jdk8-mips64-public/hotspot: src/share/vm/runtime/thread.cpp@dd05dac9563a (annotated)

src/share/vm/runtime/thread.cpp@dd05dac9563a (annotated)

src/share/vm/runtime/thread.cpp

Fri, 27 Mar 2020 19:15:09 +0000

author: andrew
date: Fri, 27 Mar 2020 19:15:09 +0000
changeset 9900: dd05dac9563a
parent 9891: 4904bded9702
parent 9850: 8f2780b3e4fa
child 9903: f37c2dd33031
permissions: -rw-r--r--

Merge

 /*
  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #include "precompiled.hpp"
 #include "classfile/classLoader.hpp"
 #include "classfile/javaClasses.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "classfile/vmSymbols.hpp"
 #include "code/scopeDesc.hpp"
 #include "compiler/compileBroker.hpp"
 #include "interpreter/interpreter.hpp"
 #include "interpreter/linkResolver.hpp"
 #include "interpreter/oopMapCache.hpp"
 #include "jfr/jfrEvents.hpp"
 #include "jvmtifiles/jvmtiEnv.hpp"
 #include "memory/gcLocker.inline.hpp"
 #include "memory/metaspaceShared.hpp"
 #include "memory/oopFactory.hpp"
 #include "memory/universe.inline.hpp"
 #include "oops/instanceKlass.hpp"
 #include "oops/objArrayOop.hpp"
 #include "oops/oop.inline.hpp"
 #include "oops/symbol.hpp"
 #include "prims/jvm_misc.hpp"
 #include "prims/jvmtiExport.hpp"
 #include "prims/jvmtiThreadState.hpp"
 #include "prims/privilegedStack.hpp"
 #include "runtime/arguments.hpp"
 #include "runtime/biasedLocking.hpp"
 #include "runtime/deoptimization.hpp"
 #include "runtime/fprofiler.hpp"
 #include "runtime/frame.inline.hpp"
 #include "runtime/init.hpp"
 #include "runtime/interfaceSupport.hpp"
 #include "runtime/java.hpp"
 #include "runtime/javaCalls.hpp"
 #include "runtime/jniPeriodicChecker.hpp"
 #include "runtime/memprofiler.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/objectMonitor.hpp"
 #include "runtime/orderAccess.inline.hpp"
 #include "runtime/osThread.hpp"
 #include "runtime/safepoint.hpp"
 #include "runtime/sharedRuntime.hpp"
 #include "runtime/statSampler.hpp"
 #include "runtime/stubRoutines.hpp"
 #include "runtime/task.hpp"
 #include "runtime/thread.inline.hpp"
 #include "runtime/threadCritical.hpp"
 #include "runtime/threadLocalStorage.hpp"
 #include "runtime/vframe.hpp"
 #include "runtime/vframeArray.hpp"
 #include "runtime/vframe_hp.hpp"
 #include "runtime/vmThread.hpp"
 #include "runtime/vm_operations.hpp"
 #include "services/attachListener.hpp"
 #include "services/management.hpp"
 #include "services/memTracker.hpp"
 #include "services/threadService.hpp"
 #include "utilities/defaultStream.hpp"
 #include "utilities/dtrace.hpp"
 #include "utilities/events.hpp"
 #include "utilities/preserveException.hpp"
 #include "utilities/macros.hpp"
 #ifdef TARGET_OS_FAMILY_linux
 # include "os_linux.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_solaris
 # include "os_solaris.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_windows
 # include "os_windows.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_bsd
 # include "os_bsd.inline.hpp"
 #endif
 #if INCLUDE_ALL_GCS
 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
 #endif // INCLUDE_ALL_GCS
 #ifdef COMPILER1
 #include "c1/c1_Compiler.hpp"
 #endif
 #ifdef COMPILER2
 #include "opto/c2compiler.hpp"
 #include "opto/idealGraphPrinter.hpp"
 #endif
 #if INCLUDE_RTM_OPT
 #include "runtime/rtmLocking.hpp"
 #endif
 #if INCLUDE_JFR
 #include "jfr/jfr.hpp"
 #endif
 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
 #ifdef DTRACE_ENABLED
 // Only bother with this argument setup if dtrace is available
 #ifndef USDT2
 HS_DTRACE_PROBE_DECL(hotspot, vm__init__begin);
 HS_DTRACE_PROBE_DECL(hotspot, vm__init__end);
 HS_DTRACE_PROBE_DECL5(hotspot, thread__start, char*, intptr_t,
   intptr_t, intptr_t, bool);
 HS_DTRACE_PROBE_DECL5(hotspot, thread__stop, char*, intptr_t,
   intptr_t, intptr_t, bool);
 #define DTRACE_THREAD_PROBE(probe, javathread)                             \
   {                                                                        \
     ResourceMark rm(this);                                                 \
     int len = 0;                                                           \
     const char* name = (javathread)->get_thread_name();                    \
     len = strlen(name);                                                    \
     HS_DTRACE_PROBE5(hotspot, thread__##probe,                             \
       name, len,                                                           \
       java_lang_Thread::thread_id((javathread)->threadObj()),              \
       (javathread)->osthread()->thread_id(),                               \
       java_lang_Thread::is_daemon((javathread)->threadObj()));             \
   }
 #else /* USDT2 */
 #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 #define DTRACE_THREAD_PROBE(probe, javathread)                             \
   {                                                                        \
     ResourceMark rm(this);                                                 \
     int len = 0;                                                           \
     const char* name = (javathread)->get_thread_name();                    \
     len = strlen(name);                                                    \
     HOTSPOT_THREAD_PROBE_##probe(  /* probe = start, stop */               \
       (char *) name, len,                                                           \
       java_lang_Thread::thread_id((javathread)->threadObj()),              \
       (uintptr_t) (javathread)->osthread()->thread_id(),                               \
       java_lang_Thread::is_daemon((javathread)->threadObj()));             \
   }
 #endif /* USDT2 */
 #else //  ndef DTRACE_ENABLED
 #define DTRACE_THREAD_PROBE(probe, javathread)
 #endif // ndef DTRACE_ENABLED
 // Class hierarchy
 // - Thread
 //   - VMThread
 //   - WatcherThread
 //   - ConcurrentMarkSweepThread
 //   - JavaThread
 //     - CompilerThread
 // ======= Thread ========
 // Support for forcing alignment of thread objects for biased locking
 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
   if (UseBiasedLocking) {
     const int alignment = markOopDesc::biased_lock_alignment;
     size_t aligned_size = size + (alignment - sizeof(intptr_t));
     void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
                                           : AllocateHeap(aligned_size, flags, CURRENT_PC,
                                               AllocFailStrategy::RETURN_NULL);
     void* aligned_addr     = (void*) align_size_up((intptr_t) real_malloc_addr, alignment);
     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
            "JavaThread alignment code overflowed allocated storage");
     if (TraceBiasedLocking) {
       if (aligned_addr != real_malloc_addr)
         tty->print_cr("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
                       real_malloc_addr, aligned_addr);
     }
     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
     return aligned_addr;
   } else {
     return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
                        : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
   }
 }
 void Thread::operator delete(void* p) {
   if (UseBiasedLocking) {
     void* real_malloc_addr = ((Thread*) p)->_real_malloc_address;
     FreeHeap(real_malloc_addr, mtThread);
   } else {
     FreeHeap(p, mtThread);
   }
 }
 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 // JavaThread
 Thread::Thread() {
   // stack and get_thread
   set_stack_base(NULL);
   set_stack_size(0);
   set_self_raw_id(0);
   set_lgrp_id(-1);
   // allocated data structures
   set_osthread(NULL);
   set_resource_area(new (mtThread)ResourceArea());
   DEBUG_ONLY(_current_resource_mark = NULL;)
   set_handle_area(new (mtThread) HandleArea(NULL));
   set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
   set_active_handles(NULL);
   set_free_handle_block(NULL);
   set_last_handle_mark(NULL);
   // This initial value ==> never claimed.
   _oops_do_parity = 0;
   _metadata_on_stack_buffer = NULL;
   // the handle mark links itself to last_handle_mark
   new HandleMark(this);
   // plain initialization
   debug_only(_owned_locks = NULL;)
   debug_only(_allow_allocation_count = 0;)
   NOT_PRODUCT(_allow_safepoint_count = 0;)
   NOT_PRODUCT(_skip_gcalot = false;)
   _jvmti_env_iteration_count = 0;
   set_allocated_bytes(0);
   _vm_operation_started_count = 0;
   _vm_operation_completed_count = 0;
   _current_pending_monitor = NULL;
   _current_pending_monitor_is_from_java = true;
   _current_waiting_monitor = NULL;
   _num_nested_signal = 0;
   omFreeList = NULL ;
   omFreeCount = 0 ;
   omFreeProvision = 32 ;
   omInUseList = NULL ;
   omInUseCount = 0 ;
 #ifdef ASSERT
   _visited_for_critical_count = false;
 #endif
   _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true);
   _suspend_flags = 0;
   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
   _hashStateX = os::random() ;
   _hashStateY = 842502087 ;
   _hashStateZ = 0x8767 ;    // (int)(3579807591LL & 0xffff) ;
   _hashStateW = 273326509 ;
   _OnTrap   = 0 ;
   _schedctl = NULL ;
   _Stalled  = 0 ;
   _TypeTag  = 0x2BAD ;
   // Many of the following fields are effectively final - immutable
   // Note that nascent threads can't use the Native Monitor-Mutex
   // construct until the _MutexEvent is initialized ...
   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
   // we might instead use a stack of ParkEvents that we could provision on-demand.
   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
   // and ::Release()
   _ParkEvent   = ParkEvent::Allocate (this) ;
   _SleepEvent  = ParkEvent::Allocate (this) ;
   _MutexEvent  = ParkEvent::Allocate (this) ;
   _MuxEvent    = ParkEvent::Allocate (this) ;
 #ifdef CHECK_UNHANDLED_OOPS
   if (CheckUnhandledOops) {
     _unhandled_oops = new UnhandledOops(this);
   }
 #endif // CHECK_UNHANDLED_OOPS
 #ifdef ASSERT
   if (UseBiasedLocking) {
     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
     assert(this == _real_malloc_address ||
            this == (void*) align_size_up((intptr_t) _real_malloc_address, markOopDesc::biased_lock_alignment),
            "bug in forced alignment of thread objects");
   }
 #endif /* ASSERT */
 }
 void Thread::initialize_thread_local_storage() {
   // Note: Make sure this method only calls
   // non-blocking operations. Otherwise, it might not work
   // with the thread-startup/safepoint interaction.
   // During Java thread startup, safepoint code should allow this
   // method to complete because it may need to allocate memory to
   // store information for the new thread.
   // initialize structure dependent on thread local storage
   ThreadLocalStorage::set_thread(this);
 }
 void Thread::record_stack_base_and_size() {
   set_stack_base(os::current_stack_base());
   set_stack_size(os::current_stack_size());
   if (is_Java_thread()) {
     ((JavaThread*) this)->set_stack_overflow_limit();
   }
   // CR 7190089: on Solaris, primordial thread's stack is adjusted
   // in initialize_thread(). Without the adjustment, stack size is
   // incorrect if stack is set to unlimited (ulimit -s unlimited).
   // So far, only Solaris has real implementation of initialize_thread().
   //
   // set up any platform-specific state.
   os::initialize_thread(this);
 #if INCLUDE_NMT
   // record thread's native stack, stack grows downward
   address stack_low_addr = stack_base() - stack_size();
   MemTracker::record_thread_stack(stack_low_addr, stack_size());
 #endif // INCLUDE_NMT
 }
 Thread::~Thread() {
   // Reclaim the objectmonitors from the omFreeList of the moribund thread.
   ObjectSynchronizer::omFlush (this) ;
   // stack_base can be NULL if the thread is never started or exited before
   // record_stack_base_and_size called. Although, we would like to ensure
   // that all started threads do call record_stack_base_and_size(), there is
   // not proper way to enforce that.
 #if INCLUDE_NMT
   if (_stack_base != NULL) {
     address low_stack_addr = stack_base() - stack_size();
     MemTracker::release_thread_stack(low_stack_addr, stack_size());
 #ifdef ASSERT
     set_stack_base(NULL);
 #endif
   }
 #endif // INCLUDE_NMT
   // deallocate data structures
   delete resource_area();
   // since the handle marks are using the handle area, we have to deallocated the root
   // handle mark before deallocating the thread's handle area,
   assert(last_handle_mark() != NULL, "check we have an element");
   delete last_handle_mark();
   assert(last_handle_mark() == NULL, "check we have reached the end");
   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
   // We NULL out the fields for good hygiene.
   ParkEvent::Release (_ParkEvent)   ; _ParkEvent   = NULL ;
   ParkEvent::Release (_SleepEvent)  ; _SleepEvent  = NULL ;
   ParkEvent::Release (_MutexEvent)  ; _MutexEvent  = NULL ;
   ParkEvent::Release (_MuxEvent)    ; _MuxEvent    = NULL ;
   delete handle_area();
   delete metadata_handles();
   // osthread() can be NULL, if creation of thread failed.
   if (osthread() != NULL) os::free_thread(osthread());
   delete _SR_lock;
   // clear thread local storage if the Thread is deleting itself
   if (this == Thread::current()) {
     ThreadLocalStorage::set_thread(NULL);
   } else {
     // In the case where we're not the current thread, invalidate all the
     // caches in case some code tries to get the current thread or the
     // thread that was destroyed, and gets stale information.
     ThreadLocalStorage::invalidate_all();
   }
   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 }
 // NOTE: dummy function for assertion purpose.
 void Thread::run() {
   ShouldNotReachHere();
 }
 #ifdef ASSERT
 // Private method to check for dangling thread pointer
 void check_for_dangling_thread_pointer(Thread *thread) {
  assert(!thread->is_Java_thread() || Thread::current() == thread || Threads_lock->owned_by_self(),
          "possibility of dangling Thread pointer");
 }
 #endif
 #ifndef PRODUCT
 // Tracing method for basic thread operations
 void Thread::trace(const char* msg, const Thread* const thread) {
   if (!TraceThreadEvents) return;
   ResourceMark rm;
   ThreadCritical tc;
   const char *name = "non-Java thread";
   int prio = -1;
   if (thread->is_Java_thread()
       && !thread->is_Compiler_thread()) {
     // The Threads_lock must be held to get information about
     // this thread but may not be in some situations when
     // tracing  thread events.
     bool release_Threads_lock = false;
     if (!Threads_lock->owned_by_self()) {
       Threads_lock->lock();
       release_Threads_lock = true;
     }
     JavaThread* jt = (JavaThread *)thread;
     name = (char *)jt->get_thread_name();
     oop thread_oop = jt->threadObj();
     if (thread_oop != NULL) {
       prio = java_lang_Thread::priority(thread_oop);
     }
     if (release_Threads_lock) {
       Threads_lock->unlock();
     }
   }
   tty->print_cr("Thread::%s " INTPTR_FORMAT " [%lx] %s (prio: %d)", msg, thread, thread->osthread()->thread_id(), name, prio);
 }
 #endif
 ThreadPriority Thread::get_priority(const Thread* const thread) {
   trace("get priority", thread);
   ThreadPriority priority;
   // Can return an error!
   (void)os::get_priority(thread, priority);
   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
   return priority;
 }
 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
   trace("set priority", thread);
   debug_only(check_for_dangling_thread_pointer(thread);)
   // Can return an error!
   (void)os::set_priority(thread, priority);
 }
 void Thread::start(Thread* thread) {
   trace("start", thread);
   // Start is different from resume in that its safety is guaranteed by context or
   // being called from a Java method synchronized on the Thread object.
   if (!DisableStartThread) {
     if (thread->is_Java_thread()) {
       // Initialize the thread state to RUNNABLE before starting this thread.
       // Can not set it after the thread started because we do not know the
       // exact thread state at that time. It could be in MONITOR_WAIT or
       // in SLEEPING or some other state.
       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
                                           java_lang_Thread::RUNNABLE);
     }
     os::start_thread(thread);
   }
 }
 // Enqueue a VM_Operation to do the job for us - sometime later
 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
   VMThread::execute(vm_stop);
 }
 //
 // Check if an external suspend request has completed (or has been
 // cancelled). Returns true if the thread is externally suspended and
 // false otherwise.
 //
 // The bits parameter returns information about the code path through
 // the routine. Useful for debugging:
 //
 // set in is_ext_suspend_completed():
 // 0x00000001 - routine was entered
 // 0x00000010 - routine return false at end
 // 0x00000100 - thread exited (return false)
 // 0x00000200 - suspend request cancelled (return false)
 // 0x00000400 - thread suspended (return true)
 // 0x00001000 - thread is in a suspend equivalent state (return true)
 // 0x00002000 - thread is native and walkable (return true)
 // 0x00004000 - thread is native_trans and walkable (needed retry)
 //
 // set in wait_for_ext_suspend_completion():
 // 0x00010000 - routine was entered
 // 0x00020000 - suspend request cancelled before loop (return false)
 // 0x00040000 - thread suspended before loop (return true)
 // 0x00080000 - suspend request cancelled in loop (return false)
 // 0x00100000 - thread suspended in loop (return true)
 // 0x00200000 - suspend not completed during retry loop (return false)
 //
 // Helper class for tracing suspend wait debug bits.
 //
 // 0x00000100 indicates that the target thread exited before it could
 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 // 0x00080000 each indicate a cancelled suspend request so they don't
 // count as wait failures either.
 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 class TraceSuspendDebugBits : public StackObj {
  private:
   JavaThread * jt;
   bool         is_wait;
   bool         called_by_wait;  // meaningful when !is_wait
   uint32_t *   bits;
  public:
   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
                         uint32_t *_bits) {
     jt             = _jt;
     is_wait        = _is_wait;
     called_by_wait = _called_by_wait;
     bits           = _bits;
   }
   ~TraceSuspendDebugBits() {
     if (!is_wait) {
 #if 1
       // By default, don't trace bits for is_ext_suspend_completed() calls.
       // That trace is very chatty.
       return;
 #else
       if (!called_by_wait) {
         // If tracing for is_ext_suspend_completed() is enabled, then only
         // trace calls to it from wait_for_ext_suspend_completion()
         return;
       }
 #endif
     }
     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
         ResourceMark rm;
         tty->print_cr(
             "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
             jt->get_thread_name(), *bits);
         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
       }
     }
   }
 };
 #undef DEBUG_FALSE_BITS
 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay, uint32_t *bits) {
   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
   bool do_trans_retry;           // flag to force the retry
   *bits |= 0x00000001;
   do {
     do_trans_retry = false;
     if (is_exiting()) {
       // Thread is in the process of exiting. This is always checked
       // first to reduce the risk of dereferencing a freed JavaThread.
       *bits |= 0x00000100;
       return false;
     }
     if (!is_external_suspend()) {
       // Suspend request is cancelled. This is always checked before
       // is_ext_suspended() to reduce the risk of a rogue resume
       // confusing the thread that made the suspend request.
       *bits |= 0x00000200;
       return false;
     }
     if (is_ext_suspended()) {
       // thread is suspended
       *bits |= 0x00000400;
       return true;
     }
     // Now that we no longer do hard suspends of threads running
     // native code, the target thread can be changing thread state
     // while we are in this routine:
     //
     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
     //
     // We save a copy of the thread state as observed at this moment
     // and make our decision about suspend completeness based on the
     // copy. This closes the race where the thread state is seen as
     // _thread_in_native_trans in the if-thread_blocked check, but is
     // seen as _thread_blocked in if-thread_in_native_trans check.
     JavaThreadState save_state = thread_state();
     if (save_state == _thread_blocked && is_suspend_equivalent()) {
       // If the thread's state is _thread_blocked and this blocking
       // condition is known to be equivalent to a suspend, then we can
       // consider the thread to be externally suspended. This means that
       // the code that sets _thread_blocked has been modified to do
       // self-suspension if the blocking condition releases. We also
       // used to check for CONDVAR_WAIT here, but that is now covered by
       // the _thread_blocked with self-suspension check.
       //
       // Return true since we wouldn't be here unless there was still an
       // external suspend request.
       *bits |= 0x00001000;
       return true;
     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
       // Threads running native code will self-suspend on native==>VM/Java
       // transitions. If its stack is walkable (should always be the case
       // unless this function is called before the actual java_suspend()
       // call), then the wait is done.
       *bits |= 0x00002000;
       return true;
     } else if (!called_by_wait && !did_trans_retry &&
                save_state == _thread_in_native_trans &&
                frame_anchor()->walkable()) {
       // The thread is transitioning from thread_in_native to another
       // thread state. check_safepoint_and_suspend_for_native_trans()
       // will force the thread to self-suspend. If it hasn't gotten
       // there yet we may have caught the thread in-between the native
       // code check above and the self-suspend. Lucky us. If we were
       // called by wait_for_ext_suspend_completion(), then it
       // will be doing the retries so we don't have to.
       //
       // Since we use the saved thread state in the if-statement above,
       // there is a chance that the thread has already transitioned to
       // _thread_blocked by the time we get here. In that case, we will
       // make a single unnecessary pass through the logic below. This
       // doesn't hurt anything since we still do the trans retry.
       *bits |= 0x00004000;
       // Once the thread leaves thread_in_native_trans for another
       // thread state, we break out of this retry loop. We shouldn't
       // need this flag to prevent us from getting back here, but
       // sometimes paranoia is good.
       did_trans_retry = true;
       // We wait for the thread to transition to a more usable state.
       for (int i = 1; i <= SuspendRetryCount; i++) {
         // We used to do an "os::yield_all(i)" call here with the intention
         // that yielding would increase on each retry. However, the parameter
         // is ignored on Linux which means the yield didn't scale up. Waiting
         // on the SR_lock below provides a much more predictable scale up for
         // the delay. It also provides a simple/direct point to check for any
         // safepoint requests from the VMThread
         // temporarily drops SR_lock while doing wait with safepoint check
         // (if we're a JavaThread - the WatcherThread can also call this)
         // and increase delay with each retry
         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
         // check the actual thread state instead of what we saved above
         if (thread_state() != _thread_in_native_trans) {
           // the thread has transitioned to another thread state so
           // try all the checks (except this one) one more time.
           do_trans_retry = true;
           break;
         }
       } // end retry loop
     }
   } while (do_trans_retry);
   *bits |= 0x00000010;
   return false;
 }
 //
 // Wait for an external suspend request to complete (or be cancelled).
 // Returns true if the thread is externally suspended and false otherwise.
 //
 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
        uint32_t *bits) {
   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
                              false /* !called_by_wait */, bits);
   // local flag copies to minimize SR_lock hold time
   bool is_suspended;
   bool pending;
   uint32_t reset_bits;
   // set a marker so is_ext_suspend_completed() knows we are the caller
   *bits |= 0x00010000;
   // We use reset_bits to reinitialize the bits value at the top of
   // each retry loop. This allows the caller to make use of any
   // unused bits for their own marking purposes.
   reset_bits = *bits;
   {
     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
                                             delay, bits);
     pending = is_external_suspend();
   }
   // must release SR_lock to allow suspension to complete
   if (!pending) {
     // A cancelled suspend request is the only false return from
     // is_ext_suspend_completed() that keeps us from entering the
     // retry loop.
     *bits |= 0x00020000;
     return false;
   }
   if (is_suspended) {
     *bits |= 0x00040000;
     return true;
   }
   for (int i = 1; i <= retries; i++) {
     *bits = reset_bits;  // reinit to only track last retry
     // We used to do an "os::yield_all(i)" call here with the intention
     // that yielding would increase on each retry. However, the parameter
     // is ignored on Linux which means the yield didn't scale up. Waiting
     // on the SR_lock below provides a much more predictable scale up for
     // the delay. It also provides a simple/direct point to check for any
     // safepoint requests from the VMThread
     {
       MutexLocker ml(SR_lock());
       // wait with safepoint check (if we're a JavaThread - the WatcherThread
       // can also call this)  and increase delay with each retry
       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
                                               delay, bits);
       // It is possible for the external suspend request to be cancelled
       // (by a resume) before the actual suspend operation is completed.
       // Refresh our local copy to see if we still need to wait.
       pending = is_external_suspend();
     }
     if (!pending) {
       // A cancelled suspend request is the only false return from
       // is_ext_suspend_completed() that keeps us from staying in the
       // retry loop.
       *bits |= 0x00080000;
       return false;
     }
     if (is_suspended) {
       *bits |= 0x00100000;
       return true;
     }
   } // end retry loop
   // thread did not suspend after all our retries
   *bits |= 0x00200000;
   return false;
 }
 #ifndef PRODUCT
 void JavaThread::record_jump(address target, address instr, const char* file, int line) {
   // This should not need to be atomic as the only way for simultaneous
   // updates is via interrupts. Even then this should be rare or non-existant
   // and we don't care that much anyway.
   int index = _jmp_ring_index;
   _jmp_ring_index = (index + 1 ) & (jump_ring_buffer_size - 1);
   _jmp_ring[index]._target = (intptr_t) target;
   _jmp_ring[index]._instruction = (intptr_t) instr;
   _jmp_ring[index]._file = file;
   _jmp_ring[index]._line = line;
 }
 #endif /* PRODUCT */
 // Called by flat profiler
 // Callers have already called wait_for_ext_suspend_completion
 // The assertion for that is currently too complex to put here:
 bool JavaThread::profile_last_Java_frame(frame* _fr) {
   bool gotframe = false;
   // self suspension saves needed state.
   if (has_last_Java_frame() && _anchor.walkable()) {
      *_fr = pd_last_frame();
      gotframe = true;
   }
   return gotframe;
 }
 void Thread::interrupt(Thread* thread) {
   trace("interrupt", thread);
   debug_only(check_for_dangling_thread_pointer(thread);)
   os::interrupt(thread);
 }
 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
   trace("is_interrupted", thread);
   debug_only(check_for_dangling_thread_pointer(thread);)
   // Note:  If clear_interrupted==false, this simply fetches and
   // returns the value of the field osthread()->interrupted().
   return os::is_interrupted(thread, clear_interrupted);
 }
 // GC Support
 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
   jint thread_parity = _oops_do_parity;
   if (thread_parity != strong_roots_parity) {
     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
     if (res == thread_parity) {
       return true;
     } else {
       guarantee(res == strong_roots_parity, "Or else what?");
       assert(SharedHeap::heap()->workers()->active_workers() > 0,
          "Should only fail when parallel.");
       return false;
     }
   }
   assert(SharedHeap::heap()->workers()->active_workers() > 0,
          "Should only fail when parallel.");
   return false;
 }
 void Thread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
   if (active_handles() != NULL) {
     active_handles()->oops_do(f);
   }
   // Do oop for ThreadShadow
   f->do_oop((oop*)&_pending_exception);
   handle_area()->oops_do(f);
 }
 void Thread::nmethods_do(CodeBlobClosure* cf) {
   // no nmethods in a generic thread...
 }
 void Thread::metadata_do(void f(Metadata*)) {
   if (metadata_handles() != NULL) {
     for (int i = 0; i< metadata_handles()->length(); i++) {
       f(metadata_handles()->at(i));
     }
   }
 }
 void Thread::print_on(outputStream* st) const {
   // get_priority assumes osthread initialized
   if (osthread() != NULL) {
     int os_prio;
     if (os::get_native_priority(this, &os_prio) == OS_OK) {
       st->print("os_prio=%d ", os_prio);
     }
     st->print("tid=" INTPTR_FORMAT " ", this);
     ext().print_on(st);
     osthread()->print_on(st);
   }
   debug_only(if (WizardMode) print_owned_locks_on(st);)
 }
 // Thread::print_on_error() is called by fatal error handler. Don't use
 // any lock or allocate memory.
 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
   if      (is_VM_thread())                  st->print("VMThread");
   else if (is_Compiler_thread())            st->print("CompilerThread");
   else if (is_Java_thread())                st->print("JavaThread");
   else if (is_GC_task_thread())             st->print("GCTaskThread");
   else if (is_Watcher_thread())             st->print("WatcherThread");
   else if (is_ConcurrentGC_thread())        st->print("ConcurrentGCThread");
   else st->print("Thread");
   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
             _stack_base - _stack_size, _stack_base);
   if (osthread()) {
     st->print(" [id=%d]", osthread()->thread_id());
   }
 }
 #ifdef ASSERT
 void Thread::print_owned_locks_on(outputStream* st) const {
   Monitor *cur = _owned_locks;
   if (cur == NULL) {
     st->print(" (no locks) ");
   } else {
     st->print_cr(" Locks owned:");
     while(cur) {
       cur->print_on(st);
       cur = cur->next();
     }
   }
 }
 static int ref_use_count  = 0;
 bool Thread::owns_locks_but_compiled_lock() const {
   for(Monitor *cur = _owned_locks; cur; cur = cur->next()) {
     if (cur != Compile_lock) return true;
   }
   return false;
 }
 #endif
 #ifndef PRODUCT
 // The flag: potential_vm_operation notifies if this particular safepoint state could potential
 // invoke the vm-thread (i.e., and oop allocation). In that case, we also have to make sure that
 // no threads which allow_vm_block's are held
 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
     // Check if current thread is allowed to block at a safepoint
     if (!(_allow_safepoint_count == 0))
       fatal("Possible safepoint reached by thread that does not allow it");
     if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
       fatal("LEAF method calling lock?");
     }
 #ifdef ASSERT
     if (potential_vm_operation && is_Java_thread()
         && !Universe::is_bootstrapping()) {
       // Make sure we do not hold any locks that the VM thread also uses.
       // This could potentially lead to deadlocks
       for(Monitor *cur = _owned_locks; cur; cur = cur->next()) {
         // Threads_lock is special, since the safepoint synchronization will not start before this is
         // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
         // since it is used to transfer control between JavaThreads and the VMThread
         // Do not *exclude* any locks unless you are absolutly sure it is correct. Ask someone else first!
         if ( (cur->allow_vm_block() &&
               cur != Threads_lock &&
               cur != Compile_lock &&               // Temporary: should not be necessary when we get spearate compilation
               cur != VMOperationRequest_lock &&
               cur != VMOperationQueue_lock) ||
               cur->rank() == Mutex::special) {
           fatal(err_msg("Thread holding lock at safepoint that vm can block on: %s", cur->name()));
         }
       }
     }
     if (GCALotAtAllSafepoints) {
       // We could enter a safepoint here and thus have a gc
       InterfaceSupport::check_gc_alot();
     }
 #endif
 }
 #endif
 bool Thread::is_in_stack(address adr) const {
   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
   address end = os::current_stack_pointer();
   // Allow non Java threads to call this without stack_base
   if (_stack_base == NULL) return true;
   if (stack_base() >= adr && adr >= end) return true;
   return false;
 }
 bool Thread::is_in_usable_stack(address adr) const {
   size_t stack_guard_size = os::uses_stack_guard_pages() ? (StackYellowPages + StackRedPages) * os::vm_page_size() : 0;
   size_t usable_stack_size = _stack_size - stack_guard_size;
   return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
 }
 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
 // used for compilation in the future. If that change is made, the need for these methods
 // should be revisited, and they should be removed if possible.
 bool Thread::is_lock_owned(address adr) const {
   return on_local_stack(adr);
 }
 bool Thread::set_as_starting_thread() {
  // NOTE: this must be called inside the main thread.
   return os::create_main_thread((JavaThread*)this);
 }
 static void initialize_class(Symbol* class_name, TRAPS) {
   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
   InstanceKlass::cast(klass)->initialize(CHECK);
 }
 // Creates the initial ThreadGroup
 static Handle create_initial_thread_group(TRAPS) {
   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_ThreadGroup(), true, CHECK_NH);
   instanceKlassHandle klass (THREAD, k);
   Handle system_instance = klass->allocate_instance_handle(CHECK_NH);
   {
     JavaValue result(T_VOID);
     JavaCalls::call_special(&result,
                             system_instance,
                             klass,
                             vmSymbols::object_initializer_name(),
                             vmSymbols::void_method_signature(),
                             CHECK_NH);
   }
   Universe::set_system_thread_group(system_instance());
   Handle main_instance = klass->allocate_instance_handle(CHECK_NH);
   {
     JavaValue result(T_VOID);
     Handle string = java_lang_String::create_from_str("main", CHECK_NH);
     JavaCalls::call_special(&result,
                             main_instance,
                             klass,
                             vmSymbols::object_initializer_name(),
                             vmSymbols::threadgroup_string_void_signature(),
                             system_instance,
                             string,
                             CHECK_NH);
   }
   return main_instance;
 }
 // Creates the initial Thread
 static oop create_initial_thread(Handle thread_group, JavaThread* thread, TRAPS) {
   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
   instanceKlassHandle klass (THREAD, k);
   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);
   java_lang_Thread::set_thread(thread_oop(), thread);
   java_lang_Thread::set_priority(thread_oop(), NormPriority);
   thread->set_threadObj(thread_oop());
   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
   JavaValue result(T_VOID);
   JavaCalls::call_special(&result, thread_oop,
                                    klass,
                                    vmSymbols::object_initializer_name(),
                                    vmSymbols::threadgroup_string_void_signature(),
                                    thread_group,
                                    string,
                                    CHECK_NULL);
   return thread_oop();
 }
 static void call_initializeSystemClass(TRAPS) {
   Klass* k =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
   instanceKlassHandle klass (THREAD, k);
   JavaValue result(T_VOID);
   JavaCalls::call_static(&result, klass, vmSymbols::initializeSystemClass_name(),
                                          vmSymbols::void_method_signature(), CHECK);
 }
 char java_runtime_name[128] = "";
 char java_runtime_version[128] = "";
 // extract the JRE name from sun.misc.Version.java_runtime_name
 static const char* get_java_runtime_name(TRAPS) {
   Klass* k = SystemDictionary::find(vmSymbols::sun_misc_Version(),
                                       Handle(), Handle(), CHECK_AND_CLEAR_NULL);
   fieldDescriptor fd;
   bool found = k != NULL &&
                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
                                                         vmSymbols::string_signature(), &fd);
   if (found) {
     oop name_oop = k->java_mirror()->obj_field(fd.offset());
     if (name_oop == NULL)
       return NULL;
     const char* name = java_lang_String::as_utf8_string(name_oop,
                                                         java_runtime_name,
                                                         sizeof(java_runtime_name));
     return name;
   } else {
     return NULL;
   }
 }
 // extract the JRE version from sun.misc.Version.java_runtime_version
 static const char* get_java_runtime_version(TRAPS) {
   Klass* k = SystemDictionary::find(vmSymbols::sun_misc_Version(),
                                       Handle(), Handle(), CHECK_AND_CLEAR_NULL);
   fieldDescriptor fd;
   bool found = k != NULL &&
                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
                                                         vmSymbols::string_signature(), &fd);
   if (found) {
     oop name_oop = k->java_mirror()->obj_field(fd.offset());
     if (name_oop == NULL)
       return NULL;
     const char* name = java_lang_String::as_utf8_string(name_oop,
                                                         java_runtime_version,
                                                         sizeof(java_runtime_version));
     return name;
   } else {
     return NULL;
   }
 }
 // General purpose hook into Java code, run once when the VM is initialized.
 // The Java library method itself may be changed independently from the VM.
 static void call_postVMInitHook(TRAPS) {
   Klass* k = SystemDictionary::resolve_or_null(vmSymbols::sun_misc_PostVMInitHook(), THREAD);
   instanceKlassHandle klass (THREAD, k);
   if (klass.not_null()) {
     JavaValue result(T_VOID);
     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
                                            vmSymbols::void_method_signature(),
                                            CHECK);
   }
 }
 static void reset_vm_info_property(TRAPS) {
   // the vm info string
   ResourceMark rm(THREAD);
   const char *vm_info = VM_Version::vm_info_string();
   // java.lang.System class
   Klass* k =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
   instanceKlassHandle klass (THREAD, k);
   // setProperty arguments
   Handle key_str    = java_lang_String::create_from_str("java.vm.info", CHECK);
   Handle value_str  = java_lang_String::create_from_str(vm_info, CHECK);
   // return value
   JavaValue r(T_OBJECT);
   // public static String setProperty(String key, String value);
   JavaCalls::call_static(&r,
                          klass,
                          vmSymbols::setProperty_name(),
                          vmSymbols::string_string_string_signature(),
                          key_str,
                          value_str,
                          CHECK);
 }
 void JavaThread::allocate_threadObj(Handle thread_group, char* thread_name, bool daemon, TRAPS) {
   assert(thread_group.not_null(), "thread group should be specified");
   assert(threadObj() == NULL, "should only create Java thread object once");
   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);
   instanceKlassHandle klass (THREAD, k);
   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
   java_lang_Thread::set_thread(thread_oop(), this);
   java_lang_Thread::set_priority(thread_oop(), NormPriority);
   set_threadObj(thread_oop());
   JavaValue result(T_VOID);
   if (thread_name != NULL) {
     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
     // Thread gets assigned specified name and null target
     JavaCalls::call_special(&result,
                             thread_oop,
                             klass,
                             vmSymbols::object_initializer_name(),
                             vmSymbols::threadgroup_string_void_signature(),
                             thread_group, // Argument 1
                             name,         // Argument 2
                             THREAD);
   } else {
     // Thread gets assigned name "Thread-nnn" and null target
     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
     JavaCalls::call_special(&result,
                             thread_oop,
                             klass,
                             vmSymbols::object_initializer_name(),
                             vmSymbols::threadgroup_runnable_void_signature(),
                             thread_group, // Argument 1
                             Handle(),     // Argument 2
                             THREAD);
   }
   if (daemon) {
       java_lang_Thread::set_daemon(thread_oop());
   }
   if (HAS_PENDING_EXCEPTION) {
     return;
   }
   KlassHandle group(this, SystemDictionary::ThreadGroup_klass());
   Handle threadObj(this, this->threadObj());
   JavaCalls::call_special(&result,
                          thread_group,
                          group,
                          vmSymbols::add_method_name(),
                          vmSymbols::thread_void_signature(),
                          threadObj,          // Arg 1
                          THREAD);
 }
 // NamedThread --  non-JavaThread subclasses with multiple
 // uniquely named instances should derive from this.
 NamedThread::NamedThread() : Thread() {
   _name = NULL;
   _processed_thread = NULL;
 }
 NamedThread::~NamedThread() {
   JFR_ONLY(Jfr::on_thread_exit(this);)
   if (_name != NULL) {
     FREE_C_HEAP_ARRAY(char, _name, mtThread);
     _name = NULL;
   }
 }
 void NamedThread::set_name(const char* format, ...) {
   guarantee(_name == NULL, "Only get to set name once.");
   _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
   guarantee(_name != NULL, "alloc failure");
   va_list ap;
   va_start(ap, format);
   jio_vsnprintf(_name, max_name_len, format, ap);
   va_end(ap);
 }
 // ======= WatcherThread ========
 // The watcher thread exists to simulate timer interrupts.  It should
 // be replaced by an abstraction over whatever native support for
 // timer interrupts exists on the platform.
 WatcherThread* WatcherThread::_watcher_thread   = NULL;
 bool WatcherThread::_startable = false;
 volatile bool  WatcherThread::_should_terminate = false;
 WatcherThread::WatcherThread() : Thread() {
   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
   if (os::create_thread(this, os::watcher_thread)) {
     _watcher_thread = this;
     // Set the watcher thread to the highest OS priority which should not be
     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
     // is created. The only normal thread using this priority is the reference
     // handler thread, which runs for very short intervals only.
     // If the VMThread's priority is not lower than the WatcherThread profiling
     // will be inaccurate.
     os::set_priority(this, MaxPriority);
     if (!DisableStartThread) {
       os::start_thread(this);
     }
   }
 }
 int WatcherThread::sleep() const {
   MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
   // remaining will be zero if there are no tasks,
   // causing the WatcherThread to sleep until a task is
   // enrolled
   int remaining = PeriodicTask::time_to_wait();
   int time_slept = 0;
   // we expect this to timeout - we only ever get unparked when
   // we should terminate or when a new task has been enrolled
   OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
   jlong time_before_loop = os::javaTimeNanos();
   for (;;) {
     bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag, remaining);
     jlong now = os::javaTimeNanos();
     if (remaining == 0) {
         // if we didn't have any tasks we could have waited for a long time
         // consider the time_slept zero and reset time_before_loop
         time_slept = 0;
         time_before_loop = now;
     } else {
         // need to recalulate since we might have new tasks in _tasks
         time_slept = (int) ((now - time_before_loop) / 1000000);
     }
     // Change to task list or spurious wakeup of some kind
     if (timedout || _should_terminate) {
         break;
     }
     remaining = PeriodicTask::time_to_wait();
     if (remaining == 0) {
         // Last task was just disenrolled so loop around and wait until
         // another task gets enrolled
         continue;
     }
     remaining -= time_slept;
     if (remaining <= 0)
       break;
   }
   return time_slept;
 }
 void WatcherThread::run() {
   assert(this == watcher_thread(), "just checking");
   this->record_stack_base_and_size();
   this->initialize_thread_local_storage();
   this->set_native_thread_name(this->name());
   this->set_active_handles(JNIHandleBlock::allocate_block());
   while(!_should_terminate) {
     assert(watcher_thread() == Thread::current(),  "thread consistency check");
     assert(watcher_thread() == this,  "thread consistency check");
     // Calculate how long it'll be until the next PeriodicTask work
     // should be done, and sleep that amount of time.
     int time_waited = sleep();
     if (is_error_reported()) {
       // A fatal error has happened, the error handler(VMError::report_and_die)
       // should abort JVM after creating an error log file. However in some
       // rare cases, the error handler itself might deadlock. Here we try to
       // kill JVM if the fatal error handler fails to abort in 2 minutes.
       //
       // This code is in WatcherThread because WatcherThread wakes up
       // periodically so the fatal error handler doesn't need to do anything;
       // also because the WatcherThread is less likely to crash than other
       // threads.
       for (;;) {
         if (!ShowMessageBoxOnError
          && (OnError == NULL || OnError[0] == '\0')
          && Arguments::abort_hook() == NULL) {
              os::sleep(this, 2 * 60 * 1000, false);
              fdStream err(defaultStream::output_fd());
              err.print_raw_cr("# [ timer expired, abort... ]");
              // skip atexit/vm_exit/vm_abort hooks
              os::die();
         }
         // Wake up 5 seconds later, the fatal handler may reset OnError or
         // ShowMessageBoxOnError when it is ready to abort.
         os::sleep(this, 5 * 1000, false);
       }
     }
     PeriodicTask::real_time_tick(time_waited);
   }
   // Signal that it is terminated
   {
     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
     _watcher_thread = NULL;
     Terminator_lock->notify();
   }
   // Thread destructor usually does this..
   ThreadLocalStorage::set_thread(NULL);
 }
 void WatcherThread::start() {
   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
   if (watcher_thread() == NULL && _startable) {
     _should_terminate = false;
     // Create the single instance of WatcherThread
     new WatcherThread();
   }
 }
 void WatcherThread::make_startable() {
   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
   _startable = true;
 }
 void WatcherThread::stop() {
   {
     MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
     _should_terminate = true;
     OrderAccess::fence();  // ensure WatcherThread sees update in main loop
     WatcherThread* watcher = watcher_thread();
     if (watcher != NULL)
       watcher->unpark();
   }
   // it is ok to take late safepoints here, if needed
   MutexLocker mu(Terminator_lock);
   while(watcher_thread() != NULL) {
     // This wait should make safepoint checks, wait without a timeout,
     // and wait as a suspend-equivalent condition.
     //
     // Note: If the FlatProfiler is running, then this thread is waiting
     // for the WatcherThread to terminate and the WatcherThread, via the
     // FlatProfiler task, is waiting for the external suspend request on
     // this thread to complete. wait_for_ext_suspend_completion() will
     // eventually timeout, but that takes time. Making this wait a
     // suspend-equivalent condition solves that timeout problem.
     //
     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
                           Mutex::_as_suspend_equivalent_flag);
   }
 }
 void WatcherThread::unpark() {
   MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ? NULL : PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
   PeriodicTask_lock->notify();
 }
 void WatcherThread::print_on(outputStream* st) const {
   st->print("\"%s\" ", name());
   Thread::print_on(st);
   st->cr();
 }
 // ======= JavaThread ========
 // A JavaThread is a normal Java thread
 void JavaThread::initialize() {
   // Initialize fields
   // Set the claimed par_id to UINT_MAX (ie not claiming any par_ids)
   set_claimed_par_id(UINT_MAX);
   set_saved_exception_pc(NULL);
   set_threadObj(NULL);
   _anchor.clear();
   set_entry_point(NULL);
   set_jni_functions(jni_functions());
   set_callee_target(NULL);
   set_vm_result(NULL);
   set_vm_result_2(NULL);
   set_vframe_array_head(NULL);
   set_vframe_array_last(NULL);
   set_deferred_locals(NULL);
   set_deopt_mark(NULL);
   set_deopt_nmethod(NULL);
   clear_must_deopt_id();
   set_monitor_chunks(NULL);
   set_next(NULL);
   set_thread_state(_thread_new);
   _terminated = _not_terminated;
   _privileged_stack_top = NULL;
   _array_for_gc = NULL;
   _suspend_equivalent = false;
   _in_deopt_handler = 0;
   _doing_unsafe_access = false;
   _stack_guard_state = stack_guard_unused;
   (void)const_cast<oop&>(_exception_oop = oop(NULL));
   _exception_pc  = 0;
   _exception_handler_pc = 0;
   _is_method_handle_return = 0;
   _jvmti_thread_state= NULL;
   _should_post_on_exceptions_flag = JNI_FALSE;
   _jvmti_get_loaded_classes_closure = NULL;
   _interp_only_mode    = 0;
   _special_runtime_exit_condition = _no_async_condition;
   _pending_async_exception = NULL;
   _thread_stat = NULL;
   _thread_stat = new ThreadStatistics();
   _blocked_on_compilation = false;
   _jni_active_critical = 0;
   _pending_jni_exception_check_fn = NULL;
   _do_not_unlock_if_synchronized = false;
   _cached_monitor_info = NULL;
   _parker = Parker::Allocate(this) ;
 #ifndef PRODUCT
   _jmp_ring_index = 0;
   for (int ji = 0 ; ji < jump_ring_buffer_size ; ji++ ) {
     record_jump(NULL, NULL, NULL, 0);
   }
 #endif /* PRODUCT */
   set_thread_profiler(NULL);
   if (FlatProfiler::is_active()) {
     // This is where we would decide to either give each thread it's own profiler
     // or use one global one from FlatProfiler,
     // or up to some count of the number of profiled threads, etc.
     ThreadProfiler* pp = new ThreadProfiler();
     pp->engage();
     set_thread_profiler(pp);
   }
   // Setup safepoint state info for this thread
   ThreadSafepointState::create(this);
   debug_only(_java_call_counter = 0);
   // JVMTI PopFrame support
   _popframe_condition = popframe_inactive;
   _popframe_preserved_args = NULL;
   _popframe_preserved_args_size = 0;
   _frames_to_pop_failed_realloc = 0;
   pd_initialize();
 }
 #if INCLUDE_ALL_GCS
 SATBMarkQueueSet JavaThread::_satb_mark_queue_set;
 DirtyCardQueueSet JavaThread::_dirty_card_queue_set;
 #endif // INCLUDE_ALL_GCS
 JavaThread::JavaThread(bool is_attaching_via_jni) :
   Thread()
 #if INCLUDE_ALL_GCS
   , _satb_mark_queue(&_satb_mark_queue_set),
   _dirty_card_queue(&_dirty_card_queue_set)
 #endif // INCLUDE_ALL_GCS
 {
   initialize();
   if (is_attaching_via_jni) {
     _jni_attach_state = _attaching_via_jni;
   } else {
     _jni_attach_state = _not_attaching_via_jni;
   }
   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
 }
 bool JavaThread::reguard_stack(address cur_sp) {
   if (_stack_guard_state != stack_guard_yellow_disabled) {
     return true; // Stack already guarded or guard pages not needed.
   }
   if (register_stack_overflow()) {
     // For those architectures which have separate register and
     // memory stacks, we must check the register stack to see if
     // it has overflowed.
     return false;
   }
   // Java code never executes within the yellow zone: the latter is only
   // there to provoke an exception during stack banging.  If java code
   // is executing there, either StackShadowPages should be larger, or
   // some exception code in c1, c2 or the interpreter isn't unwinding
   // when it should.
   guarantee(cur_sp > stack_yellow_zone_base(), "not enough space to reguard - increase StackShadowPages");
   enable_stack_yellow_zone();
   return true;
 }
 bool JavaThread::reguard_stack(void) {
   return reguard_stack(os::current_stack_pointer());
 }
 void JavaThread::block_if_vm_exited() {
   if (_terminated == _vm_exited) {
     // _vm_exited is set at safepoint, and Threads_lock is never released
     // we will block here forever
     Threads_lock->lock_without_safepoint_check();
     ShouldNotReachHere();
   }
 }
 // Remove this ifdef when C1 is ported to the compiler interface.
 static void compiler_thread_entry(JavaThread* thread, TRAPS);
 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
   Thread()
 #if INCLUDE_ALL_GCS
   , _satb_mark_queue(&_satb_mark_queue_set),
   _dirty_card_queue(&_dirty_card_queue_set)
 #endif // INCLUDE_ALL_GCS
 {
   if (TraceThreadEvents) {
     tty->print_cr("creating thread %p", this);
   }
   initialize();
   _jni_attach_state = _not_attaching_via_jni;
   set_entry_point(entry_point);
   // Create the native thread itself.
   // %note runtime_23
   os::ThreadType thr_type = os::java_thread;
   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
                                                      os::java_thread;
   os::create_thread(this, thr_type, stack_sz);
   // The _osthread may be NULL here because we ran out of memory (too many threads active).
   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
   // the exception consists of creating the exception object & initializing it, initialization
   // will leave the VM via a JavaCall and then all locks must be unlocked).
   //
   // The thread is still suspended when we reach here. Thread must be explicit started
   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
   // by calling Threads:add. The reason why this is not done here, is because the thread
   // object must be fully initialized (take a look at JVM_Start)
 }
 JavaThread::~JavaThread() {
   if (TraceThreadEvents) {
       tty->print_cr("terminate thread %p", this);
   }
   // JSR166 -- return the parker to the free list
   Parker::Release(_parker);
   _parker = NULL ;
   // Free any remaining  previous UnrollBlock
   vframeArray* old_array = vframe_array_last();
   if (old_array != NULL) {
     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
     old_array->set_unroll_block(NULL);
     delete old_info;
     delete old_array;
   }
   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
   if (deferred != NULL) {
     // This can only happen if thread is destroyed before deoptimization occurs.
     assert(deferred->length() != 0, "empty array!");
     do {
       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
       deferred->remove_at(0);
       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
       delete dlv;
     } while (deferred->length() != 0);
     delete deferred;
   }
   // All Java related clean up happens in exit
   ThreadSafepointState::destroy(this);
   if (_thread_profiler != NULL) delete _thread_profiler;
   if (_thread_stat != NULL) delete _thread_stat;
 }
 // The first routine called by a new Java thread
 void JavaThread::run() {
   // initialize thread-local alloc buffer related fields
   this->initialize_tlab();
   // used to test validitity of stack trace backs
   this->record_base_of_stack_pointer();
   // Record real stack base and size.
   this->record_stack_base_and_size();
   // Initialize thread local storage; set before calling MutexLocker
   this->initialize_thread_local_storage();
   this->create_stack_guard_pages();
   this->cache_global_variables();
   // Thread is now sufficient initialized to be handled by the safepoint code as being
   // in the VM. Change thread state from _thread_new to _thread_in_vm
   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
   assert(JavaThread::current() == this, "sanity check");
   assert(!Thread::current()->owns_locks(), "sanity check");
   DTRACE_THREAD_PROBE(start, this);
   // This operation might block. We call that after all safepoint checks for a new thread has
   // been completed.
   this->set_active_handles(JNIHandleBlock::allocate_block());
   if (JvmtiExport::should_post_thread_life()) {
     JvmtiExport::post_thread_start(this);
   }
   JFR_ONLY(Jfr::on_thread_start(this);)
   // We call another function to do the rest so we are sure that the stack addresses used
   // from there will be lower than the stack base just computed
   thread_main_inner();
   // Note, thread is no longer valid at this point!
 }
 void JavaThread::thread_main_inner() {
   assert(JavaThread::current() == this, "sanity check");
   assert(this->threadObj() != NULL, "just checking");
   // Execute thread entry point unless this thread has a pending exception
   // or has been stopped before starting.
   // Note: Due to JVM_StopThread we can have pending exceptions already!
   if (!this->has_pending_exception() &&
       !java_lang_Thread::is_stillborn(this->threadObj())) {
     {
       ResourceMark rm(this);
       this->set_native_thread_name(this->get_thread_name());
     }
     HandleMark hm(this);
     this->entry_point()(this, this);
   }
   DTRACE_THREAD_PROBE(stop, this);
   this->exit(false);
   delete this;
 }
 static void ensure_join(JavaThread* thread) {
   // We do not need to grap the Threads_lock, since we are operating on ourself.
   Handle threadObj(thread, thread->threadObj());
   assert(threadObj.not_null(), "java thread object must exist");
   ObjectLocker lock(threadObj, thread);
   // Ignore pending exception (ThreadDeath), since we are exiting anyway
   thread->clear_pending_exception();
   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
   // Clear the native thread instance - this makes isAlive return false and allows the join()
   // to complete once we've done the notify_all below
   java_lang_Thread::set_thread(threadObj(), NULL);
   lock.notify_all(thread);
   // Ignore pending exception (ThreadDeath), since we are exiting anyway
   thread->clear_pending_exception();
 }
 // For any new cleanup additions, please check to see if they need to be applied to
 // cleanup_failed_attach_current_thread as well.
 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
   assert(this == JavaThread::current(),  "thread consistency check");
   HandleMark hm(this);
   Handle uncaught_exception(this, this->pending_exception());
   this->clear_pending_exception();
   Handle threadObj(this, this->threadObj());
   assert(threadObj.not_null(), "Java thread object should be created");
   if (get_thread_profiler() != NULL) {
     get_thread_profiler()->disengage();
     ResourceMark rm;
     get_thread_profiler()->print(get_thread_name());
   }
   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
   {
     EXCEPTION_MARK;
     CLEAR_PENDING_EXCEPTION;
   }
   // FIXIT: The is_null check is only so it works better on JDK1.2 VM's. This
   // has to be fixed by a runtime query method
   if (!destroy_vm || JDK_Version::is_jdk12x_version()) {
     // JSR-166: change call from from ThreadGroup.uncaughtException to
     // java.lang.Thread.dispatchUncaughtException
     if (uncaught_exception.not_null()) {
       Handle group(this, java_lang_Thread::threadGroup(threadObj()));
       {
         EXCEPTION_MARK;
         // Check if the method Thread.dispatchUncaughtException() exists. If so
         // call it.  Otherwise we have an older library without the JSR-166 changes,
         // so call ThreadGroup.uncaughtException()
         KlassHandle recvrKlass(THREAD, threadObj->klass());
         CallInfo callinfo;
         KlassHandle thread_klass(THREAD, SystemDictionary::Thread_klass());
         LinkResolver::resolve_virtual_call(callinfo, threadObj, recvrKlass, thread_klass,
                                            vmSymbols::dispatchUncaughtException_name(),
                                            vmSymbols::throwable_void_signature(),
                                            KlassHandle(), false, false, THREAD);
         CLEAR_PENDING_EXCEPTION;
         methodHandle method = callinfo.selected_method();
         if (method.not_null()) {
           JavaValue result(T_VOID);
           JavaCalls::call_virtual(&result,
                                   threadObj, thread_klass,
                                   vmSymbols::dispatchUncaughtException_name(),
                                   vmSymbols::throwable_void_signature(),
                                   uncaught_exception,
                                   THREAD);
         } else {
           KlassHandle thread_group(THREAD, SystemDictionary::ThreadGroup_klass());
           JavaValue result(T_VOID);
           JavaCalls::call_virtual(&result,
                                   group, thread_group,
                                   vmSymbols::uncaughtException_name(),
                                   vmSymbols::thread_throwable_void_signature(),
                                   threadObj,           // Arg 1
                                   uncaught_exception,  // Arg 2
                                   THREAD);
         }
         if (HAS_PENDING_EXCEPTION) {
           ResourceMark rm(this);
           jio_fprintf(defaultStream::error_stream(),
                 "\nException: %s thrown from the UncaughtExceptionHandler"
                 " in thread \"%s\"\n",
                 pending_exception()->klass()->external_name(),
                 get_thread_name());
           CLEAR_PENDING_EXCEPTION;
         }
       }
     }
     JFR_ONLY(Jfr::on_java_thread_dismantle(this);)
     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
     // is deprecated anyhow.
     if (!is_Compiler_thread()) {
       int count = 3;
       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
         EXCEPTION_MARK;
         JavaValue result(T_VOID);
         KlassHandle thread_klass(THREAD, SystemDictionary::Thread_klass());
         JavaCalls::call_virtual(&result,
                               threadObj, thread_klass,
                               vmSymbols::exit_method_name(),
                               vmSymbols::void_method_signature(),
                               THREAD);
         CLEAR_PENDING_EXCEPTION;
       }
     }
     // notify JVMTI
     if (JvmtiExport::should_post_thread_life()) {
       JvmtiExport::post_thread_end(this);
     }
     // We have notified the agents that we are exiting, before we go on,
     // we must check for a pending external suspend request and honor it
     // in order to not surprise the thread that made the suspend request.
     while (true) {
       {
         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
         if (!is_external_suspend()) {
           set_terminated(_thread_exiting);
           ThreadService::current_thread_exiting(this);
           break;
         }
         // Implied else:
         // Things get a little tricky here. We have a pending external
         // suspend request, but we are holding the SR_lock so we
         // can't just self-suspend. So we temporarily drop the lock
         // and then self-suspend.
       }
       ThreadBlockInVM tbivm(this);
       java_suspend_self();
       // We're done with this suspend request, but we have to loop around
       // and check again. Eventually we will get SR_lock without a pending
       // external suspend request and will be able to mark ourselves as
       // exiting.
     }
     // no more external suspends are allowed at this point
   } else {
     // before_exit() has already posted JVMTI THREAD_END events
   }
   // Notify waiters on thread object. This has to be done after exit() is called
   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
   // group should have the destroyed bit set before waiters are notified).
   ensure_join(this);
   assert(!this->has_pending_exception(), "ensure_join should have cleared");
   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
   // held by this thread must be released.  A detach operation must only
   // get here if there are no Java frames on the stack.  Therefore, any
   // owned monitors at this point MUST be JNI-acquired monitors which are
   // pre-inflated and in the monitor cache.
   //
   // ensure_join() ignores IllegalThreadStateExceptions, and so does this.
   if (exit_type == jni_detach && JNIDetachReleasesMonitors) {
     assert(!this->has_last_Java_frame(), "detaching with Java frames?");
     ObjectSynchronizer::release_monitors_owned_by_thread(this);
     assert(!this->has_pending_exception(), "release_monitors should have cleared");
   }
   // These things needs to be done while we are still a Java Thread. Make sure that thread
   // is in a consistent state, in case GC happens
   assert(_privileged_stack_top == NULL, "must be NULL when we get here");
   JFR_ONLY(Jfr::on_thread_exit(this);)
   if (active_handles() != NULL) {
     JNIHandleBlock* block = active_handles();
     set_active_handles(NULL);
     JNIHandleBlock::release_block(block);
   }
   if (free_handle_block() != NULL) {
     JNIHandleBlock* block = free_handle_block();
     set_free_handle_block(NULL);
     JNIHandleBlock::release_block(block);
   }
   // These have to be removed while this is still a valid thread.
   remove_stack_guard_pages();
   if (UseTLAB) {
     tlab().make_parsable(true);  // retire TLAB
   }
   if (JvmtiEnv::environments_might_exist()) {
     JvmtiExport::cleanup_thread(this);
   }
   // We must flush any deferred card marks before removing a thread from
   // the list of active threads.
   Universe::heap()->flush_deferred_store_barrier(this);
   assert(deferred_card_mark().is_empty(), "Should have been flushed");
 #if INCLUDE_ALL_GCS
   // We must flush the G1-related buffers before removing a thread
   // from the list of active threads. We must do this after any deferred
   // card marks have been flushed (above) so that any entries that are
   // added to the thread's dirty card queue as a result are not lost.
   if (UseG1GC) {
     flush_barrier_queues();
   }
 #endif // INCLUDE_ALL_GCS
   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
   Threads::remove(this);
 }
 #if INCLUDE_ALL_GCS
 // Flush G1-related queues.
 void JavaThread::flush_barrier_queues() {
   satb_mark_queue().flush();
   dirty_card_queue().flush();
 }
 void JavaThread::initialize_queues() {
   assert(!SafepointSynchronize::is_at_safepoint(),
          "we should not be at a safepoint");
   ObjPtrQueue& satb_queue = satb_mark_queue();
   SATBMarkQueueSet& satb_queue_set = satb_mark_queue_set();
   // The SATB queue should have been constructed with its active
   // field set to false.
   assert(!satb_queue.is_active(), "SATB queue should not be active");
   assert(satb_queue.is_empty(), "SATB queue should be empty");
   // If we are creating the thread during a marking cycle, we should
   // set the active field of the SATB queue to true.
   if (satb_queue_set.is_active()) {
     satb_queue.set_active(true);
   }
   DirtyCardQueue& dirty_queue = dirty_card_queue();
   // The dirty card queue should have been constructed with its
   // active field set to true.
   assert(dirty_queue.is_active(), "dirty card queue should be active");
 }
 #endif // INCLUDE_ALL_GCS
 void JavaThread::cleanup_failed_attach_current_thread() {
   if (get_thread_profiler() != NULL) {
     get_thread_profiler()->disengage();
     ResourceMark rm;
     get_thread_profiler()->print(get_thread_name());
   }
   if (active_handles() != NULL) {
     JNIHandleBlock* block = active_handles();
     set_active_handles(NULL);
     JNIHandleBlock::release_block(block);
   }
   if (free_handle_block() != NULL) {
     JNIHandleBlock* block = free_handle_block();
     set_free_handle_block(NULL);
     JNIHandleBlock::release_block(block);
   }
   // These have to be removed while this is still a valid thread.
   remove_stack_guard_pages();
   if (UseTLAB) {
     tlab().make_parsable(true);  // retire TLAB, if any
   }
 #if INCLUDE_ALL_GCS
   if (UseG1GC) {
     flush_barrier_queues();
   }
 #endif // INCLUDE_ALL_GCS
   Threads::remove(this);
   delete this;
 }
 JavaThread* JavaThread::active() {
   Thread* thread = ThreadLocalStorage::thread();
   assert(thread != NULL, "just checking");
   if (thread->is_Java_thread()) {
     return (JavaThread*) thread;
   } else {
     assert(thread->is_VM_thread(), "this must be a vm thread");
     VM_Operation* op = ((VMThread*) thread)->vm_operation();
     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
     assert(ret->is_Java_thread(), "must be a Java thread");
     return ret;
   }
 }
 bool JavaThread::is_lock_owned(address adr) const {
   if (Thread::is_lock_owned(adr)) return true;
   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
     if (chunk->contains(adr)) return true;
   }
   return false;
 }
 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
   chunk->set_next(monitor_chunks());
   set_monitor_chunks(chunk);
 }
 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
   guarantee(monitor_chunks() != NULL, "must be non empty");
   if (monitor_chunks() == chunk) {
     set_monitor_chunks(chunk->next());
   } else {
     MonitorChunk* prev = monitor_chunks();
     while (prev->next() != chunk) prev = prev->next();
     prev->set_next(chunk->next());
   }
 }
 // JVM support.
 // Note: this function shouldn't block if it's called in
 // _thread_in_native_trans state (such as from
 // check_special_condition_for_native_trans()).
 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
   if (has_last_Java_frame() && has_async_condition()) {
     // If we are at a polling page safepoint (not a poll return)
     // then we must defer async exception because live registers
     // will be clobbered by the exception path. Poll return is
     // ok because the call we a returning from already collides
     // with exception handling registers and so there is no issue.
     // (The exception handling path kills call result registers but
     //  this is ok since the exception kills the result anyway).
     if (is_at_poll_safepoint()) {
       // if the code we are returning to has deoptimized we must defer
       // the exception otherwise live registers get clobbered on the
       // exception path before deoptimization is able to retrieve them.
       //
       RegisterMap map(this, false);
       frame caller_fr = last_frame().sender(&map);
       assert(caller_fr.is_compiled_frame(), "what?");
       if (caller_fr.is_deoptimized_frame()) {
         if (TraceExceptions) {
           ResourceMark rm;
           tty->print_cr("deferred async exception at compiled safepoint");
         }
         return;
       }
     }
   }
   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
   if (condition == _no_async_condition) {
     // Conditions have changed since has_special_runtime_exit_condition()
     // was called:
     // - if we were here only because of an external suspend request,
     //   then that was taken care of above (or cancelled) so we are done
     // - if we were here because of another async request, then it has
     //   been cleared between the has_special_runtime_exit_condition()
     //   and now so again we are done
     return;
   }
   // Check for pending async. exception
   if (_pending_async_exception != NULL) {
     // Only overwrite an already pending exception, if it is not a threadDeath.
     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
       // We cannot call Exceptions::_throw(...) here because we cannot block
       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
       if (TraceExceptions) {
         ResourceMark rm;
         tty->print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", this);
         if (has_last_Java_frame() ) {
           frame f = last_frame();
           tty->print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", f.pc(), f.sp());
         }
         tty->print_cr(" of type: %s", InstanceKlass::cast(_pending_async_exception->klass())->external_name());
       }
       _pending_async_exception = NULL;
       clear_has_async_exception();
     }
   }
   if (check_unsafe_error &&
       condition == _async_unsafe_access_error && !has_pending_exception()) {
     condition = _no_async_condition;  // done
     switch (thread_state()) {
     case _thread_in_vm:
       {
         JavaThread* THREAD = this;
         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
       }
     case _thread_in_native:
       {
         ThreadInVMfromNative tiv(this);
         JavaThread* THREAD = this;
         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
       }
     case _thread_in_Java:
       {
         ThreadInVMfromJava tiv(this);
         JavaThread* THREAD = this;
         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
       }
     default:
       ShouldNotReachHere();
     }
   }
   assert(condition == _no_async_condition || has_pending_exception() ||
          (!check_unsafe_error && condition == _async_unsafe_access_error),
          "must have handled the async condition, if no exception");
 }
 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
   //
   // Check for pending external suspend. Internal suspend requests do
   // not use handle_special_runtime_exit_condition().
   // If JNIEnv proxies are allowed, don't self-suspend if the target
   // thread is not the current thread. In older versions of jdbx, jdbx
   // threads could call into the VM with another thread's JNIEnv so we
   // can be here operating on behalf of a suspended thread (4432884).
   bool do_self_suspend = is_external_suspend_with_lock();
   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
     //
     // Because thread is external suspended the safepoint code will count
     // thread as at a safepoint. This can be odd because we can be here
     // as _thread_in_Java which would normally transition to _thread_blocked
     // at a safepoint. We would like to mark the thread as _thread_blocked
     // before calling java_suspend_self like all other callers of it but
     // we must then observe proper safepoint protocol. (We can't leave
     // _thread_blocked with a safepoint in progress). However we can be
     // here as _thread_in_native_trans so we can't use a normal transition
     // constructor/destructor pair because they assert on that type of
     // transition. We could do something like:
     //
     // JavaThreadState state = thread_state();
     // set_thread_state(_thread_in_vm);
     // {
     //   ThreadBlockInVM tbivm(this);
     //   java_suspend_self()
     // }
     // set_thread_state(_thread_in_vm_trans);
     // if (safepoint) block;
     // set_thread_state(state);
     //
     // but that is pretty messy. Instead we just go with the way the
     // code has worked before and note that this is the only path to
     // java_suspend_self that doesn't put the thread in _thread_blocked
     // mode.
     frame_anchor()->make_walkable(this);
     java_suspend_self();
     // We might be here for reasons in addition to the self-suspend request
     // so check for other async requests.
   }
   if (check_asyncs) {
     check_and_handle_async_exceptions();
   }
   JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(this);)
 }
 void JavaThread::send_thread_stop(oop java_throwable)  {
   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
   // Do not throw asynchronous exceptions against the compiler thread
   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
   if (is_Compiler_thread()) return;
   {
     // Actually throw the Throwable against the target Thread - however
     // only if there is no thread death exception installed already.
     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
       // If the topmost frame is a runtime stub, then we are calling into
       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
       // must deoptimize the caller before continuing, as the compiled  exception handler table
       // may not be valid
       if (has_last_Java_frame()) {
         frame f = last_frame();
         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
           RegisterMap reg_map(this, UseBiasedLocking);
           frame compiled_frame = f.sender(&reg_map);
           if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
           }
         }
       }
       // Set async. pending exception in thread.
       set_pending_async_exception(java_throwable);
       if (TraceExceptions) {
        ResourceMark rm;
        tty->print_cr("Pending Async. exception installed of type: %s", InstanceKlass::cast(_pending_async_exception->klass())->external_name());
       }
       // for AbortVMOnException flag
       NOT_PRODUCT(Exceptions::debug_check_abort(InstanceKlass::cast(_pending_async_exception->klass())->external_name()));
     }
   }
   // Interrupt thread so it will wake up from a potential wait()
   Thread::interrupt(this);
 }
 // External suspension mechanism.
 //
 // Tell the VM to suspend a thread when ever it knows that it does not hold on
 // to any VM_locks and it is at a transition
 // Self-suspension will happen on the transition out of the vm.
 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
 //
 // Guarantees on return:
 //   + Target thread will not execute any new bytecode (that's why we need to
 //     force a safepoint)
 //   + Target thread will not enter any new monitors
 //
 void JavaThread::java_suspend() {
   { MutexLocker mu(Threads_lock);
     if (!Threads::includes(this) || is_exiting() || this->threadObj() == NULL) {
        return;
     }
   }
   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
     if (!is_external_suspend()) {
       // a racing resume has cancelled us; bail out now
       return;
     }
     // suspend is done
     uint32_t debug_bits = 0;
     // Warning: is_ext_suspend_completed() may temporarily drop the
     // SR_lock to allow the thread to reach a stable thread state if
     // it is currently in a transient thread state.
     if (is_ext_suspend_completed(false /* !called_by_wait */,
                                  SuspendRetryDelay, &debug_bits) ) {
       return;
     }
   }
   VM_ForceSafepoint vm_suspend;
   VMThread::execute(&vm_suspend);
 }
 // Part II of external suspension.
 // A JavaThread self suspends when it detects a pending external suspend
 // request. This is usually on transitions. It is also done in places
 // where continuing to the next transition would surprise the caller,
 // e.g., monitor entry.
 //
 // Returns the number of times that the thread self-suspended.
 //
 // Note: DO NOT call java_suspend_self() when you just want to block current
 //       thread. java_suspend_self() is the second stage of cooperative
 //       suspension for external suspend requests and should only be used
 //       to complete an external suspend request.
 //
 int JavaThread::java_suspend_self() {
   int ret = 0;
   // we are in the process of exiting so don't suspend
   if (is_exiting()) {
      clear_external_suspend();
      return ret;
   }
   assert(_anchor.walkable() ||
     (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
     "must have walkable stack");
   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
   assert(!this->is_ext_suspended(),
     "a thread trying to self-suspend should not already be suspended");
   if (this->is_suspend_equivalent()) {
     // If we are self-suspending as a result of the lifting of a
     // suspend equivalent condition, then the suspend_equivalent
     // flag is not cleared until we set the ext_suspended flag so
     // that wait_for_ext_suspend_completion() returns consistent
     // results.
     this->clear_suspend_equivalent();
   }
   // A racing resume may have cancelled us before we grabbed SR_lock
   // above. Or another external suspend request could be waiting for us
   // by the time we return from SR_lock()->wait(). The thread
   // that requested the suspension may already be trying to walk our
   // stack and if we return now, we can change the stack out from under
   // it. This would be a "bad thing (TM)" and cause the stack walker
   // to crash. We stay self-suspended until there are no more pending
   // external suspend requests.
   while (is_external_suspend()) {
     ret++;
     this->set_ext_suspended();
     // _ext_suspended flag is cleared by java_resume()
     while (is_ext_suspended()) {
       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
     }
   }
   return ret;
 }
 #ifdef ASSERT
 // verify the JavaThread has not yet been published in the Threads::list, and
 // hence doesn't need protection from concurrent access at this stage
 void JavaThread::verify_not_published() {
   if (!Threads_lock->owned_by_self()) {
    MutexLockerEx ml(Threads_lock,  Mutex::_no_safepoint_check_flag);
    assert( !Threads::includes(this),
            "java thread shouldn't have been published yet!");
   }
   else {
    assert( !Threads::includes(this),
            "java thread shouldn't have been published yet!");
   }
 }
 #endif
 // Slow path when the native==>VM/Java barriers detect a safepoint is in
 // progress or when _suspend_flags is non-zero.
 // Current thread needs to self-suspend if there is a suspend request and/or
 // block if a safepoint is in progress.
 // Async exception ISN'T checked.
 // Note only the ThreadInVMfromNative transition can call this function
 // directly and when thread state is _thread_in_native_trans
 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
   JavaThread *curJT = JavaThread::current();
   bool do_self_suspend = thread->is_external_suspend();
   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
   // If JNIEnv proxies are allowed, don't self-suspend if the target
   // thread is not the current thread. In older versions of jdbx, jdbx
   // threads could call into the VM with another thread's JNIEnv so we
   // can be here operating on behalf of a suspended thread (4432884).
   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
     JavaThreadState state = thread->thread_state();
     // We mark this thread_blocked state as a suspend-equivalent so
     // that a caller to is_ext_suspend_completed() won't be confused.
     // The suspend-equivalent state is cleared by java_suspend_self().
     thread->set_suspend_equivalent();
     // If the safepoint code sees the _thread_in_native_trans state, it will
     // wait until the thread changes to other thread state. There is no
     // guarantee on how soon we can obtain the SR_lock and complete the
     // self-suspend request. It would be a bad idea to let safepoint wait for
     // too long. Temporarily change the state to _thread_blocked to
     // let the VM thread know that this thread is ready for GC. The problem
     // of changing thread state is that safepoint could happen just after
     // java_suspend_self() returns after being resumed, and VM thread will
     // see the _thread_blocked state. We must check for safepoint
     // after restoring the state and make sure we won't leave while a safepoint
     // is in progress.
     thread->set_thread_state(_thread_blocked);
     thread->java_suspend_self();
     thread->set_thread_state(state);
     // Make sure new state is seen by VM thread
     if (os::is_MP()) {
       if (UseMembar) {
         // Force a fence between the write above and read below
         OrderAccess::fence();
       } else {
         // Must use this rather than serialization page in particular on Windows
         InterfaceSupport::serialize_memory(thread);
       }
     }
   }
   if (SafepointSynchronize::do_call_back()) {
     // If we are safepointing, then block the caller which may not be
     // the same as the target thread (see above).
     SafepointSynchronize::block(curJT);
   }
   if (thread->is_deopt_suspend()) {
     thread->clear_deopt_suspend();
     RegisterMap map(thread, false);
     frame f = thread->last_frame();
     while ( f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
       f = f.sender(&map);
     }
     if (f.id() == thread->must_deopt_id()) {
       thread->clear_must_deopt_id();
       f.deoptimize(thread);
     } else {
       fatal("missed deoptimization!");
     }
   }
   JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(thread);)
 }
 // Slow path when the native==>VM/Java barriers detect a safepoint is in
 // progress or when _suspend_flags is non-zero.
 // Current thread needs to self-suspend if there is a suspend request and/or
 // block if a safepoint is in progress.
 // Also check for pending async exception (not including unsafe access error).
 // Note only the native==>VM/Java barriers can call this function and when
 // thread state is _thread_in_native_trans.
 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
   check_safepoint_and_suspend_for_native_trans(thread);
   if (thread->has_async_exception()) {
     // We are in _thread_in_native_trans state, don't handle unsafe
     // access error since that may block.
     thread->check_and_handle_async_exceptions(false);
   }
 }
 // This is a variant of the normal
 // check_special_condition_for_native_trans with slightly different
 // semantics for use by critical native wrappers.  It does all the
 // normal checks but also performs the transition back into
 // thread_in_Java state.  This is required so that critical natives
 // can potentially block and perform a GC if they are the last thread
 // exiting the GC_locker.
 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
   check_special_condition_for_native_trans(thread);
   // Finish the transition
   thread->set_thread_state(_thread_in_Java);
   if (thread->do_critical_native_unlock()) {
     ThreadInVMfromJavaNoAsyncException tiv(thread);
     GC_locker::unlock_critical(thread);
     thread->clear_critical_native_unlock();
   }
 }
 // We need to guarantee the Threads_lock here, since resumes are not
 // allowed during safepoint synchronization
 // Can only resume from an external suspension
 void JavaThread::java_resume() {
   assert_locked_or_safepoint(Threads_lock);
   // Sanity check: thread is gone, has started exiting or the thread
   // was not externally suspended.
   if (!Threads::includes(this) || is_exiting() || !is_external_suspend()) {
     return;
   }
   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
   clear_external_suspend();
   if (is_ext_suspended()) {
     clear_ext_suspended();
     SR_lock()->notify_all();
   }
 }
 void JavaThread::create_stack_guard_pages() {
   if (!os::uses_stack_guard_pages() ||
       _stack_guard_state != stack_guard_unused ||
       (DisablePrimordialThreadGuardPages && os::is_primordial_thread())) {
       if (TraceThreadEvents) {
         tty->print_cr("Stack guard page creation for thread "
                       UINTX_FORMAT " disabled", os::current_thread_id());
       }
     return;
   }
   address low_addr = stack_base() - stack_size();
   size_t len = (StackYellowPages + StackRedPages) * os::vm_page_size();
   int allocate = os::allocate_stack_guard_pages();
   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
   if (allocate && !os::create_stack_guard_pages((char *) low_addr, len)) {
     warning("Attempt to allocate stack guard pages failed.");
     return;
   }
   if (os::guard_memory((char *) low_addr, len)) {
     _stack_guard_state = stack_guard_enabled;
   } else {
     warning("Attempt to protect stack guard pages failed.");
     if (os::uncommit_memory((char *) low_addr, len)) {
       warning("Attempt to deallocate stack guard pages failed.");
     }
   }
 }
 void JavaThread::remove_stack_guard_pages() {
   assert(Thread::current() == this, "from different thread");
   if (_stack_guard_state == stack_guard_unused) return;
   address low_addr = stack_base() - stack_size();
   size_t len = (StackYellowPages + StackRedPages) * os::vm_page_size();
   if (os::allocate_stack_guard_pages()) {
     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
       _stack_guard_state = stack_guard_unused;
     } else {
       warning("Attempt to deallocate stack guard pages failed.");
     }
   } else {
     if (_stack_guard_state == stack_guard_unused) return;
     if (os::unguard_memory((char *) low_addr, len)) {
       _stack_guard_state = stack_guard_unused;
     } else {
         warning("Attempt to unprotect stack guard pages failed.");
     }
   }
 }
 void JavaThread::enable_stack_yellow_zone() {
   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
   // The base notation is from the stacks point of view, growing downward.
   // We need to adjust it to work correctly with guard_memory()
   address base = stack_yellow_zone_base() - stack_yellow_zone_size();
   guarantee(base < stack_base(),"Error calculating stack yellow zone");
   guarantee(base < os::current_stack_pointer(),"Error calculating stack yellow zone");
   if (os::guard_memory((char *) base, stack_yellow_zone_size())) {
     _stack_guard_state = stack_guard_enabled;
   } else {
     warning("Attempt to guard stack yellow zone failed.");
   }
   enable_register_stack_guard();
 }
 void JavaThread::disable_stack_yellow_zone() {
   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
   assert(_stack_guard_state != stack_guard_yellow_disabled, "already disabled");
   // Simply return if called for a thread that does not use guard pages.
   if (_stack_guard_state == stack_guard_unused) return;
   // The base notation is from the stacks point of view, growing downward.
   // We need to adjust it to work correctly with guard_memory()
   address base = stack_yellow_zone_base() - stack_yellow_zone_size();
   if (os::unguard_memory((char *)base, stack_yellow_zone_size())) {
     _stack_guard_state = stack_guard_yellow_disabled;
   } else {
     warning("Attempt to unguard stack yellow zone failed.");
   }
   disable_register_stack_guard();
 }
 void JavaThread::enable_stack_red_zone() {
   // The base notation is from the stacks point of view, growing downward.
   // We need to adjust it to work correctly with guard_memory()
   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
   address base = stack_red_zone_base() - stack_red_zone_size();
   guarantee(base < stack_base(),"Error calculating stack red zone");
   guarantee(base < os::current_stack_pointer(),"Error calculating stack red zone");
   if(!os::guard_memory((char *) base, stack_red_zone_size())) {
     warning("Attempt to guard stack red zone failed.");
   }
 }
 void JavaThread::disable_stack_red_zone() {
   // The base notation is from the stacks point of view, growing downward.
   // We need to adjust it to work correctly with guard_memory()
   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
   address base = stack_red_zone_base() - stack_red_zone_size();
   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
     warning("Attempt to unguard stack red zone failed.");
   }
 }
 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
   // ignore is there is no stack
   if (!has_last_Java_frame()) return;
   // traverse the stack frames. Starts from top frame.
   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
     frame* fr = fst.current();
     f(fr, fst.register_map());
   }
 }
 #ifndef PRODUCT
 // Deoptimization
 // Function for testing deoptimization
 void JavaThread::deoptimize() {
   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
   StackFrameStream fst(this, UseBiasedLocking);
   bool deopt = false;           // Dump stack only if a deopt actually happens.
   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
   // Iterate over all frames in the thread and deoptimize
   for(; !fst.is_done(); fst.next()) {
     if(fst.current()->can_be_deoptimized()) {
       if (only_at) {
         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
         // consists of comma or carriage return separated numbers so
         // search for the current bci in that string.
         address pc = fst.current()->pc();
         nmethod* nm =  (nmethod*) fst.current()->cb();
         ScopeDesc* sd = nm->scope_desc_at( pc);
         char buffer[8];
         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
         size_t len = strlen(buffer);
         const char * found = strstr(DeoptimizeOnlyAt, buffer);
         while (found != NULL) {
           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
             // Check that the bci found is bracketed by terminators.
             break;
           }
           found = strstr(found + 1, buffer);
         }
         if (!found) {
           continue;
         }
       }
       if (DebugDeoptimization && !deopt) {
         deopt = true; // One-time only print before deopt
         tty->print_cr("[BEFORE Deoptimization]");
         trace_frames();
         trace_stack();
       }
       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
     }
   }
   if (DebugDeoptimization && deopt) {
     tty->print_cr("[AFTER Deoptimization]");
     trace_frames();
   }
 }
 // Make zombies
 void JavaThread::make_zombies() {
   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
     if (fst.current()->can_be_deoptimized()) {
       // it is a Java nmethod
       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
       nm->make_not_entrant();
     }
   }
 }
 #endif // PRODUCT
 void JavaThread::deoptimized_wrt_marked_nmethods() {
   if (!has_last_Java_frame()) return;
   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
   StackFrameStream fst(this, UseBiasedLocking);
   for(; !fst.is_done(); fst.next()) {
     if (fst.current()->should_be_deoptimized()) {
       if (LogCompilation && xtty != NULL) {
         nmethod* nm = fst.current()->cb()->as_nmethod_or_null();
         xtty->elem("deoptimized thread='" UINTX_FORMAT "' compile_id='%d'",
                    this->name(), nm != NULL ? nm->compile_id() : -1);
       }
       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
     }
   }
 }
 // GC support
 static void frame_gc_epilogue(frame* f, const RegisterMap* map) { f->gc_epilogue(); }
 void JavaThread::gc_epilogue() {
   frames_do(frame_gc_epilogue);
 }
 static void frame_gc_prologue(frame* f, const RegisterMap* map) { f->gc_prologue(); }
 void JavaThread::gc_prologue() {
   frames_do(frame_gc_prologue);
 }
 // If the caller is a NamedThread, then remember, in the current scope,
 // the given JavaThread in its _processed_thread field.
 class RememberProcessedThread: public StackObj {
   NamedThread* _cur_thr;
 public:
   RememberProcessedThread(JavaThread* jthr) {
     Thread* thread = Thread::current();
     if (thread->is_Named_thread()) {
       _cur_thr = (NamedThread *)thread;
       _cur_thr->set_processed_thread(jthr);
     } else {
       _cur_thr = NULL;
     }
   }
   ~RememberProcessedThread() {
     if (_cur_thr) {
       _cur_thr->set_processed_thread(NULL);
     }
   }
 };
 void JavaThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
   // Verify that the deferred card marks have been flushed.
   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
   // The ThreadProfiler oops_do is done from FlatProfiler::oops_do
   // since there may be more than one thread using each ThreadProfiler.
   // Traverse the GCHandles
   Thread::oops_do(f, cld_f, cf);
   assert( (!has_last_Java_frame() && java_call_counter() == 0) ||
           (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
   if (has_last_Java_frame()) {
     // Record JavaThread to GC thread
     RememberProcessedThread rpt(this);
     // Traverse the privileged stack
     if (_privileged_stack_top != NULL) {
       _privileged_stack_top->oops_do(f);
     }
     // traverse the registered growable array
     if (_array_for_gc != NULL) {
       for (int index = 0; index < _array_for_gc->length(); index++) {
         f->do_oop(_array_for_gc->adr_at(index));
       }
     }
     // Traverse the monitor chunks
     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
       chunk->oops_do(f);
     }
     // Traverse the execution stack
     for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
       fst.current()->oops_do(f, cld_f, cf, fst.register_map());
     }
   }
   // callee_target is never live across a gc point so NULL it here should
   // it still contain a methdOop.
   set_callee_target(NULL);
   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
   // If we have deferred set_locals there might be oops waiting to be
   // written
   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
   if (list != NULL) {
     for (int i = 0; i < list->length(); i++) {
       list->at(i)->oops_do(f);
     }
   }
   // Traverse instance variables at the end since the GC may be moving things
   // around using this function
   f->do_oop((oop*) &_threadObj);
   f->do_oop((oop*) &_vm_result);
   f->do_oop((oop*) &_exception_oop);
   f->do_oop((oop*) &_pending_async_exception);
   if (jvmti_thread_state() != NULL) {
     jvmti_thread_state()->oops_do(f);
   }
 }
 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
   Thread::nmethods_do(cf);  // (super method is a no-op)
   assert( (!has_last_Java_frame() && java_call_counter() == 0) ||
           (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
   if (has_last_Java_frame()) {
     // Traverse the execution stack
     for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
       fst.current()->nmethods_do(cf);
     }
   }
 }
 void JavaThread::metadata_do(void f(Metadata*)) {
   Thread::metadata_do(f);
   if (has_last_Java_frame()) {
     // Traverse the execution stack to call f() on the methods in the stack
     for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
       fst.current()->metadata_do(f);
     }
   } else if (is_Compiler_thread()) {
     // need to walk ciMetadata in current compile tasks to keep alive.
     CompilerThread* ct = (CompilerThread*)this;
     if (ct->env() != NULL) {
       ct->env()->metadata_do(f);
     }
   }
 }
 // Printing
 const char* _get_thread_state_name(JavaThreadState _thread_state) {
   switch (_thread_state) {
   case _thread_uninitialized:     return "_thread_uninitialized";
   case _thread_new:               return "_thread_new";
   case _thread_new_trans:         return "_thread_new_trans";
   case _thread_in_native:         return "_thread_in_native";
   case _thread_in_native_trans:   return "_thread_in_native_trans";
   case _thread_in_vm:             return "_thread_in_vm";
   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
   case _thread_in_Java:           return "_thread_in_Java";
   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
   case _thread_blocked:           return "_thread_blocked";
   case _thread_blocked_trans:     return "_thread_blocked_trans";
   default:                        return "unknown thread state";
   }
 }
 #ifndef PRODUCT
 void JavaThread::print_thread_state_on(outputStream *st) const {
   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
 };
 void JavaThread::print_thread_state() const {
   print_thread_state_on(tty);
 };
 #endif // PRODUCT
 // Called by Threads::print() for VM_PrintThreads operation
 void JavaThread::print_on(outputStream *st) const {
   st->print("\"%s\" ", get_thread_name());
   oop thread_oop = threadObj();
   if (thread_oop != NULL) {
     st->print("#" INT64_FORMAT " ", java_lang_Thread::thread_id(thread_oop));
     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
   }
   Thread::print_on(st);
   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
   if (thread_oop != NULL && JDK_Version::is_gte_jdk15x_version()) {
     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
   }
 #ifndef PRODUCT
   print_thread_state_on(st);
   _safepoint_state->print_on(st);
 #endif // PRODUCT
 }
 // Called by fatal error handler. The difference between this and
 // JavaThread::print() is that we can't grab lock or allocate memory.
 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
   st->print("JavaThread \"%s\"",  get_thread_name_string(buf, buflen));
   oop thread_obj = threadObj();
   if (thread_obj != NULL) {
      if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
   }
   st->print(" [");
   st->print("%s", _get_thread_state_name(_thread_state));
   if (osthread()) {
     st->print(", id=%d", osthread()->thread_id());
   }
   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
             _stack_base - _stack_size, _stack_base);
   st->print("]");
   return;
 }
 // Verification
 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
 void JavaThread::verify() {
   // Verify oops in the thread.
   oops_do(&VerifyOopClosure::verify_oop, NULL, NULL);
   // Verify the stack frames.
   frames_do(frame_verify);
 }
 // CR 6300358 (sub-CR 2137150)
 // Most callers of this method assume that it can't return NULL but a
 // thread may not have a name whilst it is in the process of attaching to
 // the VM - see CR 6412693, and there are places where a JavaThread can be
 // seen prior to having it's threadObj set (eg JNI attaching threads and
 // if vm exit occurs during initialization). These cases can all be accounted
 // for such that this method never returns NULL.
 const char* JavaThread::get_thread_name() const {
 #ifdef ASSERT
   // early safepoints can hit while current thread does not yet have TLS
   if (!SafepointSynchronize::is_at_safepoint()) {
     Thread *cur = Thread::current();
     if (!(cur->is_Java_thread() && cur == this)) {
       // Current JavaThreads are allowed to get their own name without
       // the Threads_lock.
       assert_locked_or_safepoint(Threads_lock);
     }
   }
 #endif // ASSERT
     return get_thread_name_string();
 }
 // Returns a non-NULL representation of this thread's name, or a suitable
 // descriptive string if there is no set name
 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
   const char* name_str;
   oop thread_obj = threadObj();
   if (thread_obj != NULL) {
     oop name = java_lang_Thread::name(thread_obj);
     if (name != NULL) {
       if (buf == NULL) {
         name_str = java_lang_String::as_utf8_string(name);
       }
       else {
         name_str = java_lang_String::as_utf8_string(name, buf, buflen);
       }
     }
     else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
       name_str = "<no-name - thread is attaching>";
     }
     else {
       name_str = Thread::name();
     }
   }
   else {
     name_str = Thread::name();
   }
   assert(name_str != NULL, "unexpected NULL thread name");
   return name_str;
 }
 const char* JavaThread::get_threadgroup_name() const {
   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
   oop thread_obj = threadObj();
   if (thread_obj != NULL) {
     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
     if (thread_group != NULL) {
       typeArrayOop name = java_lang_ThreadGroup::name(thread_group);
       // ThreadGroup.name can be null
       if (name != NULL) {
         const char* str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length());
         return str;
       }
     }
   }
   return NULL;
 }
 const char* JavaThread::get_parent_name() const {
   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
   oop thread_obj = threadObj();
   if (thread_obj != NULL) {
     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
     if (thread_group != NULL) {
       oop parent = java_lang_ThreadGroup::parent(thread_group);
       if (parent != NULL) {
         typeArrayOop name = java_lang_ThreadGroup::name(parent);
         // ThreadGroup.name can be null
         if (name != NULL) {
           const char* str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length());
           return str;
         }
       }
     }
   }
   return NULL;
 }
 ThreadPriority JavaThread::java_priority() const {
   oop thr_oop = threadObj();
   if (thr_oop == NULL) return NormPriority; // Bootstrapping
   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
   return priority;
 }
 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
   // Link Java Thread object <-> C++ Thread
   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
   // and put it into a new Handle.  The Handle "thread_oop" can then
   // be used to pass the C++ thread object to other methods.
   // Set the Java level thread object (jthread) field of the
   // new thread (a JavaThread *) to C++ thread object using the
   // "thread_oop" handle.
   // Set the thread field (a JavaThread *) of the
   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
   Handle thread_oop(Thread::current(),
                     JNIHandles::resolve_non_null(jni_thread));
   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
     "must be initialized");
   set_threadObj(thread_oop());
   java_lang_Thread::set_thread(thread_oop(), this);
   if (prio == NoPriority) {
     prio = java_lang_Thread::priority(thread_oop());
     assert(prio != NoPriority, "A valid priority should be present");
   }
   // Push the Java priority down to the native thread; needs Threads_lock
   Thread::set_priority(this, prio);
   prepare_ext();
   // Add the new thread to the Threads list and set it in motion.
   // We must have threads lock in order to call Threads::add.
   // It is crucial that we do not block before the thread is
   // added to the Threads list for if a GC happens, then the java_thread oop
   // will not be visited by GC.
   Threads::add(this);
 }
 oop JavaThread::current_park_blocker() {
   // Support for JSR-166 locks
   oop thread_oop = threadObj();
   if (thread_oop != NULL &&
       JDK_Version::current().supports_thread_park_blocker()) {
     return java_lang_Thread::park_blocker(thread_oop);
   }
   return NULL;
 }
 void JavaThread::print_stack_on(outputStream* st) {
   if (!has_last_Java_frame()) return;
   ResourceMark rm;
   HandleMark   hm;
   RegisterMap reg_map(this);
   vframe* start_vf = last_java_vframe(&reg_map);
   int count = 0;
   for (vframe* f = start_vf; f; f = f->sender() ) {
     if (f->is_java_frame()) {
       javaVFrame* jvf = javaVFrame::cast(f);
       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
       // Print out lock information
       if (JavaMonitorsInStackTrace) {
         jvf->print_lock_info_on(st, count);
       }
     } else {
       // Ignore non-Java frames
     }
     // Bail-out case for too deep stacks
     count++;
     if (MaxJavaStackTraceDepth == count) return;
   }
 }
 // JVMTI PopFrame support
 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
   if (in_bytes(size_in_bytes) != 0) {
     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
     _popframe_preserved_args_size = in_bytes(size_in_bytes);
     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
   }
 }
 void* JavaThread::popframe_preserved_args() {
   return _popframe_preserved_args;
 }
 ByteSize JavaThread::popframe_preserved_args_size() {
   return in_ByteSize(_popframe_preserved_args_size);
 }
 WordSize JavaThread::popframe_preserved_args_size_in_words() {
   int sz = in_bytes(popframe_preserved_args_size());
   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
   return in_WordSize(sz / wordSize);
 }
 void JavaThread::popframe_free_preserved_args() {
   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args, mtThread);
   _popframe_preserved_args = NULL;
   _popframe_preserved_args_size = 0;
 }
 #ifndef PRODUCT
 void JavaThread::trace_frames() {
   tty->print_cr("[Describe stack]");
   int frame_no = 1;
   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
     tty->print("  %d. ", frame_no++);
     fst.current()->print_value_on(tty,this);
     tty->cr();
   }
 }
 class PrintAndVerifyOopClosure: public OopClosure {
  protected:
   template <class T> inline void do_oop_work(T* p) {
     oop obj = oopDesc::load_decode_heap_oop(p);
     if (obj == NULL) return;
     tty->print(INTPTR_FORMAT ": ", p);
     if (obj->is_oop_or_null()) {
       if (obj->is_objArray()) {
         tty->print_cr("valid objArray: " INTPTR_FORMAT, (oopDesc*) obj);
       } else {
         obj->print();
       }
     } else {
       tty->print_cr("invalid oop: " INTPTR_FORMAT, (oopDesc*) obj);
     }
     tty->cr();
   }
  public:
   virtual void do_oop(oop* p) { do_oop_work(p); }
   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
 };
 static void oops_print(frame* f, const RegisterMap *map) {
   PrintAndVerifyOopClosure print;
   f->print_value();
   f->oops_do(&print, NULL, NULL, (RegisterMap*)map);
 }
 // Print our all the locations that contain oops and whether they are
 // valid or not.  This useful when trying to find the oldest frame
 // where an oop has gone bad since the frame walk is from youngest to
 // oldest.
 void JavaThread::trace_oops() {
   tty->print_cr("[Trace oops]");
   frames_do(oops_print);
 }
 #ifdef ASSERT
 // Print or validate the layout of stack frames
 void JavaThread::print_frame_layout(int depth, bool validate_only) {
   ResourceMark rm;
   PRESERVE_EXCEPTION_MARK;
   FrameValues values;
   int frame_no = 0;
   for(StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
     fst.current()->describe(values, ++frame_no);
     if (depth == frame_no) break;
   }
   if (validate_only) {
     values.validate();
   } else {
     tty->print_cr("[Describe stack layout]");
     values.print(this);
   }
 }
 #endif
 void JavaThread::trace_stack_from(vframe* start_vf) {
   ResourceMark rm;
   int vframe_no = 1;
   for (vframe* f = start_vf; f; f = f->sender() ) {
     if (f->is_java_frame()) {
       javaVFrame::cast(f)->print_activation(vframe_no++);
     } else {
       f->print();
     }
     if (vframe_no > StackPrintLimit) {
       tty->print_cr("...<more frames>...");
       return;
     }
   }
 }
 void JavaThread::trace_stack() {
   if (!has_last_Java_frame()) return;
   ResourceMark rm;
   HandleMark   hm;
   RegisterMap reg_map(this);
   trace_stack_from(last_java_vframe(&reg_map));
 }
 #endif // PRODUCT
 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
   assert(reg_map != NULL, "a map must be given");
   frame f = last_frame();
   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender() ) {
     if (vf->is_java_frame()) return javaVFrame::cast(vf);
   }
   return NULL;
 }
 Klass* JavaThread::security_get_caller_class(int depth) {
   vframeStream vfst(this);
   vfst.security_get_caller_frame(depth);
   if (!vfst.at_end()) {
     return vfst.method()->method_holder();
   }
   return NULL;
 }
 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
   assert(thread->is_Compiler_thread(), "must be compiler thread");
   CompileBroker::compiler_thread_loop();
 }
 // Create a CompilerThread
 CompilerThread::CompilerThread(CompileQueue* queue, CompilerCounters* counters)
 : JavaThread(&compiler_thread_entry) {
   _env   = NULL;
   _log   = NULL;
   _task  = NULL;
   _queue = queue;
   _counters = counters;
   _buffer_blob = NULL;
   _scanned_nmethod = NULL;
   _compiler = NULL;
   // Compiler uses resource area for compilation, let's bias it to mtCompiler
   resource_area()->bias_to(mtCompiler);
 #ifndef PRODUCT
   _ideal_graph_printer = NULL;
 #endif
 }
 void CompilerThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
   JavaThread::oops_do(f, cld_f, cf);
   if (_scanned_nmethod != NULL && cf != NULL) {
     // Safepoints can occur when the sweeper is scanning an nmethod so
     // process it here to make sure it isn't unloaded in the middle of
     // a scan.
     cf->do_code_blob(_scanned_nmethod);
   }
 }
 // ======= Threads ========
 // The Threads class links together all active threads, and provides
 // operations over all threads.  It is protected by its own Mutex
 // lock, which is also used in other contexts to protect thread
 // operations from having the thread being operated on from exiting
 // and going away unexpectedly (e.g., safepoint synchronization)
 JavaThread* Threads::_thread_list = NULL;
 int         Threads::_number_of_threads = 0;
 int         Threads::_number_of_non_daemon_threads = 0;
 int         Threads::_return_code = 0;
 size_t      JavaThread::_stack_size_at_create = 0;
 #ifdef ASSERT
 bool        Threads::_vm_complete = false;
 #endif
 // All JavaThreads
 #define ALL_JAVA_THREADS(X) for (JavaThread* X = _thread_list; X; X = X->next())
 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
 void Threads::threads_do(ThreadClosure* tc) {
   assert_locked_or_safepoint(Threads_lock);
   // ALL_JAVA_THREADS iterates through all JavaThreads
   ALL_JAVA_THREADS(p) {
     tc->do_thread(p);
   }
   // Someday we could have a table or list of all non-JavaThreads.
   // For now, just manually iterate through them.
   tc->do_thread(VMThread::vm_thread());
   Universe::heap()->gc_threads_do(tc);
   WatcherThread *wt = WatcherThread::watcher_thread();
   // Strictly speaking, the following NULL check isn't sufficient to make sure
   // the data for WatcherThread is still valid upon being examined. However,
   // considering that WatchThread terminates when the VM is on the way to
   // exit at safepoint, the chance of the above is extremely small. The right
   // way to prevent termination of WatcherThread would be to acquire
   // Terminator_lock, but we can't do that without violating the lock rank
   // checking in some cases.
   if (wt != NULL)
     tc->do_thread(wt);
 #if INCLUDE_JFR
   Thread* sampler_thread = Jfr::sampler_thread();
   if (sampler_thread != NULL) {
     tc->do_thread(sampler_thread);
   }
 #endif
   // If CompilerThreads ever become non-JavaThreads, add them here
 }
 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
   extern void JDK_Version_init();
   // Preinitialize version info.
   VM_Version::early_initialize();
   // Check version
   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
   // Initialize the output stream module
   ostream_init();
   // Process java launcher properties.
   Arguments::process_sun_java_launcher_properties(args);
   // Initialize the os module before using TLS
   os::init();
   // Initialize system properties.
   Arguments::init_system_properties();
   // So that JDK version can be used as a discrimintor when parsing arguments
   JDK_Version_init();
   // Update/Initialize System properties after JDK version number is known
   Arguments::init_version_specific_system_properties();
   // Parse arguments
   // Note: this internally calls os::init_container_support()
   jint parse_result = Arguments::parse(args);
   if (parse_result != JNI_OK) return parse_result;
   os::init_before_ergo();
   jint ergo_result = Arguments::apply_ergo();
   if (ergo_result != JNI_OK) return ergo_result;
   if (PauseAtStartup) {
     os::pause();
   }
 #ifndef USDT2
   HS_DTRACE_PROBE(hotspot, vm__init__begin);
 #else /* USDT2 */
   HOTSPOT_VM_INIT_BEGIN();
 #endif /* USDT2 */
   // Record VM creation timing statistics
   TraceVmCreationTime create_vm_timer;
   create_vm_timer.start();
   // Timing (must come after argument parsing)
   TraceTime timer("Create VM", TraceStartupTime);
   // Initialize the os module after parsing the args
   jint os_init_2_result = os::init_2();
   if (os_init_2_result != JNI_OK) return os_init_2_result;
   jint adjust_after_os_result = Arguments::adjust_after_os();
   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
   // intialize TLS
   ThreadLocalStorage::init();
   // Initialize output stream logging
   ostream_init_log();
   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
   // Must be before create_vm_init_agents()
   if (Arguments::init_libraries_at_startup()) {
     convert_vm_init_libraries_to_agents();
   }
   // Launch -agentlib/-agentpath and converted -Xrun agents
   if (Arguments::init_agents_at_startup()) {
     create_vm_init_agents();
   }
   // Initialize Threads state
   _thread_list = NULL;
   _number_of_threads = 0;
   _number_of_non_daemon_threads = 0;
   // Initialize global data structures and create system classes in heap
   vm_init_globals();
   // Attach the main thread to this os thread
   JavaThread* main_thread = new JavaThread();
   main_thread->set_thread_state(_thread_in_vm);
   // must do this before set_active_handles and initialize_thread_local_storage
   // Note: on solaris initialize_thread_local_storage() will (indirectly)
   // change the stack size recorded here to one based on the java thread
   // stacksize. This adjusted size is what is used to figure the placement
   // of the guard pages.
   main_thread->record_stack_base_and_size();
   main_thread->initialize_thread_local_storage();
   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
   if (!main_thread->set_as_starting_thread()) {
     vm_shutdown_during_initialization(
       "Failed necessary internal allocation. Out of swap space");
     delete main_thread;
     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
     return JNI_ENOMEM;
   }
   // Enable guard page *after* os::create_main_thread(), otherwise it would
   // crash Linux VM, see notes in os_linux.cpp.
   main_thread->create_stack_guard_pages();
   // Initialize Java-Level synchronization subsystem
   ObjectMonitor::Initialize() ;
   // Initialize global modules
   jint status = init_globals();
   if (status != JNI_OK) {
     delete main_thread;
     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
     return status;
   }
   JFR_ONLY(Jfr::on_vm_init();)
   // Should be done after the heap is fully created
   main_thread->cache_global_variables();
   HandleMark hm;
   { MutexLocker mu(Threads_lock);
     Threads::add(main_thread);
   }
   // Any JVMTI raw monitors entered in onload will transition into
   // real raw monitor. VM is setup enough here for raw monitor enter.
   JvmtiExport::transition_pending_onload_raw_monitors();
   // Create the VMThread
   { TraceTime timer("Start VMThread", TraceStartupTime);
     VMThread::create();
     Thread* vmthread = VMThread::vm_thread();
     if (!os::create_thread(vmthread, os::vm_thread))
       vm_exit_during_initialization("Cannot create VM thread. Out of system resources.");
     // Wait for the VM thread to become ready, and VMThread::run to initialize
     // Monitors can have spurious returns, must always check another state flag
     {
       MutexLocker ml(Notify_lock);
       os::start_thread(vmthread);
       while (vmthread->active_handles() == NULL) {
         Notify_lock->wait();
       }
     }
   }
   assert (Universe::is_fully_initialized(), "not initialized");
   if (VerifyDuringStartup) {
     // Make sure we're starting with a clean slate.
     VM_Verify verify_op;
     VMThread::execute(&verify_op);
   }
   EXCEPTION_MARK;
   // At this point, the Universe is initialized, but we have not executed
   // any byte code.  Now is a good time (the only time) to dump out the
   // internal state of the JVM for sharing.
   if (DumpSharedSpaces) {
     MetaspaceShared::preload_and_dump(CHECK_0);
     ShouldNotReachHere();
   }
   // Always call even when there are not JVMTI environments yet, since environments
   // may be attached late and JVMTI must track phases of VM execution
   JvmtiExport::enter_start_phase();
   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
   JvmtiExport::post_vm_start();
   {
     TraceTime timer("Initialize java.lang classes", TraceStartupTime);
     if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
       create_vm_init_libraries();
     }
     initialize_class(vmSymbols::java_lang_String(), CHECK_0);
     // Initialize java_lang.System (needed before creating the thread)
     initialize_class(vmSymbols::java_lang_System(), CHECK_0);
     initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK_0);
     Handle thread_group = create_initial_thread_group(CHECK_0);
     Universe::set_main_thread_group(thread_group());
     initialize_class(vmSymbols::java_lang_Thread(), CHECK_0);
     oop thread_object = create_initial_thread(thread_group, main_thread, CHECK_0);
     main_thread->set_threadObj(thread_object);
     // Set thread status to running since main thread has
     // been started and running.
     java_lang_Thread::set_thread_status(thread_object,
                                         java_lang_Thread::RUNNABLE);
     // The VM creates & returns objects of this class. Make sure it's initialized.
     initialize_class(vmSymbols::java_lang_Class(), CHECK_0);
     // The VM preresolves methods to these classes. Make sure that they get initialized
     initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK_0);
     initialize_class(vmSymbols::java_lang_ref_Finalizer(),  CHECK_0);
     call_initializeSystemClass(CHECK_0);
     // get the Java runtime name after java.lang.System is initialized
     JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
     JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
     // an instance of OutOfMemory exception has been allocated earlier
     initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK_0);
     initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK_0);
     initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK_0);
     initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK_0);
     initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK_0);
     initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK_0);
     initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK_0);
     initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK_0);
   }
   // See        : bugid 4211085.
   // Background : the static initializer of java.lang.Compiler tries to read
   //              property"java.compiler" and read & write property "java.vm.info".
   //              When a security manager is installed through the command line
   //              option "-Djava.security.manager", the above properties are not
   //              readable and the static initializer for java.lang.Compiler fails
   //              resulting in a NoClassDefFoundError.  This can happen in any
   //              user code which calls methods in java.lang.Compiler.
   // Hack :       the hack is to pre-load and initialize this class, so that only
   //              system domains are on the stack when the properties are read.
   //              Currently even the AWT code has calls to methods in java.lang.Compiler.
   //              On the classic VM, java.lang.Compiler is loaded very early to load the JIT.
   // Future Fix : the best fix is to grant everyone permissions to read "java.compiler" and
   //              read and write"java.vm.info" in the default policy file. See bugid 4211383
   //              Once that is done, we should remove this hack.
   initialize_class(vmSymbols::java_lang_Compiler(), CHECK_0);
   // More hackery - the static initializer of java.lang.Compiler adds the string "nojit" to
   // the java.vm.info property if no jit gets loaded through java.lang.Compiler (the hotspot
   // compiler does not get loaded through java.lang.Compiler).  "java -version" with the
   // hotspot vm says "nojit" all the time which is confusing.  So, we reset it here.
   // This should also be taken out as soon as 4211383 gets fixed.
   reset_vm_info_property(CHECK_0);
   quicken_jni_functions();
   // Set flag that basic initialization has completed. Used by exceptions and various
   // debug stuff, that does not work until all basic classes have been initialized.
   set_init_completed();
   Metaspace::post_initialize();
 #ifndef USDT2
   HS_DTRACE_PROBE(hotspot, vm__init__end);
 #else /* USDT2 */
   HOTSPOT_VM_INIT_END();
 #endif /* USDT2 */
   // record VM initialization completion time
 #if INCLUDE_MANAGEMENT
   Management::record_vm_init_completed();
 #endif // INCLUDE_MANAGEMENT
   // Compute system loader. Note that this has to occur after set_init_completed, since
   // valid exceptions may be thrown in the process.
   // Note that we do not use CHECK_0 here since we are inside an EXCEPTION_MARK and
   // set_init_completed has just been called, causing exceptions not to be shortcut
   // anymore. We call vm_exit_during_initialization directly instead.
   SystemDictionary::compute_java_system_loader(THREAD);
   if (HAS_PENDING_EXCEPTION) {
     vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
   }
 #if INCLUDE_ALL_GCS
   // Support for ConcurrentMarkSweep. This should be cleaned up
   // and better encapsulated. The ugly nested if test would go away
   // once things are properly refactored. XXX YSR
   if (UseConcMarkSweepGC || UseG1GC) {
     if (UseConcMarkSweepGC) {
       ConcurrentMarkSweepThread::makeSurrogateLockerThread(THREAD);
     } else {
       ConcurrentMarkThread::makeSurrogateLockerThread(THREAD);
     }
     if (HAS_PENDING_EXCEPTION) {
       vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
     }
   }
 #endif // INCLUDE_ALL_GCS
   // Always call even when there are not JVMTI environments yet, since environments
   // may be attached late and JVMTI must track phases of VM execution
   JvmtiExport::enter_live_phase();
   // Signal Dispatcher needs to be started before VMInit event is posted
   os::signal_init();
   // Start Attach Listener if +StartAttachListener or it can't be started lazily
   if (!DisableAttachMechanism) {
     AttachListener::vm_start();
     if (StartAttachListener || AttachListener::init_at_startup()) {
       AttachListener::init();
     }
   }
   // Launch -Xrun agents
   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
   // back-end can launch with -Xdebug -Xrunjdwp.
   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
     create_vm_init_libraries();
   }
   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
   JvmtiExport::post_vm_initialized();
   JFR_ONLY(Jfr::on_vm_start();)
   if (CleanChunkPoolAsync) {
     Chunk::start_chunk_pool_cleaner_task();
   }
   // initialize compiler(s)
 #if defined(COMPILER1) || defined(COMPILER2) || defined(SHARK)
   CompileBroker::compilation_init();
 #endif
   if (EnableInvokeDynamic) {
     // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
     // It is done after compilers are initialized, because otherwise compilations of
     // signature polymorphic MH intrinsics can be missed
     // (see SystemDictionary::find_method_handle_intrinsic).
     initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK_0);
     initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK_0);
     initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK_0);
   }
 #if INCLUDE_MANAGEMENT
   Management::initialize(THREAD);
 #endif // INCLUDE_MANAGEMENT
   if (HAS_PENDING_EXCEPTION) {
     // management agent fails to start possibly due to
     // configuration problem and is responsible for printing
     // stack trace if appropriate. Simply exit VM.
     vm_exit(1);
   }
   if (Arguments::has_profile())       FlatProfiler::engage(main_thread, true);
   if (MemProfiling)                   MemProfiler::engage();
   StatSampler::engage();
   if (CheckJNICalls)                  JniPeriodicChecker::engage();
   BiasedLocking::init();
 #if INCLUDE_RTM_OPT
   RTMLockingCounters::init();
 #endif
   if (JDK_Version::current().post_vm_init_hook_enabled()) {
     call_postVMInitHook(THREAD);
     // The Java side of PostVMInitHook.run must deal with all
     // exceptions and provide means of diagnosis.
     if (HAS_PENDING_EXCEPTION) {
       CLEAR_PENDING_EXCEPTION;
     }
   }
   {
       MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
       // Make sure the watcher thread can be started by WatcherThread::start()
       // or by dynamic enrollment.
       WatcherThread::make_startable();
       // Start up the WatcherThread if there are any periodic tasks
       // NOTE:  All PeriodicTasks should be registered by now. If they
       //   aren't, late joiners might appear to start slowly (we might
       //   take a while to process their first tick).
       if (PeriodicTask::num_tasks() > 0) {
           WatcherThread::start();
       }
   }
   create_vm_timer.end();
 #ifdef ASSERT
   _vm_complete = true;
 #endif
   return JNI_OK;
 }
 // type for the Agent_OnLoad and JVM_OnLoad entry points
 extern "C" {
   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
 }
 // Find a command line agent library and return its entry point for
 //         -agentlib:  -agentpath:   -Xrun
 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent, const char *on_load_symbols[], size_t num_symbol_entries) {
   OnLoadEntry_t on_load_entry = NULL;
   void *library = NULL;
   if (!agent->valid()) {
     char buffer[JVM_MAXPATHLEN];
     char ebuf[1024];
     const char *name = agent->name();
     const char *msg = "Could not find agent library ";
     // First check to see if agent is statically linked into executable
     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
       library = agent->os_lib();
     } else if (agent->is_absolute_path()) {
       library = os::dll_load(name, ebuf, sizeof ebuf);
       if (library == NULL) {
         const char *sub_msg = " in absolute path, with error: ";
         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
         char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
         // If we can't find the agent, exit.
         vm_exit_during_initialization(buf, NULL);
         FREE_C_HEAP_ARRAY(char, buf, mtThread);
       }
     } else {
       // Try to load the agent from the standard dll directory
       if (os::dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(),
                              name)) {
         library = os::dll_load(buffer, ebuf, sizeof ebuf);
       }
       if (library == NULL) { // Try the local directory
         char ns[1] = {0};
         if (os::dll_build_name(buffer, sizeof(buffer), ns, name)) {
           library = os::dll_load(buffer, ebuf, sizeof ebuf);
         }
         if (library == NULL) {
           const char *sub_msg = " on the library path, with error: ";
           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
           char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
           jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
           // If we can't find the agent, exit.
           vm_exit_during_initialization(buf, NULL);
           FREE_C_HEAP_ARRAY(char, buf, mtThread);
         }
       }
     }
     agent->set_os_lib(library);
     agent->set_valid();
   }
   // Find the OnLoad function.
   on_load_entry =
     CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
                                                           false,
                                                           on_load_symbols,
                                                           num_symbol_entries));
   return on_load_entry;
 }
 // Find the JVM_OnLoad entry point
 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
 }
 // Find the Agent_OnLoad entry point
 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
 }
 // For backwards compatibility with -Xrun
 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
 // treated like -agentpath:
 // Must be called before agent libraries are created
 void Threads::convert_vm_init_libraries_to_agents() {
   AgentLibrary* agent;
   AgentLibrary* next;
   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
     next = agent->next();  // cache the next agent now as this agent may get moved off this list
     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
     // If there is an JVM_OnLoad function it will get called later,
     // otherwise see if there is an Agent_OnLoad
     if (on_load_entry == NULL) {
       on_load_entry = lookup_agent_on_load(agent);
       if (on_load_entry != NULL) {
         // switch it to the agent list -- so that Agent_OnLoad will be called,
         // JVM_OnLoad won't be attempted and Agent_OnUnload will
         Arguments::convert_library_to_agent(agent);
       } else {
         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
       }
     }
   }
 }
 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
 // Invokes Agent_OnLoad
 // Called very early -- before JavaThreads exist
 void Threads::create_vm_init_agents() {
   extern struct JavaVM_ main_vm;
   AgentLibrary* agent;
   JvmtiExport::enter_onload_phase();
   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
     if (on_load_entry != NULL) {
       // Invoke the Agent_OnLoad function
       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
       if (err != JNI_OK) {
         vm_exit_during_initialization("agent library failed to init", agent->name());
       }
     } else {
       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
     }
   }
   JvmtiExport::enter_primordial_phase();
 }
 extern "C" {
   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
 }
 void Threads::shutdown_vm_agents() {
   // Send any Agent_OnUnload notifications
   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
   size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
   extern struct JavaVM_ main_vm;
   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
     // Find the Agent_OnUnload function.
     Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
       os::find_agent_function(agent,
       false,
       on_unload_symbols,
       num_symbol_entries));
     // Invoke the Agent_OnUnload function
     if (unload_entry != NULL) {
       JavaThread* thread = JavaThread::current();
       ThreadToNativeFromVM ttn(thread);
       HandleMark hm(thread);
       (*unload_entry)(&main_vm);
     }
   }
 }
 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
 // Invokes JVM_OnLoad
 void Threads::create_vm_init_libraries() {
   extern struct JavaVM_ main_vm;
   AgentLibrary* agent;
   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
     if (on_load_entry != NULL) {
       // Invoke the JVM_OnLoad function
       JavaThread* thread = JavaThread::current();
       ThreadToNativeFromVM ttn(thread);
       HandleMark hm(thread);
       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
       if (err != JNI_OK) {
         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
       }
     } else {
       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
     }
   }
 }
 JavaThread* Threads::find_java_thread_from_java_tid(jlong java_tid) {
   assert(Threads_lock->owned_by_self(), "Must hold Threads_lock");
   JavaThread* java_thread = NULL;
   // Sequential search for now.  Need to do better optimization later.
   for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
     oop tobj = thread->threadObj();
     if (!thread->is_exiting() &&
         tobj != NULL &&
         java_tid == java_lang_Thread::thread_id(tobj)) {
       java_thread = thread;
       break;
     }
   }
   return java_thread;
 }
 // Last thread running calls java.lang.Shutdown.shutdown()
 void JavaThread::invoke_shutdown_hooks() {
   HandleMark hm(this);
   // We could get here with a pending exception, if so clear it now.
   if (this->has_pending_exception()) {
     this->clear_pending_exception();
   }
   EXCEPTION_MARK;
   Klass* k =
     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
                                       THREAD);
   if (k != NULL) {
     // SystemDictionary::resolve_or_null will return null if there was
     // an exception.  If we cannot load the Shutdown class, just don't
     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
     // and finalizers (if runFinalizersOnExit is set) won't be run.
     // Note that if a shutdown hook was registered or runFinalizersOnExit
     // was called, the Shutdown class would have already been loaded
     // (Runtime.addShutdownHook and runFinalizersOnExit will load it).
     instanceKlassHandle shutdown_klass (THREAD, k);
     JavaValue result(T_VOID);
     JavaCalls::call_static(&result,
                            shutdown_klass,
                            vmSymbols::shutdown_method_name(),
                            vmSymbols::void_method_signature(),
                            THREAD);
   }
   CLEAR_PENDING_EXCEPTION;
 }
 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
 // the program falls off the end of main(). Another VM exit path is through
 // vm_exit() when the program calls System.exit() to return a value or when
 // there is a serious error in VM. The two shutdown paths are not exactly
 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
 // and VM_Exit op at VM level.
 //
 // Shutdown sequence:
 //   + Shutdown native memory tracking if it is on
 //   + Wait until we are the last non-daemon thread to execute
 //     <-- every thing is still working at this moment -->
 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
 //        shutdown hooks, run finalizers if finalization-on-exit
 //   + Call before_exit(), prepare for VM exit
 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
 //        currently the only user of this mechanism is File.deleteOnExit())
 //      > stop flat profiler, StatSampler, watcher thread, CMS threads,
 //        post thread end and vm death events to JVMTI,
 //        stop signal thread
 //   + Call JavaThread::exit(), it will:
 //      > release JNI handle blocks, remove stack guard pages
 //      > remove this thread from Threads list
 //     <-- no more Java code from this thread after this point -->
 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
 //     the compiler threads at safepoint
 //     <-- do not use anything that could get blocked by Safepoint -->
 //   + Disable tracing at JNI/JVM barriers
 //   + Set _vm_exited flag for threads that are still running native code
 //   + Delete this thread
 //   + Call exit_globals()
 //      > deletes tty
 //      > deletes PerfMemory resources
 //   + Return to caller
 bool Threads::destroy_vm() {
   JavaThread* thread = JavaThread::current();
 #ifdef ASSERT
   _vm_complete = false;
 #endif
   // Wait until we are the last non-daemon thread to execute
   { MutexLocker nu(Threads_lock);
     while (Threads::number_of_non_daemon_threads() > 1 )
       // This wait should make safepoint checks, wait without a timeout,
       // and wait as a suspend-equivalent condition.
       //
       // Note: If the FlatProfiler is running and this thread is waiting
       // for another non-daemon thread to finish, then the FlatProfiler
       // is waiting for the external suspend request on this thread to
       // complete. wait_for_ext_suspend_completion() will eventually
       // timeout, but that takes time. Making this wait a suspend-
       // equivalent condition solves that timeout problem.
       //
       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
                          Mutex::_as_suspend_equivalent_flag);
   }
   EventShutdown e;
   if (e.should_commit()) {
     e.set_reason("No remaining non-daemon Java threads");
     e.commit();
   }
   // Hang forever on exit if we are reporting an error.
   if (ShowMessageBoxOnError && is_error_reported()) {
     os::infinite_sleep();
   }
   os::wait_for_keypress_at_exit();
   if (JDK_Version::is_jdk12x_version()) {
     // We are the last thread running, so check if finalizers should be run.
     // For 1.3 or later this is done in thread->invoke_shutdown_hooks()
     HandleMark rm(thread);
     Universe::run_finalizers_on_exit();
   } else {
     // run Java level shutdown hooks
     thread->invoke_shutdown_hooks();
   }
   before_exit(thread);
   thread->exit(true);
   // Stop VM thread.
   {
     // 4945125 The vm thread comes to a safepoint during exit.
     // GC vm_operations can get caught at the safepoint, and the
     // heap is unparseable if they are caught. Grab the Heap_lock
     // to prevent this. The GC vm_operations will not be able to
     // queue until after the vm thread is dead. After this point,
     // we'll never emerge out of the safepoint before the VM exits.
     MutexLocker ml(Heap_lock);
     VMThread::wait_for_vm_thread_exit();
     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
     VMThread::destroy();
   }
   // clean up ideal graph printers
 #if defined(COMPILER2) && !defined(PRODUCT)
   IdealGraphPrinter::clean_up();
 #endif
   // Now, all Java threads are gone except daemon threads. Daemon threads
   // running Java code or in VM are stopped by the Safepoint. However,
   // daemon threads executing native code are still running.  But they
   // will be stopped at native=>Java/VM barriers. Note that we can't
   // simply kill or suspend them, as it is inherently deadlock-prone.
 #ifndef PRODUCT
   // disable function tracing at JNI/JVM barriers
   TraceJNICalls = false;
   TraceJVMCalls = false;
   TraceRuntimeCalls = false;
 #endif
   VM_Exit::set_vm_exited();
   notify_vm_shutdown();
   delete thread;
   // exit_globals() will delete tty
   exit_globals();
   return true;
 }
 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
   if (version == JNI_VERSION_1_1) return JNI_TRUE;
   return is_supported_jni_version(version);
 }
 jboolean Threads::is_supported_jni_version(jint version) {
   if (version == JNI_VERSION_1_2) return JNI_TRUE;
   if (version == JNI_VERSION_1_4) return JNI_TRUE;
   if (version == JNI_VERSION_1_6) return JNI_TRUE;
   if (version == JNI_VERSION_1_8) return JNI_TRUE;
   return JNI_FALSE;
 }
 void Threads::add(JavaThread* p, bool force_daemon) {
   // The threads lock must be owned at this point
   assert_locked_or_safepoint(Threads_lock);
   // See the comment for this method in thread.hpp for its purpose and
   // why it is called here.
   p->initialize_queues();
   p->set_next(_thread_list);
   _thread_list = p;
   _number_of_threads++;
   oop threadObj = p->threadObj();
   bool daemon = true;
   // Bootstrapping problem: threadObj can be null for initial
   // JavaThread (or for threads attached via JNI)
   if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
     _number_of_non_daemon_threads++;
     daemon = false;
   }
   ThreadService::add_thread(p, daemon);
   // Possible GC point.
   Events::log(p, "Thread added: " INTPTR_FORMAT, p);
 }
 void Threads::remove(JavaThread* p) {
   // Extra scope needed for Thread_lock, so we can check
   // that we do not remove thread without safepoint code notice
   { MutexLocker ml(Threads_lock);
     assert(includes(p), "p must be present");
     JavaThread* current = _thread_list;
     JavaThread* prev    = NULL;
     while (current != p) {
       prev    = current;
       current = current->next();
     }
     if (prev) {
       prev->set_next(current->next());
     } else {
       _thread_list = p->next();
     }
     _number_of_threads--;
     oop threadObj = p->threadObj();
     bool daemon = true;
     if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
       _number_of_non_daemon_threads--;
       daemon = false;
       // Only one thread left, do a notify on the Threads_lock so a thread waiting
       // on destroy_vm will wake up.
       if (number_of_non_daemon_threads() == 1)
         Threads_lock->notify_all();
     }
     ThreadService::remove_thread(p, daemon);
     // Make sure that safepoint code disregard this thread. This is needed since
     // the thread might mess around with locks after this point. This can cause it
     // to do callbacks into the safepoint code. However, the safepoint code is not aware
     // of this thread since it is removed from the queue.
     p->set_terminated_value();
   } // unlock Threads_lock
   // Since Events::log uses a lock, we grab it outside the Threads_lock
   Events::log(p, "Thread exited: " INTPTR_FORMAT, p);
 }
 // Threads_lock must be held when this is called (or must be called during a safepoint)
 bool Threads::includes(JavaThread* p) {
   assert(Threads_lock->is_locked(), "sanity check");
   ALL_JAVA_THREADS(q) {
     if (q == p ) {
       return true;
     }
   }
   return false;
 }
 // Operations on the Threads list for GC.  These are not explicitly locked,
 // but the garbage collector must provide a safe context for them to run.
 // In particular, these things should never be called when the Threads_lock
 // is held by some other thread. (Note: the Safepoint abstraction also
 // uses the Threads_lock to gurantee this property. It also makes sure that
 // all threads gets blocked when exiting or starting).
 void Threads::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
   ALL_JAVA_THREADS(p) {
     p->oops_do(f, cld_f, cf);
   }
   VMThread::vm_thread()->oops_do(f, cld_f, cf);
 }
 void Threads::possibly_parallel_oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
   // Introduce a mechanism allowing parallel threads to claim threads as
   // root groups.  Overhead should be small enough to use all the time,
   // even in sequential code.
   SharedHeap* sh = SharedHeap::heap();
   // Cannot yet substitute active_workers for n_par_threads
   // because of G1CollectedHeap::verify() use of
   // SharedHeap::process_roots().  n_par_threads == 0 will
   // turn off parallelism in process_roots while active_workers
   // is being used for parallelism elsewhere.
   bool is_par = sh->n_par_threads() > 0;
   assert(!is_par ||
          (SharedHeap::heap()->n_par_threads() ==
           SharedHeap::heap()->workers()->active_workers()), "Mismatch");
   int cp = SharedHeap::heap()->strong_roots_parity();
   ALL_JAVA_THREADS(p) {
     if (p->claim_oops_do(is_par, cp)) {
       p->oops_do(f, cld_f, cf);
     }
   }
   VMThread* vmt = VMThread::vm_thread();
   if (vmt->claim_oops_do(is_par, cp)) {
     vmt->oops_do(f, cld_f, cf);
   }
 }
 #if INCLUDE_ALL_GCS
 // Used by ParallelScavenge
 void Threads::create_thread_roots_tasks(GCTaskQueue* q) {
   ALL_JAVA_THREADS(p) {
     q->enqueue(new ThreadRootsTask(p));
   }
   q->enqueue(new ThreadRootsTask(VMThread::vm_thread()));
 }
 // Used by Parallel Old
 void Threads::create_thread_roots_marking_tasks(GCTaskQueue* q) {
   ALL_JAVA_THREADS(p) {
     q->enqueue(new ThreadRootsMarkingTask(p));
   }
   q->enqueue(new ThreadRootsMarkingTask(VMThread::vm_thread()));
 }
 #endif // INCLUDE_ALL_GCS
 void Threads::nmethods_do(CodeBlobClosure* cf) {
   ALL_JAVA_THREADS(p) {
     p->nmethods_do(cf);
   }
   VMThread::vm_thread()->nmethods_do(cf);
 }
 void Threads::metadata_do(void f(Metadata*)) {
   ALL_JAVA_THREADS(p) {
     p->metadata_do(f);
   }
 }
 void Threads::gc_epilogue() {
   ALL_JAVA_THREADS(p) {
     p->gc_epilogue();
   }
 }
 void Threads::gc_prologue() {
   ALL_JAVA_THREADS(p) {
     p->gc_prologue();
   }
 }
 void Threads::deoptimized_wrt_marked_nmethods() {
   ALL_JAVA_THREADS(p) {
     p->deoptimized_wrt_marked_nmethods();
   }
 }
 // Get count Java threads that are waiting to enter the specified monitor.
 GrowableArray<JavaThread*>* Threads::get_pending_threads(int count,
   address monitor, bool doLock) {
   assert(doLock || SafepointSynchronize::is_at_safepoint(),
     "must grab Threads_lock or be at safepoint");
   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
   int i = 0;
   {
     MutexLockerEx ml(doLock ? Threads_lock : NULL);
     ALL_JAVA_THREADS(p) {
       if (p->is_Compiler_thread()) continue;
       address pending = (address)p->current_pending_monitor();
       if (pending == monitor) {             // found a match
         if (i < count) result->append(p);   // save the first count matches
         i++;
       }
     }
   }
   return result;
 }
 JavaThread *Threads::owning_thread_from_monitor_owner(address owner, bool doLock) {
   assert(doLock ||
          Threads_lock->owned_by_self() ||
          SafepointSynchronize::is_at_safepoint(),
          "must grab Threads_lock or be at safepoint");
   // NULL owner means not locked so we can skip the search
   if (owner == NULL) return NULL;
   {
     MutexLockerEx ml(doLock ? Threads_lock : NULL);
     ALL_JAVA_THREADS(p) {
       // first, see if owner is the address of a Java thread
       if (owner == (address)p) return p;
     }
   }
   // Cannot assert on lack of success here since this function may be
   // used by code that is trying to report useful problem information
   // like deadlock detection.
   if (UseHeavyMonitors) return NULL;
   //
   // If we didn't find a matching Java thread and we didn't force use of
   // heavyweight monitors, then the owner is the stack address of the
   // Lock Word in the owning Java thread's stack.
   //
   JavaThread* the_owner = NULL;
   {
     MutexLockerEx ml(doLock ? Threads_lock : NULL);
     ALL_JAVA_THREADS(q) {
       if (q->is_lock_owned(owner)) {
         the_owner = q;
         break;
       }
     }
   }
   // cannot assert on lack of success here; see above comment
   return the_owner;
 }
 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
 void Threads::print_on(outputStream* st, bool print_stacks, bool internal_format, bool print_concurrent_locks) {
   char buf[32];
   st->print_cr("%s", os::local_time_string(buf, sizeof(buf)));
   st->print_cr("Full thread dump %s (%s %s):",
                 Abstract_VM_Version::vm_name(),
                 Abstract_VM_Version::vm_release(),
                 Abstract_VM_Version::vm_info_string()
                );
   st->cr();
 #if INCLUDE_ALL_GCS
   // Dump concurrent locks
   ConcurrentLocksDump concurrent_locks;
   if (print_concurrent_locks) {
     concurrent_locks.dump_at_safepoint();
   }
 #endif // INCLUDE_ALL_GCS
   ALL_JAVA_THREADS(p) {
     ResourceMark rm;
     p->print_on(st);
     if (print_stacks) {
       if (internal_format) {
         p->trace_stack();
       } else {
         p->print_stack_on(st);
       }
     }
     st->cr();
 #if INCLUDE_ALL_GCS
     if (print_concurrent_locks) {
       concurrent_locks.print_locks_on(p, st);
     }
 #endif // INCLUDE_ALL_GCS
   }
   VMThread::vm_thread()->print_on(st);
   st->cr();
   Universe::heap()->print_gc_threads_on(st);
   WatcherThread* wt = WatcherThread::watcher_thread();
   if (wt != NULL) {
     wt->print_on(st);
     st->cr();
   }
   CompileBroker::print_compiler_threads_on(st);
   st->flush();
 }
 // Threads::print_on_error() is called by fatal error handler. It's possible
 // that VM is not at safepoint and/or current thread is inside signal handler.
 // Don't print stack trace, as the stack may not be walkable. Don't allocate
 // memory (even in resource area), it might deadlock the error handler.
 void Threads::print_on_error(outputStream* st, Thread* current, char* buf, int buflen) {
   bool found_current = false;
   st->print_cr("Java Threads: ( => current thread )");
   ALL_JAVA_THREADS(thread) {
     bool is_current = (current == thread);
     found_current = found_current || is_current;
     st->print("%s", is_current ? "=>" : "  ");
     st->print(PTR_FORMAT, thread);
     st->print(" ");
     thread->print_on_error(st, buf, buflen);
     st->cr();
   }
   st->cr();
   st->print_cr("Other Threads:");
   if (VMThread::vm_thread()) {
     bool is_current = (current == VMThread::vm_thread());
     found_current = found_current || is_current;
     st->print("%s", current == VMThread::vm_thread() ? "=>" : "  ");
     st->print(PTR_FORMAT, VMThread::vm_thread());
     st->print(" ");
     VMThread::vm_thread()->print_on_error(st, buf, buflen);
     st->cr();
   }
   WatcherThread* wt = WatcherThread::watcher_thread();
   if (wt != NULL) {
     bool is_current = (current == wt);
     found_current = found_current || is_current;
     st->print("%s", is_current ? "=>" : "  ");
     st->print(PTR_FORMAT, wt);
     st->print(" ");
     wt->print_on_error(st, buf, buflen);
     st->cr();
   }
   if (!found_current) {
     st->cr();
     st->print("=>" PTR_FORMAT " (exited) ", current);
     current->print_on_error(st, buf, buflen);
     st->cr();
   }
 }
 // Internal SpinLock and Mutex
 // Based on ParkEvent
 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
 //
 // We employ SpinLocks _only for low-contention, fixed-length
 // short-duration critical sections where we're concerned
 // about native mutex_t or HotSpot Mutex:: latency.
 // The mux construct provides a spin-then-block mutual exclusion
 // mechanism.
 //
 // Testing has shown that contention on the ListLock guarding gFreeList
 // is common.  If we implement ListLock as a simple SpinLock it's common
 // for the JVM to devolve to yielding with little progress.  This is true
 // despite the fact that the critical sections protected by ListLock are
 // extremely short.
 //
 // TODO-FIXME: ListLock should be of type SpinLock.
 // We should make this a 1st-class type, integrated into the lock
 // hierarchy as leaf-locks.  Critically, the SpinLock structure
 // should have sufficient padding to avoid false-sharing and excessive
 // cache-coherency traffic.
 typedef volatile int SpinLockT ;
 void Thread::SpinAcquire (volatile int * adr, const char * LockName) {
   if (Atomic::cmpxchg (1, adr, 0) == 0) {
      return ;   // normal fast-path return
   }
   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
   TEVENT (SpinAcquire - ctx) ;
   int ctr = 0 ;
   int Yields = 0 ;
   for (;;) {
      while (*adr != 0) {
         ++ctr ;
         if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
            if (Yields > 5) {
              os::naked_short_sleep(1);
            } else {
              os::NakedYield() ;
              ++Yields ;
            }
         } else {
            SpinPause() ;
         }
      }
      if (Atomic::cmpxchg (1, adr, 0) == 0) return ;
   }
 }
 void Thread::SpinRelease (volatile int * adr) {
   assert (*adr != 0, "invariant") ;
   OrderAccess::fence() ;      // guarantee at least release consistency.
   // Roach-motel semantics.
   // It's safe if subsequent LDs and STs float "up" into the critical section,
   // but prior LDs and STs within the critical section can't be allowed
   // to reorder or float past the ST that releases the lock.
   *adr = 0 ;
 }
 // muxAcquire and muxRelease:
 //
 // *  muxAcquire and muxRelease support a single-word lock-word construct.
 //    The LSB of the word is set IFF the lock is held.
 //    The remainder of the word points to the head of a singly-linked list
 //    of threads blocked on the lock.
 //
 // *  The current implementation of muxAcquire-muxRelease uses its own
 //    dedicated Thread._MuxEvent instance.  If we're interested in
 //    minimizing the peak number of extant ParkEvent instances then
 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
 //    as certain invariants were satisfied.  Specifically, care would need
 //    to be taken with regards to consuming unpark() "permits".
 //    A safe rule of thumb is that a thread would never call muxAcquire()
 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
 //    consume an unpark() permit intended for monitorenter, for instance.
 //    One way around this would be to widen the restricted-range semaphore
 //    implemented in park().  Another alternative would be to provide
 //    multiple instances of the PlatformEvent() for each thread.  One
 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
 //
 // *  Usage:
 //    -- Only as leaf locks
 //    -- for short-term locking only as muxAcquire does not perform
 //       thread state transitions.
 //
 // Alternatives:
 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
 //    but with parking or spin-then-park instead of pure spinning.
 // *  Use Taura-Oyama-Yonenzawa locks.
 // *  It's possible to construct a 1-0 lock if we encode the lockword as
 //    (List,LockByte).  Acquire will CAS the full lockword while Release
 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
 //    acquiring threads use timers (ParkTimed) to detect and recover from
 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
 //    boundaries by using placement-new.
 // *  Augment MCS with advisory back-link fields maintained with CAS().
 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
 //    The validity of the backlinks must be ratified before we trust the value.
 //    If the backlinks are invalid the exiting thread must back-track through the
 //    the forward links, which are always trustworthy.
 // *  Add a successor indication.  The LockWord is currently encoded as
 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
 //    to provide the usual futile-wakeup optimization.
 //    See RTStt for details.
 // *  Consider schedctl.sc_nopreempt to cover the critical section.
 //
 typedef volatile intptr_t MutexT ;      // Mux Lock-word
 enum MuxBits { LOCKBIT = 1 } ;
 void Thread::muxAcquire (volatile intptr_t * Lock, const char * LockName) {
   intptr_t w = Atomic::cmpxchg_ptr (LOCKBIT, Lock, 0) ;
   if (w == 0) return ;
   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
      return ;
   }
   TEVENT (muxAcquire - Contention) ;
   ParkEvent * const Self = Thread::current()->_MuxEvent ;
   assert ((intptr_t(Self) & LOCKBIT) == 0, "invariant") ;
   for (;;) {
      int its = (os::is_MP() ? 100 : 0) + 1 ;
      // Optional spin phase: spin-then-park strategy
      while (--its >= 0) {
        w = *Lock ;
        if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
           return ;
        }
      }
      Self->reset() ;
      Self->OnList = intptr_t(Lock) ;
      // The following fence() isn't _strictly necessary as the subsequent
      // CAS() both serializes execution and ratifies the fetched *Lock value.
      OrderAccess::fence();
      for (;;) {
         w = *Lock ;
         if ((w & LOCKBIT) == 0) {
             if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
                 Self->OnList = 0 ;   // hygiene - allows stronger asserts
                 return ;
             }
             continue ;      // Interference -- *Lock changed -- Just retry
         }
         assert (w & LOCKBIT, "invariant") ;
         Self->ListNext = (ParkEvent *) (w & ~LOCKBIT );
         if (Atomic::cmpxchg_ptr (intptr_t(Self)|LOCKBIT, Lock, w) == w) break ;
      }
      while (Self->OnList != 0) {
         Self->park() ;
      }
   }
 }
 void Thread::muxAcquireW (volatile intptr_t * Lock, ParkEvent * ev) {
   intptr_t w = Atomic::cmpxchg_ptr (LOCKBIT, Lock, 0) ;
   if (w == 0) return ;
   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
     return ;
   }
   TEVENT (muxAcquire - Contention) ;
   ParkEvent * ReleaseAfter = NULL ;
   if (ev == NULL) {
     ev = ReleaseAfter = ParkEvent::Allocate (NULL) ;
   }
   assert ((intptr_t(ev) & LOCKBIT) == 0, "invariant") ;
   for (;;) {
     guarantee (ev->OnList == 0, "invariant") ;
     int its = (os::is_MP() ? 100 : 0) + 1 ;
     // Optional spin phase: spin-then-park strategy
     while (--its >= 0) {
       w = *Lock ;
       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
         if (ReleaseAfter != NULL) {
           ParkEvent::Release (ReleaseAfter) ;
         }
         return ;
       }
     }
     ev->reset() ;
     ev->OnList = intptr_t(Lock) ;
     // The following fence() isn't _strictly necessary as the subsequent
     // CAS() both serializes execution and ratifies the fetched *Lock value.
     OrderAccess::fence();
     for (;;) {
       w = *Lock ;
       if ((w & LOCKBIT) == 0) {
         if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
           ev->OnList = 0 ;
           // We call ::Release while holding the outer lock, thus
           // artificially lengthening the critical section.
           // Consider deferring the ::Release() until the subsequent unlock(),
           // after we've dropped the outer lock.
           if (ReleaseAfter != NULL) {
             ParkEvent::Release (ReleaseAfter) ;
           }
           return ;
         }
         continue ;      // Interference -- *Lock changed -- Just retry
       }
       assert (w & LOCKBIT, "invariant") ;
       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT );
       if (Atomic::cmpxchg_ptr (intptr_t(ev)|LOCKBIT, Lock, w) == w) break ;
     }
     while (ev->OnList != 0) {
       ev->park() ;
     }
   }
 }
 // Release() must extract a successor from the list and then wake that thread.
 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
 // Release() would :
 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
 // (B) Extract a successor from the private list "in-hand"
 // (C) attempt to CAS() the residual back into *Lock over null.
 //     If there were any newly arrived threads and the CAS() would fail.
 //     In that case Release() would detach the RATs, re-merge the list in-hand
 //     with the RATs and repeat as needed.  Alternately, Release() might
 //     detach and extract a successor, but then pass the residual list to the wakee.
 //     The wakee would be responsible for reattaching and remerging before it
 //     competed for the lock.
 //
 // Both "pop" and DMR are immune from ABA corruption -- there can be
 // multiple concurrent pushers, but only one popper or detacher.
 // This implementation pops from the head of the list.  This is unfair,
 // but tends to provide excellent throughput as hot threads remain hot.
 // (We wake recently run threads first).
 void Thread::muxRelease (volatile intptr_t * Lock)  {
   for (;;) {
     const intptr_t w = Atomic::cmpxchg_ptr (0, Lock, LOCKBIT) ;
     assert (w & LOCKBIT, "invariant") ;
     if (w == LOCKBIT) return ;
     ParkEvent * List = (ParkEvent *) (w & ~LOCKBIT) ;
     assert (List != NULL, "invariant") ;
     assert (List->OnList == intptr_t(Lock), "invariant") ;
     ParkEvent * nxt = List->ListNext ;
     // The following CAS() releases the lock and pops the head element.
     if (Atomic::cmpxchg_ptr (intptr_t(nxt), Lock, w) != w) {
       continue ;
     }
     List->OnList = 0 ;
     OrderAccess::fence() ;
     List->unpark () ;
     return ;
   }
 }
 void Threads::verify() {
   ALL_JAVA_THREADS(p) {
     p->verify();
   }
   VMThread* thread = VMThread::vm_thread();
   if (thread != NULL) thread->verify();
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/runtime/thread.cpp@dd05dac9563a (annotated)

src/share/vm/runtime/thread.cpp