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* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <pthread.h>
#include <bitset>
#include <iosfwd>
#include <list>
#include <string>
#include <vector>
#include "dex_file.h"
#include "globals.h"
#include "jni_internal.h"
#include "logging.h"
#include "macros.h"
#include "mutex.h"
#include "mem_map.h"
#include "oat/runtime/oat_support_entrypoints.h"
#include "offsets.h"
#include "runtime_stats.h"
#include "stack.h"
#include "trace.h"
#include "UniquePtr.h"
namespace art {
class Array;
class Class;
class ClassLinker;
class ClassLoader;
class Context;
struct DebugInvokeReq;
class Method;
class Monitor;
class Object;
class Runtime;
class ScopedObjectAccess;
class ScopedObjectAccessUnchecked;
class ShadowFrame;
class StackIndirectReferenceTable;
class StackTraceElement;
class StaticStorageBase;
class Thread;
class ThreadList;
class Throwable;
template<class T> class ObjectArray;
template<class T> class PrimitiveArray;
typedef PrimitiveArray<int32_t> IntArray;
// Thread priorities. These must match the Thread.MIN_PRIORITY,
// Thread.NORM_PRIORITY, and Thread.MAX_PRIORITY constants.
enum ThreadPriority {
kMinThreadPriority = 1,
kNormThreadPriority = 5,
kMaxThreadPriority = 10,
enum ThreadState {
kTerminated = 0, // Thread.TERMINATED JDWP TS_ZOMBIE
kRunnable = 1, // Thread.RUNNABLE JDWP TS_RUNNING
kTimedWaiting = 2, // Thread.TIMED_WAITING JDWP TS_WAIT - in Object.wait() with a timeout
kBlocked = 3, // Thread.BLOCKED JDWP TS_MONITOR - blocked on a monitor
kWaiting = 4, // Thread.WAITING JDWP TS_WAIT - in Object.wait()
kWaitingForGcToComplete = 5, // Thread.WAITING JDWP TS_WAIT - blocked waiting for GC
kWaitingPerformingGc = 6, // Thread.WAITING JDWP TS_WAIT - performing GC
kWaitingForDebuggerSend = 7, // Thread.WAITING JDWP TS_WAIT - blocked waiting for events to be sent
kWaitingForDebuggerToAttach = 8, // Thread.WAITING JDWP TS_WAIT - blocked waiting for debugger to attach
kWaitingInMainDebuggerLoop = 9, // Thread.WAITING JDWP TS_WAIT - blocking/reading/processing debugger events
kWaitingForDebuggerSuspension = 10, // Thread.WAITING JDWP TS_WAIT - waiting for debugger suspend all
kWaitingForJniOnLoad = 11, // Thread.WAITING JDWP TS_WAIT - waiting for execution of dlopen and JNI on load code
kWaitingForSignalCatcherOutput = 12, // Thread.WAITING JDWP TS_WAIT - waiting for signal catcher IO to complete
kWaitingInMainSignalCatcherLoop = 13, // Thread.WAITING JDWP TS_WAIT - blocking/reading/processing signals
kStarting = 14, // Thread.NEW JDWP TS_WAIT - native thread started, not yet ready to run managed code
kNative = 15, // Thread.RUNNABLE JDWP TS_RUNNING - running in a JNI native method
kSuspended = 16, // Thread.RUNNABLE JDWP TS_RUNNING - suspended by GC or debugger
class PACKED Thread {
// Space to throw a StackOverflowError in.
static const size_t kStackOverflowReservedBytes = 4 * KB;
#else // LLVM_x86 requires more memory to throw stack overflow exception.
static const size_t kStackOverflowReservedBytes = 8 * KB;
// Creates a new native thread corresponding to the given managed peer.
// Used to implement Thread.start.
static void CreateNativeThread(JNIEnv* env, jobject peer, size_t stack_size, bool daemon);
// Attaches the calling native thread to the runtime, returning the new native peer.
// Used to implement JNI AttachCurrentThread and AttachCurrentThreadAsDaemon calls.
static Thread* Attach(const char* thread_name, bool as_daemon, jobject thread_group);
// Reset internal state of child thread after fork.
void InitAfterFork();
static Thread* Current() __attribute__ ((pure)) {
// We rely on Thread::Current returning NULL for a detached thread, so it's not obvious
// that we can replace this with a direct %fs access on x86.
void* thread = pthread_getspecific(Thread::pthread_key_self_);
return reinterpret_cast<Thread*>(thread);
static Thread* FromManagedThread(const ScopedObjectAccessUnchecked& ts, Object* thread_peer)
static Thread* FromManagedThread(const ScopedObjectAccessUnchecked& ts, jobject thread)
// Translates 172 to pAllocArrayFromCode and so on.
static void DumpThreadOffset(std::ostream& os, uint32_t offset, size_t size_of_pointers);
// Dumps a one-line summary of thread state (used for operator<<).
void ShortDump(std::ostream& os) const;
// Dumps the detailed thread state and the thread stack (used for SIGQUIT).
void Dump(std::ostream& os) const
// Dumps the SIGQUIT per-thread header. 'thread' can be NULL for a non-attached thread, in which
// case we use 'tid' to identify the thread, and we'll include as much information as we can.
static void DumpState(std::ostream& os, const Thread* thread, pid_t tid)
ThreadState GetState() const
EXCLUSIVE_LOCKS_REQUIRED(GlobalSynchronization::thread_suspend_count_lock_) {
return state_;
ThreadState SetState(ThreadState new_state)
EXCLUSIVE_LOCKS_REQUIRED(GlobalSynchronization::thread_suspend_count_lock_) {
ThreadState old_state = state_;
if (new_state == kRunnable) {
// Sanity, should never become runnable with a pending suspension and should always hold
// share of mutator_lock_.
CHECK_EQ(GetSuspendCount(), 0);
state_ = new_state;
return old_state;
int GetSuspendCount() const
EXCLUSIVE_LOCKS_REQUIRED(GlobalSynchronization::thread_suspend_count_lock_) {
return suspend_count_;
int GetDebugSuspendCount() const
EXCLUSIVE_LOCKS_REQUIRED(GlobalSynchronization::thread_suspend_count_lock_) {
return debug_suspend_count_;
bool IsSuspended() const
EXCLUSIVE_LOCKS_REQUIRED(GlobalSynchronization::thread_suspend_count_lock_) {
int suspend_count = GetSuspendCount();
return suspend_count != 0 && GetState() != kRunnable;
void ModifySuspendCount(int delta, bool for_debugger)
// Called when thread detected that the thread_suspend_count_ was non-zero. Gives up share of
// mutator_lock_ and waits until it is resumed and thread_suspend_count_ is zero.
void FullSuspendCheck()
// Transition from non-runnable to runnable state acquiring share on mutator_lock_.
ThreadState TransitionFromSuspendedToRunnable()
// Transition from runnable into a state where mutator privileges are denied. Releases share of
// mutator lock.
void TransitionFromRunnableToSuspended(ThreadState new_state)
// Wait for a debugger suspension on the thread associated with the given peer. Returns the
// thread on success, else NULL. If the thread should be suspended then request_suspension should
// be true on entry. If the suspension times out then *timeout is set to true.
static Thread* SuspendForDebugger(jobject peer, bool request_suspension, bool* timeout)
// Once called thread suspension will cause an assertion failure.
#ifndef NDEBUG
const char* StartAssertNoThreadSuspension(const char* cause) {
CHECK(cause != NULL);
const char* previous_cause = last_no_thread_suspension_cause_;
last_no_thread_suspension_cause_ = cause;
return previous_cause;
const char* StartAssertNoThreadSuspension(const char* cause) {
CHECK(cause != NULL);
return NULL;
// End region where no thread suspension is expected.
#ifndef NDEBUG
void EndAssertNoThreadSuspension(const char* old_cause) {
CHECK(old_cause != NULL || no_thread_suspension_ == 1);
CHECK_GT(no_thread_suspension_, 0U);
last_no_thread_suspension_cause_ = old_cause;
void EndAssertNoThreadSuspension(const char*) {
#ifndef NDEBUG
void AssertThreadSuspensionIsAllowable(bool check_locks = true) const;
void AssertThreadSuspensionIsAllowable(bool check_locks = true) const {
check_locks = !check_locks; // Keep GCC happy about unused parameters.
bool CanAccessDirectReferences() const {
// TODO: when we have a moving collector, we'll need: return state_ == kRunnable;
return true;
bool IsDaemon() const {
return daemon_;
bool HoldsLock(Object*);
* Changes the priority of this thread to match that of the java.lang.Thread object.
* We map a priority value from 1-10 to Linux "nice" values, where lower
* numbers indicate higher priority.
void SetNativePriority(int newPriority);
* Returns the thread priority for the current thread by querying the system.
* This is useful when attaching a thread through JNI.
* Returns a value from 1 to 10 (compatible with java.lang.Thread values).
static int GetNativePriority();
uint32_t GetThinLockId() const {
return thin_lock_id_;
pid_t GetTid() const {
return tid_;
// Returns the java.lang.Thread's name, or NULL if this Thread* doesn't have a peer.
String* GetThreadName(const ScopedObjectAccessUnchecked& ts) const
// Sets 'name' to the java.lang.Thread's name. This requires no transition to managed code,
// allocation, or locking.
void GetThreadName(std::string& name) const;
// Sets the thread's name.
void SetThreadName(const char* name) SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_);
Object* GetPeer() const SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_) {
return peer_;
bool HasPeer() const {
return peer_ != NULL;
Object* GetThreadGroup(const ScopedObjectAccessUnchecked& ts) const
RuntimeStats* GetStats() {
return &stats_;
bool IsStillStarting() const;
bool IsExceptionPending() const {
return exception_ != NULL;
Throwable* GetException() const SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_) {
return exception_;
void AssertNoPendingException() const;
void SetException(Throwable* new_exception)
SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_) {
CHECK(new_exception != NULL);
// TODO: CHECK(exception_ == NULL);
exception_ = new_exception; // TODO
void ClearException() {
exception_ = NULL;
// Find catch block and perform long jump to appropriate exception handle
void DeliverException() SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_);
Context* GetLongJumpContext();
void ReleaseLongJumpContext(Context* context) {
DCHECK(long_jump_context_ == NULL);
long_jump_context_ = context;
Method* GetCurrentMethod(uint32_t* dex_pc = NULL, size_t* frame_id = NULL) const
void SetTopOfStack(void* stack, uintptr_t pc) {
Method** top_method = reinterpret_cast<Method**>(stack);
bool HasManagedStack() const {
return managed_stack_.GetTopQuickFrame() != NULL || managed_stack_.GetTopShadowFrame() != NULL;
// If 'msg' is NULL, no detail message is set.
void ThrowNewException(const char* exception_class_descriptor, const char* msg)
// If 'msg' is NULL, no detail message is set. An exception must be pending, and will be
// used as the new exception's cause.
void ThrowNewWrappedException(const char* exception_class_descriptor, const char* msg)
void ThrowNewExceptionF(const char* exception_class_descriptor, const char* fmt, ...)
__attribute__((format(printf, 3, 4)))
void ThrowNewExceptionV(const char* exception_class_descriptor, const char* fmt, va_list ap)
// OutOfMemoryError is special, because we need to pre-allocate an instance.
// Only the GC should call this.
void ThrowOutOfMemoryError(const char* msg)
//QuickFrameIterator FindExceptionHandler(void* throw_pc, void** handler_pc);
void* FindExceptionHandlerInMethod(const Method* method,
void* throw_pc,
const DexFile& dex_file,
ClassLinker* class_linker);
static void Startup();
static void FinishStartup();
static void Shutdown();
// JNI methods
JNIEnvExt* GetJniEnv() const {
return jni_env_;
// Convert a jobject into a Object*
Object* DecodeJObject(jobject obj)
// Implements java.lang.Thread.interrupted.
bool Interrupted() {
MutexLock mu(*wait_mutex_);
bool interrupted = interrupted_;
interrupted_ = false;
return interrupted;
// Implements java.lang.Thread.isInterrupted.
bool IsInterrupted() {
MutexLock mu(*wait_mutex_);
return interrupted_;
void Interrupt() {
MutexLock mu(*wait_mutex_);
if (interrupted_) {
interrupted_ = true;
void Notify() {
MutexLock mu(*wait_mutex_);
ClassLoader* GetClassLoaderOverride()
SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_) {
return class_loader_override_;
void SetClassLoaderOverride(ClassLoader* class_loader_override) {
class_loader_override_ = class_loader_override;
// Create the internal representation of a stack trace, that is more time
// and space efficient to compute than the StackTraceElement[]
jobject CreateInternalStackTrace(const ScopedObjectAccess& soa) const
// Convert an internal stack trace representation (returned by CreateInternalStackTrace) to a
// StackTraceElement[]. If output_array is NULL, a new array is created, otherwise as many
// frames as will fit are written into the given array. If stack_depth is non-NULL, it's updated
// with the number of valid frames in the returned array.
static jobjectArray InternalStackTraceToStackTraceElementArray(JNIEnv* env, jobject internal,
jobjectArray output_array = NULL, int* stack_depth = NULL);
void VisitRoots(Heap::RootVisitor* visitor, void* arg)
void VerifyStack() SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_);
void VerifyStack() SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_){}
// Offsets of various members of native Thread class, used by compiled code.
static ThreadOffset SelfOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, self_));
static ThreadOffset ExceptionOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, exception_));
static ThreadOffset ThinLockIdOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, thin_lock_id_));
static ThreadOffset CardTableOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, card_table_));
static ThreadOffset SuspendCountOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, suspend_count_));
static ThreadOffset StateOffset() {
return ThreadOffset(OFFSETOF_VOLATILE_MEMBER(Thread, state_));
// Size of stack less any space reserved for stack overflow
size_t GetStackSize() {
return stack_size_ - (stack_end_ - stack_begin_);
// Set the stack end to that to be used during a stack overflow
void SetStackEndForStackOverflow() SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_);
// Set the stack end to that to be used during regular execution
void ResetDefaultStackEnd() {
// Our stacks grow down, so we want stack_end_ to be near there, but reserving enough room
// to throw a StackOverflowError.
stack_end_ = stack_begin_ + kStackOverflowReservedBytes;
static ThreadOffset StackEndOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, stack_end_));
static ThreadOffset JniEnvOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, jni_env_));
static ThreadOffset TopOfManagedStackOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, managed_stack_) +
static ThreadOffset TopOfManagedStackPcOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, managed_stack_) +
const ManagedStack* GetManagedStack() const {
return &managed_stack_;
// Linked list recording fragments of managed stack.
void PushManagedStackFragment(ManagedStack* fragment) {
void PopManagedStackFragment(const ManagedStack& fragment) {
ShadowFrame* PushShadowFrame(ShadowFrame* new_top_frame) {
return managed_stack_.PushShadowFrame(new_top_frame);
ShadowFrame* PopShadowFrame() {
return managed_stack_.PopShadowFrame();
static ThreadOffset TopShadowFrameOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, managed_stack_) +
// Number of references allocated in ShadowFrames on this thread
size_t NumShadowFrameReferences() const {
return managed_stack_.NumShadowFrameReferences();
// Number of references in SIRTs on this thread
size_t NumSirtReferences();
// Number of references allocated in SIRTs & shadow frames on this thread
size_t NumStackReferences() {
return NumSirtReferences() + NumShadowFrameReferences();
// Is the given obj in this thread's stack indirect reference table?
bool SirtContains(jobject obj);
void SirtVisitRoots(Heap::RootVisitor* visitor, void* arg);
void PushSirt(StackIndirectReferenceTable* sirt);
StackIndirectReferenceTable* PopSirt();
static ThreadOffset TopSirtOffset() {
return ThreadOffset(OFFSETOF_MEMBER(Thread, top_sirt_));
DebugInvokeReq* GetInvokeReq() {
return debug_invoke_req_;
void SetDebuggerUpdatesEnabled(bool enabled);
const std::vector<TraceStackFrame>* GetTraceStack() const {
return trace_stack_;
bool IsTraceStackEmpty() const {
return trace_stack_->empty();
void PushTraceStackFrame(const TraceStackFrame& frame) {
TraceStackFrame PopTraceStackFrame() {
TraceStackFrame frame = trace_stack_->back();
return frame;
BaseMutex* GetHeldMutex(MutexLevel level) const {
return held_mutexes_[level];
void SetHeldMutex(MutexLevel level, BaseMutex* mutex) {
held_mutexes_[level] = mutex;
// We have no control over the size of 'bool', but want our boolean fields
// to be 4-byte quantities.
typedef uint32_t bool32_t;
explicit Thread(bool daemon);
~Thread() LOCKS_EXCLUDED(GlobalSynchronization::mutator_lock_,
void Destroy();
friend class ThreadList; // For ~Thread and Destroy.
void CreatePeer(const char* name, bool as_daemon, jobject thread_group);
friend class Runtime; // For CreatePeer.
// TODO: remove, callers should use GetState and hold the appropriate locks. Used only by
// ShortDump.
ThreadState GetStateUnsafe() const NO_THREAD_SAFETY_ANALYSIS {
return state_;
void DumpState(std::ostream& os) const;
void DumpStack(std::ostream& os) const
// Out-of-line conveniences for debugging in gdb.
static Thread* CurrentFromGdb(); // Like Thread::Current.
// Like Thread::Dump(std::cerr).
void DumpFromGdb() const SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_);
static void* CreateCallback(void* arg);
void HandleUncaughtExceptions(const ScopedObjectAccess& soa)
void RemoveFromThreadGroup(const ScopedObjectAccess& soa)
void Init();
void InitCardTable();
void InitCpu();
void InitFunctionPointers();
void InitTid();
void InitPthreadKeySelf();
void InitStackHwm();
void NotifyLocked() EXCLUSIVE_LOCKS_REQUIRED(wait_mutex_) {
if (wait_monitor_ != NULL) {
static void ThreadExitCallback(void* arg);
// TLS key used to retrieve the Thread*.
static pthread_key_t pthread_key_self_;
// Used to notify threads that they should attempt to resume, they will suspend again if
// their suspend count is > 0.
static ConditionVariable* resume_cond_
// --- Frequently accessed fields first for short offsets ---
// A non-zero value is used to tell the current thread to enter a safe point
// at the next poll.
int suspend_count_ GUARDED_BY(GlobalSynchronization::thread_suspend_count_lock_);
// The biased card table, see CardTable for details
byte* card_table_;
// The pending exception or NULL.
Throwable* exception_;
// The end of this thread's stack. This is the lowest safely-addressable address on the stack.
// We leave extra space so there's room for the code that throws StackOverflowError.
byte* stack_end_;
// The top of the managed stack often manipulated directly by compiler generated code.
ManagedStack managed_stack_;
// Every thread may have an associated JNI environment
JNIEnvExt* jni_env_;
// Initialized to "this". On certain architectures (such as x86) reading
// off of Thread::Current is easy but getting the address of Thread::Current
// is hard. This field can be read off of Thread::Current to give the address.
Thread* self_;
volatile ThreadState state_ GUARDED_BY(GlobalSynchronization::thread_suspend_count_lock_);
// Our managed peer (an instance of java.lang.Thread).
Object* peer_;
// The "lowest addressable byte" of the stack
byte* stack_begin_;
// Size of the stack
size_t stack_size_;
// Thin lock thread id. This is a small integer used by the thin lock implementation.
// This is not to be confused with the native thread's tid, nor is it the value returned
// by java.lang.Thread.getId --- this is a distinct value, used only for locking. One
// important difference between this id and the ids visible to managed code is that these
// ones get reused (to ensure that they fit in the number of bits available).
uint32_t thin_lock_id_;
// System thread id.
pid_t tid_;
// Guards the 'interrupted_' and 'wait_monitor_' members.
mutable Mutex* wait_mutex_ DEFAULT_MUTEX_ACQUIRED_AFTER;
ConditionVariable* wait_cond_ GUARDED_BY(wait_mutex_);
// Pointer to the monitor lock we're currently waiting on (or NULL).
Monitor* wait_monitor_ GUARDED_BY(wait_mutex_);
// Thread "interrupted" status; stays raised until queried or thrown.
bool32_t interrupted_ GUARDED_BY(wait_mutex_);
// The next thread in the wait set this thread is part of.
Thread* wait_next_;
// If we're blocked in MonitorEnter, this is the object we're trying to lock.
Object* monitor_enter_object_;
friend class Monitor;
// Top of linked list of stack indirect reference tables or NULL for none
StackIndirectReferenceTable* top_sirt_;
Runtime* runtime_;
RuntimeStats stats_;
// Needed to get the right ClassLoader in JNI_OnLoad, but also
// useful for testing.
ClassLoader* class_loader_override_;
// Thread local, lazily allocated, long jump context. Used to deliver exceptions.
Context* long_jump_context_;
// A boolean telling us whether we're recursively throwing OOME.
bool32_t throwing_OutOfMemoryError_;
// How much of 'suspend_count_' is by request of the debugger, used to set things right
// when the debugger detaches. Must be <= suspend_count_.
int debug_suspend_count_ GUARDED_BY(GlobalSynchronization::thread_suspend_count_lock_);
// JDWP invoke-during-breakpoint support.
DebugInvokeReq* debug_invoke_req_;
// Additional stack used by method tracer to store method and return pc values.
// Stored as a pointer since std::vector is not PACKED.
std::vector<TraceStackFrame>* trace_stack_;
// A cached copy of the java.lang.Thread's name.
std::string* name_;
// Is the thread a daemon?
const bool32_t daemon_;
// A cached pthread_t for the pthread underlying this Thread*.
pthread_t pthread_self_;
// Support for Mutex lock hierarchy bug detection.
BaseMutex* held_mutexes_[kMaxMutexLevel + 1];
// A positive value implies we're in a region where thread suspension isn't expected.
uint32_t no_thread_suspension_;
// Cause for last suspension.
const char* last_no_thread_suspension_cause_;
// Runtime support function pointers
// TODO: move this near the top, since changing its offset requires all oats to be recompiled!
EntryPoints entrypoints_;
// How many times has our pthread key's destructor been called?
uint32_t thread_exit_check_count_;
std::ostream& operator<<(std::ostream& os, const Thread& thread);
std::ostream& operator<<(std::ostream& os, const ThreadState& state);
} // namespace art
#endif // ART_SRC_THREAD_H_