging
353   // and logging.
354   virtual const char* type_name() const { return "Thread"; }
355 
356   // Returns the current thread (ASSERTS if null)
357   static inline Thread* current();
358   // Returns the current thread, or null if not attached
359   static inline Thread* current_or_null();
360   // Returns the current thread, or null if not attached, and is
361   // safe for use from signal-handlers
362   static inline Thread* current_or_null_safe();
363 
364   // Common thread operations
365 #ifdef ASSERT
366   static void check_for_dangling_thread_pointer(Thread *thread);
367 #endif
368   static void set_priority(Thread* thread, ThreadPriority priority);
369   static void start(Thread* thread);
370 
371   void set_native_thread_name(const char *name) {
372     assert(Thread::current() == this, "set_native_thread_name can only be called on the current thread");
373     os::set_native_thread_name(name);
374   }
375 
376   // Support for Unhandled Oop detection
377   // Add the field for both, fastdebug and debug, builds to keep
378   // Thread's fields layout the same.
379   // Note: CHECK_UNHANDLED_OOPS is defined only for fastdebug build.
380 #ifdef CHECK_UNHANDLED_OOPS
381  private:
382   UnhandledOops* _unhandled_oops;
383 #elif defined(ASSERT)
384  private:
385   void* _unhandled_oops;
386 #endif
387 #ifdef CHECK_UNHANDLED_OOPS
388  public:
389   UnhandledOops* unhandled_oops() { return _unhandled_oops; }
390   // Mark oop safe for gc.  It may be stack allocated but won't move.
391   void allow_unhandled_oop(oop *op) {
392     if (CheckUnhandledOops) unhandled_oops()->allow_unhandled_oop(op);
393   }
394   // Clear oops at safepoint so crashes point to unhandled oop violator
395   void clear_unhandled_oops() {
396     if (CheckUnhandledOops) unhandled_oops()->clear_unhandled_oops();
397   }
398 #endif // CHECK_UNHANDLED_OOPS
399 
400  public:
401 #ifndef PRODUCT
402   bool skip_gcalot()           { return _skip_gcalot; }
403   void set_skip_gcalot(bool v) { _skip_gcalot = v;    }
404 #endif
405 
406   // Resource area
407   ResourceArea* resource_area() const            { return _resource_area; }
408   void set_resource_area(ResourceArea* area)     { _resource_area = area; }
409 
410   OSThread* osthread() const                     { return _osthread;   }
411   void set_osthread(OSThread* thread)            { _osthread = thread; }
412 
413   // Internal handle support
414   HandleArea* handle_area() const                { return _handle_area; }
415   void set_handle_area(HandleArea* area)         { _handle_area = area; }
416 
417   GrowableArray<Metadata*>* metadata_handles() const          { return _metadata_handles; }
418   void set_metadata_handles(GrowableArray<Metadata*>* handles){ _metadata_handles = handles; }
419 
420   // Thread-Local Allocation Buffer (TLAB) support
421   ThreadLocalAllocBuffer& tlab()                 { return _tlab; }
422   void initialize_tlab();
423 
424   jlong allocated_bytes()               { return _allocated_bytes; }
425   void set_allocated_bytes(jlong value) { _allocated_bytes = value; }
426   void incr_allocated_bytes(jlong size) { _allocated_bytes += size; }
427   inline jlong cooked_allocated_bytes();
428 
429   ThreadHeapSampler& heap_sampler()     { return _heap_sampler; }
430 
431   ThreadStatisticalInfo& statistical_info() { return _statistical_info; }
432 
433   JFR_ONLY(DEFINE_THREAD_LOCAL_ACCESSOR_JFR;)
434 
435   // For tracking the Jvmti raw monitor the thread is pending on.
436   JvmtiRawMonitor* current_pending_raw_monitor() {
437     return _current_pending_raw_monitor;
438   }
439   void set_current_pending_raw_monitor(JvmtiRawMonitor* monitor) {
440     _current_pending_raw_monitor = monitor;
441   }
442 
443   // GC support
444   // Apply "f->do_oop" to all root oops in "this".
445   //   Used by JavaThread::oops_do.
446   // Apply "cf->do_code_blob" (if !nullptr) to all code blobs active in frames
447   virtual void oops_do_no_frames(OopClosure* f, CodeBlobClosure* cf);
448   virtual void oops_do_frames(OopClosure* f, CodeBlobClosure* cf) {}
449   void oops_do(OopClosure* f, CodeBlobClosure* cf);
450 
451   // Handles the parallel case for claim_threads_do.
452  private:
453   bool claim_par_threads_do(uintx claim_token);
454  public:
455   // Requires that "claim_token" is that of the current iteration.
456   // If "is_par" is false, sets the token of "this" to
457   // "claim_token", and returns "true".  If "is_par" is true,
458   // uses an atomic instruction to set the current thread's token to
459   // "claim_token", if it is not already.  Returns "true" iff the
460   // calling thread does the update, this indicates that the calling thread
461   // has claimed the thread in the current iteration.
462   bool claim_threads_do(bool is_par, uintx claim_token) {
463     if (!is_par) {
464       _threads_do_token = claim_token;
465       return true;
466     } else {
467       return claim_par_threads_do(claim_token);
468     }
469   }
470 
471   uintx threads_do_token() const { return _threads_do_token; }
472 
473   // jvmtiRedefineClasses support
474   void metadata_handles_do(void f(Metadata*));
475 
476  private:
477   // Check if address is within the given range of this thread's
478   // stack:  stack_base() > adr >/>= limit
479   // The check is inclusive of limit if passed true, else exclusive.
480   bool is_in_stack_range(address adr, address limit, bool inclusive) const {
481     assert(stack_base() > limit && limit >= stack_end(), "limit is outside of stack");
482     return stack_base() > adr && (inclusive ? adr >= limit : adr > limit);
483   }
484 
485  public:
486   // Used by fast lock support
487   virtual bool is_lock_owned(address adr) const;
488 
489   // Check if address is within the given range of this thread's
490   // stack:  stack_base() > adr >= limit
491   bool is_in_stack_range_incl(address adr, address limit) const {
492     return is_in_stack_range(adr, limit, true);
493   }
494 
495   // Check if address is within the given range of this thread's
496   // stack:  stack_base() > adr > limit
497   bool is_in_stack_range_excl(address adr, address limit) const {
498     return is_in_stack_range(adr, limit, false);
499   }
500 
501   // Check if address is in the stack mapped to this thread. Used mainly in
502   // error reporting (so has to include guard zone) and frame printing.
503   // Expects _stack_base to be initialized - checked with assert.
504   bool is_in_full_stack_checked(address adr) const {
505     return is_in_stack_range_incl(adr, stack_end());
506   }
507 
508   // Like is_in_full_stack_checked but without the assertions as this
509   // may be called in a thread before _stack_base is initialized.
510   bool is_in_full_stack(address adr) const {
511     address stack_end = _stack_base - _stack_size;
512     return _stack_base > adr && adr >= stack_end;
513   }
514 
515   // Check if address is in the live stack of this thread (not just for locks).
516   // Warning: can only be called by the current thread on itself.
517   bool is_in_live_stack(address adr) const {
518     assert(Thread::current() == this, "is_in_live_stack can only be called from current thread");
519     return is_in_stack_range_incl(adr, os::current_stack_pointer());
520   }
521 
522   // Sets this thread as starting thread. Returns failure if thread
523   // creation fails due to lack of memory, too many threads etc.
524   bool set_as_starting_thread();
525 
526 protected:
527   // OS data associated with the thread
528   OSThread* _osthread;  // Platform-specific thread information
529 
530   // Thread local resource area for temporary allocation within the VM
531   ResourceArea* _resource_area;
532 
533   DEBUG_ONLY(ResourceMark* _current_resource_mark;)
534 
535   // Thread local handle area for allocation of handles within the VM
536   HandleArea* _handle_area;
537   GrowableArray<Metadata*>* _metadata_handles;
538 
539   // Support for stack overflow handling, get_thread, etc.
540   address          _stack_base;
541   size_t           _stack_size;
542   int              _lgrp_id;
543 
544  public:
545   // Stack overflow support
546   address stack_base() const           { assert(_stack_base != nullptr,"Sanity check"); return _stack_base; }
547   void    set_stack_base(address base) { _stack_base = base; }
548   size_t  stack_size() const           { return _stack_size; }
549   void    set_stack_size(size_t size)  { _stack_size = size; }
550   address stack_end()  const           { return stack_base() - stack_size(); }
551   void    record_stack_base_and_size();
552   void    register_thread_stack_with_NMT();
553   void    unregister_thread_stack_with_NMT();
554 
555   int     lgrp_id() const        { return _lgrp_id; }
556   void    set_lgrp_id(int value) { _lgrp_id = value; }
557 
558   // Printing
559   void print_on(outputStream* st, bool print_extended_info) const;
560   virtual void print_on(outputStream* st) const { print_on(st, false); }
561   void print() const;
562   virtual void print_on_error(outputStream* st, char* buf, int buflen) const;
563   // Basic, non-virtual, printing support that is simple and always safe.
564   void print_value_on(outputStream* st) const;
565 
566   // Debug-only code
567 #ifdef ASSERT
568  private:
569   // Deadlock detection support for Mutex locks. List of locks own by thread.
570   Mutex* _owned_locks;
571   // Mutex::set_owner_implementation is the only place where _owned_locks is modified,
572   // thus the friendship
573   friend class Mutex;
574   friend class Monitor;
575 
576  public:
577   void print_owned_locks_on(outputStream* st) const;
578   void print_owned_locks() const                 { print_owned_locks_on(tty);    }
579   Mutex* owned_locks() const                     { return _owned_locks;          }
580   bool owns_locks() const                        { return owned_locks() != nullptr; }
581 
582   // Deadlock detection
583   ResourceMark* current_resource_mark()          { return _current_resource_mark; }
584   void set_current_resource_mark(ResourceMark* rm) { _current_resource_mark = rm; }
585 #endif // ASSERT
586 
587  private:
588   volatile int _jvmti_env_iteration_count;
589 
590  public:
591   void entering_jvmti_env_iteration()            { ++_jvmti_env_iteration_count; }
592   void leaving_jvmti_env_iteration()             { --_jvmti_env_iteration_count; }
593   bool is_inside_jvmti_env_iteration()           { return _jvmti_env_iteration_count > 0; }
594 
595   // Code generation
596   static ByteSize exception_file_offset()        { return byte_offset_of(Thread, _exception_file); }
597   static ByteSize exception_line_offset()        { return byte_offset_of(Thread, _exception_line); }
598 
599   static ByteSize stack_base_offset()            { return byte_offset_of(Thread, _stack_base); }
600   static ByteSize stack_size_offset()            { return byte_offset_of(Thread, _stack_size); }
601 
602   static ByteSize tlab_start_offset()            { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::start_offset(); }
603   static ByteSize tlab_end_offset()              { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::end_offset(); }
604   static ByteSize tlab_top_offset()              { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::top_offset(); }
605   static ByteSize tlab_pf_top_offset()           { return byte_offset_of(Thread, _tlab) + ThreadLocalAllocBuffer::pf_top_offset(); }
606 
607   static ByteSize allocated_bytes_offset()       { return byte_offset_of(Thread, _allocated_bytes); }
608 
609   JFR_ONLY(DEFINE_THREAD_LOCAL_OFFSET_JFR;)
610 
611  public:
612   ParkEvent * volatile _ParkEvent;            // for Object monitors, JVMTI raw monitors,
613                                               // and ObjectSynchronizer::read_stable_mark
614 
615   // Termination indicator used by the signal handler.
616   // _ParkEvent is just a convenient field we can null out after setting the JavaThread termination state
617   // (which can't itself be read from the signal handler if a signal hits during the Thread destructor).
618   bool has_terminated()                       { return Atomic::load(&_ParkEvent) == nullptr; };
619 
620   jint _hashStateW;                           // Marsaglia Shift-XOR thread-local RNG
621   jint _hashStateX;                           // thread-specific hashCode generator state
622   jint _hashStateY;
623   jint _hashStateZ;
624 
625   // Low-level leaf-lock primitives used to implement synchronization.
626   // Not for general synchronization use.
627   static void SpinAcquire(volatile int * Lock, const char * Name);
628   static void SpinRelease(volatile int * Lock);
629 
630 #if defined(__APPLE__) && defined(AARCH64)
631  private:
632   DEBUG_ONLY(bool _wx_init);
633   WXMode _wx_state;
634  public:
635   void init_wx();
636   WXMode enable_wx(WXMode new_state);
637 
638   void assert_wx_state(WXMode expected) {
639     assert(_wx_state == expected, "wrong state");
640   }
641 #endif // __APPLE__ && AARCH64
642 
643  private:
644   bool _in_asgct = false;
645  public:
646   bool in_asgct() const { return _in_asgct; }
647   void set_in_asgct(bool value) { _in_asgct = value; }
648   static bool current_in_asgct() {
649     Thread *cur = Thread::current_or_null_safe();
650     return cur != nullptr && cur->in_asgct();
651   }
652 
653  private:
654   VMErrorCallback* _vm_error_callbacks;
655 };
656 
657 class ThreadInAsgct {
658  private:
659   Thread* _thread;
660  public:
661   ThreadInAsgct(Thread* thread) : _thread(thread) {
662     assert(thread != nullptr, "invariant");
663     assert(!thread->in_asgct(), "invariant");
664     thread->set_in_asgct(true);
665   }
666   ~ThreadInAsgct() {
667     assert(_thread->in_asgct(), "invariant");
668     _thread->set_in_asgct(false);
669   }
670 };
671 
672 // Inline implementation of Thread::current()
673 inline Thread* Thread::current() {
674   Thread* current = current_or_null();
675   assert(current != nullptr, "Thread::current() called on detached thread");
676   return current;
677 }
678 
679 inline Thread* Thread::current_or_null() {
680 #ifndef USE_LIBRARY_BASED_TLS_ONLY
681   return _thr_current;
682 #else
683   if (ThreadLocalStorage::is_initialized()) {
684     return ThreadLocalStorage::thread();
685   }
686   return nullptr;
687 #endif
688 }
689 
690 inline Thread* Thread::current_or_null_safe() {
691   if (ThreadLocalStorage::is_initialized()) {
692     return ThreadLocalStorage::thread();
693   }
694   return nullptr;
695 }
696 
697 #endif // SHARE_RUNTIME_THREAD_HPP