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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_SRC_SCOPED_THREAD_STATE_CHANGE_H_
#define ART_SRC_SCOPED_THREAD_STATE_CHANGE_H_
#include "casts.h"
#include "jni_internal.h"
#include "thread.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_)
: self_(self), thread_state_(new_thread_state), expected_has_no_thread_(false) {
if (self_ == NULL) {
// Value chosen arbitrarily and won't be used in the destructor since thread_ == NULL.
old_thread_state_ = kTerminated;
MutexLock mu(NULL, *Locks::runtime_shutdown_lock_);
Runtime* runtime = Runtime::Current();
CHECK(runtime == NULL || !runtime->IsStarted() || runtime->IsShuttingDown());
} else {
bool runnable_transition;
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();
runnable_transition = old_thread_state_ == kRunnable || new_thread_state == kRunnable;
if (!runnable_transition) {
// A suspended transition to another effectively suspended transition, ok to use Unsafe.
self_->SetState(new_thread_state);
}
if (runnable_transition && old_thread_state_ != new_thread_state) {
if (new_thread_state == kRunnable) {
self_->TransitionFromSuspendedToRunnable();
} else {
DCHECK_EQ(old_thread_state_, kRunnable);
self_->TransitionFromRunnableToSuspended(new_thread_state);
}
}
}
}
~ScopedThreadStateChange() LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_) {
if (self_ == NULL) {
if (!expected_has_no_thread_) {
MutexLock mu(NULL, *Locks::runtime_shutdown_lock_);
Runtime* runtime = Runtime::Current();
bool shutting_down = (runtime == NULL) || runtime->IsShuttingDown();
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_;
DISALLOW_COPY_AND_ASSIGN(ScopedThreadStateChange);
};
// 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 ScopedThreadStateChange {
public:
explicit ScopedObjectAccessUnchecked(JNIEnv* env)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_)
: ScopedThreadStateChange(ThreadForEnv(env), kRunnable),
env_(reinterpret_cast<JNIEnvExt*>(env)), vm_(env_->vm) {
self_->VerifyStack();
}
explicit ScopedObjectAccessUnchecked(Thread* self)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_)
: ScopedThreadStateChange(self, kRunnable),
env_(reinterpret_cast<JNIEnvExt*>(self->GetJniEnv())),
vm_(env_ != NULL ? env_->vm : NULL) {
if (Vm() != NULL && !Vm()->work_around_app_jni_bugs && self != Thread::Current()) {
UnexpectedThreads(self, Thread::Current());
}
self_->VerifyStack();
}
// 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)
: ScopedThreadStateChange(), env_(NULL), vm_(reinterpret_cast<JavaVMExt*>(vm)) {}
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.
* Part of the ScopedJniThreadState as native code shouldn't be working on raw Object* without
* having transitioned its state.
*
* We need to allow the same reference to be added multiple times.
*
* 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.
*
* Returns the local reference (currently just the same pointer that was
* passed in), or NULL on failure.
*/
template<typename T>
T AddLocalReference(Object* obj) const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
DCHECK_EQ(thread_state_, kRunnable); // Don't work with raw objects in non-runnable states.
if (obj == NULL) {
return NULL;
}
DCHECK_NE((reinterpret_cast<uintptr_t>(obj) & 0xffff0000), 0xebad0000);
IndirectReferenceTable& locals = Env()->locals;
uint32_t cookie = Env()->local_ref_cookie;
IndirectRef ref = locals.Add(cookie, obj);
#if 0 // TODO: fix this to understand PushLocalFrame, so we can turn it on.
if (Env()->check_jni) {
size_t entry_count = locals.Capacity();
if (entry_count > 16) {
LOG(WARNING) << "Warning: more than 16 JNI local references: "
<< entry_count << " (most recent was a " << PrettyTypeOf(obj) << ")\n"
<< Dumpable<IndirectReferenceTable>(locals);
// TODO: LOG(FATAL) in a later release?
}
}
#endif
if (Vm()->work_around_app_jni_bugs) {
// Hand out direct pointers to support broken old apps.
return reinterpret_cast<T>(obj);
}
return reinterpret_cast<T>(ref);
}
template<typename T>
T Decode(jobject obj) const
LOCKS_EXCLUDED(JavaVMExt::globals_lock,
JavaVMExt::weak_globals_lock)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK_EQ(thread_state_, kRunnable); // Don't work with raw objects in non-runnable states.
return down_cast<T>(Self()->DecodeJObject(obj));
}
Field* DecodeField(jfieldID fid) const
LOCKS_EXCLUDED(JavaVMExt::globals_lock,
JavaVMExt::weak_globals_lock)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK_EQ(thread_state_, kRunnable); // Don't work with raw objects in non-runnable states.
#ifdef MOVING_GARBAGE_COLLECTOR
// TODO: we should make these unique weak globals if Field instances can ever move.
UNIMPLEMENTED(WARNING);
#endif
return reinterpret_cast<Field*>(fid);
}
jfieldID EncodeField(Field* field) const
LOCKS_EXCLUDED(JavaVMExt::globals_lock,
JavaVMExt::weak_globals_lock)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK_EQ(thread_state_, kRunnable); // Don't work with raw objects in non-runnable states.
#ifdef MOVING_GARBAGE_COLLECTOR
UNIMPLEMENTED(WARNING);
#endif
return reinterpret_cast<jfieldID>(field);
}
AbstractMethod* DecodeMethod(jmethodID mid) const
LOCKS_EXCLUDED(JavaVMExt::globals_lock,
JavaVMExt::weak_globals_lock)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK_EQ(thread_state_, kRunnable); // Don't work with raw objects in non-runnable states.
#ifdef MOVING_GARBAGE_COLLECTOR
// TODO: we should make these unique weak globals if Method instances can ever move.
UNIMPLEMENTED(WARNING);
#endif
return reinterpret_cast<AbstractMethod*>(mid);
}
jmethodID EncodeMethod(AbstractMethod* method) const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
Locks::mutator_lock_->AssertSharedHeld(Self());
DCHECK_EQ(thread_state_, kRunnable); // Don't work with raw objects in non-runnable states.
#ifdef MOVING_GARBAGE_COLLECTOR
UNIMPLEMENTED(WARNING);
#endif
return reinterpret_cast<jmethodID>(method);
}
private:
static Thread* ThreadForEnv(JNIEnv* env) {
JNIEnvExt* full_env(reinterpret_cast<JNIEnvExt*>(env));
bool work_around_app_jni_bugs = full_env->vm->work_around_app_jni_bugs;
Thread* env_self = full_env->self;
Thread* self = work_around_app_jni_bugs ? Thread::Current() : env_self;
if (!work_around_app_jni_bugs && self != env_self) {
UnexpectedThreads(env_self, self);
}
return self;
}
static void UnexpectedThreads(Thread* found_self, Thread* expected_self) {
// TODO: pass through function name so we can use it here instead of NULL...
JniAbortF(NULL, "JNIEnv for %s used on %s",
found_self != NULL ? ToStr<Thread>(*found_self).c_str() : "NULL",
expected_self != NULL ? ToStr<Thread>(*expected_self).c_str() : "NULL");
}
// The full JNIEnv.
JNIEnvExt* const env_;
// The full JavaVM.
JavaVMExt* const vm_;
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_)
: ScopedObjectAccessUnchecked(env) {
Locks::mutator_lock_->AssertSharedHeld(Self());
}
explicit ScopedObjectAccess(Thread* self)
LOCKS_EXCLUDED(Locks::thread_suspend_count_lock_)
SHARED_LOCK_FUNCTION(Locks::mutator_lock_)
: ScopedObjectAccessUnchecked(self) {
Locks::mutator_lock_->AssertSharedHeld(Self());
}
~ScopedObjectAccess() UNLOCK_FUNCTION(Locks::mutator_lock_) {
// 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_SRC_SCOPED_THREAD_STATE_CHANGE_H_