/* Copyright (C) 2017 The Android Open Source Project
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This file implements interfaces from the file jvmti.h. This implementation
* is licensed under the same terms as the file jvmti.h. The
* copyright and license information for the file jvmti.h follows.
*
* Copyright (c) 2003, 2011, 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* 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 "ti_thread.h"
#include <android-base/logging.h>
#include <android-base/strings.h>
#include "art_field-inl.h"
#include "art_jvmti.h"
#include "base/mutex.h"
#include "events-inl.h"
#include "gc/system_weak.h"
#include "gc/collector_type.h"
#include "gc/gc_cause.h"
#include "gc/scoped_gc_critical_section.h"
#include "gc_root-inl.h"
#include "jni_internal.h"
#include "mirror/class.h"
#include "mirror/object-inl.h"
#include "mirror/string.h"
#include "nativehelper/scoped_local_ref.h"
#include "nativehelper/scoped_utf_chars.h"
#include "obj_ptr.h"
#include "runtime.h"
#include "runtime_callbacks.h"
#include "scoped_thread_state_change-inl.h"
#include "thread-current-inl.h"
#include "thread_list.h"
#include "ti_phase.h"
#include "well_known_classes.h"
namespace openjdkjvmti {
art::ArtField* ThreadUtil::context_class_loader_ = nullptr;
struct ThreadCallback : public art::ThreadLifecycleCallback {
jthread GetThreadObject(art::Thread* self) REQUIRES_SHARED(art::Locks::mutator_lock_) {
if (self->GetPeer() == nullptr) {
return nullptr;
}
return self->GetJniEnv()->AddLocalReference<jthread>(self->GetPeer());
}
template <ArtJvmtiEvent kEvent>
void Post(art::Thread* self) REQUIRES_SHARED(art::Locks::mutator_lock_) {
DCHECK_EQ(self, art::Thread::Current());
ScopedLocalRef<jthread> thread(self->GetJniEnv(), GetThreadObject(self));
art::ScopedThreadSuspension sts(self, art::ThreadState::kNative);
event_handler->DispatchEvent<kEvent>(self,
reinterpret_cast<JNIEnv*>(self->GetJniEnv()),
thread.get());
}
void ThreadStart(art::Thread* self) OVERRIDE REQUIRES_SHARED(art::Locks::mutator_lock_) {
if (!started) {
// Runtime isn't started. We only expect at most the signal handler or JIT threads to be
// started here.
if (art::kIsDebugBuild) {
std::string name;
self->GetThreadName(name);
if (name != "JDWP" &&
name != "Signal Catcher" &&
!android::base::StartsWith(name, "Jit thread pool")) {
LOG(FATAL) << "Unexpected thread before start: " << name << " id: "
<< self->GetThreadId();
}
}
return;
}
Post<ArtJvmtiEvent::kThreadStart>(self);
}
void ThreadDeath(art::Thread* self) OVERRIDE REQUIRES_SHARED(art::Locks::mutator_lock_) {
Post<ArtJvmtiEvent::kThreadEnd>(self);
}
EventHandler* event_handler = nullptr;
bool started = false;
};
ThreadCallback gThreadCallback;
void ThreadUtil::Register(EventHandler* handler) {
art::Runtime* runtime = art::Runtime::Current();
gThreadCallback.started = runtime->IsStarted();
gThreadCallback.event_handler = handler;
art::ScopedThreadStateChange stsc(art::Thread::Current(),
art::ThreadState::kWaitingForDebuggerToAttach);
art::ScopedSuspendAll ssa("Add thread callback");
runtime->GetRuntimeCallbacks()->AddThreadLifecycleCallback(&gThreadCallback);
}
void ThreadUtil::VMInitEventSent() {
// We should have already started.
DCHECK(gThreadCallback.started);
// We moved to VMInit. Report the main thread as started (it was attached early, and must not be
// reported until Init.
gThreadCallback.Post<ArtJvmtiEvent::kThreadStart>(art::Thread::Current());
}
void ThreadUtil::CacheData() {
// We must have started since it is now safe to cache our data;
gThreadCallback.started = true;
art::ScopedObjectAccess soa(art::Thread::Current());
art::ObjPtr<art::mirror::Class> thread_class =
soa.Decode<art::mirror::Class>(art::WellKnownClasses::java_lang_Thread);
CHECK(thread_class != nullptr);
context_class_loader_ = thread_class->FindDeclaredInstanceField("contextClassLoader",
"Ljava/lang/ClassLoader;");
CHECK(context_class_loader_ != nullptr);
}
void ThreadUtil::Unregister() {
art::ScopedThreadStateChange stsc(art::Thread::Current(),
art::ThreadState::kWaitingForDebuggerToAttach);
art::ScopedSuspendAll ssa("Remove thread callback");
art::Runtime* runtime = art::Runtime::Current();
runtime->GetRuntimeCallbacks()->RemoveThreadLifecycleCallback(&gThreadCallback);
}
jvmtiError ThreadUtil::GetCurrentThread(jvmtiEnv* env ATTRIBUTE_UNUSED, jthread* thread_ptr) {
art::Thread* self = art::Thread::Current();
art::ScopedObjectAccess soa(self);
jthread thread_peer;
if (self->IsStillStarting()) {
thread_peer = nullptr;
} else {
thread_peer = soa.AddLocalReference<jthread>(self->GetPeer());
}
*thread_ptr = thread_peer;
return ERR(NONE);
}
// Get the native thread. The spec says a null object denotes the current thread.
bool ThreadUtil::GetNativeThread(jthread thread,
const art::ScopedObjectAccessAlreadyRunnable& soa,
/*out*/ art::Thread** thr,
/*out*/ jvmtiError* err) {
if (thread == nullptr) {
*thr = art::Thread::Current();
return true;
} else if (!soa.Env()->IsInstanceOf(thread, art::WellKnownClasses::java_lang_Thread)) {
*err = ERR(INVALID_THREAD);
return false;
} else {
*thr = art::Thread::FromManagedThread(soa, thread);
return true;
}
}
bool ThreadUtil::GetAliveNativeThread(jthread thread,
const art::ScopedObjectAccessAlreadyRunnable& soa,
/*out*/ art::Thread** thr,
/*out*/ jvmtiError* err) {
if (!GetNativeThread(thread, soa, thr, err)) {
return false;
} else if (*thr == nullptr || (*thr)->GetState() == art::ThreadState::kTerminated) {
*err = ERR(THREAD_NOT_ALIVE);
return false;
} else {
return true;
}
}
jvmtiError ThreadUtil::GetThreadInfo(jvmtiEnv* env, jthread thread, jvmtiThreadInfo* info_ptr) {
if (info_ptr == nullptr) {
return ERR(NULL_POINTER);
}
if (!PhaseUtil::IsLivePhase()) {
return JVMTI_ERROR_WRONG_PHASE;
}
art::Thread* self = art::Thread::Current();
art::ScopedObjectAccess soa(self);
art::MutexLock mu(self, *art::Locks::thread_list_lock_);
art::Thread* target;
jvmtiError err = ERR(INTERNAL);
if (!GetNativeThread(thread, soa, &target, &err)) {
return err;
}
JvmtiUniquePtr<char[]> name_uptr;
if (target != nullptr) {
// Have a native thread object, this thread is alive.
std::string name;
target->GetThreadName(name);
jvmtiError name_result;
name_uptr = CopyString(env, name.c_str(), &name_result);
if (name_uptr == nullptr) {
return name_result;
}
info_ptr->name = name_uptr.get();
info_ptr->priority = target->GetNativePriority();
info_ptr->is_daemon = target->IsDaemon();
art::ObjPtr<art::mirror::Object> peer = target->GetPeerFromOtherThread();
// ThreadGroup.
if (peer != nullptr) {
art::ArtField* f = art::jni::DecodeArtField(art::WellKnownClasses::java_lang_Thread_group);
CHECK(f != nullptr);
art::ObjPtr<art::mirror::Object> group = f->GetObject(peer);
info_ptr->thread_group = group == nullptr
? nullptr
: soa.AddLocalReference<jthreadGroup>(group);
} else {
info_ptr->thread_group = nullptr;
}
// Context classloader.
DCHECK(context_class_loader_ != nullptr);
art::ObjPtr<art::mirror::Object> ccl = peer != nullptr
? context_class_loader_->GetObject(peer)
: nullptr;
info_ptr->context_class_loader = ccl == nullptr
? nullptr
: soa.AddLocalReference<jobject>(ccl);
} else {
// Only the peer. This thread has either not been started, or is dead. Read things from
// the Java side.
art::ObjPtr<art::mirror::Object> peer = soa.Decode<art::mirror::Object>(thread);
// Name.
{
art::ArtField* f = art::jni::DecodeArtField(art::WellKnownClasses::java_lang_Thread_name);
CHECK(f != nullptr);
art::ObjPtr<art::mirror::Object> name = f->GetObject(peer);
std::string name_cpp;
const char* name_cstr;
if (name != nullptr) {
name_cpp = name->AsString()->ToModifiedUtf8();
name_cstr = name_cpp.c_str();
} else {
name_cstr = "";
}
jvmtiError name_result;
name_uptr = CopyString(env, name_cstr, &name_result);
if (name_uptr == nullptr) {
return name_result;
}
info_ptr->name = name_uptr.get();
}
// Priority.
{
art::ArtField* f = art::jni::DecodeArtField(art::WellKnownClasses::java_lang_Thread_priority);
CHECK(f != nullptr);
info_ptr->priority = static_cast<jint>(f->GetInt(peer));
}
// Daemon.
{
art::ArtField* f = art::jni::DecodeArtField(art::WellKnownClasses::java_lang_Thread_daemon);
CHECK(f != nullptr);
info_ptr->is_daemon = f->GetBoolean(peer) == 0 ? JNI_FALSE : JNI_TRUE;
}
// ThreadGroup.
{
art::ArtField* f = art::jni::DecodeArtField(art::WellKnownClasses::java_lang_Thread_group);
CHECK(f != nullptr);
art::ObjPtr<art::mirror::Object> group = f->GetObject(peer);
info_ptr->thread_group = group == nullptr
? nullptr
: soa.AddLocalReference<jthreadGroup>(group);
}
// Context classloader.
DCHECK(context_class_loader_ != nullptr);
art::ObjPtr<art::mirror::Object> ccl = peer != nullptr
? context_class_loader_->GetObject(peer)
: nullptr;
info_ptr->context_class_loader = ccl == nullptr
? nullptr
: soa.AddLocalReference<jobject>(ccl);
}
name_uptr.release();
return ERR(NONE);
}
struct InternalThreadState {
art::Thread* native_thread;
art::ThreadState art_state;
int thread_user_code_suspend_count;
};
// Return the thread's (or current thread, if null) thread state.
static InternalThreadState GetNativeThreadState(art::Thread* target)
REQUIRES_SHARED(art::Locks::mutator_lock_)
REQUIRES(art::Locks::thread_list_lock_, art::Locks::user_code_suspension_lock_) {
InternalThreadState thread_state = {};
art::MutexLock tscl_mu(art::Thread::Current(), *art::Locks::thread_suspend_count_lock_);
thread_state.native_thread = target;
if (target == nullptr || target->IsStillStarting()) {
thread_state.art_state = art::ThreadState::kStarting;
thread_state.thread_user_code_suspend_count = 0;
} else {
thread_state.art_state = target->GetState();
thread_state.thread_user_code_suspend_count = target->GetUserCodeSuspendCount();
}
return thread_state;
}
static jint GetJvmtiThreadStateFromInternal(const InternalThreadState& state) {
art::ThreadState internal_thread_state = state.art_state;
jint jvmti_state = JVMTI_THREAD_STATE_ALIVE;
if (state.thread_user_code_suspend_count != 0) {
// Suspended can be set with any thread state so check it here. Even if the thread isn't in
// kSuspended state it will move to that once it hits a checkpoint so we can still set this.
jvmti_state |= JVMTI_THREAD_STATE_SUSPENDED;
// Note: We do not have data about the previous state. Otherwise we should load the previous
// state here.
}
if (state.native_thread->IsInterrupted()) {
// Interrupted can be set with any thread state so check it here.
jvmti_state |= JVMTI_THREAD_STATE_INTERRUPTED;
}
// Enumerate all the thread states and fill in the other bits. This contains the results of
// following the decision tree in the JVMTI spec GetThreadState documentation.
switch (internal_thread_state) {
case art::ThreadState::kRunnable:
case art::ThreadState::kWaitingWeakGcRootRead:
case art::ThreadState::kSuspended:
// These are all simply runnable.
// kRunnable is self-explanatory.
// kWaitingWeakGcRootRead is set during some operations with strings due to the intern-table
// so we want to keep it marked as runnable.
// kSuspended we don't mark since if we don't have a user_code_suspend_count then it is done
// by the GC and not a JVMTI suspension, which means it cannot be removed by ResumeThread.
jvmti_state |= JVMTI_THREAD_STATE_RUNNABLE;
break;
case art::ThreadState::kNative:
// kNative means native and runnable. Technically THREAD_STATE_IN_NATIVE can be set with any
// state but we don't have the information to know if it should be present for any but the
// kNative state.
jvmti_state |= (JVMTI_THREAD_STATE_IN_NATIVE |
JVMTI_THREAD_STATE_RUNNABLE);
break;
case art::ThreadState::kBlocked:
// Blocked is one of the top level states so it sits alone.
jvmti_state |= JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER;
break;
case art::ThreadState::kWaiting:
// Object.wait() so waiting, indefinitely, in object.wait.
jvmti_state |= (JVMTI_THREAD_STATE_WAITING |
JVMTI_THREAD_STATE_WAITING_INDEFINITELY |
JVMTI_THREAD_STATE_IN_OBJECT_WAIT);
break;
case art::ThreadState::kTimedWaiting:
// Object.wait(long) so waiting, with timeout, in object.wait.
jvmti_state |= (JVMTI_THREAD_STATE_WAITING |
JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT |
JVMTI_THREAD_STATE_IN_OBJECT_WAIT);
break;
case art::ThreadState::kSleeping:
// In object.sleep. This is a timed wait caused by sleep.
jvmti_state |= (JVMTI_THREAD_STATE_WAITING |
JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT |
JVMTI_THREAD_STATE_SLEEPING);
break;
// TODO We might want to print warnings if we have the debugger running while JVMTI agents are
// attached.
case art::ThreadState::kWaitingForDebuggerSend:
case art::ThreadState::kWaitingForDebuggerToAttach:
case art::ThreadState::kWaitingInMainDebuggerLoop:
case art::ThreadState::kWaitingForDebuggerSuspension:
case art::ThreadState::kWaitingForLockInflation:
case art::ThreadState::kWaitingForTaskProcessor:
case art::ThreadState::kWaitingForGcToComplete:
case art::ThreadState::kWaitingForCheckPointsToRun:
case art::ThreadState::kWaitingPerformingGc:
case art::ThreadState::kWaitingForJniOnLoad:
case art::ThreadState::kWaitingInMainSignalCatcherLoop:
case art::ThreadState::kWaitingForSignalCatcherOutput:
case art::ThreadState::kWaitingForDeoptimization:
case art::ThreadState::kWaitingForMethodTracingStart:
case art::ThreadState::kWaitingForVisitObjects:
case art::ThreadState::kWaitingForGetObjectsAllocated:
case art::ThreadState::kWaitingForGcThreadFlip:
// All of these are causing the thread to wait for an indeterminate amount of time but isn't
// caused by sleep, park, or object#wait.
jvmti_state |= (JVMTI_THREAD_STATE_WAITING |
JVMTI_THREAD_STATE_WAITING_INDEFINITELY);
break;
case art::ThreadState::kStarting:
case art::ThreadState::kTerminated:
// We only call this if we are alive so we shouldn't see either of these states.
LOG(FATAL) << "Should not be in state " << internal_thread_state;
UNREACHABLE();
}
// TODO: PARKED. We'll have to inspect the stack.
return jvmti_state;
}
static jint GetJavaStateFromInternal(const InternalThreadState& state) {
switch (state.art_state) {
case art::ThreadState::kTerminated:
return JVMTI_JAVA_LANG_THREAD_STATE_TERMINATED;
case art::ThreadState::kRunnable:
case art::ThreadState::kNative:
case art::ThreadState::kWaitingWeakGcRootRead:
case art::ThreadState::kSuspended:
return JVMTI_JAVA_LANG_THREAD_STATE_RUNNABLE;
case art::ThreadState::kTimedWaiting:
case art::ThreadState::kSleeping:
return JVMTI_JAVA_LANG_THREAD_STATE_TIMED_WAITING;
case art::ThreadState::kBlocked:
return JVMTI_JAVA_LANG_THREAD_STATE_BLOCKED;
case art::ThreadState::kStarting:
return JVMTI_JAVA_LANG_THREAD_STATE_NEW;
case art::ThreadState::kWaiting:
case art::ThreadState::kWaitingForTaskProcessor:
case art::ThreadState::kWaitingForLockInflation:
case art::ThreadState::kWaitingForGcToComplete:
case art::ThreadState::kWaitingPerformingGc:
case art::ThreadState::kWaitingForCheckPointsToRun:
case art::ThreadState::kWaitingForDebuggerSend:
case art::ThreadState::kWaitingForDebuggerToAttach:
case art::ThreadState::kWaitingInMainDebuggerLoop:
case art::ThreadState::kWaitingForDebuggerSuspension:
case art::ThreadState::kWaitingForDeoptimization:
case art::ThreadState::kWaitingForGetObjectsAllocated:
case art::ThreadState::kWaitingForJniOnLoad:
case art::ThreadState::kWaitingForSignalCatcherOutput:
case art::ThreadState::kWaitingInMainSignalCatcherLoop:
case art::ThreadState::kWaitingForMethodTracingStart:
case art::ThreadState::kWaitingForVisitObjects:
case art::ThreadState::kWaitingForGcThreadFlip:
return JVMTI_JAVA_LANG_THREAD_STATE_WAITING;
}
LOG(FATAL) << "Unreachable";
UNREACHABLE();
}
// Suspends the current thread if it has any suspend requests on it.
void ThreadUtil::SuspendCheck(art::Thread* self) {
art::ScopedObjectAccess soa(self);
// Really this is only needed if we are in FastJNI and actually have the mutator_lock_ already.
self->FullSuspendCheck();
}
bool ThreadUtil::WouldSuspendForUserCodeLocked(art::Thread* self) {
DCHECK(self == art::Thread::Current());
art::MutexLock tscl_mu(self, *art::Locks::thread_suspend_count_lock_);
return self->GetUserCodeSuspendCount() != 0;
}
bool ThreadUtil::WouldSuspendForUserCode(art::Thread* self) {
DCHECK(self == art::Thread::Current());
art::MutexLock ucsl_mu(self, *art::Locks::user_code_suspension_lock_);
return WouldSuspendForUserCodeLocked(self);
}
jvmtiError ThreadUtil::GetThreadState(jvmtiEnv* env ATTRIBUTE_UNUSED,
jthread thread,
jint* thread_state_ptr) {
if (thread_state_ptr == nullptr) {
return ERR(NULL_POINTER);
}
art::Thread* self = art::Thread::Current();
InternalThreadState state = {};
// Loop since we need to bail out and try again if we would end up getting suspended while holding
// the user_code_suspension_lock_ due to a SuspendReason::kForUserCode. In this situation we
// release the lock, wait to get resumed and try again.
do {
SuspendCheck(self);
art::MutexLock ucsl_mu(self, *art::Locks::user_code_suspension_lock_);
if (WouldSuspendForUserCodeLocked(self)) {
// Make sure we won't be suspended in the middle of holding the thread_suspend_count_lock_ by
// a user-code suspension. We retry and do another SuspendCheck to clear this.
continue;
}
art::ScopedObjectAccess soa(self);
art::MutexLock tll_mu(self, *art::Locks::thread_list_lock_);
jvmtiError err = ERR(INTERNAL);
art::Thread* target = nullptr;
if (!GetNativeThread(thread, soa, &target, &err)) {
return err;
}
state = GetNativeThreadState(target);
if (state.art_state == art::ThreadState::kStarting) {
break;
}
DCHECK(state.native_thread != nullptr);
// Translate internal thread state to JVMTI and Java state.
jint jvmti_state = GetJvmtiThreadStateFromInternal(state);
// Java state is derived from nativeGetState.
// TODO: Our implementation assigns "runnable" to suspended. As such, we will have slightly
// different mask if a thread got suspended due to user-code. However, this is for
// consistency with the Java view.
jint java_state = GetJavaStateFromInternal(state);
*thread_state_ptr = jvmti_state | java_state;
return ERR(NONE);
} while (true);
DCHECK_EQ(state.art_state, art::ThreadState::kStarting);
if (thread == nullptr) {
// No native thread, and no Java thread? We must be starting up. Report as wrong phase.
return ERR(WRONG_PHASE);
}
art::ScopedObjectAccess soa(self);
art::StackHandleScope<1> hs(self);
// Need to read the Java "started" field to know whether this is starting or terminated.
art::Handle<art::mirror::Object> peer(hs.NewHandle(soa.Decode<art::mirror::Object>(thread)));
art::ObjPtr<art::mirror::Class> thread_klass =
soa.Decode<art::mirror::Class>(art::WellKnownClasses::java_lang_Thread);
if (!thread_klass->IsAssignableFrom(peer->GetClass())) {
return ERR(INVALID_THREAD);
}
art::ArtField* started_field = thread_klass->FindDeclaredInstanceField("started", "Z");
CHECK(started_field != nullptr);
bool started = started_field->GetBoolean(peer.Get()) != 0;
constexpr jint kStartedState = JVMTI_JAVA_LANG_THREAD_STATE_NEW;
constexpr jint kTerminatedState = JVMTI_THREAD_STATE_TERMINATED |
JVMTI_JAVA_LANG_THREAD_STATE_TERMINATED;
*thread_state_ptr = started ? kTerminatedState : kStartedState;
return ERR(NONE);
}
jvmtiError ThreadUtil::GetAllThreads(jvmtiEnv* env,
jint* threads_count_ptr,
jthread** threads_ptr) {
if (threads_count_ptr == nullptr || threads_ptr == nullptr) {
return ERR(NULL_POINTER);
}
art::Thread* current = art::Thread::Current();
art::ScopedObjectAccess soa(current);
art::MutexLock mu(current, *art::Locks::thread_list_lock_);
std::list<art::Thread*> thread_list = art::Runtime::Current()->GetThreadList()->GetList();
std::vector<art::ObjPtr<art::mirror::Object>> peers;
for (art::Thread* thread : thread_list) {
// Skip threads that are still starting.
if (thread->IsStillStarting()) {
continue;
}
art::ObjPtr<art::mirror::Object> peer = thread->GetPeerFromOtherThread();
if (peer != nullptr) {
peers.push_back(peer);
}
}
if (peers.empty()) {
*threads_count_ptr = 0;
*threads_ptr = nullptr;
} else {
unsigned char* data;
jvmtiError data_result = env->Allocate(peers.size() * sizeof(jthread), &data);
if (data_result != ERR(NONE)) {
return data_result;
}
jthread* threads = reinterpret_cast<jthread*>(data);
for (size_t i = 0; i != peers.size(); ++i) {
threads[i] = soa.AddLocalReference<jthread>(peers[i]);
}
*threads_count_ptr = static_cast<jint>(peers.size());
*threads_ptr = threads;
}
return ERR(NONE);
}
// The struct that we store in the art::Thread::custom_tls_ that maps the jvmtiEnvs to the data
// stored with that thread. This is needed since different jvmtiEnvs are not supposed to share TLS
// data but we only have a single slot in Thread objects to store data.
struct JvmtiGlobalTLSData {
std::unordered_map<jvmtiEnv*, const void*> data GUARDED_BY(art::Locks::thread_list_lock_);
};
static void RemoveTLSData(art::Thread* target, void* ctx) REQUIRES(art::Locks::thread_list_lock_) {
jvmtiEnv* env = reinterpret_cast<jvmtiEnv*>(ctx);
art::Locks::thread_list_lock_->AssertHeld(art::Thread::Current());
JvmtiGlobalTLSData* global_tls = reinterpret_cast<JvmtiGlobalTLSData*>(target->GetCustomTLS());
if (global_tls != nullptr) {
global_tls->data.erase(env);
}
}
void ThreadUtil::RemoveEnvironment(jvmtiEnv* env) {
art::Thread* self = art::Thread::Current();
art::MutexLock mu(self, *art::Locks::thread_list_lock_);
art::ThreadList* list = art::Runtime::Current()->GetThreadList();
list->ForEach(RemoveTLSData, env);
}
jvmtiError ThreadUtil::SetThreadLocalStorage(jvmtiEnv* env, jthread thread, const void* data) {
art::Thread* self = art::Thread::Current();
art::ScopedObjectAccess soa(self);
art::MutexLock mu(self, *art::Locks::thread_list_lock_);
art::Thread* target = nullptr;
jvmtiError err = ERR(INTERNAL);
if (!GetAliveNativeThread(thread, soa, &target, &err)) {
return err;
}
JvmtiGlobalTLSData* global_tls = reinterpret_cast<JvmtiGlobalTLSData*>(target->GetCustomTLS());
if (global_tls == nullptr) {
target->SetCustomTLS(new JvmtiGlobalTLSData);
global_tls = reinterpret_cast<JvmtiGlobalTLSData*>(target->GetCustomTLS());
}
global_tls->data[env] = data;
return ERR(NONE);
}
jvmtiError ThreadUtil::GetThreadLocalStorage(jvmtiEnv* env,
jthread thread,
void** data_ptr) {
if (data_ptr == nullptr) {
return ERR(NULL_POINTER);
}
art::Thread* self = art::Thread::Current();
art::ScopedObjectAccess soa(self);
art::MutexLock mu(self, *art::Locks::thread_list_lock_);
art::Thread* target = nullptr;
jvmtiError err = ERR(INTERNAL);
if (!GetAliveNativeThread(thread, soa, &target, &err)) {
return err;
}
JvmtiGlobalTLSData* global_tls = reinterpret_cast<JvmtiGlobalTLSData*>(target->GetCustomTLS());
if (global_tls == nullptr) {
*data_ptr = nullptr;
return OK;
}
auto it = global_tls->data.find(env);
if (it != global_tls->data.end()) {
*data_ptr = const_cast<void*>(it->second);
} else {
*data_ptr = nullptr;
}
return ERR(NONE);
}
struct AgentData {
const void* arg;
jvmtiStartFunction proc;
jthread thread;
JavaVM* java_vm;
jvmtiEnv* jvmti_env;
jint priority;
std::string name;
};
static void* AgentCallback(void* arg) {
std::unique_ptr<AgentData> data(reinterpret_cast<AgentData*>(arg));
CHECK(data->thread != nullptr);
// We already have a peer. So call our special Attach function.
art::Thread* self = art::Thread::Attach(data->name.c_str(), true, data->thread);
CHECK(self != nullptr) << "threads_being_born_ should have ensured thread could be attached.";
// The name in Attach() is only for logging. Set the thread name. This is important so
// that the thread is no longer seen as starting up.
{
art::ScopedObjectAccess soa(self);
self->SetThreadName(data->name.c_str());
}
// Release the peer.
JNIEnv* env = self->GetJniEnv();
env->DeleteGlobalRef(data->thread);
data->thread = nullptr;
{
// The StartThreadBirth was called in the parent thread. We let the runtime know we are up
// before going into the provided code.
art::MutexLock mu(art::Thread::Current(), *art::Locks::runtime_shutdown_lock_);
art::Runtime::Current()->EndThreadBirth();
}
// Run the agent code.
data->proc(data->jvmti_env, env, const_cast<void*>(data->arg));
// Detach the thread.
int detach_result = data->java_vm->DetachCurrentThread();
CHECK_EQ(detach_result, 0);
return nullptr;
}
jvmtiError ThreadUtil::RunAgentThread(jvmtiEnv* jvmti_env,
jthread thread,
jvmtiStartFunction proc,
const void* arg,
jint priority) {
if (!PhaseUtil::IsLivePhase()) {
return ERR(WRONG_PHASE);
}
if (priority < JVMTI_THREAD_MIN_PRIORITY || priority > JVMTI_THREAD_MAX_PRIORITY) {
return ERR(INVALID_PRIORITY);
}
JNIEnv* env = art::Thread::Current()->GetJniEnv();
if (thread == nullptr || !env->IsInstanceOf(thread, art::WellKnownClasses::java_lang_Thread)) {
return ERR(INVALID_THREAD);
}
if (proc == nullptr) {
return ERR(NULL_POINTER);
}
{
art::Runtime* runtime = art::Runtime::Current();
art::MutexLock mu(art::Thread::Current(), *art::Locks::runtime_shutdown_lock_);
if (runtime->IsShuttingDownLocked()) {
// The runtime is shutting down so we cannot create new threads.
// TODO It's not fully clear from the spec what we should do here. We aren't yet in
// JVMTI_PHASE_DEAD so we cannot return ERR(WRONG_PHASE) but creating new threads is now
// impossible. Existing agents don't seem to generally do anything with this return value so
// it doesn't matter too much. We could do something like sending a fake ThreadStart event
// even though code is never actually run.
return ERR(INTERNAL);
}
runtime->StartThreadBirth();
}
std::unique_ptr<AgentData> data(new AgentData);
data->arg = arg;
data->proc = proc;
// We need a global ref for Java objects, as local refs will be invalid.
data->thread = env->NewGlobalRef(thread);
data->java_vm = art::Runtime::Current()->GetJavaVM();
data->jvmti_env = jvmti_env;
data->priority = priority;
ScopedLocalRef<jstring> s(
env,
reinterpret_cast<jstring>(
env->GetObjectField(thread, art::WellKnownClasses::java_lang_Thread_name)));
if (s == nullptr) {
data->name = "JVMTI Agent Thread";
} else {
ScopedUtfChars name(env, s.get());
data->name = name.c_str();
}
pthread_t pthread;
int pthread_create_result = pthread_create(&pthread,
nullptr,
&AgentCallback,
reinterpret_cast<void*>(data.get()));
if (pthread_create_result != 0) {
// If the create succeeded the other thread will call EndThreadBirth.
art::Runtime* runtime = art::Runtime::Current();
art::MutexLock mu(art::Thread::Current(), *art::Locks::runtime_shutdown_lock_);
runtime->EndThreadBirth();
return ERR(INTERNAL);
}
data.release();
return ERR(NONE);
}
jvmtiError ThreadUtil::SuspendOther(art::Thread* self,
jthread target_jthread) {
// Loop since we need to bail out and try again if we would end up getting suspended while holding
// the user_code_suspension_lock_ due to a SuspendReason::kForUserCode. In this situation we
// release the lock, wait to get resumed and try again.
do {
// Suspend ourself if we have any outstanding suspends. This is so we won't suspend due to
// another SuspendThread in the middle of suspending something else potentially causing a
// deadlock. We need to do this in the loop because if we ended up back here then we had
// outstanding SuspendReason::kForUserCode suspensions and we should wait for them to be cleared
// before continuing.
SuspendCheck(self);
art::MutexLock mu(self, *art::Locks::user_code_suspension_lock_);
if (WouldSuspendForUserCodeLocked(self)) {
// Make sure we won't be suspended in the middle of holding the thread_suspend_count_lock_ by
// a user-code suspension. We retry and do another SuspendCheck to clear this.
continue;
}
// We are not going to be suspended by user code from now on.
{
art::ScopedObjectAccess soa(self);
art::MutexLock thread_list_mu(self, *art::Locks::thread_list_lock_);
art::Thread* target = nullptr;
jvmtiError err = ERR(INTERNAL);
if (!GetAliveNativeThread(target_jthread, soa, &target, &err)) {
return err;
}
art::ThreadState state = target->GetState();
if (state == art::ThreadState::kStarting || target->IsStillStarting()) {
return ERR(THREAD_NOT_ALIVE);
} else {
art::MutexLock thread_suspend_count_mu(self, *art::Locks::thread_suspend_count_lock_);
if (target->GetUserCodeSuspendCount() != 0) {
return ERR(THREAD_SUSPENDED);
}
}
}
bool timeout = true;
art::Thread* ret_target = art::Runtime::Current()->GetThreadList()->SuspendThreadByPeer(
target_jthread,
/* request_suspension */ true,
art::SuspendReason::kForUserCode,
&timeout);
if (ret_target == nullptr && !timeout) {
// TODO It would be good to get more information about why exactly the thread failed to
// suspend.
return ERR(INTERNAL);
} else if (!timeout) {
// we didn't time out and got a result.
return OK;
}
// We timed out. Just go around and try again.
} while (true);
UNREACHABLE();
}
jvmtiError ThreadUtil::SuspendSelf(art::Thread* self) {
CHECK(self == art::Thread::Current());
{
art::MutexLock mu(self, *art::Locks::user_code_suspension_lock_);
art::MutexLock thread_list_mu(self, *art::Locks::thread_suspend_count_lock_);
if (self->GetUserCodeSuspendCount() != 0) {
// This can only happen if we race with another thread to suspend 'self' and we lose.
return ERR(THREAD_SUSPENDED);
}
// We shouldn't be able to fail this.
if (!self->ModifySuspendCount(self, +1, nullptr, art::SuspendReason::kForUserCode)) {
// TODO More specific error would be nice.
return ERR(INTERNAL);
}
}
// Once we have requested the suspend we actually go to sleep. We need to do this after releasing
// the suspend_lock to make sure we can be woken up. This call gains the mutator lock causing us
// to go to sleep until we are resumed.
SuspendCheck(self);
return OK;
}
jvmtiError ThreadUtil::SuspendThread(jvmtiEnv* env ATTRIBUTE_UNUSED, jthread thread) {
art::Thread* self = art::Thread::Current();
bool target_is_self = false;
{
art::ScopedObjectAccess soa(self);
art::MutexLock mu(self, *art::Locks::thread_list_lock_);
art::Thread* target = nullptr;
jvmtiError err = ERR(INTERNAL);
if (!GetAliveNativeThread(thread, soa, &target, &err)) {
return err;
} else if (target == self) {
target_is_self = true;
}
}
if (target_is_self) {
return SuspendSelf(self);
} else {
return SuspendOther(self, thread);
}
}
jvmtiError ThreadUtil::ResumeThread(jvmtiEnv* env ATTRIBUTE_UNUSED,
jthread thread) {
if (thread == nullptr) {
return ERR(NULL_POINTER);
}
art::Thread* self = art::Thread::Current();
art::Thread* target;
// Retry until we know we won't get suspended by user code while resuming something.
do {
SuspendCheck(self);
art::MutexLock ucsl_mu(self, *art::Locks::user_code_suspension_lock_);
if (WouldSuspendForUserCodeLocked(self)) {
// Make sure we won't be suspended in the middle of holding the thread_suspend_count_lock_ by
// a user-code suspension. We retry and do another SuspendCheck to clear this.
continue;
}
// From now on we know we cannot get suspended by user-code.
{
// NB This does a SuspendCheck (during thread state change) so we need to make sure we don't
// have the 'suspend_lock' locked here.
art::ScopedObjectAccess soa(self);
art::MutexLock tll_mu(self, *art::Locks::thread_list_lock_);
jvmtiError err = ERR(INTERNAL);
if (!GetAliveNativeThread(thread, soa, &target, &err)) {
return err;
} else if (target == self) {
// We would have paused until we aren't suspended anymore due to the ScopedObjectAccess so
// we can just return THREAD_NOT_SUSPENDED. Unfortunately we cannot do any real DCHECKs
// about current state since it's all concurrent.
return ERR(THREAD_NOT_SUSPENDED);
}
// The JVMTI spec requires us to return THREAD_NOT_SUSPENDED if it is alive but we really
// cannot tell why resume failed.
{
art::MutexLock thread_suspend_count_mu(self, *art::Locks::thread_suspend_count_lock_);
if (target->GetUserCodeSuspendCount() == 0) {
return ERR(THREAD_NOT_SUSPENDED);
}
}
}
// It is okay that we don't have a thread_list_lock here since we know that the thread cannot
// die since it is currently held suspended by a SuspendReason::kForUserCode suspend.
DCHECK(target != self);
if (!art::Runtime::Current()->GetThreadList()->Resume(target,
art::SuspendReason::kForUserCode)) {
// TODO Give a better error.
// This is most likely THREAD_NOT_SUSPENDED but we cannot really be sure.
return ERR(INTERNAL);
} else {
return OK;
}
} while (true);
}
static bool IsCurrentThread(jthread thr) {
if (thr == nullptr) {
return true;
}
art::Thread* self = art::Thread::Current();
art::ScopedObjectAccess soa(self);
art::MutexLock mu(self, *art::Locks::thread_list_lock_);
art::Thread* target = nullptr;
jvmtiError err_unused = ERR(INTERNAL);
if (ThreadUtil::GetNativeThread(thr, soa, &target, &err_unused)) {
return target == self;
} else {
return false;
}
}
// Suspends all the threads in the list at the same time. Getting this behavior is a little tricky
// since we can have threads in the list multiple times. This generally doesn't matter unless the
// current thread is present multiple times. In that case we need to suspend only once and either
// return the same error code in all the other slots if it failed or return ERR(THREAD_SUSPENDED) if
// it didn't. We also want to handle the current thread last to make the behavior of the code
// simpler to understand.
jvmtiError ThreadUtil::SuspendThreadList(jvmtiEnv* env,
jint request_count,
const jthread* threads,
jvmtiError* results) {
if (request_count == 0) {
return ERR(ILLEGAL_ARGUMENT);
} else if (results == nullptr || threads == nullptr) {
return ERR(NULL_POINTER);
}
// This is the list of the indexes in 'threads' and 'results' that correspond to the currently
// running thread. These indexes we need to handle specially since we need to only actually
// suspend a single time.
std::vector<jint> current_thread_indexes;
for (jint i = 0; i < request_count; i++) {
if (IsCurrentThread(threads[i])) {
current_thread_indexes.push_back(i);
} else {
results[i] = env->SuspendThread(threads[i]);
}
}
if (!current_thread_indexes.empty()) {
jint first_current_thread_index = current_thread_indexes[0];
// Suspend self.
jvmtiError res = env->SuspendThread(threads[first_current_thread_index]);
results[first_current_thread_index] = res;
// Fill in the rest of the error values as appropriate.
jvmtiError other_results = (res != OK) ? res : ERR(THREAD_SUSPENDED);
for (auto it = ++current_thread_indexes.begin(); it != current_thread_indexes.end(); ++it) {
results[*it] = other_results;
}
}
return OK;
}
jvmtiError ThreadUtil::ResumeThreadList(jvmtiEnv* env,
jint request_count,
const jthread* threads,
jvmtiError* results) {
if (request_count == 0) {
return ERR(ILLEGAL_ARGUMENT);
} else if (results == nullptr || threads == nullptr) {
return ERR(NULL_POINTER);
}
for (jint i = 0; i < request_count; i++) {
results[i] = env->ResumeThread(threads[i]);
}
return OK;
}
jvmtiError ThreadUtil::StopThread(jvmtiEnv* env ATTRIBUTE_UNUSED,
jthread thread,
jobject exception) {
art::Thread* self = art::Thread::Current();
art::ScopedObjectAccess soa(self);
art::StackHandleScope<1> hs(self);
if (exception == nullptr) {
return ERR(INVALID_OBJECT);
}
art::ObjPtr<art::mirror::Object> obj(soa.Decode<art::mirror::Object>(exception));
if (!obj->GetClass()->IsThrowableClass()) {
return ERR(INVALID_OBJECT);
}
art::Handle<art::mirror::Throwable> exc(hs.NewHandle(obj->AsThrowable()));
art::Locks::thread_list_lock_->ExclusiveLock(self);
art::Thread* target = nullptr;
jvmtiError err = ERR(INTERNAL);
if (!GetAliveNativeThread(thread, soa, &target, &err)) {
art::Locks::thread_list_lock_->ExclusiveUnlock(self);
return err;
} else if (target->GetState() == art::ThreadState::kStarting || target->IsStillStarting()) {
art::Locks::thread_list_lock_->ExclusiveUnlock(self);
return ERR(THREAD_NOT_ALIVE);
}
struct StopThreadClosure : public art::Closure {
public:
explicit StopThreadClosure(art::Handle<art::mirror::Throwable> except) : exception_(except) { }
void Run(art::Thread* me) REQUIRES_SHARED(art::Locks::mutator_lock_) {
// Make sure the thread is prepared to notice the exception.
art::Runtime::Current()->GetInstrumentation()->InstrumentThreadStack(me);
me->SetAsyncException(exception_.Get());
// Wake up the thread if it is sleeping.
me->Notify();
}
private:
art::Handle<art::mirror::Throwable> exception_;
};
StopThreadClosure c(exc);
// RequestSynchronousCheckpoint releases the thread_list_lock_ as a part of its execution.
if (target->RequestSynchronousCheckpoint(&c)) {
return OK;
} else {
// Something went wrong, probably the thread died.
return ERR(THREAD_NOT_ALIVE);
}
}
jvmtiError ThreadUtil::InterruptThread(jvmtiEnv* env ATTRIBUTE_UNUSED, jthread thread) {
art::Thread* self = art::Thread::Current();
art::ScopedObjectAccess soa(self);
art::MutexLock tll_mu(self, *art::Locks::thread_list_lock_);
art::Thread* target = nullptr;
jvmtiError err = ERR(INTERNAL);
if (!GetAliveNativeThread(thread, soa, &target, &err)) {
return err;
} else if (target->GetState() == art::ThreadState::kStarting || target->IsStillStarting()) {
return ERR(THREAD_NOT_ALIVE);
}
target->Interrupt(self);
return OK;
}
} // namespace openjdkjvmti