runtime/thread-inl.h - platform/art - Git at Google

 /*
  * Copyright (C) 2011 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #ifndef ART_RUNTIME_THREAD_INL_H_
 #define ART_RUNTIME_THREAD_INL_H_

 #include "thread.h"

 #include "arch/instruction_set.h"
 #include "base/aborting.h"
 #include "base/casts.h"
 #include "base/mutex-inl.h"
 #include "base/time_utils.h"
 #include "jni/jni_env_ext.h"
 #include "managed_stack-inl.h"
 #include "obj_ptr.h"
 #include "suspend_reason.h"
 #include "thread-current-inl.h"
 #include "thread_pool.h"

 namespace art {

 // Quickly access the current thread from a JNIEnv.
 static inline Thread* ThreadForEnv(JNIEnv* env) {
   JNIEnvExt* full_env(down_cast<JNIEnvExt*>(env));
   return full_env->GetSelf();
 }

 inline void Thread::AllowThreadSuspension() {
   CheckSuspend();
   // Invalidate the current thread's object pointers (ObjPtr) to catch possible moving GC bugs due
   // to missing handles.
   PoisonObjectPointers();
 }

 inline void Thread::CheckSuspend(bool implicit) {
   DCHECK_EQ(Thread::Current(), this);
   while (true) {
     StateAndFlags state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
     if (LIKELY(!state_and_flags.IsAnyOfFlagsSet(SuspendOrCheckpointRequestFlags()))) {
       break;
     } else if (state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest)) {
       RunCheckpointFunction();
     } else if (state_and_flags.IsFlagSet(ThreadFlag::kSuspendRequest)) {
       FullSuspendCheck(implicit);
       implicit = false;  // We do not need to `MadviseAwayAlternateSignalStack()` anymore.
     } else {
       DCHECK(state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest));
       RunEmptyCheckpoint();
     }
   }
   if (implicit) {
     // For implicit suspend check we want to `madvise()` away
     // the alternate signal stack to avoid wasting memory.
     MadviseAwayAlternateSignalStack();
   }
 }

 inline void Thread::CheckEmptyCheckpointFromWeakRefAccess(BaseMutex* cond_var_mutex) {
   Thread* self = Thread::Current();
   DCHECK_EQ(self, this);
   for (;;) {
     if (ReadFlag(ThreadFlag::kEmptyCheckpointRequest)) {
       RunEmptyCheckpoint();
       // Check we hold only an expected mutex when accessing weak ref.
       if (kIsDebugBuild) {
         for (int i = kLockLevelCount - 1; i >= 0; --i) {
           BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
           if (held_mutex != nullptr &&
               held_mutex != GetMutatorLock() &&
               held_mutex != cond_var_mutex) {
             CHECK(Locks::IsExpectedOnWeakRefAccess(held_mutex))
                 << "Holding unexpected mutex " << held_mutex->GetName()
                 << " when accessing weak ref";
           }
         }
       }
     } else {
       break;
     }
   }
 }

 inline void Thread::CheckEmptyCheckpointFromMutex() {
   DCHECK_EQ(Thread::Current(), this);
   for (;;) {
     if (ReadFlag(ThreadFlag::kEmptyCheckpointRequest)) {
       RunEmptyCheckpoint();
     } else {
       break;
     }
   }
 }

 inline ThreadState Thread::SetState(ThreadState new_state) {
   // Should only be used to change between suspended states.
   // Cannot use this code to change into or from Runnable as changing to Runnable should
   // fail if the `ThreadFlag::kSuspendRequest` is set and changing from Runnable might
   // miss passing an active suspend barrier.
   DCHECK_NE(new_state, ThreadState::kRunnable);
   if (kIsDebugBuild && this != Thread::Current()) {
     std::string name;
     GetThreadName(name);
     LOG(FATAL) << "Thread \"" << name << "\"(" << this << " != Thread::Current()="
                << Thread::Current() << ") changing state to " << new_state;
   }

   while (true) {
     StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
     CHECK_NE(old_state_and_flags.GetState(), ThreadState::kRunnable)
         << new_state << " " << *this << " " << *Thread::Current();
     StateAndFlags new_state_and_flags = old_state_and_flags.WithState(new_state);
     bool done =
         tls32_.state_and_flags.CompareAndSetWeakRelaxed(old_state_and_flags.GetValue(),
                                                         new_state_and_flags.GetValue());
     if (done) {
       return static_cast<ThreadState>(old_state_and_flags.GetState());
     }
   }
 }

 inline bool Thread::IsThreadSuspensionAllowable() const {
   if (tls32_.no_thread_suspension != 0) {
     return false;
   }
   for (int i = kLockLevelCount - 1; i >= 0; --i) {
     if (i != kMutatorLock &&
         i != kUserCodeSuspensionLock &&
         GetHeldMutex(static_cast<LockLevel>(i)) != nullptr) {
       return false;
     }
   }
   // Thread autoanalysis isn't able to understand that the GetHeldMutex(...) or AssertHeld means we
   // have the mutex meaning we need to do this hack.
   auto is_suspending_for_user_code = [this]() NO_THREAD_SAFETY_ANALYSIS {
     return tls32_.user_code_suspend_count != 0;
   };
   if (GetHeldMutex(kUserCodeSuspensionLock) != nullptr && is_suspending_for_user_code()) {
     return false;
   }
   return true;
 }

 inline void Thread::AssertThreadSuspensionIsAllowable(bool check_locks) const {
   if (kIsDebugBuild) {
     if (gAborting == 0) {
       CHECK_EQ(0u, tls32_.no_thread_suspension) << tlsPtr_.last_no_thread_suspension_cause;
     }
     if (check_locks) {
       bool bad_mutexes_held = false;
       for (int i = kLockLevelCount - 1; i >= 0; --i) {
         // We expect no locks except the mutator lock. User code suspension lock is OK as long as
         // we aren't going to be held suspended due to SuspendReason::kForUserCode.
         if (i != kMutatorLock && i != kUserCodeSuspensionLock) {
           BaseMutex* held_mutex = GetHeldMutex(static_cast<LockLevel>(i));
           if (held_mutex != nullptr) {
             LOG(ERROR) << "holding \"" << held_mutex->GetName()
                       << "\" at point where thread suspension is expected";
             bad_mutexes_held = true;
           }
         }
       }
       // Make sure that if we hold the user_code_suspension_lock_ we aren't suspending due to
       // user_code_suspend_count which would prevent the thread from ever waking up.  Thread
       // autoanalysis isn't able to understand that the GetHeldMutex(...) or AssertHeld means we
       // have the mutex meaning we need to do this hack.
       auto is_suspending_for_user_code = [this]() NO_THREAD_SAFETY_ANALYSIS {
         return tls32_.user_code_suspend_count != 0;
       };
       if (GetHeldMutex(kUserCodeSuspensionLock) != nullptr && is_suspending_for_user_code()) {
         LOG(ERROR) << "suspending due to user-code while holding \""
                    << Locks::user_code_suspension_lock_->GetName() << "\"! Thread would never "
                    << "wake up.";
         bad_mutexes_held = true;
       }
       if (gAborting == 0) {
         CHECK(!bad_mutexes_held);
       }
     }
   }
 }

 inline void Thread::TransitionToSuspendedAndRunCheckpoints(ThreadState new_state) {
   DCHECK_NE(new_state, ThreadState::kRunnable);
   while (true) {
     StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
     DCHECK_EQ(old_state_and_flags.GetState(), ThreadState::kRunnable);
     if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest))) {
       RunCheckpointFunction();
       continue;
     }
     if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest))) {
       RunEmptyCheckpoint();
       continue;
     }
     // Change the state but keep the current flags (kCheckpointRequest is clear).
     DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest));
     DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest));
     StateAndFlags new_state_and_flags = old_state_and_flags.WithState(new_state);

     // CAS the value, ensuring that prior memory operations are visible to any thread
     // that observes that we are suspended.
     bool done =
         tls32_.state_and_flags.CompareAndSetWeakRelease(old_state_and_flags.GetValue(),
                                                         new_state_and_flags.GetValue());
     if (LIKELY(done)) {
       break;
     }
   }
 }

 inline void Thread::PassActiveSuspendBarriers() {
   while (true) {
     StateAndFlags state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
     if (LIKELY(!state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest) &&
                !state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest) &&
                !state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier))) {
       break;
     } else if (state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier)) {
       PassActiveSuspendBarriers(this);
     } else {
       // Impossible
       LOG(FATAL) << "Fatal, thread transitioned into suspended without running the checkpoint";
     }
   }
 }

 inline void Thread::TransitionFromRunnableToSuspended(ThreadState new_state) {
   // Note: JNI stubs inline a fast path of this method that transitions to suspended if
   // there are no flags set and then clears the `held_mutexes[kMutatorLock]` (this comes
   // from a specialized `BaseMutex::RegisterAsLockedImpl(., kMutatorLock)` inlined from
   // the `GetMutatorLock()->TransitionFromRunnableToSuspended(this)` below).
   // Therefore any code added here (other than debug build assertions) should be gated
   // on some flag being set, so that the JNI stub can take the slow path to get here.
   AssertThreadSuspensionIsAllowable();
   PoisonObjectPointersIfDebug();
   DCHECK_EQ(this, Thread::Current());
   // Change to non-runnable state, thereby appearing suspended to the system.
   TransitionToSuspendedAndRunCheckpoints(new_state);
   // Mark the release of the share of the mutator lock.
   GetMutatorLock()->TransitionFromRunnableToSuspended(this);
   // Once suspended - check the active suspend barrier flag
   PassActiveSuspendBarriers();
 }

 inline ThreadState Thread::TransitionFromSuspendedToRunnable() {
   // Note: JNI stubs inline a fast path of this method that transitions to Runnable if
   // there are no flags set and then stores the mutator lock to `held_mutexes[kMutatorLock]`
   // (this comes from a specialized `BaseMutex::RegisterAsUnlockedImpl(., kMutatorLock)`
   // inlined from the `GetMutatorLock()->TransitionFromSuspendedToRunnable(this)` below).
   // Therefore any code added here (other than debug build assertions) should be gated
   // on some flag being set, so that the JNI stub can take the slow path to get here.
   StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
   ThreadState old_state = old_state_and_flags.GetState();
   DCHECK_NE(old_state, ThreadState::kRunnable);
   while (true) {
     GetMutatorLock()->AssertNotHeld(this);  // Otherwise we starve GC.
     // Optimize for the return from native code case - this is the fast path.
     // Atomically change from suspended to runnable if no suspend request pending.
     constexpr uint32_t kCheckedFlags =
         SuspendOrCheckpointRequestFlags() |
         enum_cast<uint32_t>(ThreadFlag::kActiveSuspendBarrier) |
         FlipFunctionFlags();
     if (LIKELY(!old_state_and_flags.IsAnyOfFlagsSet(kCheckedFlags))) {
       // CAS the value with a memory barrier.
       StateAndFlags new_state_and_flags = old_state_and_flags.WithState(ThreadState::kRunnable);
       if (LIKELY(tls32_.state_and_flags.CompareAndSetWeakAcquire(old_state_and_flags.GetValue(),
                                                                  new_state_and_flags.GetValue()))) {
         // Mark the acquisition of a share of the mutator lock.
         GetMutatorLock()->TransitionFromSuspendedToRunnable(this);
         break;
       }
     } else if (old_state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier)) {
       PassActiveSuspendBarriers(this);
     } else if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest) ||
                         old_state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest))) {
       // Checkpoint flags should not be set while in suspended state.
       static_assert(static_cast<std::underlying_type_t<ThreadState>>(ThreadState::kRunnable) == 0u);
       LOG(FATAL) << "Transitioning to Runnable with checkpoint flag,"
                  // Note: Keeping unused flags. If they are set, it points to memory corruption.
                  << " flags=" << old_state_and_flags.WithState(ThreadState::kRunnable).GetValue()
                  << " state=" << old_state_and_flags.GetState();
     } else if (old_state_and_flags.IsFlagSet(ThreadFlag::kSuspendRequest)) {
       // Wait while our suspend count is non-zero.

       // We pass null to the MutexLock as we may be in a situation where the
       // runtime is shutting down. Guarding ourselves from that situation
       // requires to take the shutdown lock, which is undesirable here.
       Thread* thread_to_pass = nullptr;
       if (kIsDebugBuild && !IsDaemon()) {
         // We know we can make our debug locking checks on non-daemon threads,
         // so re-enable them on debug builds.
         thread_to_pass = this;
       }
       MutexLock mu(thread_to_pass, *Locks::thread_suspend_count_lock_);
       ScopedTransitioningToRunnable scoped_transitioning_to_runnable(this);
       // Reload state and flags after locking the mutex.
       old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
       DCHECK_EQ(old_state, old_state_and_flags.GetState());
       while (old_state_and_flags.IsFlagSet(ThreadFlag::kSuspendRequest)) {
         // Re-check when Thread::resume_cond_ is notified.
         Thread::resume_cond_->Wait(thread_to_pass);
         // Reload state and flags after waiting.
         old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
         DCHECK_EQ(old_state, old_state_and_flags.GetState());
       }
       DCHECK_EQ(GetSuspendCount(), 0);
     } else if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction)) ||
                UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kWaitingForFlipFunction))) {
       // The thread should be suspended while another thread is running the flip function.
       static_assert(static_cast<std::underlying_type_t<ThreadState>>(ThreadState::kRunnable) == 0u);
       LOG(FATAL) << "Transitioning to Runnable while another thread is running the flip function,"
                  // Note: Keeping unused flags. If they are set, it points to memory corruption.
                  << " flags=" << old_state_and_flags.WithState(ThreadState::kRunnable).GetValue()
                  << " state=" << old_state_and_flags.GetState();
     } else {
       DCHECK(old_state_and_flags.IsFlagSet(ThreadFlag::kPendingFlipFunction));
       // CAS the value with a memory barrier.
       // Do not set `ThreadFlag::kRunningFlipFunction` as no other thread can run
       // the flip function for a thread that is not suspended.
       StateAndFlags new_state_and_flags = old_state_and_flags.WithState(ThreadState::kRunnable)
           .WithoutFlag(ThreadFlag::kPendingFlipFunction);
       if (LIKELY(tls32_.state_and_flags.CompareAndSetWeakAcquire(old_state_and_flags.GetValue(),
                                                                  new_state_and_flags.GetValue()))) {
         // Mark the acquisition of a share of the mutator lock.
         GetMutatorLock()->TransitionFromSuspendedToRunnable(this);
         // Run the flip function.
         RunFlipFunction(this, /*notify=*/ false);
         break;
       }
     }
     // Reload state and flags.
     old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
     DCHECK_EQ(old_state, old_state_and_flags.GetState());
   }
   return static_cast<ThreadState>(old_state);
 }

 inline mirror::Object* Thread::AllocTlab(size_t bytes) {
   DCHECK_GE(TlabSize(), bytes);
   ++tlsPtr_.thread_local_objects;
   mirror::Object* ret = reinterpret_cast<mirror::Object*>(tlsPtr_.thread_local_pos);
   tlsPtr_.thread_local_pos += bytes;
   return ret;
 }

 inline bool Thread::PushOnThreadLocalAllocationStack(mirror::Object* obj) {
   DCHECK_LE(tlsPtr_.thread_local_alloc_stack_top, tlsPtr_.thread_local_alloc_stack_end);
   if (tlsPtr_.thread_local_alloc_stack_top < tlsPtr_.thread_local_alloc_stack_end) {
     // There's room.
     DCHECK_LE(reinterpret_cast<uint8_t*>(tlsPtr_.thread_local_alloc_stack_top) +
               sizeof(StackReference<mirror::Object>),
               reinterpret_cast<uint8_t*>(tlsPtr_.thread_local_alloc_stack_end));
     DCHECK(tlsPtr_.thread_local_alloc_stack_top->AsMirrorPtr() == nullptr);
     tlsPtr_.thread_local_alloc_stack_top->Assign(obj);
     ++tlsPtr_.thread_local_alloc_stack_top;
     return true;
   }
   return false;
 }

 inline bool Thread::GetWeakRefAccessEnabled() const {
   CHECK(kUseReadBarrier);
   DCHECK(this == Thread::Current());
   WeakRefAccessState s = tls32_.weak_ref_access_enabled.load(std::memory_order_acquire);
   if (s == WeakRefAccessState::kVisiblyEnabled) {
     return true;
   } else if (s == WeakRefAccessState::kDisabled) {
     return false;
   }
   DCHECK(s == WeakRefAccessState::kEnabled)
       << "state = " << static_cast<std::underlying_type_t<WeakRefAccessState>>(s);
   // The state is only changed back to DISABLED during a checkpoint. Thus no other thread can
   // change the value concurrently here. No other thread reads the value we store here, so there
   // is no need for a release store.
   tls32_.weak_ref_access_enabled.store(WeakRefAccessState::kVisiblyEnabled,
                                        std::memory_order_relaxed);
   return true;
 }

 inline void Thread::SetThreadLocalAllocationStack(StackReference<mirror::Object>* start,
                                                   StackReference<mirror::Object>* end) {
   DCHECK(Thread::Current() == this) << "Should be called by self";
   DCHECK(start != nullptr);
   DCHECK(end != nullptr);
   DCHECK_ALIGNED(start, sizeof(StackReference<mirror::Object>));
   DCHECK_ALIGNED(end, sizeof(StackReference<mirror::Object>));
   DCHECK_LT(start, end);
   tlsPtr_.thread_local_alloc_stack_end = end;
   tlsPtr_.thread_local_alloc_stack_top = start;
 }

 inline void Thread::RevokeThreadLocalAllocationStack() {
   if (kIsDebugBuild) {
     // Note: self is not necessarily equal to this thread since thread may be suspended.
     Thread* self = Thread::Current();
     DCHECK(this == self || IsSuspended() || GetState() == ThreadState::kWaitingPerformingGc)
         << GetState() << " thread " << this << " self " << self;
   }
   tlsPtr_.thread_local_alloc_stack_end = nullptr;
   tlsPtr_.thread_local_alloc_stack_top = nullptr;
 }

 inline void Thread::PoisonObjectPointersIfDebug() {
   if (kObjPtrPoisoning) {
     Thread::Current()->PoisonObjectPointers();
   }
 }

 inline bool Thread::ModifySuspendCount(Thread* self,
                                        int delta,
                                        AtomicInteger* suspend_barrier,
                                        SuspendReason reason) {
   if (delta > 0 && ((kUseReadBarrier && this != self) || suspend_barrier != nullptr)) {
     // When delta > 0 (requesting a suspend), ModifySuspendCountInternal() may fail either if
     // active_suspend_barriers is full or we are in the middle of a thread flip. Retry in a loop.
     while (true) {
       if (LIKELY(ModifySuspendCountInternal(self, delta, suspend_barrier, reason))) {
         return true;
       } else {
         // Failure means the list of active_suspend_barriers is full or we are in the middle of a
         // thread flip, we should release the thread_suspend_count_lock_ (to avoid deadlock) and
         // wait till the target thread has executed or Thread::PassActiveSuspendBarriers() or the
         // flip function. Note that we could not simply wait for the thread to change to a suspended
         // state, because it might need to run checkpoint function before the state change or
         // resumes from the resume_cond_, which also needs thread_suspend_count_lock_.
         //
         // The list of active_suspend_barriers is very unlikely to be full since more than
         // kMaxSuspendBarriers threads need to execute SuspendAllInternal() simultaneously, and
         // target thread stays in kRunnable in the mean time.
         Locks::thread_suspend_count_lock_->ExclusiveUnlock(self);
         NanoSleep(100000);
         Locks::thread_suspend_count_lock_->ExclusiveLock(self);
       }
     }
   } else {
     return ModifySuspendCountInternal(self, delta, suspend_barrier, reason);
   }
 }

 inline ShadowFrame* Thread::PushShadowFrame(ShadowFrame* new_top_frame) {
   new_top_frame->CheckConsistentVRegs();
   return tlsPtr_.managed_stack.PushShadowFrame(new_top_frame);
 }

 inline ShadowFrame* Thread::PopShadowFrame() {
   return tlsPtr_.managed_stack.PopShadowFrame();
 }

 inline uint8_t* Thread::GetStackEndForInterpreter(bool implicit_overflow_check) const {
   uint8_t* end = tlsPtr_.stack_end + (implicit_overflow_check
       ? GetStackOverflowReservedBytes(kRuntimeISA)
           : 0);
   if (kIsDebugBuild) {
     // In a debuggable build, but especially under ASAN, the access-checks interpreter has a
     // potentially humongous stack size. We don't want to take too much of the stack regularly,
     // so do not increase the regular reserved size (for compiled code etc) and only report the
     // virtually smaller stack to the interpreter here.
     end += GetStackOverflowReservedBytes(kRuntimeISA);
   }
   return end;
 }

 inline void Thread::ResetDefaultStackEnd() {
   // Our stacks grow down, so we want stack_end_ to be near there, but reserving enough room
   // to throw a StackOverflowError.
   tlsPtr_.stack_end = tlsPtr_.stack_begin + GetStackOverflowReservedBytes(kRuntimeISA);
 }

 }  // namespace art

 #endif  // ART_RUNTIME_THREAD_INL_H_
	/*
	* Copyright (C) 2011 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#ifndef ART_RUNTIME_THREAD_INL_H_
	#define ART_RUNTIME_THREAD_INL_H_

	#include "thread.h"

	#include "arch/instruction_set.h"
	#include "base/aborting.h"
	#include "base/casts.h"
	#include "base/mutex-inl.h"
	#include "base/time_utils.h"
	#include "jni/jni_env_ext.h"
	#include "managed_stack-inl.h"
	#include "obj_ptr.h"
	#include "suspend_reason.h"
	#include "thread-current-inl.h"
	#include "thread_pool.h"

	namespace art {

	// Quickly access the current thread from a JNIEnv.
	static inline Thread* ThreadForEnv(JNIEnv* env) {
	JNIEnvExt* full_env(down_cast<JNIEnvExt*>(env));
	return full_env->GetSelf();
	}

	inline void Thread::AllowThreadSuspension() {
	CheckSuspend();
	// Invalidate the current thread's object pointers (ObjPtr) to catch possible moving GC bugs due
	// to missing handles.
	PoisonObjectPointers();
	}

	inline void Thread::CheckSuspend(bool implicit) {
	DCHECK_EQ(Thread::Current(), this);
	while (true) {
	StateAndFlags state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
	if (LIKELY(!state_and_flags.IsAnyOfFlagsSet(SuspendOrCheckpointRequestFlags()))) {
	break;
	} else if (state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest)) {
	RunCheckpointFunction();
	} else if (state_and_flags.IsFlagSet(ThreadFlag::kSuspendRequest)) {
	FullSuspendCheck(implicit);
	implicit = false; // We do not need to `MadviseAwayAlternateSignalStack()` anymore.
	} else {
	DCHECK(state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest));
	RunEmptyCheckpoint();
	}
	}
	if (implicit) {
	// For implicit suspend check we want to `madvise()` away
	// the alternate signal stack to avoid wasting memory.
	MadviseAwayAlternateSignalStack();
	}
	}

	inline void Thread::CheckEmptyCheckpointFromWeakRefAccess(BaseMutex* cond_var_mutex) {
	Thread* self = Thread::Current();
	DCHECK_EQ(self, this);
	for (;;) {
	if (ReadFlag(ThreadFlag::kEmptyCheckpointRequest)) {
	RunEmptyCheckpoint();
	// Check we hold only an expected mutex when accessing weak ref.
	if (kIsDebugBuild) {
	for (int i = kLockLevelCount - 1; i >= 0; --i) {
	BaseMutex* held_mutex = self->GetHeldMutex(static_cast<LockLevel>(i));
	if (held_mutex != nullptr &&
	held_mutex != GetMutatorLock() &&
	held_mutex != cond_var_mutex) {
	CHECK(Locks::IsExpectedOnWeakRefAccess(held_mutex))
	<< "Holding unexpected mutex " << held_mutex->GetName()
	<< " when accessing weak ref";
	}
	}
	}
	} else {
	break;
	}
	}
	}

	inline void Thread::CheckEmptyCheckpointFromMutex() {
	DCHECK_EQ(Thread::Current(), this);
	for (;;) {
	if (ReadFlag(ThreadFlag::kEmptyCheckpointRequest)) {
	RunEmptyCheckpoint();
	} else {
	break;
	}
	}
	}

	inline ThreadState Thread::SetState(ThreadState new_state) {
	// Should only be used to change between suspended states.
	// Cannot use this code to change into or from Runnable as changing to Runnable should
	// fail if the `ThreadFlag::kSuspendRequest` is set and changing from Runnable might
	// miss passing an active suspend barrier.
	DCHECK_NE(new_state, ThreadState::kRunnable);
	if (kIsDebugBuild && this != Thread::Current()) {
	std::string name;
	GetThreadName(name);
	LOG(FATAL) << "Thread \"" << name << "\"(" << this << " != Thread::Current()="
	<< Thread::Current() << ") changing state to " << new_state;
	}

	while (true) {
	StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
	CHECK_NE(old_state_and_flags.GetState(), ThreadState::kRunnable)
	<< new_state << " " << this << " " << Thread::Current();
	StateAndFlags new_state_and_flags = old_state_and_flags.WithState(new_state);
	bool done =
	tls32_.state_and_flags.CompareAndSetWeakRelaxed(old_state_and_flags.GetValue(),
	new_state_and_flags.GetValue());
	if (done) {
	return static_cast<ThreadState>(old_state_and_flags.GetState());
	}
	}
	}

	inline bool Thread::IsThreadSuspensionAllowable() const {
	if (tls32_.no_thread_suspension != 0) {
	return false;
	}
	for (int i = kLockLevelCount - 1; i >= 0; --i) {
	if (i != kMutatorLock &&
	i != kUserCodeSuspensionLock &&
	GetHeldMutex(static_cast<LockLevel>(i)) != nullptr) {
	return false;
	}
	}
	// Thread autoanalysis isn't able to understand that the GetHeldMutex(...) or AssertHeld means we
	// have the mutex meaning we need to do this hack.
	auto is_suspending_for_user_code = [this]() NO_THREAD_SAFETY_ANALYSIS {
	return tls32_.user_code_suspend_count != 0;
	};
	if (GetHeldMutex(kUserCodeSuspensionLock) != nullptr && is_suspending_for_user_code()) {
	return false;
	}
	return true;
	}

	inline void Thread::AssertThreadSuspensionIsAllowable(bool check_locks) const {
	if (kIsDebugBuild) {
	if (gAborting == 0) {
	CHECK_EQ(0u, tls32_.no_thread_suspension) << tlsPtr_.last_no_thread_suspension_cause;
	}
	if (check_locks) {
	bool bad_mutexes_held = false;
	for (int i = kLockLevelCount - 1; i >= 0; --i) {
	// We expect no locks except the mutator lock. User code suspension lock is OK as long as
	// we aren't going to be held suspended due to SuspendReason::kForUserCode.
	if (i != kMutatorLock && i != kUserCodeSuspensionLock) {
	BaseMutex* held_mutex = GetHeldMutex(static_cast<LockLevel>(i));
	if (held_mutex != nullptr) {
	LOG(ERROR) << "holding \"" << held_mutex->GetName()
	<< "\" at point where thread suspension is expected";
	bad_mutexes_held = true;
	}
	}
	}
	// Make sure that if we hold the user_code_suspension_lock_ we aren't suspending due to
	// user_code_suspend_count which would prevent the thread from ever waking up. Thread
	// autoanalysis isn't able to understand that the GetHeldMutex(...) or AssertHeld means we
	// have the mutex meaning we need to do this hack.
	auto is_suspending_for_user_code = [this]() NO_THREAD_SAFETY_ANALYSIS {
	return tls32_.user_code_suspend_count != 0;
	};
	if (GetHeldMutex(kUserCodeSuspensionLock) != nullptr && is_suspending_for_user_code()) {
	LOG(ERROR) << "suspending due to user-code while holding \""
	<< Locks::user_code_suspension_lock_->GetName() << "\"! Thread would never "
	<< "wake up.";
	bad_mutexes_held = true;
	}
	if (gAborting == 0) {
	CHECK(!bad_mutexes_held);
	}
	}
	}
	}

	inline void Thread::TransitionToSuspendedAndRunCheckpoints(ThreadState new_state) {
	DCHECK_NE(new_state, ThreadState::kRunnable);
	while (true) {
	StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
	DCHECK_EQ(old_state_and_flags.GetState(), ThreadState::kRunnable);
	if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest))) {
	RunCheckpointFunction();
	continue;
	}
	if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest))) {
	RunEmptyCheckpoint();
	continue;
	}
	// Change the state but keep the current flags (kCheckpointRequest is clear).
	DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest));
	DCHECK(!old_state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest));
	StateAndFlags new_state_and_flags = old_state_and_flags.WithState(new_state);

	// CAS the value, ensuring that prior memory operations are visible to any thread
	// that observes that we are suspended.
	bool done =
	tls32_.state_and_flags.CompareAndSetWeakRelease(old_state_and_flags.GetValue(),
	new_state_and_flags.GetValue());
	if (LIKELY(done)) {
	break;
	}
	}
	}

	inline void Thread::PassActiveSuspendBarriers() {
	while (true) {
	StateAndFlags state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
	if (LIKELY(!state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest) &&
	!state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest) &&
	!state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier))) {
	break;
	} else if (state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier)) {
	PassActiveSuspendBarriers(this);
	} else {
	// Impossible
	LOG(FATAL) << "Fatal, thread transitioned into suspended without running the checkpoint";
	}
	}
	}

	inline void Thread::TransitionFromRunnableToSuspended(ThreadState new_state) {
	// Note: JNI stubs inline a fast path of this method that transitions to suspended if
	// there are no flags set and then clears the `held_mutexes[kMutatorLock]` (this comes
	// from a specialized `BaseMutex::RegisterAsLockedImpl(., kMutatorLock)` inlined from
	// the `GetMutatorLock()->TransitionFromRunnableToSuspended(this)` below).
	// Therefore any code added here (other than debug build assertions) should be gated
	// on some flag being set, so that the JNI stub can take the slow path to get here.
	AssertThreadSuspensionIsAllowable();
	PoisonObjectPointersIfDebug();
	DCHECK_EQ(this, Thread::Current());
	// Change to non-runnable state, thereby appearing suspended to the system.
	TransitionToSuspendedAndRunCheckpoints(new_state);
	// Mark the release of the share of the mutator lock.
	GetMutatorLock()->TransitionFromRunnableToSuspended(this);
	// Once suspended - check the active suspend barrier flag
	PassActiveSuspendBarriers();
	}

	inline ThreadState Thread::TransitionFromSuspendedToRunnable() {
	// Note: JNI stubs inline a fast path of this method that transitions to Runnable if
	// there are no flags set and then stores the mutator lock to `held_mutexes[kMutatorLock]`
	// (this comes from a specialized `BaseMutex::RegisterAsUnlockedImpl(., kMutatorLock)`
	// inlined from the `GetMutatorLock()->TransitionFromSuspendedToRunnable(this)` below).
	// Therefore any code added here (other than debug build assertions) should be gated
	// on some flag being set, so that the JNI stub can take the slow path to get here.
	StateAndFlags old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
	ThreadState old_state = old_state_and_flags.GetState();
	DCHECK_NE(old_state, ThreadState::kRunnable);
	while (true) {
	GetMutatorLock()->AssertNotHeld(this); // Otherwise we starve GC.
	// Optimize for the return from native code case - this is the fast path.
	// Atomically change from suspended to runnable if no suspend request pending.
	constexpr uint32_t kCheckedFlags =
	SuspendOrCheckpointRequestFlags() \|
	enum_cast<uint32_t>(ThreadFlag::kActiveSuspendBarrier) \|
	FlipFunctionFlags();
	if (LIKELY(!old_state_and_flags.IsAnyOfFlagsSet(kCheckedFlags))) {
	// CAS the value with a memory barrier.
	StateAndFlags new_state_and_flags = old_state_and_flags.WithState(ThreadState::kRunnable);
	if (LIKELY(tls32_.state_and_flags.CompareAndSetWeakAcquire(old_state_and_flags.GetValue(),
	new_state_and_flags.GetValue()))) {
	// Mark the acquisition of a share of the mutator lock.
	GetMutatorLock()->TransitionFromSuspendedToRunnable(this);
	break;
	}
	} else if (old_state_and_flags.IsFlagSet(ThreadFlag::kActiveSuspendBarrier)) {
	PassActiveSuspendBarriers(this);
	} else if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kCheckpointRequest) \|\|
	old_state_and_flags.IsFlagSet(ThreadFlag::kEmptyCheckpointRequest))) {
	// Checkpoint flags should not be set while in suspended state.
	static_assert(static_cast<std::underlying_type_t<ThreadState>>(ThreadState::kRunnable) == 0u);
	LOG(FATAL) << "Transitioning to Runnable with checkpoint flag,"
	// Note: Keeping unused flags. If they are set, it points to memory corruption.
	<< " flags=" << old_state_and_flags.WithState(ThreadState::kRunnable).GetValue()
	<< " state=" << old_state_and_flags.GetState();
	} else if (old_state_and_flags.IsFlagSet(ThreadFlag::kSuspendRequest)) {
	// Wait while our suspend count is non-zero.

	// We pass null to the MutexLock as we may be in a situation where the
	// runtime is shutting down. Guarding ourselves from that situation
	// requires to take the shutdown lock, which is undesirable here.
	Thread* thread_to_pass = nullptr;
	if (kIsDebugBuild && !IsDaemon()) {
	// We know we can make our debug locking checks on non-daemon threads,
	// so re-enable them on debug builds.
	thread_to_pass = this;
	}
	MutexLock mu(thread_to_pass, *Locks::thread_suspend_count_lock_);
	ScopedTransitioningToRunnable scoped_transitioning_to_runnable(this);
	// Reload state and flags after locking the mutex.
	old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
	DCHECK_EQ(old_state, old_state_and_flags.GetState());
	while (old_state_and_flags.IsFlagSet(ThreadFlag::kSuspendRequest)) {
	// Re-check when Thread::resume_cond_ is notified.
	Thread::resume_cond_->Wait(thread_to_pass);
	// Reload state and flags after waiting.
	old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
	DCHECK_EQ(old_state, old_state_and_flags.GetState());
	}
	DCHECK_EQ(GetSuspendCount(), 0);
	} else if (UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kRunningFlipFunction)) \|\|
	UNLIKELY(old_state_and_flags.IsFlagSet(ThreadFlag::kWaitingForFlipFunction))) {
	// The thread should be suspended while another thread is running the flip function.
	static_assert(static_cast<std::underlying_type_t<ThreadState>>(ThreadState::kRunnable) == 0u);
	LOG(FATAL) << "Transitioning to Runnable while another thread is running the flip function,"
	// Note: Keeping unused flags. If they are set, it points to memory corruption.
	<< " flags=" << old_state_and_flags.WithState(ThreadState::kRunnable).GetValue()
	<< " state=" << old_state_and_flags.GetState();
	} else {
	DCHECK(old_state_and_flags.IsFlagSet(ThreadFlag::kPendingFlipFunction));
	// CAS the value with a memory barrier.
	// Do not set `ThreadFlag::kRunningFlipFunction` as no other thread can run
	// the flip function for a thread that is not suspended.
	StateAndFlags new_state_and_flags = old_state_and_flags.WithState(ThreadState::kRunnable)
	.WithoutFlag(ThreadFlag::kPendingFlipFunction);
	if (LIKELY(tls32_.state_and_flags.CompareAndSetWeakAcquire(old_state_and_flags.GetValue(),
	new_state_and_flags.GetValue()))) {
	// Mark the acquisition of a share of the mutator lock.
	GetMutatorLock()->TransitionFromSuspendedToRunnable(this);
	// Run the flip function.
	RunFlipFunction(this, /notify=/ false);
	break;
	}
	}
	// Reload state and flags.
	old_state_and_flags = GetStateAndFlags(std::memory_order_relaxed);
	DCHECK_EQ(old_state, old_state_and_flags.GetState());
	}
	return static_cast<ThreadState>(old_state);
	}

	inline mirror::Object* Thread::AllocTlab(size_t bytes) {
	DCHECK_GE(TlabSize(), bytes);
	++tlsPtr_.thread_local_objects;
	mirror::Object* ret = reinterpret_cast<mirror::Object*>(tlsPtr_.thread_local_pos);
	tlsPtr_.thread_local_pos += bytes;
	return ret;
	}

	inline bool Thread::PushOnThreadLocalAllocationStack(mirror::Object* obj) {
	DCHECK_LE(tlsPtr_.thread_local_alloc_stack_top, tlsPtr_.thread_local_alloc_stack_end);
	if (tlsPtr_.thread_local_alloc_stack_top < tlsPtr_.thread_local_alloc_stack_end) {
	// There's room.
	DCHECK_LE(reinterpret_cast<uint8_t*>(tlsPtr_.thread_local_alloc_stack_top) +
	sizeof(StackReference<mirror::Object>),
	reinterpret_cast<uint8_t*>(tlsPtr_.thread_local_alloc_stack_end));
	DCHECK(tlsPtr_.thread_local_alloc_stack_top->AsMirrorPtr() == nullptr);
	tlsPtr_.thread_local_alloc_stack_top->Assign(obj);
	++tlsPtr_.thread_local_alloc_stack_top;
	return true;
	}
	return false;
	}

	inline bool Thread::GetWeakRefAccessEnabled() const {
	CHECK(kUseReadBarrier);
	DCHECK(this == Thread::Current());
	WeakRefAccessState s = tls32_.weak_ref_access_enabled.load(std::memory_order_acquire);
	if (s == WeakRefAccessState::kVisiblyEnabled) {
	return true;
	} else if (s == WeakRefAccessState::kDisabled) {
	return false;
	}
	DCHECK(s == WeakRefAccessState::kEnabled)
	<< "state = " << static_cast<std::underlying_type_t<WeakRefAccessState>>(s);
	// The state is only changed back to DISABLED during a checkpoint. Thus no other thread can
	// change the value concurrently here. No other thread reads the value we store here, so there
	// is no need for a release store.
	tls32_.weak_ref_access_enabled.store(WeakRefAccessState::kVisiblyEnabled,
	std::memory_order_relaxed);
	return true;
	}

	inline void Thread::SetThreadLocalAllocationStack(StackReference<mirror::Object>* start,
	StackReference<mirror::Object>* end) {
	DCHECK(Thread::Current() == this) << "Should be called by self";
	DCHECK(start != nullptr);
	DCHECK(end != nullptr);
	DCHECK_ALIGNED(start, sizeof(StackReference<mirror::Object>));
	DCHECK_ALIGNED(end, sizeof(StackReference<mirror::Object>));
	DCHECK_LT(start, end);
	tlsPtr_.thread_local_alloc_stack_end = end;
	tlsPtr_.thread_local_alloc_stack_top = start;
	}

	inline void Thread::RevokeThreadLocalAllocationStack() {
	if (kIsDebugBuild) {
	// Note: self is not necessarily equal to this thread since thread may be suspended.
	Thread* self = Thread::Current();
	DCHECK(this == self \|\| IsSuspended() \|\| GetState() == ThreadState::kWaitingPerformingGc)
	<< GetState() << " thread " << this << " self " << self;
	}
	tlsPtr_.thread_local_alloc_stack_end = nullptr;
	tlsPtr_.thread_local_alloc_stack_top = nullptr;
	}

	inline void Thread::PoisonObjectPointersIfDebug() {
	if (kObjPtrPoisoning) {
	Thread::Current()->PoisonObjectPointers();
	}
	}

	inline bool Thread::ModifySuspendCount(Thread* self,
	int delta,
	AtomicInteger* suspend_barrier,
	SuspendReason reason) {
	if (delta > 0 && ((kUseReadBarrier && this != self) \|\| suspend_barrier != nullptr)) {
	// When delta > 0 (requesting a suspend), ModifySuspendCountInternal() may fail either if
	// active_suspend_barriers is full or we are in the middle of a thread flip. Retry in a loop.
	while (true) {
	if (LIKELY(ModifySuspendCountInternal(self, delta, suspend_barrier, reason))) {
	return true;
	} else {
	// Failure means the list of active_suspend_barriers is full or we are in the middle of a
	// thread flip, we should release the thread_suspend_count_lock_ (to avoid deadlock) and
	// wait till the target thread has executed or Thread::PassActiveSuspendBarriers() or the
	// flip function. Note that we could not simply wait for the thread to change to a suspended
	// state, because it might need to run checkpoint function before the state change or
	// resumes from the resume_cond_, which also needs thread_suspend_count_lock_.
	//
	// The list of active_suspend_barriers is very unlikely to be full since more than
	// kMaxSuspendBarriers threads need to execute SuspendAllInternal() simultaneously, and
	// target thread stays in kRunnable in the mean time.
	Locks::thread_suspend_count_lock_->ExclusiveUnlock(self);
	NanoSleep(100000);
	Locks::thread_suspend_count_lock_->ExclusiveLock(self);
	}
	}
	} else {
	return ModifySuspendCountInternal(self, delta, suspend_barrier, reason);
	}
	}

	inline ShadowFrame* Thread::PushShadowFrame(ShadowFrame* new_top_frame) {
	new_top_frame->CheckConsistentVRegs();
	return tlsPtr_.managed_stack.PushShadowFrame(new_top_frame);
	}

	inline ShadowFrame* Thread::PopShadowFrame() {
	return tlsPtr_.managed_stack.PopShadowFrame();
	}

	inline uint8_t* Thread::GetStackEndForInterpreter(bool implicit_overflow_check) const {
	uint8_t* end = tlsPtr_.stack_end + (implicit_overflow_check
	? GetStackOverflowReservedBytes(kRuntimeISA)
	: 0);
	if (kIsDebugBuild) {
	// In a debuggable build, but especially under ASAN, the access-checks interpreter has a
	// potentially humongous stack size. We don't want to take too much of the stack regularly,
	// so do not increase the regular reserved size (for compiled code etc) and only report the
	// virtually smaller stack to the interpreter here.
	end += GetStackOverflowReservedBytes(kRuntimeISA);
	}
	return end;
	}

	inline void Thread::ResetDefaultStackEnd() {
	// Our stacks grow down, so we want stack_end_ to be near there, but reserving enough room
	// to throw a StackOverflowError.
	tlsPtr_.stack_end = tlsPtr_.stack_begin + GetStackOverflowReservedBytes(kRuntimeISA);
	}

	} // namespace art

	#endif // ART_RUNTIME_THREAD_INL_H_