/* * Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2021, Azul Systems, Inc. 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. * * 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. *
*/
// Creates the initial Thread, and sets it to running. staticvoid create_initial_thread(Handle thread_group, JavaThread* thread,
TRAPS) {
InstanceKlass* ik = vmClasses::Thread_klass();
assert(ik->is_initialized(), "must be");
instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
// Cannot use JavaCalls::construct_new_instance because the java.lang.Thread // constructor calls Thread.current(), which must be set here for the // initial thread.
java_lang_Thread::set_thread(thread_oop(), thread);
thread->set_threadOopHandles(thread_oop());
// Set thread status to running since main thread has // been started and running.
java_lang_Thread::set_thread_status(thread_oop(),
JavaThreadStatus::RUNNABLE);
}
// Extract version and vendor specific information from // java.lang.VersionProps fields. // Returned char* is allocated in the thread's resource area // so must be copied for permanency. staticconstchar* get_java_version_info(InstanceKlass* ik,
Symbol* field_name) {
fieldDescriptor fd; bool found = ik != NULL &&
ik->find_local_field(field_name,
vmSymbols::string_signature(), &fd); if (found) {
oop name_oop = ik->java_mirror()->obj_field(fd.offset()); if (name_oop == NULL) { return NULL;
} constchar* name = java_lang_String::as_utf8_string(name_oop); return name;
} else { return NULL;
}
}
// ======= Threads ========
// The Threads class links together all active threads, and provides // operations over all threads. It is protected by the Threads_lock, // which is also used in other global contexts like safepointing. // ThreadsListHandles are used to safely perform operations on one // or more threads without the risk of the thread exiting during the // operation. // // Note: The Threads_lock is currently more widely used than we // would like. We are actively migrating Threads_lock uses to other // mechanisms in order to reduce Threads_lock contention.
int Threads::_number_of_threads = 0; int Threads::_number_of_non_daemon_threads = 0; int Threads::_return_code = 0;
uintx Threads::_thread_claim_token = 1; // Never zero.
// General purpose hook into Java code, run once when the VM is initialized. // The Java library method itself may be changed independently from the VM. staticvoid call_postVMInitHook(TRAPS) {
Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD); if (klass != NULL) {
JavaValue result(T_VOID);
JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
vmSymbols::void_method_signature(),
CHECK);
}
}
// All NonJavaThreads (i.e., every non-JavaThread in the system). void Threads::non_java_threads_do(ThreadClosure* tc) {
NoSafepointVerifier nsv; for (NonJavaThread::Iterator njti; !njti.end(); njti.step()) {
tc->do_thread(njti.current());
}
}
// All JavaThreads #define ALL_JAVA_THREADS(X) \ for (JavaThread* X : *ThreadsSMRSupport::get_java_thread_list())
// All JavaThreads void Threads::java_threads_do(ThreadClosure* tc) {
assert_locked_or_safepoint(Threads_lock); // ALL_JAVA_THREADS iterates through all JavaThreads.
ALL_JAVA_THREADS(p) {
tc->do_thread(p);
}
}
// All JavaThreads + all non-JavaThreads (i.e., every thread in the system). void Threads::threads_do(ThreadClosure* tc) {
assert_locked_or_safepoint(Threads_lock);
java_threads_do(tc);
non_java_threads_do(tc);
}
// The system initialization in the library has three phases. // // Phase 1: java.lang.System class initialization // java.lang.System is a primordial class loaded and initialized // by the VM early during startup. java.lang.System.<clinit> // only does registerNatives and keeps the rest of the class // initialization work later until thread initialization completes. // // System.initPhase1 initializes the system properties, the static // fields in, out, and err. Set up java signal handlers, OS-specific // system settings, and thread group of the main thread. staticvoid call_initPhase1(TRAPS) {
Klass* klass = vmClasses::System_klass();
JavaValue result(T_VOID);
JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
vmSymbols::void_method_signature(), CHECK);
}
// Phase 2. Module system initialization // This will initialize the module system. Only java.base classes // can be loaded until phase 2 completes. // // Call System.initPhase2 after the compiler initialization and jsr292 // classes get initialized because module initialization runs a lot of java // code, that for performance reasons, should be compiled. Also, this will // enable the startup code to use lambda and other language features in this // phase and onward. // // After phase 2, The VM will begin search classes from -Xbootclasspath/a. staticvoid call_initPhase2(TRAPS) {
TraceTime timer("Initialize module system", TRACETIME_LOG(Info, startuptime));
Klass* klass = vmClasses::System_klass();
JavaValue result(T_INT);
JavaCallArguments args;
args.push_int(DisplayVMOutputToStderr);
args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
vmSymbols::boolean_boolean_int_signature(), &args, CHECK); if (result.get_jint() != JNI_OK) {
vm_exit_during_initialization(); // no message or exception
}
universe_post_module_init();
}
// Phase 3. final setup - set security manager, system class loader and TCCL // // This will instantiate and set the security manager, set the system class // loader as well as the thread context class loader. The security manager // and system class loader may be a custom class loaded from -Xbootclasspath/a, // other modules or the application's classpath. staticvoid call_initPhase3(TRAPS) {
Klass* klass = vmClasses::System_klass();
JavaValue result(T_VOID);
JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
vmSymbols::void_method_signature(), CHECK);
}
// Inject CompactStrings value after the static initializers for String ran.
java_lang_String::set_compact_strings(CompactStrings);
// Initialize java_lang.System (needed before creating the thread)
initialize_class(vmSymbols::java_lang_System(), CHECK); // The VM creates & returns objects of this class. Make sure it's initialized.
initialize_class(vmSymbols::java_lang_Class(), CHECK);
initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
Handle thread_group = create_initial_thread_group(CHECK);
Universe::set_main_thread_group(thread_group());
initialize_class(vmSymbols::java_lang_Thread(), CHECK);
create_initial_thread(thread_group, main_thread, CHECK);
// The VM creates objects of this class.
initialize_class(vmSymbols::java_lang_Module(), CHECK);
#ifdef ASSERT
InstanceKlass *k = vmClasses::UnsafeConstants_klass();
assert(k->is_not_initialized(), "UnsafeConstants should not already be initialized"); #endif
// initialize the hardware-specific constants needed by Unsafe
initialize_class(vmSymbols::jdk_internal_misc_UnsafeConstants(), CHECK);
jdk_internal_misc_UnsafeConstants::set_unsafe_constants();
// The VM preresolves methods to these classes. Make sure that they get initialized
initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
// Phase 1 of the system initialization in the library, java.lang.System class initialization
call_initPhase1(CHECK);
// Get the Java runtime name, version, and vendor info after java.lang.System is initialized. // Some values are actually configure-time constants but some can be set via the jlink tool and // so must be read dynamically. We treat them all the same.
InstanceKlass* ik = SystemDictionary::find_instance_klass(THREAD, vmSymbols::java_lang_VersionProps(),
Handle(), Handle());
{
ResourceMark rm(main_thread);
JDK_Version::set_java_version(get_java_version_info(ik, vmSymbols::java_version_name()));
// Record VM creation timing statistics
TraceVmCreationTime create_vm_timer;
create_vm_timer.start();
// Initialize system properties.
Arguments::init_system_properties();
// So that JDK version can be used as a discriminator when parsing arguments
JDK_Version_init();
// Update/Initialize System properties after JDK version number is known
Arguments::init_version_specific_system_properties();
// Make sure to initialize log configuration *before* parsing arguments
LogConfiguration::initialize(create_vm_timer.begin_time());
// Parse arguments // Note: this internally calls os::init_container_support()
jint parse_result = Arguments::parse(args); if (parse_result != JNI_OK) return parse_result;
// Initialize NMT right after argument parsing to keep the pre-NMT-init window small.
MemTracker::initialize();
os::init_before_ergo();
jint ergo_result = Arguments::apply_ergo(); if (ergo_result != JNI_OK) return ergo_result;
// Final check of all ranges after ergonomics which may change values. if (!JVMFlagLimit::check_all_ranges()) { return JNI_EINVAL;
}
// Final check of all 'AfterErgo' constraints after ergonomics which may change values. bool constraint_result = JVMFlagLimit::check_all_constraints(JVMFlagConstraintPhase::AfterErgo); if (!constraint_result) { return JNI_EINVAL;
}
if (PauseAtStartup) {
os::pause();
}
HOTSPOT_VM_INIT_BEGIN();
// Timing (must come after argument parsing)
TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
// Initialize the os module after parsing the args
jint os_init_2_result = os::init_2(); if (os_init_2_result != JNI_OK) return os_init_2_result;
// Convert -Xrun to -agentlib: if there is no JVM_OnLoad // Must be before create_vm_init_agents() if (Arguments::init_libraries_at_startup()) {
convert_vm_init_libraries_to_agents();
}
// Launch -agentlib/-agentpath and converted -Xrun agents if (Arguments::init_agents_at_startup()) {
create_vm_init_agents();
}
// Initialize Threads state
_number_of_threads = 0;
_number_of_non_daemon_threads = 0;
// Initialize global data structures and create system classes in heap
vm_init_globals();
// Initialize OopStorage for threadObj
JavaThread::_thread_oop_storage = OopStorageSet::create_strong("Thread OopStorage", mtThread);
// Attach the main thread to this os thread
JavaThread* main_thread = new JavaThread();
main_thread->set_thread_state(_thread_in_vm);
main_thread->initialize_thread_current(); // must do this before set_active_handles
main_thread->record_stack_base_and_size();
main_thread->register_thread_stack_with_NMT();
main_thread->set_active_handles(JNIHandleBlock::allocate_block());
MACOS_AARCH64_ONLY(main_thread->init_wx());
if (!main_thread->set_as_starting_thread()) {
vm_shutdown_during_initialization( "Failed necessary internal allocation. Out of swap space");
main_thread->smr_delete();
*canTryAgain = false; // don't let caller call JNI_CreateJavaVM again return JNI_ENOMEM;
}
// Enable guard page *after* os::create_main_thread(), otherwise it would // crash Linux VM, see notes in os_linux.cpp.
main_thread->stack_overflow_state()->create_stack_guard_pages();
if (UseSystemMemoryBarrier) { if (!SystemMemoryBarrier::initialize()) {
vm_shutdown_during_initialization("Failed to initialize the requested system memory barrier synchronization."); return JNI_EINVAL;
}
log_debug(os)("Using experimental system memory barrier synchronization");
}
// Any JVMTI raw monitors entered in onload will transition into // real raw monitor. VM is setup enough here for raw monitor enter.
JvmtiExport::transition_pending_onload_raw_monitors();
// Create the VMThread
{ TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
if (!os::create_thread(vmthread, os::vm_thread)) {
vm_exit_during_initialization("Cannot create VM thread. " "Out of system resources.");
}
// Wait for the VM thread to become ready, and VMThread::run to initialize // Monitors can have spurious returns, must always check another state flag
{
MonitorLocker ml(Notify_lock);
os::start_thread(vmthread); while (!vmthread->is_running()) {
ml.wait();
}
}
}
assert(Universe::is_fully_initialized(), "not initialized"); if (VerifyDuringStartup) { // Make sure we're starting with a clean slate.
VM_Verify verify_op;
VMThread::execute(&verify_op);
}
// We need this to update the java.vm.info property in case any flags used // to initially define it have been changed. This is needed for both CDS // since UseSharedSpaces may be changed after java.vm.info // is initially computed. See Abstract_VM_Version::vm_info_string(). // This update must happen before we initialize the java classes, but // after any initialization logic that might modify the flags.
Arguments::update_vm_info_property(VM_Version::vm_info_string());
JavaThread* THREAD = JavaThread::current(); // For exception macros.
HandleMark hm(THREAD);
// Always call even when there are not JVMTI environments yet, since environments // may be attached late and JVMTI must track phases of VM execution
JvmtiExport::enter_early_start_phase();
// Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
JvmtiExport::post_early_vm_start();
// No more stub generation allowed after that point.
StubCodeDesc::freeze();
// Set flag that basic initialization has completed. Used by exceptions and various // debug stuff, that does not work until all basic classes have been initialized.
set_init_completed();
// record VM initialization completion time #if INCLUDE_MANAGEMENT
Management::record_vm_init_completed(); #endif// INCLUDE_MANAGEMENT
// Signal Dispatcher needs to be started before VMInit event is posted
os::initialize_jdk_signal_support(CHECK_JNI_ERR);
// Start Attach Listener if +StartAttachListener or it can't be started lazily if (!DisableAttachMechanism) {
AttachListener::vm_start(); if (StartAttachListener || AttachListener::init_at_startup()) {
AttachListener::init();
}
}
// Launch -Xrun agents // Must be done in the JVMTI live phase so that for backward compatibility the JDWP // back-end can launch with -Xdebug -Xrunjdwp. if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
create_vm_init_libraries();
}
Chunk::start_chunk_pool_cleaner_task();
// Start the service thread // The service thread enqueues JVMTI deferred events and does various hashtable // and other cleanups. Needs to start before the compilers start posting events.
ServiceThread::initialize();
// Start the monitor deflation thread:
MonitorDeflationThread::initialize();
// initialize compiler(s) #ifdefined(COMPILER1) || COMPILER2_OR_JVMCI #if INCLUDE_JVMCI bool force_JVMCI_intialization = false; if (EnableJVMCI) { // Initialize JVMCI eagerly when it is explicitly requested. // Or when JVMCILibDumpJNIConfig or JVMCIPrintProperties is enabled.
force_JVMCI_intialization = EagerJVMCI || JVMCIPrintProperties || JVMCILibDumpJNIConfig;
if (!force_JVMCI_intialization) { // 8145270: Force initialization of JVMCI runtime otherwise requests for blocking // compilations via JVMCI will not actually block until JVMCI is initialized.
force_JVMCI_intialization = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
}
} #endif
CompileBroker::compilation_init_phase1(CHECK_JNI_ERR); // Postpone completion of compiler initialization to after JVMCI // is initialized to avoid timeouts of blocking compilations. if (JVMCI_ONLY(!force_JVMCI_intialization) NOT_JVMCI(true)) {
CompileBroker::compilation_init_phase2();
} #endif
// Pre-initialize some JSR292 core classes to avoid deadlock during class loading. // It is done after compilers are initialized, because otherwise compilations of // signature polymorphic MH intrinsics can be missed // (see SystemDictionary::find_method_handle_intrinsic).
initialize_jsr292_core_classes(CHECK_JNI_ERR);
// This will initialize the module system. Only java.base classes can be // loaded until phase 2 completes
call_initPhase2(CHECK_JNI_ERR);
JFR_ONLY(Jfr::on_create_vm_2();)
// Always call even when there are not JVMTI environments yet, since environments // may be attached late and JVMTI must track phases of VM execution
JvmtiExport::enter_start_phase();
// Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
JvmtiExport::post_vm_start();
// Final system initialization including security manager and system class loader
call_initPhase3(CHECK_JNI_ERR);
// cache the system and platform class loaders
SystemDictionary::compute_java_loaders(CHECK_JNI_ERR);
#if INCLUDE_CDS // capture the module path info from the ModuleEntryTable
ClassLoader::initialize_module_path(THREAD); if (HAS_PENDING_EXCEPTION) {
java_lang_Throwable::print(PENDING_EXCEPTION, tty);
vm_exit_during_initialization("ClassLoader::initialize_module_path() failed unexpectedly");
} #endif
#if INCLUDE_JVMCI if (force_JVMCI_intialization) {
JVMCI::initialize_compiler(CHECK_JNI_ERR);
CompileBroker::compilation_init_phase2();
} #endif
// Always call even when there are not JVMTI environments yet, since environments // may be attached late and JVMTI must track phases of VM execution
JvmtiExport::enter_live_phase();
// Make perfmemory accessible
PerfMemory::set_accessible(true);
// Notify JVMTI agents that VM initialization is complete - nop if no agents.
JvmtiExport::post_vm_initialized();
if (HAS_PENDING_EXCEPTION) { // management agent fails to start possibly due to // configuration problem and is responsible for printing // stack trace if appropriate. Simply exit VM.
vm_exit(1);
} #endif// INCLUDE_MANAGEMENT
StatSampler::engage(); if (CheckJNICalls) JniPeriodicChecker::engage();
call_postVMInitHook(THREAD); // The Java side of PostVMInitHook.run must deal with all // exceptions and provide means of diagnosis. if (HAS_PENDING_EXCEPTION) {
CLEAR_PENDING_EXCEPTION;
}
{
MutexLocker ml(PeriodicTask_lock); // Make sure the WatcherThread can be started by WatcherThread::start() // or by dynamic enrollment.
WatcherThread::make_startable(); // Start up the WatcherThread if there are any periodic tasks // NOTE: All PeriodicTasks should be registered by now. If they // aren't, late joiners might appear to start slowly (we might // take a while to process their first tick). if (PeriodicTask::num_tasks() > 0) {
WatcherThread::start();
}
}
if (DumpSharedSpaces) {
MetaspaceShared::preload_and_dump();
ShouldNotReachHere();
}
return JNI_OK;
}
// type for the Agent_OnLoad and JVM_OnLoad entry points extern"C" { typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
} // Find a command line agent library and return its entry point for // -agentlib: -agentpath: -Xrun // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array. static OnLoadEntry_t lookup_on_load(AgentLibrary* agent, constchar *on_load_symbols[],
size_t num_symbol_entries) {
OnLoadEntry_t on_load_entry = NULL; void *library = NULL;
// For backwards compatibility with -Xrun // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be // treated like -agentpath: // Must be called before agent libraries are created void Threads::convert_vm_init_libraries_to_agents() {
AgentLibrary* agent;
AgentLibrary* next;
for (agent = Arguments::libraries(); agent != NULL; agent = next) {
next = agent->next(); // cache the next agent now as this agent may get moved off this list
OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
// If there is an JVM_OnLoad function it will get called later, // otherwise see if there is an Agent_OnLoad if (on_load_entry == NULL) {
on_load_entry = lookup_agent_on_load(agent); if (on_load_entry != NULL) { // switch it to the agent list -- so that Agent_OnLoad will be called, // JVM_OnLoad won't be attempted and Agent_OnUnload will
Arguments::convert_library_to_agent(agent);
} else {
vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
}
}
}
}
// Create agents for -agentlib: -agentpath: and converted -Xrun // Invokes Agent_OnLoad // Called very early -- before JavaThreads exist void Threads::create_vm_init_agents() { externstruct JavaVM_ main_vm;
AgentLibrary* agent;
JvmtiExport::enter_onload_phase();
for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) { // CDS dumping does not support native JVMTI agent. // CDS dumping supports Java agent if the AllowArchivingWithJavaAgent diagnostic option is specified. if (Arguments::is_dumping_archive()) { if(!agent->is_instrument_lib()) {
vm_exit_during_cds_dumping("CDS dumping does not support native JVMTI agent, name", agent->name());
} elseif (!AllowArchivingWithJavaAgent) {
vm_exit_during_cds_dumping( "Must enable AllowArchivingWithJavaAgent in order to run Java agent during CDS dumping");
}
}
if (on_load_entry != NULL) { // Invoke the Agent_OnLoad function
jint err = (*on_load_entry)(&main_vm, agent->options(), NULL); if (err != JNI_OK) {
vm_exit_during_initialization("agent library failed to init", agent->name());
}
} else {
vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
}
}
// Invoke the Agent_OnUnload function if (unload_entry != NULL) {
JavaThread* thread = JavaThread::current();
ThreadToNativeFromVM ttn(thread);
HandleMark hm(thread);
(*unload_entry)(&main_vm);
}
}
}
// Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries // Invokes JVM_OnLoad void Threads::create_vm_init_libraries() { externstruct JavaVM_ main_vm;
AgentLibrary* agent;
if (on_load_entry != NULL) { // Invoke the JVM_OnLoad function
JavaThread* thread = JavaThread::current();
ThreadToNativeFromVM ttn(thread);
HandleMark hm(thread);
jint err = (*on_load_entry)(&main_vm, agent->options(), NULL); if (err != JNI_OK) {
vm_exit_during_initialization("-Xrun library failed to init", agent->name());
}
} else {
vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
}
}
}
// Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when // the program falls off the end of main(). Another VM exit path is through // vm_exit() when the program calls System.exit() to return a value or when // there is a serious error in VM. The two shutdown paths are not exactly // the same, but they share Shutdown.shutdown() at Java level and before_exit() // and VM_Exit op at VM level. // // Shutdown sequence: // + Shutdown native memory tracking if it is on // + Wait until we are the last non-daemon thread to execute // <-- every thing is still working at this moment --> // + Call java.lang.Shutdown.shutdown(), which will invoke Java level // shutdown hooks // + Call before_exit(), prepare for VM exit // > run VM level shutdown hooks (they are registered through JVM_OnExit(), // currently the only user of this mechanism is File.deleteOnExit()) // > stop StatSampler, watcher thread, // post thread end and vm death events to JVMTI, // stop signal thread // + Call JavaThread::exit(), it will: // > release JNI handle blocks, remove stack guard pages // > remove this thread from Threads list // <-- no more Java code from this thread after this point --> // + Stop VM thread, it will bring the remaining VM to a safepoint and stop // the compiler threads at safepoint // <-- do not use anything that could get blocked by Safepoint --> // + Disable tracing at JNI/JVM barriers // + Set _vm_exited flag for threads that are still running native code // + Call exit_globals() // > deletes tty // > deletes PerfMemory resources // + Delete this thread // + Return to caller
#ifdef ASSERT
_vm_complete = false; #endif // Wait until we are the last non-daemon thread to execute, or // if we are a daemon then wait until the last non-daemon thread has // executed. bool daemon = java_lang_Thread::is_daemon(thread->threadObj()); int expected = daemon ? 0 : 1;
{
MonitorLocker nu(Threads_lock); while (Threads::number_of_non_daemon_threads() > expected) // This wait should make safepoint checks, wait without a timeout.
nu.wait(0);
}
// Hang forever on exit if we are reporting an error. if (ShowMessageBoxOnError && VMError::is_error_reported()) {
os::infinite_sleep();
}
os::wait_for_keypress_at_exit();
// run Java level shutdown hooks
thread->invoke_shutdown_hooks();
before_exit(thread);
thread->exit(true);
// We are no longer on the main thread list but could still be in a // secondary list where another thread may try to interact with us. // So wait until all such interactions are complete before we bring // the VM to the termination safepoint. Normally this would be done // using thread->smr_delete() below where we delete the thread, but // we can't call that after the termination safepoint is active as // we will deadlock on the Threads_lock. Once all interactions are // complete it is safe to directly delete the thread at any time.
ThreadsSMRSupport::wait_until_not_protected(thread);
// Stop VM thread.
{ // 4945125 The vm thread comes to a safepoint during exit. // GC vm_operations can get caught at the safepoint, and the // heap is unparseable if they are caught. Grab the Heap_lock // to prevent this. The GC vm_operations will not be able to // queue until after the vm thread is dead. After this point, // we'll never emerge out of the safepoint before the VM exits. // Assert that the thread is terminated so that acquiring the // Heap_lock doesn't cause the terminated thread to participate in // the safepoint protocol.
assert(thread->is_terminated(), "must be terminated here");
MutexLocker ml(Heap_lock);
VMThread::wait_for_vm_thread_exit();
assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
VMThread::destroy();
}
// Now, all Java threads are gone except daemon threads. Daemon threads // running Java code or in VM are stopped by the Safepoint. However, // daemon threads executing native code are still running. But they // will be stopped at native=>Java/VM barriers. Note that we can't // simply kill or suspend them, as it is inherently deadlock-prone.
VM_Exit::set_vm_exited();
// Clean up ideal graph printers after the VMThread has started // the final safepoint which will block all the Compiler threads. // Note that this Thread has already logically exited so the // clean_up() function's use of a JavaThreadIteratorWithHandle // would be a problem except set_vm_exited() has remembered the // shutdown thread which is granted a policy exception. #ifdefined(COMPILER2) && !defined(PRODUCT)
IdealGraphPrinter::clean_up(); #endif
notify_vm_shutdown();
// exit_globals() will delete tty
exit_globals();
// Deleting the shutdown thread here is safe. See comment on // wait_until_not_protected() above. delete thread;
jboolean Threads::is_supported_jni_version(jint version) { if (version == JNI_VERSION_1_2) return JNI_TRUE; if (version == JNI_VERSION_1_4) return JNI_TRUE; if (version == JNI_VERSION_1_6) return JNI_TRUE; if (version == JNI_VERSION_1_8) return JNI_TRUE; if (version == JNI_VERSION_9) return JNI_TRUE; if (version == JNI_VERSION_10) return JNI_TRUE; if (version == JNI_VERSION_19) return JNI_TRUE; if (version == JNI_VERSION_20) return JNI_TRUE; return JNI_FALSE;
}
void Threads::add(JavaThread* p, bool force_daemon) { // The threads lock must be owned at this point
assert(Threads_lock->owned_by_self(), "must have threads lock");
BarrierSet::barrier_set()->on_thread_attach(p);
// Once a JavaThread is added to the Threads list, smr_delete() has // to be used to delete it. Otherwise we can just delete it directly.
p->set_on_thread_list();
_number_of_threads++;
oop threadObj = p->threadObj(); bool daemon = true; // Bootstrapping problem: threadObj can be null for initial // JavaThread (or for threads attached via JNI) if (!force_daemon &&
(threadObj == nullptr || !java_lang_Thread::is_daemon(threadObj))) {
_number_of_non_daemon_threads++;
daemon = false;
}
ThreadService::add_thread(p, daemon);
// Maintain fast thread list
ThreadsSMRSupport::add_thread(p);
// Increase the ObjectMonitor ceiling for the new thread.
ObjectSynchronizer::inc_in_use_list_ceiling();
// Possible GC point.
Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
// Make new thread known to active EscapeBarrier
EscapeBarrier::thread_added(p);
}
void Threads::remove(JavaThread* p, bool is_daemon) { // Extra scope needed for Thread_lock, so we can check // that we do not remove thread without safepoint code notice
{ MonitorLocker ml(Threads_lock);
if (ThreadIdTable::is_initialized()) { // This cleanup must be done before the current thread's GC barrier // is detached since we need to touch the threadObj oop.
jlong tid = SharedRuntime::get_java_tid(p);
ThreadIdTable::remove_thread(tid);
}
// BarrierSet state must be destroyed after the last thread transition // before the thread terminates. Thread transitions result in calls to // StackWatermarkSet::on_safepoint(), which performs GC processing, // requiring the GC state to be alive.
BarrierSet::barrier_set()->on_thread_detach(p); if (p->is_exiting()) { // If we got here via JavaThread::exit(), then we remember that the // thread's GC barrier has been detached. We don't do this when we get // here from another path, e.g., cleanup_failed_attach_current_thread().
p->set_terminated(JavaThread::_thread_gc_barrier_detached);
}
assert(ThreadsSMRSupport::get_java_thread_list()->includes(p), "p must be present");
// Maintain fast thread list
ThreadsSMRSupport::remove_thread(p);
_number_of_threads--; if (!is_daemon) {
_number_of_non_daemon_threads--;
// If this is the last non-daemon thread then we need to do // a notify on the Threads_lock so a thread waiting // on destroy_vm will wake up. But that thread could be a daemon // or non-daemon, so we notify for both the 0 and 1 case. if (number_of_non_daemon_threads() <= 1) {
ml.notify_all();
}
}
ThreadService::remove_thread(p, is_daemon);
// Make sure that safepoint code disregard this thread. This is needed since // the thread might mess around with locks after this point. This can cause it // to do callbacks into the safepoint code. However, the safepoint code is not aware // of this thread since it is removed from the queue.
p->set_terminated(JavaThread::_thread_terminated);
// Reduce the ObjectMonitor ceiling for the exiting thread.
ObjectSynchronizer::dec_in_use_list_ceiling();
// Since Events::log uses a lock, we grab it outside the Threads_lock
Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
}
// Operations on the Threads list for GC. These are not explicitly locked, // but the garbage collector must provide a safe context for them to run. // In particular, these things should never be called when the Threads_lock // is held by some other thread. (Note: the Safepoint abstraction also // uses the Threads_lock to guarantee this property. It also makes sure that // all threads gets blocked when exiting or starting).
void Threads::change_thread_claim_token() { if (++_thread_claim_token == 0) { // On overflow of the token counter, there is a risk of future // collisions between a new global token value and a stale token // for a thread, because not all iterations visit all threads. // (Though it's pretty much a theoretical concern for non-trivial // token counter sizes.) To deal with the possibility, reset all // the thread tokens to zero on global token overflow. struct ResetClaims : public ThreadClosure { virtualvoid do_thread(Thread* t) {
t->claim_threads_do(false, 0);
}
} reset_claims;
Threads::threads_do(&reset_claims); // On overflow, update the global token to non-zero, to // avoid the special "never claimed" initial thread value.
_thread_claim_token = 1;
}
}
void Threads::metadata_handles_do(void f(Metadata*)) { // Only walk the Handles in Thread.
ThreadHandlesClosure handles_closure(f);
threads_do(&handles_closure);
}
// Get count Java threads that are waiting to enter the specified monitor.
GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list, int count,
address monitor) {
GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
int i = 0; for (JavaThread* p : *t_list) { if (!p->can_call_java()) continue;
// The first stage of async deflation does not affect any field // used by this comparison so the ObjectMonitor* is usable here.
address pending = (address)p->current_pending_monitor(); if (pending == monitor) { // found a match if (i < count) result->append(p); // save the first count matches
i++;
}
}
return result;
}
JavaThread *Threads::owning_thread_from_monitor_owner(ThreadsList * t_list,
address owner) { // NULL owner means not locked so we can skip the search if (owner == NULL) return NULL;
for (JavaThread* p : *t_list) { // first, see if owner is the address of a Java thread if (owner == (address)p) return p;
}
// Cannot assert on lack of success here since this function may be // used by code that is trying to report useful problem information // like deadlock detection. if (UseHeavyMonitors) return NULL;
// If we didn't find a matching Java thread and we didn't force use of // heavyweight monitors, then the owner is the stack address of the // Lock Word in the owning Java thread's stack. //
JavaThread* the_owner = NULL; for (JavaThread* q : *t_list) { if (q->is_lock_owned(owner)) {
the_owner = q; break;
}
}
// cannot assert on lack of success here; see above comment return the_owner;
}
// Threads::print_on_error() is called by fatal error handler. It's possible // that VM is not at safepoint and/or current thread is inside signal handler. // Don't print stack trace, as the stack may not be walkable. Don't allocate // memory (even in resource area), it might deadlock the error handler. void Threads::print_on_error(outputStream* st, Thread* current, char* buf, int buflen) {
ThreadsSMRSupport::print_info_on(st);
st->cr();
st->print_cr("Threads with active compile tasks:");
print_threads_compiling(st, buf, buflen);
}
void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen, bool short_form) {
ALL_JAVA_THREADS(thread) { if (thread->is_Compiler_thread()) {
CompilerThread* ct = (CompilerThread*) thread;
// Keep task in local variable for NULL check. // ct->_task might be set to NULL by concurring compiler thread // because it completed the compilation. The task is never freed, // though, just returned to a free list.
CompileTask* task = ct->task(); if (task != NULL) {
thread->print_name_on_error(st, buf, buflen);
st->print(" ");
task->print(st, NULL, short_form, true);
}
}
}
}
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