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/*
* Copyright (C) 2012 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_SCOPED_THREAD_STATE_CHANGE_H_
#define ART_RUNTIME_SCOPED_THREAD_STATE_CHANGE_H_
#include "base/casts.h"
#include "jni_internal-inl.h"
#include "thread-inl.h"
#include "verify_object.h"
namespace art {
// Scoped change into and out of a particular state. Handles Runnable transitions that require
// more complicated suspension checking. The subclasses ScopedObjectAccessUnchecked and
// ScopedObjectAccess are used to handle the change into Runnable to Get direct access to objects,
// the unchecked variant doesn't aid annotalysis.
class ScopedThreadStateChange {
public:
ScopedThreadStateChange(Thread* self, ThreadState new_thread_state)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) ALWAYS_INLINE
: self_(self), thread_state_(new_thread_state), expected_has_no_thread_(false) {
if (UNLIKELY(self_ == NULL)) {
// Value chosen arbitrarily and won't be used in the destructor since thread_ == NULL.
old_thread_state_ = kTerminated;
Runtime* runtime = Runtime::Current();
CHECK(runtime == NULL || !runtime->IsStarted() || runtime->IsShuttingDown(self_));
} else {
DCHECK_EQ(self, Thread::Current());
// Read state without locks, ok as state is effectively thread local and we're not interested
// in the suspend count (this will be handled in the runnable transitions).
old_thread_state_ = self->GetState();
if (old_thread_state_ != new_thread_state) {
if (new_thread_state == kRunnable) {
self_->TransitionFromSuspendedToRunnable();
} else if (old_thread_state_ == kRunnable) {
self_->TransitionFromRunnableToSuspended(new_thread_state);
} else {
// A suspended transition to another effectively suspended transition, ok to use Unsafe.
self_->SetState(new_thread_state);
}
}
}
}
~ScopedThreadStateChange() LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) ALWAYS_INLINE {
if (UNLIKELY(self_ == NULL)) {
if (!expected_has_no_thread_) {
Runtime* runtime = Runtime::Current();
bool shutting_down = (runtime == NULL) || runtime->IsShuttingDown(nullptr);
CHECK(shutting_down);
}
} else {
if (old_thread_state_ != thread_state_) {
if (old_thread_state_ == kRunnable) {
self_->TransitionFromSuspendedToRunnable();
} else if (thread_state_ == kRunnable) {
self_->TransitionFromRunnableToSuspended(old_thread_state_);
} else {
// A suspended transition to another effectively suspended transition, ok to use Unsafe.
self_->SetState(old_thread_state_);
}
}
}
}
Thread* Self() const {
return self_;
}
protected:
// Constructor used by ScopedJniThreadState for an unattached thread that has access to the VM*.
ScopedThreadStateChange()
: self_(NULL), thread_state_(kTerminated), old_thread_state_(kTerminated),
expected_has_no_thread_(true) {}
Thread* const self_;
const ThreadState thread_state_;
private:
ThreadState old_thread_state_;
const bool expected_has_no_thread_;
friend class ScopedObjectAccessUnchecked;
DISALLOW_COPY_AND_ASSIGN(ScopedThreadStateChange);
};
// Assumes we are already runnable.
class ScopedObjectAccessAlreadyRunnable {
public:
Thread* Self() const {
return self_;
}
JNIEnvExt* Env() const {
return env_;
}
JavaVMExt* Vm() const {
return vm_;
}
/*
* Add a local reference for an object to the indirect reference table associated with the
* current stack frame. When the native function returns, the reference will be discarded.
*
* We need to allow the same reference to be added multiple times, and cope with NULL.
*
* This will be called on otherwise unreferenced objects. We cannot do GC allocations here, and
* it's best if we don't grab a mutex.
*/
template<typename T>
T AddLocalReference(mirror::Object* obj) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK(IsRunnable()); // Don't work with raw objects in non-runnable states.
if (obj == NULL) {
return NULL;
}
DCHECK_NE((reinterpret_cast<uintptr_t>(obj) & 0xffff0000), 0xebad0000);
return Env()->AddLocalReference<T>(obj);
}
template<typename T>
T Decode(jobject obj) const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK(IsRunnable()); // Don't work with raw objects in non-runnable states.
return down_cast<T>(Self()->DecodeJObject(obj));
}
mirror::ArtField* DecodeField(jfieldID fid) const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK(IsRunnable()); // Don't work with raw objects in non-runnable states.
CHECK(!kMovingFields);
mirror::ArtField* field = reinterpret_cast<mirror::ArtField*>(fid);
return ReadBarrier::BarrierForRoot<mirror::ArtField, kWithReadBarrier>(&field);
}
jfieldID EncodeField(mirror::ArtField* field) const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK(IsRunnable()); // Don't work with raw objects in non-runnable states.
CHECK(!kMovingFields);
return reinterpret_cast<jfieldID>(field);
}
mirror::ArtMethod* DecodeMethod(jmethodID mid) const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK(IsRunnable()); // Don't work with raw objects in non-runnable states.
CHECK(!kMovingMethods);
mirror::ArtMethod* method = reinterpret_cast<mirror::ArtMethod*>(mid);
return ReadBarrier::BarrierForRoot<mirror::ArtMethod, kWithReadBarrier>(&method);
}
jmethodID EncodeMethod(mirror::ArtMethod* method) const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK(IsRunnable()); // Don't work with raw objects in non-runnable states.
CHECK(!kMovingMethods);
return reinterpret_cast<jmethodID>(method);
}
bool IsRunnable() const {
return self_->GetState() == kRunnable;
}
protected:
explicit ScopedObjectAccessAlreadyRunnable(JNIEnv* env)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) ALWAYS_INLINE
: self_(ThreadForEnv(env)), env_(down_cast<JNIEnvExt*>(env)), vm_(env_->vm) {
}
explicit ScopedObjectAccessAlreadyRunnable(Thread* self)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) ALWAYS_INLINE
: self_(self), env_(down_cast<JNIEnvExt*>(self->GetJniEnv())),
vm_(env_ != nullptr ? env_->vm : nullptr) {
}
// Used when we want a scoped JNI thread state but have no thread/JNIEnv. Consequently doesn't
// change into Runnable or acquire a share on the mutator_lock_.
explicit ScopedObjectAccessAlreadyRunnable(JavaVM* vm)
: self_(nullptr), env_(nullptr), vm_(down_cast<JavaVMExt*>(vm)) {}
// Here purely to force inlining.
~ScopedObjectAccessAlreadyRunnable() ALWAYS_INLINE {
}
// Self thread, can be null.
Thread* const self_;
// The full JNIEnv.
JNIEnvExt* const env_;
// The full JavaVM.
JavaVMExt* const vm_;
};
// Entry/exit processing for transitions from Native to Runnable (ie within JNI functions).
//
// This class performs the necessary thread state switching to and from Runnable and lets us
// amortize the cost of working out the current thread. Additionally it lets us check (and repair)
// apps that are using a JNIEnv on the wrong thread. The class also decodes and encodes Objects
// into jobjects via methods of this class. Performing this here enforces the Runnable thread state
// for use of Object, thereby inhibiting the Object being modified by GC whilst native or VM code
// is also manipulating the Object.
//
// The destructor transitions back to the previous thread state, typically Native. In this state
// GC and thread suspension may occur.
//
// For annotalysis the subclass ScopedObjectAccess (below) makes it explicit that a shared of
// the mutator_lock_ will be acquired on construction.
class ScopedObjectAccessUnchecked : public ScopedObjectAccessAlreadyRunnable {
public:
explicit ScopedObjectAccessUnchecked(JNIEnv* env)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) ALWAYS_INLINE
: ScopedObjectAccessAlreadyRunnable(env), tsc_(Self(), kRunnable) {
Self()->VerifyStack();
Locks::mutator_lock_->AssertSharedHeld(Self());
}
explicit ScopedObjectAccessUnchecked(Thread* self)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) ALWAYS_INLINE
: ScopedObjectAccessAlreadyRunnable(self), tsc_(self, kRunnable) {
Self()->VerifyStack();
Locks::mutator_lock_->AssertSharedHeld(Self());
}
// Used when we want a scoped JNI thread state but have no thread/JNIEnv. Consequently doesn't
// change into Runnable or acquire a share on the mutator_lock_.
explicit ScopedObjectAccessUnchecked(JavaVM* vm) ALWAYS_INLINE
: ScopedObjectAccessAlreadyRunnable(vm), tsc_() {}
private:
// The scoped thread state change makes sure that we are runnable and restores the thread state
// in the destructor.
const ScopedThreadStateChange tsc_;
DISALLOW_COPY_AND_ASSIGN(ScopedObjectAccessUnchecked);
};
// Annotalysis helping variant of the above.
class ScopedObjectAccess : public ScopedObjectAccessUnchecked {
public:
explicit ScopedObjectAccess(JNIEnv* env)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_)
SHARED_LOCK_FUNCTION(Locks::mutator_lock_) ALWAYS_INLINE
: ScopedObjectAccessUnchecked(env) {
}
explicit ScopedObjectAccess(Thread* self)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_)
SHARED_LOCK_FUNCTION(Locks::mutator_lock_) ALWAYS_INLINE
: ScopedObjectAccessUnchecked(self) {
}
~ScopedObjectAccess() UNLOCK_FUNCTION(Locks::mutator_lock_) ALWAYS_INLINE {
// Base class will release share of lock. Invoked after this destructor.
}
private:
// TODO: remove this constructor. It is used by check JNI's ScopedCheck to make it believe that
// routines operating with just a VM are sound, they are not, but when you have just a VM
// you cannot call the unsound routines.
explicit ScopedObjectAccess(JavaVM* vm)
SHARED_LOCK_FUNCTION(Locks::mutator_lock_)
: ScopedObjectAccessUnchecked(vm) {}
friend class ScopedCheck;
DISALLOW_COPY_AND_ASSIGN(ScopedObjectAccess);
};
} // namespace art
#endif // ART_RUNTIME_SCOPED_THREAD_STATE_CHANGE_H_